This is a working overview of Sublimation, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-04-27 and is reviewed periodically as new material appears.
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.
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.
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.
| 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. |
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.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
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 is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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.
=== Designed proteins === Numerous protein structures are the result of rational design and do not exist in nature. Proteins can be designed from scratch (de novo design) or by making calculated variations on a known protein structure and its sequence (known as protein redesign). Rational protein design approaches make protein-sequence predictions that will fold to specific structures. These predicted sequences can then be validated experimentally through methods such as peptide synthesis, site-directed mutagenesis, or Artificial gene synthesis.
== Elastosis == Elastosis is the buildup of elastic fibers in tissues, and is a form of degenerative disease. There are a multitude of causes, but the most commons cause is actinic elastosis of the skin, also known as solar elastosis, which is caused by prolonged and excessive sun exposure, a process known as photoaging. Uncommon causes of skin elastosis include elastosis perforans serpiginosa, perforating calcific elastosis and linear focal elastosis.
=== Reproduction === The same specimen of S. prima which had preserved a lizard in its stomach contents (NIGP 127587) also had several small eggs in its abdomen. Two eggs were preserved just in front of and above the pubic boot, and several more may lie underneath them on the slab. It is unlikely that they were eaten by the animal, as they are in the wrong part of the body cavity for the egg shells to have remained intact. It is more likely that they are unlaid eggs produced by the animal itself, proving the specimen to be a female. Each egg measured 36 mm (1.4 in) long by 26 mm (1.0 in) wide. The presence of two developed eggs suggests that Sinosauropteryx had dual oviducts and laid eggs in pairs, like other theropods.
Sources: en.wikipedia.org
== Legal history == Some have suggested that US Supreme Court rulings related to the war on drugs have reinforced racially-disproportionate treatment. In United States v. Armstrong (1996), the Supreme Court heard the case of Armstrong, a black man charged with conspiring to possess and distribute more than 50 g of crack cocaine. Facing the District Court, Armstrong claimed that he was singled out for prosecution because of his race and he filed a motion for discovery. The District Court granted the motion, required the government to provide statistics from the last three years on similar crimes, and dismissed Armstrong's case after the government refused to do so. The government appealed the decision, and the US Court of Appeals affirmed the dismissal by holding that defendants in selective-prosecution claims did not have to demonstrate that the government had failed to prosecute similar cases. The case was then sent to the Supreme Court, which reversed the decision and held that defendants had to show that the government had failed to prosecute similar cases. In United States v. Bass (2002), the Supreme Court heard a similar case. John Bass was charged with two counts of homicide, and the government sought the death penalty. Bass filed for dismissal, along with a discovery request alleging that the death sentence was racially motivated. When the government refused to comply with the discovery request, the District Court dismissed the death penalty notice. Upon appeal, the US Court of Appeals affirmed the dismissal, and the case was sent to the Supreme Court.
=== Ministry of Finance === Horacio Cartes picked Peña to replace Germán Rojas as finance minister in 2015, following Rojas's resignation on personal grounds. As Peña took office, Cartes described him as a "bright young man" who would reinvigorate Paraguay's economy in the face of low global soy prices and a slow regional export market. As Minister of Finance in 2016 and 2017, Peña promoted the project to create the Superintendency of Retirements and Pensions. Peña indicated, “There have already been situations of embezzlement with the case of the Pension Fund of the Binational Itaipú (Cajubi).” The Itaipu Retirement and Pension Fund (Cajubi) and the Itaipu Workers' Union (STEIBI) opposed the project. In a joint press conference in November 2016, the two groups stated that they saw the plan as an “unconstitutional” violation, further describing the proposed legislation as “an imminent danger from a greedy person, who is looking for ways to extract money from people and who is the Minister of Finance.” On May 17, 2018, Cajubi's director and legal advisor, Adelio Dolores Aquino, presented Cajubi's position against the creation of a Superintendency on the TV Unicanal's program Sin Vueltas. As President, Peña continued to advocate for the creation of the Superintendency of Retirement and Pensions, arguing that it was necessary to prevent problems like the Cajubi case.
