A practical reference on Sublimation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-09-18 and is reviewed periodically as new material appears.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
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.
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.
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.
==== Land ==== The Peak Tram, Hong Kong's first public transport system, has provided funicular rail transport between Central and Victoria Peak since 1888. The Central and Western District has an extensive system of escalators and moving pavements, which, together with the Mid-Levels escalator system, is the world's longest outdoor covered escalator system. Hong Kong Tramways' tram network covers a portion of Hong Kong Island, covering from Kennedy Town to Shau Kei Wan, with a branch to Happy Valley. It operates 6 routes and has had a ridership of 42,558 in 2022. It began servicing Hong Kong since 1904. Hong Kong Tramways currently holds the Guinness World Record as the "Largest double-decker tram fleet in service", certified on 30 July 2021, with a fleet of 165 double-decker trams. The fleet of trams was mostly built by Hong Kong Tramways.
The opening of the Iron Curtain between Austria and Hungary at the Pan-European Picnic on 19 August 1989 set in motion a peaceful chain reaction, at the end of which there was no longer an East Germany and the Eastern Bloc had disintegrated. After the picnic, which was based on an idea by Otto von Habsburg to test the reaction of the USSR and Mikhail Gorbachev to an opening of the border, tens of thousands of media-informed East Germans set off for Hungary. Erich Honecker dictated to the Daily Mirror for the Pan-European Picnic: "Habsburg distributed leaflets far into Poland, on which the East German holidaymakers were invited to a picnic. When they came to the picnic, they were given gifts, food and Deutsche Mark, and then they were persuaded to come to the West." The leadership of the GDR in East Berlin did not dare to completely block the borders of their own country and the USSR did not respond at all. Thus the bracket of the Eastern Bloc was broken. Following the summer of 1989, by early November refugees were finding their way to Hungary via Czechoslovakia or via the West German embassy in Prague. On 30 September, following negotiations with East Germany and the Soviet Union, the West German Foreign Minister Hans-Dietrich Genscher went to the Prague embassy to personally inform the thousands of refugees that they were allowed to leave for West Germany.
Echoing this caution, Divakar and Crespo emphasise that maximum‑likelihood pipelines such as RAxML and Bayesian frameworks (e.g., MrBayes, BEAST) give the most dependable results only when their outputs are compared side by side and underpinned by formal model testing; over‑interpreting a single, untested method can yield artefactual trees.
== Occurrence == Argon constitutes 0.934% by volume and 1.288% by mass of Earth's atmosphere. Air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation, a process that also produces purified nitrogen, oxygen, neon, krypton and xenon. Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively.
Sources: en.wikipedia.org
== Contraindications == Nicotine use for tobacco cessation has few contraindications. It is not known whether nicotine replacement therapy is effective for smoking cessation in adolescents, as of 2014. It is therefore not recommended to adolescents. It is not safe to use nicotine during pregnancy or breastfeeding, although it is safer than smoking. The desirability of NRT use in pregnancy is therefore debated. Randomized trials and observational studies of nicotine replacement therapy in cardiovascular patients show no increase in adverse cardiovascular events compared to those treated with placebo. Using nicotine products during cancer treatment may be contraindicated, as nicotine may promote tumour growth, but temporary use of NRTs to quit smoking may be advised for harm reduction. Nicotine gum is contraindicated in individuals with temporomandibular joint disease. People with chronic nasal disorders and severe reactive airway disease require additional precautions when using nicotine nasal sprays. Nicotine in any form is contraindicated in individuals with a known hypersensitivity to nicotine.
=== Notable cases === 1994: Lucien Bouchard, future premier of Québec, Canada, who was infected while leader of the federal official opposition Bloc Québécois party, lost a leg to the illness. 1994: A cluster of cases occurred in Gloucestershire, in the west of England. Of five confirmed and one probable infection, two died. The cases were believed to be connected. The first two had acquired the Streptococcus pyogenes bacteria during surgery; the remaining four were community-acquired. The cases generated much newspaper coverage, with lurid headlines such as "Flesh Eating Bug Ate My Face". 1997: Jeff Moorad, former agent and partial owner of the San Diego Padres and Arizona Diamondbacks, contracted the disease. He had seven surgeries in a little more than a week and later fully recovered. 2004: Don Rickles, American stand-up comedian, actor, and author, known especially for his insult comedy, contracted the disease in his left leg. He had six operations and later recovered. The condition confined him in his later years to performing comedy from a chair. 2004: Eric Allin Cornell, winner of the 2001 Nobel Prize in Physics, lost his left arm and shoulder to the disease. 2005: Alexandru Marin, an experimental particle physicist, professor at MIT, Boston University, and Harvard University, and researcher at CERN and JINR, died from the disease. 2006: Alan Coren, British writer and satirist, announced in his Christmas column for The Times that his long absence as a columnist had been caused by his contracting the disease while on holiday in France. 2009: R. W.
