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Academic literature on the topic 'Fractionation'

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Published: 4 June 2021
Last updated: 6 July 2024

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Journal articles on the topic "Fractionation"

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Li, Jianghanyang, Xuan Zhang, John Orlando, Geoffrey Tyndall, and Greg Michalski. "Quantifying the nitrogen isotope effects during photochemical equilibrium between NO and NO<sub>2</sub>: implications for <i>δ</i><sup>15</sup>N in tropospheric reactive nitrogen." Atmospheric Chemistry and Physics 20, no. 16 (August 21, 2020): 9805–19. http://dx.doi.org/10.5194/acp-20-9805-2020.

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Abstract. Nitrogen isotope fractionations between nitrogen oxides (NO and NO2) play a significant role in determining the nitrogen isotopic compositions (δ15N) of atmospheric reactive nitrogen. Both the equilibrium isotopic exchange between NO and NO2 molecules and the isotope effects occurring during the NOx photochemical cycle are important, but both are not well constrained. The nighttime and daytime isotopic fractionations between NO and NO2 in an atmospheric simulation chamber at atmospherically relevant NOx levels were measured. Then, the impact of NOx level and NO2 photolysis rate on the combined isotopic fractionation (equilibrium isotopic exchange and photochemical cycle) between NO and NO2 was calculated. It was found that the isotope effects occurring during the NOx photochemical cycle can be described using a single fractionation factor, designated the Leighton cycle isotope effect (LCIE). The results showed that at room temperature, the fractionation factor of nitrogen isotopic exchange is 1.0289±0.0019, and the fractionation factor of LCIE (when O3 solely controls the oxidation from NO to NO2) is 0.990±0.005. The measured LCIE factor showed good agreement with previous field measurements, suggesting that it could be applied in an ambient environment, although future work is needed to assess the isotopic fractionation factors of NO+RO2/HO2→NO2. The results were used to model the NO–NO2 isotopic fractionations under several NOx conditions. The model suggested that isotopic exchange was the dominant factor when NOx>20 nmol mol−1, while LCIE was more important at low NOx concentrations (<1 nmol mol−1) and high rates of NO2 photolysis. These findings provided a useful tool to quantify the isotopic fractionations between tropospheric NO and NO2, which can be applied in future field observations and atmospheric chemistry models.
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Christner, Emanuel, Martin Kohler, and Matthias Schneider. "The influence of snow sublimation and meltwater evaporation on <i>δ</i>D of water vapor in the atmospheric boundary layer of central Europe." Atmospheric Chemistry and Physics 17, no. 2 (January 25, 2017): 1207–25. http://dx.doi.org/10.5194/acp-17-1207-2017.

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Abstract. Post-depositional fractionation of stable water isotopes due to fractionating surface evaporation introduces uncertainty to various isotope applications such as the reconstruction of paleotemperatures, paleoaltimetry, and the investigation of groundwater formation. In this study, we investigate isotope fractionation at snow-covered moisture sources by combining 17 months of observations of isotope concentration ratios [HD16O] ∕ [H216O] in low-level water vapor in central Europe with a new Lagrangian isotope model. The isotope model is capable of reproducing variations of the observed isotope ratios with a correlation coefficient R of 0.82. Observations from 38 days were associated with cold snaps and moisture uptake in snow-covered regions. Deviations between modeled and measured isotope ratios during the cold snaps were related to differences in skin temperatures (Tskin). Analysis of Tskin provided by the Global Data Assimilation System (GDAS) of the NCEP implies the existence of two regimes of Tskin with different types of isotope fractionation during evaporation: a cold regime with Tskin < Tsubl,max = −7.7 °C, which is dominated by non-fractionating sublimation of snow, and a warmer regime with Tsubl,max < Tskin < 0 °C, which is dominated by fractionating evaporation of meltwater. Based on a sensitivity study, we assess an uncertainty range of the determined Tsubl,max of −11.9 to −2.9 °C. The existence of the two fractionation regimes has important implications for the interpretation of isotope records from snow-covered regions as well as for a more realistic modeling of isotope fractionation at snow-covered moisture sources. For these reasons, more detailed experimental studies at snow-covered sites are needed to better constrain the Tsubl,max and to further investigate isotope fractionation in the two regimes.
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Sponheimer, Matt, Todd Robinson, Linda Ayliffe, Ben Passey, Beverly Roeder, Lisa Shipley, Elvia Lopez, Thure Cerling, Denise Dearing, and Jim Ehleringer. "An experimental study of carbon-isotope fractionation between diet, hair, and feces of mammalian herbivores." Canadian Journal of Zoology 81, no. 5 (May 1, 2003): 871–76. http://dx.doi.org/10.1139/z03-066.

