sublimation comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-08-13. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
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 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.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
== Biosynthesis == Patellamide A originates from a ribosomal peptide, making it a member of the RiPP superfamily of natural products. This was determined after genome sequencing of P. didemi showed a lack of non ribosomal peptide synthetases. The biosynthetic gene cluster for patellamide A contains the genes patA, patB, patC, patD, patE, patF and patG. These genes, when introduced into E. coli, cause the production of patellamide A, definitively confirming their responsibility for patellamide A biosynthesis. The gene patE encodes the precursor peptide that contains the primary sequences of patellamides A and C. It has been proposed by Schmidt et al. that this prepatellamide is heterocyclized to form the oxazoline and thiazoline rings by PatD2. It is proposed that PatG1 is subsequently involved in oxidizing the thiazoline rings to the thiazole rings found in patellamide A. The peptide is then cleaved, possibly by PatA or PatG2, and cyclized, the cyclization is likely aided by adenylation by PatD1, forming the two cyclic peptides, patellamides A and C. Although all the amino acids used in the production of patellamide A are L-amino acids, some of the amino acids found in natural patellamide A are the D-epimers. It is proposed that epimerization of these amino acids occurs spontaneously. This was determined by comparison to a similar system, lissoclinamide 7.
Data from high-throughput chromosome conformation capture experiments, such as Hi-C (experiment) and ChIA-PET, can provide information on the three-dimensional structure and nuclear organization of chromatin. Bioinformatic challenges in this field include partitioning the genome into domains, such as Topologically Associating Domains (TADs), that are organised together in three-dimensional space. Finding the structure of proteins is an important application of bioinformatics. The Critical Assessment of Protein Structure Prediction (CASP) is an open competition where worldwide research groups submit protein models for evaluating unknown protein models.
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Progesterone, a progestogen, is the other of the two major sex hormones in women. It is mainly involved in the regulation of the female reproductive system, the menstrual cycle, pregnancy, and lactation. The non-reproductive effects of progesterone are fairly insignificant. Unlike estrogens, progesterone is not known to be involved in the development of female secondary sexual characteristics, and hence is not believed to contribute to feminization in women. One area of particular interest in terms of the effects of progesterone in women is breast development. Estrogens are responsible for the development of the ductal and connective tissues of the breasts and the deposition of fat into the breasts during puberty in girls. Conversely, high levels of progesterone, in conjunction with other hormones such as prolactin, are responsible for the lobuloalveolar maturation of the mammary glands during pregnancy. This allows for lactation and breastfeeding after childbirth. Although progesterone causes the breasts to change during pregnancy, the breasts undergo involution and revert to their pre-pregnancy composition and size after the cessation of breastfeeding. Every pregnancy, lobuloalveolar maturation occurs again anew. There are two types of progestogens: progesterone, which is the natural and bioidentical hormone in the body; and progestins, which are synthetic progestogens. There are dozens of clinically used progestins.
=== Civic Society === Bromley Civic Society is a civic society for the historic centre of Bromley. It is a founder member of Civic Voice. It seeks to educate the public about the community's history and to preserve historical sites.
Sources: en.wikipedia.org
== Lithium carbonate equivalent == Lithium carbonate equivalent, abbreviated LCE, is an industry standard for lithium compounds whose lithium content is expressed in weight-equivalent of lithium carbonate. The term is commonly used in the lithium mining industry.
Raleigh's all-time record high temperature is 106 °F (41 °C) on July 5, 2024, while the all-time record low is −9 °F (−23 °C) on January 21, 1985. Raleigh falls in USDA hardiness zones 7b (5 °F to 10 °F) and 8a (10 °F to 15 °F).
