sublimation raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-11-28. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
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.
| 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 |
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
Biological molecular machines have been known and studied for decades given their vital role in sustaining life, and have served as inspiration for synthetically designed systems with similar useful functionality. The advent of conformational analysis, or the study of conformers to analyze complex chemical structures, in the 1950s gave rise to the idea of understanding and controlling relative motion within molecular components for further applications. This led to the design of "proto-molecular machines" featuring conformational changes such as cog-wheeling of the aromatic rings in triptycenes. By 1980, scientists could achieve desired conformations using external stimuli and utilize this for different applications. A major example is the design of a photoresponsive crown ether containing an azobenzene unit, which could switch between cis and trans isomers on exposure to light and hence tune the cation-binding properties of the ether. In his seminal 1959 lecture There's Plenty of Room at the Bottom, Richard Feynman alluded to the idea and applications of molecular devices designed artificially by manipulating matter at the atomic level. This was further substantiated by Eric Drexler during the 1970s, who developed ideas based on molecular nanotechnology such as nanoscale "assemblers", though their feasibility was disputed.
August 3 – Allan Nascimento, 34, mixed martial artist (UFC). August 18 – Glória Menezes, 91, actress. September 9 – Jackson Nascimento, 102, football player (Athletico Paranaense, Corinthians) and manager (Athletico Paranaense). September 14 – Aracy Amaral, 96, art historian and curator, director of the Pinacoteca do Estado de São Paulo (1975–1979) and the Museum of Contemporary Art, University of São Paulo (1982–1986). September 15 – Amelinha Teles, 81, journalist and political activist. Paulo César Martin, 62, journalist and radio host (Folha de S.Paulo, TV Globo, Conrad Editora). September 22 – Rick Sollo, 59, singer-songwriter (Rick & Renner) and Sertanejo music producer. September 26 – Pedro Antônio Marchetti Fedalto, 100, Roman Catholic prelate, auxiliary bishop (1966–1970) and archbishop (1970–2004) of Curitiba.
=== Protection === The lungs possess several characteristics which protect against infection. The respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus. This mucociliary clearance is an important defence system against air-borne infection. The dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia. The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants. The size of the respiratory tract and the flow of air also protect the lungs from larger particles. Smaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.
A compound is a pure chemical substance composed of more than one element. The properties of a compound bear little similarity to those of its elements. The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compounds are named according to the organic nomenclature system. The names for inorganic compounds are created according to the inorganic nomenclature system. When a compound has more than one component, then they are divided into two classes, the electropositive and the electronegative components. In addition the Chemical Abstracts Service (CAS) has devised a method to index chemical substances. In this scheme each chemical substance is identifiable by a number known as its CAS registry number.
Sources: en.wikipedia.org
Up to 80% of people affected by bacterial tracheitis require the use of mechanical ventilation, and treatment may include endoscopy for the purposes of acquiring microbiological specimens for culture and sensitivity, as well as removal of any dead tissue associated with the infection. Treatment in such situations usually includes antibiotics.
In pharmacokinetics, a loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose. A loading dose is most useful for drugs that are eliminated from the body relatively slowly, i.e., which have a long systemic half-life. Such drugs need only a low maintenance dose in order to keep the amount of the drug in the body at the appropriate therapeutic level, but this also means that, without an initial higher dose, it would take a long time for the amount of the drug in the body to reach that level. Drugs which may be started with an initial loading dose include digoxin, teicoplanin, voriconazole, procainamide and fulvestrant. One or a series of doses may be given at the onset of therapy with the aim of achieving the target concentration rapidly.
== Causes == Exogenous ochronosis can be caused from long-term use of certain "skin-lightening" products, even if the hydroquinone is in amounts as small as 2%. Skin-lightening products are still prevalent in many parts of the world. This may be due to aesthetic or social-standing reasons, in areas where a lighter skin tone is considered to be a sign of wealth or beauty. Also, skin-lightening creams containing compounds such as hydroquinone are commonly used to help with hyperpigmentation disorders such as melasma. Hydroquinone is the compound most frequently used in skin-whitening products. Due to concerns about its side effects, it was almost banned by the FDA in 2006, as medical issues of carcinogenicity and reports of disfiguring ochronosis existed. In the European Union hydroquinone has been banned in cosmetic creams since 2000. Long-term use of creams containing this compound may lead to exogenous ochronotic lesions. The duration of use is directly proportional to the risk of developing the condition, with most cases occurring after years of use. Around 10–15 million skin lightening products are sold annually, with Japan being the major buyer.
