Sublimation 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 2026-05-03 and is reviewed periodically as new material appears.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
| Property | Value | Notes |
|---|---|---|
| Common names | Lyophilization; freeze-drying | Terms used interchangeably. |
| Phase change | Sublimation | Ice converts directly to vapor under vacuum. |
| Typical chamber pressure | 0.01–1 mbar | Below the triple point of water. |
| Primary drying product temperature | −40 to −10 °C | Kept below collapse or glass transition temperature. |
| Water content after drying | 0.5–3% w/w | Varies with formulation and cycle. |
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
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.
The making and drinking of cider is traditional in several areas of northern Spain, mainly Galicia, the Principality of Asturias, Cantabria, and the Basque Country. The largest producer of cider in Spain is the Atlantic region of Asturias, where cider is considered not only a beverage but an intrinsic part of its culture and folklore. Asturias amounts more than 80% of the whole production of Spain. The consumption of cider in Asturias is of 54 litres per person/year, probably the highest in any European region. The first testimony about cider in Asturias was made by Greek geographer Strabo in 60 BC. The traditional Asturian sidra is a still cider of 4–8% strength, although there are other varieties. Traditionally, it is served in sidrerías and chigres, pubs specialising in cider where it is also possible to have other drinks as well as traditional food. One of the most outstanding characteristics is that it is poured in very small quantities from a height into a wide glass, with the arm holding the bottle extended upwards and the one holding the glass extended downward. This technique is called escanciar un culín (also echar un culín) and is done to get air bubbles into the drink (espalmar), thus giving it a sparkling taste like Champagne that lasts a very short time. Cider is also poured from barrels in the traditional Espichas. One of the most popular ciders in Spain is called "El Gaitero" (the bagpipe player) which can be found everywhere in Spain and which is produced in this region.
=== Holter monitor === A Holter monitor records a continuous EKG rhythm pattern (rarely a full EKG) for 24 hours or more. These monitors are used for suspected frequent rhythm abnormalities, especially ones the wearer may not recognize by symptoms. They are more expensive than event monitors.
The distinguishing characteristic of the Rebels is that they have had all of their facial orifices sealed shut in an effort to avoid absorption of and subsequent infection by the parasitic black oil; this led to a somewhat grotesque appearance. In the latter seasons of The X-Files, the role of the Bounty Hunters on Earth has largely been taken over by the Super Soldiers, human replacements capable of withstanding incredible amounts of damage.
Foraging ants travel distances of up to 200 metres (700 ft) from their nest and scent trails allow them to find their way back even in the dark. In hot and arid regions, day-foraging ants face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants of the genus Cataglyphis such as the Sahara desert ant navigate by keeping track of direction as well as distance travelled. Distances travelled are measured using an internal pedometer that keeps count of the steps taken and also by evaluating the movement of objects in their visual field (optical flow). Directions are measured using the position of the sun. They integrate this information to find the shortest route back to their nest. Like all ants, they can also make use of visual landmarks when available as well as olfactory and tactile cues to navigate. Some species of ant are able to use the Earth's magnetic field for navigation. The compound eyes of ants have specialised cells that detect polarised light from the Sun, which is used to determine direction. These polarization detectors are sensitive in the ultraviolet region of the light spectrum. In some army ant species, a group of foragers who become separated from the main column may sometimes turn back on themselves and form a circular ant mill. The workers may then run around continuously until they die of exhaustion.
