primary drying raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-11-03 and is reviewed periodically as new material appears.
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.
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.
| 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 |
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.
Lyophilization is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid that can be reconstituted later.
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.
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.
These inland occurrences are predominantly associated with urban environments, particularly in arboretums and parks on planted ornamental trees, suggesting human-mediated dispersal. These documented range expansions have identified X. parietina as one of the few lichen species to have become demonstrably invasive in new territories, primarily through horticultural introduction pathways. Research indicates that X. parietina is being transported inland on nursery stock from coastal regions, as evidenced by its presence on commercial nursery plants and absence from naturally occurring woody plants in undisturbed areas outside these cities.
== Research directions == Research is being done to identify the proteins cleaved by calpain-3. Gene therapy is being studied to replace the function of the calpain-3. Injection of plasmids containing CAPN3 into mouse models resulted in increased levels of calpain-3.
The Han nationalist revolutionary Sun Yat-sen made Han Chinese superiority a basic tenet of the 1911 Revolution. In Sun's revolutionary philosophical view, Han identity is exclusively possessed by the so-called civilized Hua Xia people who originated from the Central Plains, and were also the former subjects of the Celestial empire and evangelists of Confucianism. Restoring Chinese rule to the Han majority was one of the motivations for supporters of the 1911 Revolution to overthrow the Manchu-led Qing dynasty in 1912, which led to the establishment of the Han-dominated Republic of China. After the establishment of the republic, Sun went to offer sacrifices in Hongwu Emperor's Xiao Mausoleum:
Public health laboratories operate as a first line of defense to protect the public against diseases and other health hazards. Day-to-day operations range from testing water and food, checking for toxins in soil, and investigating new strains of infectious diseases, such as COVID-19 or Ebola. Every US state and territory, and the District of Columbia, has a central governmental public health laboratory that performs testing and other laboratory services on behalf of the entire jurisdiction. In addition, some states have local public health laboratories ranging in size from large metropolitan laboratories with over a hundred scientists to small rural laboratories with one or two staff that support local public health.
The probable chemistry of roentgenium has received more interest than that of the two previous elements, meitnerium and darmstadtium, as the valence s-subshells of the group 11 elements are expected to be relativistically contracted most strongly at roentgenium. Calculations on the molecular compound RgH show that relativistic effects double the strength of the roentgenium–hydrogen bond, even though spin–orbit interactions also weaken it by 0.7 eV (68 kJ/mol). The compounds AuX and RgX, where X = F, Cl, Br, O, Au, or Rg, were also studied. Rg+ is predicted to be the softest metal ion, even softer than Au+, although there is disagreement on whether it would behave as an acid or a base. In aqueous solution, Rg+ would form the aqua ion [Rg(H2O)2]+, with an Rg–O bond distance of 207.1 pm. It is also expected to form Rg(I) complexes with ammonia, phosphine, and hydrogen sulfide.
Sources: en.wikipedia.org
19 May A policies study review, based on a systematic examination of existing methane policies across sectors, concludes that both only "about 13% of methane emissions are covered by methane mitigation policies" and that the effectiveness of these policies "is far from clear". Researchers propose a methodological approach and quantifications for reparations from fossil fuel producers. Cross-disciplinary researchers propose academics make universities implement, leadingly, the plant-based dietary transition that an increasingly large and confirmed corpus of studies, to which these contributed to, concludes is vital (7 May). Metascience-related events Nature reports China has "overtaken the United States as the number one ranked country or territory for contributions to research articles published in the Nature Index group of high-quality natural-science journals", remaining at second place overall. The Nature Index, since 2016, evaluates contribution by the number of articles published in a subgroup of their journals – other potential or less popular approaches and metrics for quantifications of success or impact can or could produce different rankings or annual tables and conclusions. 34% of neuroscience papers and 23% of medical papers published in 2020 were probably fabricated or plagiarized, according to a preprint study, stemming from paper mills (9 May). A time-use research study (10 May) estimates the costs of manuscript (re)formatting to fit journal guidelines, ~$230 million or ~75 million hours of lost academics' time in 2021.
Since independence, Ghana has been devoted to ideals of nonalignment and is a founding member of the Non-Aligned Movement. Ghana favours international and regional political and economic co-operation, and is an active member of the United Nations and the African Union. Three U.S. presidents have made diplomatic trips to Ghana (Bill Clinton, George W. Bush and Barack Obama), along with a Vice President (Kamala Harris). Some Ghanaian diplomats and politicians hold positions in international organisations, including Ghanaian diplomat and former Secretary-General of the United Nations Kofi Annan, International Criminal Court Judge Akua Kuenyehia, and former President Jerry John Rawlings and former President John Agyekum Kufuor, who both served as diplomats of the United Nations. In September 2010, President John Atta Mills visited China on an official visit. Mills and then-general secretary of the Chinese Communist Party Hu Jintao marked the 50th anniversary of diplomatic ties between the two nations, at the Great Hall of the People. China reciprocated with an official visit in November 2011, by the vice-chairman of the Standing Committee of the National People's Congress of China, Zhou Tienong who visited Ghana and met with Ghana's president John Mahama. China became one of the top investing countries of Ghana, which predominantly focus on infrastructure, natural resources, and the manufacturing sector, have promoted economic growth, job creation, and technology transfer in Ghana.
