Everything below concerns secondary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-07-07. Numbers and descriptions here follow the published literature rather than marketing material.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
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 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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
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.
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, 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.
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.
== Types == There are three primary and two secondary types of dialysis: hemodialysis (primary), peritoneal dialysis (primary), hemofiltration (primary), hemodiafiltration (secondary) and intestinal dialysis (secondary).
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=== Glycoproteins === Glycoproteins are conjugated proteins that consist of one or more carbohydrate groups bound to the polypeptide chain. Glycoproteins are generally the biggest groups of conjugated proteins. These carbohydrates are generally shorter polymers of monosaccharide that are covalently bonded. Glycoproteins can be found all around and in living organisms. They range from glycoproteins in cell surface membranes that constitute the glycocalyx, to important antibodies produced by leukocytes. The main function of glycoproteins is cell recognition and communication. They act as receptors and help cells interact with their environment by responding to different signals. In the immune system, glycoproteins work as antibodies to help the body recognize and destroy foreign organisms like bacteria and viruses. Glycoproteins also have other uses like Adhesion procedure, hormone activity, and protein stability.
Sources: en.wikipedia.org
== Incarceration == In January 2026, Agüero's lawyer Gustavo Nievas, submitted an emergency request to the courts asking for protective custody for Agüero. Nievas informed the judge, the penitentiary service and media, that Agüero was assaulted in September 2025 and who recently was threatened with a knife by prisoners convicted of bloodless crimes who do not share Agüero's criminal profile, with Nievas highlighting her as a "weak woman" and nonviolent. The request was accepted that same day.
=== Diagnostic criteria === An international group created a set of criteria for the diagnosis of primary Sjögren's disease in 2016 based on consensus around previous guidelines from the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR), which became known as the ACR-EULAR criteria. Although used primarily for recruitment into clinical trials, the criteria were shown to be effective in diagnosing Sjögren's by a 2025 Swedish cohort study. Per the ACR-EULAR criteria, a person with previously reported dry eye or dry mouth symptoms (including if responding positively to a short questionnaire) has SjD if they have a score of at least 4 when considering the following items:
Natural uranium (NU or Unat) is uranium with the same isotopic ratio as found in nature. It contains 0.711% uranium-235, 99.284% uranium-238, and a trace of uranium-234 by weight (0.0055%). Approximately 2.2% of its radioactivity comes from uranium-235, 48.6% from uranium-238, and 49.2% from uranium-234. Natural uranium can be used to fuel both low- and high-power nuclear reactors. Historically, graphite-moderated reactors and heavy water-moderated reactors have been fueled with natural uranium in the pure metal (U) or uranium dioxide (UO2) ceramic forms. However, experimental fuelings with uranium trioxide (UO3) and triuranium octaoxide (U3O8) have shown promise. The 0.72% uranium-235 is not sufficient to produce a self-sustaining critical chain reaction in light water reactors or nuclear weapons; these applications must use enriched uranium. Nuclear weapons take a concentration of 90% uranium-235, and light water reactors require a concentration of roughly 3% uranium-235. Unenriched natural uranium is appropriate fuel for a heavy-water reactor, like a CANDU reactor. On rare occasions, earlier in geologic history, when uranium-235 was more abundant, uranium ore was found to have naturally engaged in fission, forming natural nuclear fission reactors. Uranium-235 decays at a faster rate (half-life of 700 million years) compared to uranium-238, which decays extremely slowly (half-life of 4.5 billion years). Therefore, a billion years ago, there was more than double the uranium-235 compared to now.
Sources: en.wikipedia.org
They also made considerable advances in the field of surgery, often without the use of human dissection or animal vivisection. One of the earliest Ayurvedic treatises was the Sushruta Samhita, attributed to Sushruta in the 6th century BCE. It was also an early materia medica, describing 700 medicinal plants, 64 preparations from mineral sources, and 57 preparations based on animal sources.
August 2016, Amnesty International released a report tackling the issue of torture and ill-treatment in Syrian government prisons which amount to crimes against humanity. Since the crisis began in March 2011, the international organization estimated that 17,723 people have died in custody in Syria – an average rate of more than 300 deaths each month. According to the report, governmental forces have used torture to scare the opponents. But today, they use it as a part of systematic attack against opposition members. According to testimonies of some survivors, detainees were subjected to numerous kind of torture aiming at dehumanizing them, and in many cases killing them. Amnesty international said that those, who are responsible for these atrocities, must be brought to justice. In Sednaya Prison alone, up to 13,000 detainees were executed extrajudicially in secret between 2011 and 2015, mostly through mass-hangings. This was part of Assad's push to eliminate all dissent to his rule. On 6 July 2020, families of detainees in Syrian government prisons found the pictures of their dead relatives in the media graphics of a forensic police photographer-turned-whistleblower, codenamed, Caesar. The photos are among tens of thousands of images of torture victims, smuggled out of Syria in 2013. Numerous European citizens were also revealed to be among the torture victims.
=== Lactate dehydrogenase === Lactate dehydrogenase (LDH) is found in many body tissues, including the liver. Elevated levels of LDH may indicate liver damage. LDH isotype-1 (or cardiac) is used for estimating damage to cardiac tissue, although troponin and creatine kinase tests are preferred.
Sources: en.wikipedia.org
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.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
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.