This is a working overview of Cake collapse, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-13 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.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
| 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 |
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 physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
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.
Aspartic, glutamic, and metallo-proteases activate a water molecule, which performs a nucleophilic attack on the peptide bond to hydrolyze it. Serine, threonine, and cysteine proteases use a nucleophilic residue (usually in a catalytic triad). That residue performs a nucleophilic attack to covalently link the protease to the substrate protein, releasing the first half of the product. This covalent acyl-enzyme intermediate is then hydrolyzed by activated water to complete catalysis by releasing the second half of the product and regenerating the free enzyme
In much of the British Empire, slavery was subject to abolition in 1833, throughout the United States it was abolished in 1865 as a result of the Civil War, which was fought after the attempted secession of the South in order to protect its "Peculiar Institution" (i.e. slavery). In Cuba slavery was abolished in 1886. The last country in the Americas to abolish slavery was Brazil, in 1888. Chattel slavery survived longest in the Middle East. After the trans-Atlantic slave trade had been suppressed, the ancient trans-Saharan slave trade, the Indian Ocean slave trade and the Red Sea slave trade continued to traffic slaves from the African continent to the Middle East. During the 20th century, the issue of chattel slavery was addressed and investigated globally by international bodies created by the League of Nations and the United Nations (UN), such as the Temporary Slavery Commission in 1924–1926, the Committee of Experts on Slavery in 1932, and the Advisory Committee of Experts on Slavery in 1934–1939. By the time of the UN Ad Hoc Committee on Slavery in 1950–1951, legal chattel slavery still existed only in the Arabian Peninsula: in Oman, in Qatar, in Saudi Arabia, in the Trucial States and in Yemen. Legal chattel slavery was finally abolished in the Arabian Peninsula in the 1960s: Saudi Arabia and Yemen in 1962, in Dubai in 1963, and Oman as the last in 1970. The last country to abolish slavery, Mauritania, did so in 1981.
"Took up the cooperative movement" at its annual convention in 1919. Moved into its new 4-story building in the West End at the corner of Leverett and Ashland Street and moved in on November 13, 1920. The building contained the group's offices, cooperative grocery, creamery, shoe and dry goods store, and printing plant. The "Co-operative Wholesale Society" consisting of the "Finnish, Lithuanian, and Italian Co-operative of New England" had its offices and warehouse in this building as well. Jewish Progressive Order - Headquartered in Philadelphia. Supported the Palestine Restoration Fund by a "shekel tax" of 25 cents per member. Jewish National Workers Alliance Order of Brith Abraham - Founded in New York in 1859. Originally restricted to Reform Jews. Female lodges, consisting of the female relatives of members of the order, could be formed with the sanction of the Grand Lodge and could elect one of the Past Presidents of the male lodges as their officers. In 1899 there were 11,000 regular members and 1,000 members of the female lodges. 8,000 regular members and three-fifths of the 160 lodges were located in New York City. In 1923 it had 198 lodges, 15,152 benefit members, and 195 social members. It had 8,000 members when it became defunct in 1927. Headquarters in 1923 located at 266-268 Grand Street New York City. The ceremony of the order was calculated to inculcate the values of harmony, wisdom, and justice. The order's emblem was an "interlaced triangle" with a representation of Abraham about to sacrifice Jacob.
=== Effect on Tumour Cells === Cancer-associated fibroblasts negatively influence the outcome of oncological diseases. These cells create a stromal niche for cancer cells and especially cancer stem cells, where they employ both paracrine and direct cell-contact to maintain stemness in cancer stem cells. In turn, this enables these cancer stem cells to escape chemotherapy and radiotherapy, while the cancer-associated fibroblasts also create an environment that allows cancer cells to escape the action anti-tumour immunity. In turn, this promotes the cancer process through tumour growth and also fosters angiogenesis, metastasis and immune evasion. CAF express various cytokines and factors, which activate and contribute to pathways favouring tumorigenesis. They may disrupt normal cell functions, such as cell cycle regulation and cell death, or signal to specific types of cells to mobilize and activate their pro-tumour actions. Furthermore, it has been found that the effect of CAF on neoplastic cells is unique to the type of tumour cells. Cytokine release from CAFs have been linked to breast carcinomas through the metabolism and production of androgen synthesis enzymes. Furthermore, on the topic of the progression of breast cancer, CAFs induces the release growth factors such as FGF and HGF which in turn induces the hyperproliferation of epithelial cells of the breast. EMT and ECM reorganisation are further mechanisms by which the CAFs induce cancer. FSP1, which is secreted by CAFs, promotes tumours through another method - by altering the tumour microenvironment (TME).
