Everything below concerns primary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-06-01. 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.
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 | 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 |
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.
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.
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.
The chain of reactions that generate reactive oxygen species (ROS) results in oxidative stress, which ultimately causes cell damage. Type II pathway of photodynamic reaction: After PS is excited into T1 state, the energy is transferred directly between PS and O2. This interaction transforms the oxygen molecules into a highly reactive form known as singlet oxygen. Singlet oxygen possesses potent oxidizing properties, making it extremely effective in reacting with and damaging cellular components. However, this reaction is selective; while most cellular components exist in a less reactive singlet state and remain unaffected, the singlet oxygen specifically targets and reacts with oxygen molecules in the cell cytoplasm. PDT is used to treat cancer across diverse types and sites. A unique feature of PDT is that photosensitizers tend to accumulate more selectively in cancer cells than in normal cells. The high affinity of photosensitizers to low-density lipoprotein (LDL) allows for selectivity. LDL acts as a carrier, allowing photosensitizers to travel into cancerous tissues. The interaction between photosensitizers and LDL makes it easier for therapeutic agents to reach the right places, which makes PDT more effective against cancer.
However, temperatures at Plateau Station were only recorded during the 37 months that it was active. Had a lower temperature than the Vostok record occurred there at a later date, it would never have been recorded. Monitoring stations in Antarctica are few and far between; prior to 1995, Vostok was the only research station on the Antarctic Plateau above the elevation of 3,000 m (with the exception of Plateau Station during the brief period that it was active in the 1960s), with no other stations for several hundred kilometers in any direction. Temperatures below −89.2 °C (−128.6 °F), if they did occur elsewhere, would not have been recorded. The automatic weather station at Dome A was only installed in 2005, and has recorded −82.5 °C (−116.5 °F) as the coldest so far (2010). However, a review of satellite measurements taken between 2010 and 2013 found several places located along a ridge between Dome A and Dome F which recorded even lower temperatures of −92 to −94 °C (−134 to −137 °F), with the lowest reliable temperature being −93.2 °C (−135.8 °F) recorded in 2010, at 81°48′S 59°18′E, at an elevation of 3,900 m (12,800 ft). The extreme low temperatures are found in hollows slightly below the peak of the ice ridge, where cold air gets trapped as it flows downhill, and since the same low temperature ranges were detected at several different sites along the ridge across multiple years, it is thought this may be the lowest temperature achievable under local atmospheric conditions.
R−S−S−R' + 2 GSH → R−SH + R'−SH + GSSG where R and R' are parts of the micro-nanogel structure, and GSSG is oxidized glutathione (glutathione disulfide). The breaking of disulfide bonds causes the nanogel to degrade into smaller fragments. This degradation process leads to the release of encapsulated drugs. The released drug molecules can then exert their therapeutic effects, such as inducing apoptosis in cancer cells.
== Main constituents == Sandalwood oil contains more than 90% sesquiterpenic alcohols of which 50–60% is the tricyclic α-santalol. β-Santalol comprises 20–25%. The composition of the oil will depend on the species, region grown, age of tree, and possibly the season of harvest and details of the extraction process used. Current International Organization for Standardization (ISO) standards for S. album oil are 41–55% α-santalol and 16–24% β–santalol (ISO 3518: 2002E).
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Sources: en.wikipedia.org
Lewis, Daniel. The Feathery Tribe: Robert Ridgway and the Modern Study of Birds. Yale University Press. [1]. Ornithologie (1773–1792) Francois Nicholas Martinet Digital Edition Smithsonian Digital Libraries "West Midland Bird Club: Older Organisations". Archived from the original on May 9, 2013. Retrieved May 23, 2004. History of ornithology in North America History of ornithology and ornithology collections in Victoria, Australia on Culture Victoria History of ornithology in China Hill ornithology collections Newton, Alfred; Mitchell, Peter Chalmers (1911). "Ornithology" . Encyclopædia Britannica. Vol. 20 (11th ed.). pp. 299–326.
=== Surgery === Weight loss surgery in those with obesity and type 2 diabetes is often an effective measure. Many are able to maintain normal blood sugar levels with little or no medications following surgery and long-term mortality is decreased. There is, however, a short-term mortality risk of less than 1% from the surgery. The body mass index cutoffs for when surgery is appropriate are not yet clear. It is recommended that this option be considered in those who are unable to get both their weight and blood sugar under control. A pancreas transplant is occasionally considered for people with type 1 diabetes who have severe complications of their disease, including end stage kidney disease requiring kidney transplantation. Diabetic peripheral neuropathy (DPN) affects 30% of all diabetes patients. When DPN is superimposed with nerve compression, DPN may be treatable with multiple nerve decompressions. The theory is that DPN predisposes peripheral nerves to compression at anatomical sites of narrowing, and that the majority of DPN symptoms are actually attributable to nerve compression, a treatable condition, rather than DPN itself. The surgery is associated with lower pain scores, higher two-point discrimination (a measure of sensory improvement), lower rate of ulcerations, fewer falls (in the case of lower extremity decompression), and fewer amputations.
For the second consecutive year, the AFL's opening round was spread across two weekends. Due to concern over one-sided matches, each of the top four teams from 2012 (Sydney, Hawthorn, Adelaide and Collingwood) played each of the bottom four teams (the Western Bulldogs, Melbourne, Gold Coast and Greater Western Sydney) only once each – except that Sydney played local rival Greater Western Sydney twice, and that the Western Bulldogs played Adelaide twice. None of the bottom five teams from 2012 (Western Bulldogs, Port Adelaide, Melbourne, Gold Coast and Greater Western Sydney) featured in a Friday night match during the home-and-away season. This is due to the AFL's policy of awarding Friday night matches only to teams that perform consistently throughout the season. This season was the last in which AFL football was played at AAMI Stadium, with both Adelaide and Port Adelaide moving to a redeveloped Adelaide Oval from the 2014 season. Match starting times are local.
== Medical uses == Diclofenac is used to treat pain related to arthritis, dysmenorrhea, rheumatic diseases and other inflammatory disorders, kidney stones and gallstones. An additional indication is the treatment of acute migraines. Diclofenac is used to treat mild to moderate postoperative or post-traumatic pain, in particular when inflammation is also present. Diclofenac ophthalmic is indicated for the treatment of postoperative inflammation in people who have undergone cataract extraction and for the temporary relief of pain and photophobia in people undergoing corneal refractive surgery. Diclofenac may also help with actinic keratosis and with acute pain caused by minor strains, sprains and contusions. In many countries, eye drops are sold to treat acute and chronic nonbacterial inflammation of the anterior part of the eyes (such as postoperative states). The eye drops have also been used to manage pain for traumatic corneal abrasion. Diclofenac is often used to treat chronic pain associated with cancer, especially if inflammation is present.
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.
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.