A practical reference on primary drying: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
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.
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 synonyms | freeze-drying, lyophilisation, cryodesiccation | Lyophilization is common in pharmaceutical literature. |
| Typical chamber pressure during primary drying | 0.05–0.5 mbar (5–50 Pa) | Must remain below the triple point of water. |
| Typical shelf temperature during freezing | −40 to −20 °C | Lower temperatures may be used for eutectic systems. |
| Typical residual moisture after secondary drying | 0.5–3% w/w | Product-dependent; low moisture improves stability but can cause over-drying. |
| Typical analytical method for residual moisture | Karl Fischer titration or loss on drying | Thermogravimetric methods are also used. |
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.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
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.
Integrin inside-out signaling in leukocytes and platelets correlates with large increases in actin polymerization and cellular shape changes upon activation. Most recently, ligand binding to integrins was shown to induce full conformational change within milliseconds, and to be the first step in integrin inside-out signaling.
== Etymology == In Hausa, the national language of Niger, the word fada literally refers to a royal court or chief's council of elders—composed of men—as well as their courtyard or meeting location. More broadly, the word refers to a place where people hold meetings. The word is used to refer to conversation groups that meet to drink tea, a usage that has been loaned into Zarma, commonly spoken in the city of Niamey. This definition encompasses all groups with such meetings, regardless of demographics, so a group of adult civil servants may be called a fada; however, the concept is primarily associated with young men. In Hausa, the plural of fada is fadodi, but the French-style plural, fadas, is more commonly used. A member of a fada is known as a fadantché, a unique linguistic formation.
Technetium is a chemical element; it has symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium is one of only two radioactive elements both preceded and succeeded in the periodic table by elements with stable forms, the other being promethium. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore (the most common source), or the product of neutron capture in molybdenum ores. This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between the two. The most common naturally occurring isotope is 99Tc, in traces only. Many of technetium's properties had been predicted by Dmitri Mendeleev before it was discovered; Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (Em). In 1937, technetium became the first predominantly artificial element to be produced, hence its name (from the Greek technetos, 'artificial', + -ium). One short-lived gamma-ray–emitting nuclear isomer, technetium-99m, is used in nuclear medicine for a wide variety of tests, such as bone cancer diagnoses. The ground state of the nuclide technetium-99 is used as a gamma-ray–free source of beta particles. Long-lived technetium isotopes produced commercially are byproducts of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods.
=== February === 3 February – Prime Minister Keir Starmer rejects an allegation that he broke COVID-19 regulations by having a voice coach present at a press conference where he responded to a Brexit deal negotiated by Boris Johnson. For the first time, Reform UK have led an opinion poll, after coming top with 25% in a YouGov poll for Sky News. Labour are second on 24%, with the Conservatives on 21%. Northern Ireland's Economy Minister, Conor Murphy steps down from the post and announces he will leave Stormont after being elected to the Irish Seanad. Caoimhe Archibald is appointed to replace him as Economy Minister. 4 February – BBC News reports that Jack Lopresti, the former Conservative MP for Filton and Bradley Stoke who lost the seat at the last general election has joined the Ukrainian military. Welsh Conservatives leader Darren Millar and his colleague Russell George miss a Senedd vote on the Eluned Morgan government's budget for 2025–26 because they have travelled to the United States for the annual National Prayer Breakfast. 5 February – Deputy Prime Minister Angela Rayner confirms that local elections in East Sussex, West Sussex, Essex, Thurrock, Hampshire, the Isle of Wight, Norfolk, Suffolk and Surrey will be delayed for a year to allow major local government reorganisations to take place. Four of the seven MPs suspended from the Labour Party for voting against the child benefit cap are readmitted to the party; they are Richard Burgon, Ian Byrne, Imran Hussain and Rebecca Long-Bailey.
=== Hepatocellular carcinoma === Hepatocellular carcinoma is the most common primary liver cancer, and the most common cause of death in people with cirrhosis. Screening using an ultrasound with or without cancer markers such as alpha-fetoprotein can detect this cancer and is often carried out for early signs which has been shown to improve outcomes.
Sources: en.wikipedia.org
=== Toxicity due to size of nanoparticles === Toxicity in certain systems can also be dependent on the size of the nanoparticle. AuNSs size 1.4 nm were found to be toxic in human skin cancer cells (SK-Mel-28), human cervical cancer cells (HeLa), mouse fibroblast cells (L929), and mouse macrophages (J774A.1), while 0.8, 1.2, and 1.8 nm sized AuNSs were less toxic by a six-fold amount and 15 nm AuNSs were nontoxic. There is some evidence for AuNP buildup after injection in in vivo studies, but this is very size dependent. 1.8 nm AuNPs were found to be almost totally trapped in the lungs of rats. Different sized AuNPs were found to build-up in the blood, brain, stomach, pancreas, kidneys, liver, and spleen. Biosafety and biokinetics investigations on biodegradable ultrasmall-in-nano architectures have demonstrated that gold nanoparticles are able to avoid metal accumulation in organisms through escaping by the renal pathway.
=== Mesoamerica === Lightweight concrete was designed and used for the construction of structural elements by the pre-Columbian builders who lived in a very advanced civilisation in El Tajin near Mexico City, in Mexico. A detailed study of the composition of the aggregate and binder show that the aggregate was pumice and the binder was a pozzolanic cement made with volcanic ash and lime.