Sources: en.wikipedia.org
Garlic cloves are peeled and sliced. In most cases, the garlic is then heated to a temperature of between 150 and 160 °C (302 and 320 °F). The water is removed to a moisture content of about 6.5%. The dehydrated garlic is then further sliced, chopped, or minced until the powder is reduced to the desired particle size. Manufacturing garlic powder on a larger scale involves various steps, from extraction of the garlic bulbs to packaging the final powder. After harvesting the raw garlic, bulbs are cleaned under mild pressure to remove skin and separate the cloves. The garlic is then dehydrated using both historical and newly developed methods. While old methods, such as using natural elements of sun and wind to evaporate water from foodstuffs are still utilized in many parts of the world, new technology has enabled for more flexible and economically viable procedures, such as vacuum and freeze drying. Once the garlic cloves are dried and dehydrated, they are powdered using large scale machines and powdering units. Milling is the process of using mechanical action to break down substances through rotary cutting. As powder processing generally includes additives and is done in a bulk scale, the milling process breaks down materials to the required size for suppliers. Milling may require a series of steps, from de-agglomeration to fine grinding. The four components include delumpers, conical mills, hammermills and fine grinders.
When the precursor cations (proteins or peptides) and radical anions are combined in the ion trap an electron is transferred to the multiply-charged cation. This forms an unstable positive radical cation with one less positive charge and an odd electron. Fragmentation takes place along the peptide backbone at a N− Cα bond, resulting in c- and z-type fragment ions.
1979 Elected member, European Molecular Biology Organization. 1987 Meyenburg Prize for Cancer Research. 1995 Elected member, Academia Europaea. 1997 Doctorate honoris causa, Pomeranian Medical Academy, Szczecin, Poland. 1998 Carl Zeiss Prize, German Society of Cell Biology, (shared with Klaus Weber). 1998 Helena Rubenstein / UNESCO Prize for Women in Science (UK). 2002 L'Oréal / UNESCO Prize for Women in Science. 2003-2006 President of the International Union of Biochemistry and Molecular Biology (IUBMB). 2005 Outstanding Science Alumni Award, Pennsylvania State University, USA. 2014. Federal Cross of Merit, 1st Class, Federal Republic of Germany. 2007 Dorothea Schlözer Medal, University of Göttingen, Germany.
In this series a panel of seven academics, journalists and historians named her among the group of people in the UK "whose actions during the reign of Elizabeth II have had a significant impact on lives in these islands and given the age its character". In 2015 Hodgkin's 1949 paper The X-ray Crystallographic Investigation of the Structure of Penicillin was honoured by a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society presented to the University of Oxford (England). This research is notable for its groundbreaking use of X-ray crystallography to determine the structure of complex natural products, in this instance, of penicillin. Since 1999, the Oxford International Women's Festival has presented the annual Dorothy Hodgkin Memorial Lecture, usually in March, in honour of Hodgkin's work. The Lecture is a collaboration between Oxford AWiSE (Association for Women in Science & Engineering), Somerville College and the Oxford University Museum of Natural History.
=== Eyes === Isotretinoin and other retinoids are well known to affect the eyes. Dry eyes are very common during treatment and is caused by isotretinoin's apoptotic effect on the meibomian glands. Some people develop contact lens intolerance as a result. In some people, these changes are long-lasting or irreversible and represent Meibomian Gland Dysfunction (MGD). Other common effects on the eyes include inflammation of the eyelid (blepharitis), red eye caused by conjunctivitis and irritation of the eye. More rare ocular side effects include blurred vision, decreased night vision (which may be permanent), colour blindness, development of corneal opacities, inflammation of the cornea (keratitis), swelling of the optic disk (papilloedema, associated with IIH), photophobia and other visual disturbances.