== History == Peptide amphiphiles were developed in the 1990s. They were first described by the group of Matthew Tirrell in 1995. These first reported PA molecules were composed of two domains: one of lipophilic character and another of hydrophilic properties, which allowed self-assembly into sphere-like supramolecular structures as a result of the association of the lipophilic domains away from the solvent (hydrophobic effect), which resulted in the core of the nanostructure. The hydrophilic residues become exposed to the water, giving rise to a soluble nanostructure. Work in the laboratory of Samuel I. Stupp by Hartgerink et al., in the early 2000s, reported a new type of PA that are able to self-assemble into elongated nanostructures. These novel PAs contain three regions: a hydrophobic tail, a region of beta-sheet-forming amino acids, and a charged peptide epitope designed to allow solubility of the molecule in water. In addition, the PAs may contain a targeting or signaling epitope that allows the formed nanostructures to perform a biological function, either targeting or signaling, by interacting with living systems. The self-assembly mechanism of these PAs is a combination of hydrogen-bonding between beta-sheet forming amino acids and hydrophobic collapse of the tails to yield the formation of cylindrical micelles that present the peptide epitope at extremely high density at the nanofiber surface. By changing pH or adding counterions to screen the charged surfaces of fibers, gels can be formed.
Sources: en.wikipedia.org
Adult linear IgA disease Bullous pemphigoid Bullous lupus erythematosus Childhood linear IgA disease (chronic bullous disease of childhood) Cicatricial pemphigoid (benign mucosal pemphigoid, benign mucous membrane pemphigoid, ocular pemphigus, scarring pemphigoid) Dermatitis herpetiformis (Duhring disease) Dyshidrosis (recurrent vesicular palmoplantar dermatitis, acute vesiculobullous hand eczema, dyshidrotic dermatitis, pompholyx) Endemic pemphigus (endemic pemphigus foliaceus, fogo selvagem) Epidermolysis bullosa acquisita Grover's disease (benign papular acantholytic dermatosis, persistent acantholytic dermatosis, transient acantholytic dermatosis) IgA pemphigus Intraepidermal neutrophilic IgA dermatosis Localized cicatricial pemphigoid (Brunsting–Perry cicatricial pemphigoid) Paraneoplastic pemphigus Pemphigus erythematosus (Senear–Usher syndrome) Pemphigus foliaceus Pemphigus herpetiformis (acantholytic herpetiform dermatitis, herpetiform pemphigus, mixed bullous disease, pemphigus controlled by sulfapyridine) Pemphigoid nodularis Pemphigus vegetans Pemphigus vegetans of Hallopeau Pemphigus vegetans of Neumann Pemphigus vulgaris Vesicular pemphigoid Vulvar childhood pemphigoid
Glucokinase is a monomeric protein of 465 amino acids and a molecular weight of about 50 kDa. There are at least two clefts, one for the active site, binding glucose and MgATP, and the other for a putative allosteric activator that has not yet been identified. This is about half the size of the other mammalian hexokinases, which retain a degree of dimeric structure. Several sequences and the three-dimensional structure of the key active sites are highly conserved both in intra-species homologs and across species from mammals to yeast. The ATP binding domain, for example, are shared with hexokinases, bacterial glucokinases, and other proteins, and the common structure is termed an actin fold.
=== Deputy Leaders of the Liberal Party in the House of Commons === Donald Maclean (1920–1922) John Simon (1922–1924) Post vacant (1924–1929) Herbert Samuel (1929–1931) Archibald Sinclair (1931–1935) Francis Dyke Acland (1935–1939) Post vacant (1939–1940) Percy Harris (1940–1945) Post vacant (1945–1949) Megan Lloyd George (1949–1951) Post vacant (1951–1962) Donald Wade (1962–1964) Post vacant (1964–1976) John Pardoe (1976–1979) Post vacant (1979–1985) Alan Beith (1985–1988)
Rather, the tRNA-bound seryl residue is converted to a selenocysteine residue by the pyridoxal phosphate-containing enzyme selenocysteine synthase. In eukaryotes and archaea, two enzymes are required to convert tRNA-bound seryl residue into tRNA selenocysteinyl residue: PSTK (O-phosphoseryl-tRNA[Ser]Sec kinase) and selenocysteine synthase. Finally, the resulting Sec-tRNASecis specifically bound to an alternative translational elongation factor (SelB or mSelB (or eEFSec)), which delivers it in a targeted manner to the ribosomes translating mRNAs for selenoproteins. The specificity of this delivery mechanism is brought about by the presence of an extra protein domain (in bacteria, SelB) or an extra subunit (SBP2 for eukaryotic mSelB/eEFSec) which bind to the corresponding RNA secondary structures formed by the SECIS elements in selenoprotein mRNAs.
