The short version of Primary drying fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-02-06 and is reviewed periodically as new material appears.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
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.
| Property | Value | Notes |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
== Personal life == After raising their 6 children, James, Nancy, Betsy, Cathy, Laurie and Sally, his wife Elizabeth (Libby), a biologist by training, joined the Merrifield laboratory at Rockefeller University where she worked for over 23 years. After a long illness, R. Bruce Merrifield died on May 14, 2006, at the age of 84 in his home in Cresskill, New Jersey. At the time of his death he was survived by his wife Libby, their 6 children and 16 grandchildren. Libby died on September 13, 2017.
Another Tyrannosaurus, nicknamed Stan (NHMAD 2020.00001, formerly BHI 3033), in honor of amateur paleontologist Stan Sacrison, was recovered from the Hell Creek Formation in 1992. Stan is the second most complete skeleton found, with 199 bones recovered representing 70% of the total. This tyrannosaur also had many bone pathologies, including broken and healed ribs, a broken and healed neck, and a substantial hole in the back of its head, about the size of a Tyrannosaurus tooth. In 1998, 20-year-old Bucky Derflinger noticed a T. rex toe exposed above ground, making him the youngest person to discover a Tyrannosaurus. The specimen, dubbed Bucky in honor of its discoverer, was a young adult, 3.0 metres (10 ft) tall and 11 metres (35 ft) long. Bucky is the first Tyrannosaurus to be found that preserved a furcula (wishbone). Bucky is permanently displayed at The Children's Museum of Indianapolis.
Type V – Having the same clinical features as type IV, it can be clinically distinguished by observing a "mesh-like" appearance to a bone biopsy under a microscope. Type V can be further distinguished from other types of OI by the "V triad": an opaque band (visible on X-ray) adjacent to the growth plates; hypertrophic calluses (abnormally large masses of bony repair tissue) which form at fracture sites during the healing process; and calcification of the interosseous membrane of the forearm, which may make it difficult to turn the wrist. Other features of this condition may include pulled elbow, and, as in other types of OI, long bone bowing and hearing loss. Cases of this type are caused by mutations in the IFITM5 gene on chromosome 11p15.5. The separation of type V from type IV OI, its clinical type, was initially suggested even before its genetic cause was known, by Glorieux et al. in 2000. Type V is relatively common compared to other genetically defined types of OI—4% of OI patients at the genetics department of the Brazilian Hospital de Clínicas de Porto Alegre were found to have it. Type VI – With the same clinical features as type III, it is distinguished by bones which have an appearance similar to that seen in osteomalacia. Type VI is caused by a loss-of-function mutation in the SERPINF1 gene on chromosome 17p13.3. Type VII – OI caused by a mutation in the gene CRTAP on chromosome 3p22.3; clinically similar to OI types II and III, depending on affected individual.
Plutonium-244 is one of several extinct radionuclides that preceded the formation of the Solar System. Its half-life of 81.3 million years ensured its circulation across the Solar System before its extinction, and so evidence of it should also be found throughout the Solar System. Radionuclides such as 244Pu, decay to produce fissiogenic (i.e., arising from fission) xenon isotopes that can then be used to time the events of the early Solar System. In fact, by analyzing data from Earth's mantle which indicates that about 30% of existing fissiogenic xenon is from 244Pu decay, it can be inferred that the Earth formed nearly 50–70 million years after the Solar System formed. Before the analysis of mass spectroscopy data from analyzing samples found in meteorites, it was inferential at best to credit 244Pu as being the nuclide responsible for the fissiogenic xenon found. However, an analysis of a laboratory sample of 244Pu compared with that of fissiogenic xenon gathered from the meteorites Pasamonte and Kapoeta produced matching spectra that immediately left little doubt as to the source of the isotopic xenon anomalies. Spectra data was further acquired for another actinide isotope, 244Cm, but such data proved contradictory and helped erase further doubts that the fission was appropriately attributed to 244Pu. Both the examination of spectra data and study of fission tracks led to several findings of plutonium-244. In Western Australia, the analysis of the mass spectrum of xenon in 4.1–4.2-billion-year-old zircons was met with findings of diverse levels of 244Pu fission.
Production process – it can be derived from biotechnology or from other technologies. It may be prepared using more conventional techniques as is the case for blood or plasma-derived products and a number of vaccines. Active substance – consisting of entire microorganisms, mammalian cells, nucleic acids, proteinaceous, or polysaccharide components originating from a microbial, animal, human, or plant source. Mode of action – therapeutic and immunological medicinal products, gene transfer materials, or cell therapy materials.