When this was made illegal, the cathinone was modified, and the new products were sold by the Israeli company Neorganics. The products had names such as Neodoves pills, but the range was discontinued in January 2008 after the Israeli government made mephedrone illegal. The Psychonaut Research Project, an EU organisation that searches the internet for information regarding new drugs, first identified mephedrone in 2008. Their research suggested the drug first became available to purchase on the internet in 2007, made available through British contacts, contact unknown, when it was also discussed on internet forums. Mephedrone was first seized in France in May 2007, after police sent a tablet they assumed to be ecstasy to be analysed, with the discovery published in a paper titled "Is 4-methylephedrone, an "Ecstasy" of the twenty-first century?" Mephedrone was reported as having been sold as ecstasy in the Australian city of Cairns, along with ethylcathinone, in 2008. An annual survey of regular ecstasy users in Australia in 2010 found 21% of those surveyed had used mephedrone, with 17% having done so in the previous six months. The price they paid per gram varied from A$16 to $320. Europol noted they became aware of it in 2008, after it was found in Denmark, Finland and the UK. The Drug Enforcement Administration noted it was present in the United States in July 2009. By May 2010, mephedrone had been detected in all 22 EU member states that reported to Europol, as well as in Croatia and Norway.
Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Professor Marshall Urist and Professor Hari Reddi discovered their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body. The important functioning of BMP signals in physiology is emphasized by the multitude of roles for dysregulated BMP signalling in pathological processes. Cancerous disease often involves misregulation of the BMP signalling system. Absence of BMP signalling is, for instance, an important factor in the progression of colon cancer, and conversely, overactivation of BMP signalling following reflux-induced esophagitis provokes Barrett's esophagus and is thus instrumental in the development of esophageal adenocarcinoma. Recombinant human BMPs (rhBMPs) are used in orthopedic applications such as spinal fusions, nonunions, and oral surgery. rhBMP-2 and rhBMP-7 are Food and Drug Administration (FDA)-approved for some uses. rhBMP-2 causes more overgrown bone than any other BMPs and is widely used off-label.
Sources: en.wikipedia.org
Business biomimetics is the latest development in the application of biomimetics. Specifically it applies principles and practice from biological systems to business strategy, process, organization design, and strategic thinking. It has been successfully used by a range of industries in FMCG, defense, central government, packaging, and business services. Based on the work by Phil Richardson at the University of Bath the approach was launched at the House of Lords in May 2009. Generally, biometrics is used as a creativity technique that studies biological prototypes to get ideas for engineering solutions. In chemistry, a biomimetic synthesis is a chemical synthesis inspired by biochemical processes. Another, more recent meaning of the term bionics refers to merging organism and machine. This approach results in a hybrid system combining biological and engineering parts, which can also be referred as a cybernetic organism (cyborg). Practical realization of this was demonstrated in Kevin Warwick's implant experiments bringing about ultrasound input via his own nervous system.
=== Elderly === Additional caution is required in the elderly, as they are more sensitive to the pharmacological effects of benzodiazepines, metabolise them more slowly, and are more prone to adverse effects, including drowsiness, amnesia (especially anterograde amnesia), ataxia, hangover effects, confusion, and falls.
Glipizide, sold under the brand name Glucotrol among others, is an anti-diabetic medication of the sulfonylurea class used to treat type 2 diabetes. It is used together with a diabetic diet and exercise. It is not indicated for use by itself in type 1 diabetes. It is taken by mouth. Effects generally begin within half an hour and can last for up to a day. Common side effects include nausea, diarrhea, low blood sugar, and headache. Other side effects include sleepiness, skin rash, and shakiness. The dose may need to be adjusted in those with liver or kidney disease. Use during pregnancy or breastfeeding is not recommended. It works by stimulating the pancreas to release insulin and increases tissue sensitivity to insulin. Glipizide was approved for medical use in the United States in 1984. It is available as a generic medication. In 2023, it was the 42nd most commonly prescribed medication in the United States, with more than 15 million prescriptions.
====== Fatty acid ethoxylates ====== Fatty acid ethoxylates are a class of very versatile surfactants, which combine in a single molecule the characteristic of a weakly anionic, pH-responsive head group with the presence of stabilizing and temperature responsive ethyleneoxide units.
are perpendicular if and only if the tangential quadrilateral also has a circumcircle (it is bicentric). have equal lengths if and only if the tangential quadrilateral is a kite. The tangency chord between the sides AB and CD in a tangential quadrilateral ABCD is longer than the one between the sides BC and DA if and only if the bimedian between the sides AB and CD is shorter than the one between the sides BC and DA. If tangential quadrilateral ABCD has tangency points W on AB and Y on CD, and if tangency chord WY intersects diagonal BD at M, then the ratio of tangent lengths
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.
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.