The short version of Porous cake fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
Quality control for lyophilized materials includes visual inspection, residual moisture measurement, and reconstitution testing. Cake appearance can reveal process problems such as collapse, shrinkage, or meltback, although appearance alone does not prove potency. Residual moisture is commonly measured by Karl Fischer titration or by loss on drying. Reconstitution time is checked because a slow or incomplete dissolve can indicate a change in pore structure. Stability studies track these attributes over time under defined temperature and humidity conditions.
Analytical methods for lyophilized solids must account for the low moisture content and the fragile cake. Karl Fischer titration is widely used for water content, while near-infrared spectroscopy can measure moisture non-destructively in sealed containers. X-ray diffraction and modulated differential scanning calorimetry help identify crystalline or amorphous phases. Residual solvent analysis may be needed if organic solvents were used during formulation. The combination of these methods supports batch release and long-term stability assessment.
Lyophilized products are typically stored as sealed solids in vials or syringes. Moisture ingress is a major concern because many dried cakes are hygroscopic and can lose stability when exposed to humid air. Storage temperature depends on the formulation; some products are kept refrigerated, while others are stable at room temperature. Container closure integrity and headspace moisture are often monitored. Light protection may also be required for some photosensitive materials.
| 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 |
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.
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.
Quality control for lyophilized products focuses on appearance, moisture level, reconstitution time, and structural integrity. A cake should be uniform, intact, and free of meltback or collapse. Moisture level is measured by Karl Fischer titration or thermogravimetric analysis. Reconstitution time reflects pore structure and formulation. Visual inspection and vial integrity checks detect cracks, stopper defects, or particulate matter. These checks are often performed on samples from each batch. They help confirm that the drying cycle performed as intended.
With the tearing down of the Berlin Wall and with East and West Germany pursuing re-unification, the Iron Curtain between the West and Soviet-occupied regions came down. By 1989, the Soviet alliance system was on the brink of collapse, and, deprived of Soviet military support, the communist leaders of the Warsaw Pact states were losing power. Grassroots organizations, such as Poland's Solidarity movement, rapidly gained ground with strong popular bases.
=== Trafficking === As the number of opioid prescriptions rose, drug cartels began flooding the US with heroin from Mexico. For many opioid users, heroin was cheaper, more potent, and often easier to acquire than prescription medications. According to the CDC, tighter prescription policies by doctors did not necessarily lead to this increased heroin use. The main suppliers of heroin to the US have been Mexican transnational criminal organizations. From 2005 to 2009, Mexican heroin production increased by over 600%, from an estimated 8 metric tons in 2005 to 50 metric tons in 2009. Between 2010 and 2014, the amount seized at the border more than doubled. According to the Drug Enforcement Administration, smugglers and distributors "profit primarily by putting drugs on the street and have become crucial to the Mexican cartels." Illicit fentanyl is commonly made in Mexico and trafficked by cartels. North America's dominant trafficking group is Mexico's Sinaloa Cartel, which has been linked to 80 percent of the fentanyl seized in New York.
=== Notable cases === Napoleon – French general and emperor Arthur Kornberg – Nobel laureate in Physiology or Medicine, 1959 Nicky Wire, Manic Street Preachers – bassist Alexandr Dolgopolov – tennis player Jonas Folger – MotoGP rider
The energy in sunlight is captured by plants, cyanobacteria, purple bacteria, green sulfur bacteria and some protists. This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can, however, operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as a source of energy, while switching between carbon fixation and the fermentation of organic compounds. In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called photosynthetic reaction centres. Reaction centers are classified into two types depending on the nature of photosynthetic pigment present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two. In plants, algae, and cyanobacteria, photosystem II uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the cytochrome b6f complex, which uses their energy to pump protons across the thylakoid membrane in the chloroplast. These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through photosystem I and can then be used to reduce the coenzyme NADP+.
