Discuss the role of emotion in psychology Essay

Emotion is often the greatest cause for either enhanced recall or impaired recall. Through many studies psychologists have found that it is not only facts we store in our memory but the emotion surrounding them.  Flashbulb memories involve an enduring imprint of events surrounding an important incident, the memory is not the event itself but where you were and what you were doing when you heard about it. Sheingold and Tenney (1982) provided evidence to support the concept of flashbulb memories. Participants were asked about personal memories and found most had good memories for when they were told and who told them. They found the flashbulb memories were strong and remained consistent over time; however there is no way of checking the accuracy of these memories. As shown by Sheingold and Tenney, a flashbulb memory’s characteristic involves consistency and has an unchanging nature and they also involve a high level of emotional arousal which leads to better recall of the event. However Wright (1993) found evidence that goes against this definition, the study involved looking at people’s memories of the Hillsborough football disaster in 1989, 5 moths after the event. It was found that most of the participants didn’t report strong flashbulb memories; in fact many people had reconstructed their memories and had mixed their own with other people’s accounts. This evidence therefore goes against the idea that flashbulb memories remain consistent over time. On the other hand Conway (1994) suggested that the reason some studies don’t support flashbulb memories is because the event wasn’t significant to the individuals. Conway et al used Mrs Thatcher’s resignation as the basis for the creation of flashbulb memories. 11 months after 86% of the UK participants has a strong and consistent flashbulb memory compared to only 29% participants from other countries. This research suggests that flashbulb memories will only be strong if the event surrounding it is significant to the individual; the UK participants would have been more aware and connected to Mrs Thatcher’s resignation than participants from other countries. The role of emotion is memory can also cause impaired memory. Freud proposed the idea of repression; unwanted memories are pushed down into the unconscious mind so you forget them. Freud described this process as a way of the ego protecting itself from emotional conflict which is often the result of harsh experiences. Williams (1994) interviewed women who has been admitted to hospital on the grounds of sexual assault, 20years previously, (they were told the study was a follow up of medical care). Williams found that 38% of the women did not show any recall of being sexually abused and that 16% of the women that did, said that at one time they couldn’t remember they had. This study therefore provides strong evidence to support the repression theory, a traumatic event was repressed and some couldn’t recall it even 20 years later. Repressed memories are defined as a traumatic event placed beyond conscious awareness. Because of this placement, these memories can also affect conscious thought. Forgetting a traumatic event, like Williams (1994) research, has also been studied through case studies. One of the most famous is Bavers (1981) study on sirhan sirhan, the man who shot Robert Kennedy, who has no recall of doing so. In this case the emotions of regret and shame were probably the cause of the repression and the reason he cannot remember what he did. It has also been suggested that repressed memories can also cause anxiety and disordered behaviour. A study that supports this concept was carried out by Karon and Widener (1997) who found that once trauma was recalled in therapy, mental illness in World War 2 veterans completely alleviated, therefore supporting Freud’s theory. However Loftus and Pickrell (1995) found evidence against Frued’s repression theory. The study was called ‘lost in the mall’ and the false memory of getting lost in a shopping centre as a child was implanted into the participants. After the debriefing 20% still held to their belief that this happened to them, even though it was a false memory showing trauma has a great affect on memory even though the memory was false but going against Frued as the memory wasn’t real. Another study by Loftus and Palmer created a theory called the ‘Weapon effect’ this was during a highly emotional event such as a robbery or assault, an eye witnesses’ recall was altered due to their focus on a weapon being used. Finally a depressive state also has an influence on memory. Negative emotions often create a negative recall bias which makes depressed people only focus on negative and unhappy experiences; a mood dependent memory. Lyketsos (2001) found in support of this that depression may lead people to be inattentive and so they don’t encode new memories into the long term memory well, therefore recall is much poorer. In further support of this Antikainen et al (2001) studied 174 depressed patients and found they performed better on memory tasks and had fewer memory problems after 6 months treatment. In conclusion emotion plays an important role in memory. It can often lead to enhanced memory, such as flashbulb memories, or impaired memory such as the repression of traumatic experiences. Negative emotion is also responsible for a lack of memory such as when someone is depressed. Overall memories are largely influenced by emotion the more positive we are the more likely we are to recall, the more negative the less likely we will recall and are more likely to forget.

