A practical reference on glass transition: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-12-22 and is reviewed periodically as new material appears.
Analytical methods for lyophilized solids must account for the low moisture content and the fragile cake. Karl Fischer titration is widely used for water content, while near-infrared spectroscopy can measure moisture non-destructively in sealed containers. X-ray diffraction and modulated differential scanning calorimetry help identify crystalline or amorphous phases. Residual solvent analysis may be needed if organic solvents were used during formulation. The combination of these methods supports batch release and long-term stability assessment.
Lyophilized products are typically stored as sealed solids in vials or syringes. Moisture ingress is a major concern because many dried cakes are hygroscopic and can lose stability when exposed to humid air. Storage temperature depends on the formulation; some products are kept refrigerated, while others are stable at room temperature. Container closure integrity and headspace moisture are often monitored. Light protection may also be required for some photosensitive materials.
Quality control for lyophilized materials includes visual inspection, residual moisture measurement, and reconstitution testing. Cake appearance can reveal process problems such as collapse, shrinkage, or meltback, although appearance alone does not prove potency. Residual moisture is commonly measured by Karl Fischer titration or by loss on drying. Reconstitution time is checked because a slow or incomplete dissolve can indicate a change in pore structure. Stability studies track these attributes over time under defined temperature and humidity conditions.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
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.
| Property | Value | Notes |
|---|---|---|
| Storage temperature | 2–8 °C or 20–25 °C | Depends on product stability; some require frozen storage. |
| Moisture content | 0.5–3% w/w | Higher values may reduce stability; target set per product. |
| Moisture method | Karl Fischer titration | Coulometric for low levels; volumetric for higher levels. |
| Cake appearance | Uniform, intact, no collapse | Visual inspection is qualitative and not a potency measure. |
| Reconstitution time | Seconds to several minutes | Depends on cake density, excipients, and diluent. |
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
Stability studies examine how temperature, humidity, and time influence a lyophilized product. Accelerated conditions provide early information about degradation pathways, while long-term studies support shelf-life claims. The glass transition temperature of the dried formulation can indicate its physical stability, and storage above this temperature may increase molecular mobility and lead to collapse or aggregation. Container closure integrity also matters because moisture or oxygen ingress can degrade the product, so vial stoppers and seals are part of the quality system.
Handling and storage practices aim to keep the cake intact and dry. Vials are typically stored upright at controlled temperatures, often between 2 °C and 8 °C or at -20 °C for longer-term use. Reconstitution involves adding a suitable diluent and gently mixing until the solid dissolves. Shaking or rapid injection of diluent can create foam or damage sensitive molecules. Once reconstituted, the product may require refrigeration and use within a defined period.
Residual moisture is a key quality attribute for lyophilized products. Water that remains after secondary drying can affect chemical stability, cake structure, and shelf life. Karl Fischer titration is a common method for measuring water content in the dried solid. The target range varies by product, but many biologics are dried to between 0.5% and 3% water by weight. Acceptable limits are set during development and confirmed by stability studies.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture and oxygen exposure. The container closure system matters because stoppers and seals can allow moisture ingress over time. Storage conditions are selected from stability studies that track potency, cake appearance, and reconstitution behavior. Many freeze-dried materials are kept at controlled room temperature, while some require refrigeration or protection from light.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
Quality assessment of a lyophilized product includes cake appearance, residual moisture, reconstitution time, and container closure integrity. A uniform, porous cake suggests that freezing and drying stayed within the formulation's design space. Cracks, shrinkage, meltback, or a glassy film can indicate thermal abuse or a formulation problem. Analysts also test for subvisible particles and sterility when the product requires those specifications. Visual inspection alone cannot confirm biological activity or chemical stability, so it is combined with analytical methods.
