153,739 research outputs found
Effect of thermally aged oil on space charge dynamics in oil/paper insulation system
No full textThe formation of space charge in oil/paper insulation system can lead to material degradation in the high electrical field region and affect system reliability. Therefore, it is important to understand factors that affect space charge formation in oil/paper insulation system. In the present study the effect of thermally aged oil on space charge dynamics in oil/paper insulation system has been investigated using the pulsed electroacoustic (PEA) technique under different dc electrical fields at room temperature. The condition of oil was characterised. The ultraviolet/visible (UV/Vis) spectrum of oil shifts to visible wavelength and the oil acidity increased as the ageing time increased. It has been found that oil property has a significant effect on the space charge distribution of oil/paper insulation system. The more the deterioration of the oil and the higher the applied voltage, the larger the amount of negative charge injected into the paper near to the cathode and the positive charge accumulated at the paperpaper interface near to the cathode. The maximum electric field strength for oil/paper sample with seriously aged oil under 4kV and 6kV is more than 20% higher than its average electric field strength
DIETARY CONDITIONS AND DIFFERENTIAL ACCESS TO FOOD RESOURCES AMONG THE VARIOUS CLASSES DURING THE HAN PERIOD
Full text linkIn this thesis, I study how food resources and dietary conditions were determined by social and economic status during the Han period in China, B.C. 206~A.D.220. Even though earlier scholars have published research concerning the Chinese food culture of this period, these studies were limited in that they only illustrated the dietary culture of the upper class or the available food resources in one geographic area. Also, without any persuasive data, it has been assumed by these earlier scholars that there were big differences in food resources and food consumption between the upper and lower classes. In this thesis, for comparison among the classes, I divide the social and economic classes into five stratified groups: nobles, officials, peasants, soldiers and convicts. After a brief introduction of the nature of each social class, I examine the food resources and nutritional condition of each group using information such as the wealth and income of each group, the market price of food resources, the agricultural products of peasants, and the amount of food distribution to soldiers and convicts. I found these data from archaeological remains, received historical records and pictorial data, and excavated texts. This research shows a broader view of Chinese dietary condition focusing not only on the variety of food resources of nobles, but also on the different food accessibilities among the officials, and the food deficiencies of peasants. It also deals with the situations of food supply for soldiers and convicts in an effort to reveal the true dietary consumption and nutritional conditions for all Chinese. This research proves that the various classes during the Han period in China had different food resources and dietary conditions
Deletion of vitamin D receptor leads to premature emphysema/COPD by increased matrix metalloproteinases and lymphoid aggregates formation
Full text linkDeficiency of vitamin D is associated with accelerated decline in lung function. Vitamin D is a ligand for nuclear hormone vitamin D receptor (VDR), and upon binding it modulates various cellular functions. The level of VDR is reduced in lungs of patients with chronic obstructive pulmonary disease (COPD) which led us to hypothesize that deficiency of VDR leads to significant alterations in lung phenotype that are characteristics of COPD/emphysema associated with increased inflammatory response. We found that VDR knock-out (VDR(-/-)) mice had increased influx of inflammatory cells, phospho-acetylation of nuclear factor-kappaB (NF-κB) associated with increased proinflammatory mediators, and up-regulation of matrix metalloproteinases (MMPs) MMP-2, MMP-9, and MMP-12 in the lung. This was associated with emphysema and decline in lung function associated with lymphoid aggregates formation compared to WT mice. These findings suggest that deficiency of VDR in mouse lung can lead to an early onset of emphysema/COPD because of chronic inflammation, immune dysregulation, and lung destruction
MeSH term explosion and author rank improve expert recommendations
Full text linkInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
Full text linkBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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