A practical reference on glass transition: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-14. Anything still debated is marked as such rather than presented as settled.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white porous cake | Color depends on formulation. |
| Typical storage temperature | 2–8 °C | Refrigerated for many biologics. |
| Residual moisture | <1% to 3% | Low moisture improves stability. |
| Container | Sealed glass vial | Often with rubber stopper and aluminum crimp. |
| Reconstitution time | Seconds to minutes | Varies with cake density and diluent. |
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.
Quality control for freeze-dried lots combines visual inspection with instrumental tests. Cake appearance, color, and shrinkage are recorded against a reference, while residual moisture is measured by Karl Fischer titration or loss on drying. Thermal analysis can reveal phase transitions and crystallization events, and X-ray diffraction distinguishes amorphous from crystalline solids. Microbiological tests and container closure integrity checks are also routine for sterile products. Analytical methods must be validated for the matrix, because excipients and low moisture can affect accuracy. Open questions include how best to predict long-term stability from short-term data.
Lyophilized solids are often hygroscopic, so handling occurs in controlled low-humidity areas or glove boxes when the material is exposed. Vials remain sealed with elastomeric stoppers and aluminum crimps until use, because airborne moisture can raise residual water and shorten shelf life. The porous cake is fragile and may crack, shrink, or powder during transport. Personnel typically avoid repeated warming and cooling of sealed units, which can draw moisture through closures. These practices aim to preserve the low water content achieved during drying.
Storage conditions depend on the formulation and the intended shelf life. Many pharmaceutical and biological freeze-dried products are kept at 2–8 °C, while some stable foods and reagents tolerate room temperature. Others require −20 °C or colder to slow chemical degradation or aggregation. Protection from light and oxygen is common because oxidation can continue in the dry state. Stability studies usually monitor potency, appearance, moisture, and reconstitution time over months or years. Predictions from accelerated studies are useful but may not fully capture real-time changes.
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.
Analytical methods for lyophilized materials include X-ray diffraction for crystallinity, differential scanning calorimetry for thermal transitions, and scanning electron microscopy for pore morphology. Moisture sorption analysis shows how the cake responds to humidity. These methods help distinguish amorphous from crystalline states and detect phase changes. Open questions remain about how pore structure changes during long-term storage and how best to predict collapse under varied conditions. Comparisons across studies are complicated by differences in formulation, cycle, and storage history.
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.
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.
Polycythemia (also spelt polycythaemia) is a medical condition suggested by a laboratory finding that the hematocrit (the volume percentage of red blood cells in the blood) and/or hemoglobin concentration are increased in the blood, although this finding is also present in capillary leak syndrome. Polycythemia is sometimes called erythrocytosis, and there is significant overlap in the two findings, but the terms are not the same: polycythemia describes any increase in hematocrit and/or hemoglobin, while erythrocytosis describes an increase specifically in the number of red blood cells in the blood. Polycythemia has many causes. It can describe an increase in the number of red blood cells ("absolute polycythemia") or a decrease in the volume of plasma ("relative polycythemia"). Absolute polycythemia can be due to genetic mutations in the bone marrow ("primary polycythemia"), physiological adaptations to one's environment, medications, and/or other health conditions. Laboratory studies such as serum erythropoeitin levels and genetic testing might be helpful to clarify the cause of polycythemia if the physical exam and patient history do not reveal a likely cause. Mild polycythemia on its own is often asymptomatic. Treatment for polycythemia varies, and typically involves treating its underlying cause. Treatment of primary polycythemia (see polycythemia vera) could involve phlebotomy, antiplatelet therapy to reduce risk of blood clots, and additional cytoreductive therapy to reduce the number of red blood cells produced in the bone marrow.
The EU adopted the listing of PFOA in Annex A of the Stockholm Convention with Commission Delegated Regulation (EU) 2020/784 of 8 April 2020 and introduced a limit value of 0,025 mg/kg for PFOA including its salts, and at 1 mg/kg for the individual PFOA-related compounds or a combination of those compounds. They also included some specific exemptions. Among them is a time-bound exemption for PFOA in fire-fighting foam.
