The short version of sublimation fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-02-09. Anything still debated is marked as such rather than presented as settled.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
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 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.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
=== Heart disease === Abdominal obesity is typically associated with a statistically higher risk of heart disease, hypertension, insulin resistance, and type 2 diabetes (see below). With an increase in the waist to hip ratio and overall waist circumference the risk of death increases as well. Metabolic syndrome is associated with abdominal obesity, blood lipid disorders, inflammation, insulin resistance, type 2 diabetes, and an increased risk of developing cardiovascular disease. It is now generally believed that intra-abdominal fat is the depot that conveys the biggest health risk. Recent validation has concluded that total and regional body volume estimates correlate positively and significantly with biomarkers of cardiovascular risk and that BVI calculations correlate significantly with all biomarkers of cardiovascular risk. Abdominal obesity is linked with higher cardiovascular events among South Asian ethnic populations.
The method was developed by botanist Mikhail Tsvet in 1901–1905 in the universities of Kazan and Warsaw. He developed the technique and coined the term chromatography in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll, carotenes, and xanthophylls. Since these components separate in bands of different colors (green, orange, and yellow, respectively) they directly inspired the name of the technique. New types of chromatography developed during the 1930s and 1940s made the technique useful for many separation processes. Chromatography technique developed substantially as a result of the work of Archer John Porter Martin and Richard Laurence Millington Synge during the 1940s and 1950s, for which they won the 1952 Nobel Prize in Chemistry. They established the principles and basic techniques of partition chromatography, and their work encouraged the rapid development of several chromatographic methods: paper chromatography, gas chromatography, and what would become known as high-performance liquid chromatography. Since then, the technology has advanced rapidly. Researchers found that the main principles of Tsvet's chromatography could be applied in many different ways, resulting in the different varieties of chromatography described below. Advances are continually improving the technical performance of chromatography, allowing the separation of increasingly similar molecules.
In molecular biology, the condensation domain is a protein domain found in many multi-domain enzymes which synthesise peptide antibiotics. This domain catalyses a condensation reaction to form peptide bonds in non-ribosomal peptide biosynthesis. It is usually found to the carboxy side of a phosphopantetheine binding domain (pp-binding). It has been shown that mutations in the HHXXXDG sequence motif in this domain abolish activity suggesting this is part of the active site.
=== Phase 1 === Etifoxine deuterated (deuterated etifoxine; GRX-917) – GABAA receptor positive allosteric modulator, translocator protein (TSPO) agonist, and nonbenzodiazepine/benzoxazine [12] KAR-2618 (GFB-887; TRPC4/5 inhibitor) – transient receptor potential TRPC4 and TRPC5 cation channel inhibitor [13] SNTX-2643 (SENS-01) – atypical serotonin reuptake inhibitor (SRI) (kanna-derived) [14] Transient receptor potential channel 4/5 inhibitor - Bristol-Myers Squibb – transient receptor potential TRPC4 and TRPC5 cation channel inhibitor [15]
=== Muscle and fat tissue === Microwave burns show some similarities with electrical burns, as the tissue damage is deep rather than superficial. Adipose tissue shows less degree of damage than muscles and other water-rich tissues. (In contrast, radiant heat, contact burns and chemical burns damage subcutaneous adipose tissue to higher extent than deeper muscle tissue.) Full-thickness biopsy of the area between burned and unburned skin shows layers of more and less damaged tissue (tissue sparing), layers of undamaged fat between damaged muscles; a pattern that is not present in conventional thermal or chemical burns. Cells subjected to electrical burns show microscopic nuclear streaming on histology examination; this feature is not present with microwave burns. Microwaves also deposit more energy to areas with low blood supply and to tissue interfaces. Hot spots may be formed in the tissue, with a consequent higher absorption of microwave energy and even higher temperature achieved, with localized necrosis of the affected tissue following. Sometimes, the affected tissue can even be charred. Muscle tissue destruction can lead to myoglobinuria, with renal failure following in severe cases; this is similar to burns from electric current. Urinalysis and serum CPK, BUN and creatine tests are used to check for this condition.