Stability programs monitor lyophilized products under defined temperature and humidity conditions over time. Real-time studies at recommended storage conditions are the reference, while accelerated studies provide early signals of degradation pathways. Because a dry cake can still undergo oxidation, hydrolysis, or aggregation, stability depends on residual moisture, excipients, and container headspace. Open questions include how best to predict long-term stability from short accelerated runs and how vial-to-vial variability affects shelf life. Current guidance treats these predictions as product-specific rather than universally generalizable.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
Bats produce calls to attract mates, find roost partners and defend resources. These calls are typically low-frequency and wide-travelling. Species like Daubenton's bat (Myotis daubentonii) are capable of lowering their vocal range in a manner similar to a death growl, which they use in conflict with other individuals. Mexican free-tailed bats are one of the few species to "sing" like birds. Males sing to attract females, and their songs consist of chirps, trills and buzzes, the first of which has distinct "A" and "B" syllables. Bat songs are highly stereotypical but differ in syllable number, phrase order, and phrase repetitions between individuals. Among greater spear-nosed bats (Phyllostomus hastatus), females produce loud, broadband calls among their roost mates to form group cohesion. Roosting groups have their own distinct calls, and these may arise from vocal learning. In a study on captive Egyptian fruit bats, 70% of the directed calls could be identified by the researchers as to which individual bat made it, and 60% could occur in four contexts: fights over food, quarrelling for a sleeping position, female aggression toward amorous males, and arguing between perched neighbours. The animals made slightly different sounds when communicating with different individual bats, especially those of the opposite sex. In the highly sexually dimorphic hammer-headed bat (Hypsignathus monstrosus), males display to females with a "deep, resonating, monotonous call". Bats in flight make vocal signals for traffic control.
nausea 26% (9%) somnolence 23% (9%) dry mouth 18% (12%) headache 18% (17%) asthenia (weakness) 15% (6%) constipation 14% (9%) dizziness 13% (6%) insomnia 13% (6%) diarrhea 12% (8%) sweating 11% (2%) tremor 8% (2%) loss of appetite 6% (2%) nervousness 5% (3%) blurred vision 4% (1%) paraesthesia 4% (2%) hypomania 1% (0.3%) sexual dysfunction (≥10% incidence) Most of these adverse effects are transient and go away with continued treatment. Central and peripheral 5-HT3 receptor stimulation is believed to result in the gastrointestinal effects observed with SSRI treatment. Compared to other SSRIs, it has a lower incidence of diarrhea, but a higher incidence of anticholinergic effects (e.g., dry mouth, constipation, blurred vision, etc.), sedation/somnolence/drowsiness, sexual side effects, and weight gain. Due to reports of adverse withdrawal reactions upon terminating treatment, the Committee for Medicinal Products for Human Use at the European Medicines Agency recommends gradually reducing over several weeks or months if the decision to withdraw is made. See also Discontinuation syndrome (withdrawal). Mania or hypomania may occur in 1% of patients with depression and up to 12% of patients with bipolar disorder. This side effect can occur in individuals with no history of mania, but it may be more likely to occur in those with bipolar disorder or with a family history of mania. Paroxetine is described as a 'hepatoxic agent' and has been associated with hepatoxicity and jaundice.
== Medical uses == In the European Union, remdesivir is indicated for the treatment of COVID‑19 in adults and adolescents (aged twelve years and older with body weight at least 40 kilograms (88 lb)) with pneumonia requiring supplemental oxygen and for adults who do not require supplemental oxygen and who are at increased risk of progressing to severe COVID‑19. In the United States, remdesivir is indicated for the treatment of COVID‑19 in people 28 days of age and older and weighing at least 3 kilograms (6.6 lb) who are hospitalized; or not hospitalized and have mild-to-moderate COVID‑19, and are at high risk for progression to severe COVID‑19, including hospitalization or death. In November 2020, the FDA issued an emergency use authorization (EUA) for the combination of baricitinib with remdesivir, for the treatment of suspected or laboratory confirmed COVID‑19 in hospitalized people two years of age or older requiring supplemental oxygen, invasive mechanical ventilation, or extracorporeal membrane oxygenation (ECMO). In Australia, it is approved for those aged four weeks of age and older with a body weight at least 3 kilograms (6.6 lb) with pneumonia requiring supplemental oxygen or those aged four weeks of age and older with body weight at least 40 kilograms (88 lb) who do not require supplemental oxygen and who are at high risk of progressing to severe COVID‑19. In 2024, a retrospective study found treatment with the antiviral remdesivir plus dexamethasone was associated with fewer deaths in hospitalized COVID-19 patients compared to dexamethasone alone.
