Everything below concerns Sublimation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-07-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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.
| 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 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.
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.
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 removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
Recombinant DNA technology arose as a result of advances in biology that began in the 1950s and '60s. During these decades, a tradition of merging the structural, biochemical, and informational approaches to the central problems of classical genetics became more apparent. Two main underlying concepts of this tradition were that genes consisted of DNA and that DNA encoded information that determined the processes of replication and protein synthesis. These concepts were embodied in the model of DNA produced through the combined efforts of James Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins. Further research on the Watson-Crick model yielded theoretical advances that were reflected in new capacities to manipulate DNA. One of these capacities was recombinant DNA technology.
Membrane interaction of alpha-synuclein modulates or affects its rate of aggregation. The membrane-mediated modulation of aggregation is very similar to that observed for other amyloid proteins such as IAPP and abeta. Aggregated states of alpha-synuclein permeate the membrane of lipid vesicles. They are formed upon interaction with peroxidation-prone polyunsaturated fatty acids (PUFA) but not with monounsaturated fatty acids and the binding of lipid autoxidation-promoting transition metals such as iron or copper provokes oligomerization of alpha-synuclein. The aggregated alpha-synuclein has a specific activity for peroxidized lipids and induces lipid autoxidation in PUFA-rich membranes of both neurons and astrocytes, decreasing resistance to apoptosis. Lipid autoxidation is inhibited if the cells are pre-incubated with isotope-reinforced PUFAs (D-PUFA).
Afucosylated monoclonal antibodies are monoclonal antibodies engineered so that the oligosaccharides in the Fc region of the antibody do not have any fucose sugar units. When antibodies are afucosylated, antibody-dependent cellular cytotoxicity (ADCC) is increased. Most approved monoclonal antibodies are of the IgG1 isotype, where two N-linked biantennary complex-type oligosaccharides are bound to the Fc region. The Fc region exercises the effector function of ADCC through its interaction with leukocyte receptors of the FcγR family. ADCC is important in the efficacy of cancer antibodies, but with many approved cancer antibodies there is less ADCC than could be desired due to nonspecific IgG competing with the drugs for binding to FcγIIIa on natural killer cells. Afucosylated monoclonal antibodies overcome this problem through improved FcγIIIa binding.
Alexander Butlerov Institute of Chemistry trains students for school chemical Olympiads of the Republic of Tatarstan and the Russian Federation. At various times, professors of the Institute of Chemistry headed Russian teams at International School Chemistry Olympiad among them were Andrey N. Vedernikov, Arkady I. Kuramshin and Igor A. Sedov; The old building of the Alexander Butlerov Institute of Chemistry since it was built in 1953, was not only a laboratory building of chemical faculty of Kazan University, at different times, it also placed historical-philological faculty of Kazan University, military department, some rooms were used as a hostel for young teachers and graduate students of the University.
A safety modification to Mark 39 Mod 2 weapons known as Alt 197 had been approved in January 1960, but not yet applied to all deployed weapons prior to the Goldsboro accident, and was not applied to the weapons involved in the accident. Alt 197 replaced the MC-772 Arm/Safe switch with the MC-1288 Arm/Safe switch, with the main change being that the latter would prevent the charging of the low-voltage thermal battery when the Arm/Safe switch was in the "Safe" position, and as such would make sure that no electrical current was available anywhere within the bomb to power additional switches or hardware, legitimately or not. After the accident, all other Mark 39 Mod 2 weapons without the modification were taken off of deployment status ("red-lined") until the modification could be applied to the remaining inventory of the weapons.
Sources: en.wikipedia.org
Other automotive engineers include those listed below: Aerodynamics engineers will often give guidance to the styling studio so that the shapes they design are aerodynamic, as well as attractive. Body engineers will also let the studio know if it is feasible to make the panels for their designs. Change control engineers make sure that all of the design and manufacturing changes that occur are organized, managed and implemented... NVH engineers perform sound and vibration testing to prevent loud cabin noises, detectable vibrations, and/or improve the sound quality while the vehicle is on the road.
For decades, the public viewed the house as the "Birthplace of Insulin," and many individuals expressed their desire to have it turned into a shrine or monument to honour the Canadian hero. It was first internationally referred to with the title "Birthplace of Insulin," in 1923, by the Detroit Free Press. After 47 years, the house received official recognition in 1970, in the form of a plaque for the house, awarded by the London Public Library Board. In 1981, the London & District Branch of the Canadian Diabetes Association purchased the house, and began to use it as an office; they hoped to eventually restore the house, and turn it into a museum. Through various grants and fundraising efforts, by 1984, the museum was operational.
The exact size of the GPCR superfamily is unknown, but at least 831 different human genes (or about 4% of the entire protein-coding genome) have been predicted to code for them from genome sequence analysis. Although numerous classification schemes have been proposed, the superfamily was classically divided into three main classes (A, B, and C) with no detectable shared sequence homology between classes. The largest class by far is class A, which accounts for nearly 85% of the GPCR genes. Of class A GPCRs, over half of these are predicted to encode olfactory receptors, while the remaining receptors are liganded by known endogenous compounds or are classified as orphan receptors. Despite the lack of sequence homology between classes, all GPCRs have a common structure and mechanism of signal transduction. The very large rhodopsin A group has been further subdivided into 19 subgroups (A1-A19). According to the classical A-F system, GPCRs can be grouped into six classes based on sequence homology and functional similarity:
The intense research for development of efficient chiral selectors has resulted in the synthesis of over 1400 CSPs and over 200 CSPs have been commercialized and available in the market. The most commonly employed chiral selectors are categorized and presented in the table. It is surprising to note that In 1980, there was no single chiral stationary phase available in the market for performing chiral chromatography. However, In late 1980s the subject of enantioselective chromatography attracted growing interest, particularly under the drive of the institution of Okamoto in Japan, the teams of Pirkle, and Armstrong in the US, Schurig and König in Germany, Lindner in Austria, and Francotte in Switzerland . The Polysaccharides, amylose and cellulose, form the most abundant chiral polymers on earth. These naturally occurring polysaccharides form basis for an important class of chiral selectors.
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.
Primary drying removes ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, often under the same vacuum. The two stages differ in the water state being removed.