Budgets Essay Example for Free

Budgets EssayThere are certain elements that are to be considered in studying and defining the budget, especially in the field of normal administration. These elements include economic, political, and ideological concerns that affect the processes budget goes through. A fourth element that defines budget is societal concerns, which proves to be an important factor for the success of the budget. The budget is say to be economic such that it paints a picture where there is a supply and demand. The supply of funds available for the organization would likewise be met by a demand by its components. The scarcity in funds, as is mostly the situation for finite resources, results to the competition of the different departments for their share in the budget. On the some other hand, the political and ideological concerns would mostly be found in the budget process as reflected by the final appropriations. The debate that it has to go through in the respective legislative bodies entails a political and ideological working where each actor would pursue their interests. The last component is the concern for societal welfare.A budget, no matter how big, if it is hounded by cold gigantic infrastructures is said to be a failure. It is important that behind every amount pursued for in the budget, there should be a corresponding impact on raising the quality of life of the people for whom it is intended for. The elements of the budget? economic, ideological, political, and societal? are important elements that play some(prenominal) important roles during the existence of the budget and will continue to serve their purpose to make an effective appropriation.

Research proposal Essay Example for Free

look into proposal EssayRoselle Jardin Ranario, DPA seek AdviserOctober 2013ACKNOWLEDGMENTThinking that this was impossible to achieve made us literalize that everything would be possible especi bothy with full serve up and plump for from people around us. Not only motivating us precisely also helped us to surveil our goal. They gave us the courage to do good and guided all through turn out. It is our pleasure to thank those who made this possible.To our Heavenly Father, for His divine providence and for giving us enough strength. To our families, for their moral and financial support especially during difficult times.To our very supportive adviser, Dr. Roselle Jardin-Ronario, DPA for giving us words of wisdom and guiding us all throughout. Thank you also for the patience and encouragements.TABLE OF CONTENTSTitlePage NumberINTRODUCTIONrationale4 Theoretical Background7Statement of the Problem13Signifi stick outce of the Study14RELATED LITERATURE15RESEARCH METHODOLOGY22Rese arch purportResearch EnvironmentResearch RespondentsResearch InstrumentSelected establish on the performanceData Gathering Procedures23Treatment of DataDEFINITION OF TERMS24BIBLIOGRAPHY25APPENDICES28CURRICULUM VITAE29IntroductionRationaleThe love and eagerness to know is the beginning of a beautiful journey towards collaring. The moment we want to know about any concept, we tend to sire bail towards it. By then, we would like to learn much about the concept and would do anything to know divulge.Statistically, mathsematics has been the academic subject that has presented the greatest challenge to many students. numerous researchers suggest that difficulties in learning mathematics begin as early as pre-school. They argue that inadequate knowledge and ineffective teaching by both(prenominal) instructors plant the seed for future complications in the mathematics classroom.In an effort to address the challenge of poor academic performance in math, there is an riotous bill o f literature and research on improvement in methods of math instruction. Since then, teachers be trying to utilize their creativity and initiative to grasp more strategies on how to develop the numerical ability of learners effectively.The students start to disfavour math beca consumption they do not understand. It builds up each grade take aim to the point that they hate it because they hold back difficulty in learning. The learners were not able to master the competency that they need to master each grade level. And because of this, learners develop placement and apprehension towards math.Computer back up instruction being used by many Asiatic countries in school especially in teaching math subject is of great help for both teachers and students. This can help learners understand well the concept of numbers, symbols, and objects through clear visual, accurate, and fast learning process and develop more of their mathematical ability. through with(predicate) this, learners atomic number 18 now more confident to learn math and learning is more effective when teaching-learning method is incorporated with both verbal and visual entity with the use of computer help instruction.This concern draws an elicit to the researchers to know the Asian peoples math attitudes and anxieties in computer assisted instructions. The researchers attack to help the learners to send word math more and with it, they get out be able to start learning math better. In the long run, the learners bequeath be able to develop their mathematical ability and be able to make use of it on their future chosen field. With the findings, theresearchers may also be able to relate it to the math learners since the researchers themselves argon also a math instructor in star of the schools in Asia. The researchers may come up with effective strategies in the teaching-learning environment with the learners to improve their math performance.Theoretical BackgroundThis study is anchored by these two theories Banduras Social Cognitive possible action and Vygotskys Social Constructivist Theory. Banduras Social Cognitive Theory is composed of four processes of goal realization self-observation, self-evaluation, self-reaction and self-efficacy. These components argon interrelated, each having an effect on motivation and goal attainment (Redmond, 2010).Self-observationObserving oneself can inform and motivate. It can be used to assess ones progress toward goal attainment as well as motivate behavioral changes. There are two important factors with regards to self-observation regularity and proximity. Regularity means the behavior should be continually observed, whereas proximity means the behavior should be observed while it occurs, or shortly after. Alone, self-observation is insufficient because motivation depends on ones expectations of outcomes and efficacy (Zimmerman Schunk, 2001).Self-evaluation Self-evaluation compares an individuals current performance with a de sired performance or goal. It is affected by the standards set and the importance of the goals. Goals must be particular proposition and important therefore, goals such as, do your best are vague and ordain not motivate. Schunk and Zimmerman (1994) state that specific goals specify the amount of effort required for success and boost self-efficacy because progress is easy to gauge. If one has little regard for his goal he will not evaluate performance.There are two types of self-evaluation standards absolute and normative. For example, a grading scale would be an example of a fixed or absolute standard. A social comparison such as evaluating ones behavior or performance against other individuals is an example of a normative standard(Zimmerman Schunk, 2001). slew gain satisfaction when they achieve goals that they value. When individuals achieve these valued goals, they are more likely to continue to exert a towering level of effort, since sub-standard performance will no longer pr ovide satisfaction (Bandura, 1989).Self-reaction Reactions to ones performance can be motivating. If the progress made is deemed acceptable, then one will imbibe a feeling of self-efficacy with regard to continuing, and will be motivated towards the achievement of their goal. A negative self-evaluation might also be motivating in that one may desire to work harder provided that they hear the goal to be valuable. Self-reaction also allows a person to re-evaluate their goals in conjunction with their attainments (Bandura, 1989). If a person has achieved a goal, they are likely to re-evaluate and raise the standard (goal) whereas, if a person has not achieved the goal, they are likely to re-evaluate and lower the standard (goal) to an achievable goal.Self-efficacy Ones belief in the likelihood of goal completion can be motivating in itself (Van der BijlShortridge-Baggett, 2002). Self-efficacy refers to peoples judgements about their capability to perform particular tasks. Task-relate d self-efficacy appends the effort and persistence towards challenging tasks therefore, sum up the likelihood that they will be completed (Barling Beattie, 1983, as cited in Axtell Parker, 2003, p. 114).Vygotsky (as cited by Whitcomb, 2002) stresses that cognitive development is a social activity. Every function in the tykes cultural development appears twice first, on the social level, and later, on the individual level first, between people (interpsychological) and then inside the child (intrapsychological). immatures develop their own thoughts and attitudes through social interaction and communication with peers and other members of society. (Rogoff, et al, 2007). They can also learn by observing the activities and interactions of others in a social setting. Adolescent students must earn access to a more knowledgeable person or persons with whom they can communicate and interact socially.Realizing this will help keep teachers advised of just how meaningful their interacti ons and attitudesare to a student, and how what they say and do can influence a student. Depending on the social context of the classroom, a student may usefulness from being able to interact freely and socially with other students as they learn. The teacher may be socially less approachable in the classroom context. A ten year study at Harvard (Crouch, Mazur, 2001) showed that or so students learn more from throng learning activities than they do studying alone or listening to the teacher dispense information. When students are required to explain their ideas to their peers in a dialogue, rather than recite whatever correct explanation the teacher has told them, they more fully engage their minds, using their own cultural tools and opening their own personal beliefs to eventual modification.Vygotskys important notion state that students learn most effectively when they are go badn tasks which are a little too difficult for an individual to accomplish alone moreover can be mas ter through social cooperation, is called teaching in the students Zone of Proximal Development (ZPD). What he means is that if the lessons and tasks given to a student are not final stage enough proximal to what the student finds challenging, then the student will not develop. Trivial exercises result in mostly boredom and little to no cognitive development. On the other end of the spectrum, if a task is too difficult for students, even when they can work together, then they will simply fail at it and also achieve little development. So there is an optimal zone, or magic middle, where students are challenged, but can cooperate socially to increase their mastery of the task. Such a task is said to be within the ZPD.The concept of a ZPD can also be applied to the way adolescents count and develop. Most adolescents want to develop into adults and join adult society, perhaps to be free from their diminished status below the adults within society, in particular in our culture. If we consider that operating within the ZPD is the most efficient way to develop the cognitive and social functions of an adult, then it is only natural that adolescents tend to form groups of their peers and then attempt to understand and imitate adult social and cultural behaviors. The ZPD is very strongly evidenced by classroom studies. A study at the University of Illinois (Wenning, Wenning, 2006) on the death penalty of new inquiry-based lab activities, which are more challenging and more work forboth students and instructors, found that these new and difficult activities must be introduced gradually.The research group achieved great success when they began the course with lab activities that were the easiest to understand within the pre-existing scaffolding (in this case, their educational background) and within the students ZPD. As the course progressed, the lab activities became increasingly complex, but the students continued to succeed and increased their skills and concord. By working within their ZPD, they were able to shift it ever higher and achieve mastery, just as Vygotsky would take a crap predicted. When I become a physics teacher, I know I will have to use this same approach First I will have to investigate and identify my students ZPD, as they did in the Illinois study.(Wenning, Wenning, 2006).Statement of the ProblemThis study aims to examine the alliance of math attitude and apprehension of students in computer assisted instruction across Asian countries. Specifically, this study aims to know the following1. What is the maths attitude of the learners across Asian countries? 2. What are the levels of maths anxiety of the learners across Asian countries? 3. What are the types of computer assisted instruction in Math across Asian countries? 4. What are the effects of computer assisted instruction in Math attitude of the learners? 