This is a working overview of secondary drying, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
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 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.
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.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
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.
There are several different mating systems among teleosts. Some species are promiscuous, where both males and females breed with multiple partners and there are no obvious mate choices. This has been recorded in Baltic herring, Guppies, Nassau groupers, humbug damselfish, cichlids and creole wrasses. Polygamy, where one sex has multiple partners can come in many forms. Polyandry consists of one adult female breeding with multiple males, which only breed with that female. This is rare among teleosts, and fish in general, but is found in the clownfish. In addition, it may also exist to an extent among anglerfish, where some females have more than one male attached to them. Polygyny, where one male breeds with multiple females, is much more common. This is recorded in Sculpins, sunfish, darters, damselfish and cichlids where multiple females may visit a territorial male that guards and takes care of eggs and young. Polygyny may also involve a male guarding a harem of several females. This occurs in coral reef species, such as damselfishes, wrasses, parrotfishes, surgeonfishes, triggerfishes and tilefishes. Lek breeding, where males congregate to display to females, has been recorded in at least one species Cyrtocara eucinostomus. Lek-like breeding systems have also been recorded in several other species. In monogamous species, males and females may form pair bonds and breed exclusively with their partners. This occurs in North American freshwater catfishes, many butterflyfishes, sea horses and several other species.
In 1995, Ice-T had a recurring role as vengeful drug dealer Danny Cort on the television series New York Undercover, co-created by Dick Wolf. His work on the series earned him the 1996 NAACP Image Award for Outstanding Supporting Actor in a Drama Series. In 1997, he co-created the short-lived series Players, produced by Wolf. This was followed by a role as pimp Seymour "Kingston" Stockton in Exiled: A Law & Order Movie (1998). These collaborations led Wolf to add Ice-T to the cast of Law & Order: Special Victims Unit. Since 2000, he has portrayed Odafin "Fin" Tutuola, a former undercover narcotics officer transferred to the Special Victims Unit. In 2002, the NAACP awarded Ice-T with a second Image Award, again for Outstanding Supporting Actor in a Drama Series, for his work on Law & Order: SVU. Around 1995, Ice-T co-presented a UK-produced magazine television series on black culture, Baadasss TV. In 1997, Ice-T had a pay-per-view special titled Ice-T's Extreme Babes which appeared on Action PPV, formerly owned by BET Networks. In 1999, Ice-T starred in the HBO film Stealth Fighter as a United States Naval Aviator who fakes his own death, steals an F-117 stealth fighter, and threatens to destroy United States military bases. He also acted in the film Sonic Impact, released the same year. Ice-T made an appearance on the comedy television series Chappelle's Show as himself presenting the award for "Player Hater of the Year" at the "Player-Haters Ball", a parody of his own appearance at the Players Ball. He was dubbed the "Original Player Hater".
=== May 2003 === In separate incidents, the Royal Military Police declared that Radhi Natna died of a heart attack while in British custody, yet his family reports that he had no heart trouble; and the Black Watch regiment arrested the 17-year-old Ahmad Jabber Kareem Ali in Basra, who then drowned after being ordered to swim across a river despite not being able to swim, according to his friend Ayad Salim Hanoon. Army Reservists abused Prisoners at Camp Bucca, and were later court-martialed. Brigadier General Ennis Whitehead III reported that Master Sergeant Lisa Marie Girman, a state trooper, "repeatedly kick[ed a prisoner] in the groin, abdomen and head, and encouraging her subordinate soldiers to do the same," Lieutenant Colonel Vic Harris reported that Staff Sergeant Scott A. McKenzie who worked at a Pennsylvania Department of Corrections boot-camp-style prison, and Specialist Timothy F. Canjar: held prisoners' legs, encouraged others to then kick them in the groin, stepped on their previously injured arms, and made false sworn statements to the Army Criminal Investigation Division. They received "general under honorable conditions" discharges, were ordered to forfeit two months' salary, and returned to the United States. Sergeant Shawna Edmondson, also involved in the case, received an "other-than-honorable" discharge, after she requested it instead of being court-martialed. Hossam Shaltout said the abuse at Camp Bucca was similar to that at Abu Ghraib prisoner abuse, and that his torture included scorpions placed on his body.
Sources: en.wikipedia.org
ALK-negative ALCL tumor cells show products made by chimeric genes: DUSP22-IRF4 (many of which are fused at particular site and termed DUSP22-FRA7H) in 30% of the cases; TP63-TBL1XR1 in 8% of cases; and NFKB2-ROS1, NCOR2-ROS1, NFKB2-TYK2, or PABPC4-TYK2 in rare cases. They also show mutations in the JAK1 and/or STAT3 genes in 18% of cases; the MSC gene in 15% of cases, and the NOTCH1 gene in 15% of cases. About 24% of cases have a truncated ERBB4 gene. DUSP22 gene rearrangements have been associated with favorable outcomes in ALK-negative ALCL while TP63 gene arrangements are often associated with a poorer prognosis in various cancers. ALK-negative ALCL cells overexpress overactive STAT3 in 47% of cases and JAK1 in many cases. Many of these gene abnormalities appear to contribute to the development of ALK-negative ALCL.
There was initial resistance to these results on the part of Ernst Antevs, the palaeobotanist who had worked on the Scandinavian varve series, but his objections were eventually discounted by other geologists. In the 1990s samples were tested with AMS, yielding (uncalibrated) dates ranging from 11,640 BP to 11,800 BP, both with a standard error of 160 years. Subsequently, a sample from the fossil forest was used in an interlaboratory test, with results provided by over 70 laboratories. These tests produced a median age of 11,788 ± 8 BP (2σ confidence) which when calibrated gives a date range of 13,730 to 13,550 cal BP. The Two Creeks radiocarbon dates are now regarded as a key result in developing the modern understanding of North American glaciation at the end of the Pleistocene.
