If you have been reading about Primary drying and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-04-23. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 |
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
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.
== Plant protein research == The first biochemist to enter the field was Karl Heinrich Ritthausen, a student of Justus von Liebig. Thomas Burr Osborne continued what Ritthausen started and published The Vegetable Proteins in 1909. Thus Yale University was the early center of protein nutrition, where William Cumming Rose was a student. Osborne also worked to determine the essentials, and later led the Biochemistry Department at the University of Chicago. When Ritthausen died in 1912, Osborne praised his efforts in biochemistry:
A Palestinian exodus from Kuwait took place during and after the Gulf War. During the Gulf War, more than 200,000 Palestinians fled Kuwait during the Iraqi occupation of Kuwait due to harassment and intimidation by Iraqi security forces, in addition to getting fired from work by Iraqi authority figures in Kuwait. After the Gulf War, the Kuwaiti authorities forcibly pressured nearly 200,000 Palestinians to leave Kuwait in 1991. Kuwait's policy, which led to this exodus, was a response to alignment of Palestinian leader Yasser Arafat and the PLO with Saddam Hussein. The Palestinians who fled Kuwait were Jordanian citizens. In 2013, 280,000 Jordanian citizens of Palestinian origin lived in Kuwait. In 2012, 80,000 Palestinians (without Jordanian citizenship) lived in Kuwait. Saudi Arabia expelled Yemeni workers after Yemen supported Saddam during the Gulf War.
== Distribution and migration == The cabbage looper can be found across North America and Eurasia, as far south as Florida and as far north as British Columbia. Cabbage looper populations in North America migrate from Mexico to Canada, depending on the seasons. It generally overwinters in Mexico or southern California, where temperatures are above 16 °C (61 °F) even during winter. It used to be frequently found in Florida, but this has lessened due to fewer cabbage crops. As northern regions of North America grow warmer, the cabbage looper gradually moves upward, only migrating if the region is above 16 °C (61 °F). During summer, it is less commonly found in southern regions, due to high temperatures. Similar to the monarch butterfly, populations presumably migrate in groups, as there is little genetic difference between source and migrating populations. Similar seasonal distributions were found in Europe. There, the cabbage looper can be found from England to southeastern Europe.
With the ability to form porous glasses as platelets, membrane technology is another important area of application. Hyper filtration of sea – and brackish water and ultra filtration in "downstream process" are but two. Additionally, they are often appropriate as a carrier for catalysts. For example, the olefin – metathesis was realized on the system metal – metal oxide/porous glass. Porous glasses can be used as membrane reactors as well, again because of their high mechanical, thermal and chemical stability. Membrane reactors can improve conversion of limited balance reactions, while one reaction product is removed by a selective membrane. For example, in the decomposition of hydrogen sulfide on a catalyst in a glass capillary, the conversion by reaction was higher with glass capillary than without.
== Role in disease == Activation of prothrombin is crucial in physiological and pathological coagulation. Various rare diseases involving prothrombin have been described (e.g., hypoprothrombinemia). Anti-prothrombin antibodies in autoimmune disease may be a factor in the formation of the lupus anticoagulant (also known as antiphospholipid syndrome). Hyperprothrombinemia can be caused by the G20210A mutation. Thrombin, a potent vasoconstrictor and mitogen, is implicated as a major factor in vasospasm following subarachnoid hemorrhage. Blood from a ruptured cerebral aneurysm clots around a cerebral artery, releasing thrombin. This can induce an acute and prolonged narrowing of the blood vessel, potentially resulting in cerebral ischemia and infarction (stroke). Beyond its key role in the dynamic process of thrombus formation, thrombin has a pronounced pro-inflammatory character, which may influence the onset and progression of atherosclerosis. Acting via its specific cell membrane receptors (protease activated receptors: PAR-1, PAR-3 and PAR-4), which are abundantly expressed in all arterial vessel wall constituents, thrombin has the potential to exert pro-atherogenic actions such as inflammation, leukocyte recruitment into the atherosclerotic plaque, enhanced oxidative stress, migration and proliferation of vascular smooth muscle cells, apoptosis and angiogenesis. Thrombin is implicated in the physiology of blood clots. Its presence indicates the existence of a clot. In 2013 a system for detecting the presence of thrombin was developed in mice.
Sources: en.wikipedia.org
He also initiated the President's Emergency Plan for AIDS Relief, in 2003, to address the global AIDS epidemic. The September 11 attacks during 2001 decisively reshaped his administration, resulting in the start of the war on terror and the creation of the Department of Homeland Security. Bush ordered the invasion of Afghanistan in an effort to overthrow the Taliban, destroy al-Qaeda, and capture Osama bin Laden. He signed the Patriot Act, expanding surveillance powers for suspected terrorists. He also ordered the 2003 invasion of Iraq to overthrow Saddam Hussein's regime, citing claims that it possessed weapons of mass destruction and had ties with al-Qaeda. Bush later signed the Medicare Modernization Act, which created Medicare Part D. In 2004, Bush was re-elected president in a close race, beating Democratic opponent John Kerry and winning the popular vote. During his second term, Bush negotiated various free trade agreements, appointed John Roberts and Samuel Alito to the Supreme Court, and sought major changes to Social Security and immigration laws, both of which ultimately failed in Congress. He was widely criticized for his administration's handling of Hurricane Katrina and revelations of torture against detainees at Abu Ghraib prison in Iraq. Amid his unpopularity, the Democrats regained control of Congress in the 2006 elections. In January 2007, Bush launched a surge of troops in Iraq.
