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排序方式: 共有151条查询结果,搜索用时 15 毫秒
1.
A Nobrega A Grandien M Haury L Hecker E Malanchère A Coutinho 《Canadian Metallurgical Quarterly》1998,28(4):1204-1215
Our objective was to determine the effect of level and chemical form of dietary selenium on productivity of beef cows, concentrations of triiodothyronine (T3), and thyroxine (T4) in plasma, and immunoglobulins (IgG and IgM) in plasma and colostrum of cows. Pregnant cows (n = 60) were randomly allocated among four dietary treatments of 20, 60, or 120 ppm Se as selenite and 60 ppm as selenomethionine from selenized yeast (SeY) in salts offered free-choice. Treatments began 90 d prepartum and continued through the second parturition. Treatments did not affect the final body weights of cows or birth weights or weaning weights of calves. At parturition, cows given salt with 20 ppm Se as selenite had lower (P < . 05) concentrations of Se in blood than cows with access to higher-Se salts. Treatments affected (P < .01) the concentration of T3 and the ratio of T3:T4 in plasma of cows. The concentration of T3 in plasma of cows with access to salt with 20 ppm Se was 14% lower than that in cows supplemented with 60 ppm Se as selenite or SeY. Plasma IgG in cows and calves, colostrum, and Se concentrations in colostrum, casein, and whey were lowest (P < .01) for cows given salt with only 20 ppm Se. Thus, salts with concentrations of 60 and 120 ppm Se improved measures of Se status in cows and calves. Consideration should be given to the concentrations of T3 and IgG when determining the nutritional requirements for Se in cattle. 相似文献
2.
Anna Raffaela de Matos Costa Juliana Cysneiros Lima Raquel dos Santos Lhaira Souza Barreto Mariana Alves Henrique Laura Hecker de Carvalho Yêda Medeiros Bastos de Almeida 《应用聚合物科学杂志》2021,138(36):50916
This work deals with the rheological, morphological, and thermal properties of composites having poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and their blends as matrices, and rice husk ash (RHA) as a filler. The study determines the effect of composition on the change in viscosity and rate of degradation during processing in a torque rheometer. Our data indicates that thermal stability and degradation during processing depend on matrix composition and filler concentration. SEM micrographs show both partial adhesion of the filler to the matrices and filler pullout. Optical microscopy shows particle agglomeration and that agglomerate size increased with filler content. FTIR investigates the shifting of absorption bands of PET/PA6 composite after the addition of RHA and attributes the selective dispersion of RHA to the formation of hydrogen bonds. Our data supports the idea that filler employed here is an option to develop polymer composites with improved properties. 相似文献
3.
Privacy is becoming increasingly important due to the advent of e-commerce. E-commerce applications frequently require customers to divulge many personal details about themselves that must be protected carefully in accordance with privacy principles and regulations. Here, the authors define a privacy ontology to support the provision of privacy and help derive the level of privacy associated with e-commerce transactions and applications. The privacy ontology provides a framework against which e-commerce sites can benchmark their privacy policies and implementations. 相似文献
4.
Plant species discrimination using remote sensing is generally limited by the similarity of their reflectance spectra in the visible, NIR and SWIR domains. Laboratory measured emissivity spectra in the mid infrared (MIR; 2.5 μm–6 μm) and the thermal infrared (TIR; 8 μm–14 μm) domain of different plant species, however, reveal significant differences. It is anticipated that with the advances in airborne and space borne hyperspectral thermal sensors, differentiation between plant species may improve. The laboratory emissivity spectra of thirteen common broad leaved species, comprising 3024 spectral bands in the MIR and TIR, were analyzed. For each wavelength the differences between the species were tested for significance using the one way analysis of variance (ANOVA) with the post-hoc Tukey HSD test. The emissivity spectra of the analyzed species were found to be statistically different at various wavebands. Subsequently, six spectral bands were selected (based on the histogram of separable pairs of species for each waveband) to quantify the separability between each species pair based on the Jefferies Matusita (JM) distance. Out of 78 combinations, 76 pairs had a significantly different JM distance. This means that careful selection of hyperspectral bands in the MIR and TIR (2.5 μm–14 μm) results in reliable species discrimination. 相似文献
5.
