Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient.[1][2] Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques.
Fractionation is widely employed in many branches of science and technology. Mixtures of liquids and gasses are separated by fractional distillation by difference in boiling point. Fractionation of components also takes place in column chromatography by a difference in affinity between stationary phase and the mobile phase. In fractional crystallization and fractional freezing, chemical substances are fractionated based on difference in solubility at a given temperature. In cell fractionation, cell components are separated by difference in mass.
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A typical protocol to isolate a pure chemical agent from natural origin is, step-by-step separation of extracted components based on differences in their bioassay-guided fractionation physicochemical properties, and assessing the biological activity, followed by next round of separation and assaying. Typically, such work is initiated after a given crude extract is deemed "active" in a particular in vitro assay.
The process of blood fractionation involves separation of blood into its main components. Blood fractionation refers generally to the process of separation using a centrifuge (centrifugation), after which three major blood components can be visualized: plasma, buffy coat and erythrocytes (blood cells). These separated components can be analyzed and often further separated.
The map of the Rosebud Sioux Reservation below illustrates how part of the Tribal treaty land base was carved into thousands of individual allotted tracts by 1903. Although the allotted land is not divided physically, meaning heirs receive an undivided interest in the land, the children, spouses, and other relatives of the original and successive landowners inherit increasingly smaller interests in the land. As a result, fractionation of the ownership interests has grown exponentially over generations. Many allotted tracts now have hundreds of individual owners. For example, a tract on the Lac Courte Oreilles Reservation has more than 1,200 owners. The Federal allotment policies ended with the Indian Reorganization Act of 1934, which helped strengthen Tribal sovereignty by increasing Indian self-governance and responsibility.
Background: Radiotherapy reduces the risk of local recurrence in rectal cancer. However, the optimal radiotherapy fractionation and interval between radiotherapy and surgery is still under debate. We aimed to study recurrence in patients randomised between three different radiotherapy regimens with respect to fractionation and time to surgery.
Background: The Meta-Analysis of Radiotherapy in squamous cell Carcinomas of Head and neck (MARCH) showed that altered fractionation radiotherapy is associated with improved overall and progression-free survival compared with conventional radiotherapy, with hyperfractionated radiotherapy showing the greatest benefit. This update aims to confirm and explain the superiority of hyperfractionated radiotherapy over other altered fractionation radiotherapy regimens and to assess the benefit of altered fractionation within the context of concomitant chemotherapy with the inclusion of new trials.
Methods: For this updated meta-analysis, we searched bibliography databases, trials registries, and meeting proceedings for published or unpublished randomised trials done between Jan 1, 2009, and July 15, 2015, comparing primary or postoperative conventional fractionation radiotherapy versus altered fractionation radiotherapy (comparison 1) or conventional fractionation radiotherapy plus concomitant chemotherapy versus altered fractionation radiotherapy alone (comparison 2). Eligible trials had to start randomisation on or after Jan 1, 1970, and completed accrual before Dec 31, 2010; had to have been randomised in a way that precluded prior knowledge of treatment assignment; and had to include patients with non-metastatic squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx undergoing first-line curative treatment. Trials including a non-conventional radiotherapy control group, investigating hypofractionated radiotherapy, or including mostly nasopharyngeal carcinomas were excluded. Trials were grouped in three types of altered fractionation: hyperfractionated, moderately accelerated, and very accelerated. Individual patient data were collected and combined with a fixed-effects model based on the intention-to-treat principle. The primary endpoint was overall survival.
