This is a working overview of glass transition, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-22 and is reviewed periodically as new material appears.
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.
Quality control for lyophilized products focuses on appearance, moisture level, reconstitution time, and structural integrity. A cake should be uniform, intact, and free of meltback or collapse. Moisture level is measured by Karl Fischer titration or thermogravimetric analysis. Reconstitution time reflects pore structure and formulation. Visual inspection and vial integrity checks detect cracks, stopper defects, or particulate matter. These checks are often performed on samples from each batch. They help confirm that the drying cycle performed as intended.
Storage stability depends on water content, oxygen exposure, and temperature. Lyophilized solids are hygroscopic and can absorb water if exposed to humid air. Vials are usually sealed under vacuum or inert gas with rubber stoppers and aluminum crimps. Storage temperatures range from room temperature to refrigerated or frozen conditions depending on the material. Stability studies track potency, moisture, and physical form over time. Accelerated conditions can reveal sensitivity but may not predict long-term behavior.
| Property | Value | Notes |
|---|---|---|
| Primary phase change | Sublimation | Ice changes directly to vapor under reduced pressure |
| Typical chamber pressure | 0.01–0.5 mbar (1–50 Pa) | Below the triple point of water; product-specific |
| Typical product temperature during primary drying | −40 °C to −10 °C | Kept below collapse temperature |
| Typical residual moisture | 0.5–3% w/w | Target range varies by formulation and use |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilization is the US spelling |
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
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.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
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.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
An yttrium–barium cuprate, YBa2Cu3O7−x (or Y123), was the first superconductor found above liquid nitrogen boiling point. The three different metals in the YBa2Cu3O7 superconductor are in the mole ratio of 1 to 2 to 3 for yttrium to barium to copper, respectively; hence, this particular superconductor has often been referred to as the 123 superconductor. The unit cell of YBa2Cu3O7 consists of three perovskite unit cells, which is pseudocubic, nearly orthorhombic. The other superconducting cuprates have another structure: they have a tetragonal cell. Each perovskite cell contains a Y or Ba atom at the center: Ba in the bottom unit cell, Y in the middle one, and Ba in the top unit cell. Thus, Y and Ba are stacked in the sequence [Ba–Y–Ba] along the c-axis. All corner sites of the unit cell are occupied by Cu, which has two different coordinations, Cu(1) and Cu(2), with respect to oxygen. There are four possible crystallographic sites for oxygen: O(1), O(2), O(3) and O(4). The coordination polyhedra of Y and Ba with respect to oxygen are different. The tripling of the perovskite unit cell leads to nine oxygen atoms, whereas YBa2Cu3O7 has seven oxygen atoms and, therefore, is referred to as an oxygen-deficient perovskite structure. The structure has a stacking of different layers: (CuO)(BaO)(CuO2)(Y)(CuO2)(BaO)(CuO). One of the key feature of the unit cell of YBa2Cu3O7−x (YBCO) is the presence of two layers of CuO2. The role of the Y plane is to serve as a spacer between two CuO2 planes. In YBCO, the Cu–O chains are known to play an important role for superconductivity.
dyspepsia of a non-ulcer/dysmotility type (gastric "fullness", discomfort, and possible pain) gastroparesis (delayed gastric emptying) anorexia heartburn regurgitation bloating nausea and vomiting other possible gastric, prolactin, or dopamine related conditions Itopride was shown to significantly improve symptoms in patients with functional dyspepsia and motility disorders in placebo-controlled trials. These studies concluded that the reduction in the severity of symptoms of functional dyspepsia after 8 weeks of treatment with itopride indicated that itopride was significantly superior to placebo and that itopride yielded a greater rate of response than placebo in significantly reducing pain and fullness.
=== Breeding === In India, from where moringa most likely originated, the diversity of wild types gives a good basis for breeding programs. In countries where moringa has been introduced, the diversity is usually much smaller among the cultivar types. Locally well-adapted wild types, though, can be found in most regions. Because moringa is cultivated and used in different ways, breeding aims for an annual or a perennial plant are obviously different. The yield stability of fruits is an important breeding aim for the commercial cultivation in India, where moringa is cultivated as an annual. On less favorable locations, perennial cultivation has big advantages, such as less erosion. In Pakistan, varieties have been tested for the nutritional composition of their leaves on different locations. India selects for a higher number of pods and dwarf or semidwarf varieties. Breeders in Tanzania, though, are selecting for higher oil content.
Sources: en.wikipedia.org
Kampo or Kanpō medicine (漢方医学, Kanpō igaku), often known simply as Kanpō (漢方; Japanese medicine) literally means "method from the Han period of Chinese history, but took on specific Japanese characteristics during the Edo period of Japanese history after 1600. One authority writes that Kampo medicine is not the same as modern traditional Chinese medicine (TCM). Japanese Kampo favors diagnostic methods that directly relate the symptoms to the therapy, rather than speculative concepts of traditional philosophy, such as Yin and Yang and the theory of the five elements. Under modern Japanese medical law, it is possible for doctors to perform acupuncture and massage, but because there is a separate law regarding acupuncture and massage, these treatments are mainly performed by massage therapists, acupuncturists, and moxibustion practitioners.