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The carbon-isotope composition of hair and feces offers a glimpse into the diets of mammalian herbivores. It is particularly useful for determining the relative consumption of browse and graze in tropical environments, as these foods have strongly divergent carbon-isotope compositions. Fecal δ13C values reflect the last few days consumption, whereas hair provides longer term dietary information. Previous studies have shown, however, that some fractionation occurs between dietary δ13C values and those of hair and feces. Accurate dietary reconstruction requires an understanding of these fractionations, but few controlled-feeding studies have been undertaken to investigate these fractionations in any mammalian taxa, fewer still in large mammalian herbivores. Here, we present data from the first study of carbon-isotope fractionation between diet, hair, and feces in multiple herbivore taxa. All taxa were fed pure alfalfa (Medicago sativa) diets for a minimum period of 6 months, at which point recently grown hair was shaved and analyzed for carbon isotopes. The mean observed diet–hair fractionation was +3.2‰, with a range of +2.7 to +3.5‰. We also examined diet–feces fractionation for herbivores on alfalfa and bermudagrass (Cynodon dactylon) feeds. The mean diet–feces fractionation for both diets was –0.8‰, with less fractionation for alfalfa (–0.6‰) than bermudagrass (–1.0‰). Fecal carbon turnover also varies greatly between taxa. When diets were switched, horse (Equus caballus) feces reflected the new diet within 60 h, but alpaca (Lama pacos) feces did not equilibrate with the new diet for nearly 200 h. Thus, fecal carbon isotopes provide far greater dietary resolution for hindgut-fermenting horses than foregut-fermenting alpacas.
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Detmers, Jan, Volker Brüchert, Kirsten S. Habicht, and Jan Kuever. "Diversity of Sulfur Isotope Fractionations by Sulfate-Reducing Prokaryotes." Applied and Environmental Microbiology 67, no. 2 (February 1, 2001): 888–94. http://dx.doi.org/10.1128/aem.67.2.888-894.2001.

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ABSTRACT Batch culture experiments were performed with 32 different sulfate-reducing prokaryotes to explore the diversity in sulfur isotope fractionation during dissimilatory sulfate reduction by pure cultures. The selected strains reflect the phylogenetic and physiologic diversity of presently known sulfate reducers and cover a broad range of natural marine and freshwater habitats. Experimental conditions were designed to achieve optimum growth conditions with respect to electron donors, salinity, temperature, and pH. Under these optimized conditions, experimental fractionation factors ranged from 2.0 to 42.0‰. Salinity, incubation temperature, pH, and phylogeny had no systematic effect on the sulfur isotope fractionation. There was no correlation between isotope fractionation and sulfate reduction rate. The type of dissimilatory bisulfite reductase also had no effect on fractionation. Sulfate reducers that oxidized the carbon source completely to CO2 showed greater fractionations than sulfate reducers that released acetate as the final product of carbon oxidation. Different metabolic pathways and variable regulation of sulfate transport across the cell membrane all potentially affect isotope fractionation. Previous models that explained fractionation only in terms of sulfate reduction rates appear to be oversimplified. The species-specific physiology of each sulfate reducer thus needs to be taken into account to understand the regulation of sulfur isotope fractionation during dissimilatory sulfate reduction.
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Laitinen, Ossi, Kalle Kemppainen, Tuomas Stoor, and Jouko Niinimäki. "Fractionation of pulp and paper particles selectively by size." BioResources 6, no. 1 (January 15, 2011): 672–85. http://dx.doi.org/10.15376/biores.6.1.672-685.

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A study was made of the classification of pulp, paper, and peat particles by size with a device called a tube flow fractionator. An accurate and simple experimental model was formulated in order to estimate the time required for fractionation, yielding an excellent correlation between the observed and predicted fractionation times. The results showed that the fractionation time of a certain size of pulp, paper, and peat particles in the tube flow device can be accurately estimated from the length, width, and thickness of the particle. The results can be used to facilitate the selection of specific fractions of pulp and paper samples.
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Fujii, T., F. Moynier, A. Agranier, E. Ponzevera, and M. Abe. "Isotope fractionation of palladium in chemical exchange reaction." Proceedings in Radiochemistry 1, no. 1 (September 1, 2011): 339–44. http://dx.doi.org/10.1524/rcpr.2011.0060.

