If you have been reading about sublimation 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.
Updated 2025-11-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
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 is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid that can be reconstituted later.
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.
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.
== Early life and military service == Jerome Kalman Sherman was born in 1925 in Brooklyn, New York, to Murray and Beatrice Sherman, a sailmaker and Navy Yard worker. After graduating from Erasmus Hall High School early, he enrolled at Brooklyn College at the age of 16, but after three semesters put his studies on hold to enlist in the military during World War II. At age 17, in 1943, Sherman joined the U.S. Navy as a seaman and earned a commission at Notre Dame. He then served in the Pacific Theater as an anti-submarine officer until 1945, learning of the Japanese surrender on his 20th birthday. Subsequently he served in occupied Japan as part of the first naval line officer to enter Nagasaki, left the Navy as a lieutenant commander.
== Axonal degeneration == Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration (AAD), which is rapid separation of the proximal (the part nearer the cell body) and distal ends within 30 minutes of injury. After separation, dystrophic bulb structures form at both terminals and the transected membranes are sealed. A brief latency phase occurs in the distal segment during which it remains electrically excitable and structurally intact. Degeneration follows with swelling of the axolemma, and eventually the formation of bead-like axonal spheroids. The process takes roughly 24 hours in the PNS, and longer in the CNS. The signaling pathways leading to axolemma degeneration are currently poorly understood. However, research has shown that this AAD process is calcium–independent. Granular disintegration of the axonal cytoskeleton and inner organelles occurs after axolemma degradation. Early changes include accumulation of mitochondria in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The depolymerization of microtubules occurs and is soon followed by degradation of the neurofilaments and other cytoskeleton components. The disintegration is dependent on ubiquitin and calpain proteases (caused by influx of calcium ion), suggesting that axonal degeneration is an active process and not a passive one as previously misunderstood. Thus the axon undergoes complete fragmentation.
transcription unit The segment of DNA between the initiation site and the termination site of transcription, containing the coding sequences for one or more genes. All genes within a transcription unit are transcribed together into a single transcript during a single transcription event; the resulting polycistronic RNA may subsequently be cleaved into separate RNAs, or may be translated as a unit and then cleaved into separate polypeptides.
For the second consecutive year, Zverev and Team Germany failed to progress at the United Cup. At the 2026 Australian Open, Zverev progressed to his third consecutive semifinal, defeating Cameron Norrie, Francisco Cerúndolo, and Learner Tien en route. In a rematch of their quarterfinal match in 2024, Zverev lost to eventual champion Carlos Alcaraz in a five-set epic semifinal lasting five hours and 27 minutes, ranking as the third longest match in Australian Open history. During the semifinal, Zverev dropped the first two sets, but rebounded to win the next two in consecutive tiebreaks to push the match to a deciding set, the first deciding set of the men's tournament on Rod Laver Arena. In the fifth set, Zverev had an opportunity to serve for the match, but was broken twice to lose the match. Failing to defend his finalist points from 2025, he dropped to world No. 4 in the rankings, behind Novak Djokovic. In Acapulco, Zverev lost in the second round of singles to Miomir Kecmanovic. However, in doubles, partnered with Marcelo Melo, the pair took the doubles title, defeating Alexander Erler & Robert Galloway in the final. Zverev then made consecutive Masters 1000 semifinals at Indian Wells, Miami, and Monte-Carlo, improving significantly on his results from the previous year. By reaching his first Indian Wells semifinal, he completed the semifinal set of all nine Masters 1000 tournaments, the first person outside of the Big Four to do so.
==== In Ukraine ==== Similarly to the events in imperial Cossack hosts, a revival of Cossack self-organization also took place in Ukraine, inspired by the traditions of the Zaporozhian Sich and Cossack Hetmanate. In April 1917 a congress in Zvenyhorodka, Kyiv Governorate, established Free Cossacks as a volunteer militia in order "to defend the liberties of the Ukrainian people" and maintain civil order. The revived Cossack structure in Ukraine was organized according to the territorial principle, with villages providing companies of volunteers, which were grouped into a kurin (battalion) on the volost level, subordinate to a regiment led by polkovnyk, which was itself part of a kish (division) led by an Ottoman. All officers of Free Cossacks were elected, and funds were provided from taxation. Most volunteers of the organization were peasants, but industrial workers did also enlist themselves, especially in cities. During 1917 the Free Cossack movement spread around Kyiv, Volhynia, Kherson, Poltava and Chernihiv governorates. At the All-Ukrainian Congress of Free Cossacks in Chyhyryn on 16–20 October 1917 Pavlo Skoropadskyi was elected otaman of the movement.
Sources: en.wikipedia.org
=== Xenobiotics === Numerous drugs can raise GGT levels, including phenobarbitone and phenytoin. GGT elevation has also been occasionally reported following nonsteroidal anti-inflammatory drugs (including aspirin), St. John's wort and kava.
Drugs under prescription control are sent to pharmacies in multi-packs of unit packs or in bottles containing many hundreds of capsules. Typically a pharmacist prepares the final form of the unit pack or places a lower count of capsules in a small bottle for the customer. In a pharmacy, pharmacists are available to answer questions and to ensure that proper documentation is provided. Internet pharmacies mail the prescribed drugs to the customer; boxes or mailing envelopes are used. Child resistant packaging is often required on the unit packs; if requested, a pharmacist is allowed to put drugs in a bottle with easy-open features. Over-the-counter drugs are sold in independent or chain pharmacies, grocery stores, and diverse retail outlets. Usually the package needs to have all the usage information available. Packages often need to have tamper resistant features and child-resistant packaging. Usually the packaging and labeling of dietary supplements, homeopathic products, and folk medicines are not regulated. Some producers voluntarily follow the regulations for over-the-counter drugs or regional Pharmacopoeias.
Chemical synthesis, either from petrochemical starting materials or from natural products extracts. Biotechnology, specifically biocatalysis (enzymatic methods) and biosynthesis (fermentation) for small molecules, and cell culture technology for big molecules. Extraction from animals, microorganisms, or plants; for example, isolation and purification is used for alkaloids, antibacterials (especially penicillins), and steroids. Hydrolysis of proteins, especially when combined with ion exchange chromatography, used, for instance, for amino acids. Chemical synthesis and biotechnology are most frequently used, sometimes in combination.
== Complications == One review of 23 publications involved a total of 889 patients reported an overall rate of complications of 18%. Reported complications are mostly minor, and include: bleeding, perianal pain / discomfort (which may rarely be persistent), leakage of injected material, infection / abscess (which rarely may require drainage), mucosal erosion, obstructed defecation, hypersensitivity reaction, hematoma, diarrhea, pruritus ani, dermatitis, and bowel urgency (sudden strong urge to defecate).
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.