War is a complex social situation due to the interplay of multiple factors. Economical and political ones are of utmost importance, but human attitudes and motivations must be also taken into account. Being desirable to modify human transactions in such a way that they do not interfere with the basic right of everyone to a condition of physical and mental well-being, war must be abolished. The author contends that an understanding of behaviour through Psychology can be helpful in that aim. Aggression is considered the principal psychological cause of war. It is worth while to differentiate between aggression as an instrument for attaining a special end, and as pure hostility. Only in the first form, it is held here, does it play an important role in war. Psychogists must deal also with a wide range of states of mind that can be "served" by aggression: feelings of inferiority or insecurity, fear, greed, projections, compensations, rationalizations, etc. Scientific approach is not the only one Physiology brings to war prevention. It is equally important the wide dissemination of its conclusions among the general public. Information on the dynamics that prompt people to decide war would make it easier to control. This applies not only to political or military leaders, but also to civil populations. Concerning those two possible contributions of psychologists, scientific and educative, it is suggested the extensive use of psychodramatic techniques. Their richness lie in the lifelike experiences they convey to the participants, and particular aptitude to promote changes of attitudes. Investigation and information on the psychological processes related to war should be undertaken by international organizations of social scientists, acting simultaneously in several countries. Some of the initial steps they could further: 1) that prevention of war be a current subject matter in psychological courses; 2) that the World Health Organization take interest in this subject; 3) that psychologists participate in international political and economical bodies in order to clarify the psychological factors leading to war. 相似文献
6.
The performance of older adults and depressed people on linear order reasoning is hypothesized to be best explained by different theoretical models. Whereas depressed younger adults are found to be impaired in generative inference making, older adults are well capable of making such inferences but exhibit problems with working memory (Experiments 1 and 2). Restriction of the available study time impairs reasoning by nondepressed control participants and. as such, proves to be a good model of older adults' but not depressed participants' limitations (Experiment 3). These results are replicated comparing depressed and older participants with a control group in the same study, providing increased power and linking the results to additional control measures of processing speed and working memory (Experiment 4). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Carl-Mattheis Wahl Constanze Schmidt Markus Hecker Nina D. Ullrich 《International journal of molecular sciences》2022,23(17)
Gap junctions and their expression pattern are essential to robust function of intercellular communication and electrical propagation in cardiomyocytes. In healthy myocytes, the main cardiac gap junction protein connexin-43 (Cx43) is located at the intercalated disc providing a clear direction of signal spreading across the cardiac tissue. Dislocation of Cx43 to lateral membranes has been detected in numerous cardiac diseases leading to slowed conduction and high propensity for the development of arrhythmias. At the cellular level, arrhythmogenic diseases are associated with elevated levels of oxidative distress and gap junction remodeling affecting especially the amount and sarcolemmal distribution of Cx43 expression. So far, a mechanistic link between sustained oxidative distress and altered Cx43 expression has not yet been identified. Here, we propose a novel cell model based on murine induced-pluripotent stem cell-derived cardiomyocytes to investigate subcellular signaling pathways linking cardiomyocyte distress with gap junction remodeling. We tested the new hypothesis that chronic distress, induced by rapid pacing, leads to increased reactive oxygen species, which promotes expression of a micro-RNA, miR-1, specific for the control of Cx43. Our data demonstrate that Cx43 expression is highly sensitive to oxidative distress, leading to reduced expression. This effect can be efficiently prevented by the glutathione peroxidase mimetic ebselen. Moreover, Cx43 expression is tightly regulated by miR-1, which is activated by tachypacing-induced oxidative distress. In light of the high arrhythmogenic potential of altered Cx43 expression, we propose miR-1 as a novel target for pharmacological interventions to prevent the maladaptive remodeling processes during chronic distress in the heart. 相似文献
8.
