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 2026-05-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 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 |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
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.
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.
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.
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.
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.
where aB = 0.053 nm is the Bohr radius, m is the mass, μ is the reduced mass, and εr is the size-dependent dielectric constant (relative permittivity). This results in the increase in the total emission energy (the sum of the energy levels in the smaller band gaps in the strong confinement regime is larger than the energy levels in the band gaps of the original levels in the weak confinement regime) and the emission at various wavelengths. If the size distribution of QDs is not enough peaked, the convolution of multiple emission wavelengths is observed as a continuous spectra. Confinement energy The exciton entity can be modeled using the particle in the box. The electron and the hole can be seen as hydrogen in the Bohr model with the hydrogen nucleus replaced by the hole of positive charge and negative electron mass. Then the energy levels of the exciton can be represented as the solution to the particle in a box at the ground level (n = 1) with the mass replaced by the reduced mass. Thus by varying the size of the quantum dot, the confinement energy of the exciton can be controlled. Bound exciton energy There is Coulomb attraction between the negatively charged electron and the positively charged hole. The negative energy involved in the attraction is proportional to Rydberg's energy and inversely proportional to square of the size-dependent dielectric constant of the semiconductor. When the size of the semiconductor crystal is smaller than the exciton Bohr radius, the Coulomb interaction must be modified to fit the situation.
== Investigation == Mendonça's tutor called his parents because the child had not turned up for his 5:00 PM lesson, and they quickly initiated a search for him. Because Mendonça had told his mother that he was planning to meet up with his friend Dias, the police sought him for questioning. Dias was in an emotional state while being questioned, and simply replied that he did not know the boy's whereabouts, but that the police "should close the borders". Dias was interrogated by the police. Mendonça's cousin, João André Mendonça, recounted to the police that he, Mendonça and Dias had had a conversation where Dias had invited them to go meet up with a prostitute. The cousin said he had not joined Mendonça and Dias that afternoon because his mother would not let him leave the house. The police considered the possibility of kidnapping, slavery, homicide and suicide.
Prussian blue or "ferric ferrocyanide", Fe4[Fe(CN)6]3, is an old and well-known iron-cyanide complex, extensively used as pigment and in several other applications. Its formation can be used as a simple wet chemistry test to distinguish between aqueous solutions of Fe2+ and Fe3+ as they react (respectively) with potassium ferricyanide and potassium ferrocyanide to form Prussian blue. Another old example of an organoiron compound is iron pentacarbonyl, Fe(CO)5, in which a neutral iron atom is bound to the carbon atoms of five carbon monoxide molecules. The compound can be used to make carbonyl iron powder, a highly reactive form of metallic iron. Thermolysis of iron pentacarbonyl gives triiron dodecacarbonyl, Fe3(CO)12, a complex with a cluster of three iron atoms at its core. Collman's reagent, disodium tetracarbonylferrate, is a useful reagent for organic chemistry; it contains iron in the −2 oxidation state. Cyclopentadienyliron dicarbonyl dimer contains iron in the rare +1 oxidation state.
== Definition == Urea and creatinine are nitrogenous end products of metabolism. Urea is the primary metabolite derived from dietary protein and tissue protein turnover. Creatinine is the product of muscle creatine catabolism. Both are relatively small molecules (60 and 113 daltons, respectively) that distribute throughout total body water. In Europe, the whole urea molecule is assayed, whereas in the United States only the nitrogen component of urea (the blood or serum urea nitrogen, i.e., BUN or SUN) is measured. The BUN, then, is roughly one-half (7/15 or 0.466) of the blood urea. The normal range of urea nitrogen in blood or serum is 5 to 20 mg/dl, or 1.8 to 7.1 mmol urea per liter. The range is wide because of normal variations due to protein intake, endogenous protein catabolism, state of hydration, hepatic urea synthesis, and renal urea excretion. A BUN of 15 mg/dl would represent significantly impaired function for a woman in the thirtieth week of gestation. Her higher glomerular filtration rate (GFR), expanded extracellular fluid volume, and anabolism in the developing fetus contribute to her relatively low BUN of 5 to 7 mg/dl. In contrast, the rugged rancher who eats in excess of 125 g protein each day may have a normal BUN of 20 mg/dl. The normal serum creatinine (sCr) varies with the subject's body muscle mass and with the technique used to measure it. For the adult male, the normal range is 0.6 to 1.2 mg/dl, or 53 to 106 μmol/L by the kinetic or enzymatic method, and 0.8 to 1.5 mg/dl, or 70 to 133 μmol/L by the older manual Jaffé reaction.