In 1944, Jones became the first Black-American to become a member of the American Society of Refrigeration Engineers. 1953 Merit Award, Phyllis Wheatley Auxiliary (Phillis Wheatley Club of Cleveland, Ohio), "for outstanding achievements which serve as an inspiration to youth." In 1977, he was posthumously inducted into the Minnesota Inventors Hall of Fame. In 1991, the National Medal of Technology was awarded to Joseph A. Numero and Frederick M. Jones. President George Bush presented the awards posthumously to their widows at a ceremony in the White House Rose Garden. Jones was the first Black American to receive the award. In 1996, the Thermo King Model 'C' refrigeration unit, the world's first front-mount refrigeration unit for mobile trucks, was designated an International Mechanical Engineering Landmark by the American Society of Mechanical Engineers. Jones designed and built the prototype from junkyard salvage. The challenges were to build a structural frame and refrigerant tubing connections that would withstand the constant pounding of road vibrations. In 2007, Jones was inducted into the National Inventors Hall of Fame, which honored him as a "Visionary Veteran." In the March 2009 issue of Heavy Duty Truck magazine, editor Tom Berg dubbed Jones "The King of Cool", and wrote that his "technological breakthrough redefined the global marketplace, with cultural reverberations felt from the world's largest cities to its most isolated villages." In 2015, Jones' achievements were recognized by the creators of a Black heritage-themed playground located in Minneapolis.
Tofu has also been fused into other cuisines in the West, for instance in Indian-style curries. Tofu and soy protein can be industrially processed to match the textures and flavors of cheese, pudding, eggs, bacon, and similar products. Tofu's texture can also be altered by freezing, puréeing, and cooking. In the Americas, Europe, Australia and New Zealand, tofu is frequently associated with vegetarianism and veganism, as it is a source of non-animal protein. In India, tofu is used as a low-fat replacement for paneer, providing a similar texture. Awara (also known as wara soya, Nigerian tofu, or Beske), is a food commonly consumed in Northern Nigeria. It's produced by curdling soy milk with a natural agent, then pressing, seasoning, and frying it into cubes. As opposed to an ingredient substitute, the tofu is eaten as the main ingredient, often with vegetables on the side.
Hanoi hosted five times, while four provinces & cities have each hosted once: Ho Chi Minh City will host the games for the second time in 2026. Hanoi leads the all time medal count for the Vietnam National Games, and has topped the medal table on 6 separate occasions.
Sources: en.wikipedia.org
stop codon Also termination codon. A codon that signals the termination of protein synthesis during translation of a messenger RNA transcript. In the standard genetic code, three different stop codons are used to dissociate ribosomes from the growing amino acid chain, thereby ending translation: UAG (nicknamed "amber"), UAA ("ochre"), and UGA ("opal"). Contrast start codon.
=== Exposure route considerations in CNT toxicology === Pulmonary exposure: Inhalation of airborne CNTs during manufacturing or handling poses the highest risk. CNTs can induce dose-dependent pulmonary toxicity, including granuloma formation, fibrosis, and inflammation. MWCNTs, due to their fiber-like structure, are particularly prone to eliciting asbestos-like responses. SWCNTs may translocate systemically but generally exhibit less chronic pulmonary toxicity. Dermal and consumer exposure: Intact skin provides a barrier to CNT penetration, though localized cutaneous inflammation has been reported while evidence suggests limited systemic health impact. Oral and systemic exposure: Oral ingestion of CNTs typically results in low bioavailability and rapid excretion, with significant effects observed only at high doses. Systemic exposure via intravenous or intraperitoneal routes is primarily relevant in experimental or therapeutic contexts.
For services to Business and to the UK Film Industry. Catherine Anne Goodman, LVO. Artist and Educator. For services to Art. Professor Roger James Goodman. Nissan Professor of Modern Japanese Studies and Warden, St. Antony's College, University of Oxford. For services to Social Science. Gayle Jean Margaret Gorman. Lately HM Chief Inspector and Chief Executive, Education Scotland. For services to Education and Charity. Gerard Arthur Georges Grech. Founder, Tech Nation and Managing Director, Founders at the University of Cambridge. For services to the Technology Sector. The Reverend Nicholas Glyn Paul Gumbel. Lately Vicar, Holy Trinity Brompton, London. For services to the Church of England. Paul Harris. Deputy Chief Executive Officer and Operations Director, HM Courts and Tribunals Service. For Public and Voluntary Service. Martin James Hewitt, QPM. Lately Chair, National Police Chiefs Council. For services to Policing. Professor Peter Michael Hollingsworth. Director of Science and Deputy Keeper, Royal Botanic Garden, Edinburgh. For services to Botanical Science. Karl James Hoods. Chief Digital and Information Officer, Department for Science, Innovation and Technology and Department for Energy Security and Net Zero. For services to Technology and to Education. Professor Andrew Lee Hopkins, FRS, FMedSci, FRSE. Chief Executive Officer, Exscientia. For services to Science and to Innovation. Christian Edward Johnston Horner, OBE. Team Principal and Chief Executive Officer, Red Bull Racing. For services to Motor Sport. Pauline Jean Howie, OBE.
=== Macroscopic examination === Visual examination of the specimen may provide information to the pathologist or the physician. For example, fluid drained from an abscess may appear cloudy, or cerebrospinal fluid obtained by lumbar puncture may exhibit xanthochromia, suggesting a bleed has occurred. Laboratory technologists may provide qualitative descriptions accordingly.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
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.