=== Taxes === During his 2022 gubernatorial campaign, Moore repeatedly said that he did not anticipate raising taxes as governor, but said in September 2022 that he planned to work with the legislature to fix what he described as the state's "upside-down taxation system". In January 2024, he expressed openness to raising taxes to address the state's budget shortfall, but said that any conversation about taxes would have a "very high bar". That year, the legislature amended Moore's budget proposal, which included no tax increases, to add about $252 million in increases toward transportation-related fees and tobacco taxes to help pay for the Blueprint for Maryland's Future reforms and state transportation projects. In May 2022, following a spike in gas prices as a result of the Russo-Ukrainian War, Moore said he supported staving off automatic increases to the state's gas tax, arguing that voters needed immediate relief and later calling it a "regressive tax". He also expressed interest in eliminating either the state's estate or inheritance tax to make the state more attractive to retirees. In June 2023, Moore said he supported shifting transportation funding away from the state's gas tax as well as decoupling it from inflation, but opposed calling a special session to do so, instead preferring to pass tax reforms during the 2024 legislative session. In March 2026, Moore opposed a Republican proposal to implement a 30-day gas tax holiday following a spike in gas prices as a result of the 2026 Iran war.
compared four sterile wound-cleansing solutions (saline, Ringer's solution, Prontosan® and Octenisept®) using a wound coating model consisting of slides containing dried blood plasma or fibrin. The concentration of dissolved proteins was measured and the findings indicate that a surfactant containing solution (polyhexamethylene biguanide with betaine) (Prontosan®) was more effective than saline in removing the protein (adhered dried plasma or fibrin). The proteins in the antiseptic solution (Octenisept®) were denatured and became insoluble. The authors suggest this implies that the antiseptic solution is unsuitable as a 'general' wound cleanser and that its use should be restricted to infected wounds. In a double-blind, randomised, stratified, controlled, parallel-group study the influence of two antiseptics (octenidine, polyhexanide) versus a placebo of Ringer's solution on wound healing in a porcine model was conducted. Assessment of healing was recorded using planimetry and histopathology. At nine days post wounding, the octenidine-treated wounds demonstrated retarded contraction at significantly greater extent than placebo and polyhexanide. At days 18 and 28 the polyhexanide treated wounds supported contraction significantly more than placebo and octenidine. The polyhexanide treated wounds led to complete wound closure after 22.9 days, in comparison to the placebo octenidine treated wounds respectively, 24.1 days (p < 0.05) and 28.3 days (no statistical difference to placebo).
=== Cactus Club Cafe === Cactus Club Cafe is a chain of premium casual restaurants founded by Richard Jaffray and Scott Morison in Vancouver in 1988. Currently 31 restaurants are operated across Canada. As of 2022 "After 34 years, Richard Jaffray stepped aside as an owner and executive of Cactus Club Cafe, the restaurant chain he co-founded. The Fuller family, who have been silent partners since the company began, will become full owners." The Fuller family also owns Earls, Joey's, Cactus Club and Saltlik Steakhouse.
Sources: en.wikipedia.org
==== II. Nanoparticle and Liposome Attachment ==== Attachment of liposomes or nanoparticles to the exterior of the lipid microbubble has also been explored to increase microbubble payload. Upon microbubble destruction with ultrasound, these smaller particles can extravasate into the tumor tissue. Furthermore, through attachment of these particles to microbubbles as opposed to co-injection, the drug is confined to the blood stream instead of accumulating in healthy tissues, and the treatment is relegated to the location of ultrasound therapy. This microbubble modification is particularly attractive for Doxil, a lipid formulation of Doxorubicin already in clinical use. An analysis of nanoparticle infiltration due to microbubble destruction indicates that higher pressures are necessary for vascular permeability and likely improves treatment by promoting local fluid movement and enhancing endocytosis.
