This is a working overview of Stability study, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-26. Anything still debated is marked as such rather than presented as settled.
Regulatory expectations for lyophilized products focus on consistent manufacture and documented stability. Batches are often monitored for moisture, appearance, potency, and sterility where applicable. Process parameters such as shelf temperature, chamber pressure, and drying time are recorded and controlled within validated ranges. Open questions remain about how best to predict long-term stability from short accelerated studies, especially for complex biologics. Variations in freezing rate and ice crystal size can produce differences that are not always visible but may affect performance.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture uptake. Residual water content is measured because small changes can alter chemical stability and cake appearance. Storage temperature depends on the material; many biological products are kept at 2–8 °C, while some require −20 °C or colder. Exposure to ambient humidity during handling can cause the porous solid to absorb water and collapse. Container closures and stoppers are therefore selected for low moisture transmission and compatibility.
Quality control for lyophilized materials includes visual inspection of the cake, measurement of residual moisture, and tests for reconstitution time. An acceptable cake is typically uniform and may be slightly porous; shrinkage, meltback, or cracks can indicate process deviations. Analytical methods such as Karl Fischer titration, thermogravimetric analysis, and near-infrared spectroscopy quantify water content. Reconstitution time is recorded because a very slow or incomplete dissolution can signal collapse or aggregation. Stability studies compare samples stored under defined temperature and humidity conditions over months or years.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 2–8 °C | Common for biological materials; some require −20 °C or colder |
| Residual moisture specification | 0.5–3.0% w/w | Product-specific; measured after drying |
| Common moisture method | Karl Fischer titration | Coulometric or volumetric; detects water content |
| Cake appearance | Uniform and porous | Collapse, meltback, or cracks are deviations |
| Reconstitution time | Seconds to several minutes | Depends on formulation, cake structure, and diluent |
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
Quality control for lyophilized products includes appearance, cake structure, reconstitution time, pH, residual moisture, and potency. Residual moisture is a key attribute because excess water can reduce stability, while excessively low moisture may cause structural changes or aggregation in some systems. Stability studies compare real-time and accelerated conditions to estimate shelf life. Analytical methods must be validated for the specific matrix, container, and moisture range. Sterility and container integrity are also monitored for sterile products.
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.
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.
=== Ways of ptaquiloside exposure === Main routes that can lead to human exposure to the toxic effects of bracken fern include ingestion of the plant (particularly the croziers and young fronds), inhalation of the airborne spores, consumption of the milk and meat of affected animals, and drinking ptaquiloside contaminated water.
=== Chalcogen === Serine, homoserine, O-methylhomoserine and O-ethylhomoserine possess a hydroxymethyl, hydroxyethyl, O-methylhydroxymethyl and O-methylhydroxyethyl side chain; whereas cysteine, homocysteine, methionine and ethionine possess the thiol equivalents. The selenol equivalents are selenocysteine, selenohomocysteine, selenomethionine and selenoethionine. Amino acids with the next chalcogen down are also found in nature: several species such as Aspergillus fumigatus, Aspergillus terreus, and Penicillium chrysogenum in the absence of sulfur are able to produce and incorporate into protein tellurocysteine and telluromethionine.
The numbers 1.930 and 0.537 are phenomenological; these specific values provide a fairly good fit to the data. The product Re√fD (called the "friction Reynolds number") can be considered, like the Reynolds number, to be a (dimensionless) parameter of the flow: at fixed values of Re√fD, the friction factor is also fixed. In the Kármán–Prandtl resistance equation, fD can be expressed in closed form as an analytic function of Re through the use of the Lambert W function:
The preparation of other cuprates is more difficult than the YBCO preparation. They also have a different crystal structure: they are tetragonal where YBCO is orthorhombic. Problems in these superconductors arise because of the existence of three or more phases having a similar layered structure. Moreover, the crystal structure of other tested cuprate superconductors are very similar. Like YBCO, the perovskite-type feature and the presence of simple copper oxide (CuO2) layers also exist in these superconductors. However, unlike YBCO, Cu–O chains are not present in these superconductors. The YBCO superconductor has an orthorhombic structure, whereas the other high-Tc superconductors have a tetragonal structure. There are three main classes of superconducting cuprates: bismuth-based, thallium-based and mercury-based. The second cuprate by practical importance is currently BSCCO, a compound of Bi–Sr–Ca–Cu–O. The content of bismuth and strontium creates some chemical issues. It has three superconducting phases forming a homologous series as Bi2Sr2Can−1CunO4+2n+x (n=1, 2 and 3). These three phases are Bi-2201, Bi-2212 and Bi-2223, having transition temperatures of 20 K (−253.2 °C), 85 K (−188.2 °C) and 110 K (−163 °C), respectively, where the numbering system represent number of atoms for Bi Sr, Ca and Cu respectively. The two phases have a tetragonal structure which consists of two sheared crystallographic unit cells.