MALAT1-associated small cytoplasmic RNA, also known as mascRNA, is a non-coding RNA found in the cytosol. This is a small RNA, roughly 53–61 nucleotides in length, that is processed from a much longer ncRNA called MALAT1 by an enzyme called RNase P. This RNA is expressed in many different human tissues, is highly conserved by evolution and shares a remarkable similarity to tRNA which is also produced by RNase P, yet this RNA is not aminoacylated in HeLa cells. The primary transcript, MALAT1 (metastasis associated lung adenocarcinoma transcript 1), appears to be upregulated in several malignant cancers. Another small RNA that is homologous to mascRNA, called menRNA, is processed from another long ncRNA called MEN beta. MALAT1 appears to be involved in the regulation of alternative splicing. MALAT1 interacts with SR proteins, influencing the distribution of these in nuclear speckle domains.
Sources: en.wikipedia.org
=== Other drugs === Other drugs like sulfur and resorcinol have also been found useful in treating seborrheic dermatitis. These drugs have keratolytic and antiseptic properties which may benefit seborrhoea. Salicylic acid has a mild effect on seborrhoea.
Histones H2A, H2B, H3 and H4 form the core of a nucleosome and thus are called core histones. Processing of core histones is done differently because typical histone mRNA lacks several features of other eukaryotic mRNAs, such as poly(A) tail and introns. Thus, such mRNAs do not undergo splicing and their 3' processing is done independent of most cleavage and polyadenylation factors. Core histone mRNAs have a special stem-loop structure at 3-prime end that is recognized by a stem–loop binding protein and a downstream sequence, called histone downstream element (HDE) that recruits U7 snRNA. Cleavage and polyadenylation specificity factor 73 cuts mRNA between stem-loop and HDE Histone variants, such as H2A.Z or H3.3, however, have introns and are processed as normal mRNAs including splicing and polyadenylation.
Vaccine production and storage has great potential in transgenic plants. Vaccines are expensive to produce, transport, and administer, so having a system that could produce them locally would allow greater access to poorer and developing areas. As well as purifying vaccines expressed in plants it is also possible to produce edible vaccines in plants. Edible vaccines stimulate the immune system when ingested to protect against certain diseases. Being stored in plants reduces the long-term cost as they can be disseminated without the need for cold storage, don't need to be purified, and have long term stability. Also being housed within plant cells provides some protection from the gut acids upon digestion. However the cost of developing, regulating, and containing transgenic plants is high, leading to most current plant-based vaccine development being applied to veterinary medicine, where the controls are not as strict. Genetically modified crops have been proposed as one of the ways to reduce farming-related CO2 emissions due to higher yield, reduced use of pesticides, reduced use of tractor fuel and no tillage. According to a 2021 study, in EU alone widespread adoption of GE crops would reduce greenhouse gas emissions by 33 million tons of CO2 equivalent or 7.5% of total farming-related emissions.
Sandoz also marketed and sold pure psilocybin under the name Indocybin to clinicians and researchers worldwide. There were no reports of serious complications when psilocybin was used in this way. In the early 1960s, Harvard University became a testing ground for psilocybin through the efforts of Timothy Leary and his associates Ralph Metzner and Richard Alpert (who later changed his name to Ram Dass). Leary obtained synthesized psilocybin from Hofmann through Sandoz Pharmaceuticals. Some studies, such as the Concord Prison Experiment, suggested promising results using psilocybin in clinical psychiatry. But according to a 2008 review of safety guidelines in human hallucinogenic research, Leary's and Alpert's well-publicized termination from Harvard and later advocacy of hallucinogen use "further undermined an objective scientific approach to studying these compounds". In response to concerns about the increase in unauthorized use of psychedelic drugs by the general public, psilocybin and other hallucinogenic drugs were unfavorably covered in the press and faced increasingly restrictive laws. In the U.S., laws passed in 1966 that prohibited the production, trade, or ingestion of hallucinogenic drugs; Sandoz stopped producing LSD and psilocybin the same year. In 1970, Congress passed "The Federal Comprehensive Drug Abuse Prevention and Control Act" that made LSD, peyote, psilocybin, and other hallucinogens illegal to use for any purpose, including scientific research.