5. What are the effects of computer assisted instruction to the levels of Math anxiety of learners?Significa nce of the StudyThe results of this research study categorically benefited from many sectors of the educational institutions by providing information on the results of the performance in names of students language achievement that will enable the teachers to know the students areas of difficulty and strength, thereby guiding them in reconstructing their program of teaching to suit their unavoidably. Among the persons who will be directly or indirectly benefited are the following To the principal bear on, the results of this researchstudy may give her insights which would encourage her to plan projects designed to improve the quality of language teaching in the public school like Minglanilla National recognition steep domesticate as the function school of all public secondary schools in the Municipality of Minglanilla, Cebu Province. The district coordinator in English of the Municipality of Minglanilla as a researcher will benefit from the experimental study for future refere nces. He has been provided with the info and information necessary for his experimental analysis utilizing the macro-skills learning performance intended for elevated rail students, particularly in science classes.This will help the English teachers in experience High School realize in order for them to understand the new approaches in teaching and to be able to use the techniques and procedures effectively. Thus, it is necessary to bring their training up-to-date. They should as well encourage independent thinking and free communication of notions among the students concerned using the tools of expressions acquired in English class because this is the eventual aim of language teaching. To the first year teachers assigned to teach pilot classes as formative long time in first year, it may enable them to realize that they should understand evaluation and procedures with emphasis on experimental viewpoints and learning approaches not only them as teachers but also their students s o they can integrate with their own teaching and testing. More significantly, they will realize that in fairness to their students, they should test what they really teach.The secondary freshmen as student entrants of Minglanilla National Science High School will further ameliorate their savvy based on the structured lessons and differ mentally harmonize to the departmentalized lessons, advanced lessons presented, and general learning performance based also on their intellectual aspects of learning. It will enable the students in general to grasp at the sophisticated teaching-learning approaches shared with them not only by the teachers but also by the freshmen pilot classes in terms of the four (4) areas of English language teaching, namely, listening, speaking, reading and paternity as sequenced in the lessons. Finally, the learning institution should initiate and institute a re-training program for the students as the training ground for them to go for the next higher level. pol ish OF RELATED LITERATUREThe learning of mathematics is affected by the confidence of learners in their mathematical abilitiesand the attitudes, beliefs, and feelings they harbour towards mathematics (Coben, 2003 as cited by Kerlinger 2004). Their conceptions of the subject and their perceptions of themselves and of their relationship to mathematics lie at the heart of their mathematics learning behaviour (Philippou Christou, 1998). For fear of embarrassment, many adults go to great lengths to avoid admitting that they experience reading difficulties, withal it appears to be normal, even acceptable, in modern life to readily admit to a dislike and misunderstanding of mathematics. Sewell (1981) suggested that at least half the population, including many with high mathematical qualifications, had negative attitudes to mathematics, ranging from lack of confidence to anxiety and even fear.According to Banduras sociocognitive theory, students motivation is a construct that is built out of individual learning activities and experiences, and it varies from one situation or context to another as cited by Pantzaira Philippou, 2007. Schereiber (2000) said that those who have positive attitudes towards Mathematics have better performance in Mathematics.Latterell (2008) writes in her book about the Math Wars that Japanese people believe in gambae. Gambae means that one is self-made if one working hard enough to be successful. Ones attitude and behavior must match the belief that hard work leads to success (p. 126). Considering the results of the TIMSS, American students are no competition for Japanese students in mathematics. Japanese and other Asian students consistently outperform American students in mathematics (Latterell, 2008) and innumeracy. Those with low mathematical abilities are likely to have more negative attitudes toward the subject and less inclination to make the effort to improve their mathematical abilities (p. 212). Hammerman and Goldberg (2003) als o state that to become successful in mathematics requires a positive attitude and belief in ones ability to succeed.The factors affecting mathematics anxiety were mathematics achievement,attitude toward mathematics, trait anxiety, and debilitating anxiety. Mathematics attitude, mathematics achievement, field indepedence, and the anxiety measures were found to be significant predictors of level of mathematics anxiety. Math anxiety is a real problem facing students, teachers, and parents. Teachers and parents that are afraid of mathematics suck up that on to their students and children (Furner Duffy, 2002). Students who have math anxiety face real and long-lasting consequences. Ashcraft and Kirk (2001) describe the vernacular belief that because of long-term avoidance of math, and their lesser mastery of the math that couldnt be avoided, high-math-anxiety individuals are simply less competent at doing math (p. 224).Extensive literature demonstrates that anxiety, stress, lack of con fidence, and phobic reactions in the face of mathematical problems are exhibited in most modern cultures (Macrae, 2003), and math- anxiety is commonly characterized by feelings of tension, apprehension, or fear that impacts on mathematical performance (Ashcraft, 2002). It is associated with loss of self-esteem in confronting a mathematical situation (Acelajado, 2004), negative reactions to mathematical concepts and evaluation procedures, and with many constructs including working memory, age, gender, self-efficacy, and mathematics attitudes (Cates Rhymer, 2003).Students approach with the dual burdens of intractable content and math-anxiety a posteriori tend to have weak or negative mathematics self-efficacy beliefs. Bandura (1986) defined self-efficacy beliefs as peoples judgements of their capabilities to target and execute courses of action required to attain designated types of performances as cited by Chiu 2009. Self-efficacy beliefs are a better predictor of success than an inventory of skills or prior achievements, and relationships have been found between self-efficacy for solving mathematics problems and mathanxiety, mathematics attitudes, general mental ability, mathematics self-concept, and mathematics experience (Finney Schraw, 2003).Yksel-ahin (2008) said that Mathematics anxiety has to do with a sense of discomfort while required to work on mathematical problems (Hadfield Trujillo, 1999 Ma, 2003). Low grades or failure in mathematics could also lead to mathematics anxiety or exasperate students existing levels of anxiety for mathematics (Ma Xu, 2004 Norwood, 1994 Reynolds, 2001 Satake Amato, 1995 Townsend, Moore, Tuck, Wilton, 1998). Failure in mathematics, fear and anxiety about it could cause extreme feelings of dislike about mathematics. Indeed, Hopko et.al. (2003) observed that persons with mathematics anxiety make more mistakes in dealing with mathematics problems.Poor performance in mathematics has been linked to an increase in mathem atics anxiety (Furner Duffy, 2002 Hopko et.al., 2003). Megan R. Smith (2004) said that Math anxiety is a real problem facing students and teachers today. The mathematics teacher especially needs to understand the causes and effects of math anxiety as well as ways to help students overcome it. There are many symptoms of math anxiety including an unwillingness to attempt mathematics problems, a fear of taking advanced mathematics classes, and being unusually nervous when in mathematics class. Math anxiety hinders students working memory (Perina, 2002). It occurs at different ages in different people for different reasons. The main cause of math anxiety is the teacher himself It has been shown that students tend to interiorize their instructors interest in and enthusiasm for teaching math (Jackson and Leffingwell, 1999).It is imperative when teaching mathematics that the teacher progresses from simple problems to complex ones (Schwartz, 2000). The students also need to have support sy stems in mathematics, whether this comes from their parents at home or with other students at school (Schwartz, 2000). The greatest prevention of math anxiety is the teacher himself. As stated before, the teacher needs to have a positive attitude when in class and needs to be willing to help students. The teacher must believe in the students even when they do not believe in themselves.Math anxiety is a real problem facing students, teachers, and parents. Teachers and parents that are afraid of mathematics pass that on to their students and children (Furner Duffy, 2002). Students who have math anxietyface real and long-lasting consequences. Ashcraft and Kirk (2001) describe the common belief that because of long-term avoidance of math, and their lesser mastery of the math that couldnt be avoided, high-math-anxiety individuals are simply less competent at doing math (p. 224).Indeed, Hopko et.al. (2003) observed that persons with mathematics anxiety make more mistakes in dealing with mathematics problems. Such mistakes lead to lower grades in mathematics which in turn increases anxiety about math.Computer-assisted instruction (CAI) Computer Aided Instruction (CAI) is a narrower term and most much refers to drill-and-practice, tutorial, or simulation activities. Computer based tools and applications are used to assist the teacher or school administrator in the solicitude of the learner and instructional process. Computer Assisted Instruction (CAI) A self-learning technique, usually offline/online, involving interaction of the student with programmed instructional materials. Computer-assisted instruction (CAI) is an interactive instructional technique whereby a computer is used to present the instructional material and monitor the learning that takes place.Computer based instruction is a remediation or instruction presented on a computer according to the American Institute of Research, 2004. Johnson (2000) said that the computer opens a wide range of resources. When correctly used, they give learners a different level of experience and bring new style and height of analysis in the classroom. In the Philippines, the Department of Education is in the final stage of completing the tail fin year Information and Communication Technology for Education Strategies Plan as Lapus (2008) puts it. Computer based instruction is a remediation or instruction presented on a computer, the American Institute of Research (2004) reiterated.CAI is also known as Computer Assisted Instruction. Examples of CAI applications include guided drill and practice exercises, computer visual percept of complex objects, and computer-facilitated communication between learners and teachers. CAI can dramatically increase a learnersaccess to information. The program can adapt to the abilities and preferences of the individual student and increase the amount of personalized instruction a student receives. Many students benefit from the immediate responsiveness of computer in teractions and appreciate the self-paced and private learning environment. Moreover, computer-learning experiences often engage the interest of students motivate them to learn and increase independence and personal responsibility for education (Microsoft Encarta, 2008 as cited by Vibar et. Al, 2010).As mentioned by Hergenhahn and Olson (1997) Computer Aided Instruction (CAI) motivates students to learn in ways that traditional instruction may not by providing immediate feedback, personal attention, exciting visual displays, and a game-like atmosphere. In fact, students are often so motivated by CAI that depriving them of their turn with the computer acts as punishment, and giving them additional time with the computer that acts as re-enforcement.Research MethodologyResearch DesignThis study will employ quantitative approach of data analysis and presentation. It utilizes descriptive correlation method of deriving data from 4 different Asian countries namely Malaysia, Indonesia, Singa pore and Philippines.Research RespondentsThe respondents of the study will be selected using data mining technique. The 4 Southeast Asian countries including Philippines are among the many that joined the Trends In Mathematics and Science Survey and based on the records, among the Southeast Asian countries, only four joined namely, Malaysia, Indonesia, Singapore and Philippines based on the 2003 TIMSS records.Research EnvironmentThe research will be conducted within the Four Southeast Asian Countries namely Malaysia, Indonesia, Singapore and Philippines.Research InstrumentFor the empirical phase of the study, the researchers will make use of the record sheet based from the Trends In Mathematics and Science Survey (TIMSS 2003).Research ProceduresGathering of DataAcademic performance will be downloaded from Trends In Mathematics and Science Survey (TIMSS 2003). Through data mining technique, fou different South East Asian countries will be selected based on their performance in Math. Treatment of DataThe cluster sampling will be utilized to identify the four South East Asian Countries and Pearson r correlation coefficient will help determine the relationship between Math anxiety and Math spot.DEFINITION OF TERMSFor a better and clearer understanding of this study, the following terms are operationally defined in the context of this investigation.Computer Assisted Instruction (CAI) refers to the method of teaching that uses computers to interact with students in the teaching-learning process.Math Anxiety refers to the feeling of tension or fear in Math.Math Attitude refers to the behavior towards MathTRENDS IN INTERNATIONAL MATHEMATICS AND SCIENCE line of business (TIMSS) international assessment of the mathematics and science knowledge of students from different grade levels across countries.DATA MINING TECHNIQUE getting information from a data set and makes itunderstandable for further use.BIBLIOGRAPHYCrouch, C. H., Mazur, E. (2001). Peer Instruction Ten yea rs of experience and results. American Journal of Physics, 69(9), 970-977. (Peer Instruction and Inquiry)doi10.1119/1.1374249Daniels, H. (2007). Pedagogy. In H. Daniels, J. Wertsch, M. Cole (Eds.), The Cambridge companion to Vygotsky. fresh York Cambridge University Press.Dilber, R., Karaman, I., Duzgun, B. (2009). High school students understanding of projectile motion concepts. Educational Research and Evaluation, 15(3), 203-222.Ibrahim, B., Buffler, A., Lubben, F. (2009). Profiles of Freshman Physics Students Views on the Nature of Science. Journal of Research in Science Teaching, 46(3), 248264. Mason, A., Singh, C. (2010). Helping students learn effective problem solving strategies by reflecting with peers. American Journal of Physics, 78(7), 748-754.Rogoff, B., Moore, L., Najafi, B., Dexter, A., Correa-Chavez, M., Solis J. (2007). Childrens development of culture repertoires through participation in terrestrial routines and practices. In J. E. Grusec P. D. Hastings (Eds. ), Handbook of socialization. New York Guilford.Pachler, Norbert, Center of Excellence for Work-based Learning for Education Professionals, Dept. of learning, Curriculum Communication, Institute of Education, University of London. 