sublimation is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-04-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
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.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
| Property | Value | Notes |
|---|---|---|
| Appearance | Porous, uniform cake or powder | Collapsed or shrunken cakes indicate process issues. |
| Reconstitution time | Seconds to several minutes | Depends on cake porosity, excipients, and diluent. |
| Residual moisture | 0.5-3% w/w | Product-specific; measured by Karl Fischer titration. |
| Typical storage temperature | 2-25 °C | Some biologics require 2-8 °C. |
| Container closure | Glass vial with elastomeric stopper | Sealed under vacuum or inert gas. |
Storage stability depends on water content, oxygen exposure, and temperature. Lyophilized solids are hygroscopic and can absorb water if exposed to humid air. Vials are usually sealed under vacuum or inert gas with rubber stoppers and aluminum crimps. Storage temperatures range from room temperature to refrigerated or frozen conditions depending on the material. Stability studies track potency, moisture, and physical form over time. Accelerated conditions can reveal sensitivity but may not predict long-term behavior.
Analytical methods for lyophilized materials include X-ray diffraction for crystallinity, differential scanning calorimetry for thermal transitions, and scanning electron microscopy for pore morphology. Moisture sorption analysis shows how the cake responds to humidity. These methods help distinguish amorphous from crystalline states and detect phase changes. Open questions remain about how pore structure changes during long-term storage and how best to predict collapse under varied conditions. Comparisons across studies are complicated by differences in formulation, cycle, and storage history.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
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.
Malolactic fermentation is possibly as old as the history of wine, but scientific understanding of the positive benefits of MLF and control of the process is a relatively recent development. For many centuries, winemakers noticed an "activity" that would happen in their wines stored in barrel during the warm spring months following harvest. Like primary alcoholic fermentation, this phenomenon would release carbon dioxide gas and seem to have a profound change on the wine that was not always welcomed. It was described as a "second fermentation" in 1837 by the German enologist Freiherr von Babo and the cause for increased turbidity in the wine. Von Babo encouraged winemakers to quickly respond at the first sight of this activity by racking the wine into a new barrel, adding sulfur dioxide, and then following up with another set of racking and sulfuring to stabilize the wine. In 1866, Louis Pasteur, one of the pioneers of modern microbiology, isolated the first bacteria from wine and determined that all bacteria in wine were a cause for wine spoilage. While Pasteur did notice an acid reduction in wine with the lactic bacteria, he did not link that process to a consumption of malic acid by the bacteria, but rather assumed it was just tartrate precipitation. In 1891, the Swiss enologist Hermann Müller theorized that bacteria may be the cause of this reduction. With the aid of peers, Müller explained his theory of "biological deacidication" in 1913 to be caused by wine bacterium Bacterium gracile.
==== Louis Vuitton fashion shows ==== Williams was hand-selected to be the new creative director of menswear at luxury fashion house Louis Vuitton in 2023. In a story with the New York Times about the job and his upcoming debut fashion show with the brand, an unheard song with Pusha T ("Chains & Whips") was teased, although it was not yet revealed as a Clipse song. The three annual spring–summer shows from this point until Let God Sort Em Out's release all featured new Clipse music in their soundtracks, along with other songs. "Chains & Whips" was debuted at the Louis Vuitton's Men's Spring–Summer Show 2024 on June 20, 2023, although Kendrick Lamar's guest verse was not yet included. Pusha T and Malice also walked on the runway in Williams's designs. For the Men's Spring–Summer Show 2025 on June 18, 2024, "The Birds Don't Sing" was previewed for the first time, featuring vocals by John Legend. The Men's Spring–Summer Show 2026 debuted "So Be It Pt. II" on June 24, 2025.
The units use strontium-90, and a larger number of such units have been deployed both on the ground and on the ocean floor than have been used on spacecraft, with public regulatory documents suggesting that the US had deployed at least 100–150 during the 1970s and 1980s. In the past, small "plutonium cells" (very small 238Pu-powered RTGs) were used in implanted heart pacemakers to ensure a very long "battery life". As of 2004, about ninety were still in use. By the end of 2007, the number was reported to be down to just nine. The Mound Laboratory Cardiac Pacemaker program began on 1 June 1966, in conjunction with NUMEC. The program was cancelled in 1972, when it was recognized that the heat source would not remain intact during cremation and there was no way to completely ensure that the units would not be cremated with their users' bodies.
