The short version of Primary drying fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-12-19 and is reviewed periodically as new material appears.
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.
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.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
| 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 |
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.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
Quality assessment of a lyophilized product includes cake appearance, residual moisture, reconstitution time, and container closure integrity. A uniform, porous cake suggests that freezing and drying stayed within the formulation's design space. Cracks, shrinkage, meltback, or a glassy film can indicate thermal abuse or a formulation problem. Analysts also test for subvisible particles and sterility when the product requires those specifications. Visual inspection alone cannot confirm biological activity or chemical stability, so it is combined with analytical methods.
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.
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.
== Return to Mexico == On September 25, 1945, a few weeks after the war ended, members of the FAEM unveiled a monument to their fallen comrades. The monument was designed by pilot Miguel Moreno Arreola and was built with the help of 10 elements of the Squadron. The eagle that tops the monument was made by the sculptor of Filipino origin Guillermo Tolentino. On October 12, the Squadron handed over its aircraft to the 45th Air Services Group and began preparations to return to Mexico. The members of the FAEM boarded the Sea Marlin ship on October 23, arriving on November 13 in San Pedro, California, although the first to arrive in Americas were Colonel Cárdenas Rodríguez, Lieutenant Amadeo Castro Almanza, Second Lieutenant García Ramos and Second Lieutenant José Luis Pratt Ramos, who traveled by air after meeting with General MacArthur in Tokyo, to thank him for his cooperation with the FAEM. 201st Squadron returned to Mexico City on November 18 in a military parade in the Zócalo and the subsequent presentation of the flag to the president, General Manuel Ávila Camacho, being received as heroes for battling fascism in the Pacific. The FAEM was disbanded upon his return from the Philippines. However, the rest of the Mexicans who fought in other armies were not given recognition as they did with the Squadron. In the years following the war, many of the members have successfully moved on to other careers in life, some as leaders of civil aviation or the Mexican Army, others as businessmen, educators and engineers; five of the pilots became generals of the Mexican Air Force.
==== Types of 3D printing used in manufacturing vascularized organs ==== Extrusion Extrusion based printing is a type of printing in which material is pushed through a nozzle and extruded onto a surface or medium. While material is being extruded, either the nozzle or the print bed is moved so that the material can be placed in complex shapes across it medium. Layers upon layers of material are placed until a 3D structure is formed. The extruded material comes out as a liquid and is solidified through varies means depending on the chemical or physical properties of the material. For example, the material could be solidified through the use of photoreceptive polymerization, in which light activates the material to solidify. The material could also be hardened through the use of chemicals or enzymes. Some examples of bioinks used in extrusion based printing include some alginates, hyaluronic acid, and gellan gum.
Summit Acquisitions, LLC, a group made up of three of the company's franchisees, has assumed a strategic advisory role on behalf of the company's bondholders. Twin Peaks is no longer associated with FAT Brands and has returned to its previous status as a privately-held company. As of June 2026, the company has 115 locations, having recently opened a new lodge in Omaha, NE, with another set to open in Kissimmee, FL in late June. They also have secured signed development agreements with operators to bring Twin Peaks to Connecticut (via New London Hospitality) and another agreement that will see several new lodges in South Texas, including Brownsville, South Padre Island, and Laredo, TX.
=== Host restriction and safety for domestic animals === Currently, there is no scientific data obtained using modern detection methods that would identify SeV as an infectious - disease causing agent for humans or domestic animals. Modern methods for the identification of pathogenic microorganisms have never detected SeV in pigs or other domestic animals, despite the isolation of other paramyxoviruses. Consequently, it is recognized that Sendai virus disease causing infection is host restrictive for rodents and the virus does not cause disease in humans or domestic animals, which are natural hosts for their own parainfluenza viruses. After experimental SeV infection the virus can replicate and shed from the upper and lower respiratory tract of African green monkeys and chimpanzees, but it is not causing any disease. Sendai virus has been used and demonstrated high safety profile in clinical trials involving both adults and children to immunize against human parainfluenza virus type 1, since the two viruses share common antigenic determinants and trigger the generation of cross-reactive neutralizing antibodies. The study that was published in 2011 demonstrated that SeV neutralizing antibodies (which were formed due to human parainfluenza virus type 1 past infection) can be detected in 92.5% of human subjects worldwide with a median EC50 titer of 60.6 and values ranging from 5.9 to 11,324. Low anti-SeV antibodies background does not block the ability of SeV-base vaccine to promote antigen-specific T cell immunity.
The BacT/ALERT system, which indirectly detects production of CO2 by measuring the decrease in the medium's pH, was approved for use in the US in 1991. Unlike the BACTEC systems available at the time, the BacT/ALERT did not require a needle to be introduced into the bottle for sampling; this reduced the frequency of contamination and made it the first system to provide truly continuous monitoring of blood cultures. This non-invasive measurement method was adopted in 1992 by the BACTEC 9000 series, which used fluorescent indicators to detect pH changes. The Difco ESP, a direct predecessor of the contemporary VersaTREK system which detects gas production by measuring pressure changes, was also first approved in 1992. By 1996, an international study found that 55% of 466 laboratories surveyed were using the BACTEC or BacT/ALERT systems, with other automated systems accounting for 10% of the total.