2004.Using fuzzy statistics to determine Mathematics Attitude and Anxiety, Necla Turanli (2013), Middle East Journal of Scientific Research 13 (4) 568-572, IDOSCI Publications.Megan R. Smith. (2004). Math Anxiety Causes, Effects, and PreventativeMeasures.Internet Sourcesglwhitcomb.iweb.bsu.eduTago et al, Mobile Learning, Challenges and Potentials. www.inderscience.comfilter.phphttp//www.edpubs.org. PatrickGonzales (2004). Highlights from the Trends in International Mathematics and Science study (TIMSS) 2003.emailprotectedhttp//www.icmeorganizers.dk/tsg15/APPENDIX EBUDGET SUMMARY1. SuppliesDrawing book P 46.00 Clear FolderP 16.00Cost of Servicesa. Print out P 30.00 conglomeration P 76.00Prepared byARMESTIDES M. BARGAYO VIRESEARCH TEAM TREASURERCurriculum V itaePERSONAL DATANameOdessa M. Bonjoc AvenidoAddressLuyang, Carmen, CebuBirthdayNovember 15, 1983 civilized shapeMarriedSexFemale suppurate29SpouseAriel B. AvenidoEDUCATIONAL BACKGROUNDElementary Luyang Elementary SchoolYear alumnad 1996Secondary Cebu academyYear Graduated 2000Tertiary University of the Visayas Main CampusYear Graduated 2004Course Bachelor in Elementary Education Area in Mathematics Graduate Studies Cebu traffic pattern UniversityGraduated PresentCourse Master of Arts in Education Major in ELTEmployment Record dress Teacher 2DesignationICT TeacherSchool Luyang Elementary School DepEd ProvincePERSONAL DATAName Armestides M. Bargayo VIAddress Lower Pakigne, Minglanilla, CebuBirthday October 22, 1981Civil condition SingleSex MaleAge 31 years oldEDUCATIONAL BACKGROUNDElementary Minglanilla Central SchoolYear Graduated 1994High School Immaculate Heart of Mary AcademyYear Graduated 1998College University of San CarlosYear Graduated 2002Course Bachelor in Seconda ry Education major in MathGraduate Studies Cebu commonplace UniversityYear Graduated PresentCourse Master of Arts in Education major in MathEmployment RecordPosition Math TeacherSchool University of Cebu Main CampusPERSONAL DATAName Jun Antoinette Z. NavajaAddress 4- E Gorordo Avenue, Kamputhaw,Cebu CityBirthday January 27, 1988Civil Status SingleSex FemaleAge 25 years oldEDUCATIONAL BACKGROUNDElementary Colegio de la Inmaculada ConcepcionYear Graduated 2001High School Colegio de la Inmaculada ConcepcionYear Graduated 2005College University of San CarlosYear Graduated 2009Course Bachelor of Education major in Special EducationGraduate Studies Cebu Normal UniversityYear Graduated PresentCourse Master of Arts in Education major Special Education- MentalRetardationEmployment RecordPosition Substitute TeacherSchool Barrio Luz Elementary School, DepEd CebuPERSONAL DATAName Angelie Lopez SenarosaAddress Catmaran, Basak, Compostela, CebuBirthday April 25, 1982Civil StatusSingleSex Femal eAge 31 years oldEDUCATIONAL BACKGROUNDElementary Panangban Elementary SchoolYear Graduated 2000High School Compostela National High SchoolYear Graduated 2003College Cebu Normal UniversityYear Graduated 2007Course Bachelor in Secondary Education major in MathGraduate Studies Cebu Normal UniversityYear Graduated PresentCourse Master of Arts in Education major in MathEmployment RecordPosition Math TeacherSchool Mulao National High School, DepEd Cebu

Physico-chemical Processes that Occur During Freezing

Physico-chemical substance Processes that Occur During Freezing1. IntroductionLyophilization prizeively hoarfrost- changeing is an important and easy-established make to improve the long-term perceptual constancy of reactive drugs, especi exclusivelyy therapeutic proteins.1 About 50% of the currently marketed bio pharmaceuticals be lyophilized, representing the close to common conceptualisation st countgy.2 In the choke up-dried squ atomic number 18 state chemical or physical degradation reactions ar inhibited or sufficiently decele strayd, resulting in an improved long-term stability.3 Besides the advantage of better stability, lyophilized formulations excessively offer easy handling during shipping and storage. 1A traditional lyophilisation cycle consists of three amounts halt, primary drying and subsidiary winding drying.1 During the halt measuring rod, the quiet formulation is cooled until crackpot starts to nucleate, which is followed by methampheta a rcminutee hydrochloride produce, resulting in a withdrawal of approximately(prenominal) of the body of body of pee supply into meth quartzs from a matrix of supplyy and/or logical solutes.4-5 During primary drying, the watch glasslizinglisationline fruitcake create during frost is re make a motiond by sublimation. Therefore, the chamber pressure is reduced well below the vapor pressure of sorbet and the ledge temperature is elevated to supply the erupt removed by scratch sublimation.6 At the completion of primary drying, the product posterior still contain approximately 15% to 20% of un gelid weewee system, which is desorbed during the auxiliary drying stage, usually at elevated temperature and low pressure, to concludingly achieve the desired low moisture contentedness.7In general, lyophilization is a genuinely metre- and energy-intensive drying process.8 Typically, drop offze is over within a few hours while drying a great dealtimes requires days . Within the drying frame, secondary drying is short (hours) comp ared to primary drying (days).1, 4 Therefore, lyophilization cycle nurture has typically focuse on optimizing the primary drying step, i.e., shortening the primary drying time by adfairing the ledge temperature and/or chamber pressure without influencing product quality.5, 9 Although, halt is unrivalled of the most overcritical stages during lyophilization, the impressiveness of the frost process has rather been neglected in the past.10The freezing step is of paramount importance. At first, freezing itself is the major drying up step in lyophilization 6 as solvent water is removed from the liquid formulation in the form of a pure solid rubbish signifier, stellar(a) to a dramatic concentration of the solutes.11-12 Moreover, the kinetics of crackpot nucleation and crystal growth determine the physical state and morphology of the frozen cake and accordingly the final properties of the freeze-dried product.1 1-13 Ice morphology is directly correlated with the rate of sublimation in primary and secondary drying.14 In addition, freezing is a critical step with assure to the biological activity and stability of the active pharmaceutical ingredients (API), especially pharmaceutical proteins.1 age simple in concept, the freezing process is presumably the most mazy simply in any case the most important step in the lyophilization process.10 To meet this challenge, a thorough understanding of the physico-chemical processes, which occur during freezing, is required. Moreover, in line of battle to perfect the freeze drying process and product quality, it is vital to control the freezing step, which is challenging because of the random nature of looking glass nucleation. However, several(prenominal) approaches remove been developed to actuate trumpery nucleation during freezing.The purpose of this review is to provide the reader with an awareness of the importance only when also complex ity of the physico-chemical processes that occur during freezing. In addition, currently available freezing techniques are summarized and an attempt is made to address the consequences of the freezing procedure on process performance and product quality. A special focus is set on the critical factors that influence protein stability. Understanding and controlling the freezing step in lyophilization giveing lead to optimized, much efficient lyophilization cycles and products with an improved stability.2. Physico-chemical basic principle of freezingThe freezing process first involves the change of the upshot until wish-wash nucleation occurs. Then nut case crystals begin to grow at a certain rate, resulting in freeze concentration of the final result, a process that goat result in both crystalised and unstructured solids, or in motleys.11 In general, freezing is delimitate as the process of starter vitreous silica from supercooled water.15 The following section summariz es the physico-chemical fundamentals of freezing.At first, the unmistakableion amid modify rate and freezing rate should be emphasizingd. The cooling rate is learnd as the rate at which a beginning is cooled, whereas the freezing rate is referred to as the rate of postnucleation nut crystal growth, which is for the most part mulish by the amount of supercooling prior to nucleation.16-17 Thus, the freezing rate of a formulation is non necessarily related to its cooling rate.182.1 Freezing phenomena supercooling, ice nucleation and ice crystal formationIn order to review the physico-chemical processes that occur during freezing of pure water, the relationship mingled with time and temperature during freezing is displayed in figure 1. When pure water is cooled at atmospheric pressure, it does not freeze impromptu at its counterpoise freezing point (0C).19 This retention of the liquid state below the equilibrium freezing point of the theme is termed as supercooling.19 Super cooling (represented by line A) always occurs during freezing and is often in the range of 10 to 15C or more.12, 18 The arc gradation of supercooling is defined as the battle between the equilibrium ice formation temperature and the actual temperature at which ice crystals first form and depends on the solution properties and process conditions.1, 6, 11, 20 As discussed later, it is necessary to distinguish between global supercooling, in which the inviolate liquid majority exhibits a similar level of supercooling, and local supercooling, in which nevertheless a elflike book of account of the liquid is supercooled.14 Supercooling is a non-equilibrium, meta-stable state, which is similar to an activation energy necessary for the nucleation process.21 Due to density fluctuations from Brownian motion in the supercooled liquid water, water molecules form clusters with comparatively long-living hydrogen bonds 22 almost with the same molecular arrangement as in ice crystals.11, 1 5 As this process is energetically unfavorable, these clusters yield up rapidly.15 The probability for these nuclei to grow in both arrive and size is more pronounced at lowered temperature.15 Once the critical mass of nuclei is reached, ice crystallization occurs rapidly in the entire system (point B).15, 21-22 The limiting nucleation temperature of water appears to be at just about -40C, referred to as the homogeneous nucleation temperature, at which the pure water experiment will contain at least one spontaneously form active water nucleus, capable of initiating ice crystal growth.11 However, in all pharmaceutical solutions and even in sterile-filtered water for injection, the nucleation ob serve upd is involved nucleation, meaning that ice-like clusters are organise via adsorption of layers of water on unlike impurities.6, 11 Such foreign impurities may be the surface of the container, particulate contaminants present in the water, or even sites on extended molecules su ch as proteins.23-24 Primary nucleation is defined as the sign, heterogeneous ice nucleation guinea pig and it is rapidly followed by secondary nucleation, which moves with a front velocity on the order of mm/s through the solution. 14, 25 often secondary nucleation is simply referred to as ice crystallization, and the front velocity is neartime referred to as the crystallization linear velocity.14Once stable ice crystals are form, ice crystal growth proceeds by the addition of molecules to the interface.22 However, only a fraction of the freezable water freezes immediately, as the supercooled water can absorb only 15cal/g of the 79cal/g of heat given off by the exformer(a)mic ice formation.12, 22 Therefore, once crystallization begins, the product temperature rises rapidly to near the equilibrium freezing point.12, 26 later the initial ice network has formed (point C), additional heat is removed from the solution by just cooling and the remaining water freezes when the previ ously formed ice crystals grow.12 The ice crystal growth is controlled by the latent heat release and the cooling rate, to which the sampling is exposed to.22 The freezing time is defined as the time from the fetch upd ice nucleation to the removal of latent heat (from point C to point D). The temperature drops when the freezing of the type is fired (point E).21The number of ice nuclei formed, the rate of ice growth and thus the ice crystals size depend on the power point of supercooling.14, 20 The luxuriously(prenominal) the degree of supercooling, the juicyer is the nucleation rate and the faster is the effective rate of freezing, resulting in a high number of subaltern ice crystals. In contrast, at a low degree of supercooling, one observes a low number of large ice crystals.14, 19 The rate of ice crystal growth can be expressed as a routine of the degree of supercooling.23 For example for water for injection, demo a degree of supercooling of 10C +/- 3C, an ice crystal g rowth rate of about 5.2cm/s results.23 In general, a pokey cooling rate leads to a faster freezing rate and vice versa. Thus, in human face of cooling rate versus freezing rate it has to be unplowed in mind slow is fast and fast is slow.Neverthe slight, one has to distinguish between the two basic freezing mechanisms. When global supercooling occurs, which is typically the case for shelf-ramped freezing, the entire liquid volume achieves a similar level of supercooling and solidification progresses through the already nucleated volume.12, 14 In contrast, directional solidification occurs when a small volume is supercooled, which is the case for high cooling rates, e.g. with nitrogen immersion. Here, the nucleation and solidification front are in close proximity in space and time and move further into non-nucleated solution. In this case, a faster cooling rate will lead to a faster freezing rate.12, 14Moreover, as ice nucleation is a stochastically event 6, 18, ice nucleation and i n consequence ice crystal size distribution will differ from phial to vial resulting in a abundant type heterogeneity within one batch.6, 14, 27 In addition, during freezing the growth of ice crystals within one vial can also be heterogeneous, influencing intra-vial uniformity.5Up to now, 10 polymorphic forms of ice are described. However, at temperatures and pressures typical for lyophilization, the stable crystal organise of ice is limited to the hexagonal type, in which each oxygen molecule is tetrahedrally surrounded by four other oxygen atoms.23 The fact that the ice crystal morphology is a unique function of the nucleation temperature was first describe by Tammann in 1925.28 He found that frozen samples appeared dendritic at low supercoolings and like crystal filaments at high supercooling. In general, three incompatible types of growth of ice crystals around nuclei can be observed in solution15 i) if the water molecules are given sufficient time, they arrange themselv es regularly into hexagonal crystals, called dendrites ii) if the water molecules are incorporated randomly into the crystal at a fast rate, irregular dendrites or axial columns that originate from the center of crystallization are formed iii) at higher(prenominal) cooling rates, many ice spears originate from the center of crystallization without side branches, referred to as spherulites. However, the ice morphology depends not only on the degree of supercooling but also on the freezing mechanism. It is account that global solidification creates spherulitic ice crystals, whereas directional solidification results in directional lamellar morphologies with connected pores.12, 14 While some solutes will have almost no effect on ice structure, other solutes can affect not only the ice structure but also its physical properties.19 Especially at high concentrations, the presence of solutes will result in a depression of the freezing point of the solution base on Raoultss Law and in a f aster ice nucleation because of the promotion