Everything below concerns Sublimation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-02-21. Numbers and descriptions here follow the published literature rather than marketing material.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
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 |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
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.
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.
== Contraindications == Oliceridine should not be given to people with significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment; known or suspected gastrointestinal obstruction; or known hypersensitivity to the medication.
Thirdly, succinylcholine use has been associated with postoperative myalgia, where patients often experience muscle pain similar to that of post-exercise muscle pain mainly in the shoulders, neck, neck and upper abdominal muscle the following day after surgery, especially in young healthy patients with greater muscle mass, whereas reports from children, elderly and pregnant woman are less frequent. This is caused by the fasciculations (muscle twitches) that appear in sites such as intercostal muscles, and the diaphragm. These fasciculations are not relieved through analgesics, and in common practice, a sub-paralyzing dose of non-depolarizing neuromuscular blocker is administered a few minutes before succinylcholine administration to reduce visible fasciculation and postoperative myalgia. The use of succinylcholine is therefore also contraindicated in patient with muscle myopathy within 24 to 72 hours post-administration. Non-depolarizing drug Atracurium: Atracurium is commonly associated with histamine-related symptoms, most notably flushing and erythema. Less commonly seen adverse effects include urticaria, hypotension, wheezing, tachycardia, bronchospasm, dyspnea, bradycardia, and laryngospasm. Moreover, drops of up to 30 mmHg in mean arterial pressure was also observed within two minutes of administration in some patients. H1 and H2 receptor blocking agents can be used to attenuate the drop in mean arterial pressure. A slow injection speed between 30 and 60 seconds reduces adverse effects.
March 26 COVID-19 pandemic Maine reports its first case of the Lineage P.1 variant, which was originally detected in Brazil. Wisconsin confirms their first cases of the Lineage P.1 and 501.V2 variants of SARS-CoV-2. Arizona reports its first case of the 501.V2 variant, which was originally detected in South Africa. New Jersey amends its alcohol and cannabis laws to allow police to notify parents or guardians after a first-time offense by a minor, following strong opposition to the prohibition on first-time notifications implemented when New Jersey legalized cannabis the previous month. The U.S. Food and Drug Administration (FDA) approves Abecma to treat multiple myeloma. Abecma is the first cell-based gene therapy approved by the FDA for the treatment of multiple myeloma. March 29 In Minnesota, opening statements begin at the trial of former police officer Derek Chauvin, who is accused of murdering 46-year-old black man George Floyd by kneeling on his neck. The Arkansas Senate passed, HB1570, a bill that prohibited normally functioning and physically healthy minors from puberty blockers, cross-sex hormones, and genital and non-genital invasive surgical alterations. A judge orders three men charged with plotting to kidnap Michigan Governor Gretchen Whitmer to stand trial, after a three-day preliminary hearing. Threat of terrorism charges are also dismissed against two of the defendants. Killing of Adam Toledo – A 13-year-old Latino boy, Adam Toledo, is shot and killed by an officer of the Chicago Police Department.
Sources: en.wikipedia.org
==== Gomori-positive astrocytes and brain dysfunction ==== A type of astrocyte with an aging-related pathology has been described over the last fifty years. Astrocytes of this subtype possess prominent cytoplasmic granules that are intensely stained by Gomori's chrome alum hematoxylin stain, and hence are termed Gomori-positive (GP) astrocytes. They can be found throughout the brain, but are by far the most abundant in the olfactory bulbs, medial habenula, dentate gyrus of the hippocampus, arcuate nucleus of the hypothalamus, and in the dorsal medulla, just beneath the area postrema. Gomori-positive cytoplasmic granules are derived from damaged mitochondria engulfed within lysosomes. Cytoplasmic granules contain undigested remnants of mitochondrial structures. These contents include heme-linked copper and iron atoms remaining from mitochondrial enzymes. These chemical substances account for the pseudoperoxidase activity of Gomori-positive granules that can utilized to stain for these granules. Oxidative stress is believed to be cause of damage to these astrocytes. However, the exact nature of this stress is uncertain. Brain regions enriched in Gomori-positive astrocytes also contain a sub-population of specialized astrocytes that synthesize Fatty Acid Binding Protein 7 (FABP7). Indeed, astrocytes in the hypothalamus that synthesize FABP7 have also been shown to possess Gomori-positive granules. Thus, a connection between these two glial features is apparent.
== History == The precise origin of absinthe is unclear. The medical use of wormwood dates back to ancient Egypt and is mentioned in the Ebers Papyrus from around 1550 BC. Wormwood extracts and wine-soaked wormwood leaves were used as remedies by the ancient Greeks. Moreover, some evidence exists of a wormwood-flavoured wine in ancient Greece called absinthites oinos. Lucretius' De Rerum Natura (I, 936–950) says that a drink containing wormwood was given as medicine to children in a cup with honey on the brim to make it drinkable. The first evidence of absinthe, in the sense of a distilled spirit containing green anise and fennel, dates to the 18th century. According to popular legend, it began as an all-purpose patent remedy created by Dr. Pierre Ordinaire, a French doctor living in Couvet, Switzerland, around 1792 (the exact date varies by account). Ordinaire's recipe was passed on to the Henriod sisters of Couvet, who sold it as a medicinal elixir. By other accounts, the Henriod sisters may have been making the elixir before Ordinaire's arrival. In either case, a certain Major Dubied acquired the formula from the sisters in 1797 and opened the first absinthe distillery named Dubied Père et Fils in Couvet with his son Marcellin and son-in-law Henry-Louis Pernod. In 1805, they built a second distillery in Pontarlier, France, under the company name Maison Pernod Fils. Pernod Fils remained one of the most popular brands of absinthe until the drink was banned in France in 1914.
