The short version of secondary drying fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-28. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Process removes water by sublimation under vacuum. |
| Typical primary drying shelf temperature | -40 C to -10 C | Set below the formulation's collapse temperature. |
| Typical chamber pressure | 0.05-0.3 mbar | Low pressure allows ice to sublime below its triple point. |
| Water content after drying | 0.5-3% by weight | Higher values may reduce storage stability for some materials. |
| Key thermal parameter | Collapse temperature | Measured by freeze-drying microscopy or differential scanning calorimetry. |
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 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.
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.
== Uses == A precursor for mercaptan is 3-mercapto-3-methylbutanol (MMB). MMB is a chemical which gives a strong odor to cat urine. This smell is likely used for communicating amongst cats as well as scaring away predators and rivals. That is, the smell can mark their territory amongst other male cats and attract a female mate.
Chronic use may result in cocaine dependence, withdrawal symptoms, neurotoxicity, and nasal damage, including cocaine-induced midline destructive lesions. Coca cultivation and initial processing occur primarily in Latin America, especially in the Andes regions of Bolivia, Peru, and Colombia. Cultivation is expanding into Central America, including Honduras, Guatemala, and Belize. Violence linked to the cocaine trade continues to affect Latin America and the Caribbean and is expanding into Western Europe, Asia, and Africa as transnational organized crime groups compete globally. Cocaine remains the world's fastest-growing illicit drug market. Coca chewing dates back at least 8,000 years in South America. Large-scale cultivation occurred in Taiwan and Java prior to World War II. The cocaine boom—a sharp rise in illegal production and trade—began in the late 1970s and peaked in the 1980s. Cocaine is regulated under international drug control conventions, though its legal status varies nationally: several countries have decriminalized possession of small quantities.
== Function == All interferons share several common effects: they are antiviral agents and they modulate functions of the immune system. Administration of Type I IFN has been shown experimentally to inhibit tumor growth in animals, but the beneficial action in human tumors has not been widely documented. A virus-infected cell releases viral particles that can infect nearby cells. However, the infected cell can protect neighboring cells against a potential infection of the virus by releasing interferons. In response to interferon, cells produce large amounts of an enzyme known as protein kinase R (PKR). This enzyme phosphorylates a protein known as eIF-2 in response to new viral infections; the phosphorylated eIF-2 forms an inactive complex with another protein, called eIF2B, to reduce protein synthesis within the cell. Another cellular enzyme, RNAse L—also induced by interferon action—destroys RNA within the cells to further reduce protein synthesis from both viral and host genes. Inhibited protein synthesis impairs both virus replication and infected host cells. In addition, interferons induce production of hundreds of other proteins—known collectively as interferon-stimulated genes (ISGs)—that have roles in combating viruses and other actions produced by interferon. They also limit viral spread by increasing p53 activity, which kills virus-infected cells by promoting apoptosis. The effect of IFN on p53 is also linked to its protective role against certain cancers.
Miosis (constricted pupils) Vomiting Spasms of the stomach and intestines Hypoventilation (breathing that is too slow/shallow) Drowsiness, sleepiness, disorientation, sedation, unresponsiveness Skin that is cool, clammy (damp), and pale Blue fingernails and lips Limp muscles, trouble staying awake, nausea Unconsciousness and coma The respiratory depression of an overdose can be treated with naloxone. Naloxone is preferred to the newer, longer-acting antagonist naltrexone. Despite methadone's much longer duration of action compared to heroin and other shorter-acting agonists and the need for repeat doses of the antagonist naloxone, it is still used for overdose therapy. As naltrexone has a longer half-life, it is more difficult to titrate. If too large a dose of the opioid antagonist is given to a dependent person, it will result in withdrawal symptoms (possibly severe). When using naloxone, the naloxone will be quickly eliminated and the withdrawal will be short-lived. Doses of methadone take longer to be eliminated from the person's system. A common problem in treating methadone overdoses is that given the short action of naloxone (versus the extremely longer-acting methadone), a dosage of naloxone given to a methadone-overdosed person will initially work to bring the person out of overdose, but once the naloxone wears off, if no further naloxone is administered, the person can go right back into overdose (based upon time and dosage of the methadone ingested).