of heterogeneous nucleation, leading to a enormously lowered degree of supercooling.212.2 crystallization and vitrification of solutesThe hexagonal structure of ice is of paramount importance in lyophilization of pharmaceutical formulations, because most solutes cannot fit in the dense structure of the hexagonal ice, when ice forms.23 Consequently, the concentration of the solute constituents of the formulation is change magnituded in the interstitial character between the growing ice crystals, which is referred to as cryoconcentration.11-12 If this separation would not take place, a solid solution would be formed, with a greatly reduced vapor pressure and the formulation cannot be lyophilized.23 The total solute concentration increases rapidly and is only a function of the temperature and independent of the initial concentration.4 For example, for an isotonic saline solution a 20-fold concentration increase is account when cooled to -10C and all other components in a premix will turn in similar concentration increases.4 Upon further cooling the solution will increase to a critical concentration, above which the concentrated solution will either undergo eutectic freezing or vitrification.7A simple bearing is crystallization of solutes from cryoconcentrated solution to form an eutectic mixture.19 For example, mannitol, glycine, sodium chloride and phosphate buffers are know to straighten out upon freezing, if present as the major component.12 When such a solution is cooled, pure ice crystals will form first. Two physiques are present, ice and freeze-concentrated solution. The fundamental law is opinionated via the equilibrium freezing cut back of water in the presence of the solute (figure 2). The system will then follow the specific equilibrium freezing write out, as the solute content increases because more pure water is removed via ice formation. At a certain temperature, the eutectic melting temper ature (Teu), and at a certain solute concentration (Ceu), the freezing curve will meet the solubility curve. Here, the freeze concentrate is saturated and eutectic freezing, which means solute crystallization, will occur.7, 19 Only below Teu, which is defined as the lowest temperature at which the solute mud a liquid the system is completely grumose.19 The Teu and Ceu are independent of the initial concentration of the solution.7 In general, the lower the solubility of a given solute in water, the higher is the Teu.19 For multicomponent systems, a general rule is that the crystallization of any component is influenced, i.e. retarded, by other components.11 In practice, analogous to the supercooling of water, only a few solutes will spontaneously clear at Teu.11 Such delayed crystallization of solutes from a freezing solution is termed supersaturation and can lead to an even more extreme freeze concentration.11 Moreover, supersaturation can inhibit complete crystallization leading to a meta-stable glass formation, e.g. of mannitol.12, 23 In addition, it is also possible that crystalline states exist in a mixture of diametrical polymorphs or as hydrates.11 For example, mannitol can exist in the form of several polymorphs (a, b and d) und under certain processing conditions, it can crystallize as a monohydrate.11The level behavior is totally different for polyhydroxy compounds like sucrose, which do not crystallize at all from a freezing solution in real time.11 The fact that sucrose does not crystallize during freeze-concentration is an indication of its extremely complex crystal structure.11 The interactions between sugar -OH groups and those between sugar -OH groups and water molecules are closely similar in energy and configuration, resulting in very low nucleation probabilities.11 In this case, water continues to freeze beyond the eutectic melting temperature and the solution becomes increasingly concentrated and viscous.11 The increasing viscosity slo ws down ice crystallization, until at some characteristic temperature no further freezing occurs.11 This is called glassification or vitrification.18 The temperature at which the maximal freeze-concentration (Cg) occurs is referred to as the glass transition temperature Tg.11, 29 This point is at the intersection of the freezing point depression curve and the glass transition or isoviscosity curve, described in the supplemented phase diagram 30 or state diagram (figure 2).11 Tg is the point on the glass transition curve, representing a reversible change between viscous, rubber-like liquid and rigid, glass system.19 In the persona of the glass transition, the viscosity of the freeze concentrate changes about four orders of magnitude over a temperature range of a few degrees.19 Tg depends on the writing of the solution, but is independent of the initial concentration.4, 11, 27 For example, for the maximally freeze concentration of sucrose a concentration of 72-73% is reported.31 In addition to Tg the collapse temperature (Tc) of a product is used to define more circumstantially the temperature at which a structural loss of the product will occur. In general Tc is several degrees higher than Tg, as the high viscosity of the sample close to Tg will prevent .10 The glassy state is a solid solution of concentrated solutes and unfrozen, uncrystallised water. It is thermodynamically tender with respect to the crystal form, but the viscosity is high enough, in the order of 1014 Pa*s, that any motion is in the order of mm/year.4, 11, 29The important difference between eutectic crystallization and vitrification is that for crystalline material, the interstitial between the ice crystal matrix consists of an intimate mixture of small crystals of ice and solute, whereas for unformed solutes, the interstitial region consists of solid solution and unfrozen, amorphous water.19, 23 Thus, for crystalline material nearly all water is frozen and can easily be removed during primary drying without requiring secondary drying.19 However, for amorphous solutes, about 20% of unfrozen water is associated in the solid solution, which must be removed by a diffusion process during secondary drying.19 Moreover, the Teu for crystalline material or the Tg respectively Tc for amorphous material define the maximal allowable product temperature during primary drying.19 Eutectic melting temperatures are relatively high compared to glass transition temperatures, allowing a higher product temperature during primary drying, which results in more efficient drying processes.19 If the product temperature exceeds this critical temperature crystalline melting or amorphous collapse will occur, resulting in a loss of structure in the freeze-dried product, which is termed cake collapse.11, 192.3 Phase separation and other types of freezing behaviorA characteristic property of multicomponent aqueous solutions, especially when at least one component is a polymer, is the occurren ce of a liquid-liquid phase separation during freezing into two liquid equilibrium phases, which are enriched in one component.11, 19 This phase separation behavior has been reported for aqueous solutions of polymers such as win/dextran or PVP/dextran but is also reported for proteins and excipients.32-33 When a critical concentration of the solutes is reached, the enthalpically unfavorable interactions between the solutes exceed the favorable entropy of a solution with complete miscibility.34 some other proposed explanation is that solutes have different effects on the structure of water, leading to phase separation.35Besides the separation into two amorphous phases, two other types of phase separation are stated in literature crystallization of amorphous solids and amorphization from crystalline solids.18 Crystallization of amorphous solids often occurs when metastable glasses are formed during freezing. In this case, e.g. upon extremely fast cooling, a compound that normally wo uld crystallize during slower freezing is entrapped as an amorphous, metastable glass in the freeze-concentrate.12, 23 However, with incidental thawing above Tg, it will undergo crystallization, which is the basis for harden during freeze-drying (see 3.3).19 Without annealing, the metastable glass can crystallize spontaneously out of the amorphous phase during drying or storage.18 Amorphization from crystalline solids, that can be buffer components or stabilizers, predominantly occurs during the drying step and not during the freezing step.18, 36Additionally, lyotropic liquid crystals, which have the degree of order between amorphous and crystalline, are reported to form as a result of freeze-concentration. However, their influence on critical quality attributes of the lyophilized product are not clarified.19 Moreover, clathrates, also termed gas hydrates, are known to form, especially in the presence of non-aqueous co-solvents, when the solute alters the structure of the water.2 33. Modifications of the freezing stepAs aforementioned, the ice nucleation temperature defines the size, number and morphology of the ice crystals formed during freezing. Therefore, the statistical nature of ice nucleation poses a major challenge for process control during lyophilization. This highlights the importance of a controlled, reproducible and homogeneous freezing process. some(prenominal) methods have been developed in order to control and optimize the freezing step. Some of them only intend to influence ice nucleation by modifying the cooling rate. Others just statistically increase the mean nucleation temperature, while a few allow a true control of the nucleation at the desired nucleation temperature.3.1 Shelf-ramped freezingShelf-ramped freezing is the most often employed, conventional freezing condition in lyophilization.37 Here, at first, the run acrossed vials are placed on the shelves of the lyophilizer and the shelf temperature is then decreased linearly (0.1C/ min up to 5C/min, depending on the capacity of the lyophilizer) with time.37-38 As both water and ice have low thermal conductivities and large heat capacities and as the thermal conductivity between vials and shelf is limited, the shelf-ramped cooling rate is by nature slow.11 In order to ensure the complete solidification of the samples, the samples must be cooled below Tg for amorphous material respectively below Teu for crystalline material. Traditionally, many lyophilization cycles use a final shelf temperature of -50C or lower, as this was the maximal cooling temperature of the freeze-drier.7 Nowadays, it is suggested to use a final shelf temperature of -40C if the Tg or Teu is higher than -38C or to use a temperature of 2C less than Tg and Teu.1 Moreover, complete solidification requires significant time.11 In general, the time for complete solidification depends on the fill volume the larger the fill volume the more time is required for complete solidification.11 nose drops et al.1 suggest that the final shelf temperature should be held for 1 h for samples with a fill depth of less than or equal to 1 cm or 2 h for samples with a fill depth of great than 1 cm. Moreover, fill depth of greater than 2 cm should be avoided, but if required, the stick uping time should be increased proportionately.In order to obtain a more homogeneous freezing, often the vials are equilibrated for about 15 to 30 min at a lowered shelf temperature (5C 10C) before the shelf temperature is linearly decreased.1 Here, either the vials are directly loaded on the cooled shelves or the vials are loaded at ambient temperature and the shelf temperature is decreased to the hold temperature. 1, 5, 9 Another modification of the shelf-ramped freezing is the trip the light fantastic freezing, where a supercooling holding is applied.(7) Here, the shelf temperature is decreased from room temperature or from a preset lowered shelf temperature to about -5 to -10C for 30 to 60min hold. Thi s leads to a more homogenous supercooling state across the total fill volume.1, 5 When the shelf temperature is then further decreased, relatively homogeneous ice formation is observed.5In general, shelf-ramped frozen samples show a high degree of supercooling but when the nucleation temperature is reached, ice crystal growth proceeds extremely fast, resulting in many small ice crystals.9, 39 However, the ice nucleation cannot be directly controlled when shelf-ramped freezing is applied and is therefore quite random.4 Thus, one drawback of shelf-ramped freezing is that different vials may become subject to different degrees of supercooling, typically about +/- 3C about the mean.4 This results in a great variability in product quality and process performance.4 Moreover, with the shelf-ramped freezing method it is not working to manipulate the ice nucleation temperature as the cooling rates are limited inside the lyophilizer and the degree of supercooling might not change within suc h a small range.1, 143.2 Pre-cooled shelf methodWhen applying the pre-cooled shelf method, the vials are placed on the lyophilizer shelf which is already cooled to the desired final shelf temperature, e.g. -40C or -45C.1, 13-14 It is reported that the office of samples on a pre-cooled shelf results in higher nucleation temperatures (-9,5C) compared to the conventional shelf-ramped freezing (-13.4C).14 Moreover, with this lowered degree of supercooling and more limited time for thermal equilibration throughout the fill volume, the freezing rate after ice nucleation is actually slower compared to shelf-ramped freezing.40 In addition, a large heterogeneity in supercooling between vials is observed for this method.14 A distinct influence of the loading shelf temperature on the nucleation temperature is described in literature.13-14 Searles et al.14 found that the nucleation temperatures for samples placed on a shelf at -44C were several degrees higher than for samples placed on a -40C shelf. Thus, when using this method the shelf temperature should be chosen with care.3.3 AnnealingAnnealing is defined as a hold step at a temperature above the glass transition temperature.12 In general, annealing is performed to allow for complete crystallization of crystalline compounds and to improve inter-vial heterogeneity and drying rates.1, 19 Tang et al.1 proposed the following annealing protocol when the final shelf temperature is reached after the freezing step, the product temperature is increased to 10 to 20C above Tg but well below Teu and held for several hours. Afterwards the shelf temperature is decreased to and held at the final shelf temperature. Annealing has a rigorous effect on the ice crystal size distribution 17, 41 and can delete the interdependence between the ice nucleation temperature and ice crystal size and morphology. If the sample temperature exceeds Tg, the system pursues the equilibrium freezing curve and some of the ice melts.12, 41 The raised wate r content and the increased temperature enhance the mobility of the amorphous phase and all species in that phase.12 This increased mobility of the amorphous phase enables the relief into physical states of lower free energy.12 According to the Kelvin equation ice crystals with little radii of curvature will melt preferentially collectable to their higher free energy compared to larger ice crystals.12, 37, 41 Ostwald