An original recommendation for water intake in 1945 by the Food and Nutrition Board of the U.S. National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods." The latest dietary reference intake report by the U.S. National Research Council in general recommended, based on the median total water intake from US survey data (including food sources): 3.7 litres (0.81 imp gal; 0.98 US gal) for men and 2.7 litres (0.59 imp gal; 0.71 US gal) of water total for women, noting that water contained in food provided approximately 19% of total water intake in the survey. Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. The US Institute of Medicine recommends that, on average, men consume 3 litres (0.66 imp gal; 0.79 US gal) and women 2.2 litres (0.48 imp gal; 0.58 US gal); pregnant women should increase intake to 2.4 litres (0.53 imp gal; 0.63 US gal) and breastfeeding women should get 3 liters (12 cups), since an especially large amount of fluid is lost during nursing. Also noted is that normally, about 20% of water intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through urine and feces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well. Humans require water with few impurities.
INS: The insulin gene (INS) on chromosome 11p15 is one of the earliest identified non-HLA genes linked to T1D. A variable number tandem repeat (VNTR) polymorphism in the promoter region of the insulin gene affects its thymic expression, with certain alleles reducing the ability to develop immune tolerance to insulin, a key autoantigen in T1D. PTPN22: This gene encodes a protein tyrosine phosphatase involved in T-cell receptor signaling. A common single-nucleotide polymorphism (SNP), R620W, in the PTPN22 gene is associated with an increased risk of T1D and other autoimmune diseases, suggesting its role in modulating immune responses. IL2RA: The interleukin-2 receptor alpha (IL2RA) gene, located on chromosome 10p15, plays a crucial role in regulating immune tolerance and T-cell activation. Variants in IL2RA affect the susceptibility to T1D by altering the function of regulatory T-cells, which help maintain immune homeostasis. CTLA4: The cytotoxic T-lymphocyte-associated protein 4 (CTLA4) gene is another immune-related gene associated with T1D. CTLA4 acts as a negative regulator of T-cell activation, and certain variants are linked to impaired immune regulation and a higher risk of autoimmunity. T1D is considered a polygenic disease, meaning that multiple genes contribute to its development. While individual genes confer varying degrees of risk, it is the combination of several genetic factors, along with environmental triggers, that ultimately leads to disease onset.
Sources: en.wikipedia.org
Estradiol acts primarily as an agonist of the estrogen receptor (ER), a nuclear steroid hormone receptor. There are two subtypes of the ER, ERα and ERβ, and estradiol potently binds to and activates both of these receptors. The result of ER activation is a modulation of gene transcription and expression in ER-expressing cells, which is the predominant mechanism by which estradiol mediates its biological effects in the body. Estradiol also acts as an agonist of membrane estrogen receptors (mERs), such as GPER (GPR30), a recently discovered non-nuclear receptor for estradiol, via which it can mediate a variety of rapid, non-genomic effects. Unlike the case of the ER, GPER appears to be selective for estradiol, and shows very low affinities for other endogenous estrogens, such as estrone and estriol. Additional mERs besides GPER include ER-X, ERx, and Gq-mER. ERα/ERβ are in inactive state trapped in multimolecular chaperone complexes organized around the heat shock protein 90 (HSP90), containing p23 protein, and immunophilin, and located in majority in cytoplasm and partially in nucleus. In the E2 classical pathway or estrogen classical pathway, estradiol enters the cytoplasm, where it interacts with ERs. Once bound E2, ERs dissociate from the molecular chaperone complexes and become competent to dimerize, migrate to nucleus, and to bind to specific DNA sequences (estrogen response element, ERE), allowing for gene transcription which can take place over hours and days.