Martin Luther King in campaigning in the North Essay

In 1966 Martin Luther King decided to focus on dealing with the problems in the North particularly Chicago. The problems that he encountered here were very different to those that he had had so much success with in the South. Dealing with the economic and social segregation that he faced here proved difficult for several reasons. The problems facing blacks in the North, stemmed from a variety of different areas including education, employment, housing etc. Although King was able to identify the problems being faced in these areas, particularly housing, he still largely relayed on the same tactics that he and the Southern Christian Leadership Conference (SCLC) had used in the South. However, the mayor of Chicago (Daley) would avoid making a hostile response such as that of ‘Bull’ Connor in Birmingham. The authorities here were more subtle to avoid gaining the attention of the media e.g. the police would avoid using brutality and Daley even blamed violence for social decay*. This prevented the movement from gaining as much publicity and support as in previous years. King also tried to come to some sort of agreement with Daley regarding housing. However, Daley was reluctant to do so fearing the loss of votes of the white working class. Actions such as this added to the anger that blacks in Chicago felt towards the white authorities and increased their unwillingness to co-operate. Both Mayor Daley’s refusal to help and King’s disorganisation when planning the Chicago campaign played an important role in its failure. Chicago suffered more from problems in racial division than other cities in the North, and so perhaps it was not a good starting point for the campaign here. Locals would sometimes blame blacks for inciting race riots and these divisions were illustrated by the marches organised by the SCLC in 1966, which ended in violence from mobs. * * In Chicago most blacks lived in ghettoes to the south of the city. Therefore it appears reasonable that these people often found it difficult to relate to Martin Luther King and his middle class background. The SCLC had never had much grass roots support unlike other organisations, such as the Student Non-violent Coordinating Committee (SNNC). Although in the South this had  still allowed them to have success, in Chicago most blacks were working class and looking for improvements in housing, less poverty and some overall change brought about by an end to de facto segregation. However, in the South the need for change had been more political- an end to de jure segregation. Given these differences, many northern blacks felt that King’s non-violent philosophy did not represent their views. It would be difficult to change these attitudes – here, perhaps as a result of poverty, the amount of gang warfare and crime was much higher than in the South. Change would undoubtedly take time- more than the few months that the SCLC had planned for the campaign to last. There were quite clear social divisions between black communities in the South and North. One of the most important examples of this is that the churches in the North were not as successful at organising their community as churches in the South had been. This was partly due to a lack of co-operation, and partly due to the fact that the Christian faith was much stronger in the South. It was at this point that many blacks were beginning to join alternative ‘black power’ groups. Overall it appears that King underestimated the differences between the North and the South and the divisions that were evident amongst the black community. He was unfamiliar with the attitudes of those in the North and did not make an accurate assessment of the situation. As a result of this the tactics employed by the SCLC were not as successful as originally hoped. * http://www.revision-notes.co.uk/revision/59.html ** http://www.reportingcivilrights.org/

MTV: Building Brand Resonance Essay

1 – What is the MTV brand image? How valuable are the MTV brand associations? What should its core values be? The MTV brand started out with a focus on the music where it helped to launch the visual impact of bands through music videos. MTV is a youth oriented brand, that started as a purely music video station, and has now involved into a pop-culture station with a mix of long-form programming, and videos. They created stars and termed new expressions like VJs and quickly differentiated their product from the competition. As a result of having a first-mover advantage they were the TV channel to go to in order to endorse your music. They managed to build up their brand and be a key channel for promotion where artists where demanding to have their own videos played on MTV. MTV remains a strong brand within the youth segment but needs to constantly evolve in order to maintain their position with new trends and changes emerging. The brand associations are strong since they are attached to a certain target-group (youths) that is very desirable to reach for many advertisers. The adolescence and early adulthood that MTV reaches are important for establishing enduring preferences for a specific type of brand that might follow a person throughout his life. Viewed as very â€Å"hip and now† many teens look to the channel to see what is popular and what the up and coming trends of today are. MTV has very strong brand attributes, with its viewers and even with people that do not view the channel as one they would frequently watch, therefore giving the brand strong brand associations. MTV has core values of staying on top of music and cultural trends, as a result ensuring their continued growth of their audience; MTV needs to stay relevant to stay on top. 2 – Describe the current sources of MTV’s brand equity. How have they changed over time? MTV creates its brand equity through high level of awareness and brand associations it’s made with its targeted viewers. MTV did this by using VJ’s or video jockeys to bring the viewers â€Å"along for the ride†. VJ’s made it’s a much more personal experience as if they were friends with the audience. The use of long-form programming has helped keep viewers interested in the channel by keeping relevant in its programming, by moving away from its roots as a music only channel and giving viewers what they were interested at any point in time. There are multiple genres and cultures represented on MTV and the channel high ratings among its key teen demographic, especially females. The evolution of the channel has kept the brand equity. In 2010 the MTV logo changed and no longer contained the tag-line â€Å"Music Television† to further emphasize their shift away from the pure music. By focusing more on programs that were â€Å"culture† shows and not only music they have managed to maintain a strong brand. Throughout their changes of focus MTV has managed to keep its core values intact. They are a channel for the younger generation that constantly provokes and stays on the edge of new concepts. By having a brand aimed at pop culture they constantly have to re-invent themselves to stay current. One of the biggest challenges for MTV is managing growth because usually when things become too popular it is no longer considered to be cool. 3 – What is the role of music within MTV? Do they need to put the â€Å"M† back in MTV? Music still plays a major part in MTV’s image and brand associations. Music and pop culture have always been interconnected, as many view the music that they listen to be how they express who they are as an individual. By having the same segments of people liking the same types of music, you can see the cliques within these segments, and usually these are how social trends begin. Although on a television station, music does not have the power to captivate viewers for prolonged periods of time; MTV found that long-form programming kept viewers tuned in on a regular basis, whereas music created grazing behaviors. Additionally, the channel viewers have changed therefore changing back to an all music channel I do not think would benefit the channel; viewers need to stay tuned in order for MTV to remain profitable and they are doing a good job of keeping their brand equity and associations. 4 – Discuss the role the Internet in programming. How should MTV best integrate the Internet into the brand? How might technology impact MTV’s future? MTV’s websites serve as an added channel to keep viewers engaged beyond just watching the channel they can now watch TV episodes and have wallpapers etc. However, the internet could pose the problem as sites like YouTube, World Star Hip Hop, and a collection of others give viewers access to video on demand, (what they want to see and when they want to see it), as opposed to watching a channel and waiting to hopefully see a song or wait for a program to air. MTV should continue to use the Internet to its advantage by offering exclusive online clips, interviews, and MTV personalized gear. They should continue to create apps and use Twitter, Facebook, and Instagram to connect to viewers. The MTV website already offers a variety of experiences to visitors and its greatest pull is that the brand owns the market as the resource for popular music. Drawing on that, and positioning the interactive aspect as a true storehouse for information is the most complementary stance MTVi (the interactive division of MTV) can take. With trendiness at its core, MTV will thrive as technology continues to change. 5 – How have MTV’s sister networks affected the parent channel’s brand equity? What changes, if any, would you make in positioning of the sister networks in order to create the optimal brand portfolio? MTV has effectively used its sister networks and parent channels to boost brand equity. By playing more music clips and videos on the MTV2 and VH1 channels, it spreads the core values of the brand. MTV started and made its name by showing music videos, so having its sister channels show more videos it extends the brand image and values. MTV is a global brand and therefore reaches many different people from all around the world. This means that they have an extensive range of viewers that are from different places, cultures, nationalities, ethnicities, etc. MTV’s global channels offer country specific programming to appeal to the many different countries and cultural tastes. MTV is doing a good job of positioning itself and its sister channels for continued success in boosting brand equity.

