collapse temperature raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-07-28. Anything still debated is marked as such rather than presented as settled.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Process removes water by sublimation under vacuum. |
| Typical primary drying shelf temperature | -40 C to -10 C | Set below the formulation's collapse temperature. |
| Typical chamber pressure | 0.05-0.3 mbar | Low pressure allows ice to sublime below its triple point. |
| Water content after drying | 0.5-3% by weight | Higher values may reduce storage stability for some materials. |
| Key thermal parameter | Collapse temperature | Measured by freeze-drying microscopy or differential scanning calorimetry. |
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
== Types == Think tanks vary by ideological perspectives, sources of funding, topical emphasis and prospective consumers. Funding may also represent who or what the institution wants to influence; in the United States, for example, "Some donors want to influence votes in Congress or shape public opinion, others want to position themselves or the experts they fund for future government jobs, while others want to push specific areas of research or education." McGann distinguishes think tanks based on independence, source of funding and affiliation, grouping think tanks into autonomous and independent, quasi-independent, government affiliated, quasi-governmental, university affiliated, political-party affiliated or corporate. A new trend, resulting from globalization, is collaboration between policy institutes in different countries. For instance, the Carnegie Endowment for International Peace operates offices in Washington, D.C., Beijing, Beirut, Brussels and formerly in Moscow, where it was closed in April 2022. The Think Tanks and Civil Societies Program (TTCSP) at the University of Pennsylvania, led by James McGann, annually rated policy institutes worldwide through 2021 in a number of categories and presented its findings in the Global Go-To Think Tanks rating index. However, this method of the study and assessment of policy institutes has been criticized by researchers such as Enrique Mendizabal and Goran Buldioski, Director of the Think Tank Fund, assisted by the Open Society Institute.
According to journalist Steven Dudley, who interviewed ex-FARC members as well as former members of the UP and the Communist Party, FARC leader Jacobo Arenas insisted to his subordinates that the UP's creation did not mean the group would lay down its arms; neither did it imply a rejection of the Seventh Conference's military strategy. In October 1987, Jaime Pardo Leal, who had been the UP's presidential candidate the previous year, was assassinated amid a wave of violence in which thousands of the party's members perished at the hands of death squads. According to Pecáut, the killers included members of the military and the political class who opposed Betancur's peace process and considered the UP to be little more than a "facade" for the FARC, as well as drug traffickers and landowners who were involved in the establishment of paramilitary groups.
In July 2010, Roche acquired mtm laboratories AG for up to 190 million EUR. In October, Roche acquired Anadys Pharmaceuticals, Inc. for $230 million. In December, Roche announced it would acquire Munich-based Verum Diagnostica GmbH, gaining entry to the fastest-growing field in the coagulation diagnostics market. On 26 June 2012, Roche announced the closure of the Nutley/Clifton campus, which was completed in 2013. The property is in the process of remediation. In July 2013, Roche Diagnostics acquired blood diagnostics company Constitution Medical Inc. for $220 million. Later, in September, Genentech announced it would acquire Arrayit Corporation. On 7 April 2014, Roche announced its intention to acquire IQuum for up to $450 million, as well as the rights to an experimental drug (ORY-1001) from Spanish company Oryzon Genomics for $21 million and up to $500 million in milestone payments. On 2 June, Roche announced its intention to acquire Genia Technologies Inc. for up to $350 million. In August 2014, the company agreed to purchase Californian-based pharmaceutical firm InterMune for $8.3 billion, at $74 a share this represents a 38% premium over the final share closing price, as well as Santaris Pharma A/S for $450 million. In December 2014, the company acquired next-generation sequencing processing company Bina Technologies for an undisclosed sum and Dutalys GmbH a developer of next-generation anti-bodies.
=== Light weight === Portable explosive detectors need to be as light weight as possible to allow users to not fatigue when holding them. Also, light weight detectors can easily be placed on top of robots.
On some early frost-free models, the defrost limiter also sends a signal to the defrost timer to start the compressor and fan as soon as it shuts off the heating element before the timed defrost cycle ends. When the defrost cycle is completed, the compressor and fan are allowed to cycle back on. Frost-free refrigerators, including some early frost-free refrigerators/freezers that used a cold plate in their refrigerator section instead of airflow from the freezer section, generally don't shut off their refrigerator fans during defrosting. This allows consumers to leave food in the main refrigerator compartment uncovered, and also helps keep vegetables moist. This method also helps reduce energy consumption, because the refrigerator is above freeze point and can pass the warmer-than-freezing air through the evaporator or cold plate to aid the defrosting cycle.
Sources: en.wikipedia.org
=== Names === A similar combination is also sold under the brand name Mydayis. Mydayis contains the amphetamines dextroamphetamine sulfate, dextroamphetamine saccharate, amphetamine aspartate monohydrate, and amphetamine sulfate capsule.
=== Heart === Cardiomyocyte necrosis activates an inflammatory response that serves to clear the injured myocardium from dead cells, and stimulates repair, but may also extend injury. Research suggests that the cell types involved in the process play an important role. Namely monocyte-derived macrophages tend to induce inflammation while inhibiting cardiac regeneration, while tissue resident macrophages may help restoration of tissue structure and function.
That December the headquarters of the 4th Ferrying Group of the Army Air Forces Air Transport Command shifted to the airport. The group was tasked with sending new aircraft overseas; pilots departed Memphis for South America and then flew over the South Atlantic Ocean to Africa. Personnel such as mechanics and engineers underwent training at the base and then traveled overseas. Chicago and Southern's repair facilities at the airport were used to repair military planes. Commercial air service continued, though it was limited. The ferrying group's postwar activities included moving planes off deactivated bases. For a period in 1946, Memphis served as headquarters for the Continental Division of the Air Transport Command, which oversaw the 4th Ferrying Group and ran scheduled flights for military personnel throughout the country. The ferrying group ceased operations in March 1947. City officials reached an agreement with the federal government in January 1949 to regain control of the airfield. Five trunk carriers flew to Memphis as of 1947, and two years later, a regional airline named Southern Airways launched operations with multi-stop service to Atlanta. The airport opened the first air-cargo terminal in the country in February 1958. The following year, passenger counts crossed one million. In August 1960, the city received its first scheduled jet flight; Delta Air Lines started using Convair 880s on its Chicago–Memphis–New Orleans route. The United States Supreme Court in Turner v. City of Memphis ordered the desegregation of the airport in 1962.
increased price due to cost-intensive production; sensitivity to moisture (tablets can degrade at higher humidity); poor physical resistance (easy to break); limited ability to incorporate higher concentrations of active drug.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, often under the same vacuum. The two stages differ in the water state being removed.
Freezing determines ice crystal size, pore structure, and the concentration of solutes in remaining liquid. Faster freezing generally creates smaller ice crystals and a denser dried matrix. These features affect drying rate and reconstitution behavior.
Lyophilization reduces water content but usually leaves a small amount of water in the dried material. Some water remains bound to solids or trapped in the dried matrix. Very low water targets can require extended secondary drying, which may alter product stability.
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.