A practical reference on Sublimation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-12-09. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common names | Lyophilization; freeze-drying | Terms used interchangeably. |
| Phase change | Sublimation | Ice converts directly to vapor under vacuum. |
| Typical chamber pressure | 0.01–1 mbar | Below the triple point of water. |
| Primary drying product temperature | −40 to −10 °C | Kept below collapse or glass transition temperature. |
| Water content after drying | 0.5–3% w/w | Varies with formulation and cycle. |
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.
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.
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.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
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.
== Taxes == General sales tax Goods and services tax, the name for the value-added tax in several jurisdictions: Goods and services tax (Australia) Goods and services tax (Canada) Goods and services tax (Hong Kong) Goods and Services Tax (India) Goods and Services Tax (India) Bill Goods and Services Tax (India) Revenue Statistics Goods and Services Tax (Malaysia) Goods and Services Tax (New Zealand) Goods and Services Tax (Singapore) Generation-skipping transfer tax, in the United States
=== Personal struggles === Kidder received a diagnosis of bipolar disorder in 1988, which she rejected at the time, and refused the recommended lithium treatment. In 1990, while filming the pilot of a proposed television series Nancy Drew and Daughter, Kidder was in a car crash that injured her spine and left her partially paralyzed. She was unable to work for two years, resulting in debts over $800,000. Kidder attempted to sue the Canadian producer, Nelvana, for $1 million in damages, but did not receive a settlement, and launching the suit rendered her ineligible for Canadian workers' compensation. While convalescing, Kidder said she finally "was able to accept the diagnosis" (of bipolar disorder). She later spoke openly about treatment of her bipolar disorder via alternative medicine. In 1996, she experienced a manic episode in Los Angeles. At the time, Kidder had been working on an autobiography when her laptop computer became infected with a virus, which caused it to crash and her to lose three years' worth of drafts. Kidder flew to California to have the computer examined by a data-retrieval company that was unable to retrieve the lost files. This prompted her to enter a manic state and she disappeared for four days. She was later found by a homeowner in the backyard of a Glendale residence, and was taken by the Los Angeles Police Department to Olive View–UCLA Medical Center in a distressed state, the caps on her teeth having been knocked out during a rape attempt. She was subsequently placed in psychiatric care.
When we were getting very close to releasing Half-Life (less than a week or so), we found there were already some projects that we needed to start working on, but we couldn't risk checking in code to the shipping version of the game. At that point we forked off the code in VSS to be both /$Goldsrc and /$Src. Over the next few years, we used these terms internally as "Goldsource" and "Source". At least initially, the Goldsrc branch of code referred to the codebase that was currently released, and Src referred to the next set of more risky technology that we were working on. When it came down to show Half-Life 2 for the first time at E3, it was part of our internal communication to refer to the "Source" engine vs. the "Goldsource" engine, and the name stuck. Source was developed part-by-part from this fork onwards, slowly replacing GoldSrc in Valve's internal projects and, in part, explaining the reasons behind its unusually modular nature. Valve's development of Source since has been a mixture of licensed middleware and in-house-developed code. Older versions of Source use Bink Video for video playback, however more recent releases of the Source engine use WebM videos for menu backgrounds, Full Motion Videos, and splash screens. .
Sources: en.wikipedia.org
== Non-cytokine examples of macrophage-activating factors == Pathogenic antigens can bind to toll-like receptors that stimulate macrophage activation and response. Examples include heat shock proteins released during apoptosis, and bacterial lipopolysaccharide.
== Types == There are membrane-bound (type 1, guanylate cyclase-coupled receptor) and soluble (type 2, soluble guanylate cyclase) forms of guanylate cyclases. Membrane bound guanylate cyclases include an external ligand-binding domain (e.g., for peptide hormones such as BNP and ANP), a transmembrane domain, and an internal catalytic domain homologous to adenylyl cyclases. Recently, a directly light-gated guanylate cyclase has been discovered in an aquatic fungus. In the mammalian retina, two forms of guanylate cyclase have been identified, each encoded by separate genes; RETGC-1 and RETGC-2. RETGC-1 has been found to be expressed in higher levels in cones compared to rod cells. Studies have also shown that mutations in the RETGC-1 gene can lead to cone-rod dystrophy by disrupting the phototransduction processes.
=== November === 1 November - Resident Craig Dentith’s fury over ‘appalling’ state of unfinished Winsford estate https://www.northwichguardian.co.uk/news/23892480.residents-fury-appalling-state-unfinished-development/
Sources: en.wikipedia.org
== Screening == Because it can be difficult to measure weight-for-height Z scores (WHZ) frequently, screening is performed by physical exam, with careful examination of the child's feet to detect the presence of bilateral pitting edema. Screening for edema is essential for the diagnosis of kwashiorkor, since nearly two-thirds of kwashiorkor cases do not have evidence of acute wasting (i.e. mid-upper arm circumference (MUAC) < 125 mm, or WHZ < -2) when diagnosed with kwashiorkor.
== Further reading == Foreman, John C.; Johansen, Torben; Gibb, Alasdair J., eds. (2010). Textbook of Receptor Pharmacology. doi:10.1201/9781420052558. ISBN 978-0-429-14730-2. Brunton L (2011). Brunton LL, Chabner B, Knollmann BC (eds.). Goodman and Gilman's The Pharmacological Basis of Therapeutics (12 ed.). New York: McGraw-Hill. ISBN 978-0-07-162442-8. Whalen K (2014). Lippincott Illustrated Reviews: Pharmacology.
== Mutations and disease == Marilyn Kozak demonstrated, through systematic study of point mutations, that any mutations of a strong consensus sequence in the −3 position or to the +4 position resulted in highly impaired translation initiation both in vitro and in vivo.
=== Ethylene vinyl alcohol co-polymer in dimethyl sulfoxide === 8% ethylene vinyl alcohol co-polymer in dimethyl sulfoxide solution has been used. For FI it is marketed as Onyx34, and for gastroesophageal reflux disease it is marketed as Enteryx. After injection, it forms a spongy solid mass via solidification of the hydrophobic copolymer. This occurs because the co-polymer is hydrophic, and the solvent is dissolved away upon contact with tissues. In one publication inter-sphincteric injection site was used via the inter-sphincteric route.
Sources: en.wikipedia.org
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.
Reduced pressure lowers the boiling point of water and allows ice to sublime below its triple point. Without sufficient vacuum, melting or boiling may occur instead of sublimation, which can damage the product structure.
Heat and mass transfer limit drying once the ice front recedes. The dried layer insulates the frozen core and resists vapor flow, so increasing shelf temperature too quickly can cause collapse or meltback.
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.