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排序方式: 共有120条查询结果,搜索用时 31 毫秒
81.
Paulo de Tarso G Leopoldo J Xavier-Filho Maria S Lima 《Journal of the science of food and agriculture》1994,65(2):179-183
A column of chitin was utilized to separate four lectins (hemagglutinating activity) from the seeds of (Lablab purpureus L) Sweet. Two of these activities, which were bound by chitin and were also strongly inhibited by N-aeetyl-D -glucosamine, were differentiated according to their ionic properties: one is a basic (C2-S1) and the other is an acidic (C2-S2) lectin. A third N-acetyl-D -glucosamine binding lectin (Cl-2) is also acidic in nature but showed a lower binding capacity towards this sugar than C2-S2. A fourth lectin (C1-1S2) was strongly inhibited by galactose and has an acidic character. The lectin is formed by subunits of 39000 and 44000 kDa. 相似文献
82.
In this study, we examine the scientific output of Brazilian psychiatry, based on the databaseof the Institute for Scientific Information (ISI), publications in the 10 most important psychiatricjournals, and publications in major Brazilian journals. The number of Brazilian publications (i.e.,those carrying at least one Brazilian address) in psychiatry in the ISI database increased by 168%during the 15-year period under study (1981-1995) . Despite this growth, the relative contributionof publications in psychiatry to the country's publications in medical sciences did not change overthe 15-year period. This fraction, around 2%, remained at less than one-third of the averagecontribution of psychiatry journals to publications in medicine worldwide. The impact inferredfrom number of citations (1981-1992) shows that Brazilian articles in psychiatry were cited lessthan the world average in this field. In the 10 psychiatry journals with the highest impact,Brazilian authors published only 48 articles in the 1981-1995 period, representing only 0.2% ofthe articles in those journals. Like their American and British counterparts, Brazilian psychiatristsalso published primarily in domestic journals: 87.1% of the publications by Brazilians appeared inthe two major Brazilian psychiatric journals, compared with only 12.9% in foreign journals.Among publications in psychiatry in the ISI database, the number of articles co-authored byBrazilians with scientists from other countries increased 12.3 fold from 1981-1985 to 1991-1995,representing at the end 50% of all publications by Brazilian psychiatrists in international journals.Despite all cuts in funding for Brazilian science during the last decades, all of the articles in oursample originated in public universities, and only 10 universities were responsible for 70% of thepublications by Brazilian psychiatrists in our survey period. We conclude that Brazilianpsychiatric research is a subject worthy of particular concern, especially if we take into accountthe country's modest scientific performance and the socio-economic consequences of mentaldisorders in the Brazilian population. 相似文献
83.
Mauricio Alférez Rodrigo Bonifácio Leopoldo Teixeira Paola Accioly Uirá Kulesza Ana Moreira João Araújo Paulo Borba 《Requirements Engineering》2014,19(4):355-376
Software product lines (SPL) provide support for productivity gains through systematic reuse. Among the various quality attributes supporting these goals, modularity, stability and expressiveness of feature specifications, their composition and configuration knowledge emerge as strategic values in modern software development paradigms. This paper presents a metric-based evaluation aiming at assessing how well the chosen qualities are supported by scenario-based SPL requirements approaches. The selected approaches for this study span from type of notation (textual or graphical based), style to support variability (annotation or composition based), and specification expressiveness. They are compared using the metrics developed in a set of releases from an exemplar case study. Our major findings indicate that composition-based approaches have greater potential to support modularity and stability, and that quantification mechanisms simplify and increase expressiveness of configuration knowledge and composition specifications. 相似文献
84.
The combustion of a char in the 41 mm ID riser of a laboratory circulating fluidized bed combustor has been investigated at different air excesses and rates of solids (char and sand) circulating in the loop. Riser performance was characterized by an axial oxygen concentration profile as well as by the overall carbon content and particle size distribution. The proposed model accounts for carbon surface reaction, intraparticle and external diffusion, and attrition. External diffusion effects were relevant in the riser dense region where char was potentially entrapped in large clusters of inert solids. Experimental data and results of the model calculations are in satisfactory agreement. 相似文献
85.
