glass transition is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Analytical methods for lyophilized solids must account for the low moisture content and the fragile cake. Karl Fischer titration is widely used for water content, while near-infrared spectroscopy can measure moisture non-destructively in sealed containers. X-ray diffraction and modulated differential scanning calorimetry help identify crystalline or amorphous phases. Residual solvent analysis may be needed if organic solvents were used during formulation. The combination of these methods supports batch release and long-term stability assessment.
Lyophilized products are typically stored as sealed solids in vials or syringes. Moisture ingress is a major concern because many dried cakes are hygroscopic and can lose stability when exposed to humid air. Storage temperature depends on the formulation; some products are kept refrigerated, while others are stable at room temperature. Container closure integrity and headspace moisture are often monitored. Light protection may also be required for some photosensitive materials.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
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.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
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 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.
Handling and storage practices aim to keep the cake intact and dry. Vials are typically stored upright at controlled temperatures, often between 2 °C and 8 °C or at -20 °C for longer-term use. Reconstitution involves adding a suitable diluent and gently mixing until the solid dissolves. Shaking or rapid injection of diluent can create foam or damage sensitive molecules. Once reconstituted, the product may require refrigeration and use within a defined period.
Residual moisture is a key quality attribute for lyophilized products. Water that remains after secondary drying can affect chemical stability, cake structure, and shelf life. Karl Fischer titration is a common method for measuring water content in the dried solid. The target range varies by product, but many biologics are dried to between 0.5% and 3% water by weight. Acceptable limits are set during development and confirmed by stability studies.
Stability studies examine how temperature, humidity, and time influence a lyophilized product. Accelerated conditions provide early information about degradation pathways, while long-term studies support shelf-life claims. The glass transition temperature of the dried formulation can indicate its physical stability, and storage above this temperature may increase molecular mobility and lead to collapse or aggregation. Container closure integrity also matters because moisture or oxygen ingress can degrade the product, so vial stoppers and seals are part of the quality system.
The creation of British Nationality (Overseas) status, for instance, (with fewer privileges than British citizen status) was met with criticism from many Hong Kong residents who felt that British citizenship would have been more appropriate in light of the "moral debt" owed to them by the UK. Some British politicians and magazines also criticised the creation of BN(O) status. In 2020, the British government under Boris Johnson announced a program under which BN(O)s would have leave to remain in the UK with rights to work and study for five years, after which they may apply for settled status. They would then be eligible for full citizenship after holding settled status for 12 months. This was implemented as the eponymously named "British National (Overseas) visa", a residence permit that BN(O)s and their dependent family members have been able to apply for since 31 January 2021. BN(O)s and their dependents who arrived in the UK before the new immigration route became available were granted "Leave Outside the Rules" at the discretion of the Border Force to remain in the country for up to six months as a temporary measure. In effect, this retroactively granted BN(O)s a path to right of abode in the United Kingdom. Despite the COVID-19 pandemic, about 7,000 people had entered the UK under this scheme between July 2020 and January 2021.
nonsynonymous mutation Also nonsynonymous substitution or replacement mutation. A type of mutation in which the substitution of one nucleotide base for another results, after transcription and translation, in an amino acid sequence that is different from that produced by the original unmutated gene. Because nonsynonymous mutations always result in a biological change in the organism, they are often subject to strong selection pressure. Contrast synonymous mutation.
== Occurrence == The most abundant polyphenols are the condensed tannins, found in virtually all families of plants. Larger polyphenols are often concentrated in leaf tissue, the epidermis, bark layers, flowers and fruits but also play important roles in the decomposition of forest litter, and nutrient cycles in forest ecology. Absolute concentrations of total phenols in plant tissues differ widely depending on the literature source, type of polyphenols and assay; they are in the range of 1–25% total natural phenols and polyphenols, calculated with reference to the dry green leaf mass. Polyphenols are also found in animals. In arthropods, such as insects, and crustaceans polyphenols play a role in epicuticle hardening (sclerotization). The hardening of the cuticle is due to the presence of a polyphenol oxidase. In crustaceans, there is a second oxidase activity leading to cuticle pigmentation. There is apparently no polyphenol tanning occurring in arachnids cuticle.
Russian-installed officials in Crimea claimed that a missile attack caused explosions and fires in Sevastopol, adding that air defenses shot down 10 ATACMS missiles over the Black Sea and near Belbek Air Base. Other reports indicated that some missiles struck dropping cluster munitions on the airfield, destroying at least two Russian ground-based air defense systems, two MiG-31s and a fuel farm. An Su-27 was also damaged. Two drones struck an oil refinery in Proletarsky District, Rostov Oblast, Russia, causing explosions according to the local governor. However no fire was started and there were no casualties. The Russian Defence Ministry claimed to have intercepted various drones, rockets and missiles fired at Belgorod Oblast, which injured two people. Drones were downed over Kursk and Bryansk Oblasts as well as in Tatarstan. Two railway workers were killed by Russian shelling of railway infrastructure in Dnipropetrovsk Oblast. One person was killed by shelling in Sumy Oblast.
