Everything below concerns primary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-02-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 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.
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.
| 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. |
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
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.
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.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
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.
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.
Membrane-targeting domains associate specifically with head groups of their lipid ligands embedded into the membrane. These lipid ligands are present in different concentrations in distinct types of biological membranes (for example, PtdIns3P can be found mostly in membranes of early endosomes, PtdIns(3,5)P2 in late endosomes, and PtdIns4P in the Golgi). Hence, each domain is targeted to a specific membrane.
=== Signs === There are many different signs of dehydration in undernourished people. These can include sunken eyes; a very dry mouth; decreased urine output or dark urine; increased heart rate with decreasing blood pressure; and altered mental status.
Gene splicing techniques are being looked at to try to repair a genome with the erroneous gene that causes HD, using tools such as CRISPR/Cas9. PTC Therapeutics is evaluating small molecules that induce poison exon inclusion in HTT transcript as a therapeutic strategy to lower HTT expression. In 2025, researchers at University College London reported preliminary results from AMT-130, a phase 1/2 uniQure huntingtin-lowering gene therapy clinical trial, that showed a 75% slowing of disease progression over three years; the full study data has not yet been released peer-reviewed nor published. AMT-130 is a gene therapy utilising adeno-associated virus serotype 5 (AAV5) vector carrying an artificial micro-RNA to silence the gene leading to a lowering of huntingtin protein expression. The therapy is delivered directly into the deep brain structures of the caudate nucleus and putamen via an MRI guided neurosurgical procedure.
== External links == "Relaxin Family Peptide Receptors: RXFP4". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology. Archived from the original on 2016-03-03. Retrieved 2008-12-09.
Sources: en.wikipedia.org
These events caused widespread devastation, and even depopulated the north, resulting in the complete social and political breakdown and collapse of central authority in the Central Plains, triggering massive, sustained waves of Han Chinese migration into South China, leading to the formation of distinct Han lineages, who also likely assimilated the by-now partially sinicized Bai Yue in their midst. Modern Han Chinese subgroups, such as the Cantonese, the Hakka, the Henghua, the Hainanese, the Hoklo peoples, the Gan, the Xiang, the Wu-speaking peoples, all claim Han Chinese ancestry pointing to official histories and their own genealogical records to support such claims. Linguists hypothesize that proto- Wu and Min varieties of Chinese may have originated from the time of Jin, while the proto- Yue and Hakka varieties perhaps from the Tang and Song, about half-a-millennium later. The presence of Tai-Kradai substrates in these dialects may have been due to the assimilation of the remaining groups of Bai Yue, integrating these lands into the Sinosphere proper.
From 2011, new cars should have brake assist system in the EU, according to The Pedestrian Protection Regulation (EC) 78/2009. Starting in 2012, all cars under 10,000 lbs. sold in the US are required to have Electronic Stability Control. In 2014, ESP (Electronic Stability Program) and TPMS became mandatory in the European Union, with also the driver seat belt reminder and the ISOFIX system, under General Safety Regulation (EC) No 661/2009. In 2015, recognizing that safer roads are a shared responsibility, Together for Safer Roads (TSR) was formally launched to align the private sector's road safety efforts with the United Nations Decade of Action for Road Safety. In 2016 and 2017, ABS became mandatory on motorcycles in the EU. In 2018, eCall became mandatory in the EU, and reverse camera in the US. In 2019, the EU legislated to revise the General Safety Regulation (GSR), the revision includes the following automotive safety features:
== Experimental chemistry == Unambiguous determination of the chemical characteristics of roentgenium has yet to have been established due to the low yields of reactions that produce roentgenium isotopes. For chemical studies to be carried out on a transactinide, at least four atoms must be produced, the half-life of the isotope used must be at least 1 second, and the rate of production must be at least one atom per week. Even though the half-life of 282Rg, the most stable confirmed roentgenium isotope, is 100 seconds, long enough to perform chemical studies, another obstacle is the need to increase the rate of production of roentgenium isotopes and allow experiments to carry on for weeks or months so that statistically significant results can be obtained. Separation and detection must be carried out continuously to separate out the roentgenium isotopes and allow automated systems to experiment on the gas-phase and solution chemistry of roentgenium, as the yields for heavier elements are predicted to be smaller than those for lighter elements. However, the experimental chemistry of roentgenium has not received as much attention as that of the heavier elements from copernicium to livermorium, despite early interest in theoretical predictions due to relativistic effects on the ns subshell in group 11 reaching a maximum at roentgenium.
Deep learning uses several layers of neurons between the network's inputs and outputs. The multiple layers can progressively extract higher-level features from the raw input. For example, in image processing, lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits, letters, or faces. Deep learning has been used to improve the performance of programs in subfields of artificial intelligence including computer vision, speech recognition, natural language processing, image classification and others. Deep neural networks and backpropagation had been in development since 1950. Starting in 2012, the speed of deep learning was increased one hundred-fold by switching to GPUs, and there were enormous amounts of data available on the internet (called at the time "big data") as well as curated datasets used for benchmark testing, such as ImageNet. Usage of deep learning increased in 2012–2015 due to these improvements. In 2025, Geoffrey Hinton said that, until the 2010s, "We couldn't do anything very impressive because we didn’t have enough data and we didn't have enough computation."
==== Liberation of Czechoslovakia ==== On 8 May 1944, Beneš signed an agreement with Soviet leaders stipulating that "Czechoslovak territory liberated by Soviet armies" would be placed under Czechoslovak civilian control. On 21 September, Czechoslovak troops formed in the Soviet-liberated village, Kalinov, which was the first liberated settlement of Slovakia, located near the Dukla Pass in northeastern part of the country. Slovakia and the Czech lands were occupied mostly by Soviet troops (the Red Army), supported by Czech and Slovak resistance, from the east to the west; only southwestern Bohemia was liberated by other Allied troops from the west. Even at the end of the war, German troops massacred Czech civilians; the Massacre in Trhová Kamenice and the Massacre at Javoříčko are examples of this. A provisional Czechoslovak government was established by the Soviets in the eastern Slovak city of Košice on 4 April 1945. "National committees" (supervised by the Red Army) took over the administration of towns as the Germans were expelled. Bratislava was taken by the Soviets on 4 April. On April 18th, 1945, elements of the U.S. 90th Infantry Division of General George S. Patton’s U.S. 3rd Army crossed the western border of the former Czechoslovakia border near the town of Cheb, effectively cutting Germany in half. Elements of the 3rd Army would probe the Czech border for the rest of April, moving parallel down the border in an advance towards Linz, Austria.
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 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.