Sources: en.wikipedia.org
Ring A is then expanded via the polyketide synthase pathway to incorporate L-serine into ring B (figure 3). Ring A fragment is transferred from the peptidyl carrier protein (PCP) to the acyl carrier protein (ACP) by a keto-synthase (KS) domain, followed by transfer to malonyl-ACP via decarboxylative Claisen condensation catalysed by the enzyme pigJ. This fragment is then able to react with the masked carbanion formed from the pyridoxal phosphate (PLP) mediated decarboxylation of L-serine, which cyclizes in a dehydration reaction to yield the second pyrrole ring. This intermediate is then modified by oxidation of the primary alcohol to the aldehyde, catalysed by pigM, and methylation (which incorporates a methyl group from L-methionine onto the alcohol at the 6-position) catalysed by pigF and pigN. This yields the core A-B ring structure ready for further transformations, including to the tambjamines as well as the prodiginines.
Amyloids are aggregates of proteins characterised by a fibrillar morphology of typically 7–13 nm in diameter, a β-sheet secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the human body, amyloids have been linked to the development of various diseases. Pathogenic amyloids form when previously healthy proteins lose their normal structure and physiological functions (misfolding) and form fibrous deposits within and around cells. These protein misfolding and deposition processes disrupt the healthy function of tissues and organs. Such amyloids have been associated with (but not necessarily as the cause of) more than 50 human diseases, including amyloidosis, and may play a role in some neurodegenerative diseases. Some of these diseases are mainly sporadic and only a few cases are familial. Others are only familial. Some result from medical treatment. Prions are an infectious form of amyloids that can act as a template to convert other non-infectious forms. Amyloids may also have normal biological functions; for example, in the formation of fimbriae in some genera of bacteria, transmission of epigenetic traits in fungi, as well as pigment deposition and hormone release in humans. Amyloids have been known to arise from many different proteins. These polypeptide chains generally form β-sheet structures that aggregate into long fibers; however, identical polypeptides can fold into multiple distinct amyloid conformations. The diversity of the conformations may have led to different forms of the prion diseases.
is the number of amino acid residues, R1 is the first residue of the protein P, R2 is the second residue, and so forth. The problem with this approach was that in some sequence-similarity-search-based tools, the query protein often lacked significant homology (or sequence similarity) with any other known protein in the database. To resolve this problem, discrete models for representing protein samples were proposed. The simplest discrete model is using the amino acid composition (AAC) to represent protein samples. Under the AAC model, the protein P of Eq.1 can also be expressed by
== Analogue controls == Several jurisdictions have implemented analogue law controls of fentanyl analogues in an attempt to pre-emptively ban novel derivatives before they appear on the market. One representative example is the New Zealand provisions enacted in 1988 in response to the first wave of fentanyl derivatives. This bans a set of structures as follows; "Fentanyl analogues, in which the N-[1-(2-phenethyl)-4-piperidyl]aniline nucleus has additional radicals, either alone or in combination, attached as follows: (a) an acetyl, propionyl, butenoyl or butanoyl radical, attached to the aniline nitrogen atom: (b) 1 or more alkyl radicals, with up to 10 carbon atoms in total, attached to the ethyl moiety: (c) any combination of up to 5 alkyl radicals and/or alkoxy radicals (each with up to 6 carbon atoms, including cyclic radicals) and/or halogen radicals, attached to each of the benzene rings." A more recent and somewhat broader example was introduced into US Federal legislation in 2018, covering the following structures; "...fentanyl-related substances includes any substance not otherwise controlled in any schedule...that is structurally related to fentanyl by one or more of the following modifications:
Sources: en.wikipedia.org
==== 2400–2499 ==== County Council of Clwyd (River Dee Estuary Bridge) Scheme 1992 Confirmation Instrument 1993 (S.I. 1993/2400) Environmental Protection (Prescribed Processes and Substances) (Amendment) (No. 2) Regulations 1993 (S.I. 1993/2405) Offshore Safety Act 1992 (Commencement No. 1) Order 1993 (S.I. 1993/2406) Leasehold Reform (Collective Enfranchisement and Lease Renewal) Regulations 1993 (S.I. 1993/2407) Rent Assessment Committee (England and Wales) (Leasehold Valuation Tribunal) Regulations 1993 (S.I. 1993/2408) Leasehold Reform (Notices) (Amendment) Regulations 1993 (S.I. 1993/2409) Local Government and Housing Act 1989 (Commencement No. 16) Order 1993 (S.I. 1993/2410) National Health Service (General Medical Services) Amendment (No. 2) Regulations 1993 (S.I. 1993/2421) Environmentally Sensitive Areas (Ynys Mo*n) Designation (Amendment) Order 1993 (S.I. 1993/2422) Patents (Amendment) Rules 1993 (S.I. 1993/2423) Pembrokeshire National Health Service Trust (Transfer of Trust Property) Order 1993 (S.I. 1993/2436) Strathclyde Region (Electoral Arrangements) Order 1993 (S.I. 1993/2439) Finance Act 1993, Section 18, (Appointed Day) Order 1993 (S.I. 1993/2446) National Health Service (General Medical and Pharmaceutical Services) (Scotland) Amendment (No. 2) Regulations 1993 (S.I. 1993/2449) Social Fund Cold Weather Payments (General) Amendment Regulations 1993 (S.I. 1993/2450) National Health Service (Pharmaceutical Services) Amendment Regulations 1993 (S.I. 1993/2451) Vehicles Excise Duty (Simplification of Goods Vehicles Rates) Order 1993 (S.I.