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Abstract Palladium isotopes were fractionated by the solvent extraction technique with a crown ether. After purification by ion-exchange chemistry, the isotopic ratios of 105Pd/106Pd, 108Pd/106Pd, and 110Pd/106Pd were determined by multiple-collector inductively coupled plasma mass spectrometry. Isotope fractionations between the two phases were found to be larger than 0.1‰. The isotope fractionation of the odd atomic mass isotope (105Pd) showed a deviation from that estimated from the even atomic mass isotopes (106Pd, 108Pd, and 110Pd). The mass-independent isotope fractionation found was attributable to the nuclear field shift effect. The quantum chemical calculations for the different Pd species supported the validity of the isotope fractionation factors obtained.
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Ledgard, SF, KC Woo, and FJ Bergersen. "Isotopic Fractionation During Reduction of Nitrate and Nitrite by Extracts of Spinach Leaves." Functional Plant Biology 12, no. 6 (1985): 631. http://dx.doi.org/10.1071/pp9850631.

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The isotopic fractionations of nitrogen during the reduction of NO3- and NO2- in a cytosolic fraction and in a chloroplast preparation from spinach (Spinacia oleracea L.) leaves were determined. The reduction of NO3- to NH3 was studied using a reconstituted system containing cytosolic extract and intact chloroplasts, while a chloroplast system was used for NO2- reduction. In the reconstituted systems the ratio of nitrate reductase activity to nitrite reductase activity had a large effect on the relative amounts of NO2- and NH3 formed. Ammonia predominated when the nitrate reductase to nitrite reductase activity ratio was 1 : 5 and this ratio was used in the isotopic fractionation studies. Significant isotopic fractionation of N was observed in the reconstituted system but not in the chloroplast system. This indicates that the observed isotopic fractionation was associated with the reduction of NO3- to NO2- by nitrate reductase. The isotopic fractionation (i.e. δ15Nproduct - δ15Nsubstrate) for this reaction was - 15‰.
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Fehér, Anikó, Soma Bedő, and Csaba Fehér. "Comparison of Enzymatic and Acidic Fractionation of Corn Fiber for Glucose-rich Hydrolysate and Bioethanol Production by Candida boidinii." Periodica Polytechnica Chemical Engineering 65, no. 3 (May 18, 2021): 320–30. http://dx.doi.org/10.3311/ppch.17431.

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Corn fiber is a by-product of the corn wet milling process and a promising raw material to produce bioethanol in a bio-refinery process. In this study, enzymatic and acidic fractionations of corn fiber were compared with particular attention to produce glucose-rich hydrolyzates. The acidic fractionation contained two, sequential, sulphuric acid-catalyzed, hydrolysis steps based on our previous study. In the enzymatic fractionation process, corn fiber was pre-treated by soaking in aqueous ammonia (18.5 % (w/w) dry matter, 15 % (w/w) ammonia solution, 24 hours) and then hydrolyzed by using Hemicellulase (NS 22002) enzyme cocktail. The cellulose part of the solid residues obtained after the acidic and enzymatic fractionation processes was enzymatically hydrolyzed by using Cellic Ctec2 and Novozymes 188 (12.5 % (w/w) dry matter, 50 °C, 72 hours). Cellulose hydrolysis after the acidic and enzymatic fractionation resulted in a supernatant containing 64 g/L and 25 g/L glucose, respectively. Therefore, ethanol fermentation experiments were performed in Separated Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) configurations after the acidic fractionation of corn fiber. SHF configuration was found to be more advantageous regarding the achievable ethanol yield. Although the fermentation with Candida boidinii NCAIM Y.01308 was accomplished within longer time (43 hours) compared to Saccharomyces cerevisiae (5 hours), the achieved ethanol yields were similar (79%) during the SHF process. It was concluded that acidic fractionation is more efficient to produce glucose-rich hydrolyzate from corn fiber compared to enzymatic fractionation, and Candida boidinii is suitable for ethanol fermentation on the glucose-rich hydrolyzate.
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Morasch, Barbara, Hans H. Richnow, Bernhard Schink, and Rainer U. Meckenstock. "Stable Hydrogen and Carbon Isotope Fractionation during Microbial Toluene Degradation: Mechanistic and Environmental Aspects." Applied and Environmental Microbiology 67, no. 10 (October 1, 2001): 4842–49. http://dx.doi.org/10.1128/aem.67.10.4842-4849.2001.

