primary drying comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-04-19. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
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 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.
=== Isotope effects === Isotope peaks within a spectrum can help in structure elucidation. Compounds containing halogens (especially chlorine and bromine) can produce very distinct isotope peaks. The mass spectrum of methylbromide has two prominent peaks of equal intensity at m/z 94 (M) and 96 (M+2) and then two more at 79 and 81 belonging to the bromine fragment. Even when compounds only contain elements with less intense isotope peaks (carbon or oxygen), the distribution of these peaks can be used to assign the spectrum to the correct compound. For example, two compounds with identical mass of 150 Da, C8H12N3+ and C9H10O2+, will have two different M+2 intensities which makes it possible to distinguish between them.
=== Archives === CBC Digital Archives – Cold War Culture: The Nuclear Fear of the 1950s and 1960s The Cold War International History Project (CWIHP) The Cold War Files CONELRAD Cold War Pop Culture Site Archived 29 July 2020 at the Wayback Machine The Persuasive Cartography, The PJ Mode Collection, Cornell University Library (Select "Communism & Cold War" value to browse maps dated 1933–1982) Preview of the War We Do Not Want published in Collier's Magazine 27 October 1951
October 28, 2008 United Kingdom 500,000 mortgage holders are left in negative equity after house prices dropped 15% since the previous summer, with another 700,000 mortgage holders facing the same risk if prices continue to fall.
== Further research == As lenticule extraction techniques evolve, there is a possibility that extracted lenticules can be cryogenically preserved either for future donation, or re-implantation. Proof of concept has been carried out on primates where lenticules were extracted from monkeys and allogenically transplanted into other monkeys with positive results.
Tamago kake gohan (卵かけご飯; lit. 'egg on rice'), abbreviated TKG, is a popular Japanese breakfast food consisting of cooked Japanese rice topped or mixed with raw egg and soy sauce. It is sometimes referred to simply as tamago gohan (egg rice), tamago kake meshi (egg on rice/food), tamago bukkake gohan (egg splashed onto rice), or other variations. The dish has sometimes been referred to as the "soul food of the Japanese", characterized by Japan's exceptionally high standards of egg hygiene which minimize the risk of Salmonella poisoning from raw eggs. This allows the cultural practice of consuming raw eggs, combined with the staple food of rice, to flourish.
Sources: en.wikipedia.org
Sendai virus is used as a backbone for vaccine development against Mycobacterium tuberculosis that causes tuberculosis, against HIV-1 that causes AIDS and against other viruses, including those that cause severe respiratory infections in children. The latter include human respiratory syncytial virus (HRSV), human metapneumovirus (HMPV) and human parainfluenza viruses (HPIV). The vaccine studies against M. tuberculosis, HMPV, HPIV1 and, HPIV2 are in the pre-clinical stage, against HRSV a phase I clinical trial has been completed. The phase I clinical studies of SeV-based vaccination were also completed for HPIV1. They were done in adults and in 1–6-year-old children. As a result of vaccination against HPIV1, a significant boost in virus-specific neutralizing antibodies was observed. A SeV-based vaccine development against HIV-1 has reached a phase II clinical trial. In Japan intranasal Sendai virus-based SARS-CoV-2 vaccine was created and tested in a mouse model. More recent applications (2024–2025) include non-integrative gene delivery for fertility restoration in mouse models, enhanced transduction in pancreatic cancer, and temperature-sensitive platforms for CRISPR-Cas9 editing in human stem cells and viral genome engineering.
It is also possible to directly inoculate microbial identification panels with blood from a positive culture bottle, although this is not as reliable as testing subcultured bacteria because additives from the growth media can interfere with the results. Even faster diagnosis could be achieved through bypassing culture entirely and detecting pathogens directly from blood samples. A few direct testing systems are commercially available as of 2018, but the technology is still in its infancy. Most panels detect only a limited number of pathogens, and the sensitivity can be poor compared to conventional blood culture methods. Culturing remains necessary in order to carry out full antimicrobial sensitivity testing.
The following is a list of antibiotics. The highest division between antibiotics is bactericidal and bacteriostatic. Bactericidals kill bacteria directly, whereas bacteriostatics prevent them from dividing. However, these classifications are based on laboratory behavior. The development of antibiotics has had a profound effect on the health of people for many years. Also, both people and animals have used antibiotics to treat infections and diseases. In practice, both treat bacterial infections.