=== Role in tumor growth === Endothelial progenitor cells are likely important in tumour growth and are thought to be critical for metastasis and the angiogenesis. A large amount of research has been done on CFU-Hill bone marrow-derived putative EPCs. Ablation of the endothelial progenitor cells in the bone marrow lead to a significant decrease in tumour growth and vasculature development. This indicates that endothelial progenitor cells present novel therapeutic targets. Inhibitor of DNA Binding 1 (ID1) has been used as a marker for these cells; this allows for tracking EPCs from the bone marrow to the blood to the tumour-stroma and even incorporated in tumour vasculature. Recently it has been found that miRNAs regulate EPC biology and tumour angiogenesis. This work by Plummer et al. found that in particular targeting of the miRNAs miR-10b and miR-196b led to significant defects in angiogenesis-mediated tumor growth by decreasing the mobilization of proangiogenic EPCs to the tumour. These findings indicate that directed targeting these miRNAs in EPCs may result in a novel strategy for inhibiting tumor angiogenesis. Studies have shown ECFCs and human umbilical vein endothelial cells (HUVECs) to have a capacity for tumor migration and neoangiogenesis even greater than that of other CD34+ hematopoietic cells when implanted in immunodeficient mice, suggesting the endothelial progenitors play a key role, but further supporting the importance of both cell types as targets for pharmacological therapy.
=== Hoarding by intermediaries === Intermediaries, who play a significant role in Iran's distribution network, often hoard food products when they anticipate price increases. By controlling the release of these goods, they can manipulate market conditions to maximize profits. This practice not only increases prices but also leads to significant volatility in the market.
Sources: en.wikipedia.org
I. Bilobed flap The design of the bilobed flap derives from the creation of two adjacent random transposition flaps (lobes). In its original design, the leading flap is applied to cover the defect, and the second flap, is emplaced where the skin flexes more, and fills the donor-site wound (from where the first flap was harvested), which then is closed primarily, with sutures. The first flap is oriented geometrically, at 90 degrees from the long axis of the wound (defect), and the second flap is oriented 180 degrees from the axis of the wound. Although effective, the bilobed flap technique did create troublesome "dog ears" of excess flesh that required trimming and it also produced a broad skin-donor area that was difficult to confine to the nose. In 1989, J. A. Zitelli modified the bilobed flap technique by: (a) orienting the leading flap at 45 degrees from the long axis of the wound; and (b) orienting the second flap at 90 degrees from the axis of the wound. Said orientations and emplacements eliminated the excess-flesh "dog ears", and thus required a smaller area of donor skin; resultantly, the broad-based, bilobed flap is less prone to the "trap door" and the "pin cushion" deformities common to skin-flap transposition procedure.
PHGDH is allosterically regulated by its downstream product, L-serine. This feedback inhibition is understandable considering that 3-phosphoglycerate is an intermediate in the glycolytic pathway. Given that PHGDH represents the committed step in the production of serine in the cell, flux through the pathway must be carefully controlled. L-serine binding has been shown to exhibit cooperative behavior. Mutants that decreased this cooperativity also increased in sensitivity to serine's allosteric inhibition, suggesting a separation of the chemical mechanisms that result in allosteric binding cooperativity and active site inhibition. The mechanism of inhibition is Vmax type, indicating that serine affects the reaction rate rather than the binding affinity of the active site. Although L-serine's allosteric effects are usually the focus of regulatory investigation, it has been noted that in some variants of the enzyme, 3-phosphoglycerate dehydrogenase is inhibited at separate positively charged allosteric site by high concentrations of its own substrate.
2 NaN3 + 2 HNO2 → 3 N2 + 2 NO + 2 NaOH A safer modification to the above method that avoids the potential production of hydrazoic acid or nitrogen oxide fumes is that of W. F. Rinkenbach. A solution of 2.5 oz (71 g) sodium nitrite in 1 US pt (470 mL) of water is added to a stirring dispersion of 1 oz (28 g) sodium azide in 1.5 US gal (5.7 L) 10% ammonium acetate, followed by addition of 7 US fl oz (210 mL) of glacial acetic acid. The solution is allowed to stand in a warm place for an hour and disposed of.
=== Androgen-independent === Minoxidil dilates small blood vessels; it is not clear how this causes hair to grow. Other treatments include tretinoin combined with minoxidil, ketoconazole shampoo, dermarolling (Collagen induction therapy), spironolactone, alfatradiol, topilutamide (fluridil), topical melatonin, and intradermal and intramuscular botulinum toxin injections to the scalp. The drug suvomipic (PP405; JXL069) is a potential treatment which works by stimulating follicular mitochondria. It is currently in Phase II human clinical trials.
A lobotomy (from Greek λοβός (lobos) 'lobe' and τομή (tomē) 'cut, slice') or leucotomy is a discredited form of neurosurgical treatment for psychiatric disorder or neurological disorder (e.g. epilepsy, depression) that involves severing connections in the brain's prefrontal cortex. The surgery severs most of the connections to and from the prefrontal cortex, and the anterior part of the frontal lobes of the brain. From the 1930s until the 1970s, the treatment was used for handling psychiatric disorders as a mainstream procedure in some countries. A preoccupation with the ability to work and personal responsibility over patient well-being were contributing factors to the prevalence of lobotomies in the United States. The originator of the procedure, Portuguese neurologist António Egas Moniz, shared the Nobel Prize for Physiology or Medicine of 1949 for the "discovery of the therapeutic value of leucotomy in certain psychoses", although the awarding of the prize has been subject to controversy. The procedure was modified and championed by Walter Freeman, who performed the first lobotomy at a mental hospital in the United States in 1936. Its use increased dramatically from the early 1940s and into the 1950s; by 1951, almost 20,000 lobotomies had been performed in the US and proportionally more in the United Kingdom. More lobotomies were performed on women than on men: a 1951 study found that nearly 60% of American lobotomy patients were women, and limited data shows that 74% of lobotomies in Ontario from 1948 to 1952 were performed on female patients.
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.
Collapse occurs when the product temperature rises above its collapse or eutectic temperature during drying. The frozen matrix loses structure, producing a shrunken or melted appearance. This can slow reconstitution and may affect stability.