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ABSTRACT Primary features of hydrogen and carbon isotope fractionation during toluene degradation were studied to evaluate if analysis of isotope signatures can be used as a tool to monitor biodegradation in contaminated aquifers. D/H hydrogen isotope fractionation during microbial degradation of toluene was measured by gas chromatography. Per-deuterated toluene-d 8 and nonlabeled toluene were supplied in equal amounts as growth substrates, and kinetic isotope fractionation was calculated from the shift of the molar ratios of toluene-d 8 and nondeuterated toluene. The D/H isotope fractionation varied slightly for sulfate-reducing strain TRM1 (slope of curve [b] = −1.219), Desulfobacterium cetonicum(b = −1.196), Thauera aromatica(b = −0.816), and Geobacter metallireducens (b = −1.004) and was greater for the aerobic bacterium Pseudomonas putidamt-2 (b = −2.667). The D/H isotope fractionation was 3 orders of magnitude greater than the13C/12C carbon isotope fractionation reported previously. Hydrogen isotope fractionation with nonlabeled toluene was 1.7 and 6 times less than isotope fractionation with per-deuterated toluene-d 8 and nonlabeled toluene for sulfate-reducing strain TRM1 (b = −0.728) andD. cetonicum (b = −0.198), respectively. Carbon and hydrogen isotope fractionation during toluene degradation by D. cetonicum remained constant over a growth temperature range of 15 to 37°C but varied slightly during degradation by P. putida mt-2, which showed maximum hydrogen isotope fractionation at 20°C (b = −4.086) and minimum fractionation at 35°C (b = −2.138). D/H isotope fractionation was observed only if the deuterium label was located at the methyl group of the toluene molecule which is the site of the initial enzymatic attack on the substrate by the bacterial strains investigated in this study. Use of ring-labeled toluene-d 5 in combination with nondeuterated toluene did not lead to significant D/H isotope fractionation. The activity of the first enzyme in the anaerobic toluene degradation pathway, benzylsuccinate synthase, was measured in cell extracts of D. cetonicum with an initial activity of 3.63 mU (mg of protein)−1. The D/H isotope fractionation (b = −1.580) was 30% greater than that in growth experiments with D. cetonicum. Mass spectroscopic analysis of the product benzylsuccinate showed that H atoms abstracted from the toluene molecules by the enzyme were retained in the same molecules after the product was released. Our findings revealed that the use of deuterium-labeled toluene was appropriate for studying basic features of D/H isotope fractionation. Similar D/H fractionation factors for toluene degradation by anaerobic bacteria, the lack of significant temperature dependence, and the strong fractionation suggest that analysis of D/H fractionation can be used as a sensitive tool to assess degradation activities. Identification of the first enzyme reaction in the pathway as the major fractionating step provides a basis for linking observed isotope fractionation to biochemical reactions.
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Schoeller, D. A., C. A. Leitch, and C. Brown. "Doubly labeled water method: in vivo oxygen and hydrogen isotope fractionation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 251, no. 6 (December 1, 1986): R1137—R1143. http://dx.doi.org/10.1152/ajpregu.1986.251.6.r1137.

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The accuracy and precision of the doubly labeled water method for measuring energy expenditure are influenced by isotope fractionation during evaporative water loss and CO2 excretion. To characterize in vivo isotope fractionation, we collected and isotopically analyzed physiological fluids and gases. Breath and transcutaneous water vapor were isotopically fractionated. The degree of fractionation indicated that the former was fractionated under equilibrium control at 37 degrees C, and the latter was kinetically fractionated. Sweat and urine were unfractionated. By use of isotopic balance models, the fraction of water lost via fractionating routes was estimated from the isotopic abundances of body water, local drinking water, and dietary solids. Fractionated water loss averaged 23% (SD = 10%) of water turnover, which agreed with our previous estimates based on metabolic rate, but there was a systematic difference between the results based on O2 and hydrogen. Corrections for isotopic fractionation of water lost in breath and (nonsweat) transcutaneous loss should be made when using labeled water to measure water turnover or CO2 production.
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Dissertations / Theses on the topic "Fractionation"

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Wang, Baoyong. "Fractionation Statistics." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31001.

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Paralog reduction, the loss of duplicate genes after whole genome duplication (WGD) is a pervasive process. Whether this loss proceeds gene by gene or through deletion of multi-gene DNA segments is controversial, as is the question of fractionation bias, namely whether one homeologous chromosome is more vulnerable to gene deletion than the other. As a null hypothesis, we first assume deletion events, on one homeolog only, excise a geometrically distributed number of genes with unknown mean mu, and these events combine to produce deleted runs of length l, distributed approximately as a negative binomial with unknown parameter r; itself a random variable with distribution pi(.). A biologically more realistic model requires deletion events on both homeologs distributed as a truncated geometric. We simulate the distribution of run lengths l in both models, as well as the underlying pi(r), as a function of mu, and show how sampling l allows us to estimate mu. We apply this to data on a total of 15 genomes descended from 6 distinct WGD events and show how to correct the bias towards shorter runs caused by genome rearrangements. Because of the difficulty in deriving pi(.) analytically, we develop a deterministic recurrence to calculate each pi(r) as a function of mu and the proportion of unreduced paralog pairs. This is based on a computing formula containing nested sums. The parameter mu can be estimated based on run lengths of single-copy regions. We then reduce the computing formulae, at least in the one-sided case, to closed form. This virtually eliminates computing time due to highly nested summations. We formulate a continuous version of the fractionation process, deleting line segments of exponentially distributed lengths in analogy to geometric distributed numbers of genes. We derive nested integrals and discover that the number of previously deleted regions to be skipped by a new deletion event is exactly geometrically distributed. We undertook a large simulation experiment to show how to discriminate between the gene-by-gene duplicate deletion model and the deletion of a geometrically distributed number of genes. This revealed the importance of the effects of genome size N, the mean of the geometric distribution, the progress towards completion of the fractionation process, and whether the data are based on runs of deleted genes or undeleted genes.
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Chen, Xiaocai Joyce. "Fractionation of nylon fibres." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ28927.pdf.