== Diagnosis == Fasting Insulin levels in blood may be measured as this can be elevated in the presence of normal glucose. Diagnosis is often made by checking normal levels of glucose that exceed 1.7 mmol/L (30 mg/dL) when 1 mg of glucagon is administered IM or IV. In addition, urine samples or blood samples are also used to check levels of ketones and low free fatty acids. After diagnosis, most people are required to continue regular check ups for evaluations.
Sources: en.wikipedia.org
After structural comparison with different species of Penicillium, Fleming believed that his specimen was Penicillium chrysogenum, a species described by an American microbiologist Charles Thom in 1910. Charles John Patrick La Touche, an Irish botanist, had recently joined St Mary's as a mycologist, and he identified the specimen as Penicillium rubrum, the identification used by Fleming in his publication. In 1931, Thom re-examined different Penicillia, including that of Fleming's specimen, and he came to the conclusion that Fleming's specimen was P. notatum, a member of the P. chrysogenum series. From then on, Fleming's mould was synonymously referred to as P. notatum and P. chrysogenum. To resolve the confusion, the Seventeenth International Botanical Congress held in Vienna, Austria, in 2005 formally adopted P. chrysogenum as the name. Whole-genome sequence and phylogenetic analysis in 2011 revealed that Fleming's mould belongs to P. rubens, a species described by Belgian microbiologist Philibert Biourge in 1923. The source of the fungal contamination in Fleming's experiment remained the subject of speculation for several decades. Fleming suggested in 1945 that the fungal spores came through the window facing Praed Street, but was disputed by his co-workers, who testified much later that Fleming's laboratory window was kept shut, and Fleming was unable to reach the window to open it. A consensus developed that the mould had come from La Touche's laboratory, a floor below Fleming's, and that spores had drifted in through the open doors.
Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. This includes use as an eye ointment to treat conjunctivitis. By mouth or by injection into a vein, it is used to treat meningitis, plague, cholera, and typhoid fever. Its use by mouth or by injection is only recommended when safer antibiotics cannot be used. Monitoring both blood levels of the medication and blood cell levels every two days is recommended during treatment. Common side effects include bone marrow suppression, nausea, and diarrhea. The bone marrow suppression may result in death. To reduce the risk of side effects treatment duration should be as short as possible. People with liver or kidney problems may need lower doses. In young infants, a condition known as gray baby syndrome may occur which results in a swollen stomach and low blood pressure. Its use near the end of pregnancy and during breastfeeding is typically not recommended. Chloramphenicol is a broad-spectrum antibiotic that typically stops bacterial growth by stopping the production of proteins. Chloramphenicol was discovered after being isolated from Streptomyces venezuelae in 1947. Its chemical structure was identified and it was first synthesized in 1949. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
== Discovery == Before the discovery of the ubiquitin–proteasome system, protein degradation in cells was thought to rely mainly on lysosomes, membrane-bound organelles with acidic and protease-filled interiors that can degrade and then recycle exogenous proteins and aged or damaged organelles. However, work by Joseph Etlinger and Alfred L. Goldberg in 1977 on ATP-dependent protein degradation in reticulocytes, which lack lysosomes, suggested the presence of a second intracellular degradation mechanism. This was shown in 1978 to be composed of several distinct protein chains, a novelty among proteases at the time. Later work on modification of histones led to the identification of an unexpected covalent modification of the histone protein by a bond between a lysine side chain of the histone and the C-terminal glycine residue of ubiquitin, a protein that had no known function. It was then discovered that a previously identified protein associated with proteolytic degradation, known as ATP-dependent proteolysis factor 1 (APF-1), was the same protein as ubiquitin. The proteolytic activities of this system were isolated as a multi-protein complex originally called the multi-catalytic proteinase complex by Sherwin Wilk and Marion Orlowski. Later, the ATP-dependent proteolytic complex that was responsible for ubiquitin-dependent protein degradation was discovered and was called the 26S proteasome.
