If you have been reading about Collapse temperature and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-01-15. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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 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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
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.
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.
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 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.
==== Co-evolutionary evidence ==== An independent molecular analysis trying to establish the dates when bat ectoparasites (bedbugs) evolved came to the conclusion that bedbugs similar to those known today (all major extant lineages, all of which feed primarily on bats) had already diversified and become established over 100 million years ago, suggesting that they initially all evolved on non-bat hosts and "bats were colonized several times independently, unless the evolutionary origin of bats has been grossly underestimated". No analysis has provided estimates for the age of the flea lineages associated with bats. The oldest known members of a different lineage of bat ectoparasites (bat flies), however, are from roughly 20 million years ago, well after the origin of bats. The bat-ectoparasitic earwig family Arixeniidae has no fossil record but is not believed to originate more than 23 million years ago.
The first pathway begins with a P450 enzyme, ibogamine-10-hydroxylase (I10H), and methylation of noribogaine-10-Ο-methyltransferase (N10OMT) to produce (-)-voacangine. Polyneudridine aldehyde esterase-like 1 (PNAE1) and a spontaneous decarboxylation can convert (-)-voacangine to (-)-ibogaine. The second pathway consists of PNAE1 and the spontaneous decarboxylation occurring first to yield (-)-ibogamine, then the reaction of I10H-mediated hydroxylation and N10OMT-catalyzed O-methylation to produce (-)-ibogaine.
=== Budget framework negotiations === Initially, on February 21, 2025, the Senate approved S. Con. Res. 7 by 52–48, intended to be the first of two reconciliation instruction bills. The resolution allowed for a future reconciliation bill containing $175 billion for immigration and border enforcement, $150 billion for the military and would not extend the 2017 Trump tax cuts. Senator Rand Paul of Kentucky was the only Republican to oppose the resolution. The Senate intended to allow the House to pass reconciliation instructions first. At the time of the bill's passage, the House faced opposition to its one-bill approach from fiscally conservative members. On February 25, 2025, the House of Representatives approved H. Con. Res. 14 by a 217–215 vote. The resolution would allow Republicans to pass a budget containing tax cuts while reducing federal spending. The resolution would also allow Congress to raise the debt limit by $4 trillion. The resolution was briefly pulled due to opposition from fiscally conservative Republicans Thomas Massie of Kentucky, Tim Burchett of Tennessee, Warren Davidson of Ohio, and Victoria Spartz of Indiana. Leadership convinced all but Massie to support the resolution, and the vote happened as scheduled. Initially, some moderate Republicans also expressed opposition over the possibility that the resolution would necessitate cuts to Medicare and Medicaid. In the end, Massie was the only House Republican to vote against the resolution. In the early hours of April 5, 2025, the Senate approved an amended version of H. Con. Res. 14 by a 51–48 vote.
TikTok enables content monetization to creators who meet specific requirements and reside in eligible areas. TikTok first offered this monetization in 2020 through the Creator Fund, which contained a finite amount of money split amongst creators that qualified for it. In 2024, this fund was replaced with the Creator Rewards Program. Creators that have a video reach the top 4% of the platform and have more than 100,000 followers are eligible to receive 50% of its ad revenue. TikTok also has a tool called Creative Exchange that connects creators with potential sponsorship deals. As the platform has grown significantly over time, companies have increasingly advertised through influencer marketing. The platform's algorithm also contributes to the influencer marketing potential, as it picks out content according to the user's preference. Sponsored content is not as prevalent on the platform as it is on other social media apps, but brands and influencers still can make as much as they would if not more in comparison to other platforms. Influencers on the platform who earn money through engagement, such as likes and comments, are referred to as "meme machines". In 2021, The New York Times reported that viral TikTok videos by young people relating the emotional impact of books on them, tagged with the label "BookTok", significantly drove sales of literature. Publishers were increasingly using the platform as a venue for influencer marketing. TikTok has also increased sales of adult coloring books.
Sources: en.wikipedia.org
==== Relations with Free Peru ==== After the new ministers were sworn in, Free Peru's spokesperson Waldemar Cerrón called the new cabinet a betrayal of the majority. He stated that Free Peru will keep fighting for a cabinet that represents all Peruvian people. According to Edgar Tello, a Congressman from Free Peru, his party has agreed to not give confidence to the Vásquez cabinet. Tello also indicated that if Castillo does not respond to Free Peru's request to reevaluate the cabinet, then Free Peru could become part of the opposition. When asked if the party would support impeachment against Castillo, Tello stated that the Free Peru caucus has not made a decision in this regard. However, he noted that he wished that Free Peru wouldn't have to resort to such extremes. The next day, Free Peru released a statement, in which they stated they will not support the cabinet but ruled out acting to obstruct the Government. Waldemar Cerrón claimed that the party was more united than ever, and that they support President Castillo. That said, a faction of Free Peru came out in support of the new cabinet. Ultimately, 16 of Free Peru's parliamentarians, including former prime minister Guido Bellido, voted against giving confidence to the Vásquez cabinet. 19 of Free Peru's parliamentarians voted to give confidence to the Vásquez cabinet. On 6 November 2021, Free Peru's Regional Secretary Jorge Spelucín claimed that President Castillo had cut off all communication channels with Free Peru.