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Ghosh, Raja. "Protein fractionation using ultrafiltration." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302133.

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Rajah, Kanes K. "Fractionation of milk fat." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233844.

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Al-Jabari, Maher. "Particle fractionation by elutriation-spouting." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28409.

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Pulp fibers can be spouted in a conical vessel if the inlet Reynolds number is above a critical value which varies linearly with mass of pulp in the vessel. Continuous pulp spouting is also feasible in a wedge-like vessel within certain limits of flow rate and inlet pulp consistency. Spouting hydrodynamics and particle separation behavior in both vessels were investigated for pulp fibers and recycled pulp suspensions.
The minimum spouting velocity (MSV), spouting stability and the pressure drop-flow rate relationship were determined for liquid spouting of pulp fibers and of rigid particles. Liquid spouting of rigid particles is similar to gaseous spouting; pulp spouting is different. The liquid flow field in a conical spouted bed of pulp fibers is of a jet expansion type. A model for predicting the MSV for spouting pulp fibers was developed based on visual observation of the transition of the jet flow patterns in the conical vessel.
Small particles including both ink and pulp fines can be elutriated from a spouted bed of a recycled pulp suspension, with little fiber loss, in both semi-batch and continuous modes using conical and wedge-like vessels, respectively. Both processes were studied using on-line measurement of the exit particle concentration.
For the semi-batch process, the first order elutriation coefficient increased with the flow rate, but was about the same for all pulps. Based on the analysis of the flow field around a porous spherical particle in a shear flow, an elutriation model was developed for fine particle removal from a suspension of porous coarse particles. For the continuous operation, the particle separation mechanism and the fractional particle removal were investigated. Separation occurs by excluding fibers from the top stream, while fines are split according to the ratio of top to bottom flow rates.
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Wehmeier, Silvia. "Antimony isotope fractionation through biomethylation." Thesis, University of Aberdeen, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401160.

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Fermenter cultures with anaerobe bacteria communities (sewage sludge medium) were analysed for volatile and non-volatile methylantimony species.  Gas-samples were analysed by GC-ICP-MS, and fermenter sludge medium and cytosol by HG-GC-ICP-MS.  Trimethylstibine was the sole volatile species, and non-volatile methylantimony species were found in the fermenter sludge medium, but higher levels were found in sludge cytosol. Antimony isotopic fractionation values were determined as high as d 123Sb + 150 in one fermenter experiment.  Additionally, the species-specific isotope ratio ‘fingerprint’ from the methylantimony species confirmed the mechanism proposed by Challenger for the biomethylation process.  It showed the formation of partially methylated antimony species as intermediates.  However, other stimulated bacteria cultures did not show any antimony isotope fractionation through biomethylation. Further investigation into the biomethylation process was studied to determine whether antimonate, Sb(V), is methylated by anaerobe bacteria communities.  For this purpose, isotopically enriched 123Sb(V) was used to monitor the antimony isotope ratio of the methylantimony metabolite species.  The antimonate was stepwise methylated. Environmental gas samples from a landfill site and a digester plant, showed trimethylstibine as the prominent organometal(loid)-species.  Moreover, the biovolatilisation species trimethylstibine was determined to have an antimony isotope fractionation value of d 123Sb + 10. Antimony-glutathione complexes were identified in both in vivo and in vitro studies of antimony interactions with biomolecules.  The molecular structures of these Sb-GS complexes were determined using FI-ESI-MS.  The glutathione influence was then further investigated in a non-enzymatic methylation of antimony with methylcobalamin.  The prominent species produces in vivo was monomethylantimony, with small amount of dimethylantimony.
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Katz, David P. "The Fractionation of Working Memory." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1559732086225506.

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Dean, Lauren Rachael. "Neural pathways of movement fractionation." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2812.