The Roles of The Presidents Essay Example | Topics and Well Written Essays - 750 words

The Roles of The Presidents - Essay Example Documented evidence available indicates that the administration of President Dwight David Eisenhower is considered to have been responsible for starting the war. His presidency is in fact looked at in two contexts, with the most prominent one involving the strategy he employed to wage the Cold War. He was intensely dedicated to the policy of containing socialism by deploying economic and military aid, forming defensive alliances, and finally by threatening to exercise U.S. military power (Jonathan, 2004). With the exit of the French from Vietnam, it is stated that Eisenhower decided to support the South Vietnamese President Ngo Dinh Diem believing to get some success in return. This was not to be the case With this failure, Eisenhower knew that a destructive atomic war was in the offing. Although he wanted to avert this possibility as much as possible, he was on the other prepared to employ clandestine and deliberately misleading methods to achieve his nation's national security goals (Jonathan, 2004). He had used the same strategy in Iran and later in Guatemala working through the Central Intelligence Agency. Although his party lost control of Congress, he won an overwhelming personal victory at the polls. President John F. Escalation of the conflict. President John F. Kennedy ascended into office with a conviction that America might and ought to shape the destiny of the world's developing countries. Primarily, Vietnam was not one of his mental preoccupations. In fact Vietnam was not on his list of priorities nor was it either discussed as a key issue at the transition meeting during the take over from Eisenhower. But sometime in the middle of his administration when the Vietnam issue had become more urgent, Kennedy simply remarked that Eisenhower never uttered the word Vietnam (Sylvia, 2004). He never strongly condemned the Vietnam War, an indication that he aided in its escalation. In fact it is only one of his key advisers who is known to have spoken against the war. President Kennedy started sending American forces to Vietnam in May 1961 and by the end of 1962, the military had received 11,300 US officers operating in South Vietnam, thus slowly escalating American involvement in the war. But towards the end of 1963, the war was still far from being over. This caused President Kennedy to organize the assassination of Diem of the South Vietnam regime. Before Kennedy was able to pull out 1,000 men from Vietnam at the end of the year as he had announced, was assassinated on November 22, 1963, having helped to escalate America's military, political, and maybe psychological commitment to Vietnam (Jonathan, 2004). Responsibility for America's disappointment in the Vietnam War is most squarely placed at the feet of Lyndon Johnson. It was him following President Kennedy's death in 1963 that increased America's military involvement in Vietnam and it was also during his administration that most American casualties were suffered. It is even documented that on 28 June 1966, the United States started bombing petrol, oil and lubricants facilities in the North Vietnamese cities of Hanoi and Haiphong, a move considered in many quarters as directed mainly against civilians (Jonathan, 2004). President Nixon on the other hand must be held accountable nearly as much as Lyndon Johnson for the failure of

