The short version of collapse temperature fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
| 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. |
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.
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.
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.
RBR: 04 × 1.62 Gbit/s = 06.48 Gbit/s bandwidth (data rate of 5.184 Gbit/s or 648 MB/s with 8b/10b encoding) HBR: 04 × 2.70 Gbit/s = 10.80 Gbit/s bandwidth (data rate of 8.64 Gbit/s or 1.08 GB/s) HBR2: 4 × 5.40 Gbit/s = 21.60 Gbit/s bandwidth (data rate of 17.28 Gbit/s or 2.16 GB/s) HBR3: 4 × 8.10 Gbit/s = 32.40 Gbit/s bandwidth (data rate of 25.92 Gbit/s or 3.24 GB/s) UHBR 10: 4 × 10.0 Gbit/s = 40.00 Gbit/s bandwidth (data rate of 38.69 Gbit/s or 4.84 GB/s with 128b/132b encoding and FEC) UHBR 13.5: 4 × 13.5 Gbit/s = 54.00 Gbit/s bandwidth (data rate of 52.22 Gbit/s or 6.52 GB/s) UHBR 20: 4 × 20.0 Gbit/s = 80.00 Gbit/s bandwidth (data rate of 77.37 Gbit/s or 9.69 GB/s) The transmission mode used by the DisplayPort main link is negotiated by the source and sink device (the device accepting the signal) when a connection is made, through a process called Link Training. This process determines the maximum possible speed of the connection. If the quality of the DisplayPort cable is insufficient to reliably handle HBR2 speeds for example, the DisplayPort devices will detect this and switch down to a lower mode to maintain a stable connection. The link can be re-negotiated at any time if a loss of synchronization is detected. Audio data is transmitted across the main link during the video blanking intervals (short pauses between each line and frame of video data).
Activation of presynaptic dopamine autoreceptors by dihydroergocriptine leads to reduced dopamine receptor turnover and indirect antioxidant effects. In particular, further activation of intracellular kinase systems due to dopamine agonists are hypothesized to lead to antiapoptotic effects that also help in halting and slowing the disease progression. This may also contribute to prevention of development of motor fluctuations, though more research is needed. Modern agonists like dihydroergocryptine typically cost two to three times more than levodopa therapy. More health economics assessments may be needed to determine whether the initial increased costs of the agonists are offset by less patients needing surgery in later stages of the disease.
Convulxin is a snake venom toxin found in a tropical rattlesnake known as Crotalus durissus terrificus. It belongs to the family of hemotoxins, which destroy red blood cells or, as is the case with convulxin, induce blood coagulation. It causes platelet activation in the blood, forming clots and buildup of pressure. Convulxin acts as an agonist to the GPVI receptor, the major signalling receptor for collagen. This can cause the blood stream to burst, or the heart or brain to lose blood, thus resulting in death. It is a tetramer C-type lectin with an oligomeric structure, made up of heterodimeric subunits.
They concluded more experimental research is needed to investigate the toxicity of mephedrone. Doctors who treated a 15-year-old female suffering from mephedrone intoxication suggested in The Lancet that, like MDMA, mephedrone may promote serotonin-mediated release of antidiuretic hormone, resulting in hyponatraemia and an altered mental state. In another case, a 19-year-old male was admitted to hospital suffering from inflammation of the heart, 20 hours after taking one gram of mephedrone. The doctors treating the patient stated it was caused by either a direct toxic effect of mephedrone on the heart muscle, or by an immune response. One case of acquired methaemoglobinaemia, where a patient had "bluish lips and fingers", has also been reported, after the user snorted one gram of mephedrone. The patient started to recover after arriving at the hospital and it was not necessary to administer any medication.
Here, a, b, and c are lattice constants in picometers, No is the space group number, and Z is the number of formula units per unit cell; fcc stands for the face-centered cubic symmetry. Density was not measured directly but calculated from the lattice parameters.
Sources: en.wikipedia.org
Nicotine is the active chemical constituent in tobacco, which is available in many forms, including cigarettes, cigars, chewing tobacco, and smoking cessation aids such as nicotine patches, nicotine gum, and electronic cigarettes. Nicotine is used widely throughout the world for its stimulating and relaxing effects. Nicotine exerts its effects through the agonism of nicotinic acetylcholine receptors, resulting in multiple downstream effects such as increase in activity of dopaminergic neurons in the midbrain reward system, and acetaldehyde one of the tobacco constituent decreased the expression of monoamine oxidase in the brain. Nicotine is addictive and dependence-forming. Tobacco, the most common source of nicotine, has an overall harm to user and self score 3% below cocaine, and 13% above amphetamines, ranking 6th most harmful of the 20 drugs assessed, as determined by a multi-criteria decision analysis.
During the late 1980s, ADP-ribosyl cyclases, which catalyze the addition of cyclic-ADP-ribose groups to proteins, were discovered. Finally, sirtuins, a family of enzymes that also possess NAD+-dependent deacylation activity, were discovered to also possess mono(ADP-ribosyl)transferase activity.
This charge polarization within the molecule allows it to align with adjacent molecules through strong intermolecular hydrogen bonding, rendering the bulk liquid cohesive. Van der Waals gases such as methane, however, have weak cohesion due only to van der Waals forces that operate by induced polarity in non-polar molecules. Cohesion, along with adhesion (attraction between unlike molecules), helps explain phenomena such as meniscus, surface tension, and capillary action. Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the bottom of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave. Mercury will not wet the glass, unlike water and many other liquids, and if the glass is tipped, it will 'roll' around inside.
==== Outdoor areas with elevated concentrations ==== Local concentrations of carbon dioxide can reach high values near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot spring near Rapolano Terme in Tuscany, Italy, situated in a bowl-shaped depression about 100 m (330 ft) in diameter, concentrations of CO2 rise to above 75% overnight, sufficient to kill insects and small animals. After sunrise the gas is dispersed by convection. High concentrations of CO2 produced by disturbance of deep lake water saturated with CO2 are thought to have caused 37 fatalities at Lake Monoun, Cameroon in 1984 and 1700 casualties at Lake Nyos, Cameroon in 1986.
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.
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.