If you have been reading about Sublimation and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-01-23. Numbers and descriptions here follow the published literature rather than marketing material.
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.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
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.
| Property | Value | Notes |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
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.
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 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.
=== Stress === Smokers report higher levels of everyday stress. Several studies have monitored feelings of stress over time and found reduced stress after quitting. The deleterious mood effects of everyday between-cigarette nicotine withdrawal symptoms explain why people who smoke experience more daily stress than non-smokers, and become less stressed when they quit smoking. Deprivation reversal also explains much of the arousal data, with deprived smokers being less vigilant and less alert than non-deprived smokers or non-smokers. Recent studies have shown a positive relationship between psychological distress and salivary cotinine levels in smoking and non-smoking adults, indicating that both first-hand and second-hand smoke exposure may lead to higher levels of mental stress.
=== 28 March === German Minister of Defence Boris Pistorius stated that 18 Leopard 2A6 tanks had arrived in Ukraine. Ukrainian Defence spokeswoman Iryna Zolotar confirmed the arrival of British Challenger 2 tanks.
A patient's genome may include an inherited or random mutation which affects the probability of developing a disease in the future. For example, Lynch syndrome is a genetic disease that predisposes patients to colorectal and other cancers; early detection can lead to close monitoring that improves the patient's chances of a good outcome. Cardiovascular risk is indicated by biological markers and screening can measure the risk that a child will be born with a genetic disease such as Cystic fibrosis. Genetic testing is ethically complex: patients may not want the stress of knowing their risk. In countries without universal healthcare, a known risk may raise insurance premiums.
== Mass spectrometry == The tropylium ion is frequently encountered in mass spectrometry in the form of a signal at m/z = 91 and is used in mass spectrum analysis. This fragment is often found for aromatic compounds containing a benzyl unit. Upon ionization, the benzyl fragment forms a cation (PhCH+2), which rearranges to the highly stable tropylium cation (C7H+7).
Sources: en.wikipedia.org
28 September The 15-year-old girl killed in Croydon, South London the previous day is named locally as Elianne Andam. Police are given an extra 24 hours to question the 17-year-old suspect. The landmark Sycamore Gap Tree, beside Hadrian's Wall in Northumberland, is illegally felled. A 16-year-old boy is subsequently arrested on suspicion of criminal damage. 29 September A school bus carrying 58 people overturns between junction 4 and 5 of the M53 motorway, killing a 15-year-old girl and the driver. A major incident is declared by North West Ambulance Service and Liverpool's Alder Hey Children's Hospital. Dozens of others are treated for injuries, and several are hospitalised. A 17-year-old boy appears in court charged with the murder of Elianne Andam, and is remanded in youth detention to appear before the Old Bailey on 3 October. A second person – a man in his 60s – is arrested in correction with the cutting-down of the world-famous Sycamore Gap Tree. The 16-year-old boy arrested over the incident the previous day is released on bail. In an interview with The Sun, Prime Minister Rishi Sunak reinforces his pro-motorist stance, saying he wants to stop "hare-brained" road calming and safety schemes – including 20 mph zones and low-traffic neighbourhoods – putting an end to what he refers to as a "war on motorists".
In mammals, the vulva (pl. vulvas or vulvae) comprises mostly external, visible structures of the female genitalia leading into the interior of the female reproductive tract. For humans, it includes the mons pubis, labia majora, labia minora, clitoris, vestibule, urinary meatus, vaginal introitus, hymen, and openings of the vestibular glands (Bartholin's and Skene's). The folds of the outer and inner labia provide a double layer of protection for the vagina (which leads to the uterus). While the vagina is a separate part of the anatomy, colloquially the term has often been used synonymously with vulva. Pelvic floor muscles support the structures of the vulva. Other muscles of the urogenital triangle also give support. Blood supply to the vulva comes from the three pudendal arteries. The internal pudendal veins give drainage. Afferent lymph vessels carry lymph away from the vulva to the inguinal lymph nodes. The nerves that supply the vulva are the pudendal nerve, perineal nerve, ilioinguinal nerve and their branches. Blood and nerve supply to the vulva contribute to the stages of sexual arousal that are helpful in the reproduction process. Following the development of the vulva, changes take place at birth, childhood, puberty, menopause and post-menopause. There is a great deal of variation in the appearance of the vulva, particularly in relation to the labia minora. The vulva can be affected by many disorders, which may often result in irritation. Vulvovaginal health measures can prevent many of these. Other disorders include a number of infections and cancers.
