This is a working overview of Collapse temperature, written for readers who want more than a one-paragraph summary but less than a textbook.
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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.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
| Property | Value | Notes |
|---|---|---|
| Primary phase change | Sublimation | Ice changes directly to vapor under reduced pressure |
| Typical chamber pressure | 0.01–0.5 mbar (1–50 Pa) | Below the triple point of water; product-specific |
| Typical product temperature during primary drying | −40 °C to −10 °C | Kept below collapse temperature |
| Typical residual moisture | 0.5–3% w/w | Target range varies by formulation and use |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilization is the US spelling |
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.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
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, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
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.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
=== 1990 === January 19–20: Soviet troops kill at least 131 Azerbaijanis for demonstrating for independence in Baku. January 30: the Polish United Workers' Party is dissolved, allowing democracy to be restored in Poland. January 31: U.S. Operation Just Cause ends, and Operation Promote Liberty begins in Panama. February 12–14: The Dushanbe riots occurred in Tajikistan. March 11: Lithuania declares independence from the Soviet Union. March 21: South Africa give de jure independence to South West Africa (Namibia). April 3: The Bulgarian Communist Party, the ruling party of Bulgaria, is dissolved. May 22: Both North Yemen and South Yemen unified. May 29: Boris Yeltsin is elected as the president of Russia. Yeltsin would serve as Russia's president until resigning on December 31, 1999, with Vladimir Putin taking over. May 30: The Washington Summit begins. June 12: Russia issues the Declaration of Sovereignty but never officially declares its independence from the Soviet Union. With the declaration, it declares that the laws and constitution of the Russian Soviet Federated Socialist Republic (RSFSR) to be above those of the Soviet Union. The loss of the RSFSR which was the most powerful of all the Soviet republics is a major blow to the Soviet Union. August 2: Ba'athist Iraq invades Kuwait, igniting the Gulf War. August 20: Estonia declares independence from the Soviet Union. August 23: Armenia declares independence from the Soviet Union. September 9: George H. W.
=== Velocity measurement === The effect of a mean flow of the gas in the path of the laser beam can be seen as a shift in the absorption spectrum, also known as Doppler shift. The shift in the frequency spectrum is related to the mean flow velocity by,
The Dexcom G5 was the first Dexcom continuous glucose monitor to be compatible with a mobile application. The accompanying app, named "Dexcom G5," allowed users to view their blood glucose readings on a smartphone and, with an intermediary iPhone, on an Apple Watch. The app remained available until the discontinuation of the Dexcom G5, at which point it was removed from app stores. The Dexcom G6 continued this functionality with its own dedicated application, "Dexcom G6," which provided real-time glucose readings and data-sharing capabilities. Upon the release of the Dexcom G7, a new application, "Dexcom G7," was introduced to support the updated system. The Dexcom G7 app is also available as the first system that connects directly to a smart watch. The Stelo by Dexcom also has an app which is similar to that of the G7, but has slightly different options.
Sources: en.wikipedia.org
Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also often glycosylated. Glycoproteins are also often important integral membrane proteins, where they play a role in cell–cell interactions. It is important to distinguish endoplasmic reticulum-based glycosylation of the secretory system from reversible cytosolic-nuclear glycosylation. Glycoproteins of the cytosol and nucleus can be modified through the reversible addition of a single GlcNAc residue that is considered reciprocal to phosphorylation and the functions of these are likely to be an additional regulatory mechanism that controls phosphorylation-based signalling. In contrast, classical secretory glycosylation can be structurally essential. For example, inhibition of asparagine-linked, i.e. N-linked, glycosylation can prevent proper glycoprotein folding and full inhibition can be toxic to an individual cell.
== Deaths == In the United States, in 2003, a 17-year-old who, according to his parents, was self-treating his anxiety with home-brewed poppy seed tea, died of pulmonary edema caused by acute morphine and codeine intoxication. A Drug Alert posted by the DOJ in 2010 pointed to five deaths possibly resulting from drinking of poppy tea. Since 2010, not less than 10 deaths presumably related to poppy tea consumption were reported by the FDA's Center for Food Safety and Applied Nutrition Adverse Event Reporting System (CAERS). In Canada, on 19 May 2012, a 19-year-old from Nova Scotia died after drinking the tea from a poppy seed pod he purchased on the Internet. In November 2012, a Tasmanian youth died after drinking tea brewed from seed heads, and a 50-year-old Tasmanian man died in similar circumstances in February 2011. Some instances of death or injury associated with the consumption of poppy seed tea have involved users who combined the beverage with other nervous system depressants (i.e. alcohol, tranquillizers, benzodiazepines).
