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981.
Jorge González-Domínguez Osni A. Marques María J. Martín Juan Touriño 《The Journal of supercomputing》2014,70(2):816-829
This paper examines four different strategies, each one with its own data distribution, for implementing the parallel conjugate gradient (CG) method and how they impact communication and overall performance. Firstly, typical 1D and 2D distributions of the matrix involved in CG computations are considered. Then, a new 2D version of the CG method with asymmetric workload, based on leaving some threads idle during part of the computation to reduce communication, is proposed. The four strategies are independent of sparse storage schemes and are implemented using Unified Parallel C (UPC), a Partitioned Global Address Space (PGAS) language. The strategies are evaluated on two different platforms through a set of matrices that exhibit distinct sparse patterns, demonstrating that our asymmetric proposal outperforms the others except for one matrix on one platform. 相似文献
982.
Enterotoxigenic <Emphasis Type="Italic">Escherichia coli</Emphasis> strains bind bovine milk gangliosides in a ceramide-dependent process 总被引:2,自引:0,他引:2
Diarrhea caused by enterotoxigenic Escherichia coli (ETEC) is the main infectious disease of newborn calves. The first step of infection involves bacterial attachment to the
intestinal mucosa. This adhesion is mediated by fimbriae that recognize some glycoconjugates on the host cell surface, in
particular, several gangliosides. Because milk also contains gangliosides, these have been suggested to serve as ligands for
bacterial fimbriae and thus prevent the bacterial attachment to mucosa. The most relevant ETEC strains in calves, including
those with K99 and F41 fimbriae, were assayed to determine whether they are able to bind gangliosides isolated from several
stages of bovine lactation. Both GM3 and GD3, the main gangliosides of milk, were recognized by ETEC strains, although the
different fimbriae showed diverse levels of affinity. Unexpectedly, the adhesion to colostral gangliosides was considerably
weaker than that to gangliosides from the other stages of lactation. Because the carbohydrate moiety did not change and because
differences in the percentages of unsaturated FA and sphingosine between colostrum and other stages were observed, we conclude
that the differences in adhesion could be due to a different composition of the ganglioside caramide. 相似文献
983.
Dietary fat and body weight control 总被引:3,自引:0,他引:3
The global obesity epidemic has heightened the debate about dietary factors contributing to weight gain. Media stories have
promulgated the notion that obesity has increased despite reductions in dietary fat intake. Some have even speculated that
lower dietary fat levels may be driving the rapid rise in weight gain within the population. A close examination of the science
reveals a different picture and supports the hypothesis that dietary fat, within the context of the total dietary composition
consumed by many populations, promotes obesity. Hence, dietary fat control is still an important strategy as part of an overall
approach to body weight management in our modern environment. Dietary fat increases the energy density of foods. Abundant
evidence from preclinical and clinical studies indicates that fat promotes excess energy intake and positive energy balance.
Dietary fat does not promote its own oxidation in the body and is stored efficiently, promoting a positive fat balance. Thus,
both the behavioral and metabolic responses to dietary fat increase the probability of positive energy balance and body fat
gain. Restoring fat balance when consuming diets rich in fat requires increasing the size of the body fat mass, increasing
physical activity, or reducing dietary fat intake. Numerous epidemiologic, preclinical, and controlled clinical studies have
shown that body fat is positively associated with dietary fat intake and that dietary fat manipulation leads to appropriate
changes in body fat mass. Finally, data from the National Weight Control Registry, a database of >3000 individuals who have
successfully maintained a substantial weight loss, indicate that moderating dietary fat intake is a key strategy for long-term
management of body weight. 相似文献
984.
Short fibers and fine particles of β-SiC were obtained by pyrolysis of Colombian rice husk (RH). The synthesis of SiC was carried out in a gas furnace: a mathematical model was developed in order to design and build this equipment and the process was optimized using an experimental design that included variables such as temperature, pyrolysis time, type of catalyst, and process atmosphere. The obtained material was characterized by using FTIR, DRX and SEM for microstructural characterization and EDS technique for chemical analysis. 相似文献
985.
Investigations on white spirit and acetone permeation resistance of modified polyamide and nylon 6 clay (MPANYC) blends and their corresponding polyethylene/MPANYC bottles were reported in this study. The white spirit and acetone permeation resistance of MPANYC sheets improve consistently with increasing NYC contents present in MPANYC resins after blending nylon 6 clay (NYC) in modified polyamide (MPA) resins. However, the order of barrier improvement of the PE/MPANYC and PE/NYC bottle specimens is not corresponding to the order of barrier improvement of the MPANYC and/or NYC barrier resins added in PE. The blow-molded PE/NYC bottle specimen exhibits similarly worse white spirit and acetone solvent permeation resistance as the PE bottle specimen, wherein no clearly formed NYC laminas but only dispersed NYC droplets or agglomerates were found on the fracture surfaces of the PE/NYC bottles. However, after blending optimum compositions of MPANYC in PE, the PE/MPANYC bottles with demarcated MPANYC laminas exhibit significantly better white spirit and acetone permeation resistance than the PE/MPA bottle, wherein the white spirit and acetone permeation rates of the PE/MPA8NYC1 bottle are about 1.3 and 1.4 times slower than those of the PE/MPA bottle, respectively. In order to understand these interesting barrier properties of PE/MPANYC and PE/NYC bottles, rheological, thermal, wide angle X-ray diffraction and morphological properties of the base MPANYC and NYC resins and their corresponding morphology present in the blow-molded bottles were investigated. 相似文献
986.
