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 2026-05-09. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
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, 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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | freeze-drying, lyophilisation, cryodesiccation | Lyophilization is common in pharmaceutical literature. |
| Typical chamber pressure during primary drying | 0.05–0.5 mbar (5–50 Pa) | Must remain below the triple point of water. |
| Typical shelf temperature during freezing | −40 to −20 °C | Lower temperatures may be used for eutectic systems. |
| Typical residual moisture after secondary drying | 0.5–3% w/w | Product-dependent; low moisture improves stability but can cause over-drying. |
| Typical analytical method for residual moisture | Karl Fischer titration or loss on drying | Thermogravimetric methods are also used. |
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.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
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.
The structure of chitin was determined by Albert Hofmann in 1929. Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia. Chitin is a modified polysaccharide that contains nitrogen; it is synthesized from units of N-acetyl-D-glucosamine (to be precise, 2-(acetylamino)-2-deoxy-D-glucose). These units form covalent β-(1→4)-linkages (like the linkages between glucose units forming cellulose). Therefore, chitin may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength. In its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. In most arthropods, however, it is often modified, occurring largely as a component of composite materials, such as in sclerotin, a tanned proteinaceous matrix, which forms much of the exoskeleton of insects. Combined with calcium carbonate, as in the shells of crustaceans and molluscs, chitin produces a much stronger composite. This composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the flexible body wall of a caterpillar (mainly chitin) to the stiff, light elytron of a beetle (containing a large proportion of sclerotin).
A coroner's inquest into the deaths of Lancashire couple John and Susan Cooper, who died while on holiday in Egypt in August 2018, concludes their deaths occurred as a result of carbon monoxide poisoning brought about by the use of a substance containing dichloromethane to kill bed bugs in an adjoining hotel room. 13 November – Police confirm that three children are among five members of the same family to have been killed in a house fire in London the previous day. A sixth person subsequently dies in hospital a few days later. 14 November – Around 400 are evacuated from Barton House, the oldest tower block in Bristol, after a survey carried out by Bristol City Council identified structural and fire safety concerns with the building. 16 November – The Department for Education asks the exams regulator, Ofqual, to extend extra support for GCSE students in England for another year as a way to help against the impact of COVID-19 on students taking examinations. Convicted murderer Ron Evans, 82, also known as the Clifton Rapist, is sentenced to four years in prison after he was earlier convicted of sexually assaulting a woman he met at a community centre. Cumbria Police confirm that a 16-year-old boy arrested in connection with the felling of the Sycamore Gap tree will face no further action. Two 12-year-old boys are charged with the murder of 19-year-old Shawn Seesahai, who was fatally stabbed in Wolverhampton three days earlier.
In March 1916 (BR.23–BR.26), Robertson announced the results of a series of experiments that he and his assistant, Louis Adolph Ray, had conducted with the white mice — chosen as his "experimental animal" because of their "hardiness, rapid growth, smallness, and fecundity" (BR.23, p.366) — wherein the oral administration of tethelin, a "growth-controlling principle" (which they later described as "the ether-precipitable fraction of an alcoholic extract of the anterior lobe of the pituitary body"), produced precisely "the same effects on their growth" as those "which [had] accompan[ied] the [oral] administration of the whole tissue of the anterior lobe of the pituitary body" to his control group (BR.25, p.397). As Everitt (AE.2, p.63) notes — having distinguished (p.66) Robertson and Ray's "growth controlling principle" of the pituitary (BR.35) from Moon, et al.'s "growth stimulating principle" (HM.2) — it was not until the (1921) work of Herbert Evans and Joseph Long (HE.1; HE.2) that "[it was] conclusively proved that the pituitary contained a growth-stimulating hormone". Evans and Long also discovered that, whilst the oral administration of their "pituitary principle" had no effect, administration per medium of an intraperitoneal injection was effective: which led them to the conclusion that whatever the pituitary's 'active principle' might be, it was "digested in the alimentary canal".
It is particularly concerning as those consequences happen while the brain is still developing. The degree to which the sleep is disturbed and fragmented has been significantly linked to the severity of the consequences, the latter having the possibility to decrease once the sleep is improved. It is more the disruption of sleep processes than the total amount of sleep the child experience that generates the adverse consequences on the child's daytime functioning; it contributes to the hyperactivity for example. Children with OSA may experience learning and memory deficits, and OSA has been linked to lowered childhood IQ scores. Untreated OSA may prevent children from reaching their height potential.
