A practical reference on primary drying: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-09-14 and is reviewed periodically as new material appears.
Lyophilization is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid that can be reconstituted later.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
Storage conditions depend on the formulation and the intended shelf life. Many pharmaceutical and biological freeze-dried products are kept at 2–8 °C, while some stable foods and reagents tolerate room temperature. Others require −20 °C or colder to slow chemical degradation or aggregation. Protection from light and oxygen is common because oxidation can continue in the dry state. Stability studies usually monitor potency, appearance, moisture, and reconstitution time over months or years. Predictions from accelerated studies are useful but may not fully capture real-time changes.
Quality control for freeze-dried lots combines visual inspection with instrumental tests. Cake appearance, color, and shrinkage are recorded against a reference, while residual moisture is measured by Karl Fischer titration or loss on drying. Thermal analysis can reveal phase transitions and crystallization events, and X-ray diffraction distinguishes amorphous from crystalline solids. Microbiological tests and container closure integrity checks are also routine for sterile products. Analytical methods must be validated for the matrix, because excipients and low moisture can affect accuracy. Open questions include how best to predict long-term stability from short-term data.
| Property | Value | Notes |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
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.
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.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
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.
The discovery of element 102 was a complicated process and was claimed by groups from Sweden, the United Kingdom, the United States, and the Soviet Union. The first complete and incontrovertible report of its detection only came in 1966 from the Joint Institute of Nuclear Research at Dubna (then in the Soviet Union). The first announcement of the discovery of element 102 was announced by physicists from Argonne National Laboratory, Harwell Atomic Energy Research Establishment, and Nobel Institute for Physics in Sweden in 1957. The team reported that they had bombarded a curium target with carbon-13 ions in half-hour intervals for fifty times. Between bombardments, ion-exchange chemistry was performed on the target. Twelve out of the fifty bombardments contained samples emitting (8.5 ± 0.1) MeV alpha particles, which were in drops which eluted earlier than fermium (atomic number Z = 100) and californium (Z = 98). The half-life reported was 10 minutes and was assigned to either 251No or 253No, although the possibility that the alpha particles observed were from a presumably short-lived mendelevium (Z = 101) isotope created from the electron capture of element 102 was not excluded. The team proposed the name nobelium (No) for the new element, which was immediately approved by IUPAC, a decision which the Dubna group characterized in 1968 as being hasty. In 1958, scientists at the Lawrence Berkeley National Laboratory repeated the experiment. The Berkeley team, consisting of Albert Ghiorso, Glenn T. Seaborg, John R.
C5H12 + Cl2 → C5H11Cl + HCl Without zeolite catalysts, such reactions are unselective, so with n-pentane, the result is a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical halogenations can also occur.
The Republic of South Africa was established in 1961. The only change made to the composition of the Parliament was the substitution of the State President for the Queen. A few significant changes were made later:
However this claim has been challenged by another report that the human musk-recognizing receptor, OR5AN1 that robustly responds to cyclopentadecanone and muscone, fails to distinguish isotopomers of these compounds in vitro. Furthermore, the mouse (methylthio)methanethiol-recognizing receptor, MOR244-3, as well as other selected human and mouse olfactory receptors, responded similarly to normal, deuterated, and carbon-13 isotopomers of their respective ligands, paralleling results found with the musk receptor OR5AN1. Hence it was concluded that the proposed vibration theory does not apply to the human musk receptor OR5AN1, mouse thiol receptor MOR244-3, or other olfactory receptors examined. In addition, the proposed electron transfer mechanism of the vibrational frequencies of odorants could be easily suppressed by quantum effects of nonodorant molecular vibrational modes. Hence multiple lines of evidence argue against the vibration theory of smell. This later study was criticized since it used "cells in a dish rather than within whole organisms" and that "expressing an olfactory receptor in human embryonic kidney cells doesn't adequately reconstitute the complex nature of olfaction...". In response, the authors of the second study state "Embryonic kidney cells are not identical to the cells in the nose .. but if you are looking at receptors, it's the best system in the world."
Sources: en.wikipedia.org
Mahathir also strengthened political and economic cooperation with China, whilst maintaining diplomatic ambivalence on security issues to avoid escalating territorial disputes in the South China Sea. He openly criticised China's involvement in Malaysia's communist insurgency, but downplayed any military threat from China after the Cold War ended. In 1985, Mahathir visited China for the first time as prime minister, where he met Chinese leader Deng Xiaoping, establishing a new level of trust that laid the foundation for Malaysia-China relations and set the stage for decades of economic and diplomatic growth. Later, he visited China again in 1993, 1994, 1996, 1999, and twice in 2001. In the early 1990s, Mahathir played a key role in engaging China with ASEAN despite South China Sea disputes, particularly in the post-Tiananmen and post-Cold War contexts, paving the way for then Chinese Foreign Minister Qian Qichen to attend the ASEAN meeting's opening ceremony in July 1991 as a guest of the Malaysian government, and eventually leading to China's upgrade to ASEAN's dialogue partner in 1996. Amidst the Asian financial crisis, Mahathir also led several large delegations to China and Russia to seek regional economic cooperation. Besides that, Mahathir also had significant interactions with Taiwan, especially during the 1980s and 1990s, when economic ties between the two sides were at their strongest despite the lack of formal diplomatic relations.
