The short version of residual moisture fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-18. Anything still debated is marked as such rather than presented as settled.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
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.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Process removes water by sublimation under vacuum. |
| Typical primary drying shelf temperature | -40 C to -10 C | Set below the formulation's collapse temperature. |
| Typical chamber pressure | 0.05-0.3 mbar | Low pressure allows ice to sublime below its triple point. |
| Water content after drying | 0.5-3% by weight | Higher values may reduce storage stability for some materials. |
| Key thermal parameter | Collapse temperature | Measured by freeze-drying microscopy or differential scanning calorimetry. |
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
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.
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.
== Carbohydrate control in invertebrates == Insects have two types of "blood sugar", the monosaccharide glucose and the disaccharide trehalose. Trehalose is the major carbohydrate used by insects for flight. The concentrations of the carbohydrates trehalose and glucose in the insect hemolymph are tightly controlled by multiple enzymes and hormones, including trehalase, insulin-like peptides (ILPs and DILPs), adipokinetic hormone (AKH), leucokinin (LK), octopamine and other mediators, thereby maintaining carbohydrate homeostasis by endocrine and metabolic feedback mechanisms.
Previous studies have shown that progesterone supports the normal development of neurons in the brain, and that the hormone has a protective effect on damaged brain tissue. Animal models show that females have reduced susceptibility to traumatic brain injury, and this protective effect has been hypothesized to be caused by increased circulating levels of estrogen and progesterone in females.
A PEGylated lipid is used as an excipient in both the Moderna vaccine and the Pfizer–BioNTech COVID-19 vaccine. Both RNA vaccines consist of Messenger RNA, or mRNA, encased in a bubble of oily molecules called lipids. Proprietary lipid technology is used for each. In both vaccines, the bubbles are coated with a stabilizing molecule of polyethylene glycol. As of December 2020, there is some concern that PEG could trigger an allergic reaction, as appears to have occurred by 19 December, in at least three "Alaska health care worker" people who were administered the Pfizer–BioNTech COVID-19 vaccine. The particular PEGylated molecule in the Moderna vaccine is known as DMG-PEG 2000. Pegvaliase (Biomarin) – PEGylated recombinant phenylalanine ammonia-lyase for the treatment of Phenylketonuria, approved by the FDA for the US in May 2018. Adynovate – PEGylated Antihemophilic Factor VIII for the treatment of patients with hemophilia A. (Baxalta, 2015) Irinotecan liposome (Onivyde) – PEGylated liposomal irinotecan hydrochloride trihydrate for the treatment of metastatic pancreatic cancer in adults proceeding treatment with gemcitabine-based therapy. (Ipsen, 2015) Plegridy – PEGylated Interferon Beta-1a for the treatment of patients with relapsing forms of multiple sclerosis. (Biogen, 2014) Naloxegol (Movantik) – PEGylated naloxol for the treatment of opioid-induced constipation in adults patients with chronic non-cancer pain (un-pegylated methadone can cause adverse gastrointestinal reactions).
Sources: en.wikipedia.org
Fish food should ideally provide the fish with fat (for energy) and amino acids (building blocks of proteins) and the fish food (whether flake or pellet) must be speedily digested in order to prevent buildup of intestinal gas, kidney failure and infections (such as swim bladder problems and dropsy) and to avoid aquarium pollution due to excessive ammonia. Aquatic diets for carnivores must contain vegetable matter such as spirulina.
Sir John Christopher Willoughby was second in command and took command of the expedition when the two columns united northwest of Johannesburg on 30 December. Although Jameson's men had cut the telegraph wires to Cape Town, they had failed to cut the telegraph wires to Pretoria (cutting a fence by mistake). Accordingly, news of his incursion quickly reached Pretoria and Jameson's armed column was tracked by Transvaal forces from the moment that it crossed the border. The Jameson armed column first encountered resistance very early on 1 January when there was a very brief exchange of fire with a Boer outpost. Around noon the Jameson armed column was around twenty miles further on, at Krugersdorp, where a small force of Boer soldiers had blocked the road to Johannesburg and dug in and prepared defensive positions. Jameson's force spent some hours exchanging fire with the Boers, losing several men and many horses in the skirmish. Towards evening the Jameson armed column withdrew and turned south-east attempting to flank the Boer force. The Boers tracked the move overnight and on 2 January, as the light improved, a substantial Boer force with some artillery was waiting for Jameson at Doornkop. The tired raiders initially exchanged fire with the Boers, losing around thirty men before Jameson realized the position was hopeless and surrendered to Commandant Piet Cronjé. The raiders were taken to Pretoria and jailed.
primary transcript The unprocessed, single-stranded RNA molecule produced by the transcription of a DNA sequence as it exists before post-transcriptional modifications such as alternative splicing convert it into a mature RNA product such as an mRNA, tRNA, or rRNA. A precursor mRNA or pre-mRNA, for example, is a primary transcript which, after processing, becomes a mature mRNA ready for translation.
Sources: en.wikipedia.org
to improve the resolution of analytes that co-elute with the micellar phase. These agents, however, may alter the level of the EOF. Cyclodextrins are cyclic polysaccharides that form inclusion complexes that can cause competitive hydrophobic partitioning of the analyte. Since analyte-cyclodextrin complexes are neutral, they will migrate toward the cathode at a higher velocity than that of the negatively charged micelles. Mixed micelle systems, such as the one formed by combining SDS with the non-ionic surfactant Brij-35, can also be used to alter the selectivity of MEKC.
Mental health can be seen as a continuum, where an individual's mental health may have many different possible values. Mental wellness is viewed as a positive attribute; this definition of mental health highlights emotional well-being, the capacity to live a full and creative life, and the flexibility to deal with life's inevitable challenges. Some discussions are formulated in terms of contentment or happiness. Many therapeutic systems and self-help books offer methods and philosophies espousing strategies and techniques vaunted as effective for further improving the mental wellness. Positive psychology is increasingly prominent in mental health. A holistic model of mental health generally includes concepts based upon anthropological, educational, psychological, religious, and sociological perspectives. There are also models as theoretical perspectives from personality, social, clinical, health and developmental psychology. The tripartite model of mental well-being views mental well-being as encompassing three components of emotional well-being, social well-being, and psychological well-being. Emotional well-being is defined as having high levels of positive emotions, whereas social and psychological well-being are defined as the presence of psychological and social skills and abilities that contribute to optimal functioning in daily life. The model has received empirical support across cultures. The Mental Health Continuum-Short Form (MHC-SF) is the most widely used scale to measure the tripartite model of mental well-being.
The endoplasmic reticulum (ER) is a transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that float freely in the cytoplasm. The ER has two forms: the rough endoplasmic reticulum (RER), which has ribosomes on its surface that secrete proteins into the ER, and the smooth endoplasmic reticulum (SER), which lacks ribosomes. The smooth ER plays a role in calcium sequestration and release, and helps in synthesis of lipid.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, often under the same vacuum. The two stages differ in the water state being removed.
Freezing determines ice crystal size, pore structure, and the concentration of solutes in remaining liquid. Faster freezing generally creates smaller ice crystals and a denser dried matrix. These features affect drying rate and reconstitution behavior.
Lyophilization reduces water content but usually leaves a small amount of water in the dried material. Some water remains bound to solids or trapped in the dried matrix. Very low water targets can require extended secondary drying, which may alter product stability.
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.