Sources: en.wikipedia.org
==== Agrochemicals ==== Agrochemical companies are the second largest users of fine chemicals. Most products have a "pharmaceutical heritage". As a consequence of an intensive M&A activity (Mergers and Acquisitions) over the past 10–20 years, the industry now is more consolidated than the pharmaceutical industry. The top 10 companies, led by Syngenta, Switzerland; Bayer Cropsciences, Germany: Monsanto, USA; BASF Crop Protection, Germany, and Dow Agrosciences, USA have a share of almost 95% of the total 2,000,000 tons / $48.5 billion pesticide output in 2010. Since the 1990s, the R&D effort has been focused mainly on gene modified (GM) seeds. At both Monsanto and DuPont's seed subsidiary, Pioneer Hi-Bred, the GM seed businesses already account for more than 50% of total sales. 100 new LMW agrochemicals were launched between 2000–2009. However, only 8 products achieved sales in excess of $100 million per year. Generics play a bigger role in the agro than in the pharma industry. They represent some 70% of the global market. China National Chemical Corp is the world's largest supplier of generic farm chemicals. Mahkteshim Agan, Israel, and Cheminova, Denmark, rank second and third. Apart from these multibillion-dollar companies, there are hundreds of smaller firms with sales of less than $50 million per year, mainly in India and China. The incidence of the cost of the active ingredient is about 33%, much higher than in drugs.
Serena Michelle Best , is a British academic, and the Professor of Materials Science at the University of Cambridge. Best has a BSc from the University of Surrey, and a PhD from the University of London. She was elected Fellow of the Royal Academy of Engineering (FREng) in 2012. In the 2017 Birthday Honours, Best was made a CBE, "For services to Biomaterials Engineering." Best was President of the Institute of Materials, Minerals and Mining from 2019 to 2020.
=== Anxiety disorders === Escitalopram appears to be effective in treating generalized anxiety disorder, with relapse on escitalopram at 20% rather than placebo at 50%, which translates to a number needed to treat of 3.33. Escitalopram appears effective in treating social anxiety disorder as well.
=== Non-regional === In addition to the regional senses, a spatula can be used in both British and American English to refer to a tool with a flat, blunt blade used for mixing and spreading things as opposed to one used for lifting and flipping food, an example of which is the rubber scraper shown on the right.
You must know that, for my part, there would be none, determined as I am to leave the command in this next Congress, but who can mitigate the ambition of our leaders and the fear of inequality among the lowly people? Don't you think that England would be jealous of the choice made in a Bourbon? How much would not be opposed by all the new American states, and the United States that seem destined by Providence to plague America with miseries in the name of Liberty? It seems to me that I already see a general conspiracy against this poor Colombia, already too envied by all the Republics America has. All the presses would be in motion calling for a new crusade against the accomplices of treason against freedom, addicts of the Bourbons and violators of the American system. In the South, the Peruvians would ignite the flame of discord; by the Isthmus those of Guatemala and Mexico, and by the Antilles the Americans and the liberals of all parts. Santo Domingo would not stay idle and call his brothers to make common cause against a prince of France. They would all become enemies without Europe doing anything to support us, because the New World is not worth the expense of a Holy Alliance; At least, we have reason to judge so, due to the indifference with which we have been seen to undertake and fight for the emancipation of half the world, which very soon will be the most productive source of European prosperity.
Sources: en.wikipedia.org
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.
Reduced pressure lowers the boiling point of water and allows ice to sublime below its triple point. Without sufficient vacuum, melting or boiling may occur instead of sublimation, which can damage the product structure.
Heat and mass transfer limit drying once the ice front recedes. The dried layer insulates the frozen core and resists vapor flow, so increasing shelf temperature too quickly can cause collapse or meltback.
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.