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Stroke is a common neurological event which often results in motor deficits of the hand and arm. The reticulospinal tract (RST) may partly underlie residual hand and arm movement ability after a stroke but remains poorly characterised. A greater understanding of the RST could inform work to improve motor recovery. Additionally, the development of non-invasive methods of probing the RST in humans should allow comparison of the characteristics of the RST across species. It has been suggested that the RST is involved in mediating muscle responses to auditory startle, experimentally known as the StartReact paradigm. However, it was not clear how this pathway was involved. A human experiment presented here suggests that the RST comprises the final pathway in the StartReact effect, confirming it as a technique to probe the RST in humans. Other factors such as habituation and the validity of a marker of the StartReact effect were also further explored; these findings may inform future use of the technique. The output divergence, co-activation patterns, level of fractionation and synergies produced by the RST were further characterised in macaques and baboons; these factors had previously been mostly unexplored. In macaques, two subdivisions of primary motor cortex (M1) were also characterised in order to compare to the RST. These subdivisions are based upon the presence of corticomotoneuronal (CM) cells, and consist of ‘old’ (CM cells absent) and ‘new’ (CM cells present) M1. Stimulation of new M1 produced a higher level of fractionation of movement than stimulation of old M1 and the reticular formation (RF). The RF is suggested to produce slightly more fractionated behaviour than old M1, though the baboon RF responses may be less fractionated than those from macaque old M1. Output divergence of the RF as well as old and new M1 was also explored. However, methodological limitations may have biased the results towards muscles with more excitable motoneurons, or monosynaptic connections. Abstract ii In baboons, threshold stimulation elicited responses in upper limb and axial muscles only, with higher stimulation intensities or trains of pulses required to activate leg muscles. In contrast to long-held beliefs about RST output, distal upper limb muscles were more commonly activated than proximal ones. Previously reported attempts to record natural electromyography (EMG) data from macaques were limited to controlled experimental settings, and hence may have differed from EMG observed during truly natural behaviours. Here, EMG was recorded from 18 muscles in one macaque over several hours of natural, untrained activity in her home cage. Two matrix decomposition algorithms extracted three to four dominant synergies from the data. This number is comparable to that previously described for ‘natural’ behaviour in more controlled conditions, suggesting that it accurately reflects the dominant synergies used across both conditions. Future work should aim to delineate the respective contributions of the RST and corticospinal tract to natural movement and to develop approaches to manipulate RST projections in humans to improve post-stroke motor outcomes.
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Chen, Zhi. "Separation with electrical field-flow fractionation." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013788.

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Chand, Amita. "On-farm fractionation of milk components." The University of Waikato, 2006. http://hdl.handle.net/10289/2669.

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Methods for on-farm extraction of low-concentration (minor) proteins from raw whole bovine milk directly after milking were explored. These minor proteins have high commercial value. Lactoferrin (LF) and lactoperoxidase (LP) were used as model proteins for extraction using cation exchange chromatography. Laboratory fractionations showed that milk could be processed by conventional column chromatography without excessive column backpressures if resin with large particles sizes were used and the temperature was high enough so fat in the milk was malleable; ideally the milk should be near the secretion temperature of 37oC. Processing parameters such as equilibrium and dynamic capacities were determined for SP Sepharose ™ (GE Healthcare Technologies) and Bio Rex 70 (BioRad Laboratories) resins. SP Sepharose Big Beads (SP BB) were found to be more suitable than BR 70, for raw whole milk processing due to the larger size (200 um). Design considerations showed that column chromatography was not the most practical method for on-farm processing of fresh, raw whole milk. Trials with a single-stage stirred tank showed that SP BB resin could extract up to 65% of LF (initial LF concentration of 0.5 mg/mL) with a 10-minute adsorption time. The composite non-linear (CNL) model of Rowe et al. (1999) was used to describe LF uptake by SP BB resin in raw whole milk with initial LF concentrations of 0 to 1.0 mg/mL and resin:milk volume ratios of 0.010, 0.012, 0.017 and 0.024 over 45-minute contact times. The CNL model could be used to predict LF yields if initial feed concentration, milk and resin volumes, and contact times were known. Laboratory extractions showed that processing did not significantly affect bulk milk composition (fat, protein, lactose and total solids), indicating that the milk could be used for conventional processing after the minor proteins had been extracted. Resin cleaning and regeneration studies, using a procedure similar to that recommended by the resin supplier, showed that the Sepharose resin had not degraded and there was no significant decrease in binding capacity after 50 extraction cycles. A Protein Fractionation Robot (PFR) prototype based on a single-stage stirred tank and the operating parameters obtained from the laboratory trials was designed, assembled and coupled to an Automated Milking System (AMS) to process fresh, raw whole milk from individual cows immediately after milking. The LF and LP extracted from the milk from 16 individual cows were 19.7 - 55.2% (35.6 10.2%) and 21.2 - 99.5% (87.1 12.0%) respectively. Generally, higher extraction levels were obtained at higher resin:milk ratios. The amount of LF extracted on-farm agreed within 14.1 9.8% of those predicted by the CNL model, with predicted values generally being higher. The experimental on-farm adsorption values were calculated using data of LF recovered after elution, so differences between actual and predicted values may be due to losses during post-adsorption processing. Economic feasibility studies, based on experimental data from the PFR and realistic wholesale prices for LF and LP ($400 and $150/kg respectively) showed that PFR-based processing is economically viable if the farmer is paid for the LF and LP produced as well as the bulk milk. This system would have a payback period of approximately five years and an internal rate of return of 14.5%. Further case studies determined the sensitivity of the economics to various operating parameters and value/cost assumptions, including producing recombinant human protein from transgenic bovine milk. These studies showed that the higher the value of the processed raw milk, the higher the absorptive capacity of the resin, and the higher the value of the extracted protein, the more favourable the economics. In the extreme case of producing a very high value therapeutic protein (e.g. $20 000), the payback period could be as low as 0.3 years, with an internal rate of return of 818%.
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Books on the topic "Fractionation"