==== Electrolyte recycling ==== Electrolyte recycling consists of two phases. The collection phase extracts the electrolyte from the spent Li-ion battery. This can be achieved through mechanical processes, distillation, freezing, solvent extraction, and supercritical fluid extraction. Due to the volatility, flammability, and sensitivity of the electrolyte, the collection process poses a greater difficulty than the collection process for other components of a Li-ion battery. The next phase consists of separation/electrolyte regeneration. Separation consists of isolating the individual components of the electrolyte. This approach is often used for the direct recovery of the Li salts from the organic solvents. In contrast, regeneration of the electrolyte aims to preserve the electrolyte composition by removing impurities which can be achieved through filtration methods. The recycling of the electrolytes, which consists 10–15 wt.% of the Li-ion battery, provides both economic and environmental benefits. These benefits include the recovery of the valuable Li-based salts and the prevention of hazardous compounds, such as volatile organic compounds (VOCs) and carcinogens, being released into the environment. Compared to electrode recycling, less focus is placed on recycling the electrolyte of Li-ion batteries due to lower economic benefits and greater process challenges.
Sources: en.wikipedia.org
The T-cell receptor (TCR) is a protein complex, located on the surface of T cells (also called T lymphocytes). They are responsible for recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules. The binding between TCR and antigen peptides is of relatively low affinity and is biologically degenerate (that is, many TCRs recognize the same antigen peptide, and many antigen peptides are recognized by the same TCR). The TCR is composed of two different protein chains (that is, it is a heterodimer). In humans, in 95% of T cells the TCR consists of an alpha (α) chain and a beta (β) chain (encoded by TRA and TRB, respectively), whereas in 5% of T cells the TCR consists of gamma and delta (γ/δ) chains (encoded by TRG and TRD, respectively). This ratio changes during ontogeny and in diseased states (such as leukemia). It also differs between species. Orthologues of the 4 loci have been mapped in various species. Each locus can produce a variety of polypeptides with both constant and variable regions. When the TCR engages with antigenic peptide and MHC (peptide/MHC), the T lymphocyte is activated through signal transduction (that is, a series of biochemical events mediated by associated enzymes, co-receptors, specialized adaptor molecules, and activated or released transcription factors). Based on the initial receptor-triggering mechanism, the TCR is classified as belonging to the family of non-catalytic tyrosine-phosphorylated receptors (NTRs).
== Arthropathies and related disorders (710–719) == 710 Diffuse diseases of connective tissue 710.0 Systemic lupus erythematosus 710.2 Sjögren's syndrome 710.3 Dermatomyositis 710.4 Polymyositis 710.5 Eosinophilia myalgia syndrome 710.9 Connective tissue disease, unspec. 711 Arthropathy associated with infections 712 Crystal arthropathies 712.1 Chondrocalcinosis due to dicalcium phosphate crystals 712.2 Chondrocalcinosis due to pyrophosphate crystals 712.3 Chondrocalcinosis, cause unspecified pseudogout 712.8 Other specified crystal arthropathies 712.9 Unspecified crystal arthropathy 713 Arthropathy, endocrine disorders 713.1 Arthropathy, gastrointestinal conditions 714 Rheumatoid arthritis and other inflammatory polyarthropathies 714.0 Rheumatoid arthritis 714.3 Polyarticular juvenile rheumatoid arthritis 715 Osteoarthrosis and allied disorders 715.09 Osteoarthrosis, generalized, multiple sites 715.11 Osteoarthrosis, shoulder 715.14 Osteoarthrosis, hand 715.15 Osteoarthrosis, hip 715.16 Osteoarthrosis, knee 715.17 Osteoarthrosis, ankle/foot 715.9 Osteoarthrosis, unspec. 716 Other and unspecified arthropathies 716.1 Arthropathy, traumatic, unspec. 716.9 Arthropathy, unspec. 717 Internal derangement of knee 717.1 Derangement of anterior horn of medial meniscus 717.42 Derangement of lateral meniscus 717.7 Chondromalacia of patella 717.9 Derangement, internal, knee, unspec.
== Applications == Also known as cyclotetramethylene-tetranitramine, tetrahexamine tetranitramine, or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, HMX was first made in 1930. In 1949 it was discovered that HMX can be prepared by nitrolysis of RDX. Nitrolysis of RDX is performed by dissolving RDX in a 55% HNO3 solution, followed by placing the solution on a steambath for about six hours. HMX is used almost exclusively in military applications, including as the detonator in nuclear weapons, in the form of polymer-bonded explosive, and as a solid-rocket propellant. HMX is used in melt-castable explosives when mixed with TNT, which as a class are referred to as "octols". Additionally, polymer-bonded explosive compositions containing HMX are used in the manufacture of missile warheads and armor-piercing shaped charges. HMX is also used in the process of perforating the steel casing in oil and gas wells. The HMX is built into a shaped charge that is detonated within the wellbore to punch a hole through the steel casing and surrounding cement out into the hydrocarbon-bearing formations. The pathway that is created allows formation fluids to flow into the wellbore and onward to the surface. The Hayabusa2 space probe used HMX to excavate a hole in an asteroid in order to access material that had not been exposed to the solar wind. Ongoing research aims to reduce its sensitivity and improve some manufacturing properties.
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.