=== Biochemical and Pharmaceutical Properties === Research has demonstrated that various insect derived compounds exhibit antimicrobial, anti inflammatory, and wound healing properties. Maggot therapy, for instance, has been extensively studied for its ability to clean necrotic tissue and promote wound healing. According to studies published in PubMed and the NCBI Bookshelf, maggots of the Lucilia sericata species secrete enzymes that break down dead tissue while releasing antimicrobial peptides effective against antibiotic resistant bacteria. Also certain insect derived compounds, such as chitosan from insect exoskeletons, have shown promise in drug delivery systems and wound dressings due to their biocompatibility and hemostatic properties.
=== Food preparation === Niacin naturally found in food is susceptible to destruction from high heat cooking, especially in the presence of acidic foods and sauces. It is soluble in water, and so may also be lost from foods boiled in water.
Aang, in the animated series Avatar: The Last Airbender and The Legend of Korra was vegetarian. According to the show's creators, "Buddhism and Taoism have been huge inspirations behind the idea for Avatar." As shown in "The King of Omashu" and "The Headband", a notable aspect of Aang's character is his vegetarian diet, which is consistent with Buddhism, Hinduism, and Taoism. In the Brahmajala Sutra, a Buddhist code of ethics, vegetarianism is encouraged. Other fictional characters who are vegetarians include Count Duckula in Count Duckula, Beast Boy in Teen Titans and Teen Titans Go!, Lenore in Supernatural, and Norville "Shaggy" Rogers in the animated series What's New, Scooby Doo?. Before the latter animated series, Shaggy was known for having an "enormous appetite" earlier in the Scooby-Doo franchise. The decision to make Shaggy a vegetarian occurred after his voice actor, Casey Kasem, convinced the producers to do so, since he was a vegan who supported animal rights and opposed factory farming, saying he would refuse to voice Shaggy unless the character was vegetarian. An October 2019 South Park episode, "Let Them Eat Goo", featured a vegetarian character. Additionally, Steven Universe, the protagonist in the show Steven Universe and the limited epilogue series, Steven Universe Future, is a vegetarian. In the episode "Snow Day" of Steven Universe Future, Steven tells the Gems he lives with that he has been a vegetarian for a month, drinks protein shakes and mentions that he does "his own skincare routine."
== Clinical significance == The enzymes that make and use NAD+ and NADH are important in both pharmacology and the research into future treatments for disease. Drug design and drug development exploits NAD+ in three ways: as a direct target of drugs, by designing enzyme inhibitors or activators based on its structure that change the activity of NAD-dependent enzymes, and by trying to inhibit NAD+ biosynthesis. Because cancer cells utilize increased glycolysis, and because NAD enhances glycolysis, nicotinamide phosphoribosyltransferase (NAD salvage pathway) is often amplified in cancer cells. It has been studied for its potential use in the therapy of neurodegenerative diseases such as Alzheimer's and Parkinson's disease as well as multiple sclerosis. A placebo-controlled clinical trial of NADH (which excluded NADH precursors) in people with Parkinson's failed to show any effect. NAD+ is also a direct target of the drug isoniazid, which is used in the treatment of tuberculosis, an infection caused by Mycobacterium tuberculosis. Isoniazid is a prodrug and once it has entered the bacteria, it is activated by a peroxidase enzyme, which oxidizes the compound into a free radical form. This radical then reacts with NADH, to produce adducts that are very potent inhibitors of the enzymes enoyl-acyl carrier protein reductase, and dihydrofolate reductase. Since many oxidoreductases use NAD+ and NADH as substrates, and bind them using a highly conserved structural motif, the idea that inhibitors based on NAD+ could be specific to one enzyme is surprising.
Sources: en.wikipedia.org
Modafinil promotes wakefulness in narcoleptic dogs with non-functional orexin 2 receptors and in humans with type 1 narcolepsy, which is characterized by a marked loss of orexin-producing neurons. In contrast, the wake-promoting effects of modafinil are abolished in dopamine transporter knockout mice. The effects of modafinil on histamine, orexin, and other non-catecholaminergic systems may be secondary to its catecholaminergic effects.