Sources: en.wikipedia.org
=== December === 1 December – A Bangladeshi court convicts MP and former minister Tulip Siddiq of corruption charges and sentences her in her absence to two years in custody. Siddiq describes the sentence as "deeply unfair". Richard Hughes resigns as chair of the Office for Budget Responsibility as an inquiry is launched into how details of the November 2025 United Kingdom budget were published 40 minutes before Chancellor Rachel Reeves delivered the statement to Parliament. Former Conservative MPs Jonathan Gullis, Chris Green and Lia Nici defect to Reform UK. Belfast City Council votes in favour of flying the Palestinian flag above City Hall. 2 December – The High Court rejects an emergency legal application by Traditional Unionist Voice to have the Palestinian flag taken down from Belfast City Hall. 3 December – German President Frank-Walter Steinmeier and his wife Elke Büdenbender are welcomed by King Charles III and Queen Camilla on a state visit to the UK, the first to be made by a German leader for 27 years. Markus Campbell-Savours is suspended from the Parliamentary Labour Party for rebelling against the family farm tax. Reform UK launches an investigation into the online activity of Ian Cooper, the leader of Staffordshire County Council, following allegations he posted racist comments online. 5 December – It is announced that Chancellor Rachel Reeves will not face an investigation by ethics adviser Sir Laurie Magnus over whether or not her pre-budget interventions broke the ministerial code.
Singapore is a major international transport hub in Asia, serving some of the busiest sea and air trade routes. Changi Airport is an aviation centre for Southeast Asia and a stopover on Qantas' Kangaroo Route between Sydney and London. There are two civilian airports in Singapore, Changi Airport and Seletar Airport. Changi Airport hosts a network of over 100 airlines connecting Singapore to some 300 cities in about 70 countries and territories worldwide. It has been rated one of the best international airports by international travel magazines, including being rated as the world's best airport for the first time in 2006 by Skytrax. It also had three of the ten busiest international air routes in the world in 2023: the busiest between Kuala Lumpur–Singapore, the seventh busiest between Jakarta–Singapore, and the ninth busiest between Bangkok–Singapore. Singapore Airlines, the flag carrier of Singapore, has been regarded as a 5-star airline by Skytrax and been in the world top 10 list of airlines for multiple consecutive years. It held the title of the World's Best Airline by Skytrax in 2023. It won this title 12 times. Its hub, Changi Airport had also been rated as the world's best airport from 2013 to 2020 before being superseded by Hamad International Airport in Doha. It reclaimed this title in 2023 before being superseded once more in 2024.
No visible clubbing – Fluctuation (increased ballotability) and softening of the nail bed only. No visible changes in nails. Mild clubbing – Loss of the normal <165° angle (Lovibond angle) between the nailbed and the fold (cuticula). Schamroth's window (see image) is obliterated. Clubbing is not obvious at a glance. Moderate clubbing – Increased convexity of the nail fold. Clubbing is apparent at a glance. Gross clubbing – Thickening of the whole distal (end part of the) finger (resembling a drumstick) Hypertrophic osteoarthropathy – Shiny aspect and striation of the nail and skin Schamroth's sign or Schamroth's window test (originally demonstrated by South African cardiologist Leo Schamroth on himself) is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly opposed (place fingernails of the same finger on opposite hands against each other, nail to nail), a small diamond-shaped "window" is normally apparent between the nailbeds. If this window is obliterated, the test is positive, and clubbing is present.
== Pharmacokinetics == The pharmacokinetics of synephrine were studied by Hengstmann and Aulepp, who reported a peak plasma concentration at 1–2 hours, with an elimination half-life (T1/2) of ~ 2 hours.
== Reference pattern == This reference pattern is based on the essential amino acid requirements for preschool children aged 1–3 years as published in Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005). Adults aged 18+ will have slightly lower requirements.