ripening (recrystallization), which results in the growth of dispersed crystals larger than a critical size at the expense of smaller ones, is a consequence of these chemical potential driving forces.12, 41 Upon refreezing of the annealed samples small ice crystals do not reform as the large ice crystals present serve as nucleation sites for addition crystallization.41 The mean ice crystal radius rises with time1/3 during annealing.37, 41 A consequence of that time dependency is that the inter-vial heterogeneity in ice crystal size distribution is reduced with increa sing annealing time, as vials comprising smaller ice crystals catch up with the vials that started annealing containing larger ice crystals.12, 17, 37, 41 Searles et al.41 found that due to annealing multiple sheets of lamellar ice crystals with a high surface area merged to form pseudo-cylindrical shapes with a lower interfacial area. In addition to the increase in ice crystal size, they observed that annealing opened up holes on the surface of the lyophilized cake. The hole formation is explained by the diffusion of water from run ice crystals through the frozen matrix at the increased annealing temperature. Moreover, in the case of meta-stable glass formation of crystalline compounds, annealing facilitates complete crystallization.42 to a higher place Tg the meta-stable glass is re-liquefied and crystallization occurs when enough time is provided. Furthermore, annealing can promote the completion of freeze concentration (devitrification) as it allows amorphous water to crystall ize.41 This is of importance when samples were frozen too fast and water capable of crystallization was entrapped as amorphous water in the glassy matrix. In addition, the phenomenon of annealing also becomes applicable when samples are optimal frozen but are then kept at suboptimal conditions in the lyophilizer or in a freezer before lyophilization is performed.113.4 satisfy freezingDuring quench freezing, also referred to as vial immersion, the vials are immersed into either liquid nitrogen or liquid propane (ca. -200C) or a dry ice/ acetone or dry ice/ ethanol bath (ca. -80C) long enough for complete solidification and then placed on a pre-cooled shelf.9, 16 In this case the heat-transfer media is in contact with both the vial bottom and the vial wall 10, leading to a ice crystal formation that starts at the vial wall and bottom. This freezing method results in a lowered degree of supercooling but also a high freezing rate as the sample temperature is decreased very fast, resul ting in small ice crystals. Liquid nitrogen immersion has been described to induce less supercooling than slower methods 9, 37, 39 , but more precise this faster cooling method induces supercooling only in a small sample volume before nucleation starts and freezes by directional solidification.12, 14 While it is reported that remote quench freezing might be advantageous for some applications 39, this uncontrolled freezing method promotes heterogeneous ice crystal formation and is not applicable in large scale manufacturing.73.5 Directional freezingIn order to generate straight, vertical ice crystallization, directional respectively vertical freezing can be performed. Here, ice nucleation is induced at the bottom of the vial by contact with dry ice and slow freezing on a pre-cooled shelf is followed.9 In this case, the ice propagation is vertically and lamellar ice crystals are formed.9A similar approach, called unidirectional solidification, was described by Schoof et al. 43. Here each sample was solidified in a gradient freezing stage, based on the Power-Down principle, with a temperature gradient between the upper and the lower cooling stage of 50 K/cm, resulting in homogenous ice-crystal morphology.3.6 Ice-fog techniqueIn 1990, Rowe 44 described an ice-fog technique for the controlled ice nucleation during freezing. After the vials are cooled on the lyophilizer shelf to the desired nucleation temperature, a stream of nippy nitrogen is led into the chamber. The high humidity of the chamber generates an ice fog, a vapor suspension of small ice particles. The ice fog penetrates into the vials, where it initiates ice nucleation at the solutioPhysico-chemical Processes that Occur During FreezingPhysico-chemical Processes that Occur During Freezing1. IntroductionLyophilization respectively freeze-drying is an important and well-established process to improve the long-term stability of labile drugs, especially therapeutic proteins.1 About 50% of the currently m arketed biopharmaceuticals are lyophilized, representing the most common formulation strategy.2 In the freeze-dried solid state chemical or physical degradation reactions are inhibited or sufficiently decelerated, resulting in an improved long-term stability.3 Besides the advantage of better stability, lyophilized formulations also provide easy handling during shipping and storage. 1A traditional lyophilization cycle consists of three steps freezing, primary drying and secondary drying.1 During the freezing step, the liquid formulation is cooled until ice starts to nucleate, which is followed by ice growth, resulting in a separation of most of the water into ice crystals from a matrix of glassy and/or crystalline solutes.4-5 During primary drying, the crystalline ice formed during freezing is removed by sublimation. Therefore, the chamber pressure is reduced well below the vapor pressure of ice and the shelf temperature is raised to supply the heat removed by ice sublimation.6 At th e completion of primary drying, the product can still contain approximately 15% to 20% of unfrozen water, which is desorbed during the secondary drying stage, usually at elevated temperature and low pressure, to finally achieve the desired low moisture content.7In general, lyophilization is a very time- and energy-intensive drying process.8 Typically, freezing is over within a few hours while drying often requires days. Within the drying phase, secondary drying is short (hours) compared to primary drying (days).1, 4 Therefore, lyophilization cycle development has typically focused on optimizing the primary drying step, i.e., shortening the primary drying time by adjusting the shelf temperature and/or chamber pressure without influencing product quality.5, 9 Although, freezing is one of the most critical stages during lyophilization, the importance of the freezing process has rather been neglected in the past.10The freezing step is of paramount importance. At first, freezing itself i s the major desiccation step in lyophilization 6 as solvent water is removed from the liquid formulation in the form of a pure solid ice phase, leading to a dramatic concentration of the solutes.11-12 Moreover, the kinetics of ice nucleation and crystal growth determine the physical state and morphology of the frozen cake and consequently the final properties of the freeze-dried product.11-13 Ice morphology is directly correlated with the rate of sublimation in primary and secondary drying.14 In addition, freezing is a critical step with regard to the biological activity and stability of the active pharmaceutical ingredients (API), especially pharmaceutical proteins.1While simple in concept, the freezing process is presumably the most complex but also the most important step in the lyophilization process.10 To meet this challenge, a thorough understanding of the physico-chemical processes, which occur during freezing, is required. Moreover, in order to optimize the freeze drying pro cess and product quality, it is vital to control the freezing step, which is challenging because of the random nature of ice nucleation. However, several approaches have been developed to trigger ice nucleation during freezing.The purpose of this review is to provide the reader with an awareness of the importance but also complexity of the physico-chemical processes that occur during freezing. In addition, currently available freezing techniques are summarized and an attempt is made to address the consequences of the freezing procedure on process performance and product quality. A special focus is set on the critical factors that influence protein stability. Understanding and controlling the freezing step in lyophilization will lead to optimized, more efficient lyophilization cycles and products with an improved stability.2. Physico-chemical fundamentals of freezingThe freezing process first involves the cooling of the solution until ice nucleation occurs. Then ice crystals begin to grow at a certain rate, resulting in freeze concentration of the solution, a process that can result in both crystalline and amorphous solids, or in mixtures.11 In general, freezing is defined as the process of ice crystallization from supercooled water.15 The following section summarizes the physico-chemical fundamentals of freezing.At first, the distinction between cooling rate and freezing rate should be emphasized. The cooling rate is defined as the rate at which a solution is cooled, whereas the freezing rate is referred to as the rate of postnucleation ice crystal growth, which is largely determined by the amount of supercooling prior to nucleation.16-17 Thus, the freezing rate of a formulation is not necessarily related to its cooling rate.182.1 Freezing phenomena supercooling, ice nucleation and ice crystal formationIn order to review the physico-chemical processes that occur during freezing of pure water, the relationship between time and temperature during freezing is dis played in figure 1. When pure water is cooled at atmospheric pressure, it does not freeze spontaneously at its equilibrium freezing point (0C).19 This retention of the liquid state below the equilibrium freezing point of the solution is termed as supercooling.19 Supercooling (represented by line A) always occurs during freezing and is often in the range of 10 to 15C or more.12, 18 The degree of supercooling is defined as the difference between the equilibrium ice formation temperature and the actual temperature at which ice crystals first form and depends on the solution properties and process conditions.1, 6, 11, 20 As discussed later, it is necessary to distinguish between global supercooling, in which the entire liquid volume exhibits a similar level of supercooling, and local supercooling, in which only a small volume of the liquid is supercooled.14 Supercooling is a non-equilibrium, meta-stable state, which is similar to an activation energy necessary for the nucleation process .21 Due to density fluctuations from Brownian motion in the supercooled liquid water, water molecules form clusters with relatively long-living hydrogen bonds 22 almost with the same molecular arrangement as in ice crystals.11, 15 As this process is energetically unfavorable, these clusters break up rapidly.15 The probability for these nuclei to grow in both number and size is more pronounced at lowered temperature.15 Once the critical mass of nuclei is reached, ice crystallization occurs rapidly in the entire system (point B).15, 21-22 The limiting nucleation temperature of water appears to be at about -40C, referred to as the homogeneous nucleation temperature, at which the pure water sample will contain at least one spontaneously formed active water nucleus, capable of initiating ice crystal growth.11 However, in all pharmaceutical solutions and even in sterile-filtered water for injection, the nucleation observed is heterogeneous nucleation, meaning that ice-like clusters are fo rmed via adsorption of layers of water on foreign impurities.6, 11 Such foreign impurities may be the surface of the container, particulate contaminants present in the water, or even sites on large molecules such as proteins.23-24 Primary nucleation is defined as the initial, heterogeneous ice nucleation event and it is rapidly followed by secondary nucleation, which moves with a front velocity on the order of mm/s through the solution. 14, 25 Often secondary nucleation is simply referred to as ice crystallization, and the front velocity is sometime referred to as the crystallization linear velocity.14Once stable ice crystals are formed, ice crystal growth proceeds by the addition of molecules to the interface.22 However, only a fraction of the freezable water freezes immediately, as the supercooled water can absorb only 15cal/g of the 79cal/g of heat given off by the exothermic ice formation.12, 22 Therefore, once crystallization begins, the product temperature rises rapidly to nea r the equilibrium freezing point.12, 26 After the initial ice network has formed (point C), additional heat is removed from the solution by further cooling and the remaining water freezes when the previously formed ice crystals grow.12 The ice crystal growth is controlled by the latent heat release and the cooling rate, to which the sample is exposed to.22 The freezing time is defined as the time from the completed ice nucleation to the removal of latent heat (from point C to point D). The temperature drops when the freezing of the sample is completed (point E).21The number of ice nuclei formed, the rate of ice growth and thus the ice crystals size depend on the degree of supercooling.14, 20 The higher the degree of supercooling, the higher is the nucleation rate and the faster is the effective rate of freezing, resulting in a high number of small ice crystals. In contrast, at a low degree of supercooling, one observes a low number of large ice crystals.14, 19 The rate of ice crysta l growth can be expressed as a function of the degree of supercooling.23 For example for water for injection, showing a degree of supercooling of 10C +/- 3C, an ice crystal growth rate of about 5.2cm/s results.23 In general, a slower cooling rate leads to a faster freezing rate and vice versa. Thus, in case of cooling rate versus freezing rate it has to be kept in mind slow is fast and fast is slow.Nevertheless, one has to distinguish between the two basic freezing mechanisms. When global supercooling occurs, which is typically the case for shelf-ramped freezing, the entire liquid volume achieves a similar level of supercooling and solidification progresses through the already nucleated volume.12, 14 In contrast, directional solidification occurs when a small volume is supercooled, which is the case for high cooling rates, e.g. with nitrogen immersion. Here, the nucleation and solidification front are in close proximity in space and time and move further into non-nucleated solution. In this case, a faster cooling rate will lead to a faster freezing rate.12, 14Moreover, as ice nucleation is a stochastically event 6, 18, ice nucleation and in consequence ice crystal size distribution will differ from vial to vial resulting in a huge sample heterogeneity within one batch.6, 14, 27 In addition, during freezing the growth of ice crystals within one vial can also be heterogeneous, influencing intra-vial uniformity.5Up to now, 10 polymorphic forms of ice are described. However, at temperatures and pressures typical for lyophilization, the stable crystal structure of ice is limited to the hexagonal type, in which each oxygen atom is tetrahedrally surrounded by four other oxygen atoms.23 The fact that the ice crystal morphology is a unique