Lack of sufficient insulin (but enough to prevent ketosis) Poor kidney function Poor fluid intake (dehydration) Older age (50–70 years) Certain medical conditions (cerebral vascular injury, myocardial infarction, sepsis) Certain medications (glucocorticoids, beta-blockers, thiazide diuretics, calcium channel blockers, and phenytoin)
Leucotomy was first undertaken in 1935 under the direction of the Portuguese neurologist (and inventor of the term psychosurgery) António Egas Moniz. First developing an interest in psychiatric conditions and their somatic treatment in the early 1930s, Moniz conceived a new opportunity for recognition in the development of a surgical intervention on the brain as a treatment for mental illness.
Sources: en.wikipedia.org
On 7 August 2022, Petro was sworn in, becoming the country's first leftist president. Later that month, Colombia and Venezuela formally reestablished bilateral diplomatic relations. The 21 June 2026 election run-off vote ended in a win for right-wing candidate, Abelardo de la Espriella, taking 49.7% of the vote compared to 48.7% of left-wing Iván Cepeda. On 7 August 2026, Abelardo de la Espriella was sworn in as Colombia’s president.
α-Fluoromethylhistidine (α-FMH) is an irreversible specific inhibitor of histidine decarboxylase (HDC). It functions by forming a covalent linkage with a catalytic serine residue on the active site of HDC. Due to its efficacy in reducing histamine levels in tissue mast cells, it has many applications in the study of histaminergic systems. It has potent sleep-inducing effects in mice. In the central nervous systems of rats, α-FMH administration has been shown to cause impairments in long-term memory and learning. Additionally, injection of α-FMH has been shown to increase food intake, although the mechanism is believed to distinct from HDC inhibition, indicating that α-FMH may be involved in the regulation of non-histaminergic systems. A proposed mechanism involves the enhanced expression of neuropeptide Y (NPY) rather than HDC inhibition. α-FMH has also been shown to target isozymes of the glutathione S-transferase (GST) family. Due to the role of GSTs in detoxification, the efficacy of HDC inhibition by α-FMH in humans and its potential for the treatment of pathological conditions is subject to further research.
The heavy isotope plutonium-244 has a half-life long enough that extreme trace quantities should have survived primordially (from the Earth's formation) to the present, but so far experiments have not yet been sensitive enough to detect it. Both plutonium-239 and plutonium-241 are fissile, meaning they can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium-240 has a high rate of spontaneous fission, raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a plutonium sample's usability for weapons or its quality as reactor fuel, and the percentage of plutonium-240 determines its grade (weapons-grade, fuel-grade, or reactor-grade). Plutonium-238 has a half-life of 87.7 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred after the war.
== External links == Receptors, Corticotropin-Releasing Hormone at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Overview of all the structural information available in the PDB for UniProt: Q60748 (Mouse Corticotropin-releasing factor receptor 2) at the PDBe-KB.
NS Otto Hahn, the only European nuclear-powered civilian ship (1964); a crater on the Moon (shared with his namesake Friedrich von Hahn); and the asteroid 19126 Ottohahn; the Otto Hahn Prize of both the German Chemical and Physical Societies and the city of Frankfurt/Main; the Otto Hahn Medal – An Incentive for Young Scientists – and the Otto Hahn Award of the Max Planck Society; and the Otto Hahn Peace Medal in Gold of the United Nations Association of Germany (DGVN) in Berlin (1988). Proposals were made at various times, first in 1971 by American chemists, that the newly synthesised element 105 should be named hahnium in Hahn's honour, but in 1997 the IUPAC named it dubnium, after the Russian research centre in Dubna. In 1992 element 108 was discovered by a German research team, and they proposed the name hassium (after Hesse). In spite of the long-standing convention to give the discoverer the right to suggest a name, a 1994 IUPAC committee recommended that it be named hahnium. After protests from the German discoverers, the name hassium (Hs) was adopted internationally in 1997.
Sources: en.wikipedia.org
Most are held in sealed containers at controlled temperatures, often 2–8 °C, while some require frozen storage. Protection from moisture and light helps preserve the dry matrix. Exact conditions are set by the manufacturer or study protocol.
Cake collapse suggests the material exceeded its collapse temperature during drying or later absorbed moisture. It can lead to slower reconstitution, uneven moisture, and reduced stability. Appearance alone may not reveal the cause, so process records and moisture tests are used together.
Some residual moisture is common and may be acceptable within a defined range. Very low moisture can alter stability or increase brittleness, while high moisture promotes hydrolysis and microbial risk. Specifications are based on product-specific stability data.
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.