Sources: en.wikipedia.org
==== Mineral extraction and hardware footprint ==== The physical infrastructure of AI, specifically the Graphics Processing Units (GPUs) and data centres required to train and run large language models, relies heavily on critical minerals and rare earth elements. A 2026 study published in Nature Communications Earth & Environment quantified the material footprint of AI training, revealing that AI hardware consists of approximately 90% heavy metals. The study estimated that training a single large language model requires the equivalent lifetime consumption of between 1,760 and 8,800 GPUs, underscoring that incremental model performance gains come at disproportionately high material costs. The extraction of these minerals, such as cobalt, lithium, tantalum, and coltan, is heavily concentrated in the Global South and is frequently associated with severe environmental degradation and human rights abuses. For example, the Democratic Republic of Congo (DRC) holds roughly 70% of the world's cobalt reserves, alongside vast deposits of coltan and copper. Academic analyses note that the global AI supply chain relies on a familiar geopolitical division of labour: African countries mine the raw materials, while Western and East Asian economies refine them and capture the technological value. In the UK, a coalition of NGOs including Friends of the Earth, the Trade Justice Movement, and the London Mining Network published a joint report in May 2026 criticising the UK Government's critical minerals agenda.
Intelligence & achievement tests – These tests are designed to measure certain specific kinds of cognitive functioning (often referred to as IQ) in comparison to a norming group. These tests, such as the WISC-IV and the WAIS, attempt to measure such traits as general knowledge, verbal skill, memory, attention span, logical reasoning, and visual/spatial perception. Several tests have been shown to predict accurately certain kinds of performance, especially scholastic. Other tests in this category include the WRAML and the WIAT. Personality tests – Tests of personality aim to describe patterns of behavior, thoughts, and feelings. They generally fall within two categories: objective and projective. Objective measures, such as the MMPI, are based on restricted answers—such as yes/no, true/false, or a rating scale—which allow for the computation of scores that can be compared to a normative group. Projective tests, such as the Rorschach inkblot test, allow for open-ended answers, often based on ambiguous stimuli. Other commonly used personality assessment measures include the PAI and the NEO Neuropsychological tests – Neuropsychological tests consist of specifically designed tasks used to measure psychological functions known to be linked to a particular brain structure or pathway. They are typically used to assess impairment after an injury or illness known to affect neurocognitive functioning, or when used in research, to contrast neuropsychological abilities across experimental groups.
Denaturation can also be caused by changes in the pH which can affect the chemistry of the amino acids and their residues. The ionizable groups in amino acids are able to become ionized when changes in pH occur. A pH change to more acidic or more basic conditions can induce unfolding. Acid-induced unfolding often occurs between pH 2 and 5, base-induced unfolding usually requires pH 10 or higher.
Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis, and chromatography; the advent of genetic engineering has made possible a number of methods to facilitate purification. To perform in vitro analysis, a protein must be purified away from other cellular components. This process usually begins with cell lysis, in which a cell's membrane is disrupted and its internal contents released into a solution known as a crude lysate. The resulting mixture can be purified using ultracentrifugation, which fractionates the various cellular components into fractions containing soluble proteins; membrane lipids and proteins; cellular organelles, and nucleic acids. Precipitation by a method known as salting out can concentrate the proteins from this lysate. Various types of chromatography are then used to isolate the protein or proteins of interest based on properties such as molecular weight, net charge and binding affinity. The level of purification can be monitored using various types of gel electrophoresis if the desired protein's molecular weight and isoelectric point are known, by spectroscopy if the protein has distinguishable spectroscopic features, or by enzyme assays if the protein has enzymatic activity. Additionally, proteins can be isolated according to their charge using electrofocusing. For natural proteins, a series of purification steps may be necessary to obtain protein sufficiently pure for laboratory applications.
Bethlem myopathy is a slowly progressive muscle disease characterized predominantly by contractures, rigidity of the spine, skin abnormalities and proximal muscle weakness. Symptoms may present as early as infancy, with typical contractures and hyperlaxity of joints; however, in some patients, symptoms may go unnoticed until adolescence or adulthood. Serum creatine kinase (CK) is usually normal to mildly elevated (<5×).
Sources: en.wikipedia.org
252Cf(12C,αxn)260−xNo (x=3?) This reaction was studied at the LBNL in 1961 as part of their search for element 104. They detected 8.2 MeV alpha particles with a half-life of 15 s. This activity was assigned to a Z=102 isotope. Later work suggests an assignment to 257No, resulting most likely from the α3n channel with the 252Cf component of the californium target.