Nuclear DNA has two copies per cell (except for sperm and egg cells), one copy being inherited from the father and the other from the mother. Mitochondrial DNA, however, is inherited from the mother only (with some exceptions) and each mitochondrion typically contains between 2 and 10 mtDNA copies. During cell division the mitochondria segregate randomly between the two new cells. Those mitochondria make more copies, normally reaching 500 mitochondria per cell. As mtDNA is copied when mitochondria proliferate, they can accumulate random mutations, a phenomenon called heteroplasmy. If only a few of the mtDNA copies inherited from the mother are defective, mitochondrial division may cause most of the defective copies to end up in just one of the new mitochondria (for more detailed inheritance patterns, see human mitochondrial genetics). Mitochondrial disease may become clinically apparent once the number of affected mitochondria reaches a certain level; this phenomenon is called "threshold expression". Mitochondria possess many of the same DNA repair pathways as nuclei do—but not all of them; therefore, mutations occur more frequently in mitochondrial DNA than in nuclear DNA (see Mutation rate). This means that mitochondrial DNA disorders may occur spontaneously and relatively often. Defects in enzymes that control mitochondrial DNA replication (all of which are encoded for by genes in the nuclear DNA) may also cause mitochondrial DNA mutations. Most mitochondrial function and biogenesis is controlled by nuclear DNA.
Sources: en.wikipedia.org
He also said that the government would also target 86 more people and companies connected to President Putin, including people who were "actively undermining the impact of existing sanctions". Sunak said that the new sanctions were made to ensure Russia paid "a price for its illegal activity" and urged other G7 countries to follow suit. The United States also announced that it would tighten export controls to Russia, particularly with regard to militarily important goods, and impose nearly 300 new sanctions against targets linked to Russia. Canada also imposed sanctions on targets linked to the Russian military, relatives of listed persons, members of the Kremlin elite, and those involved in human rights violations. In response to these sanctions, the Russian Foreign Ministry announced a ban on entry into the country on 500 Americans including former President Barack Obama, comedians Stephen Colbert, Jimmy Kimmel and Seth Meyers, Senators JD Vance, Katie Britt and Eric Schmitt, former US Ambassador Jon Huntsman Jr., presumptive Chairman of the Joint Chiefs of Staff General Charles Q. Brown Jr. and several journalists of CNN. Also included were officials involved in the prosecution of participants in the United States Capitol attack in 2021. It also continued to deny US consular access to detained journalist Evan Gershkovich in retaliation for the blocking of entry to Russian journalists during Foreign Minister Sergei Lavrov's visit to the UN in New York in April 2023.
This was elegantly restated in 1963 in a plaque unveiled at Johns Hopkins to commemorate the major contribution (of McLean) to the discovery of heparin in 1916 in collaboration with Professor William Henry Howell. In the 1930s, several researchers were investigating heparin. Erik Jorpes at Karolinska Institutet published his research on the structure of heparin in 1935, which made it possible for the Swedish company Vitrum AB to launch the first heparin product for intravenous use in 1936. Between 1933 and 1936, Connaught Medical Research Laboratories, then a part of the University of Toronto, perfected a technique for producing safe, nontoxic heparin that could be administered to patients, in a saline solution. The first human trials of heparin began in May 1935, and, by 1937, it was clear that Connaught's heparin was safe, easily available, and effective as a blood anticoagulant. Before 1933, heparin was available in small amounts, was extremely expensive and toxic, and, as a consequence, of no medical value. Heparin production experienced a break in the 1990s. Until then, heparin was mainly obtained from cattle tissue, which was a by-product of the meat industry, especially in North America. With the rapid spread of BSE, more and more manufacturers abandoned this source of supply. As a result, global heparin production became increasingly concentrated in China, where the substance was now procured from the expanding industry of breeding and slaughtering hogs.
National legislation for amendment of the Controlled Substances Act to place salvinorin A and Salvia divinorum in Schedule I at the federal level in the United States was proposed in 2002 by Representative Joe Baca (D- California). Those opposed to bill HR 5607 include Daniel Siebert, who sent a letter to Congress arguing against the proposed legislation, and the Center for Cognitive Liberty and Ethics (CCLE), who sent key members of the US Congress a report on Salvia divinorum and its active principle, along with letters from an array of scientists who expressed concern that scheduling Salvia divinorum would negatively impact important research on the plant. The bill did not pass. Although salvia is not regulated under the Controlled Substances Act, as of 2009, it had been made illegal in 13 states. Delaware banned it after salvia use was reported to have played a role in the suicide of a teenager. Alabama, Delaware, Illinois, Louisiana, Michigan, Missouri, Ohio, Texas, and other states have passed their own laws. Several other states have proposed legislation against salvia, including Alaska, California, Florida, Iowa, Maryland, New Jersey, New York, Oregon, and Pennsylvania. Many of these proposals have not made it into law, with motions having failed, stalled or otherwise died, for example at committee review stages. Where individual state legislation does exist, it varies from state to state in its prohibitive degree. Legal consequences may also exist even in states without bans on salvia in particular.
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.
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.