This is a working overview of Collapse temperature, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-01-15 and is reviewed periodically as new material appears.
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.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
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 process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
| 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. |
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.
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.
=== Toxicity === A 2022 study concluded that SAMe could be toxic. Jean-Michel Fustin of Manchester University said that the researchers found that excess SAMe breaks down into adenine and methylthioadenosine in the body, both producing the paradoxical effect of inhibiting methylation. This was found in laboratory mice, causing harm to health, and in in vitro tests on human cells.
=== Stalemate develops between Smith and Wilson === Smith wrote to Wilson the day after the referendum, asking him to send Bottomley to Salisbury for talks. Wilson replied that Smith should instead come to London. The British and Rhodesians exchanged often confrontational letters for the next few months. Alluding to the British financial aid pledged to Salisbury as part of the Federal dissolution arrangements, Wilson's High Commissioner in Salisbury, J B Johnston, wrote to the Rhodesian Cabinet Secretary Gerald B. Clarke on 23 December that "talk of a unilateral declaration of independence is bound to throw a shadow of uncertainty on the future financial relations between the two governments". Smith was furious, seeing this as blackmail, and on 13 January 1965 wrote to Wilson: "I am so incensed at the line of your High Commissioner's letter that I am replying directly to you ... It would appear that any undertakings given by the British government are worthless ... such immoral behaviour on the part of the British government makes it impossible for me to continue negotiations with you with any confidence that our standards of fair play, honesty and decency will prevail."
Lymph enters the convex side of a lymph node through multiple afferent lymphatic vessels, which form a network of lymphatic vessels (Latin: plexus) and flows into a space (Latin: sinus) underneath the capsule called the subcapsular sinus. From here, lymph flows into sinuses within the cortex. After passing through the cortex, lymph then collects in medullary sinuses. All of these sinuses drain into the efferent lymphatic vessels to exit the node at the hilum on the concave side. These are channels within the node lined by endothelial cells along with fibroblastic reticular cells, allowing for the smooth flow of lymph. The endothelium of the subcapsular sinus is continuous with that of the afferent lymph vessel and also with that of the similar sinuses flanking the trabeculae and within the cortex. These vessels are smaller and do not allow the passage of macrophages so that they remain contained to function within a lymph node. In the course of the lymph, lymphocytes may be activated as part of the adaptive immune response. There is usually only one efferent vessel though sometimes there may be two, in contrast to the multiple afferent channels that bring lymph into the node. Medullary sinuses contain histiocytes (immobile macrophages) and reticular cells, the former of which, along with T and B cells, become activated in the presence of antigens through lymphatic flow. The fewer efferent vessels allow this flow to be slowed, providing time to activate and distribute a larger number of immune cells in the event of an infection.
Borderline personality disorder (BPD) is a personality disorder characterized by a pervasive, long-term pattern across several contexts of significant interpersonal relationship instability, extreme fear of abandonment, and intense emotional outbursts. People with BPD frequently exhibit self-harming behaviors and engage in risky activities, primarily caused by difficulties in regulating emotions. Symptoms such as dissociation, a pervasive sense of emptiness, and distorted sense of self are prevalent. Onset of symptoms can be triggered by events others perceive as normal, with the disorder typically manifesting in early adulthood and persisting across diverse contexts. BPD is often comorbid with substance use disorders, depressive disorders, and eating disorders. Studies estimate up to 10 percent of people with BPD die by suicide, a rate approximately 730 times greater than the general population in the United States. BPD faces significant stigmatization in media portrayals and the psychiatric field, leading to underdiagnosis and insufficient treatment. Causes of BPD are unclear and complex, implicating genetic, neurological, and psychosocial conditions in its development. The current hypothesis suggests BPD is caused by an interaction between genetic factors and adverse childhood experiences. BPD is significantly more common in people with a family history of BPD, particularly immediate relatives, suggesting genetic predisposition. There is a risk of misdiagnosis, with BPD commonly confused with a mood disorder, substance use disorder, or other mental health disorders.