Sources: en.wikipedia.org
Cerebras Systems Inc., headquartered in Sunnyvale, California, develops semiconductors, supercomputers, and related software to power artificial intelligence deep-learning applications such as inference engines. Products include its wafer scale engine (WSE)-3 semiconductors, its CS-3 supercomputers, and its "AI inference cloud" and "AI training cloud" APIs, which allow users to access the company's computing power without buying its hardware. The company also builds data centers using its processors and supercomputers to provide cloud computing services directly to clients. Measuring 215 mm (8.5 in) squared, the company's WSE-3 semiconductors are currently the largest AI semiconductors ever built. They take up entire silicon wafers and use wafer-scale integration and switched fabric. This reduces latency and interconnect bottlenecks compared to GPU clusters. They use static random-access memory, as opposed to dynamic random-access memory. Cerebras semiconductors and computer systems are much more powerful than those of competitors; however, they have disadvantages due to their large size, 25kW power draw, and cost of as much as $3 million per node. The company has 4 major customers: the Mohamed bin Zayed University of Artificial Intelligence (62% of 2025 revenues), G42 (24% of 2025 revenues), OpenAI (signed in 2026), and Amazon Web Services (signed in 2026). Cerebras has offices in Sunnyvale, San Diego, Toronto, and Bangalore, India. Its semiconductors are manufactured by TSMC, currently the only company that has the ability to manufacture Cerebras chips.
Isobutyryl-coenzyme A is a necessary cofactor required for Polyketide synthase (PKS) enzyme(s), to catalyze the a,b-dehydrogenation of acyl-CoA esters to make many natural products via Polyketide synthase (PKS) assembly lines, as well as PKS-NRPS hybrid assembly lines. The resulting products comprise antibiotics and other bioactive molecules. Notably, isobutyryl-coenzyme A is also an intermediate in the metabolism of the amino acid valine, and it is structurally similar to intermediates in the catabolism of other small amino acids. Defective Isobutyryl-coenzyme A, produced by the body, often results in a metabolic disease.
1993/1977) County Court (Pensions Ombudsman) (Enforcement of Directions and Determinations) Rules 1993 (S.I. 1993/1978) Education (School Inspection) (Wales) (No. 2) Regulations 1993 (S.I. 1993/1982) Education (National Curriculum) (Assessment Arrangements for the Core Subjects) (Key Stage 1) Order 1993 (S.I. 1993/1983) Education (National Curriculum) (Assessment Arrangements for the Core Subjects) (Key Stage 3) Order 1993 (S.I. 1993/1984) Social Security (Industrial Injuries) (Prescribed Diseases) Amendment (No. 2) Regulations 1993 (S.I. 1993/1985) Education (School Inspection) (No. 2) Regulations 1993 (S.I. 1993/1986) Education (Further Education in Schools) Regulations 1993 (S.I. 1993/1987) A27 Trunk Road (Polegate Bypass Slip Roads) Order 1993 (S.I. 1993/1990) A27 Trunk Road (Polegate Bypass De-Trunking)Order 1993 (S.I. 1993/1991) A259 Trunk Road Brookland Diversion Order 1993 (S.I. 1993/1992) Education (Further Education Institutions Information) (England) Regulations 1993 (S.I. 1993/1993) Merchant Shipping (Load Lines) Act 1967 (Unregistered Ships) Order 1993 (S.I. 1993/1994) Poultry Breeding Flocks, Hatcheries and Processed Animal Protein (Fees) Order 1993 (S.I. 1993/1998)
3/8 S8 + 6 OH− → 2 S2− + SO2−3 + 3 H2O Adding back 6 Ca2+ cations from hydrated lime for the sake of electroneutrality, one obtains the overall reaction. This last reaction is consistent with the overall lime sulfur reaction mentioned in the USDA document. However, it does not account for all the details, such as the production of thiosulfate and sulfate among the end products of the reaction. Nevertheless, it is a good first-order approximation, and it usefully highlights the overall lime sulfur reaction scheme because the chemistry of reduced or partially oxidized forms of sulfur is particularly complex, and all the intermediate steps or involved mechanisms are hard to unravel. Moreover, once exposed to atmospheric oxygen and microbial activity, the lime sulfur system will undergo a rapid oxidation, and its different products will continue to evolve and eventually enter the natural sulfur cycle. The presence of thiosulfate in the lime sulfur reaction can be accounted for by the reaction between sulfite and elemental sulfur (or with sulfide and polysulfides), and that of sulfate by the complete oxidation of sulfite or thiosulfate, following a more complex reaction scheme. More information on calcium thiosulfate production is described in a patent by Hajjatie et al. (2006). Hajjatie et al. (2006) expressed the lime sulfur reaction in various ways depending on the degree of polymerization of calcium polysulfides, but the following reaction is probably the simplest of their series:
=== First complete genomic nucleotide sequence === The 3569-nucleotide sequence of all of the genes of the RNA bacteriophage MS2 was determined by a large team of researchers over several years, and was reported in a series of scientific papers. These results enabled the analysis of the first complete genome, albeit an extremely tiny one by modern standards. Several surprising features were identified, including genes that partially overlap one another and the first clues that different organisms might have slightly different codon usage patterns.
Sources: en.wikipedia.org
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.
Reduced pressure keeps the process below the triple point of water, so ice can sublimate directly to vapor. It also lowers the temperature needed for drying, which helps preserve heat-sensitive materials. Without vacuum, melting or boiling could occur instead of controlled sublimation.
The rate depends on heat transfer to the product and mass transfer of vapor through the dried layer. A cold condenser, adequate vacuum, and suitable shelf temperature all influence speed. Formulation properties such as solid content and collapse temperature also set practical limits.
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.