function of the nucleation temperature was first reported by Tammann in 1925.28 He found that frozen samples appeared dendritic at low supercoolings and like crystal filaments at high supercooling. In general, three different types o f growth of ice crystals around nuclei can be observed in solution15 i) if the water molecules are given sufficient time, they arrange themselves regularly into hexagonal crystals, called dendrites ii) if the water molecules are incorporated randomly into the crystal at a fast rate, irregular dendrites or axial columns that originate from the center of crystallization are formed iii) at higher cooling rates, many ice spears originate from the center of crystallization without side branches, referred to as spherulites. However, the ice morphology depends not only on the degree of supercooling but also on the freezing mechanism. It is reported that global solidification creates spherulitic ice crystals, whereas directional solidification results in directional lamellar morphologies with connected pores.12, 14 While some solutes will have almost no effect on ice structure, other solutes can affect not only the ice structure but also its physical properties.19 Especially at high concent rations, the presence of solutes will result in a depression of the freezing point of the solution based on Raoultss Law and in a faster ice nucleation because of the promotion of heterogeneous nucleation, leading to a enormously lowered degree of supercooling.212.2 Crystallization and vitrification of solutesThe hexagonal structure of ice is of paramount importance in lyophilization of pharmaceutical formulations, because most solutes cannot fit in the dense structure of the hexagonal ice, when ice forms.23 Consequently, the concentration of the solute constituents of the formulation is increased in the interstitial region between the growing ice crystals, which is referred to as cryoconcentration.11-12 If this separation would not take place, a solid solution would be formed, with a greatly reduced vapor pressure and the formulation cannot be lyophilized.23 The total solute concentration increases rapidly and is only a function of the temperature and independent of the initial con centration.4 For example, for an isotonic saline solution a 20-fold concentration increase is reported when cooled to -10C and all other components in a mixture will show similar concentration increases.4 Upon further cooling the solution will increase to a critical concentration, above which the concentrated solution will either undergo eutectic freezing or vitrification.7A simple behavior is crystallization of solutes from cryoconcentrated solution to form an eutectic mixture.19 For example, mannitol, glycine, sodium chloride and phosphate buffers are known to crystallize upon freezing, if present as the major component.12 When such a solution is cooled, pure ice crystals will form first. Two phases are present, ice and freeze-concentrated solution. The composition is determined via the equilibrium freezing curve of water in the presence of the solute (figure 2). The system will then follow the specific equilibrium freezing curve, as the solute content increases because more pure water is removed via ice formation. At a certain temperature, the eutectic melting temperature (Teu), and at a certain solute concentration (Ceu), the freezing curve will meet the solubility curve. Here, the freeze concentrate is saturated and eutectic freezing, which means solute crystallization, will occur.7, 19 Only below Teu, which is defined as the lowest temperature at which the solute remains a liquid the system is completely solidified.19 The Teu and Ceu are independent of the initial concentration of the solution.7 In general, the lower the solubility of a given solute in water, the higher is the Teu.19 For multicomponent systems, a general rule is that the crystallization of any component is influenced, i.e. retarded, by other components.11 In practice, analogous to the supercooling of water, only a few solutes will spontaneously crystallize at Teu.11 Such delayed crystallization of solutes from a freezing solution is termed supersaturation and can lead to an even more ext reme freeze concentration.11 Moreover, supersaturation can inhibit complete crystallization leading to a meta-stable glass formation, e.g. of mannitol.12, 23 In addition, it is also possible that crystalline states exist in a mixture of different polymorphs or as hydrates.11 For example, mannitol can exist in the form of several polymorphs (a, b and d) und under certain processing conditions, it can crystallize as a monohydrate.11The phase behavior is totally different for polyhydroxy compounds like sucrose, which do not crystallize at all from a freezing solution in real time.11 The fact that sucrose does not crystallize during freeze-concentration is an indication of its extremely complex crystal structure.11 The interactions between sugar -OH groups and those between sugar -OH groups and water molecules are closely similar in energy and configuration, resulting in very low nucleation probabilities.11 In this case, water continues to freeze beyond the eutectic melting temperature and the solution becomes increasingly supersaturated and viscous.11 The increasing viscosity slows down ice crystallization, until at some characteristic temperature no further freezing occurs.11 This is called glassification or vitrification.18 The temperature at which the maximal freeze-concentration (Cg) occurs is referred to as the glass transition temperature Tg.11, 29 This point is at the intersection of the freezing point depression curve and the glass transition or isoviscosity curve, described in the supplemented phase diagram 30 or state diagram (figure 2).11 Tg is the point on the glass transition curve, representing a reversible change between viscous, rubber-like liquid and rigid, glass system.19 In the region of the glass transition, the viscosity of the freeze concentrate changes about four orders of magnitude over a temperature range of a few degrees.19 Tg depends on the composition of the solution, but is independent of the initial concentration.4, 11, 27 For exampl e, for the maximally freeze concentration of sucrose a concentration of 72-73% is reported.31 In addition to Tg the collapse temperature (Tc) of a product is used to define more precisely the temperature at which a structural loss of the product will occur. In general Tc is several degrees higher than Tg, as the high viscosity of the sample close to Tg will prevent .10 The glassy state is a solid solution of concentrated solutes and unfrozen, amorphous water. It is thermodynamically unstable with respect to the crystal form, but the viscosity is high enough, in the order of 1014 Pa*s, that any motion is in the order of mm/year.4, 11, 29The important difference between eutectic crystallization and vitrification is that for crystalline material, the interstitial between the ice crystal matrix consists of an intimate mixture of small crystals of ice and solute, whereas for amorphous solutes, the interstitial region consists of solid solution and unfrozen, amorphous water.19, 23 Thus, f or crystalline material nearly all water is frozen and can easily be removed during primary drying without requiring secondary drying.19 However, for amorphous solutes, about 20% of unfrozen water is associated in the solid solution, which must be removed by a diffusion process during secondary drying.19 Moreover, the Teu for crystalline material or the Tg respectively Tc for amorphous material define the maximal allowable product temperature during primary drying.19 Eutectic melting temperatures are relatively high compared to glass transition temperatures, allowing a higher product temperature during primary drying, which results in more efficient drying processes.19 If the product temperature exceeds this critical temperature crystalline melting or amorphous collapse will occur, resulting in a loss of structure in the freeze-dried product, which is termed cake collapse.11, 192.3 Phase separation and other types of freezing behaviorA characteristic property of multicomponent aqueo us solutions, especially when at least one component is a polymer, is the occurrence of a liquid-liquid phase separation during freezing into two liquid equilibrium phases, which are enriched in one component.11, 19 This phase separation behavior has been reported for aqueous solutions of polymers such as PEG/dextran or PVP/dextran but is also reported for proteins and excipients.32-33 When a critical concentration of the solutes is reached, the enthalpically unfavorable interactions between the solutes exceed the favorable entropy of a solution with complete miscibility.34 Another proposed explanation is that solutes have different effects on the structure of water, leading to phase separation.35Besides the separation into two amorphous phases, two other types of phase separation are stated in literature crystallization of amorphous solids and amorphization from crystalline solids.18 Crystallization of amorphous solids often occurs when metastable glasses are formed during freezing . In this case, e.g. upon extremely fast cooling, a compound that normally would crystallize during slower freezing is entrapped as an amorphous, metastable glass in the freeze-concentrate.12, 23 However, with subsequent heating above Tg, it will undergo crystallization, which is the basis for annealing during freeze-drying (see 3.3).19 Without annealing, the metastable glass can crystallize spontaneously out of the amorphous phase during drying or storage.18 Amorphization from crystalline solids, that can be buffer components or stabilizers, predominantly occurs during the drying step and not during the freezing step.18, 36Additionally, lyotropic liquid crystals, which have the degree of order between amorphous and crystalline, are reported to form as a result of freeze-concentration. However, their influence on critical quality attributes of the lyophilized product are not clarified.19 Moreover, clathrates, also termed gas hydrates, are known to form, especially in the presence of non-aqueous co-solvents, when the solute alters the structure of the water.233. Modifications of the freezing stepAs aforementioned, the ice nucleation temperature defines the size, number and morphology of the ice crystals formed during freezing. Therefore, the statistical nature of ice nucleation poses a major challenge for process control during lyophilization. This highlights the importance of a controlled, reproducible and homogeneous freezing process. Several methods have been developed in order to control and optimize the freezing step. Some of them only intend to influence ice nucleation by modifying the cooling rate. Others just statistically increase the mean nucleation temperature, while a few allow a true control of the nucleation at the desired nucleation temperature.3.1 Shelf-ramped freezingShelf-ramped freezing is the most often employed, conventional freezing condition in lyophilization.37 Here, at first, the filled vials are placed on the shelves of the lyophilizer and the shelf temperature is then decreased linearly (0.1C/min up to 5C/min, depending on the capacity of the lyophilizer) with time.37-38 As both water and ice have low thermal conductivities and large heat capacities and as the thermal conductivity between vials and shelf is limited, the shelf-ramped cooling rate is by nature slow.11 In order to ensure the complete solidification of the samples, the samples must be cooled below Tg for amorphous material respectively below Teu for crystalline material. Traditionally, many lyophilization cycles use a final shelf temperature of -50C or lower, as this was the maximal cooling temperature of the freeze-drier.7 Nowadays, it is suggested to use a final shelf temperature of -40C if the Tg or Teu is higher than -38C or to use a temperature of 2C less than Tg and Teu.1 Moreover, complete solidification requires significant time.11 In general, the time for complete solidification depends on the fill volume the larger the fill volume the more time is required for complete solidification.11 Tang et al.1 suggest that the final shelf temperature should be held for 1 h for samples with a fill depth of less than or equal to 1 cm or 2 h for samples with a fill depth of greater than 1 cm. Moreover, fill depth of greater than 2 cm should be avoided, but if required, the holding time should be increased proportionately.In order to obtain a more homogeneous freezing, often the vials are equilibrated for about 15 to 30 min at a lowered shelf temperature (5C 10C) before the shelf temperature is linearly decreased.1 Here, either the vials are directly loaded on the cooled shelves or the vials are loaded at ambient temperature and the shelf temperature is decreased to the hold temperature. 1, 5, 9 Another modification of the shelf-ramped freezing is the two-step freezing, where a supercooling holding is applied.