=== Introns can be mobile genetic elements === Some self-splicing introns can spread through a population of organisms by "homing", inserting copies of themselves into genes at sites that previously lacked an intron. Because they are self-splicing (that is, they remove themselves at the RNA level from genes into which they have inserted), these sequences represent transposons that are genetically silent, i.e. they do not interfere with the expression of the gene into which they become inserted. These introns can be regarded as examples of selfish DNA. Some mobile introns encode homing endonucleases, enzymes that initiate the homing process by specifically cleaving double-stranded DNA at or near the intron-insertion site of alleles lacking an intron. Mobile introns are frequently members of either the group I or group II families of self-splicing introns.
Northern: The northern section runs from the Canadian province of Newfoundland and Labrador to the Hudson River. It includes the Long Range Mountains and Annieopsquotch Mountains on the island of Newfoundland, the French Territorial Collectivity of Saint-Pierre and Miquelon southwest of Newfoundland, Chic-Choc Mountains and Notre Dame Range in Quebec and New Brunswick, scattered elevations and small ranges elsewhere in Nova Scotia and New Brunswick, the Longfellow Mountains in Maine, the White Mountains in New Hampshire, the Green Mountains in Vermont, and The Berkshires in Massachusetts, and Connecticut, the Metacomet Ridge Mountains in Connecticut and south-central Massachusetts, and the Adirondack Mountains in New York are all part of the Appalachian Mountains as defined by the governments of Canada and the United States.Mountains of the Long Range in Newfoundland, such as the Cabox and Gros Morne, reach heights of nearly 2,700 ft (800 m). In the Chic-Choc and Notre Dame Mountain ranges in Quebec, the higher summits rise above 4,000 ft (1,200 m) in elevation. Isolated peaks and small ranges in Nova Scotia and New Brunswick vary from 1,000 to 2,700 ft (300 to 800 m). In Maine, several peaks exceed 4,000 ft (1,200 m), including Mount Katahdin at 5,267 feet (1,605 m).
== Early life == Simco was born on January 29, 1982, in Houston, Texas, to Anita Isaacs, a maid, and Ronald Simco, a Vietnam War veteran with severe post-traumatic stress disorder, who worked various jobs, including as a police officer and Walmart manager. His mother grew up in Shaker Heights, Ohio, descending from a family of German Jews and Lithuanian Jews that included several survivors and victims of the Holocaust. Riff Raff is the second of four siblings. He and his family lived in Copperfield, a suburb 25 miles northwest of Houston. Growing up he was obsessed with basketball, playing frequently with other children in his neighborhood. The Simcos had moved to nearby Stone Creek. He attended Langham Creek High School, where he was shooting guard on his school's basketball team, before dropping out in his senior year. Shortly thereafter he obtained his GED. After his parents divorced, his father was diagnosed with tonsil cancer and the family moved to Duluth, Minnesota, to get his father out of the heat into a cooler environment. For a time, Riff Raff and his siblings were shuttled back and forth between Duluth and Houston, where their mother remained. In 2001, he enrolled at Hibbing Community College in Hibbing, Minnesota, where he played on the basketball team for a month and majored in liberal arts. Feeling out of place, he dropped out in 2003 and moved back to Houston, where he painted cars in the in-vogue "candy-colored" style and gradually built his new identity. He eventually relocated to Los Angeles and began to take his rapping career seriously.
Lee H, Iglewski WJ (1984). "Cellular ADP-ribosyltransferase with the same mechanism of action as diphtheria toxin and Pseudomonas toxin A". Proc. Natl. Acad. Sci. U.S.A. 81 (9): 2703–7. Bibcode:1984PNAS...81.2703L. doi:10.1073/pnas.81.9.2703. PMC 345138. PMID 6326138. Ueda K, Hayaishi O (1985). "ADP-ribosylation". Annu. Rev. Biochem. 54 (1): 73–100. doi:10.1146/annurev.bi.54.070185.000445. PMID 3927821.
