glass transition 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.
Last reviewed on 2025-08-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Residual moisture is a key quality attribute for lyophilized products. Water that remains after secondary drying can affect chemical stability, cake structure, and shelf life. Karl Fischer titration is a common method for measuring water content in the dried solid. The target range varies by product, but many biologics are dried to between 0.5% and 3% water by weight. Acceptable limits are set during development and confirmed by stability studies.
Stability studies examine how temperature, humidity, and time influence a lyophilized product. Accelerated conditions provide early information about degradation pathways, while long-term studies support shelf-life claims. The glass transition temperature of the dried formulation can indicate its physical stability, and storage above this temperature may increase molecular mobility and lead to collapse or aggregation. Container closure integrity also matters because moisture or oxygen ingress can degrade the product, so vial stoppers and seals are part of the quality system.
| 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.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
Quality control for lyophilized products includes appearance, cake structure, reconstitution time, pH, residual moisture, and potency. Residual moisture is a key attribute because excess water can reduce stability, while excessively low moisture may cause structural changes or aggregation in some systems. Stability studies compare real-time and accelerated conditions to estimate shelf life. Analytical methods must be validated for the specific matrix, container, and moisture range. Sterility and container integrity are also monitored for sterile products.
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.
great-granddaughter of Joseph Hertz (Chief Rabbi of the British Empire) Chaim Herzog(Hebrew: חיים הרצוג; 17 September 1918 – 17 April 1997) Northern-Irish-born Israeli politician, general, lawyer and author of over five books on the Arab-Israeli conflict, who served as the sixth President of Israel; born in Belfast, raised in Dublin, the son of Ireland's Chief Rabbi Yitzhak HaLevi Herzog, he immigrated to Mandatory Palestine in 1935 and served in Haganah Jewish paramilitary group during the 1936–1939 Arab revolt; returned to Palestine after the war and, following the end of the British Mandate and Israel's Declaration of Independence in 1948, fought in the Battles of Latrun during the 1948 Arab–Israeli War; retired from Israel Defence Forces in 1962 with rank of major-general.His son Isaac Herzog is the incumbent President of Israel, the first father–son pair to serve as the nation's president, and led the Israeli Labor Party and the parliamentary Opposition in the Knesset between 2013 and 2017.
2015: Edgar Savisaar, Estonian politician, had his right leg amputated. He got the disease during a trip to Thailand. 2018: Alex Smith, an American football quarterback for the Washington Football Team of the National Football League (NFL), contracted the disease after being injured during a game. He suffered an open compound fracture in his lower leg, which became infected. Smith narrowly avoided amputation and eventually returned to playing professional football in October 2020. Smith's injury and recovery is the subject of the ESPN documentary E60 Presents: Project 11. 2019: OG Maco contracted NF after an untreated rash. 2021: Irish actor Barry Keoghan revealed in 2024 that he contracted NF shortly before filming The Banshees of Inisherin and nearly had his arm amputated.
The aphid that was the central source of the damage in France was first noted following the growing of the European vine Vitis vinifera by French colonists in Florida, in the 16th century. These plantations were a failure, and later experiments with related species of vine also failed, although the reason for these failures appears to have been a mystery to the French colonists. It is known today that it was a species of North American grape phylloxera that caused these early vineyards to fail; the venom injected by the Phylloxera causes a disease that is quickly fatal to the European varieties of vine. The aphids initially went unnoticed by the colonists, despite their great numbers, and the pressure to successfully start a vineyard in America at the time. It became common knowledge among the settlers that their European vines, of the vinifera variety, simply would not grow in American soil, and they resorted to growing native American plants, and established plantations of these native vines. Exceptions did exist; vinifera plantations were well-established in California before the aphids found their way there.
Sources: en.wikipedia.org
A suitable site is to be sought throughout Germany and identified by 2031. In principle, crystalline (granite), salt or clay rock types can be considered for a repository. There will be no "ideal" site. The "best possible" site will be sought. Mining areas and regions where volcanoes have been active or where there is a risk of earthquakes are excluded. Internationally, experts are advocating storage in rock formations several hundred meters below the earth's surface. This involves building a repository mine and storing the waste there. It is then permanently sealed. Geological and technical barriers surrounding the waste are designed to keep it safe for thousands of years. For example, 300 meters of rock will separate the repository from the earth's surface. It will be surrounded by a 100-meter-thick layer of granite, salt or clay. The first waste is not expected to be stored until 2050. The Federal Office for the Safety of Nuclear Waste Management (BfE) took up its activities on September 1, 2004. Its remit includes tasks relating to nuclear safety, the safety of nuclear waste management, the site selection procedure including research activities in these areas and, later on, further tasks in the area of licensing and supervision of repositories. In the USA, Yucca Mountain was initially selected as the final storage site, but this project was temporarily halted in February 2009. Yucca Mountain was the starting point for an investigation into atomic semiotics.