=== Mechanism of action === Avasimibe is a potent activator of the pregnane X receptor and, consequently, an indirect inducer of CYP3A4 and P-glycoprotein, as well as a potent inhibitor of several cytochrome P450 isoenzymes, including CYP1A2, CYP2C9, and CYP2C19; its spectrum of CYP induction and inhibition is similar to that of rifampicin.
FSL constructs, when in solution (saline) and in contact, will spontaneously incorporate into cell and virus membranes. The methodology involves simply preparing a solution of FSL constructs in the range of 1–1000 μg/mL. The actual concentration will depend on the construct and the quantity of construct required in the membrane. One part of FSL solution is added to one part of cells (up to 100% suspension) and they are incubated at a set temperature within the range of 4–37 °C (39–99 °F) depending on temperature compatibility of the cells being modified. The higher the temperature, the faster the rate of FSL insertion into the membrane. For red blood cells, at 37 °C incubation for 2 hours achieves >95% insertion with at least 50% insertion being achieved within 20 minutes. In general, FSL insertion time of 4 hours at room temperature or 20 hours at 4 °C gives results similar to 1 hour at 37 °C for carbohydrate based FSLs inserting into red blood cells. The resultant kodecytes or kodevirions do not required to be washed, however this option should be considered if an excess of FSL construct is used in the koding process.
It entails a loss of fuel-efficiency as well as power by converting the output of the diesel engine into electricity. While both generators and electric motors are known to be very efficient, their efficiency nevertheless falls short of 100 percent. It requires an additional component in the form of a dedicated generator. Since the electric motor is always used to drive the propeller it can no longer step in to take on generator service as well. It does not allow the diesel engine and the electrical motor to join forces by simultaneously driving the propeller mechanically for maximum speed when the submarine is surfaced or snorkeling. This may, however, be of little practical importance inasmuch as the option it prevents is one that would leave the submarine at a risk of having to dive with its batteries at least partly depleted. The reason why diesel–electric transmission has become the dominant alternative in spite of these disadvantages is of course that it also comes with many advantages and that, on balance, these have eventually been found to be more important. The advantages include the following:
Sources: en.wikipedia.org
In acidic solutions, the neptunium(III) to neptunium(VII) ions exist as Np3+, Np4+, NpO+2, NpO2+2, and NpO+3. In basic solutions, they exist as the oxides and hydroxides Np(OH)3, NpO2, NpO2OH, NpO2(OH)2, and NpO3−5. Not as much work has been done to characterize neptunium in basic solutions. Np3+ and Np4+ can easily be reduced and oxidized to each other, as can NpO+2 and NpO2+2.
{\displaystyle {\begin{aligned}{\frac {\partial \rho }{\partial t}}+\nabla \cdot \left(\rho \mathbf {u} \right)&=0\\\Longleftrightarrow \nabla \cdot \mathbf {u} &=-{\frac {1}{\rho }}{\frac {d\rho }{dt}}={\frac {1}{v}}{\frac {dv}{dt}}\end{aligned}}}
=== Files === Copying files: Making copies of files is the simplest and most common way to perform a backup. A means to perform this basic function is included in all backup software and all operating systems. Partial file copying: A backup may include only the blocks or bytes within a file that have changed in a given period of time. This can substantially reduce needed storage space, but requires higher sophistication to reconstruct files in a restore situation. Some implementations require integration with the source file system. Deleted files: To prevent the unintentional restoration of files that have been intentionally deleted, a record of the deletion must be kept. Versioning of files: Most backup applications, other than those that do only full only/System imaging, also back up files that have been modified since the last backup. "That way, you can retrieve many different versions of a given file, and if you delete it on your hard disk, you can still find it in your [information repository] archive."
where z is the charge on the ion, e is the charge of a proton, kB is the Boltzmann constant and ψ is the potential of the charged surface. This however is inaccurate close to the surface, because it assumes that molar concentration is equal to activity. It also assumes that ions were modeled as point charges and was later modified. An improvement of this theory, known as the modified Gouy-Chapman theory, included the finite size of the ions with respect to their interaction with the surface in the form of a plane of closest approach.
When the USSR was dissolved in 1991, Moscow remained the capital of the Russian Federation. Since then, a market economy has emerged, producing a significant increase in Western-style retailing, services, architecture, and lifestyles. The city continued to grow during the 1990s and 2000s, its population rising from less than nine million to more than ten million. Scholars Mason and Nigmatullina argue that Soviet-era urban-growth controls produced controlled and sustainable metropolitan development, typified by the greenbelt built in 1935. Since then, however, low-density suburban sprawl has increased significantly, as a result of heavy demand for single-family dwellings (rather than multi-family apartments). In 1995–1997, the MKAD ring road was widened from an initial four lanes to ten lanes. In December 2002, Bulvar Dmitriya Donskogo became the first Moscow Metro station to open outside the MKAD. The Third Ring Road—intermediate between the early 19th-century Garden Ring and the Soviet-era outer ring road—was completed in 2004. The greenbelt is becoming more fragmented, and satellite cities are appearing at the fringe. Summer dachas are being converted into year-round residences; with the proliferation of automobiles, the city has heavy traffic congestion. Multiple old churches and other examples of architectural heritage that were demolished during the Stalin era have been restored, such as the Cathedral of Christ the Saviour. In the 2010s, Moscow's administration launched long-term projects such as the Moja Ulitsa (lit.
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.
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.