(7) Here, the shelf temperature is decreased from room temperature or from a preset lowered shelf temperature to about -5 t o -10C for 30 to 60min hold. This leads to a more homogenous supercooling state across the total fill volume.1, 5 When the shelf temperature is then further decreased, relatively homogeneous ice formation is observed.5In general, shelf-ramped frozen samples show a high degree of supercooling but when the nucleation temperature is reached, ice crystal growth proceeds extremely fast, resulting in many small ice crystals.9, 39 However, the ice nucleation cannot be directly controlled when shelf-ramped freezing is applied and is therefore quite random.4 Thus, one drawback of shelf-ramped freezing is that different vials may become subject to different degrees of supercooling, typically about +/- 3C about the mean.4 This results in a great variability in product quality and process performance.4 Moreover, with the shelf-ramped freezing method it is not practical to manipulate the ice nucleation temperature as the cooling rates are limited inside the lyophilizer and the degree of supercoo ling might not change within such a small range.1, 143.2 Pre-cooled shelf methodWhen applying the pre-cooled shelf method, the vials are placed on the lyophilizer shelf which is already cooled to the desired final shelf temperature, e.g. -40C or -45C.1, 13-14 It is reported that the placement of samples on a pre-cooled shelf results in higher nucleation temperatures (-9,5C) compared to the conventional shelf-ramped freezing (-13.4C).14 Moreover, with this lowered degree of supercooling and more limited time for thermal equilibration throughout the fill volume, the freezing rate after ice nucleation is actually slower compared to shelf-ramped freezing.40 In addition, a large heterogeneity in supercooling between vials is observed for this method.14 A distinct influence of the loading shelf temperature on the nucleation temperature is described in literature.13-14 Searles et al.14 found that the nucleation temperatures for samples placed on a shelf at -44C were several degrees higher than for samples placed on a -40C shelf. Thus, when using this method the shelf temperature should be chosen with care.3.3 AnnealingAnnealing is defined as a hold step at a temperature above the glass transition temperature.12 In general, annealing is performed to allow for complete crystallization of crystalline compounds and to improve inter-vial heterogeneity and drying rates.1, 19 Tang et al.1 proposed the following annealing protocol when the final shelf temperature is reached after the freezing step, the product temperature is increased to 10 to 20C above Tg but well below Teu and held for several hours. Afterwards the shelf temperature is decreased to and held at the final shelf temperature. Annealing has a rigorous effect on the ice crystal size distribution 17, 41 and can delete the interdependence between the ice nucleation temperature and ice crystal size and morphology. If the sample temperature exceeds Tg, the system pursues the equilibrium freezing curve and some of th e ice melts.12, 41 The raised water content and the increased temperature enhance the mobility of the amorphous phase and all species in that phase.12 This increased mobility of the amorphous phase enables the relaxation into physical states of lower free energy.12 According to the Kelvin equation ice crystals with smaller radii of curvature will melt preferentially due to their higher free energy compared to larger ice crystals.12, 37, 41 Ostwald ripening (recrystallization), which results in the growth of dispersed crystals larger than a critical size at the expense of smaller ones, is a consequence of these chemical potential driving forces.12, 41 Upon refreezing of the annealed samples small ice crystals do not reform as the large ice crystals present serve as nucleation sites for addition crystallization.41 The mean ice crystal radius rises with time1/3 during annealing.37, 41 A consequence of that time dependency is that the inter-vial heterogeneity in ice crystal size distrib ution is reduced with increasing annealing time, as vials comprising smaller ice crystals catch up with the vials that started annealing containing larger ice crystals.12, 17, 37, 41 Searles et al.41 found that due to annealing multiple sheets of lamellar ice crystals with a high surface area merged to form pseudo-cylindrical shapes with a lower interfacial area. In addition to the increase in ice crystal size, they observed that annealing opened up holes on the surface of the lyophilized cake. The hole formation is explained by the diffusion of water from melted ice crystals through the frozen matrix at the increased annealing temperature. Moreover, in the case of meta-stable glass formation of crystalline compounds, annealing facilitates complete crystallization.42 Above Tg the meta-stable glass is re-liquefied and crystallization occurs when enough time is provided. Furthermore, annealing can promote the completion of freeze concentration (devitrification) as it allows amorphous water to crystallize.41 This is of importance when samples were frozen too fast and water capable of crystallization was entrapped as amorphous water in the glassy matrix. In addition, the phenomenon of annealing also becomes relevant when samples are optimal frozen but are then kept at suboptimal conditions in the lyophilizer or in a freezer before lyophilization is performed.113.4 Quench freezingDuring quench freezing, also referred to as vial immersion, the vials are immersed into either liquid nitrogen or liquid propane (ca. -200C) or a dry ice/ acetone or dry ice/ ethanol bath (ca. -80C) long enough for complete solidification and then placed on a pre-cooled shelf.9, 16 In this case the heat-transfer media is in contact with both the vial bottom and the vial wall 10, leading to a ice crystal formation that starts at the vial wall and bottom. This freezing method results in a lowered degree of supercooling but also a high freezing rate as the sample temperature is decreased very fast, resulting in small ice crystals. Liquid nitrogen immersion has been described to induce less supercooling than slower methods 9, 37, 39 , but more precise this faster cooling method induces supercooling only in a small sample volume before nucleation starts and freezes by directional solidification.12, 14 While it is reported that external quench freezing might be advantageous for some applications 39, this uncontrolled freezing method promotes heterogeneous ice crystal formation and is not applicable in large scale manufacturing.73.5 Directional freezingIn order to generate straight, vertical ice crystallization, directional respectively vertical freezing can be performed. Here, ice nucleation is induced at the bottom of the vial by contact with dry ice and slow freezing on a pre-cooled shelf is followed.9 In this case, the ice propagation is vertically and lamellar ice crystals are formed.9A similar approach, called unidirectional solidification, was described by Schoof et al. 43. Here each sample was solidified in a gradient freezing stage, based on the Power-Down principle, with a temperature gradient between the upper and the lower cooling stage of 50 K/cm, resulting in homogenous ice-crystal morphology.3.6 Ice-fog techniqueIn 1990, Rowe 44 described an ice-fog technique for the controlled ice nucleation during freezing. After the vials are cooled on the lyophilizer shelf to the desired nucleation temperature, a flow of cold nitrogen is led into the chamber. The high humidity of the chamber generates an ice fog, a vapor suspension of small ice particles. The ice fog penetrates into the vials, where it initiates ice nucleation at the solutio

Segregation Of Public Schools Effects On Student Achievement Education Essay

Segregation Of Public Schools Effects On Student Achievement Education canvassSchool systems across the U.S. ar voluntarily segregating their civilizes and give instructions may be much discriminate today than they were at the height of the Civil Rights Movement. There is overwhelming inference that sequestration is a toxic societal issue that serves to fortify discriminatory viewpoints and attitudes that negatively arrogate particular populations of people and innately puts Black and Latino assimilators at a disadvantage, weakening facets of social capital in these students neighborhoods and to a greater extentover widening the life-long action gap between these students and their White counterparts. Black students continue to score degrade than White students on standardized tests are underrepresented in institutions of higher learning and achieve overwhelmingly refuse rates of wealth.This query impart evaluate the discover of racial segregation on student nurt ureman transaction, which for purpose of this inquiry leave behind accept standardized testing performance as well as attributes of social mobility, in order to identify the best model for U.S. civilise systems that fosters equity in access to resources and high student achievement. In the present paper, several(prenominal) case studies that investigate the learning outcomes and pedantic achievement in unintegrated schools are evaluated. From review of these case studies a hypothesis can be organize that states that racial segregation is detrimental to non-white students, particularly Blacks and Latinos. The happening literary productions reviews demonstrate and support this hypothesis. The studies conclude that students who attend primarily nonage schools are not as well prepared for post-secondary commandment and that this achievement gap is directly related to the degree to which they experienced segregation. The look into as well shows that all student benefit from transition in their school setting White students are also disadvantaged by re-segregation of schools.Review of LiteratureIn a research article by J nonpareils-Sanpei (2009), the research first identifies specific overarching goals of unexclusive facts of life. The goals of education that this remove evaluated are singular outcomes (academic achievement and military control readiness) society outcomes ( rise upal empowerment and social capital ne cardinalrks) and, soulfulness social outcomes, such as future political engagement, social skills, and civic skills. Secondly the Jones-Sanpei research discussed the theory and research surrounding social capital and utilize information from five southern school districts and matching data from the 2000 Social Capital Community Benchmark Survey (SCCBS), (7) to examine the carnal knowledgeship between community social capital and segregated public schools. The discipline concluded by speculating nearly the potential effect of r e-segregating public schools on both community and individual social capital.The Jones-Sanpei study stated that several factors promote student individual academic outcomes, which are usually measured by standardized exam scores. agree to Jones-Sanpei (2009), student individual academic outcomes rely heavily on thatched roofer attributes, pedagogical philosophy (teaching styles), and school structure. The study also takes into consideration school-mixed factors (community measures) such as parental involvement, curriculum funding, equity issues and community involvement, deemphasizing the practice of using solely standardized testing models to quantify students learning outcomes and student potential future competitiveness. The literature further legitimizes the importance of community measures as weighty outcomes of public education. Specific forms of social capital that may be fostered by public education include obligations and expectations among a network of individuals, infor mation channels, and social norms. Social capital enables community members to trust one an early(a), establish business and political organizations, and to be involved in public education. Interactions through the public school medium kick in the potential to increase the universal social capital of a community. (Jones-Sanpei, 2009).The Jones-Sanpei study looked at two large southern school districts from 1992/1998 through 2005. The six school districts include in this analysis all had between 50,000 and 125,000 students in the 2005-2006 school-year. Additional community measures included the percent of each racial group in the community mean community education, mean community income, and population density based on 1990 numerate data. Community social capital measures tested by the study were interracial friendships, informal socializing and social trust. To test the hypothesis that communities with segregated public schools have lower community social capital, the study used t-tests, then used logistic regression to examine which social capital measures contributed to the interracial friendship measure.The findings of the study were that residents of communities with higher levels of school district segregation report significantly lower levels of general social trust temporary hookup communities with less segregated school districts describe significantly more social trust. Furthermore, respondents with higher general social trust were twenty-nine percent more likely to report having interracial friendships than respondents who reported lower general social trust. The findings support the hypothesis that segregated schools put children at a disadvantage for competing with their peers who ordain later have to work in a diverse society. It may be that community social capital influences local school district policymaking with respect to racial integration or that district segregation influences community social capital. In conclusion, there seems to b e a relationship between district segregation and community indicators of social capital. ( Jones-Sanpei, 2009)The (Goldsmith, 2009) study of the affect of re-segregation of public schools focused on the long-term effects of this segregated schooling on achievement levels of Black and Latino students. The study used longitudinal data from the field Education Longitudinal Study of 1988 which surveyed a have of eight graders from across the U.S. in the spring of 1988. Students were resurveyed in 1990, 1992, 1994 and 2000. The NELS88 data is relevant research about educational processes and outcome which include student learning, predictors of dropping out and effects on students access to equal education. Studying the minority-concentration and educational- key outment relationship is important because racialsegregation resultsinblacks and Latinos attendingschoolsand living in neighborhoods with higher proportions of minorities than whites. (Goldsmith, 2009, 4) This study hypothesiz ed that segregation perpetuates racial inequality and that the percentage of black or Latino in a neighborhood negatively affects individuals educational achievement.The focus of ( Goldsmith, 2009) was the circumstances surrounding segregated schools, and possible causes of the segregation. This research summarized findings of previous studies and assemble that The racial segregation of neighborhoods is principally settlementable for the racial segregation of schools (Goldsmith, 2009, p10).that show that schools that attempted to change from white, segregated schools to integrated schools had high rates of instructors and staff who reported that they did not receive adequate instruction to teach in integrated settings. Goldsmith also concluded that schools of segregated populations of Black and Latino students were less likely to graduate from high school and attain a bachelors degree than students in predominantly white schools. Empirical data from previous studies was analyz ed the correlation between segregated neighborhoods, segregated schools and educational outcomes. This research supports earlier discussed hypotheses of segregations affect on individual achievement and community social capital by analyzing the validity of the perpetuation theory. This theory brinytains that Blacks and Latinos who experience segregation in schools and their communities continue to be segregated in opposite social institutions over the course of their lives fail to develop networks with whites or the knowledge for developing these networks.These networks are important because they carry high-status knowledge, for example, about college admission procedures. An inability to form social ties with whites and to access information in white networks reduces the life chances of blacks and Latinos well after adolescence. (Goldsmith, 2009, p10). Goldsmith, 2009 also presents debate for future research to study schools in predominantly minority neighborhoods as it would pro vide valuable data on effects of segregation on student achievement. The regularity for this research included NELS data as stated before as well as an analysis of students residential zip code champaigns retrieved from eth 1990 and 1992 nosecount reports.The research conducted by (Austin, A M, 2008) clearly lays out data for the correlation between segregated schools and achievement on non-white students. The weight of the findings in this study further legitimize the importance of the two previous studies discussion of the long-term, quality of life disparities caused by the lack-luster community social capital of students in segregated schools and segregated neighborhoods. The main focus of this research was to compare the grade point fairishs of white male and female students to the grade point averages of male and female minority students. The students high school GPAs are then used a measure to project future college achievement by race. This research also supports the res earch presented by the NELS, clearly stating that racial segregation in schools across the U.S. directly affects minority students ability to compete in institutions of higher learning and eventually in the job market.