=== Supervoltage cancer therapy === Working from an auto garage near Harvard Square, HVEC began building Trump's gas-insulated Van de Graaff generators for hospitals and manufacturers. In 1947, the first orders came from several British hospitals for HVEC's compact 2-megavolt machines. The company was among the first to make artificial radiation sources commercially available for cancer treatment. After three years, HVEC had delivered 17 particle accelerators, employed 140 people, and negotiated $2 million in sales (equivalent to $27.1 million in 2025), eclipsing its competitors' products and undercutting them on price. Nevertheless, the company faced severe financial difficulties in its early years. On several occasions, technical problems brought HVEC to within days of exhausting both money and credit. By the mid-1950s, successor technologies like cobalt-60 machines built by General Electric began dominating hospital orders, offering simpler operation and lower maintenance costs. Although HVEC remained in the medical market until 1969, the company increasingly focused on redesigning its generators for research and industrial applications.
== Performance measures == The South African logistics sector ranks highly on a global scale, and rankings are continuing to increase. According to indices from the World Bank, as of 2026, SA's logistics infrastructure and performance are comparable to those of China and the United States. South Africa ranked joint 19th place, out of 139 countries in the 2023 World Bank Logistics Performance Index - an increase of 14 places year-over-year. There are various measures of performance for South African logistics, with a mix of indices, ranks, and other metrics from the a national and node-specific perspective. According to the Council for Scientific and Industrial Research, some of these are:
Sources: en.wikipedia.org
==== Funeral ceremonies ==== According to Margaret Holloway, funerals are believed to be driven by the consumer's choice, personalisation, secularization, and stories that place individual traditional meta-narratives. It has been studied that funeral homes in the UK are most concerned with comforting the grieving, rather than focusing on the departed. This study found that modern day funerals focus on the psycho-social-spiritual event. Modern day funerals also help the transition of the recently passed transitioning to the social status of 'the deceased'. The article found that funeral homes do not adhere to traditional religious beliefs, but do follow religious traditions.
The Aleutian Islands ( ə-LOO-shən or ə-LEW-shən), also called the Aleut Islands, or Aleutic Islands, are a chain of 14 main, larger volcanic islands and 55 smaller ones. Most of the islands belong to the U.S. state of Alaska, with the archipelago encompassing the Aleutians West Census Area and the Aleutians East Borough. The Commander Islands, located farther to the west, belong to the Russian federal subject of Kamchatka Krai, of the Russian Far East. The islands form part of the Aleutian Arc of the Northern Pacific Ocean, and occupy a land area of 6,821 sq mi (17,666 km2) that extends westward roughly 1,200 mi (1,900 km) from the Alaska Peninsula mainland, in the direction of the Kamchatka Peninsula; the archipelago acts as a border between the Bering Sea to the north and the Pacific Ocean to the south. Crossing longitude 180°, at which point east and west longitude end, the archipelago contains both the westernmost and easternmost parts of the United States, by longitude (Amatignak Island and Semisopochnoi Island, respectively). The westernmost U.S. island, in real terms, however, is Attu Island, west of which runs the International Date Line. The islands, with their 57 volcanoes, form the northernmost part of the Pacific Ring of Fire. Physiographically, they are a distinct section of the larger Pacific Border province, which, in turn, is part of the larger Pacific Mountain System physiographic division. The islands are considered to be among the most geographically isolated areas of the Northern Pacific.
== Structure == PGLYRP2 has one canonical carboxy-terminal catalytic peptidoglycan-binding type 2 amidase domain (also known as a PGRP domain) with predicted peptidoglycan-binding and catalytic cleft with walls formed by α-helices and the floor by a β-sheet. PGLYRP2 also has a long N-terminal segment that comprises two thirds of the PGLYRP2 sequence, has two hydrophobic regions, is unique and not found in other mammalian PGLYRP1, PGLYRP3, and PGLYRP4 and in invertebrate PGRPs, and contains intrinsically disordered region with hepatitis B virus (HBV) DNA-binding domain. The C-terminal segment is also longer than in other mammalian PGLYRPs. PGLYRP2 has two pairs of cysteines in the PGRP domain that are conserved in all human PGRPs and are predicted to form two disulfide bonds. Human PGLYRP2 is glycosylated and secreted, and forms non-disulfide-linked homodimers. PGLYRP2, similar to all other amidase-active PGRPs (invertebrate and vertebrate), has a conserved Zn2+-binding site in the peptidoglycan-binding cleft, which is also present in bacteriophage type 2 amidases and consists of two histidines, one tyrosine, and one cysteine (His411, Tyr447, His522, Cys530 in human PGLYRP2).
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.
Residual moisture can influence chemical degradation, cake collapse, and long-term stability. Low moisture levels usually improve stability, but each product has an optimal range.