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Oriented strand board is manufactured in wide mats from cross-oriented layers of thin, rectangular wooden strips compressed and bonded together with wax and synthetic resin adhesives. The adhesive resins types used include: urea-formaldehyde (OSB type 1, nonstructural, nonwaterproof); isocyanate-based glue (or PMDI poly-methylene diphenyl diisocyanate–based) in inner regions with melamine-urea-formaldehyde or phenol formaldehyde resin glues at surface (OSB type 2, structural, water resistant on face); phenol formaldehyde resin throughout (OSB types 3 and 4, structural, for use in damp and outside environments). The layers are created by shredding the wood into strips, which are sifted and then oriented on a belt or wire-mesh caul (a heated, ventilated support) and coated with the resin. The layers thus built up are transferred to a forming line and cross-oriented so that strips on the external layers are aligned to the panel's strength axis, while the internal layers are perpendicular. The number of layers placed is determined partly by the thickness of the panel, and is limited by the equipment used. Individual layers can also vary in thickness to give different finished panel thicknesses; typically, a 15 cm (5.9 in) layer will produce a 15 mm (0.59 in) panel thickness. The mat is placed in a thermal press to compress the flakes and bond them by heat activation and curing of the resin. Individual panels are then cut from the mats into finished sizes. Most of the world's OSB is made in the United States and Canada in large production facilities.
Chronic poisoning is long-term repeated or continuous exposure to a poison where symptoms do not occur immediately or after each exposure. The person gradually becomes ill, or becomes ill after a long latent period. Chronic poisoning most commonly occurs following exposure to poisons that bioaccumulate, or are biomagnified, such as mercury, gadolinium, and lead.
The city of Moscow is led by a single mayor, Sergey Sobyanin. The city is divided into 12 administrative okrugs and 125 districts. Moscow's urban planning appeared as early as the 12th century, when the city was founded. The city center grew by amalgamating with suburbs, in keeping with medieval principles of urban development, as strong fortress walls gradually spread along the circular streets of adjacent new settlements. The first circular defense walls established the trajectory for Moscow's rings, laying the groundwork for future city planning. The following fortifications served as the city's circular defense boundaries at some point in history:
=== Neurodevelopmental disorders === Astrocytes have emerged as important participants in various neurodevelopmental disorders. This view states that astrocyte dysfunction may result in improper neural circuitry, which underlies certain psychiatric disorders such as autism spectrum disorders and schizophrenia.
Sources: en.wikipedia.org
=== Antimicrobial surfaces === Antimicrobial surfaces are designed to either inhibit the ability of microorganisms to grow or damaging them by chemical (copper toxicity) or physical processes (micro/nano-pillars to rupture cell walls). These surfaces are especially important for the healthcare industry. Designing effective antimicrobial surfaces demands an in-depth understanding of the initial microbe-surface adhesion mechanisms. Molecular dynamics simulation and time-lapse imaging are typically used to investigate these mechanisms.
The ability of birds to return to precise locations across vast distances has been known for some time; in an experiment conducted in the 1950s, a Manx shearwater released in Boston in the United States returned to its colony in Skomer, in Wales within 13 days, a distance of 5,150 km (3,200 mi). Birds navigate during migration using a variety of methods. For diurnal migrants, the sun is used to navigate by day, and a stellar compass is used at night. Birds that use the sun compensate for the changing position of the sun during the day by the use of an internal clock. Orientation with the stellar compass depends on the position of the constellations surrounding Polaris. These are backed up in some species by their ability to sense the Earth's geomagnetism through specialised photoreceptors.
Draculin (named after Count Dracula) is a glycoprotein found in the saliva of vampire bats, Desmodus rotundus. It is a member of the lactotransferrin protein family. It is a single-chain polypeptide protein composed of 708 amino acids, weighing about 88.5 kDa when reduced and 83 kDa when non-reduced, and selectively inhibits FIXa and FXa. It functions as an anticoagulant, inhibiting coagulation factors IX (IXa) and X (Xa) by establishing rapid equilibrium with factor Xa, and is the first natural polypeptide which has been described to show immediate anti-IXa and anti-Xa properties. The rapid equilibrium achieved at comparable concentrations of FXa and Draculin, as well as the lack of any detectable lag phases in assays, supports the conclusion that Draculin is a tight-binding inhibitor. In addition, Draculin inhibits the conversion of prothrombin to thrombin, preventing fibrinogen from converting to fibrin. These two processes inhibit blood coagulation thus keeping the blood of the bitten victim from clotting while the bat is drinking. The activation of factor X is a common point between the intrinsic and extrinsic pathway of blood coagulation.
Headaches Enlargement of the hands, feet, nose, lips, and ears, and a general thickening of the skin Soft tissue swelling of internal organs, notably the heart with the attendant weakening of its muscularity, and the kidneys, also the vocal cords resulting in a characteristic thick, deep voice and slowing of speech Generalized expansion of the skull at the fontanelle Pronounced brow protrusion, often with ocular distension (frontal bossing) Pronounced lower jaw protrusion (prognathism) with attendant macroglossia (enlargement of the tongue) and teeth spacing Hypertrichosis, hyperpigmentation and hyperhidrosis Skin tags Carpal tunnel syndrome
=== Leaders of the Liberal Party === H. H. Asquith, 1st Earl of Oxford and Asquith, 1925 (1916–1926) Donald Maclean, Acting Leader (1919–1920) David Lloyd George (1926–1931) Sir Herbert Samuel (1931–1935) Sir Archibald Sinclair (1935–1945) Clement Davies (1945–1956) Jo Grimond (1956–1967) Jeremy Thorpe (1967–1976) Jo Grimond, Interim Leader (1976) David Steel (1976–1988)
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Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.