Diarrhea Rash Fever Facial swelling Difficulty breathing Unusual bleeding Seizures This medicine is passed through breast milk, so its use during pregnancy or breastfeeding should only be done when clearly needed. Primaxin is cleared from the body by the kidneys, so it is important to tell one's doctor about any other drugs being taken that are also cleared through the kidneys (such as other antibiotics), especially for older patients, as kidney function declines with age. Patients who are allergic to penicillin, cephalosporins, and related drugs may react to imipenem. It is important tell one's doctor or pharmacist one's medical history, especially of brain disorders (e.g., seizures, head injury, tumor), kidney disease, liver disease, and stomach/intestinal diseases (e.g., colitis).
by Kimura). In 1981, Joseph Felsenstein proposed a four-parameter model (F81) in which the substitution rate corresponds to the equilibrium frequency of the target nucleotide. Hasegawa, Kishino, and Yano unified the two last models to a five-parameter model (HKY). After these pioneering efforts, many additional sub-models of the GTR model were introduced into the literature (and common use) in the 1990s. Other models that move beyond the GTR model in specific ways were also developed and refined by several researchers. Almost all DNA substitution models are mechanistic models (as described above). The small number of parameters that one needs to estimate for these models makes it feasible to estimate those parameters from the data. It is also necessary because the patterns of DNA sequence evolution often differ among organisms and among genes within organisms. The later may reflect optimization by the action of selection for specific purposes (e.g. fast expression or messenger RNA stability) or it might reflect neutral variation in the patterns of substitution. Thus, depending on the organism and the type of gene, it is likely necessary to adjust the model to these circumstances.
== Background == In general, it is difficult to decompose a combined wave–mean motion into a mean and a wave part, especially for flows bounded by a wavy surface: e.g. in the presence of surface gravity waves or near another undulating bounding surface (like atmospheric flow over mountainous or hilly terrain). However, this splitting of the motion in a wave and mean part is often demanded in mathematical models, when the main interest is in the mean motion – slowly varying at scales much larger than those of the individual undulations. From a series of postulates, Andrews & McIntyre (1978a) arrive at the (GLM) formalism to split the flow: into a generalised Lagrangian mean flow and an oscillatory-flow part. The GLM method does not suffer from the strong drawback of the Lagrangian specification of the flow field – following individual fluid parcels – that Lagrangian positions which are initially close gradually drift far apart. In the Lagrangian frame of reference, it therefore becomes often difficult to attribute Lagrangian-mean values to some location in space. The specification of mean properties for the oscillatory part of the flow, like: Stokes drift, wave action, pseudomomentum and pseudoenergy – and the associated conservation laws – arise naturally when using the GLM method. The GLM concept can also be incorporated into variational principles of fluid flow.
The Good Food Award Television and Radio Personality – 1995/1996 The England for Excellence Awards – Outstanding Contribution to Tourism Award – 1988–1998 Caterer and Hotelkeeper 1999 Chef Award – Chef of the Year The Catey Awards AA Guide Chefs' Chef of the Year 1999–2000 Waterford Wedgwood Hospitality Award – 1999 The Glenfiddich Trophy – 2001 The Cornwall Tourist Award – A special award for outstanding services to Cornwall 2002 OBE – 2003 New Year Honours: For services to tourism in Cornwall CatererSearch 100 – 14th most influential chef in UK in 2005 In 2012, Stein was among the British cultural icons selected by pop artist Sir Peter Blake to appear in a new version of his most famous artwork – the Beatles' Sgt. Pepper's Lonely Hearts Club Band album cover – to celebrate the British cultural figures of the last six decades. 5 July 2016, Rick and Jill Stein received the Special Award at the prestigious Catey Awards, for their more than 41 years of outstanding contribution to the hospitality industry. CBE – 2018 New Year Honours: For services to the economy
Sources: en.wikipedia.org
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.
Freezing determines ice crystal size, pore structure, and the concentration of solutes in remaining liquid. Faster freezing generally creates smaller ice crystals and a denser dried matrix. These features affect drying rate and reconstitution behavior.
Lyophilization reduces water content but usually leaves a small amount of water in the dried material. Some water remains bound to solids or trapped in the dried matrix. Very low water targets can require extended secondary drying, which may alter product stability.
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.