== Side effects == Nausea, ejaculation failure, insomnia, diarrhea, dry mouth, somnolence, dizziness, tremor, headache, excessive sweating, fatigue, restless legs syndrome and decreased libido are the common adverse effects associated with sertraline with the greatest difference from placebo. Those that most often result in interruption of the treatment are nausea, diarrhea, and insomnia. The incidence of diarrhea is higher with sertraline – especially when prescribed at higher doses – in comparison with other SSRIs. Over more than six months of sertraline therapy for depression, people showed no significant weight increase. A 30-month-long treatment with sertraline for OCD also resulted in no significant weight gain. Although the difference did not reach statistical significance, the average weight gain was lower for fluoxetine (1%) but higher for citalopram, fluvoxamine and paroxetine (2.5%). Of the sertraline group, 4.5% gained a large amount of weight (defined as more than 7% gain). This result compares favorably with placebo, where, according to the literature, 3–6% of patients gained more than 7% of their initial weight. The large weight gain was observed only among female members of the sertraline group; the significance of this finding is unclear because of the small size of the group. Over a two-week treatment of healthy volunteers, sertraline slightly improved verbal fluency but did not affect word learning, short-term memory, vigilance, flicker fusion time, choice reaction time, memory span, or psychomotor coordination.
Sources: en.wikipedia.org
=== As a fumigant === In the beginning of the 20th century sulfur dioxide was used in Buenos Aires as a fumigant to kill rats that carried the Yersinia pestis bacterium, which causes bubonic plague. The application was successful, and the application of this method was extended to other areas in South America. In Buenos Aires, where these apparatuses were known as Sulfurozador, but later also in Rio de Janeiro, New Orleans and San Francisco, the sulfur dioxide treatment machines were brought into the streets to enable extensive disinfection campaigns, with effective results.
In SN 12.59 and its counterpart SA 284, there is a chain that starts by saying that for someone who "abides in seeing [the Chinese has grasping at] the flavour in enfettering dharmas (saññojaniyesu dhammesu), there comes the appearance (avakkanti) of consciousness." There then follows the standard list. Then it states that if someone abides by seeing the danger (adinavanupassino) in the dharmas (the Chinese has seeing impermanence), there is no appearance of consciousness (Chinese has mind). SN 12.65 and 67 (and SA 287 and 288) begin the chain with both consciousness and name and form conditioning each other in a cyclical relationship. It also states that "consciousness turns back, it goes no further than name and form." SN 12.67 also contains a chain with consciousness and name and form being in a reciprocal relationship. In this sutta, Sariputta states that this relationship is like two sheaves of reeds leaning on each other for support (the parallel at SA 288 has three sheaves instead).
== Uses == It is nearly isosteric with methionine, even though it does not contain sulfur. For this reason, norleucine has been used to probe the role of methionine in Amyloid-β peptide (AβP) the central constituent of senile plaques in Alzheimer's disease. A study showed that with the substitution of the methionine at the 35 position with norleucine the neurotoxic effects of the Aβ peptides were completely negated.
Portal takes place in the Half-Life universe and within the Aperture Science Computer-Aided Enrichment Center, a research facility responsible for the creation of the portal gun. Information about Aperture Science, developed by Valve for creating its setting, is revealed during the game and via the real-world promotional website. According to the Aperture Science website, Cave Johnson founded the company in 1943 for the purpose of making shower curtains for the U.S. military. After becoming mentally unstable from "moon rock poisoning" in 1978, Johnson created a three-tier research and development plan to make his organization successful. The first two tiers, the Counter-Heimlich Maneuver (a maneuver designed to ensure choking) and the Take-A-Wish Foundation (a program to give the wishes of terminally ill children to adults in need of dreams), were commercial failures and led to an investigation of the company by the U.S. Senate. However, when the investigative committee heard of the success of the third tier—a person-sized, ad hoc quantum tunnel through physical space, with a possible application as a shower curtain—it recessed permanently and gave Aperture Science an open-ended contract to continue its research. The development of GLaDOS, an artificially intelligent research assistant and disk-operating system, began in 1986 in an attempt to speed up portal technology research in competition with Black Mesa's work on similar portal technology.
The variance is infinite. In a real reactor, diffusion will eventually mix the layers so that the tail of the RTD becomes exponential and the variance finite; but laminar flow reactors can have variance greater than 1, the maximum for CTSD reactors.
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.