=== 26 March === The SAF retook Khartoum International Airport and the Manshiya Bridge over the Blue Nile in Khartoum. It also retook the Tiba al-Hassanab camp in Jabal Aulia, which is described as the RSF's last stronghold in Khartoum and its main base in central Sudan. Al-Burhan visited the presidential palace in Khartoum and announced the liberation of the city, proclaiming that "Khartoum is free".
Frozen sectioning for intraoperative consultation Preparing tissue samples for flow cytometry, immunohistochemical (IHC) stains, genetic testing, microbiology culturing, and for various other laboratory evaluations Gross specimen photography Training pathology residents, PA fellows, and other pathology lab personnel (as needed) Fulfilling roles in managerial duties, instructional positions, and supervisory roles Research While many PAs are employed in hospitals, they may also gain employment in private pathology laboratories/groups, medical examiner's offices, morgues, government or reference laboratories, or universities, and may be self-employed and provide contract work.
=== Constipation === Opioid-induced constipation (OIC) develops in 90 to 95% of people taking opioids long-term. Since tolerance to this problem does not generally develop, most people on long-term opioids need to take a laxative and/or enemas. Treatment of OIC is successional and dependent on severity. The first mode of treatment is non-pharmacological, and includes lifestyle modifications like increasing dietary fiber, fluid intake (around 1.5 L (51 US fl oz) per day), and physical activity. If non-pharmacological measures are ineffective, laxatives, including stool softeners (e.g., polyethylene glycol), bulk-forming laxatives (e.g., fiber supplements), stimulant laxatives (e.g., bisacodyl, senna), and/or enemas, may be used. A common laxative regimen for OIC is the combination of docusate and bisacodyl. Osmotic laxatives, including lactulose, polyethylene glycol, and milk of magnesia (magnesium hydroxide), as well as mineral oil (a lubricant laxative), are also commonly used for OIC. If laxatives are insufficiently effective (which is often the case), opioid formulations or regimens that include a peripherally-selective opioid antagonist, such as methylnaltrexone bromide, naloxegol, alvimopan, or naloxone (as in oxycodone/naloxone), may be tried. A 2018 (updated in 2022) Cochrane review found that the evidence was moderate for alvimopan, naloxone, or methylnaltrexone bromide but with increased risk of adverse events. Naloxone by mouth appears to be the most effective.
=== Nootropic or "smart drug" === Selegiline is considered by some to be a nootropic, otherwise known as a cognitive enhancer or "smart drug", both at clinical and sub-clinical dosages, and has been used off-label and non-medically to improve cognitive performance. It is one of the most popular such agents. Selegiline has been found to have neuroprotective activity against certain neurotoxins and to increase the production of several brain growth factors, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF). The drug has also been found in animal models to improve learning ability and to help preserve it during ischemia and aging. Despite claims that selegiline and other claimed nootropics have cognitive-enhancing effects however, these effects are controversial and their benefits versus risks are uncertain.
Sources: en.wikipedia.org
Lyophilized products should be stored in airtight containers, protected from moisture and light, at the temperature specified by the manufacturer. Many require refrigeration at 2–8 °C, while some need frozen storage. Always check the product label for specific conditions.
Moisture can cause the porous cake to collapse, increase molecular mobility, and accelerate chemical degradation. It may also promote microbial growth if the product lacks preservatives. Proper sealing and handling are essential to maintain stability.
Some formulations contain labile biological molecules that degrade even in the dry state at higher temperatures. Others have a low glass transition temperature, meaning the cake can soften or collapse at room temperature. Cold storage reduces molecular motion and slows degradation.
Sealed vials or containers should be kept at the temperature specified by stability data, often controlled room temperature or 2–8 °C. Moisture and oxygen barriers are important because both can degrade sensitive materials. Opened containers may need immediate use or protection from ambient humidity.