Sources: en.wikipedia.org
The sexism was evident in many ways, according to Mamphela Ramphele, a BCM activist and doctor at the Zanempilo Clinic, including that women tended to be given responsibility for the cleaning and catering at functions. "There was no way you could think of Steve making a cup of tea or whatever for himself", another activist said. Feminism was viewed as irrelevant "bra-burning". Surrounded by women who cared about him, Biko developed a reputation as a womaniser, something that Woods described as "well earned". He displayed no racial prejudice, sleeping with both black and white women. At NUSAS, he and his friends competed to see who could have sex with the most female delegates. Responding to this behaviour, the NUSAS general secretary Sheila Lapinsky accused Biko of sexism, to which he responded: "Don't worry about my sexism. What about your white racist friends in NUSAS?" Sobukwe also admonished Biko for his womanising, believing that it set a bad example to other activists. Biko married Ntsiki Mashalaba in December 1970. They had two children together: Nkosinathi, born in 1971, and Samora, born in 1975. Biko's wife chose the name Nkosinathi ("The Lord is with us"), and Biko named their second child after the Mozambican revolutionary leader Samora Machel. Angered by her husband's serial adultery, Mashalaba ultimately moved out of their home, and by the time of his death, she had begun divorce proceedings. Biko had also begun an extra-marital relationship with Mamphela Ramphele. In 1974, they had a daughter, Lerato, who died after two months.
== Use and effects == The 2C drugs are orally active at doses of 6 to 150 mg, depending on the drug, and have durations of 3 to 48 hours, also depending on the drug. Several have doses in the range of 10 to 60 mg and durations in the range of 4 to 12 hours. The 2C drugs produce psychedelic effects, such as perceptual enhancement, psychedelic visuals, and euphoria. Some, such as 2C-B, have also been reported to produce some entactogen-like effects, but findings in this area appear to be mixed.
Headquarters Großdeutschland Reconnaissance Battalion Großdeutschland Panzer Regiment Großdeutschland Grenadier Regiment Großdeutschland Fusilier Regiment Großdeutschland Engineer Battalion Großdeutschland Artillery Regiment Großdeutschland Tank Destroyer Battalion Großdeutschland Army Anti-Aircraft Battalion Großdeutschland Assault Gun Battalion Großdeutschland Signal Battalion Großdeutschland Divisional Supply Group
In May 1944, the Prime Minister, John Curtin, and the Commander-in-Chief of the Australian Army, General Sir Thomas Blamey, visited London for the 1944 Commonwealth Prime Ministers' Conference. At Blamey's request, Curtin asked Florey if he would visit Australia as an advisor on the use of penicillin. Florey arrived in Australia in August 1944 to a hero's welcome, and he was awarded the degree of Doctor of Medicine (MD) by the University of Adelaide. In accepting the degree, he recapitulated his own career, and spoke about the need to make it easier for research to be conducted in Australia. Florey met with Blamey; the two men got along well and chatted for several hours. It ended with Blamey convinced that Florey was the man to head a project Blamey had in mind: a medical research institute in Canberra, the national capital. Blamey put his proposal to Curtin on 24 October. It was quickly approved, but Curtin became ill, and he died in July 1945. Florey discovered that penicillin production was already underway in Australia at the Commonwealth Serum Laboratories (CSL) in Melbourne. In 1943, the War Cabinet had agreed to produce penicillin in Australia, and Colonel E. V. (Bill) Keogh, the Army's Director of Hygiene and Pathology, detailed Captain Percival Bazeley and Lieutenant H. H. Kretchmar to establish a production facility. They visited Peoria, and obtained penicillin cultures from Coghill. The first Australian-made penicillin began reaching the troops in New Guinea in December 1943.
In the US, Aducanumab is indicated for the treatment of Alzheimer's disease. In July 2021, the US Food and Drug Administration (FDA) limited the indication to people with mild cognitive impairment or mild dementia stage of disease, the population in which treatment was initiated in clinical trials. Aducanumab is a monoclonal IgG1 antibody that binds to the amyloid beta protein at amino acids 3–7, which is posited to result in slowing the progression of Alzheimer's disease. The mechanism is based on the amyloid hypothesis, which posits that amyloid proteins cause Alzheimer's disease, hence removing amyloid should slow the progression of the disease. How the antibody accesses the plaques is under active research. One mechanism suggests the plaques are exposed to the lumen of blood vessels and the antibody accesses the plaques from the lumen side. This assumes the plaque formed as a result of a leaky blood brain barrier and may also explain why there is hemorrhage after the plaques are removed. The most common serious adverse reactions reported are:
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.
Most lyophilized products are stored in sealed containers at controlled temperature and humidity. Some require refrigeration, while others are stable at room temperature. Protection from light and moisture is often necessary.