Sources: en.wikipedia.org
=== Air pollution control === In addition to water treatment and environmental remediation, nanotechnology is currently improving air quality. Nanoparticles can be engineered to catalyze, or hasten, the reaction to transform environmentally pernicious gases into harmless ones. For example, many industrial factories that produce large amounts harmful gases employ a type of nanofiber catalyst made of magnesium oxide (Mg2O) to purify dangerous organic substances in the smoke. Although chemical catalysts already exist in the gaseous vapors from cars, nanotechnology has a greater chance of reacting with the harmful substances in the vapors. This greater probability comes from the fact that nanotechnology can interact with more particles because of its greater surface area. Nanotechnology has been used to remediate air pollution including car exhaust pollution, and potentially greenhouse gases due to its high surface area. Based on research done by the Environmental Science Pollution Research International, nanotechnology can specifically help to treat carbon-based nanoparticles, greenhouse gases, and volatile organic compounds. There is also work being done to develop antibacterial nanoparticles, metal oxide nanoparticles, and amendment agents for phytoremediation processes. Nanotechnology can also give the possibility of preventing air pollution in the first place due to its extremely small scale.
David Neal, the former Independent Chief Inspector of Borders and Immigration, has described the Home Office is dysfunctional and in urgent need of reform, citing problems with immigration as an example. 12 March – A spokesman for the prime minister describes the remarks allegedly made by Frank Hester about Diane Abbott as "racist and wrong". A recall petition opens in the Blackpool South constituency following Scott Benton's 35 day suspension from Parliament. 13 March – Sunak tells Prime Minister's Questions he will not return £10m donated to the Conservative Party by Frank Hester, because he has apologised and "his remorse should be accepted". The UK government announces a scheme to offer failed asylum seekers £3,000 if they agree to move to Rwanda voluntarily. The UK government announces a ban on foreign state ownership of British newspapers and news magazines following controversy over a potential purchase of The Telegraph by a consortium backed by the United Arab Emirates. Middlesbrough MP Andy McDonald regains the Labour whip. 14 March – Russia is reported to have jammed the GPS signal of an RAF plane carrying Defence Secretary Grant Shapps back to the UK from Poland the previous day for around 30 minutes as the plane flew near the border of the Russian territory of Kaliningrad. Speaking in the House of Commons, Secretary of State for Levelling Up, Housing and Communities Michael Gove outlines the UK government's new definition of extremism, and names five groups that would be assessed against the new criteria.
This tornado was part of a small outbreak that affected Europe that day, which produced a total of seven tornadoes. In Poland, one person was injured by an F2 tornado that impacted the towns of Librantowa and Koniuszowa, damaging numerous structures, 15 of which had their roofs torn off. Numerous reports of damaging straight-line winds and large, destructive hail were received as well. Weather of 2021 List of tornadoes rated on the International Fujita scale List of European tornadoes and tornado outbreaks List of F4 and EF4 tornadoes List of F4 and EF4 tornadoes (2020–present) October 2022 European tornado outbreak – An EF3 tornado struck Bihucourt F4 Tornado Hits Hodonín, Czechia - Jun. 24, 2021 tornádo v Hodoníně F4 Tornado Hits Hodonín, Czechia - Jun. 24, 2021 tornádo v Hodoníně (Part 2) Inside of an F4 tornado (full version)
The biosynthesis of mycofactocin from its precursor peptide MftA begins with decarboxylation of the C-terminal tyrosine residue by the radical SAM enzyme MftC, with help from the precursor-binding protein MftB. However, MftC appears next to perform a further modification to the MftA precursor peptide, an easily missed isomerization, by introducing a tyramine-valine cross-link, and consuming another S-adenosylmethionine in the process. The need for two modifications to MftA by MftC might explain the high degree of amino acid conservation in the last eight residues of MftA, as compared to the level of conservation seen for PqqA, precursor of PQQ. Next, the creatininase homolog MftE releases the C-terminal dipeptide, VY* (valine-tyrosine, where * indicates that the tyrosine was previously modified). Next, MftD converts the VY-derived dipeptide to premycofactocin, which has a biologically active redox center. And lastly, the glycosyltransferase MftF builds onto premycofactocin a variably sized, beta-1,4 linked oligomeric chain of glucose (i.e. cellulose), sometimes substituting derivatives such as 2-O-methylglucose. Mycofactocin, therefore, is not a single compound, but instead a mixture of closely related electron carriers that differ in the nature of their attached oligosaccharides.
== Later games == Valve released Team Fortress 2 in 2007. Fans created a mod for Half-Life 2, Fortress Forever, aiming to replicate the gameplay of Team Fortress Classic while using the more modern Source engine. Fans also made a similar mod of Team Fortress 2, Team Fortress 2 Classified, which seeks to marry gameplay elements and concepts from both entries alongside scrapped ideas from the sequel's development cycle and several entirely original additions.
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.
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.