Sources: en.wikipedia.org
The main drawback to using MALBAC is that it has reduced accuracy compared to DOP-PCR and MDA due to the enzyme used to copy the DNA. Once amplified using any of the above techniques, the DNA can be sequenced using Sanger sequencing or next-generation sequencing (NGS).
Most refrigerator-freezers—except for manual defrost models or cheaper units—use what appears to be two thermostats. Only the refrigerator compartment is properly temperature controlled. When the refrigerator gets too warm, the thermostat starts the cooling process and a fan circulates the air around the freezer. During this time, the refrigerator also gets colder. The freezer control knob only controls the amount of air that flows into the refrigerator via a damper system. Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction. Changing the freezer temperature will have no effect on the refrigerator temperature. The freezer control may also be adjusted to compensate for any refrigerator adjustment. This means the refrigerator may become too warm. However, because only enough air is diverted to the refrigerator compartment, the freezer usually re-acquires the set temperature quickly, unless the door is opened. When a door is opened, either in the refrigerator or the freezer, the fan in some units stops immediately to prevent excessive frost build up on the freezer's evaporator coil, because this coil is cooling two areas. When the freezer reaches temperature, the unit cycles off, no matter what the refrigerator temperature is. Modern computerized refrigerators do not use the damper system. The computer manages fan speed for both compartments, although air is still blown from the freezer.
To overcome the dust issues and poor flowability of the powder, a new generation of spray dryers called multiple effect spray dryers have been developed. Instead of drying the liquid in one stage, drying is done through two steps: the first at the top (as per single effect) and the second with an integrated static bed at the bottom of the chamber. The bed provides a humid environment which causes smaller particles to clump, producing more uniform particle sizes, usually within the range of 100 to 300 μm. These powders are free-flowing due to the larger particle size. The fine powders generated by the first stage drying can be recycled in continuous flow either at the top of the chamber (around the sprayed liquid) or at the bottom, inside the integrated fluidized bed. The drying of the powder can be finalized on an external vibrating fluidized bed. The hot drying gas can be passed in as a co-current, same direction as sprayed liquid atomizer, or counter-current, where the hot air flows against the flow from the atomizer. With co-current flow, particles spend less time in the system and the particle separator (typically a cyclone device). With counter-current flow, particles spend more time in the system and is usually paired with a fluidized bed system. Co-current flow generally allows the system to operate more efficiently. Alternatives to spray dryers are:
There is no doubt that a little sunlight is good for you! But 5–15 minutes of casual sun exposure of hands, face and arms two to three times a week during the summer months is sufficient to keep your vitamin D levels high. Vitamin D can also be obtained from food and supplementation. Excess sun exposure produces harmful effects, however.
Sources: en.wikipedia.org
ArH + CH2O → ArCH2OH When conducted in the presence of hydrogen chloride, the product is the chloromethyl compound, as described in the Blanc chloromethylation. If the arene is electron-rich, as in phenols, elaborate condensations ensue. With 4-substituted phenols one obtains calixarenes. Phenol results in polymers.
She eventually succeeded in purifying components of the coat that were not clathrin and are now known as adaptor proteins. These proteins sit between clathrin, which forms the vesicle's outer shell and also the vesicle membrane. Continuing, Margaret discovered that there were two different populations of clathrin-coated vesicles, one that uses AP-2 at the plasma membrane and one that uses AP-1 and was associated with intracellular membranes. AP-1 and AP-2 are both heterotetramers with related subunits. They both have two large subunits and the other subunit is closely related in AP-1 and AP-2.
The Rush website, newly redesigned on March 12, 2007, to support the new album, also announced that the band would embark on a tour to begin in the summer. Snakes & Arrows was released on May 1, 2007, in North America, where it debuted at No. 3 on the Billboard 200 with approximately 93,000 units sold in its first week. It peaked at No. 3 in Canada and No. 13 in the UK, selling an estimated 611,000 copies worldwide. Coinciding with the beginning of Atlantic Ocean hurricane season, "Spindrift" was released as the official second radio single on June 1, 2007, while "The Larger Bowl (A Pantoum)" came out as a single on June 25, 2007. "The Larger Bowl" peaked within the top 20 of both the Billboard Mainstream Rock and Mediabase Mainstream charts, but "Spindrift" failed to appear on any commercial chart. The planned intercontinental tour in support of Snakes & Arrows began on June 13, 2007, in Atlanta, coming to a close on October 29, 2007, at Hartwall Arena in Helsinki, Finland. The 2008 portion of the Snakes & Arrows tour began on April 11, 2008, in San Juan, Puerto Rico, at José Miguel Agrelot Coliseum, and concluded on July 24, 2008, in Noblesville, Indiana at the Verizon Wireless Music Center. On April 15, 2008, the band released Snakes & Arrows Live, a double live album documenting the first leg of the tour, recorded at the Ahoy arena in Rotterdam, Netherlands on October 16 and 17, 2007. A DVD and Blu-ray recording of the same concerts was released on November 24, 2008.
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 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.