This paper addresses the problem of designing controllers that are robust to a great uncertainty in a time constant of the plant. Plants must be represented by minimum phase rational transfer functions of an arbitrary order. The design specifications are: (1) a phase margin for the nominal plant, (2) a gain crossover frequency for the nominal plant, (3) zero steady state error to step commands, and (4) a constant phase margin for all the possible values of the time constant (T): 0<T<∞. We propose a theorem that defines the structure of the set of controllers that fulfil these specifications and show that it is necessary for these robust controllers to include a fractional-order PI term. Examples are developed for both stable and unstable plants, and the results are compared with a standard PI controller and a robust controller designed using the QFT methodology. 相似文献
987.
CHARACTERIZATION OF EVA-BASED ADHESIVES CONTAINING DIFFERENT AMOUNTS OF ROSIN ESTER OR POLYTERPENE TACKIFIER 总被引:1,自引:0,他引:1
Marí a Luisa Barrueso-Martí nez Teresa del Pilar Ferr ndiz-G mez Marí a Dolores Romero-S nchez Jos Miguel Martí n-Martí nez 《The Journal of Adhesion》2003,79(8):805-824
Different amounts (50-170 php--parts per hundred parts of EVA, 33-63 wt%) of two tackifiers (hydrogenated rosin ester, polyterpene resin) were added to an ethylene vinyl acetate (EVA) copolymer containing 28 wt% vinyl acetate. The EVA and the tackifier were characterized using infrared (IR) spectroscopy, DSC measurements, and stress-controlled plate-plate rheology. The properties and compatibility of the EVA-tackifier mixtures were studied using DSC, DMTA, and stress-controlled plate-plate rheology. Immediate adhesion was measured as a quantification of tack, and the T-peel strength of roughened styrene-butadiene rubber/EVA-tackifier adhesive joints was also obtained. The increase in the amount of tackifier noticeably changed the crystallinity of polyethylene blocks in the EVA, and the temperature at the cross-over between the curves of the storage and loss moduli as a function of the temperature was displaced to a lower value. Whereas the hydrogenated rosin ester was compatible with the amorphous ethylene vinyl acetate copolymer regions of the EVA (Tg value increased) reducing its crystallinity, the polyterpene resin was compatible with the polyethylene blocks of the EVA (T g value was not modified), increasing its crystallinity. Immediate adhesion of the EVA-tackifier mixtures was improved by adding both hydrogenated rosin ester and polyterpene tackifiers. On the other hand, there was an optimum tackifier content at which the maximum T-peel strength value was obtained. 相似文献
988.
989.
H_5N_1亚型禽流感病毒血凝素基因的克隆及分子进化分析 总被引:1,自引:0,他引:1
目的 克隆H5N1 亚型禽流感病毒HA基因并进行分子进化分析。方法 应用RT PCR方法 ,以 2株H5N1 亚型禽流感病毒RNA为模板 ,扩增了HA全基因cDNA。将HAcDNA基因克隆于pUCm T载体 ,并对其进行了测序。结果 所克隆的HA基因全长为 1731bp ,共编码 5 6 8个氨基酸。将该毒株与其它 10株H5亚型禽流感病毒HA基因序列核苷酸及氨基酸进行比较 ,其核苷酸同源性在 80 5 %~ 99 2 %之间 ,氨基酸序列同源性在 89 4 %~98 6 %之间。高致病性毒株HA基因裂解位点存在多个碱性氨基酸插入。结论 为禽流感基因工程疫苗的研制奠定了基础 ,同时通过分子进化分析也揭示了各毒株间的亲缘关系。 相似文献
990.
The application of supercritical fluid chromatography (SFC) coupled with a UV variable-wavelength detector to isolate the
minor components (carotenes, vitamin E, sterols, and squalene) in crude palm oil (CPO) and the residual oil from palm-pressed
fiber is reported. SFC is a good technique for the isolation and analysis of these compounds from the sources mentioned. The
carotenes, vitamin E, sterols, and squalene were isolated in less than 20 min. The individual vitamin E isomers present in
palm oil were also isolated into their respective components, α-tocopherol, α-tocotrienol, γ-tocopherol, γ-tocotrienol, and
δ-tocotrienol. Calibration of all the minor components of palm as well as the individual components of palm vitamin E was
carried out and was found to be comparable to those analyzed by other established analytical methods. 相似文献