Collapse temperature comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-10-30. Numbers and descriptions here follow the published literature rather than marketing material.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
| Property | Value | Notes |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
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.
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.
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.
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.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
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.
=== Impacts on wild fish === Some carnivorous and omnivorous farmed fish species are fed wild forage fish. Although carnivorous farmed fish represented only 13 percent of aquaculture production by weight in 2000, they represented 34 percent of aquaculture production by value. Farming of carnivorous species like salmon and shrimp leads to a high demand for forage fish to match the nutrition they get in the wild. Fish do not actually produce omega-3 fatty acids, but instead accumulate them from either consuming microalgae that produce these fatty acids, as is the case with forage fish like herring and sardines, or, as is the case with fatty predatory fish, like salmon, by eating prey fish that have accumulated omega-3 fatty acids from microalgae. To satisfy this requirement, more than 50 percent of the world fish oil production is fed to farmed salmon. Farmed salmon consume more wild fish than they generate as a final product, although the efficiency of production is improving. To produce one kilograms of farmed salmon, products from several kilograms of wild fish are fed to them – this can be described as the "fish-in-fish-out" (FIFO) ratio. In 1995, salmon had a FIFO ratio of 7.5 (meaning 7.5 kilograms of wild fish feed were required to produce one kilogram of salmon); by 2006 the ratio had fallen to 4.9. Additionally, a growing share of fish oil and fishmeal come from residues (byproducts of fish processing), rather than dedicated whole fish. In 2012, 34 percent of fish oil and 28 percent of fishmeal came from residues.
== Clinical significance == Human prohibitin 1 has some activity as a virus receptor protein, having been identified as a receptor for Chikungunya Virus (CHIKV) and Dengue Virus 2 (DENV-2). Little else is known about the activity of the prohibitins in viral pathogenesis.
=== Agentic misalignment === "Agentic misalignment" refers to situations in which an AI agent's actions or goals diverge from its designers' intentions. This occurs when an autonomous system pursues unintended strategies to achieve its objectives, a concern studied in AI safety research. Potential examples include AI agents attempting to sabotage an organization's systems when facing updates or deactivation. On July 21, 2026, OpenAI disclosed that during a capture the flag cybersecurity test, an unreleased AI model autonomously evaded containment restrictions, gained access to the public internet, and compromised Hugging Face, a platform where developers host and share AI models and datasets. Contributing factors to the incident were a lack of log monitoring of the software activities and inadequate sandboxing. On September 24, 2026, it was announced that an internal OpenAI frontier model autonomously gained unauthorized access on June 18 to the Medicare Statistics Reporting Service, an Australian Government website that holds data on the country's universal health insurance scheme Medicare. This was described as the first known case of an AI agent hacking a government network and has furthered concern about AI safety and loss-of-control. In response to these hacks, OpenAI announced that it would slow model development, including a two-week pause on reinforcement learning of its latest models to "assess model behavior, validate our safeguards, and establish more evidence of alignment before proceeding".
This is because the amount of active enzyme at a given concentration of irreversible inhibitor will be different depending on how long the inhibitor is pre-incubated with the enzyme. Instead, kobs/[I] values are used, where kobs is the observed pseudo-first order rate of inactivation (obtained by plotting the log of % activity versus time) and [I] is the concentration of inhibitor. The kobs/[I] parameter is valid as long as the inhibitor does not saturate binding with the enzyme (in which case kobs = kinact) where kinact is the rate of inactivation.
== Tissue distribution == CRF1 is expressed widely throughout both the central and peripheral nervous systems. In the central nervous system, CRF1 is particularly found in the cortex, cerebellum, amygdala, hippocampus, olfactory bulb, ventral tegmental area, brainstem areas, paraventricular hypothalamus, and pituitary. In the pituitary, CRF1 stimulation triggers the activation of the POMC gene, which in turn causes the release of ACTH and β-endorphins from the anterior pituitary. In the peripheral nervous system, CRF1 is expressed at low levels in a wide variety of tissues, including the skin, spleen, heart, liver, adipose tissue, placenta, ovary, testis, and adrenal gland. In CRF1 knockout mice, and mice treated with a CRF1 antagonist, there is a decrease in anxious behavior and a blunted stress response, suggesting that CRF1 mechanisms are anxiogenic. However, the effect of CRF1 appears to be regionally specific and cell-type specific, likely due to the wide variety of cascades and signaling pathways activated by the binding of CRF or CRF-agonists. In mice, offspring born to CRF1 -/- knockout mothers typically die within a few days of birth from lung dysplasia, likely due to low glucocorticoid levels. In the central nervous system, CRF1 activation mediates fear learning and consolidation in the extended amygdala, stress-related modulation of memory formation in the hippocampus, and brainstem regulation of arousal.