== Protein == The expressed peptide contains a three-turn α-helix, and has no symmetry. The length of the peptide depends on where it is produced. If it is produced inside the mitochondria it will be 21 amino acids long. If it is produced outside the mitochondria, in the cytosol, it will be 24 amino acids long. Both peptides have been shown to have biological activity. The full length 24 amino acid version of humanin has the sequence MAPRGFSCLLLLTSEIDLPVKRRA, with four residues cleaved from the C terminal end to form the 20 amino acid mitochondrial version MAPRGFSCLLLLTSEIDLPV. Several other natural isoforms are also known with slight variations to the amino acid sequence. Synthetic versions often have one or more amino acid changes to increase stability and improve activity, such as HNG with a S→G substitution at position 14, and HNGF6A which has an F→A substitution at position 6 as well. Humanin-glycine (HNG) is up to 1000x more potent than the natural version depending how the activity is assayed, and so is one of the more common synthetic analogues used in research and investigated for potential clinical applications. Shorter fragments such as HN(1-19) and HN(1-17) also retain some activity but are generally less potent.
Sources: en.wikipedia.org
=== Abuse potential === Pregabalin has potential for recreational use and abuse. It possesses a relatively wide therapeutic index and margin of safety compared to other central nervous system (CNS) depressants, and its effects may include euphoria, anxiolysis, and sedation. Although generally considered to have low abuse potential, reports describe pregabalin inducing sensations of euphoria, calmness, excitement, and a "high" comparable to that of cannabis. These effects may contribute to the development of substance dependence, and withdrawal symptoms can occur if the medication is stopped abruptly. While pregabalin and cannabis share certain effects, such as CNS depressant and orexigenic (appetite-stimulating) properties, they differ significantly in their pharmacodynamics. Cannabis is primarily an anxiogenic substance with mild psychedelic effects, whereas pregabalin is an anxiolytic agent associated with mild euphoria that is prone to rapid tolerance.
== Research == Laboratory studies and clinical trials have started investigating the possibility of increasing the anticancer potency of temozolomide by combining it with other pharmacologic agents. For example, clinical trials have indicated that the addition of chloroquine might be beneficial for the treatment of glioma patients. Laboratory studies found that temozolomide killed brain tumor cells more efficiently when epigallocatechin gallate (EGCG), a component of green tea, was added; however, the efficacy of this effect has not yet been confirmed in brain-tumor patients. Preclinical studies reported in 2010 on investigations into the use of the novel oxygen diffusion-enhancing compound trans sodium crocetinate (TSC) when combined with temozolomide and radiation therapy and a clinical trial was underway as of August 2015. While the above-mentioned approaches have investigated whether the combination of temozolomide with other agents might improve therapeutic outcome, efforts have also started to study whether altering the temozolomide molecule itself can increase its activity. One such approach permanently fused perillyl alcohol, a natural compound with demonstrated therapeutic activity in brain cancer patients, to the temozolomide molecule. The resultant novel compound, called NEO212 or TMZ-POH, revealed anticancer activity that was significantly greater than that of either of its two parent molecules, temozolomide and perillyl alcohol.
=== Animals cannot resynthesize carbohydrates from fatty acids === The main fuel stored in the bodies of animals is fat. A young adult human's fat stores average between about 15–20 kg (33–44 lb), but varies greatly depending on age, sex, and individual disposition. In contrast, the human body stores only about 400 g (0.9 lb) of glycogen, of which 300 g (0.7 lb) is locked inside the skeletal muscles and is unavailable to the body as a whole. The 100 g (0.2 lb) or so of glycogen stored in the liver is depleted within one day of starvation. Thereafter the glucose that is released into the blood by the liver for general use by the body tissues, has to be synthesized from the glucogenic amino acids and a few other gluconeogenic substrates, which do not include fatty acids. Fatty acids are broken down to acetyl-CoA by means of beta oxidation inside the mitochondria, whereas fatty acids are synthesized from acetyl-CoA outside the mitochondrion, in the cytosol. The two pathways are distinct, not only in where they occur, but also in the reactions that occur, and the substrates that are used. The two pathways are mutually inhibitory, preventing the acetyl-CoA produced by beta-oxidation from entering the synthetic pathway via the acetyl-CoA carboxylase reaction. It can also not be converted to pyruvate as the pyruvate decarboxylation reaction is irreversible. Instead it condenses with oxaloacetate, to enter the citric acid cycle.
=== Late modern botany === Building upon the gene-chromosome theory of heredity that originated with Gregor Mendel (1822–1884), August Weismann (1834–1914) proved that inheritance only takes place through gametes. No other cells can pass on inherited characters. The work of Katherine Esau (1898–1997) on plant anatomy is still a major foundation of modern botany. Her books Plant Anatomy and Anatomy of Seed Plants have been key plant structural biology texts for more than half a century.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
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.