Sublimation comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
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.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
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.
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.
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.
=== LOCAL algorithm of Larget and Simon === The LOCAL algorithms offers a computational advantage over previous methods and demonstrates that a Bayesian approach is able to assess uncertainty computationally practical in larger trees. The LOCAL algorithm is an improvement of the GLOBAL algorithm presented in Mau, Newton and Larget (1999) in which all branch lengths are changed in every cycle. The LOCAL algorithms modifies the tree by selecting an internal branch of the tree at random. The nodes at the ends of this branch are each connected to two other branches. One of each pair is chosen at random. Imagine taking these three selected edges and stringing them like a clothesline from left to right, where the direction (left/right) is also selected at random. The two endpoints of the first branch selected will have a sub-tree hanging like a piece of clothing strung to the line. The algorithm proceeds by multiplying the three selected branches by a common random amount, akin to stretching or shrinking the clothesline. Finally the leftmost of the two hanging sub-trees is disconnected and reattached to the clothesline at a location selected uniformly at random. This would be the candidate tree. Suppose we began by selecting the internal branch with length
== Medical uses == The primary measure of efficacy in the clinical trials is three or more spontaneous complete bowel movements per week; a secondary measure is an increase of at least one complete spontaneous bowel movement per week. Further measures are improvements in PAC-QOL (a quality of life measure) and PAC-SYM (a range of stool, abdominal, and rectal symptoms associated with chronic constipation). Infrequent bowel movements, bloating, straining, abdominal pain, and defecation urge with inability to evacuate can be severe symptoms, significantly affecting quality of life. In three large clinical trials, 12 weeks of treatment with prucalopride 2 and 4 mg/day resulted in a significantly higher proportion of patients reaching the primary efficacy endpoint of an average of ≥3 spontaneous complete bowel movements than with placebo. There was also significantly improved bowel habit and associated symptoms, patient satisfaction with bowel habit and treatment, and HR-QOL in patients with severe chronic constipation, including those who did not experience adequate relief with prior therapies (>80% of the trial participants). The improvement in patient satisfaction with bowel habit and treatment was maintained during treatment for up to 24 months; prucalopride therapy was generally well tolerated. Small clinical trials suggested that prucalopride administration results in the 5-HT4 receptor agonism-associated memory enhancing in healthy participants improving their ability to recall and increasing neural activation in the hippocampus and functionally related areas.
Kidder's television debut was in an episode of Wojeck aired January 16, 1968, billed as "Margaret Kidder". She very shortly afterward adopted the name Margot Kidder, which she used for the rest of her life. She then made her film debut in a 49-minute film titled The Best Damn Fiddler from Calabogie to Kaladar (1968), a drama set in a Canadian logging community, which was produced by the Challenge for Change. Kidder's 1969 appearance in the episode "Does Anybody Here Know Denny?" on the Canadian drama series Corwin earned her a Canadian Film Award for "outstanding new talent." Kidder's first major feature was the 1969 American film Gaily, Gaily, a period comedy starring Beau Bridges, in which she portrayed a prostitute. She subsequently appeared in a number of TV drama series for the CBC, including guest appearances on Adventures in Rainbow Country, and a semi-regular role as a young reporter on McQueen, and as a panelist on Mantrap, which featured discussions centered on a feminist perspective.
Sources: en.wikipedia.org
Duterte accused David of being involved in illegal drugs and stealing church donations, after which the CBCP came to David's defense and vouched for his integrity. Citing continued criticism from Catholic bishops, Duterte's verbal attacks on the Catholic Church escalated in mid-2018 to early 2019, during which he challenged the Catholic Church to show evidence of the existence of God, while expressing his belief in "one Supreme God" and "a universal mind somewhere which controls the universe". In one of his harshest vitriol in June 2018, he remarked that God was "stupid" for permitting the serpent to tempt Eve in the creation story in the Bible; though the controversial statement was later clarified by his spokesperson as Duterte's "personal opinion", it contributed to Duterte's quarterly approval rating dipping to its lowest at 45%. Efforts by the Church to rally public support against the administration's war on drugs, however, were less effective due to Duterte's domestic popularity and high trust ratings.
=== Viruses === Brine pockets can support a wide variety of bacteria, and they are also home to high concentrations of marine viruses. Marine viruses in brine pockets may play a major role in regulating the population dynamics of their hosts and influencing biogeochemical cycles within the pocket. As viruses are highly specific to their hosts, viruses in brine pockets include bacteriophages, which infect bacteria, and archaeal viruses, which infect archaea. Algal viruses and other eukaryotic viruses can also be present in brine pockets, which influences the productivity and diversity of these microorganisms. Marine viruses in brine pockets can also influence biogeochemical processes by releasing nutrients through the lysis of infected cells, and by facilitating horizontal gene transfer between hosts. Infections caused by viruses can also trigger changes in the host metabolism, leading to altered nutrient uptake and production of metabolites, which in turn can influence the surrounding environment. The few studies on viral abundance and composition in brine pockets focus mainly on the diverse concentrations of viruses, separated by molecular size. Brine pockets in the Antarctic lakes have been found to have three groups of viruses at different abundances. In the Arctic waters, viral concentrations were found to vary from 1.6 to 82 × 106 ml−1, with the highest concentrations found in the coldest brine pockets (–24 to –31 °C).
=== Antimicrobial properties === CO2 at high pressures has antimicrobial properties. While its effectiveness has been shown for various applications, the mechanisms of inactivation have not been fully understood although they have been investigated for more than 60 years.
Sources: en.wikipedia.org
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.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.