Sources: en.wikipedia.org
== Superintendent/CEO == In 2013, a governance reorganization led by then-County Executive Rushern Baker renamed the superintendent position to chief executive officer of PGCPS. Dubbed a 'takeover' of the county's school system, this shift increased the operational control for the CEO while limiting the school board's powers. Dr. Kevin Maxwell was the inaugural CEO of Prince George's County Public Schools, serving until 2018. He was succeeded by Dr. Monica Goldson, who remained in the position through the 2022–23 school year. After a rigorous 6-month nationwide search, the district shortlisted three candidates. Following an interview with County Executive Angela Alsobrooks, Millard House II, former Superintendent of the Houston Independent School District, was chosen to succeed Dr. Goldson. With House's appointment as Superintendent in June 2023, the district ceased referring to its head as CEO. Dr. Shawn Joseph was appointed interim superintendent for the 2025–2026 school year. On June 1, 2026, the appointment of Dr. Joseph to the Superintendent role was made permanent.
== Influencing factors == Tenderness is perhaps the most important of all factors impacting meat eating quality, with others being flavor, juiciness, and succulence. Tenderness is a quality complex to obtain and gauge, and it depends on a number of factors. On the basic level, these factors are meat grain, the amount and composition of connective tissue, and the amount of fat. In order to obtain a tender meat, there is a complex interplay between the animal's pasture, age, species, breed, protein intake, calcium status, stress before and at killing, and how the meat is treated after slaughter. Meat with the fat content deposited within the steak to create a marbled appearance has always been regarded as more tender than steaks where the fat is in a separate layer. Cooking causes melting of the fat, spreading it throughout the meat and increasing the tenderness of the final product.
==== Reaction hosts with size selectivity ==== MOFs might prove useful for both photochemical and polymerization reactions due to the tuneability of the size and shape of their pores. A 3D MOF {[Co(bpdc)3(bpy)] • 4dmf • H2O} (bpdc: biphenyldicarboxylate, bpy: 4,4′-bipyridine) was synthesized by Li and coworkers. Using this MOF photochemistry of o-methyl dibenzyl ketone (o-MeDBK) was extensively studied. This molecule was found to have a variety of photochemical reaction properties including the production of cyclopentanol. MOFs have been used to study polymerization in the confined space of MOF channels. Polymerization reactions in confined space might have different properties than polymerization in open space. Styrene, divinylbenzene, substituted acetylenes, methyl methacrylate, and vinyl acetate have all been studied by Kitagawa and coworkers as possible activated monomers for radical polymerization. Due to the different linker size the MOF channel size could be tunable on the order of roughly 25 and 100 Å2. The channels were shown to stabilize propagating radicals and suppress termination reactions when used as radical polymerization sites.
Although geneticists originally studied inheritance in a wide variety of organisms, the range of species studied has narrowed. One reason is that when significant research already exists for a given organism, new researchers are more likely to choose it for further study, and so eventually a few model organisms became the basis for most genetics research. Common research topics in model organism genetics include the study of gene regulation and the involvement of genes in development and cancer. Organisms were chosen, in part, for convenience—short generation times and easy genetic manipulation made some organisms popular genetics research tools. Widely used model organisms include the gut bacterium Escherichia coli, the plant Arabidopsis thaliana, baker's yeast (Saccharomyces cerevisiae), the nematode Caenorhabditis elegans, the common fruit fly (Drosophila melanogaster), the zebrafish (Danio rerio), and the common house mouse (Mus musculus).