1

Francuskiewicz, Frieder. Polymer Fractionation. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78704-1.

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Francuskiewicz, F. Polymer fractionation. Berlin: Springer-Verlag, 1994.

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H, Hendry J., ed. Fractionation in radiotherapy. London: Taylor & Francis, 1987.

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Trombetta, Mark, Jean-Philippe Pignol, Paolo Montemaggi, and Luther W. Brady, eds. Alternate Fractionation in Radiotherapy. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-51198-6.

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1957-, Schimpf Martin E., Caldwell Karin 1940-, and Giddings J. Calvin 1930-, eds. Field flow fractionation handbook. New York: Wiley-Interscience, 2000.

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Singh, Narendra. Green vegetation fractionation technology. New Delhi: Oxford & IBH Pub. Co., 1996.

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Green vegetation fractionation technology. Lebanon, NH: Science Publishers, 1996.

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Uglea, Constantin V. Caracterization Polymer Characterization. Fractionation. Bucharest: Technical Editorial House, 1985.

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Smit Sibinga, C. Th, P. C. Das, and S. Seidl, eds. Plasma Fractionation and Blood Transfusion. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4613-2631-1.

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1943-, Graham J. M., and Rickwood D, eds. Subcellular fractionation: A practical approach. Oxford: IRL Press at Oxford University Press, 1997.

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Book chapters on the topic "Fractionation"

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Stern, Jennifer C. "Fractionation." In Encyclopedia of Astrobiology, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_595-2.

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Stern, Jennifer C. "Fractionation." In Encyclopedia of Astrobiology, 891. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_595.

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Stern, Jennifer C. "Fractionation." In Encyclopedia of Astrobiology, 610–11. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_595.

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Eggenkamp, Hans. "Fractionation." In The Geochemistry of Stable Chlorine and Bromine Isotopes, 73–74. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-28506-6_6.

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Fry, Brian. "Fractionation." In Stable Isotope Ecology, 194–276. New York, NY: Springer New York, 2006. http://dx.doi.org/10.1007/0-387-33745-8_7.

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Gooch, Jan W. "Fractionation." In Encyclopedic Dictionary of Polymers, 324. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_5268.

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Dijkstra, Albert J. "Fractionation." In Edible Oil Processing from a Patent Perspective, 243–53. Boston, MA: Springer US, 2012. http://dx.doi.org/10.1007/978-1-4614-3351-4_12.

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Stern, Jennifer C. "Fractionation." In Encyclopedia of Astrobiology, 1081–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/978-3-662-65093-6_595.

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Francuskiewicz, Frieder. "Partition Fractionation." In Polymer Fractionation, 145–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78704-1_11.

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Francuskiewicz, Frieder. "Cross Fractionation." In Polymer Fractionation, 177–83. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78704-1_12.

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Conference papers on the topic "Fractionation"

1

Lakemond, Catriona. "Insect protein fractionation." In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.115300.

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Fruhstorfer, Peter, and Reinhard Niessner. "Flow-field-flow-fractionation as a new tool for fractionating aquatic colloids." In European Symposium on Optics for Environmental and Public Safety, edited by Tuan Vo-Dinh. SPIE, 1995. http://dx.doi.org/10.1117/12.224091.

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DeFelice, Christopher, Yan Hu, Wenzhong Wang, Fang-Zhen Teng, Shichun Huang, and Frederick Frey. "Crystal Fractionation-Induced Isotope Fractionation in Basalts from Mauna Kea, Hawaii." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.538.

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Sankoff, David. "Keynote: Aspects of fractionation." In 2012 IEEE 2nd International Conference on Computational Advances in Bio and Medical Sciences (ICCABS). IEEE, 2012. http://dx.doi.org/10.1109/iccabs.2012.6182617.