Change in nomenclature During the term of the fourth assembly on 18 July 1967, the house unanimously adopted and recommended that steps be taken by the state government to secure the necessary amendment to the Constitution of India to change the name of Madras State to Tamil Nadu. Accordingly, the Madras State (Alteration of Name) Act, 1968 (Central Act 53 of 1968) was passed by the Parliament of India and came into force on 14 January 1969. Consequently, the nomenclature "Madras Legislative Assembly" was changed to "Tamil Nadu Legislative Assembly". From 1967 onwards, the strength of the assembly continued to remain at 234 plus a nominated member. From 1952 to 1986, the state had a parliamentary system of government with two democratically elected houses, the Legislative Assembly and the Legislative Council. On 14 May 1986, the state government passed a resolution to abolish the legislative council in the state, which was then moved and adopted by the house. On 1 November 1986, Tamil Nadu became a state with a unicameral legislature, and since then, several times, the state government has taken steps to reconstitute the legislative council, but they have failed for so long. The Tamil Nadu Legislative Council has not been constituted in the state to date.
Zinc is an essential element for all known forms of life. In humans, zinc is required for the function of over 300 enzymes and 1000 transcription factors, and is stored and transferred in metallothioneins. It is the second most abundant trace metal in humans after iron. It is the only metal which appears in all enzyme classes. In proteins, zinc ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult. Roughly 2–4 grams of zinc are distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye. Semen contains a particularly high amount of zinc, a key factor in prostate gland function and reproductive organ growth. Zinc homeostasis of the body is mainly controlled by the intestine. Here, ZIP4 and especially TRPM7 were linked to intestinal zinc uptake essential for postnatal survival. In humans, the biological roles of zinc are ubiquitous. It interacts with "a wide range of organic ligands", and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A review from 2015 indicated that about 10% of human proteins (~3000) bind zinc, in addition to hundreds more that transport and traffic zinc; a similar in silico study in the plant Arabidopsis thaliana found 2367 zinc-related proteins.
== Other names == Drop sets and the technique also go by the names breakdowns, burnouts, descending sets, triple-drops (when a total of three different weights are used), down the rack or running the rack (when using dumbbells), up the stack (because with a weight machine, the pin is moved up the stack of plates with each drop in weight), strip sets (when you "strip" weights off the ends of a bar), or the stripping technique (so called because of "stripping" weight plates off with each drop in weight).
Sources: en.wikipedia.org
Papillomas and warts/verrucae: They are caused by various strains of the human papilloma virus (HPV) of which there are more than 100 strains but usually due to HPV types 6 and 11. Papillomas are mostly spiky, finger like projections, or cauliflower head rounded lobular shaped. Usually painless and singular. Verrucae usually appear on the lips. Verrucae vulgaris is associated with HPV types 2 and 4. HPV types 16 and 18, designated high risk due to association with cancers, do not present like this in the oral mucosa but as white patches. Multifocal epithelial hyperplasia (Heck disease) is rare, usually familial, swellings appear in multiples and are more common to some Native American and Inuit groups. Verruciform xanthoma, a rare lesion which may resemble papilloma, is often white due to hyperkeratosis, usually appear in 50-70 year age group, commonly on the gingivae. They may be mistaken for papilloma or verrucous leukoplakia but are benign.
In simplifications where the change in reaction quotient is solely due to the concentration changes, Qr is referred to as the mass-action ratio, and the ratio Qr/Keq is referred to as the disequilibrium ratio.
2 July Democratic senator George McGovern stated that he met with North Vietnamese and VC negotiators in Paris in May and that productive negotiations would not occur without the start of unconditional U.S. withdrawal and distancing from the South Vietnamese government.
== Further reading == Aird, William C. "Blood Endothelial Cells" in Endothelial Cells In Health and Disease. Boca Raton: Taylor & Francis, 2005. Milosevic, V., Edelmann, R.J., Fosse, J.H., Östman, A., Akslen, L.A. (2022). Molecular Phenotypes of Endothelial Cells in Malignant Tumors. In: Akslen, L.A., Watnick, R.S. (eds) Biomarkers of the Tumor Microenvironment. Springer, Cham. https://doi.org/10.1007/978-3-030-98950-7_3 Stem Cells, Therapeutic Applications by Mariusz Z. Ratajczak Advances in Experimental Medicine and Biology
Sources: en.wikipedia.org
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.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.