== Selected publications == Ammann AJ and Stiehm ER. Immune Globulin Levels in Colostrum and Breast Milk, and Serum From Formula- and Breast-Fed Newborns.[link removed] Proc Soc Exp Biol Med, 122:1098-1100, 1966. Stiehm ER, Ammann AJ, Cherry JD. Elevated cord macroglobulins in the diagnosis of intrauterine infections. NEJM, 275:971-977, 1966. Ammann AJ, Wara D, Salmon S, Perkins H. Thymus transplantation. Thymus Transplantation — Permanent Reconstitution of Cellular Immunity in a Patient with Sex-Linked Combined Immunodeficiency. NEJM, 289:5-9, 1973. Wara DW, Goldstein AL, Doyle NE, Ammann AJ. Thymosin Activity in Patients with Cellular Immunodeficiency. NEJM, 292:70-74, 1975. (One of the 500 most widely quoted articles in 1980, Citation Classic) Giblett ER, Ammann AJ, Sandman R, Wara DW, Diamond LK. Nucleoside-phosphorylase deficiency in a child with severely defective T-cell immunity and normal B-cell immunity. Lancet, 1:2020-1014, 1975. (One of the 500 most widely quoted articles in 1984, Citation Classic) Ammann AJ, Addiego J, Wara DW, Lubin B, Smith WB, Mentzer WC. Polyvalent pneumococcal-polysaccharide immunization of patients with sickle-cell anemia and patients with splenectomy. NEJM, 297:897-900, 1977. Ammann AJ, Cowan MJ, Wara DW, Weintrub P, Dritz S, Goldman H, Perkins HA. Acquired immunodeficiency in an infant: Possible transmission by means of blood products. Lancet, 1:956-958, 1983.
Although orphan disease populations are the smallest, the cost of per-patient outlays among them are the largest and are expected to increase as more people with rare diseases become eligible for subsidies – in the U.S., for example, through the Affordable Care Act.
Sources: en.wikipedia.org
In the first mechanism, Browner M.F. and colleagues proposed the base-catalysis mechanism, carried out by the conserved glutamate residue and the Zn2+ ion. In the second mechanism, the Matthews-mechanism, Kester and Matthews suggested an interaction between a water molecule and the Zn2+ ion during the acid-base catalysis. In the third mechanism, the Manzetti-mechanism, Manzetti Sergio and colleagues provided evidence that a coordination between water and zinc during catalysis was unlikely, and suggested a third mechanism wherein a histidine from the HExxHxxGxxH-motif participates in catalysis by allowing the Zn2+ ion to assume a quasi-penta coordinated state, via its dissociation from it. In this state, the Zn2+ ion is coordinated with the two oxygen atoms from the catalytic glutamic acid, the substrate's carbonyl oxygen atom, and the two histidine residues, and can polarize the glutamic acid's oxygen atom, proximate the scissile bond, and induce it to act as reversible electron donor. This forms an oxyanion transition state. At this stage, a water molecule acts on the dissociated scissile bond and completes the hydrolyzation of the substrate.
Today, it is considered that GBS pigment (granadaene) and hemolysin are identical or closely related molecules. Sialic acid is a notable virulence factor in S. agalactiae despite being found normally in humans and many other animals. By expressing an unusually high amount of sialic acid on the bacterial cell surface, S. agalactiae can subvert the innate immune system, convincing leukocytes that the bacteria are human cells.
The field went through multiple cycles of optimism throughout its history, followed by periods of disappointment and loss of funding, known as AI winters. Funding and interest increased substantially after 2012, when graphics processing units (GPUs) started being used to accelerate neural networks, and deep learning outperformed previous AI techniques. This growth accelerated further after 2017 with the transformer architecture. In the 2020s, an AI boom coincided with advances in generative AI, which became widespread and allowed for the creation and modification of media. In addition to AI safety and unintended consequences and harms from the use of AI, ethical concerns, AI's long-term effects, environmental effects, and potential existential risks have prompted discussions of AI regulation.
Sources: en.wikipedia.org
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.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
Karl Fischer titration is a common reference method that quantifies water by a chemical reaction. Thermogravimetric analysis can also estimate moisture by weight loss on heating. Method choice depends on sample size and whether other volatile substances are present.