Merit system raises vs. Performance raises Essay

Merit system raises vs. Performance raises - Essay Example Key steps are the main reason to have resulted in the expansion and estimated increase of the annual monetary value contrary to the reduction of annual monetary in the field (Bernanke, 2006). Firstly, the expansion of services of the Agency to South Carolina, secondly, the acquisition of Family Resources, Inc. of Beaufort, SC, which also resulted in staff increase. Finally, it is the strategies that are followed to sensor the environment for needs and adapt to provide solutions following even a restructure in organization hierarchy or proper use of information (Choo, 2001). Growing Home Southeast complied with the former by monitoring client needs to increase productivity and acquiring new skills. Growing Home Southeast is recommended to adopt the merit raise program to further increase productivity. The merit pay program is based on salary increase according to employee productivity and effectiveness (Silva, 1998). As one increases so does the other. Salary increments are not removed if productivity reduces employees therefore, are constantly motivated to achieve high performance. Bearing in mind such a payment program, it is implied that the selling product is appealing to the customer; not even the best marketing approaches can guarantee effective purchases of an indifferent product. Merit pay system is a performance-based system falling under this wider category.

Care of the Child within Accident and Emergency Case Study

Care of the Child within Accident and Emergency - Case Study Example The child whose care I am going to critically reflect on is a child with meningitis. This was a 2-year-old child who presented to the Accident and Emergency accompanied by anxious mother. This was a male child who presented to the A and E with loss of consciousness at home that was preceded by vomiting. This child was diagnosed to be a case of bacterial meningitis and I had to deliver care in the A and E. Milestones and Development: Obviously many children with the age group that I am going to discuss presented with different diagnoses during my placement in the Accident and Emergency, and milestones and development from both physiological and psychological perspectives have implications in diagnosis and management of these children. To discern an aberration, it is important that an overview of the normal milestones is done. Children accomplish maturation of different biological functions at an anticipated age with a margin of few months on the either side. Ideally, assessment of behavioural development should be interpreted from the time of appearance of definite skills while giving due considerations to environmental and social factors besides the stress of the actual clinical situation. In the phase between 2-3 years, the height increases further with 2.3 kg weight gain per year until the age of 5 years, and at the age of 2.5 years has a full set of 20 baby teeth (Rasen, D.S., 200 4). Psychosocial Milestones: Psychosocially, negativism grows out of child's sense of developing independence and says "no" to every command. Ritualism is important to toddler for security. Temper tantrums may result from toddler's frustration in wanting to do everything for self. The child shows parallel play as well as begins interaction with others and engages in associative play. Fears become pronounced, and the child continues to react to separation from parents but shows increasing ability to handle short periods of separation. The child has daytime bladder control and begins to develop nighttime bladder control. The child becomes more independent and begins to identify sex (gender) roles. The child explores environment outside the home and can create different ways of getting desired outcome (Parker, S., & Zuckerman, B., 1995). Child in the Accident and Emergency: The primary concerns of this age group that is relevant to the care that I delivered are many. These include "separation anxiety" relationship with mother is intense. Separation represents the loss of family and familiar surroundings, resulting in feelings of insecurity, grief, anxiety, and abandonment. The toddler's emotional needs are intensified by the parents' absence. Presence and treatment in the hospital or A anb E would mean changes in rituals and routines, all of which are important to sense of security, become a source of concern. In this age group, the child has limited capacity to understand reality and passage of time. There is inability to communicate and understanding of language and this affords the child limited communication between self and the world. Moreover while being investigated, examined, or treated, this represents to him loss of autonomy and independence. The child sees self as a separate being with some potential contr ol

The catcher in the rye Research Paper Example | Topics and Well Written Essays - 1250 words