Sources: en.wikipedia.org
=== Other === Due to its naturally selective spectrum of activity, it is also employed as a selective agent in microbiological media to isolate gram-negative bacteria, yeast, and moulds. Nisin has also been used in food packaging applications and can serve as a preservative by controlled release onto the food surface from the polymer packaging. In combination with miconazole, it has been studied as a possible treatment for infections of Clostridioides difficile.
=== Pharmacodynamics === Pharmacodynamics includes enzymes for which vitamin C is a cofactor, with function potentially compromised in a deficiency state, and any enzyme cofactor or other physiological function affected by administration of vitamin C, orally or injected, in excess of normal requirements. At normal physiological concentrations, vitamin C is an enzyme substrate or cofactor and an electron donor antioxidant. The enzymatic functions include the synthesis of collagen, carnitine, and neurotransmitters; the synthesis and catabolism of tyrosine; and the metabolism of microsomes. In nonenzymatic functions it acts as a reducing agent, donating electrons to oxidized molecules and preventing oxidation in order to keep iron and copper atoms in their reduced states. At non-physiological concentrations achieved by intravenous dosing, vitamin C can be a pro-oxidant, with therapeutic toxicity against cancer cells. Vitamin C is a cofactor for the following enzymes:
The incidence of side effects with doxepin and its safety at these doses was similar to that of placebo in clinical trials; the most frequent side effects were headache and somnolence/sedation, both with an incidence of less than 5%. Other side effects sometimes associated with antihistamines, including daytime sedation, increased appetite, and weight gain, all were not observed. Clinical evidence of H1 receptor antagonists and TCAs for the treatment insomnia shows mixed effectiveness and is limited in its quality due to weaknesses like small sample sizes and poor generalizability. However, doxepin is a unique and notable exception; it has been well-studied in the treatment of insomnia and shows consistent benefits with excellent tolerability and safety. Aside from diphenhydramine and doxylamine, which have historical approval as hypnotics, doxepin is the only H1 receptor antagonist that is specifically approved for the treatment of insomnia in the United States. The effect sizes of very low-dose doxepin in the treatment of insomnia range from small to medium. These include subjective and objective measures of sleep maintenance, sleep duration, and sleep efficiency. Conversely, very low-dose doxepin shows relatively weak effects on sleep initiation and does not significantly separate from placebo on this measure. This is in contrast to benzodiazepines and nonbenzodiazepine (Z-drug) hypnotics, which are additionally effective in improving sleep onset latency.
Duterte accused David of being involved in illegal drugs and stealing church donations, after which the CBCP came to David's defense and vouched for his integrity. Citing continued criticism from Catholic bishops, Duterte's verbal attacks on the Catholic Church escalated in mid-2018 to early 2019, during which he challenged the Catholic Church to show evidence of the existence of God, while expressing his belief in "one Supreme God" and "a universal mind somewhere which controls the universe". In one of his harshest vitriol in June 2018, he remarked that God was "stupid" for permitting the serpent to tempt Eve in the creation story in the Bible; though the controversial statement was later clarified by his spokesperson as Duterte's "personal opinion", it contributed to Duterte's quarterly approval rating dipping to its lowest at 45%. Efforts by the Church to rally public support against the administration's war on drugs, however, were less effective due to Duterte's domestic popularity and high trust ratings.
Matthew turning up after 20 years and wanting a relationship with her is "too much for Ari to handle", especially with Ari knowing how he took advantage of Mia. Chloe forges a bond with Matthew, which angers Mia and Ari, who later punches Matthew during an argument. Matthew realises he can use Ari's criminal record to his advantage and warns Mia to back off, or he will report Ari's assault to the police. Matthew tries to take Chloe away from Mia by offering her the tuition to a prestigious college in the city. Ari believes that telling Chloe the truth about her conception will keep her in the Bay. Kipa-Williams stated: "Ari respects Mia's choice not to tell Chloe about what happened with Matthew, but he also wants to keep her from making decisions that may affect her wellbeing." After Chloe accepts Matthews's offer, Mia tells her the truth and Chloe finally understands Mia's behaviour towards Matthew. Ari later receives a phone call from Chloe asking for his help as Matthew has turned up at the house. Kipa-Williams pointed out that Ari believes Matthew is "unpredictable and dangerous" and would do anything to protect Chloe and Mia. The story sees Chloe accidentally kill Matthew when she hits him over the head with a brick to protect Mia.
Sources: en.wikipedia.org
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.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
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.