Sources: en.wikipedia.org
The supernatant contains a mitogenic factor, a mitosis promoting factor, that is characterized heat and trypsin sensitivity, both of which characterize it as a peptide. Treatment of Schwann cells with the collected supernatant shows that it is a mitogenic factor and thus plays an important role in the proliferation of Schwann cells. Macrophages are also involved in the secretion factors that promote nerve regeneration. Macrophages secrete not only interleukin-1, a cytokine that induces expression of nerve growth factor (NGF) in Schwann cells but also an interleukin-1 receptor antagonist (IL-1ra). Expression of IL-1ra in mice with transected sciatic nerves via implantation of a tube releasing IL-1ra showed the regrowth of fewer myelinated and unmyelinated axons. Macrophage secretion of interleukin-1 is involved in stimulation of nerve regeneration.
A large group of primarily lichenized fungi (the subclass Ostropomycetidae) apparently lost the ability to form lichens early in its history, reverting to a saprotrophic lifestyle. Later, some descendants regained a photobiont and lichenized again. This finding contradicts older assumptions that once a fungus became obligately lichenized it could never revert. Lineages with complex thalli, especially those bearing cyanobacterial cephalodia, show higher estimated extinction rates: they diversify rapidly but are more prone to die out, perhaps because of ecological specialization. Such large-scale studies now link geological and climatic shifts, for example, the spread of angiosperm forests in the Late Cretaceous–Early Paleogene, to bursts of lichen diversification, revealing a more intricate evolutionary history. In simple terms, this means lichens diversified in bursts when new habitats (like forests with lots of new tree bark) became available. New high-throughput techniques are also solving smaller-scale questions once thought intractable. 'Museomics' now retrieves DNA from old, fragmented specimens. For instance, Leavitt and colleagues (2019) shotgun-sequenced decades-old historical type specimens of the Rhizoplaca melanophthalma group. From three crustose thalli they recovered more than a thousand gene regions, sufficient to position each specimen in a phylogenomic tree and match them with modern material. The data showed one specimen was the distinct species R.
=== Francium perchlorate === Francium perchlorate is produced by the reaction of francium chloride and sodium perchlorate. The francium perchlorate coprecipitates with caesium perchlorate. This coprecipitation can be used to isolate francium, by adapting the radiocaesium coprecipitation method of Lawrence E. Glendenin and C. M. Nelson. However, this method is unreliable in separating thallium, which also coprecipitates with caesium. Francium perchlorate's entropy is expected to be 42.7 e.u (178.7 J mol−1 K−1).
=== Phase III ACHIEVE-1 trial === In April 2025, results from a phase III clinical trial involving 559 people with type 2 diabetes who took an oral orforglipron pill or a placebo daily for 40 weeks showed that orforglipron produced a reduction of hemoglobin A1C level by 1.3 to 1.6 percentage points from a starting level of 8%. More than 65% of participants taking the highest dose of orforglipron achieved a reduction of hemoglobin A1C level by more than or equal to 1.5 percentage points, bringing them into the non-diabetic range as defined by the American Diabetes Association. People taking the highest dose of the pill lost 8% of their weight, or around 16 lb (7.3 kg), on average after 40 weeks. In its press release, Lilly noted that the subjects' weight loss had not yet plateaued at the time the trial concluded, and suggested that this indicated that greater weight reduction would ultimately be achieved with extended therapy. Side effects were similar to those seen with other GLP-1 agonists, and no significant liver problems were observed.
Sources: en.wikipedia.org
Most lyophilized products are stored in sealed containers at controlled temperature and humidity. Some require refrigeration, while others are stable at room temperature. Protection from light and moisture is often necessary.
Cake collapse indicates that the porous structure was lost during drying. It can result from excessive product temperature or an unsuitable formulation. Collapsed cakes may have slower reconstitution and are often rejected by visual inspection.
Residual moisture affects the chemical and physical stability of a lyophilized solid. High moisture can promote degradation, aggregation, or cake shrinkage. The acceptable range is set for each product based on stability data.
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.