The catcher in the rye - Research Paper Example After an emotive nosedive emphasized by Pencey Prep expulsion, Caulfield checks the Edmont Hotel and meanders the vicinities of Manhattan for 3 days. However, as Caulfield’s adventure progresses, he gradually begins bridging the gap between childhood innocence and the adulthood onset. The second last chapter of the novel follows Caulfield as a few significant occasions add to his advantage of personal closure concerning the loss of virtuousness between childhood and adulthood, a universal theme of the book. Caulfield’s walk on 5th Avenue at the beginning of the chapter signifies his many struggles related to his journey to adulthood throughout the book (Gohn 44). Caulfield literally aims at "catching" the children as they fall into adulthood. Caulfield, like any other teenager, stays scared of growing up. He understands that no one stands at the bottom of this metaphorical face with open arms to hold him as he tumbles, and that frightens him more than anything in his li fe. This fear of the cliff edge pushes Caulfield to walk on the streak between adulthood and childhood without committing to either flank, paralleling his sprints from one block to another (Sanford Pinsker 112). Additionally, Holden adheres to one of his only thoughts that he will ever find consoling for strength - his brother’s, (Allie) memory. As he runs, he "make[s] believes that he talks to his brother" (Salinger 257), and appreciates him when he crosses by the street securely. In a logic, Caulfield views Allie as his catcher on the bottom end of the cliff. He holds Allie's catcher's hand with him at every time, and it is apparent that Allie's death affected and infected him in an irreversible way that made it extremely hard for him to progress in his life. While he reflects to the past, Caulfield’s course of growing up turns out to be stunted. He calls out for Allie's memory to protect him from harms not only as he strolls along the streets in New York but when he rambles through his life. Without guides and uncertain, Caulfield never takes his time to cement precisely what he wants in life and consequently becomes trapped in the midpoint of adolescence. Convoying the discovery of smudged atrocities on his sister Phoebe's school, Caulfield begins to understand that individual’s loss of innocence remains` irresistible. He contemplates of how every child at the school could see the graffiti and, owing that he is young and innocent, he do not know what it implied. The thought drives him "near crazy" (Salinger 260). Caulfield discovers the fact that the communications written in school for children disturbing, wishing it could be possible that Phoebe with her friends could exist unpolluted by such rudimentary messages. In Caulfield’s views, young children like Phoebe signify everything that is pure and real about life, finding consolation in visiting Phoebe within earlier chapters. He despises the thought that their blamelessness w ill inevitably disappear one time. After seeing some more items of graffiti, Caulfield comments that "if you could get a million years of doing it in, you could not rub out even a half the "dirty" cryptograms in the world. It is practically impossible" (Salinger 262). Caulfield finally has his own epiphany - he understands that loss of innocence in children is unstoppable. Society is so corrupt for there to occur a utopian,

The Stock Plans Essay Example | Topics and Well Written Essays - 1500 words

The Stock Plans - Essay Example The major difference between the two accounting methods is that the intrinsic value based method overstates the income of the company. This method does not reveal the fair value of the stock, whereas the fair value based method, which is also recommended by FASB is based upon the estimated fair value of the company’s stock. Amount Of Compensation Under a stock options plan, 100 shares were offered to each employee that was purchased or exercised at $45 per share i.e., the grant price. The stock options would cost them $4500 ($45x100). However, the current market price of the stock is $60, which makes $6000 ($60x100) if sold in the market. The shares would obviously be sold on the current market value and hence each employee would get the difference ($6000-$4500) between the grant price and the current market value. The total amount of compensation that each employee would get is $1500 making the total compensation of $3000 paid by the company to two employees. Recording Of Sto ck Options In XYZ’s books The US GAAP requires the companies to expense out the employee stock options on the fair or intrinsic value, as well as disclose it in the company’s financial statements, which is supposed to decrease the company’s earnings significantly. Therefore, an expense will be recorded in the books of XYZ Corporation against the amount of employee stock options as per the accounting practice of FASB and the corresponding expense will be disclosed in the company’s financial statements.

Health and pe Essay Example | Topics and Well Written Essays - 500 words

Health and pe - Essay Example But how could I go about getting my people to exercise hard enough to start keeping weight off before I was replaced as King? I only had time to make about one Royal Decree before the official Weight and See Dinner to see whether I would stay king. If the people had more weight on them than the last Weight and See Dinner, I would need to start looking for another profession. After a lot of heavy thinking and finally falling asleep without a solution, I woke up the next morning with the perfect answer, dance! Instead of forcing my people to participate in strenuous activity, something none of them were necessarily naturally inclined to do, I simply performed a very active â€Å"Dance of Thanksgiving† in front of my astonished assembly just as breakfast was being served. After breakfast, I stood up and performed another dance, the â€Å"Dance of Satisfaction†, which was slower because my full belly just wanted to stretch. I did this same activity before brunch, lunch, the afternoon tea buffet, dinner and nighttime feast. I had so much fun doing it that I could help laughing through some of the dances and, by lunch, some of my people were looking more interested than shocked. By the nighttime feast, about half of them were joining me in the dances. By lunch the next day, everyone was dancing in wild movements of celebration before each meal and slower dances after each meal. By the third day, I caught my people dancing randomly during their other daily tasks just for the joy of movement. This was the perfect solution to the problem for many reasons. First, my people were participating in strenuous activity completely voluntarily, so they didn’t resent me for imposing a new rule and they didn’t resent the activity as something that they had to squeeze in between their other daily activities. Second, dancing is fun and it makes your body feel good, which is itself an encouragement to keep doing it. It also made the food preparers feel good because we