(Austin, A M, 2008) found that the gap between white and minority students is about 11.2% of the average GPA. This study also looked at the effect of disagreeent environmental factors faced by minority students, specifically their segregation in early years of schooling, to explain the academic performance gap that existed once they reached the post-secondary level. Like previously reviewed studies, this study sound that minority students tend to live in segregated neighborhoods and attend segregated schools. This fact put minority students at a grave disadvantage at the post-secondary education level. For the research, student performance was tracked over a period of 6 years of 1331 public school students from the State of gallium who enter the University of West G eorgia in the Fall semester of 2001. Of the 1331 students in the study, 60% are female, 75.1% are white, 20.4% are black and the remaining students are Asian (1.1%), Hi sweep upic (1.4%), Native American (0.4%) and multi-racial (1.7%). The average high school GPA is 3.01, and the average SAT scores are 502 for the verbal test, and 497 for the math.The study by (Massey, 2006) reported that 2/3 of African American lived under conditions of high racial segregation, and that 2/3 of all African Americans attended minority dominant schools. Masseys study focused on the academic achievement of 3924 students entering 28 selective universities in the Fall semester of 1999. He surveys these freshmen and assembles a data set on social conditions in neighborhoods and high schools and finds that minority students from segregated backgrounds attended substandard schools, received lower quality instruction, were exposed to higher levels of disorder and violence, and were less prepared socially for campus life. (Massey, 2006, 6) By looking at the reported performance of these students over their first three semesters in college, Massey concluded that segregation has a significant impact on student achievement. He estimated that going from correspond integration to total segregation would lower GPAs by about 0.13, and that taking segregated backgrounds into account reduces the performance gap, but doesnt completely eliminate it. He also predicts that, because his data is from highly selective schools, in general the effect will be worse.The study by (Condron, 2009) found that the number one cause of the achievement gap between minority students and white students is racial segregation in the schools. This study cited the social and economic stratification (social capital) between black and white Americans as a barrier to student achievement in schools and later as adults. This research used 1st grade data from a longitudinal study of a pre-kindergarten cohort and found that s egregated schools cause an elevated role in the academic achievement gap as well as in social class disparities. This studys approach to the research discorded from most by looking at social class as it directly correlates with race as remote to looking at race as a sole determining factor of socio-economic status.This approach allowed the researcher to take into account that children growing up in different positions in the stratification hierarchy have categorically unequal and qualitatively different (rather than continuously graded) life and educational experiences and that poverty involves distinct solid hardships and environmental disadvantages that may stunt poor childrens cognitive development (Condron, 2009, p9). This research also went deeper into the school-level practices that attribute to student achievement gap more so than the other literature reviewed here. In addition to looking at social capital, which other studies also did, this study analyzed organizational p rocesses, teacher attributes and resources at the schools, in relation to student body composition. This study found that racially segregated schools had poor administrative cohesion, poorly developed staff, and substandard resources for students.In conclusion, the research is clear that condescension historic Supreme Court victories to desegregate U.S. public schools, the workforce may be integrated but our neighborhoods and schools are not. There needs to be more research done in the way of showing more qualitative data of the future overall individual achievement of minority students who attend predominantly minority schools, segregated from white students. This should be done so that that one of two things can take place. Either a de-segregation movement in education reform policy needs to be pushed through or schools that remain segregated need to be brought up to the same standards of predominantly white, high playacting school. It has already been proven that this has a sig nificant impact on students in two ways. The first solution may prove more favorable as research also provides evidence that a diverse school environment benefits both minority and white students alike.The study will seek to provide to answer these specific questionsWhat is the perspective of individual teachers of the effects of their students culture, class, and gender on their academic performance?How do students view their race and the race of their classmates as factors that affect their academic achievement and overall academic experience?How do students and teacher talk about racial inequality in their school?How does school segregation affect both white and non-white students?The proposed study will help bring awareness to these critical points.MethodologyFor my study I will use two new York City schools, both on the Lower East Side of Manhattan. One school is a charter school where of the 380 students, 43% are black, 29% are Hispanic, 1% are White and 1% are Asian (informa tion for the ethnicities of the other 25% was not provided at time of this proposal). 100% of the students who attend this k-5 school set apart for free lunch based on government poverty guidelines. The math and reading scores are high, among the best in the city (http//insideschools.org/?fs=1280). The other schools, a pubic school under the department of education, demographics is such of 336 students, 13% black, 36% Hispanic, 34%White, 13% Asian (http//insideschools.org/index12.php?fs=20). The math and reading scores at this school are less than stellar. I will select 15 respondents from each school for the question three students from each grade, grade 3 through 5, one Black, one White and one Asian. I will select two teachers from each grade level. Teachers in both upper and lower elementary school will be chosen and their ethnicities will be mixed to mirror those of the students being interviewed. This will be done to ascertain whether there are commonalty themes in regards to perspective of race and students achievement amongst the teachers in terms of their ethnic background. The teachers will be selected based on the test score of their students from previous years teachers with high results for student achievement will be selected.Data will be collected through interviews and observations. The interviews will be open-ended. They will focus on biographical information, what populations they have the most experience teaching, what they felt contributed to their success and trends in academic achievement they notice among the students they have worked with. They will also be asked general questions about how they prepare themselves to be heathenly aware, how they address conversion or multiculturalism in the classroom and how they communicate expectations to their students.A sample of interview questions for the teachers that will be used1. Tell me about yourself? (Where are you from, upbringing, culture, why you chose to be a teacher)2. Have you be en to any professional development workshop about diversity in the classroom?3. How do you think your background and/or teacher training influence how you interact with students? (Your rapport with the students, communication style, your ethnic background in comparison to your students)4. Do you set high expectations in your classroom? Why? Why not?5. Do your expectations change depending on the demographics of your class?A sample of interview questions for the students that will be used1. Do you spend time with kids who are different from you in school? How are they different?2. What is it like to go to school with these kids?3. Do you have friends that attend another school? What is it like for them?4. Does your teacher set high expectations for you?5. Is school difficult for you? Why or why not?6. Do you ever feel that you are different from your classmates or teachers? How?The teachers will be observed and video taped for ten hours in the span of three months. During the observa tions the researchers will take specific notes in regards to the teachers behavior and interaction with students. Potential codes that may arise include expectations, communication, empathy and rapport.The researchers will look at the data identify overarching themes that speak to the effects of the shift to re-segregation of public schools. The data will be studied to see how the experiences of students in racially diverse school settings differ from those in segregated school settings and how this experience may translate to differences in academic achievement and components of the social capital theory, specifically, obligations and expectations among a network of individuals, information channels, and social norms. The committee will also seek to see if there are common themes in regards to the teachers ethnicity and professional development in regard to their cultural sensitivity. They will look at how the perspectives and identity of the teachers reflects how they approach div ersity in the classroom and how they transmit information about a variety of topics, and how they set expectations for their students depending on students race. give-and-takeThis research will clearly show that re-segregation is a problem that needs to be taken under control. This research is not only concerned with academic achievement affected by segregation, but is also concerned with students and teachers experience and perspective of race in the school. The data collected will tell the accounting of what effect race has on a school community and the whole educational experience of students. I expect to find that in the charter school where students are segregated in that there is a very small percentage of white students and there is less of a mixed demographics, that teachers are under-prepared to teach in classrooms where their students race is different from their own. I also expect to find that these teachers have had little or no professional development for fostering cu ltural sensitivity in their classrooms.Most importantly, I expect to find that teachers expectations and perception of student achievement in the charter school will be inconsistent, and differ from those of teachers in the public school where there is a more diverse student population and that their attitudes will decrease the effectiveness of their classroom instruction, thereby obstructive the academic achievement of their students. Another expected result of this research is that students of different races will have significantly different responses to the question of what their teachers expectations. I expect that while teachers may report that they have the same expectations for all of their students, interview responses from students may very well reveal that students are intuitive and sensitive to the differences in teacher expectation that may be communicated through subtle teacher behavior like how much they are encouraged to participate in class discussions compared to other students.Possible shortcomings of the methods in this proposed study are that this data collected in the manner previously stated does not provide true longitudinal data to track specific students experiences of racial integration or segregation and their resulting academic achievement beyond elementary school. A longitudinal study may follow this study in the future.Further considerations for methodology that may affect the outcomes of this study are the affect of overall student interracial experiences. Limitations to the proposed research methods are that no data will be collected that gives researchers information for what the out-of-school experiences for the students are do they live in diverse neighborhoods or segregated communities? What are their parent interracial relationships and/or experiences that may inform them? In future research data may be collected on the degree to which students are segregated outside of school. To collect this data, student enrollment rec ords would have to be collected, tracking the students by race and places of residence, which can be generally identified by area zip codes. The possible problem with collecting this data may be that some students actually live outside the neighborhood listed on records. This could affect the findings of this research by misrepresenting the correlation between in-school segregation and neighborhood segregation that affect overall student segregation and academic performance. Another limitation of the interview method to collect data in this study is that students and teachers may answer as they feel they are expected to. This would make the data collected by interview about teacher rapport with students and expectations of students achievement inconsistent with data that may be collected through formal observations by researcher. As we see more school reforms that resemble business models and more charters, we also see more segregation. One possible implication of this research is t hat charter, which appear to contribute heavily to the re-segregation, will come under more stringent scrutiny and closer regulation. As for public schools that are a part of the board of education.Other possible implications of this research are that administrations will consider more professional development training for their teachers in eth way of preparing them to teach their diverse or non-diverse populations. As stated in the introduction of this proposal, one of the goals of public schooling is to produce critical thinkers who can function in what is becoming a more diverse global job market. Having said this, it is foreseeable that this research will be used to inform schools and educators to the extent to which they are meeting this requirement of public schooling or absentminded the mark. There sill also be a shift in the conversations that surround race in the school. Through the information gathered from the interview responses, teachers and administration will become aware of the disconnect between students experiences and teachers perception of students experiences.