Sources: en.wikipedia.org
The catalytic cycle begins with coordination of the Cu(I) species to the olefin, followed by oxidative addition at the γ position and an allylic shift to displace the leaving group. This generates a Cu(III) allyl complex intermediate. Finally, reductive elimination yields the final product and regenerates Cu(I). A Cu(III) intermediate has not been confirmed by isolation from allylic substitutions, but Cu(III) intermediates have been isolated before, thus providing credence to the proposed mechanism. If reductive elimination does not occur fast enough, the γ allyl complex can isomerize to the α allyl complex and yield the α substituted isomer as a byproduct. This side pathway can be prevented by using electron withdrawing ligands on copper, typically a cyanide or halide ligand, which promote reductive elimination.
CLIP or Class II-associated invariant chain peptide is the part of the invariant chain (Ii) that binds to the peptide binding groove of MHC class II and remains there until the MHC receptor is fully assembled. CLIP is one of the most prevalent self peptides found in the thymic cortex of most antigen-presenting cells. The purpose of CLIP is to prevent the degradation of MHC II dimers before antigenic peptides bind, and to prevent autoimmunity. During MHC II assembly in the endoplasmic reticulum, the invariant chain polypeptide complexes with MHC II heterodimers. In a late endosome/early lysosome, cathepsin S cleaves the invariant chain, leaving CLIP bound to the MHC II complex. In the presence of antigenic peptide fragments, HLA-DM partially binds to the MHC II peptide binding groove and acts as a catalyst, releasing CLIP and allowing peptides to bind. Antigenic peptides have a high affinity for the MHC II groove, and are readily exchanged for CLIP. This occurs in most cells expressing MHC II–however, in B cells, HLA-DO functions as the accessory protein. Both HLA-DM and HLA-DO interact with each other to act as chaperone proteins and prevent the denaturing of MHC II. MHC II with bound antigen is then transported to the plasma membrane for presentation. CLIP also can affect the differentiation of T cells. MHC II + CLIP complexes are upregulated on maturing dendritic cells, which activate and differentiate T cells into Thelper (Th) and Tcytotoxic (Tc) cells. Th cells can polarize into Th1 or Th2 effector cells depending on the presence of cytokines.
=== Response to pollution and environmental stress === Historical records indicate that X. parietina persisted in London despite severe air pollution, even when many other lichens disappeared. Mid-20th century mapping studies revealed that its distribution correlated with areas of moderate sulphur dioxide concentrations, but it was absent from the most polluted zones of central London, suggesting that while resistant to airborne contaminants, it has an upper tolerance limit. However, it is sensitive to certain pollutants, as demonstrated after the Torrey Canyon oil spill, when oil contamination and toxic dispersants caused widespread mortality on coastal rocks. Affected thalli lost their characteristic orange pigmentation, indicating chemical damage that interfered with enzymatic and protein activity, ultimately leading to detachment from the rock surface. The dispersant BP 1002, used during cleanup efforts, was later found to be highly toxic to marine life and coastal lichens. In X. parietina, its surfactant components disrupted algal cell membranes, reducing photosynthetic activity and accelerating thallus deterioration. Pollution affects both the population structure and development of X. parietina. There has been a decline in population density with increasing pollution levels; one study documented approximately 47 thalli per tree in lightly polluted zones, compared to 12 in moderately polluted areas and 9 in severely polluted regions. In unpolluted environments, the lichen completes its full life cycle, reaching maturity and old age.
The Kockums shipyard responsible for the design of the x-stern on Swedish submarines eventually exported it to Australia with the Collins class as well as to Japan with the Sōryū class. With the introduction of the type 212, the German and Italian Navies came to feature it as well. The US Navy with its Columbia class, the British Navy with its Dreadnought class, and the French Navy with its Barracuda class are all about to join the x-stern family. Hence, as judged by the situation in the early 2020s, the x-stern is about to become the dominant technology. When a submarine performs an emergency surfacing, all depth and trim control methods are used simultaneously, together with propelling the boat upwards. Such surfacing is very quick, so the vessel may even partially jump out of the water, potentially damaging submarine systems.
=== Fibrosis === Fibrosis is the scarring of connective tissue, one attribute is the excess deposition of collagen in the extracellular matrix of tissue. Research has shown that HSPs have a role in fibrotic diseases. HSP47 has been shown to be pro-fibrosis in various fibrotic diseases. During the process of fibrosis, HSP47 is expressed and is involved in the production of collagen. HSP47 could be a potential therapeutic agent for fibrotic disease, a down-regulation of HSP47 leads to decreased fibrotic progression.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.