Cite and Correct Using Risk Assessment Assignment - 2

Cite and Correct Using Risk Assessment - Assignment Example zards as they can hit employees and injure them badly, that is in case they are opened while an employee is walking towards the point where the gate or door is swinging moving. The dust, gas, vapor and fumes produced are hazardous as they may damage parts of the body exposed to the substances. This may cause burns. Additionally, the chemicals may attack some organs, for example the lungs or liver, when the body absorbs some chemicals. An employee may touch bare wire, equipment that ungrounded properly or wet surfaces, which may lead to the employee being shocked. This may cause burns especially when the clothes are get fire. This may even lead to death. Some machinery reduces the levels of oxygen and this is hazardous to anyone in around as it may lead to suffocation. Employees deprived of oxygen for long periods may lead to brain damage and in extreme scenarios, death. For the walking work surface, any person entering the company is at risk. This is because any one can fall and get hurt since everyone is using the same polished floors. Additionally, doors swinging while being opened may hit anyone. Every single individual in the company is at risk of exposure. This is because the chemical produced, dust, gas, vapor and fumes, not excluding the noise, radiation and extreme temperatures, will not spare anyone. However, those people who spend more time in the company are more at risk than the visitors due to longer periods of exposure are. Everyone in the company is at risk in case the oxygen levels are low. This is because everyone needs oxygen and nobody will be spared. This also includes hazardous chemicals increasing to levels beyond the Permissible Exposure Limits. Impacts = the risk is only localized to the polished floors and the risk only increases when the floor is wet. Slipping may cause injuries but the probabilities of the injuries being serious are quite low. Impacts = the risk is only localized to a specific door being opened while an individual

Women in design Essay Example | Topics and Well Written Essays - 1000 words

Women in design - Essay Example One notable object that was designed by a woman during this period was the Lounge chair. The design was made by Greta Jalk commonly known as GJ chair. It was constructed by folding two plywood pieces. The process of construction was complex though it looked simple; with this complexity only three hundred pieces were produced in the 1960s. Greta had studied furniture started her own office in design after successfully finishing he education at the Copenhagen Royal Academy of Fine Arts. The complexity greatly discouraged the prosper of this design and it never went into industrial production in the 1960s. Greta’s Lounge chair can be compared to the child’s chair by Ray Eames. This chair was made from a single piece of plywood and then dyed red, blue, yellow, black or magenta. Unlike Greta’s chair Ray’s chair was not as complex to manufacture. Ray Eames looked into many factors while coming up with the design. It was cheap, colorful, robust, the chair had Eames’s approach to pragmatic was well suited by the use of plywood. The design was also economical compared to Gera’s chair, in addition to the fact that plywood is a lightweight material a child would find it easy to move the chair around making it easy to play with it. The back of the chair was heart shaped that represented the innocence and sweetness of the children. Unlike the Gera’s design Ray’s design thrived and got into industrial production. This ancient design by a woman greatly influenced the modern designs in the 20th century. Gera’s design was revived in the 20th century though she was not alive to see the impact her design had made in the 20th century. The first piece of furniture that was impacted by the design of Gera debuted in Germany. A large production factory was started to continue with the legacy of Gera in 2008. Modern designs have come up that have different uses from office furniture to home furniture. At the reception of modern

Tension Built Essay Example for Free

Tension Built Essay Arthur Miller was an American playwright who was born in 1915. Miller wrote The Crucible in 1953 during the McCarthy period when Americans were accusing each other of Pro-Communist beliefs. His purpose through writing The Crucible was to express his own views on McCarthyism, and he does this through the main plot, the 17th century Salemwitch hunt, which has a stark similarity to the trials during the McCarthy period. The citizens of Salem were against each other in every way, and one accusation would lead to the arrest and murder of another person, unless they told of other names. At the end of the play, the two most honest and noble people are killed, Rebecca Nurse and John Proctor. This is an exact replica of what was happening in America during the 1950s and this play is an attack upon the McCarthy period of America. The setting of Act 3 can be understood as an attack on the harshness of the authorities in Salem and 1950s America. Act 3 starts with the stage directions and these go on for a few sentences, each one being quite specific about the situation. The language used is negative and disheartening, creating an unwanted feeling throughout the audience, almost as if they are not meant to be there; even forbidding. We are told that sunlight (is) pouring through two high windows in the back wall but is being swallowed by the darkness beneath. In the play, these stage directions can be understood as the two windows being Giles and John Proctor, who tell the truth, but Danforth, the darkness beneath, is hiding the truth. This is also an attack on McCarthy and the 1950s American society, the two windows representing the innocent people of America, who refused to name names, and the darkness, Senator Joseph McCarthy and his communist supporters, the people who refused to put up with citizens who went against his views. Also, the light is shown to be outside, and the darkness inside, which represents the ignorance of the American people, as the truth is shown to be distant, and the lies near. The opening lines of Act 3 are said by Hathorne and Martha Corey. Hathorne is questioning whether Corey is a witch, a claim that she denies. Throughout their argument, there are regular interruptions, predominantly by Giles, the village idiot. This attacks McCarthy and his laws, as Miller is showing the village idiot clever enough to know that the allegations are false, and yet Danforth is unable to realise this. Because of the fact that Giles is threatening Danforths position, he is ordered to be taken away, Remove that man. This shows Danforth, and McCarthy, to be weak, as their only power is the fear they put into peoples hearts, not their education or their understanding of the case. Danforth is repeatedly shown to be weak throughout this act, as well as in the play on a whole, degrading him and McCarthy. The language Danforth uses towards the characters is very humiliating, Your old age alone keeps you out of jail. He does not want to be argued with, and sticks by his rules no matter what. By doing this, Miller is showing McCarthy to be weak, as people who stick by their rules often have nothing else to say, and control people by their only source of power-authority. This suggests that the citizens of Salem and in America during the 1950s were very naà ¯Ã‚ ¿Ã‚ ½ve, and would follow whatever they were told to do, but the ones who stood up for themselves, lost everything-including their lives. This shows any individual would die, but if groups of people were to stick together and lie, then, and only then, would they able to live. This puts fear into people, and they feel as if they have to lie in order to live, There are wheels within wheels in this village, and fires within fires. Proctor, the tragic hero of the play, dies at the end, saving the life of his wife and his unborn child. This shows what an unselfish and noble character he is, but is lead to death because of the injustice of the court. Miller is attacking the McCarthy courts by killing the two most noble characters at the end, and the ultimate evil, Abigail, is shown to live till the end of the play and further. In the movie, we are shown the scene where John Proctor is privately taking to Elizabeth, about what he should do. This scene is probably the most moving scene in the movie, and we are made to feel sorry for the situation he is put in. As well as sympathising with proctor, we are also angered, as to why he should die. By showing this scene, and perhaps lengthening it-it was about 4-5 minutes in the movie-Miller is expressing his anger towards McCarthy and his laws.