Natural killer cell (NK) therapies and CAR-NK cell approaches are also being explored, leveraging NK cells' innate ability to target tumor cells. Other strategies include cancer vaccines, which aim to provoke an immune response against tumor-associated antigens, and may be either preventive or therapeutic. Immunomodulatory agents such as cytokines (e.g., interleukin-2, interferon-alpha) and Bacillus Calmette-Guerin (BCG) are used to enhance immune activity or alter the tumor microenvironment. Oncolytic virus therapies, which employ engineered viruses to selectively kill cancer cells while promoting systemic immunity, are also under investigation. In 2018, American immunologist James P. Allison and Japanese immunologist Tasuku Honjo received the Nobel Prize in Physiology or Medicine for their discovery of cancer therapy by inhibition of negative immune regulation.
Sources: en.wikipedia.org
Generally, American black bears are largely crepuscular in foraging activity, though they may actively feed at any time. Up to 85% of their diet consists of vegetation, though they tend to dig less than brown bears, eating far fewer roots, bulbs, corms and tubers than the latter species. When initially emerging from hibernation, they will seek to feed on carrion from winter-killed animals and newborn ungulates. As the spring temperature warms, American black bears seek new shoots of many plant species, especially new grasses, wetland plants and forbs. Young shoots and buds from trees and shrubs during the spring period are important to bears emerging from hibernation, as they assist in rebuilding muscle and strengthening the skeleton and are often the only digestible foods available at that time. During summer, the diet largely comprises fruits, especially berries and soft mast such as buds and drupes. During the autumn hyperphagia, feeding becomes virtually the full-time task. Hard mast becomes the most important part of the diet in autumn and may even partially dictate the species' distribution. Favored mast such as hazelnuts, oak acorns and whitebark pine nuts may be consumed by the hundreds each day by a single bear during the fall. During the fall period, bears may also habitually raid the nut caches of tree squirrels. Also extremely important in fall are berries such as huckleberries and buffalo berries.
== Role in disease == A genetic protein C deficiency, in its mild form associated with simple heterozygosity, causes a significantly increased risk of venous thrombosis in adults. If a fetus is homozygous or compound heterozygous for the deficiency, there may be a presentation of purpura fulminans, severe disseminated intravascular coagulation and simultaneous venous thromboembolism in the womb; this is very severe and usually fatal. Deletion of the protein C gene in mice causes fetal death around the time of birth. Fetal mice with no protein C develop normally at first, but experience severe bleeding, coagulopathy, deposition of fibrin and necrosis of the liver. The frequency of protein C deficiency among asymptomatic individuals is between 1 in 200 and 1 in 500. In contrast, significant symptoms of the deficiency are detectable in 1 in 20,000 individuals. No racial nor ethnic biases have been detected. At least 177 disease-causing mutations in this gene have been discovered. Activated protein C resistance occurs when APC is unable to perform its functions. This disease has similar symptoms to protein C deficiency. The most common mutation leading to activated protein C resistance among Caucasians is at the cleavage site in Factor V for APC. There, Arg506 is replaced with Gln, producing Factor V Leiden. This mutation is also called a R506Q. The mutation leading to the loss of this cleavage site actually stops APC from effectively inactivating both Factor Va and Factor VIIIa.
=== Knowledge-based === A typical data-mining-based prediction uses support-vector machines, decision trees, or neural networks. This method is usually very successful for calculating log P values when used with compounds that have similar chemical structures and known log P values. Molecule mining approaches apply a similarity-matrix-based prediction or an automatic fragmentation scheme into molecular substructures. Furthermore, there exist also approaches using maximum common subgraph searches or molecule kernels.
===== Kidnapping of Jesús Alfredo Guzmán Salazar and Iván Archivaldo Guzmán ===== In August 2016 in an upmarket restaurant called La Leche in the resort city of Puerto Vallarta, the CJNG kidnapped two sons of Joaquin Guzmán Loera (El Chapo), Jesús Alfredo Guzmán Salazar and Iván Archivaldo Guzmán Salazar, along with friends and then released them after negotiations. The event happened shortly after the incarceration of Joaquín Guzmán and was seen as a humiliation for the powerful Sinaloa cartel.
Sources: en.wikipedia.org
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.
The process has three main stages: freezing, primary drying, and secondary drying. Freezing sets the ice structure, primary drying removes free ice, and secondary drying removes bound water. Each stage uses specific temperature, pressure, and time settings.
No, it is a drying method rather than a sterilization method. Removing water can limit microbial growth, but it does not reliably kill microorganisms. Sterility must come from separate steps such as filtration, heat treatment, or aseptic processing.
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.