Byzantine music is eclectically descended from early Christian plainsong, Jewish music, and a variety of ancient music; its exact connections to ancient Greek music remain uncertain. It included both sacred and secular traditions, but the latter is little known, whereas the former remains the central music of Eastern Orthodox liturgy into the 21st century. The empire's church music, known as Byzantine chant, was exclusively unaccompanied monodic vocal music, sung in Greek. From the 8th century, chant melodies were governed by the Oktōēchos framework, a set of eight modes—echos (ἦχος; lit. 'sound')—which each provide predetermined motivic formulae for composition. These formulae were chosen for proper text stress and occasionally for text painting, then collated through centonisation into hymns or psalms. Byzantine chant was central to the Byzantine Rite; the earliest music was not notated, including early monostrophic short hymns like the troparion. Proto-Ekphonetic notation (9th century onwards) marked simple recitation patterns. The neumatic Palaeo-Byzantine notation system emerged in the 10th century, and the Middle Byzantine "Round Notation" from the mid-12th century onwards is the first fully diastematic scheme. Several major forms developed alongside well-known composers: the long kontakion (5th century onwards), popularised by Romanos the Melodist; the also-extensive kanōn (late 7th century onwards), developed by Andrew of Crete; and the shorter sticheron (at least 8th century onwards), championed by Kassia.
Two abnormal proteins define the pathology of Alzheimer's disease: amyloid beta protein (Aβ) in amyloid plaques and tau protein in neurofibrillary tangles. These proteins share two features that promote their ability to cause disease: They both become abnormal by misfolding, that is, by assuming a shape that is rich in beta sheets; and they proliferate in the brain by the prion-like mechanism of seeded protein aggregation. The presence of these abnormal proteins in Alzheimer's disease has spawned two hypotheses of the proteopathic origin of the disease: The amyloid (or Aβ) hypothesis, and the tau hypothesis. The amyloid hypothesis, also known as the "amyloid cascade hypothesis" or "Aβ cascade hypothesis", holds that the accumulation of misfolded Aβ in the brain is the fundamental cause of Alzheimer's disease. In the amyloid cascade, the buildup of abnormal Aβ leads to tauopathy and eventually the complex degenerative changes of advanced Alzheimer's disease. Abnormal Aβ is thought to damage the brain by directly interacting with cells, as well as indirectly, for example by causing oxidative stress and neuroinflammation. The amyloid hypothesis is supported by evidence from genetics and biomarkers. All autosomal dominant genetic causes of Alzheimer's disease affect either the amyloid precursor protein (APP) on chromosome 21 or the enzymes that generate Aβ, known as presenilin 1 and presenilin 2.
Sources: en.wikipedia.org
An endolith or endolithic is an organism (archaeon, bacterium, fungus, lichen, algae, sponge, or amoeba) that is able to acquire the necessary resources for growth in the inner part of a rock, mineral, coral, animal shells, or in the pores between mineral grains of a rock. Many are extremophiles, living in places long considered inhospitable to life. The distribution, biomass, and diversity of endolith microorganisms are determined by the physical and chemical properties of the rock substrate, including the mineral composition, permeability, the presence of organic compounds, the structure and distribution of pores, water retention capacity, and the pH. Normally, the endoliths colonize the areas within lithic substrates to withstand intense solar radiation, temperature fluctuations, wind, and desiccation. They are of particular interest to astrobiologists, who theorize that endolithic environments on Mars and other planets constitute potential refugia for extraterrestrial microbial communities.
embryo The developing organism that represents the earliest stages of development in all sexually reproducing multicellular organisms, traditionally encompassing the period after fertilization of an egg cell and formation of the zygote but prior to birth, hatching, or metamorphosis. During this period, known as embryonic development, the single-cell zygote is transformed by repeated cell divisions and rearrangements into a series of increasingly complex multicellular structures. For humans, the term "embryo" is only used until the ninth week after conception, after which time the embryo is known as a foetus; for most other organisms, including plants, "embryo" can be used more broadly to describe any early stage of the life cycle.
Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes, this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved. The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones, making ionic bonds to the acidic sugar-phosphate backbone of the DNA, and are thus largely independent of the base sequence. Chemical modifications of these basic amino acid residues include methylation, phosphorylation, and acetylation. These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to transcription factors and changing the rate of transcription. Other non-specific DNA-binding proteins in chromatin include the high-mobility group proteins, which bind to bent or distorted DNA. These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up chromosomes. A distinct group of DNA-binding proteins is the DNA-binding proteins that specifically bind single-stranded DNA.
Sources: en.wikipedia.org
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.
The process has three main stages: freezing, primary drying, and secondary drying. Freezing sets the ice structure, primary drying removes free ice, and secondary drying removes bound water. Each stage uses specific temperature, pressure, and time settings.
No, it is a drying method rather than a sterilization method. Removing water can limit microbial growth, but it does not reliably kill microorganisms. Sterility must come from separate steps such as filtration, heat treatment, or aseptic processing.
Karl Fischer titration is a common method, using coulometric or volumetric detection. Thermogravimetric analysis can also measure weight loss on heating. Results depend on sample handling because the dried solid can absorb moisture quickly.