Sources: en.wikipedia.org
== Epithelial membrane == The epithelial membrane is composed of epithelium attached to a layer of connective tissue, for example, skin. The mucous membrane is also a composite of connective and epithelial tissues. Sometimes called mucosae, these epithelial membranes line the body cavities and hollow passageways that open to the external environment, and include the digestive, respiratory, excretory, and reproductive tracts. Mucus, produced by the epithelial exocrine glands, covers the epithelial layer. The underlying connective tissue, called the lamina propria (literally “own layer”), help support the fragile epithelial layer. A serous membrane is an epithelial membrane composed of mesodermally derived epithelium called the mesothelium that is supported by connective tissue. These membranes line the coelomic cavities of the body, that is, those cavities that do not open to the outside, and they cover the organs located within those cavities. They are essentially membranous bags, with mesothelium lining the inside and connective tissue on the outside. Serous fluid secreted by the cells of the thin squamous mesothelium lubricates the membrane and reduces abrasion and friction between organs. Serous membranes are identified according locations. Three serous membranes line the thoracic cavity; the two pleura that cover the lungs and the pericardium that covers the heart. A fourth, the peritoneum, is the serous membrane in the abdominal cavity that covers abdominal organs and forms double sheets of mesenteries that suspend many of the digestive organs.
== Pathophysiology == Seigo Minami, a Japanese physician, first reported the crush syndrome in 1923. He studied the pathology of three soldiers who died in World War I due to kidney failure. The renal changes were due to the buildup of excess myoglobin, resulting from the destruction of muscles from lack of oxygen. The progressive acute kidney failure is because of acute tubular necrosis. The syndrome was later described by British physician Eric Bywaters in patients during the 1941 wartime bombing of London (the Blitz). It is a reperfusion injury that appears after the release of the crushing pressure. The mechanism is believed to be the release into the bloodstream of muscle breakdown products—notably myoglobin, potassium and phosphorus—that are the products of rhabdomyolysis (the breakdown of skeletal muscle damaged by ischemic conditions). The specific action on the kidneys is not understood completely, but may be due partly to nephrotoxic metabolites of myoglobin. The most devastating effects upon the body can occur when the crushing pressure is suddenly released, without proper preparation of the patient, causing reperfusion syndrome. In addition to tissue directly suffering the crush mechanism, the tissue is then subjected to sudden reoxygenation in the limbs and extremities. Without proper preparation, the patient, with pain control, may be cheerful before recovery, but then may suddenly die shortly thereafter. This sudden failure is called the "smiling death". These systemic effects are caused by a traumatic rhabdomyolysis.
=== Exercise and fatigue === A low-carbohydrate diet has been found to reduce endurance capacity for intense exercise efforts, and depleted muscle glycogen following such efforts is only slowly replenished if a low-carbohydrate diet is taken. Inadequate carbohydrate intake during athletic training causes metabolic acidosis, which may be responsible for the impaired performance which has been observed.
Neurotrophic factors are those that promote survival and growth of neurons. A trophic factor can be described as a factor that is associated with providing nourishment to allow for growth. In general they are protein ligands for tyrosine kinase receptors; binding to the specific receptor yields autophosphorylation and subsequent phosphorylation of tyrosine residues on proteins that participate in further downstream signaling to activate proteins and genes involved in growth and proliferation. Neurotrophic factors act through retrograde transport in neurons, in which they are taken up by the growth cone of the injured neuron and transported back to the cell body. These neurotrophic factors have both autocrine and paracrine effects, as they promote growth of the damaged neurons as well as the adjacent Schwann cells. Nerve growth factor (NGF) typically has a low level of expression in nerves that are healthy and not growing or developing, but in response to nerve injury NGF expression increases in Schwann cells. This is a mechanism to increase growth and proliferation of Schwann cells at the distal stump in order to prepare for reception of the regenerating axon. NGF has not only a trophic role but also a tropic or guiding role. The Schwann cells that form the bands of Bungner at the distal injury site express NGF receptors as a guiding factor for the regenerating axon of the injured neuron.
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.
Karl Fischer titration is a common reference method that quantifies water by a chemical reaction. Thermogravimetric analysis can also estimate moisture by weight loss on heating. Method choice depends on sample size and whether other volatile substances are present.