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Terray, Alex, Joseph D. Taylor, and Sean J. Hart. "Optical chromatographic sample fractionation." In SPIE NanoScience + Engineering, edited by Kishan Dholakia and Gabriel C. Spalding. SPIE, 2009. http://dx.doi.org/10.1117/12.828147.

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Cook, Michelle M., M. D. Rahman, Stan F. Wanat, Douglas S. McKenzie, Balaji Narasimhan, Robert K. Fea, and Melodie I. Munoz. "Alternate novolak resin fractionation." In Microlithography '99, edited by Will Conley. SPIE, 1999. http://dx.doi.org/10.1117/12.350168.

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Bilenker, Laura D., Anaïs Fourny, Dominique Weis, James S. Scoates, and Stearns A. Morse. "SIGNIFICANT FE ISOTOPE FRACTIONATION WITHIN THE KIGLAPAIT LAYERED INTRUSION REFLECTS CRYSTAL FRACTIONATION." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-302138.

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Liu, Chia-Pin, and Dar-Zen Chen. "On the Embedded Kinematic Fractionation of Epicyclic Gear Trains." In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/dac-8660.

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Abstract In this paper, the concept of kinematic fractionation is introduced for epicyclic gear trains (EGTs) which contains structural fractionation as a degenerate case. Kinematic fractionation provides a viewpoint to determine the type of fractionation of an EGT by distinguishing the independent transmission path(s) inside. With the concept of kinematic fractionation, kinematically independent group(s) embedded in an EGT can be identified. A composition list, which depicts the links and the link connection in the associated group, is used to determine the type of fractionation. It is found that most previously enumerated structurally non-fractionated EGTs in the literature are kinematically fractionated. It is shown that a structurally non-fractionated EGT may be kinematically fractionated while a structurally fractionated EGT must be kinematically fractionated. The concept of kinematic fractionation can lead to efficient topological analysis of EGTs with physical comprehension.
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Hockin, Matt, Himanshu J. Sant, Mario Capecchi, and Bruce K. Gale. "Dean flow fractionation of chromosomes." In SPIE BiOS, edited by Bonnie L. Gray and Holger Becker. SPIE, 2016. http://dx.doi.org/10.1117/12.2219842.

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Ouchani, Samir. "Towards a fractionation-based verification." In SAC '19: The 34th ACM/SIGAPP Symposium on Applied Computing. New York, NY, USA: ACM, 2019. http://dx.doi.org/10.1145/3297280.3297480.

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Reports on the topic "Fractionation"

1

O'Leary, M. H. (Carbon isotope fractionation inplants). Office of Scientific and Technical Information (OSTI), January 1990. http://dx.doi.org/10.2172/7206375.

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Marti-Arbona, Ricardo, Noah Jemison, Robert F. Williams, Hakim Boukhalfa, Chris Michael Yeager, Ning Xu, and Velimir Valentinov Vesselinov. Biogenic uranium isotope fractionation. Office of Scientific and Technical Information (OSTI), May 2020. http://dx.doi.org/10.2172/1631550.

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Giddings, J. C. Field-flow fractionation of chromosomes. Office of Scientific and Technical Information (OSTI), April 1993. http://dx.doi.org/10.2172/6434224.

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Giddings, J. C. Field-flow fractionation of chromosomes. Office of Scientific and Technical Information (OSTI), September 1990. http://dx.doi.org/10.2172/6370502.

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Giddings, J. C. Field-flow fractionation of chromosomes. Office of Scientific and Technical Information (OSTI), September 1991. http://dx.doi.org/10.2172/5745557.

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O`Leary, M. H. [Carbon isotope fractionation inplants]. Final report. Office of Scientific and Technical Information (OSTI), December 1990. http://dx.doi.org/10.2172/10153604.

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Oldberg, Nick. SOP for Nuclear and Cytoplasmic Fractionation. ResearchHub Technologies, Inc., April 2024. http://dx.doi.org/10.55277/researchhub.s3y61f7f.

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Resasco, Daniel, Lance Lobban, Steven Crossley, Vikas Khanna, Christos Maravelias, Lucia Petkovic, and Nhung Duong. Fractionation and catalytic upgrading of bio-oil. Office of Scientific and Technical Information (OSTI), January 2018. http://dx.doi.org/10.2172/1417911.

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Wang, A., and K. Fisher. Acoustic Filtration, Fractionation, and Mixing in Microfluidic Systems. Office of Scientific and Technical Information (OSTI), February 2002. http://dx.doi.org/10.2172/15006208.

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Glaeser, R. M. Dose fractionation theorem in 3-D reconstruction (tomography). Office of Scientific and Technical Information (OSTI), February 1997. http://dx.doi.org/10.2172/525915.

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