In Hong Kong, the accrediting body is Hong Kong Accreditation Service (HKAS). On 16 February 2004, HKAS launched its medical testing accreditation programme. In Canada, laboratory accreditation is not mandatory, but is becoming more and more popular. Accreditation Canada (AC) is the national reference. Different provincial oversight bodies mandate laboratories in EQA participations like LSPQ (Quebec), IQMH (Ontario) for example.
Sources: en.wikipedia.org
=== Detection in urine === Researchers found that humans who smoked 580 μg of the pure drug had urine salvinorin A concentrations of 2.4–10.9 μg/L during the first hour; the levels fell below the detection limit by 1.5 hours after smoking.
=== Alcohol dependence === Nalmefene is used in the European Union to reduce alcohol dependence and NICE recommends the use of nalmefene to reduce alcohol consumption in combination with psychological support for people who drink heavily. Based on a meta analysis, the usefulness of nalmefene for alcohol dependence is unclear. Nalmefene, in combination with psychosocial management, may decrease the amount of alcohol drunk by people who are alcohol dependent. The medication may also be taken "as needed", when a person feels the urge to consume alcohol.
== Intentional == Intentional weight loss is the loss of total body mass as a result of efforts to improve fitness and health, or to change appearance through slimming. Weight loss is the main treatment for obesity, and there is substantial evidence this can prevent progression from prediabetes to type 2 diabetes with a 7–10% weight loss and manage cardiometabolic health for diabetic people with a 5–15% weight loss. Weight loss in individuals who are overweight or obese can reduce health risks, increase fitness, and may delay the onset of diabetes. It could reduce pain and increase movement in people with osteoarthritis of the knee. Weight loss can lead to a reduction in hypertension (high blood pressure), however whether this reduces hypertension-related harm is unclear. Weight loss is achieved by adopting a lifestyle in which fewer calories are consumed than are expended. Depression, stress or boredom may contribute to unwanted weight gain or loss depending on the individual, and in these cases, individuals are advised to seek medical help. A 2010 study found that dieters who got a full night's sleep lost more than twice as much fat as sleep-deprived dieters. Though hypothesized that supplementation of vitamin D may help, studies do not support this. The majority of dieters regain weight over the long term. According to the UK National Health Service and the Dietary Guidelines for Americans, those who achieve and manage a healthy weight do so most successfully by being careful to consume just enough calories to meet their needs, and being physically active.
EDOT is often prepared from C4 precursors such as butanediol and butadiene via routes that produce the thiophene and dioxane rings in separate steps. Representative is the reaction of 2,3-butanedione, trimethyl orthoformate, and ethylene glycol to form the dioxane. Sulfidization with elemental sulfur gives the bicyclic target. EDOT is converted into the conducting polymer PEDOT by oxidation. The mechanism for this conversion begins with production of the radical cation [EDOT]+, which attacks a neutral EDOT molecule followed by deprotonation. Further similar steps result in the dehydropolymerization. The idealized conversion using peroxydisulfate is shown
Sources: en.wikipedia.org
== Society == Mass Party, a political party in Thailand (2006–2009?) Mass society, a society based on relations between huge numbers of people, whose prototypical denizen is the "mass man" Mass politics, politics in the mass society, featuring especially the modern political party
== Research and development == In the 1970s, chemists at Dr. Karl Thomae GmbH, a subsidiary of Boehringer-Ingelheim in Germany, synthesized a variety of enol carboxamides with the aim of obtaining active ingredients with anti-inflammatory or antithrombotic properties. A compound belonging to the oxicams (UH-AC 62, meloxicam) stood out, exhibiting antiinflammatory activity in the pharmacological adjuvant arthritis model, but only low antithrombotic efficacy as measured by platelet aggregation. Dr. Karl Thomae GmbH filed the German basic patent DE2756113 (1979) and Boehringer Ingelheim US patent 4,233,299 (1980) and patents in many other countries.
== Commercial and clinical products == The clearest commercial example is the SERI Surgical Scaffold, a knitted mesh of highly purified silk fibroin that originated in research at Tufts University and was first marketed by Serica Technologies. The U.S. Food and Drug Administration cleared it in 2009 as a temporary scaffold for the support and reinforcement of soft tissue; the product was subsequently held by Allergan and then by Sofregen Medical. After implantation the mesh provides immediate mechanical support and is gradually resorbed and replaced by the patient's own collagen. Silk sutures remain in widespread clinical use, and other silk-based products and devices are in development or early clinical testing.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
Most lyophilized products are stored in sealed containers at controlled temperature and humidity. Some require refrigeration, while others are stable at room temperature. Protection from light and moisture is often necessary.