Kendall was elected to the United States National Academy of Sciences in 1950, and both the American Academy of Arts and Sciences and the American Philosophical Society in 1951. Kendall's career at Mayo ended in 1951, when he reached mandatory retirement age. He moved on to Princeton University, where he was a visiting professor in the Department of Biochemistry. He remained affiliated with Princeton until his death in 1972. In addition to the Nobel Prize, Kendall received other major awards including the Lasker Award, the Passano Foundation Award and the Cameron Prize for Therapeutics of the University of Edinburgh. Kendall received the Golden Plate Award of the American Academy of Achievement in 1966. He was awarded honorary doctorates from the University of Cincinnati, Western Reserve University, Williams College, Yale University, Columbia University, National University of Ireland, and Gustavus Adolphus College.
The foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; it contains a hydrophilic polar head and a hydrophobic nonpolar tail. The phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for ions and molecules. There are various types of phospholipids; consequently, their synthesis pathways differ. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane. The synthesis pathway is found below:
== Composition history == The original commission for Higdon to compose her first opera, in collaboration with Scheer as librettist, came from the San Francisco Opera. Over the period of 2009 to 2011, the creators had searched for various subjects to adapt, which led to the choice of the novel Cold Mountain. However, complications related to securing the rights to adapt the novel, along with conflicts over financial demands and reports of clashes of working style with San Francisco Opera with respect to the creation of new operas, led to the lapsing of this commission. Santa Fe Opera subsequently rescued this commission, in conjunction with the Opera Company of Philadelphia (now Opera Philadelphia) and the Minnesota Opera. Scheer began to write the libretto in autumn 2011, and Higdon began to compose the music in 2012. Higdon used her personal background of having lived in the Appalachia region of the US to assist Scheer with rendering portions of his libretto in a style of speech more authentic to the region, when needed: "I helped Gene 'southernize' the libretto. Gene's from New York, and he wasn't sure how to shape the language for the characters, so I took care of it. Those speech patterns felt very familiar. Scheer estimated that 20 to 25% of the sung text in his libretto came directly from lines in the novel. Higdon took 20 months to complete her score. Workshops of the opera at the Curtis Institute of Music occurred in December 2012 for act 1 and in December 2013 for act 2. In advance of the premiere, four of the five scheduled Santa Fe Opera performances sold out.
Human rights in the Soviet Union were severely limited. The Soviet Union was a totalitarian state from 1927 until 1953 and a one-party state until 1990. Freedom of speech was suppressed and dissent was punished. Independent political activities were not tolerated, whether these involved participation in free labour unions, private corporations, independent churches or opposition political parties. The freedom of movement within and especially outside the country was limited. The state restricted rights of citizens to private property.
Sources: en.wikipedia.org
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.
Storage temperature is set by the least stable component in the formulation. Proteins, vaccines, and some small molecules can degrade faster at higher temperatures. Refrigeration slows these changes but does not stop them completely.
Collapse occurs when the product exceeds its collapse or glass transition temperature during drying. The ice structure then loses support, and the cake may shrink, melt back, or become dense. Formulation and cycle adjustments are used to keep the product below that threshold.
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.