Sources: en.wikipedia.org
Coordinates were measured in grades on official French terrestrial ordnance charts from the French revolution well into the 20th century. 1 grade (or in modern symbology, 1 gon) = 0.9° or 0.01 right angle. One advantage of this measure is that the distance between latitude lines 0.01 gon apart at the equator is almost exactly 1 kilometre. It would be exactly 1 km if the original definition of 1 metre = 1⁄10,000 quarter-meridian had been adhered to. One disadvantage is that common angles like 30° and 60° are expressed by fractional values (33+1⁄3 and 66+2⁄3 respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex – degree – minute – second invented by Babylonian astronomers.
==== Michigan ==== In November 2017, the Michigan PFAS Action Response Team (MPART) was created to address growing pollution concerns after multiple sites contaminated by PFAS were identified. MPART is a multi-agency team tasked with investigating PFAS contamination sites and sources in the state, protecting drinking water, enhancing interagency communication and keeping the public informed. In January 2018, Michigan established a legally enforceable groundwater cleanup level of 70 ppt for both PFOA and PFOS. Two science advisory committees were also created and joined MPART to "coordinate and review medical and environmental health, PFAS science and develop evidence-based recommendations". In August 2020, the Michigan Department of Environment, Great Lakes, and Energy adopted stricter drinking water standards in the form of MCLs, lowering acceptable levels from the 2018 enforceable groundwater cleanup levels of 70 ppt to 8 ppt for PFOA and 16 ppt for PFOS and adding MCLs for 5 previously unregulated PFAS compounds PFNA, PFHxA, PFHxS, PFBS, and HFPO-DA.
=== Genomes === Genomic DNA is tightly and orderly packed in the process called DNA condensation, to fit the small available volumes of the cell. In eukaryotes, DNA is located in the cell nucleus, with small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid. The functional genetic information in a genome is located in genes, regulatory sequences, origins of replication, centromeres, telomeres, and segments required for the three-dimensional structure of chromatin. In many complex eukaryotes, only a small fraction of the total sequence is devoted to the various functional elements. For example, in humans less than 10% of the genome has a defined functional role and the rest (90%) is probably junk DNA. (See also [Non-coding DNA].)
Allied technological cooperation during World War II List of aircraft of the United Kingdom in World War II List of aircraft of World War II List of fighter aircraft List of military aircraft of the United States
Sources: en.wikipedia.org
== Antidepressant research == Two meta-analyses of preliminary clinical trials evaluating the efficacy of St. John's wort for treating mild-to-moderate depression indicated a response similar to selective serotonin reuptake inhibitors and with better tolerance, although the long-term generalization of study results was limited by the short duration (4–12 weeks) of reviewed studies.
Blue Shift does not elaborate on the storyline in Opposing Force, the preceding expansion pack, and no enemy characters or weapons introduced in it appear in the game. The player is instead given access to a limited selection of Half-Life's original weaponry.
==== Migration patterns ==== HIC can be useful in tracking animal migration. Animals with metabolically inert tissue (e.g. feathers or hair) synthesize that tissue using hydrogen from source water and food, but ideally do not incorporate subsequent water during migration. Because δD varies geographically, the difference between animal tissue δD and post-migration water δD, after accounting for the biological fractionation of assimilation, can provide information regarding animal movement. In monarch butterflies, for example, wing chitin is metabolically inert after it is built, so it can reflect the isotopic composition of the environmental water at the time and location of wing growth. This then creates a record of butterfly origin and can be used to determine migration distance. This approach can also be used in bats and birds, using hair and feathers, respectively. Since rainwater becomes depleted as elevation increases, this method can also track altitudinal migration. However, this is technically hard to do, and the resolution seems to be too poor to track small altitudinal changes. 2H is most useful in tracking movement of species between areas with large continental water variation, since species movement can be complicated by the similarity of local water δD between places. For example, source water from Baja California may have the same δD as water from Maine. Further, a proportion of the HIC in the tissue can exchange with water and complicate the interpretation of measurements.
Sources: en.wikipedia.org
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
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.