== Awards and honors == Arthur C. Cope Scholar Award (2024) from the American Chemical Society for his foundational contributions to organic chemistry. Cathay Award (2024) from the Chinese Peptide Society for his work in peptide science. Max Bergmann Kreis Gold Medal (2011) for outstanding contributions in peptide chemistry. Vincent du Vigneaud Award (2010) from the American Peptide Society.
=== Challenges === The stigma surrounding addiction can heavily influence opioid addicts not to seek help. Stigma may arise from a variety of sources, including friends, family, employers, and healthcare providers. People who experience stigma related to their opioid use disorder are less inclined to seek out treatment or remain in treatment because of shame or feelings of being judged. Therefore, reducing stigma via education and support improves outcomes in the treatment of OUD and makes people more confident in seeking treatment. Many people view addiction as a moral failing rather than a medical condition, which can lead to feelings of shame and isolation. This stigma can affect family members, making it difficult for them to support their loved ones effectively. According to position papers on the treatment of opioid dependence published by the United Nations Office on Drugs and Crime and the World Health Organization, care providers should not treat opioid use disorder as the result of a weak moral character or will but as a medical condition. Some evidence suggests the possibility that opioid use disorders occur due to genetic or other chemical mechanisms that may be difficult to identify or change, such as dysregulation of brain circuitry involving reward and volitional experience. It has also been hypothesized that endocrine and autonomic nervous system abnormalities can be opioid-induced. Critically, the endogenous opioid system is involved in reward; changes to this system affect experience and subsequent behavior.
=== Pharmacokinetics === The two active components of the medication, ibuprofen and hydrocodone, do not affect each other's absorption characteristics or other pharmacokinetic parameters. After an oral dose, the peak level of hydrocodone in the blood is reached 1.7 hours after administration. The blood levels of ibuprofen peak 1.8 hours after oral administration.
Other methods of weight loss include use of anti-obesity drugs that decrease appetite, block fat absorption, or reduce stomach volume. Obesity has been resistant to drug-based therapies, with a 2021 review stating that existing medications are "often delivering insufficient efficacy and dubious safety". Semaglutide has also become popular recently as an aid in weight loss. It is particularly beneficial for those with type 2 diabetes and obesity.
Sources: en.wikipedia.org
== History == Trazodone was developed in Italy, in the 1960s, by Angelini Research Laboratories as a second-generation antidepressant. It was developed according to the mental pain hypothesis, which was postulated from studying patients and which proposes that major depression is associated with a decreased pain threshold. In sharp contrast to most other antidepressants available at the time of its development, trazodone showed minimal effects on muscarinic cholinergic receptors. Trazodone was patented and marketed in many countries all over the world, starting with Italy in 1972 and West Germany in 1977. It was approved by the Food and Drug Administration (FDA) in 1981 and was the first non-tricyclic or MAOI antidepressant approved in the US.
==== Other ==== Treatment of breast cancer in women, although they are now rarely used for this purpose due to their marked virilizing side effects. In low doses as a component of hormone therapy for postmenopausal and transgender women, for instance to increase energy, well-being, libido, and quality of life, as well as to reduce hot flashes. Testosterone is usually used for this purpose, although methyltestosterone is also used. Male hormonal contraception; currently experimental, but potential for use as effective, safe, reliable, and reversible male contraceptives. Assistant in the treatment of Raynaud's Phenomenon and peripheral acrocyanosis. Testosterone and other anabolics tend to be potent vasodilators, which can significantly improve bloodflow in individuals prone to vasoconstriction.
The δ values and absolute isotope ratios of common reference materials are summarized in Table 1 and described in more detail below. Alternative values for the absolute isotopic ratios of reference materials, differing only modestly from those in Table 1, are presented in Table 2.5 of Sharp (2007) (a text freely available online), as well as Table 1 of the 1993 IAEA report on isotopic reference materials. For an exhaustive list of reference material, refer to Appendix I of Sharp (2007), Table 40.1 of Gröning (2004), or the website of the International Atomic Energy Agency. Note that the 13C/12C ratio of Vienna Pee Dee Belemnite (VPDB) and 34S/32S ratio of Vienna Canyon Diablo Troilite (VCDT) are purely mathematical constructs; neither material existed as a physical sample that could be measured.
=== Pharmacodynamics === The mechanism of action of tiflorex has apparently never been studied. Similar compounds such as fenfluramine, norfenfluramine and 4-MTA act as selective serotonin releasing agents and 5-HT2 receptor agonists. Fenfluramine in particular causes very similar side effects and appetite suppression at therapeutically relevant doses.
Sources: en.wikipedia.org
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.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
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.