sublimation 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 2026-03-16. 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.
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.
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.
| 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. |
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.
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.
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Officials involved in the hepatitis B vaccination programs say that in many of China's poverty-stricken rural areas, children are delivered at home in remote mountain villages or nomadic herders' tents, far from hospitals and access to medical information. The Chinese Center for Disease Control and Prevention (China CDC) have conducted research that supports the evidence that "there was and is still a huge bottleneck to ensure the delivery of the timely birth dosage to home births". Another problem is the growing size of China's migrant labor force or "floating population." Farmers or peasants who become urban laborers move frequently around the country and often do not seek medical attention. The immunization rate among them remains low, said China CDC. One major problem facing Chinese people infected with hepatitis B is that illegal blood testing is required by most employers in China. Anyone that tests positive for hepatitis B is either denied employment or fired. Laws do exist to protect the privacy of employees and job seekers but they are not enforced.
The drug has been implicated in the deaths of people from all walks of life—from homeless individuals to professionals—including teens and young parents. Because of the rising deaths across the country, especially in British Columbia where 1,716 deaths were reported in 2020 and 1,782 from January to October 2021, Health Canada is putting a rush on a review of the prescription-only status of naloxone in an effort to combat overdoses of the drug. In 2018, Global News reported allegations that diplomatic tensions between Canada and China hindered cooperation to seize imports, with Beijing being accused of inaction. Fentanyl has been discovered for sale in illicit markets in Australia in 2017 and in New Zealand in 2018. In response, New Zealand experts called for wider availability of naloxone. In May 2019, China regulated the entire class of fentanyl-type drugs and two fentanyl precursors. Nevertheless, it remains the principal origin of fentanyl in the United States: Mexican cartels source fentanyl precursors from Chinese suppliers such as Yuancheng Group, which are finished in Mexico and smuggled to the United States.In the past several months before February 2025, China began scheduling fentanyl precursors that are internationally banned.
Sources: en.wikipedia.org
=== Tumour mediation === Fibroblasts, like tumor-associated host fibroblasts (TAF), play a crucial role in immune regulation through TAF-derived ECM components and modulators. TAF are known to be significant in the inflammatory response as well as immune suppression in tumors. TAF-derived ECM components cause alterations in ECM composition and initiate the ECM remodeling. ECM remodeling is described as changes in the ECM as a result of enzyme activity which can lead to degradation of the ECM. Immune regulation of tumors is largely determined by ECM remodeling because the ECM is responsible for regulating a variety of functions, such as proliferation, differentiation, and morphogenesis of vital organs. In many tumor types, especially those related to the epithelial cells, ECM remodeling is common. Examples of TAF-derived ECM components include Tenascin and Thrombospondin-1 (TSP-1), which can be found in sites of chronic inflammation and carcinomas, respectively. Immune regulation of tumors can also occur through the TAF-derived modulators. Although these modulators may sound similar to the TAF-derived ECM components, they differ in the sense that they are responsible for the variation and turnover of the ECM. Cleaved ECM molecules can play a critical role in immune regulation. Proteases like matrix metalloproteinases and the uPA system are known to cleave the ECM. These proteases are derived from fibroblasts.
=== Dental care === ACE-inhibitors like lisinopril are considered to be generally safe for people undergoing routine dental care, though the use of lisinopril prior to dental surgery is more controversial, with some dentists recommending discontinuation the morning of the procedure. People may present to dental care suspicious of an infected tooth, but the swelling around the mouth may be due to lisinopril-induced angioedema, prompting emergency and medical referral.
It is descriptive rather than prescriptive. Bias and unfairness may go undetected because the developers are overwhelmingly white and male: among AI engineers, about 4% are black and 20% are women. There are various conflicting definitions and mathematical models of fairness. These notions depend on ethical assumptions, and are influenced by beliefs about society. One broad category is distributive fairness, which focuses on the outcomes, often identifying groups and seeking to compensate for statistical disparities. Representational fairness tries to ensure that AI systems do not reinforce negative stereotypes or render certain groups invisible. Procedural fairness focuses on the decision process rather than the outcome. The most relevant notions of fairness may depend on the context, notably the type of AI application and the stakeholders. The subjectivity in the notions of bias and fairness makes it difficult for companies to operationalise them. Having access to sensitive attributes such as race or gender is also considered by many AI ethicists to be necessary in order to compensate for biases, but it may conflict with anti-discrimination laws. At the 2022 ACM Conference on Fairness, Accountability, and Transparency a paper reported that a CLIP‑based (Contrastive Language-Image Pre-training) robotic system reproduced harmful gender‑ and race‑linked stereotypes in a simulated manipulation task.
Sources: en.wikipedia.org
Clostripain (EC 3.4.22.8, clostridiopeptidase B, clostridium histolyticum proteinase B, alpha-clostridipain, clostridiopeptidase, Endoproteinase Arg-C) is a cysteine protease that cleaves proteins on the carboxyl peptide bond of arginine. It was isolated from Clostridium histolyticum. The isoelectric point of the enzyme is 4.8-4.9 (at 8 °C), and optimum pH is 7.4~7.8 (against α-benzoyl-arginine ethyl ester). The composition of the enzyme is indicated to be of two chains of relative molecular mass 45,000 and 12,500.
In one of the largest studies on regional body mass, bears in British Columbia averaged 73.7 kg (162 lb) in 89 females and 103.1 kg (227 lb) in 243 males. In Yellowstone National Park, a study found that adult males averaged 119 kg (262 lb) and adult females averaged 67 kg (148 lb). Black bears in north-central Minnesota averaged 70 kg (150 lb) in 163 females and 125 kg (276 lb) in 77 males. In New York, the males average 136 kg (300 lb) and females 72.6 kg (160 lb). It was found in Nevada and the Lake Tahoe region that bears closer to urban regions were significantly heavier than their arid-country dwelling counterparts, with males near urban areas averaging 138 kg (304 lb) against wild-land males which averaged 115.5 kg (255 lb) whereas peri-urban females averaged 97.9 kg (216 lb) against the average of 65.2 kg (144 lb) in wild-land ones. In Waterton Lakes National Park, Alberta, adults averaged 125 to 128 kg (276 to 282 lb). The biggest wild American black bear ever recorded was a male from New Brunswick, shot in November 1972, that weighed 409 kg (902 lb) after it had been dressed, meaning it weighed an estimated 500 kg (1,100 lb) in life and measured 2.41 m (7 ft 11 in) long. Another notably outsized wild American black bear, weighing in at 408 kg (899 lb), was the cattle-killer shot in December 1921 on the Moqui Reservation in Arizona. The record-sized American black bear from New Jersey was shot in Morris County December 2011 and scaled 376.5 kg (830 lb). The Pennsylvania state record weighed 399 kg (880 lb) and was shot in November 2010 in Pike County.
== Career == Burnham is a professor of Pathology and Immunology, Molecular Microbiology, Pediatrics and Medicine at Washington University. She is the medical director for the clinical microbiology laboratory at Barnes-Jewish Hospital and the program director for the CPEP fellowship at Washington University.
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.
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.