Physico-chemical Processes that Occur During Freezing

Physico-chemical Processes that Occur During Freezing 1. Introduction Lyophilization 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 marketed 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. [1] A 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 the 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.[7] In 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.[10]   The freezing step is of paramount importance. At first, freezing itself is 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.[1] While 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 process 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 freezing The 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.[18] 2.1 Freezing phenomena: supercooling, ice nucleation and ice crystal formation In order to review the physico-chemical processes that occur during freezing of pure water, the relationship between time and temperature during freezing is displayed in figure 1. When pure water is cooled at atmospheric pressure, it does not freeze spontaneously at its equilibrium freezing point (0 °C).[19] This retention of the liquid state below the equilibrium freezing point of the solution is termed as â€Å"supercooling†.[19] Supercooling (represented by line A) always occurs during freezing and is often in the range of 10 to 15 °C 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 â€Å"global supercooling†, in which the entire liquid volume exhibits a similar level of supercooling, and â€Å"lo cal 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 -40 °C, referred to as the â€Å"homogeneous nucleation temperature†, at which the pure water sample will contain at least one spontaneously f ormed 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 â€Å"heterogeneous nucleation†, meaning that ice-like clusters are formed via adsorption of layers of water on â€Å"foreign impurities†.[6, 11] Such â€Å"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.[14] Once 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 near 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).[21] The 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 crystal 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 10 °C +/- 3 °C, 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 â€Å"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, 14] Moreover, 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.[5] Up 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 â€Å"crystal filaments† at high supercooling. In general, three different types of growth of ice crystals around nuclei can be observed in solution[15]: 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, â€Å"irregular dendrites† or axial columns that originate from the center of crystallization are formed; iii) at higher coo ling 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 â€Å"global solidification† creates spherulitic ice crystals, whereas â€Å"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 based on Raoults`s Law and in a faster ice nucleation because of the promotion of heterogeneous nucleation, leading to a enormously lowered degree of supercooling.[21] 2.2 Crystallization and vitrification of solutes The 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 â€Å"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 reported when cooled to -10 °C and all other components in a mixture will show similar concentration increases.[4] Upon further cooling the solution will increase to a critical concentration, ab ove which the concentrated solution will either undergo eutectic freezing or vitrification.[7] A 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 temperat ure 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 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 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.[11] The 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 t he freezing point depression curve and the glass transition or isoviscosity curve, described in the â€Å"supplemented phase diagram† [30] or â€Å"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 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 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 pre vent .[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, 29] The 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, 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 resu lts 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 â€Å"cake collapse†.[11, 19] 2.3 Phase separation and other types of freezing behavior A characteristic property of multicomponent aqueous 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.[35] Besides 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, 36]   Additionally, 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.[23] 3. Modifications of the freezing step As 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 freezing Shelf-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 (0.1 °C/min up to 5 °C/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 -50 °C 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 -40 °C if the Tg` or Teu is higher than -38 °C or to use a temper ature of 2 °C 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 (5 °C 10 °C) 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 â€Å"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 -10 °C 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.[5] In 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 +/- 3 °C 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 supercooling might not change within such a small range.[1, 14] 3.2 Pre-cooled shelf method When 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. -40 °C or -45 °C.[1, 13-14] It is reported that the placement of samples on a pre-cooled shelf results in higher nucleation temperatures (-9,5 °C) compared to the conventional shelf-ramped freezing (-13.4 °C).[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 -44 °C were several degrees higher than for samples placed on a -40 °C shelf. Thus, when using this method the shelf temperature should be chosen with care. 3.3 Annealing Annealing 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 20 °C 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 water content and the increased temperature enhance the mobility of the amorphous phas e 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 distribution is reduced with increasing annealing time, as vials comprising smaller ice crystals â€Å"catch u p† 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 a nd 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.[11] 3.4 Quench freezing During quench freezing, also referred to as vial immersion, the vials are immersed into either liquid nitrogen or liquid propane (ca. -200 °C) or a dry ice/ acetone or dry ice/ ethanol bath (ca. -80 °C) 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 advantag eous for some applications [39], this uncontrolled freezing method promotes heterogeneous ice crystal formation and is not applicable in large scale manufacturing.[7] 3.5 Directional freezing In 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.