Nymphs ofTriatoma infestans andTriatoma mazzottii are weakly attracted to their feces and to extracts of feces in polar solvents, but not to nonpolar solvent extracts. The major volatile compounds identified in feces by solvent extraction and thermal desorption wereo-aminoacetophenone, 4-methylquinazoline, and 2,4-dimethylquinazoline, but these showed no attractant activity at a range of concentrations. Choice tests with a moving current of air gave no positive reaction to feces, extracts, or pure compounds. 相似文献
86.
Lucia Catabriga Alvaro L. G. A. Coutinho Leopoldo P. Franca 《International journal for numerical methods in engineering》2004,60(9):1513-1534
In this work we evaluate the performance of the left conjugate direction method recently introduced by Yuan, Golub, Plemmons and Cecílio for the solution of non‐symmetric systems of linear equations arising from the implicit semi‐discrete SUPG finite element formulation of advective–diffusive and inviscid compressible flows. We extend the original algorithm to accommodate restarts and typical element‐by‐element preconditioners. We also show how to select the first left conjugate vector to start LCD. Several problems are solved, accessing performance parameters such as number of iterations, memory requirements and CPU times, and results are compared with other algorithms, such as GMRES, TFQMR and Bi‐CGSTAB. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
87.
Brazilian university-based science has grown rapidly in the last 20 years. Most of the PhD-level teaching, research, and technical
publications are based in the government-supported universities, although there are also privately supported universities,
which educate a large fraction of Brazilian attorney, business people, and other professions. We investigate here the relationship
between type of university, numbers of degree program offered, number of faculty members, and number of published papers.
Twelve universities, all government supported, are found to produce a very large fraction of publications and to house the
best qualified PhD programs. We find that there is a strong correlation between research carried out with foreign collaborators
and rate at which the resulting publications are cited. This trend is characteristic of many developing and less developed
nations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
88.
Gutiérrez-Sánchez PE Hernández-León A Villafuerte-Robles L 《Drug development and industrial pharmacy》2008,34(2):171-180
The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO2 bubbles, and the matrix volume expansion produced after addition of SB. 相似文献
89.
Esther Andrés-Pérez Daniel González-Juárez Mario J. Martin-Burgos Leopoldo Carro-Calvo Sancho Salcedo-Sanz 《工程优选》2017,49(2):181-198
Surrogate-based optimization (SBO) has recently found widespread use in aerodynamic shape design owing to its promising potential to speed up the whole process by the use of a low-cost objective function evaluation, to reduce the required number of expensive computational fluid dynamics simulations. However, the application of these SBO methods for industrial configurations still faces several challenges. The most crucial challenge nowadays is the ‘curse of dimensionality’, the ability of surrogates to handle a high number of design parameters. This article presents an application study on how the number and location of design variables may affect the surrogate-based design process and aims to draw conclusions on their ability to provide optimal shapes in an efficient manner. To do so, an optimization framework based on the combined use of a surrogate modelling technique (support vector machines for regression), an evolutionary algorithm and a volumetric non-uniform rational B-splines parameterization are applied to the shape optimization of a two-dimensional aerofoil (RAE 2822) and a three-dimensional wing (DPW) in transonic flow conditions. 相似文献
90.
R Perrone F Berardi NA Colabufo M Leopoldo V Tortorella 《Canadian Metallurgical Quarterly》1998,41(24):4903-4909
A series of new 1-aryl-4-alkylpiperazines containing a terminal benzamide fragment or a tetralin-1-yl nucleus on the alkyl chain were synthesized and tested for binding at cloned human dopamine D4 and D2 receptor subtypes. A SAFIR (structure-affinity relationship) study on this series is herein discussed. The most relevant D4 receptor affinities were displayed by N-[omega-[4-arylpiperazin-1-yl]alkyl]-methoxybenzamides (compounds 5, 16-20), their IC50 values ranging between 0.057 and 7.8 nM. Among these, N-[2-[4-(4-chlorophenyl)piperazin-1-yl]ethyl]-3-methoxybenzamide (17) emerged since it exhibited very high affinity for dopamine D4 receptor (IC50 = 0.057 nM) with selectivity of >10 000 for the D4 versus the D2 receptor; compound 17 was also selective versus serotonin 5-HT1A and adrenergic alpha1 receptors. 相似文献