=== Structure === Honokiol belongs to a class of neolignan biphenols. As a polyphenol it is relatively small and can interact with cell membrane proteins through intermolecular interactions like hydrogen bonding, hydrophobic interactions, or aromatic pi orbital co-valency. It is hydrophobic and readily dissolved in lipids. It is structurally similar to propofol.
Valve closed the office in August 2013 when it decided it had little benefit. At the 2013 D.I.C.E. Summit, Newell announced that he and the film director J. J. Abrams were collaborating to produce a Half-Life or Portal film, as well as a possible game. In the 2010s, Valve released fewer games and invested in hardware development. Newell intended to make Valve more like Nintendo, which develops games in tandem with hardware, allowing it to create innovative games such as Super Mario 64. Valve initially focused on augmented reality, but in 2013 Newell laid off many staff to focus on virtual reality (VR). Valve began porting its games to Linux in 2013, including Half-Life 2 and Left 4 Dead 2. In 2015, Valve released the Steam Machine, a line of gaming computers, which sold poorly. Media commentators speculated that Valve's transition to service provider with Steam, which generated an estimated $3.4 billion in 2017, had driven it away from game development. Valve canceled games including numerous Half-Life projects (including Episode Three), Left 4 Dead 3, a Soulslike game, and a voxel-based game, A.R.T.I. Additional VR projects included SimTrek, developed by members of the Kerbal Space Program development team, and a new VR device, Vader, that was determined to be too costly for consumers. According to the designer Robin Walker, the abundance of projects that failed to gain traction, with no shared vision, damaged morale. Many players grew frustrated in anticipation of a new Half-Life game.
AC/DC, an Australian rock music group ACDC (medicine), Arterial calcification due to deficiency of CD73 (ACDC), a rare genetic disorder Adiponectin, a peptide hormone All Campus Dining Center, a dining hall at Vassar College Asian Community Development Corporation, a community development organization headquartered in Boston ACDC (JoJo's Bizarre Adventure), also Esidisi, a character from the Japanese manga and anime JoJo's Bizarre Adventure in the story arc Battle Tendency ACDC, a dance crew led by Adam G. Sevani and Jon M. Chu Africa CDC, Africa Centres for Disease Control and Prevention Asymmetric counteranion directed catalysis, a type of chemical reaction
== Epidemiology == Fever is one of the most common medical signs. It is part of about 30% of healthcare visits by children, and occurs in up to 75% of adults who are seriously sick. About 5% of people who go to an emergency room have a fever.
Sources: en.wikipedia.org
=== Web browsing === Web browsers with integrated AI agents are sometimes called agentic browsers. Such agents can perform tasks and browser actions on the user's behalf. In 2025, Microsoft launched NLWeb, an agentic web search replacement that would allow websites to use agents to query content from websites by using RSS-like interfaces that allow for the lookup and semantic retrieval of content. Within weeks of release, NLWeb was found to have created security issues and expose information about users to third-party servers.
=== Supporting === Xu Di as Xue Zhenzhu (薛珍珠), Luo Zijun and Luo Ziqun's mother. Zhang Lingxin as Luo Ziqun (罗子群), Luo Zijun's younger sister. Zheng Luoqian as Wei Wei'an (薇薇安) Wang Tianze as Leng Jiaqing (冷佳清), Ling Ling's son and Chen Junsheng's stepson. Vivian Wu as Aunt Wu Luan Yuanhui as Bai Guang Chuo Ni as Luoluo Mei Ting as Zhuo Jianqing's former girlfriend Tan Kai as Adom Kong Wei as a single woman Zhang Yanyan as Su Manshu Hou Yansong as Laojin Wei Zhihao as Ping'er Song Yunhao as Duan Xiaotian Xu Caigen as Cui Baojian Ren Jimin as Chen Junsheng's father Zhang Lan as Chen Junsheng's mother Ru Tian as Ya Qin Min Tianhao as A Hui Shi An as Lawyer Li Guo Tongtong as Xiaodong Chen Guanning as Cui Baojian's son Yang Mei as a chubby girl. Sun Yuhan as Caicai Xu Sheng as Phil Guan Xueying as Sandra Dong Bi Hanwen as the lawyer of Chen Junsheng Qu Lingzi as He Han's assistant Lu Ling as Yingying Cheng Hong as the marketing manager Huang Jing as Tang Jing's assistant Yu Mingjia as the CEO of Angel Ren Donglin as Li Rui Zhang Yi as Luo Ping
In the anterior pituitary, the term "acidophil" is used to describe two different types of cells which stain well with acidic dyes. Somatotrophs, which secrete growth hormone (a peptide hormone) Lactotrophs, which secrete prolactin (a peptide hormone) When using standard staining techniques, they cannot be distinguished from each other (though they can be distinguished from basophils and chromophobes), and are therefore identified simply as "acidophils". Eosinophilic Acidophile (histology) Basophilic Chromophobe cell Melanotroph Chromophil Basophil cell Oxyphil cell Oxyphil cell (parathyroid) Pituitary gland Neuroendocrine cell
In September 2020, the US Food and Drug Administration (FDA) required the boxed warning for all benzodiazepine medicines to be updated to describe the risks of abuse, misuse, addiction, physical dependence, and withdrawal reactions consistently across all the medicines in the class.
Sources: en.wikipedia.org
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
Karl Fischer titration is widely used because it is specific for water and works at low levels. Loss on drying is simpler but less specific, since volatile solvents or decomposition products can also be lost.