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 2026-01-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
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.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
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.
== Colors and materials == Conventional LEDs are made from a variety of inorganic semiconductor materials. The following table shows the available colors with wavelength range, voltage drop and material:
== United Kingdom == Below are the individuals appointed by Charles III in his right as King of the United Kingdom with honours within his own gift and with the advice of the Government for other honours.
=== Nigeria === In Nigeria, medical laboratory science is a high skilled profession charged by Act 11 of 2003 Laws of the Federation of Nigeria. The initial qualification awarded graduates of the programme, like some other medical programmes, was Associate of the Institute of Medical Laboratory Technology/Science (AIMLT/AIMLS). The Medical Laboratory Science Council of Nigeria, which was established by Act. 2004 Cap 114 Laws of the Federation of Nigeria, regulates the practice of medical laboratory science in Nigeria. In Nigeria, the Medical Laboratory Science programme is Bachelor of Medical Laboratory Science (BMLS), regulated by the National Universities Commission (NUC) and the Medical Laboratory Science Council of Nigeria (MLSCN). Students at their first year (100 level) are trained under the Faculty of Science in Basic Sciences and Faculty of Arts, Management and Social science in General studies and Entrepreneurship. At the 200 level, students are taught basic medical sciences and are introduced to Medical Laboratory Science. The third year of the programme marks the beginning of the professional training as students are engaged in the classroom for lectures as well as in the Hospital laboratory for the professional or practical training. At the fourth year, students are taught the basics in all the special areas of medical laboratory science. At the end of 400 level programme, successful students are presented for the first professional examination, to be moderated by the Medical Laboratory Science Council of Nigeria.
Sources: en.wikipedia.org
Insect-based pet food is pet food consisting of, or containing insects digestible by pets such as dogs or cats. A limited, but growing number of products are available on the market, including insect-based cat food, dog food, and pet treats. The process of consuming insects by animals (as well as humans) is called entomophagy.
However, owing to problems in administration and after several cases of unhealthiness, the Domino's Peruvian franchise closed in 2015, and reopened one year later with new owners. The master franchises for India, Nepal, and Sri Lanka are currently owned by the Indian company Jubilant FoodWorks. India is the largest international market for Domino's outside its home market, being the only country to have more than 1,000 Domino's outlets. With the first store opening in Delhi in 1996, the company operates 1,362 stores across 264 Indian cities as of 2018. In Bangladesh, the franchises for Domino's Pizza are co-owned by Jubilant FoodWorks and Golden Harvest Limited, forming 'Domino's Pizza Bangladesh Limited'. In this entity, Jubilant FoodWorks is the majority shareholder and owns 51% of the company, while the rest of the share is owned by Golden Harvest Limited. The first store in Bangladesh opened in February 2019. As of October 19 2017, Domino's Pizza opened in Naxxar Road Birkirkara, Malta. As of July 27, 2020, Domino's Pizza opened in downtown Zagreb, Croatia. As of 2020, Domino's Pizza opened 550 stores in Turkey. In Italy, Domino's declared bankruptcy closing all its stores. In Russia, DP Eurasia announced that they would be declaring bankruptcy for its Russian business and would be closing all of its locations in Russia, Turkey, Azerbaijan, and Georgia. The Russian network was bought by rapper Timati in August 2023. After the sale, it changed its name to Domиno Pizza.
Archival Resources Details Thorburn Brailsford Robertson: Repository: Commonwealth Scientific and Industrial Research Organisation (CSIRO) Corporate Records and Archives Strategies, The Encyclopedia of Australian Science and Innovation. Robertson, Thorburn Brailsford (1884–1930), The Encyclopedia of Australian Science and Innovation. Thorburn Brailsford Robertson, Adelaide Connect, University of Adelaide. Lehmann Jayne, "World Diabetes Day – Time to celebrate Adelaide’s link to 1922 insulin discovery", EdHealth Australia, 14 November 2016. Thorburn Brailsford Robertson, South Australian Medical Heritage Society. TROVE: "From the library of Thorburn Brailsford Robertson".
Sources: en.wikipedia.org
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.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
Karl Fischer titration is a common reference method that quantifies water by a chemical reaction. Thermogravimetric analysis can also estimate moisture by weight loss on heating. Method choice depends on sample size and whether other volatile substances are present.