Findings: Comparison 1 (conventional fractionation radiotherapy vs altered fractionation radiotherapy) included 33 trials and 11 423 patients. Altered fractionation radiotherapy was associated with a significant benefit on overall survival (hazard ratio [HR] 094, 95% CI 090-098; p=00033), with an absolute difference at 5 years of 31% (95% CI 13-49) and at 10 years of 12% (-08 to 32). We found a significant interaction (p=0051) between type of fractionation and treatment effect, the overall survival benefit being restricted to the hyperfractionated group (HR 083, 074-092), with absolute differences at 5 years of 81% (34 to 128) and at 10 years of 39% (-06 to 84). Comparison 2 (conventional fractionation radiotherapy plus concomitant chemotherapy versus altered fractionation radiotherapy alone) included five trials and 986 patients. Overall survival was significantly worse with altered fractionation radiotherapy compared with concomitant chemoradiotherapy (HR 122, 105-142; p=00098), with absolute differences at 5 years of -58% (-119 to 03) and at 10 years of -51% (-130 to 28).
The main goal of this project is to compare the amount of spray nozzle liquid re-entrainment for various low surface area packings/grids, and to help fractionation specialists choose the optimum packing type to minimize wash oil wetting loss. FRI is collaborating with a spray nozzle manufacturer to test one of their new to market nozzles.
The International Plasma and Fractionation Association (IPFA) is an association representing organisations engaged in the collection of plasma and fractionation of it into plasma-derived medicinal products. IPFAs members are from the not-for-profit sector and come from all over the world. They represent both blood establishments collecting plasma and manufactures (fractionators) who produce the plasma-derived products.
IPFAs aim is to enable robust, safe supply and patient access to life-saving plasma-derived medicines, while strengthening the contribution and ability of the public sector to collect plasma within their communities for this purpose. We encourage and help the not-for-profit blood establishment to increase their collection of plasma for fractionation and their aims to conduct this task alongside the collection of other blood components, with a strong an emphasis on donations without financial gain, donor health protection and long-term commitment.
An integral part of our activities are the events we arrange to offer education, discussion on important topics and training in the field of plasma collection and fractionation. The Workshop on Screening and Surveillance of Blood-borne pathogens which we arrange annually since the 1990s in cooperation with the Paul-Ehrlich-Insititut in Germany (PEI) is a well recognised and important meeting for scientists, national authorities, company representatives and other stakeholders with an interest in a continued high safety for blood and plasma products.
a, Solid line indicates a scenario in which there is a concave relationship between vaccine efficacy (vertical axis) and dosage (horizontal axis), whereby a fractionated dose (e.g., approximately half of a standard dose) could provide considerably more than half the effectiveness of the standard dose; the dashed diagonal line is included for reference. If the concave relationship holds, it indicates that providing half doses to a certain number of people could provide a greater level of population immunity than would providing standard doses to half as many people. For reference, the population immunity conferred by vaccination could be estimated via the vaccination coverage multiplied by vaccination effectiveness. b, Another scenario in which very low fractionated doses might not provide any clinical benefit, but fractionation would still provide population benefits above a certain threshold. Here, the solid line crosses the diagonal dashed line at doses approaching half a standard dose, and at the fractionated dose indicated (approximately half a standard dose), there would be an advantage for population immunity to use half doses.
Concerns about the evolution of vaccine resistance have been posited as a potential drawback of dose-sparing strategies. However, vaccines that provide protection against clinical disease seem to also reduce transmission, which indicates that expanding partial vaccination coverage could reduce the incidence of infection. As described in a recent paper, lower prevalence should slow, not accelerate, the emergence and spread of new SARS-CoV-2 variants8. Within-host dynamics are unlikely to overcome these population-level effects. In contrast to some chronic infections, such as infection with human immunodeficiency virus, infection with SARS-CoV-2 in healthy people does not readily select for variants that escape the immune system. Such rapid selection has been reported only in immunocompromised people, who might have better access to vaccines if doses were fractionated in the general population. One other potential concern about fractionation would relate to vaccine hesitancy, if fractionated doses were viewed as inferior. However, the strategy of delaying the second dose of the vaccine applied in the UK and elsewhere has been well accepted as a strategy for providing at least partial protection to a greater number of people8. 006ab0faaa
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