[9] A 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 technique In 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 Physico-chemical Processes that Occur During Freezing Physico-chemical Processes that Occur During Freezing 1. Introduction Lyophilization 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 marketed 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. [1] A 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 the 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.[7] In 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.[10]   The freezing step is of paramount importance. At first, freezing itself is 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.[1] While 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 process 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 freezing The 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.[18] 2.1 Freezing phenomena: supercooling, ice nucleation and ice crystal formation In order to review the physico-chemical processes that occur during freezing of pure water, the relationship between time and temperature during freezing is displayed in figure 1. When pure water is cooled at atmospheric pressure, it does not freeze spontaneously at its equilibrium freezing point (0 °C).[19] This retention of the liquid state below the equilibrium freezing point of the solution is termed as â€Å"supercooling†.[19] Supercooling (represented by line A) always occurs during freezing and is often in the range of 10 to 15 °C 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 â€Å"global supercooling†, in which the entire liquid volume exhibits a similar level of supercooling, and â€Å"lo cal 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 -40 °C, referred to as the â€Å"homogeneous nucleation temperature†, at which the pure water sample will contain at least one spontaneously f ormed 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 â€Å"heterogeneous nucleation†, meaning that ice-like clusters are formed via adsorption of layers of water on â€Å"foreign impurities†.[6, 11] Such â€Å"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.[14] Once 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 near 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).[21] The 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 crystal 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 10 °C +/- 3 °C, 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 â€Å"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, 14] Moreover, 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.[5] Up 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 â€Å"crystal filaments† at high supercooling. In general, three different types of growth of ice crystals around nuclei can be observed in solution[15]: 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, â€Å"irregular dendrites† or axial columns that originate from the center of crystallization are formed; iii) at higher coo ling 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 â€Å"global solidification† creates spherulitic ice crystals, whereas â€Å"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 based on Raoults`s Law and in a faster ice nucleation because of the promotion of heterogeneous nucleation, leading to a enormously lowered degree of supercooling.[21] 2.2 Crystallization and vitrification of solutes The 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 â€Å"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 reported when cooled to -10 °C and all other components in a mixture will show similar concentration increases.[4] Upon further cooling the solution will increase to a critical concentration, ab ove which the concentrated solution will either undergo eutectic freezing or vitrification.[7] A 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 temperat ure 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 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 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.[11] The 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 t he freezing point depression curve and the glass transition or isoviscosity curve, described in the â€Å"supplemented phase diagram† [30] or â€Å"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 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 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 pre vent .[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, 29] The 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, 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 resu lts 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 â€Å"cake collapse†.[11, 19] 2.3 Phase separation and other types of freezing behavior A characteristic property of multicomponent aqueous 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.[35] Besides 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, 36]   Additionally, 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.[23] 3. Modifications of the freezing step As 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 freezing Shelf-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 (0.1 °C/min up to 5 °C/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 -50 °C 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 -40 °C if the Tg` or Teu is higher than -38 °C or to use a temper ature of 2 °C 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 (5 °C 10 °C) 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 â€Å"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 -10 °C 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.[5] In 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 +/- 3 °C 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 supercooling might not change within such a small range.[1, 14] 3.2 Pre-cooled shelf method When 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. -40 °C or -45 °C.[1, 13-14] It is reported that the placement of samples on a pre-cooled shelf results in higher nucleation temperatures (-9,5 °C) compared to the conventional shelf-ramped freezing (-13.4 °C).[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 -44 °C were several degrees higher than for samples placed on a -40 °C shelf. Thus, when using this method the shelf temperature should be chosen with care. 3.3 Annealing Annealing 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 20 °C 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 water content and the increased temperature enhance the mobility of the amorphous phas e 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 distribution is reduced with increasing annealing time, as vials comprising smaller ice crystals â€Å"catch u p† 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 a nd 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.[11] 3.4 Quench freezing During quench freezing, also referred to as vial immersion, the vials are immersed into either liquid nitrogen or liquid propane (ca. -200 °C) or a dry ice/ acetone or dry ice/ ethanol bath (ca. -80 °C) 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 advantag eous for some applications [39], this uncontrolled freezing method promotes heterogeneous ice crystal formation and is not applicable in large scale manufacturing.[7] 3.5 Directional freezing In 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.[9] A 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 technique In 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