C. Kuenzer C. Hecker J. Zhang S. Wessling W. Wagner 《International journal of remote sensing》2013,34(3):923-944
In this paper we present the results of our analyses of multidiurnal low‐resolution Moderate Resolution Imaging Spectroradiometer (MODIS) thermal data for coal fire‐related thermal anomaly detection. Results are presented for data of the Jharia coal mining region of India. We combine three relatively new approaches: first, we use low‐resolution MODIS data for coal fire area analyses, which has only been undertaken by a few authors. Second, we analyse data from four different times of day (morning, afternoon, evening and predawn) and for three different bands (MODIS bands 20, 32 and a ratio thereof); and third, we use an unbiased automated algorithm for thermal anomaly extraction of local thermal anomalies. The MODIS data analysed stem from the years 2001 and 2005. In 2001, MODIS data were only been available from the platform TERRA as morning and evening data (around 1030 and 2200 h). In 2005, MODIS data were available from this platform as well as from the platform AQUA as afternoon and predawn data (around 0130 and 0200 h). Our analyses indicate that MODIS multidiurnal data, and especially bands 20, 32 and ratio bands thereof, have a high potential for the detection of coal fire zones and coal fire hot spot zones, as well as for regular thermal monitoring activities. However, the data are not suitable for a quantitative coal fire analysis concerning fire outline, fire temperature or fire classification into surface and subsurface fires. We used higher‐resolution ASTER and LANDSAT data from 2005 and 2002 for general orientation and later comparison of thermal anomaly extraction results. We also used high‐resolution Quickbird data for the characterization of individual anomalous thermal clusters. Comparisons demonstrate that even low‐resolution thermal sensors such as MODIS can support coal fire detection and zonation into warm and very hot zones. 相似文献
9.
Torsion tests carried out to large plastic strains typically exhibit a leveling out (saturation) of the flow stress. On the other hand, saturation is usually not observed for other modes of deformation such as wire drawing or rolling. In iron and other body-centered cubic materials linear hardening persists to strains of . For face-centered cubic materials the behavior is mixed, with saturation not being achieved for most impure metals. We propose an explanation for the difference in flow stress at large strains between torsion and other modes of deformation. The explanation is based on Holt's dislocation cell wall formation theory and on the fact that apparently dislocations of only one Burgers vector are required to be active in torsion at large strains, whereas several are required for other deformation modes. Consequently, at the same dislocation density and applied stress level dislocations of opposite character but of the same kind are closer together in torsion. The dislocations have a stronger force of attraction between them and a faster rate of mutual annihilation through pipe diffusion controlled climb. The saturation stress is larger the larger is the number of different Burgers vectors of the dislocations involved in the deformation. Shear band instabilities are explained as a consequence of material locally reducing the number of active slip systems. 相似文献
10.
Siegfried S. Hecker 《Metallurgical and Materials Transactions A》1990,21(10):2617-2636
Summary The United States continues to depend heavily on science and technology for ensuring its defense needs, promoting human welfare,
and enhancing its economic competitiveness. I hope that my comments have helped to reinforce the point that we, as a nation,
must do a better job of leveraging the federal investment in R & D. I have used examples in materials science and engineering
to illustrate how this can be done, because materials science and engineering are crucial to our security and competitiveness,
as pointed out in the National Research Council’s report. I also took the liberty of telling you about the broad diversity
of the materials program at Los Alamos by picking my examples from Los Alamos’ work.
In closing, I recognize fully that what I have discussed today is only part of what is required to maintain national security
and enhance competitiveness. I believe that, first and foremost, we must get United States industry back into the lead. And
the United States government must address the macroeconomic issues and deal with the crisis in education as well. But I also
believe that Los Alamos can help in leveraging the federal R & D investment. 相似文献