The most common fault associated with malolactic fermentation is its occurrence when it is not desired. This could be for a wine that is meant to be acidic and fruity (such as Riesling) or it could be a wine that was previously thought to have gone through MLF and bottled only to have malolactic fermentation commence in the bottle. The outcome of this "in-bottle" fermentation is often gassy, hazy wine that can be unpalatable to consumers. Improvement in sanitation and control of lactic acid bacteria in the winery can limit the occurrence of these faults. For early Vinho Verde producers, the slight effervesce that came from in-bottle malolactic fermentation was considered a distinguishing trait that consumers enjoyed in the wine. However, wineries had to market the wine in opaque bottles to mask the turbidity and sediment that the "in-bottle MLF" produced. Today, most Vinho Verde producers no longer follow this practice and instead complete malolactic fermentation prior to bottle with the slight sparkle being added by artificial carbonation. While not necessarily a fault, malolactic fermentation does have the potential of making a wine "protein unstable" due to the resulting change in pH which affects the solubility of proteins in wine. For this reason, protein fining and heat stability tests on wine usually take place after malolactic fermentation has run to completion.
== Need for Platelet-mimicking particles == Despite the vital role of native platelets in hemostasis, their limitations - such as short shelf life, donor dependence, and transfusion-related risks - have presented a need for synthetic alternatives. These challenges inform the need for synthetic solutions that can replicate platelet functions while also minimizing these drawbacks and thus decrease adverse bleeding events. A primary limitation of native platelets is their limited shelf life, typically ranging from 5 to 7 days which complicates their storage and distribution. This short window increases the difficulty to maintain an adequate supply of platelets, especially in emergency situations or regions with limited access to donor blood. Additionally, platelet transfusions are associated with risks such as immune reactions, bacterial infections, and transmission of blood-borne diseases. These risks arise due to potential contamination during blood collection, processing, and storage. Given these challenges, synthetic platelets offer a solution by providing a longer-lasting and more accessible alternative.
Sources: en.wikipedia.org
=== 27 May === A spokeswoman for the German Defence Ministry confirmed that Ukraine had formally asked to be supplied with the Taurus KEPD 350 cruise missile. In Kharkiv Oblast, a woman was killed and another civilian was injured by Russian shelling in Kupiansk. Mikhail Vedernikov, Governor of Russia's Pskov Oblast, claimed that two drones struck an administrative building for a nearby oil pipeline, causing an explosion. No casualties were reported, however the building was damaged. The attack occurred less than ten kilometres from the Belarus border. In Kursk Oblast, a construction worker was reported to have been killed by Ukrainian shelling near the village of Plekhovo, a few kilometers from the international border. Another civilian, a security guard was killed by shelling in Shebekino, Belgorod Oblast. The Russian Defence Ministry claimed that its forces had intercepted two Storm Shadow missiles, 19 drones and several HIMARS and HARM missiles from Ukraine in the past 24 hours. The German Foreign Ministry confirmed that hundreds of its educational and cultural workers, including employees at the German school in Moscow and at the local branch of the Goethe Institute were to be expelled from Russia starting in June after it imposed a limit on the number of German employees in retaliation for the expulsion of Russian diplomats and staff from Germany.
=== Liver === The human liver is particularly known for its ability to regenerate, and is capable of doing so from only one quarter of its tissue, due chiefly to the unipotency of hepatocytes. Resection of liver can induce the proliferation of the remaining hepatocytes until the lost mass is restored, where the intensity of the liver's response is directly proportional to the mass resected. For almost 80 years surgical resection of the liver in rodents has been a very useful model to the study of cell proliferation.
For example, an officer of unit "A" does not directly command lower-ranking members of unit "B", and is generally expected to approach an officer of unit "B" if he requires action by members of that unit. The chain of command means that individual members take orders from only one superior and only give orders to a defined group of people immediately below them. If an officer of unit "A" does give orders directly to a lower-ranked member of unit "B", it would be considered highly unusual (i.e., a faux pas, or extraordinary circumstances, such as a lack of time or inability to confer with the officer in command of unit "B") as officer "A" would be seen as subverting the authority of the officer of unit "B". Depending on the situation or the standard procedure of the military organization, the lower-ranked member being ordered may choose to carry out the order anyway, or advise that it has to be cleared with their own chain of command first, which in this example would be with officer "B". Refusal to carry out an order is almost always considered insubordination; the only exception usually allowed is if the order itself is illegal (i.e., the person carrying out the order would be committing an illegal act). (See superior orders.) In addition, within combat units, line officers are in the chain of command, but staff officers in specialist fields (such as medical, dental, legal, supply, and chaplain) are not, except within their own specialty.
Sources: en.wikipedia.org
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.
Reduced pressure keeps the process below the triple point of water, so ice can sublimate directly to vapor. It also lowers the temperature needed for drying, which helps preserve heat-sensitive materials. Without vacuum, melting or boiling could occur instead of controlled sublimation.
The rate depends on heat transfer to the product and mass transfer of vapor through the dried layer. A cold condenser, adequate vacuum, and suitable shelf temperature all influence speed. Formulation properties such as solid content and collapse temperature also set practical limits.
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.