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排序方式: 共有172条查询结果,搜索用时 46 毫秒
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Chao AC Ziadeh BI Diau GY Wijendran V Sarkadi-Nagy E Hsieh AT Nathanielsz PW Brenna JT 《Lipids》2003,38(4):425-429
One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant,
dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA)
on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one
of four groups: breast-fed (B), term formula-fed (T−), preterm formulafed (P−), and preterm fed formula supplemented with DHA-AA (P+). Breast milk contained 0.68%wt DHA and the P+ group formula contained 0.61%wt DHA. In the preterm groups (P− and P+), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested,
and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found
among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented
groups, but not compared with the P+ group. The B and P+ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P−) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0
or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant
lipid concentration in preterm neonate lungs. 相似文献
3.
The popularity of distance education has grown rapidly over the last decade in Taiwan’s higher education, yet many fundamental teaching–learning issues are still in debate. While teacher–student interaction is a key success factor in distance education, little work has been done on the teachers. The intent of this research was to clarify teacher’s perceptions on key distance education issues and to develop a discernible typology of different groups of teachers based on their perceptions. Because there may be a gulf between teachers and the technology used in distance education, the target of this study was teachers in information related departments in Taiwan’s colleges, who were more familiar with current technology. Factor analysis and cluster analysis were used to derive the typology. Five higher-level issue constructs emerged from the factor analysis: learning effect, customization, administrative challenges, geographic and resource integration, and instructional design challenges. Four groups of teachers, namely the skeptics, the optimists, the mild-promising group, and the outlier, were identified using cluster analysis of teachers’ perceptions on these five higher-level issue constructs. The profiles of the four groups of teachers were summarized and implications were discussed, which should provide useful insights to the policy makers of higher education on distance education decisions. 相似文献
4.
The hot-working characteristics of wrought Co-Ni-Cr-Mo implant alloy during ingot-to-billet conversion were evaluated using a Gleeble-2000A simulator. The hot tensile test at 700–1 320 °C was used to determine the optimum hot-working parameters at a strain rate equivalent to that of conventional press forging to ensure acceptable hot workability. Hot ductility and deformation resistance as a function of temperature can be clearly established. The fracture surfaces of the tensile specimens were examined to correlate them with the hot tensile ductility values at various temperatures. The poor ductility at temperatures above 1300 °C was attributed to the incipient melting of grain boundaries. The effect of temperature and strain rate on the flow-stress behaviour and microstructures were investigated by uniaxial compression testing in the temperature range 900–1200 °C and strain rate, , range of 0.01–10s–1. The strain-hardening and steady-state behaviour were described from the measured true stress-true strain curves. 相似文献
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This study aims to propose an algorithm for traffic estimation, particularly for urban roadway sections with insufficient data sources. Establishing an advanced traffic management system (ATMS) heavily depends on obtaining complete data. In this regard, traffic detectors play an important role in data acquisition. However, installing traffic detectors extensively over a metropolitan area can be rather expensive. As such, in most cities around the world, vehicle detectors for traffic data collection are relatively insufficient to meet requirements. In light of this, the current research therefore proposes a feasible algorithm of dynamic section flow prediction based on the automatic control theory and observer design for roadway sections with insufficient data sources. According to the numerical evaluation, the method is found to be satisfactory and acceptable in practice. 相似文献
8.
Shenting Liu Jiang Wu Peng Yu Qinghua Ding Zhihua Zhou Handong Li Chih-chung Lai Yu-Lun Chueh Zhiming M Wang 《Nanoscale research letters》2014,9(1):549
Earth-abundant iron pyrite (FeS2) shows great potential as a light absorber for solar cells and photodetectors due to their high absorption coefficient (>105 cm-1). In this paper, high-quality phase-pure and single crystalline pyrite nanocrystals were synthesized via facile, low-cost, and environment friendly hydrothermal method. The molar ratio of sulphur to iron and the reaction time play a crucial role in determining the quality and morphology of FeS2 nanocrystals. X-ray diffraction and high-resolution transmission electron microscopy confirm that phase-pure and single crystalline pyrite nanocrystals can be synthesized with high sulphur to iron molar ratio and sufficient reaction time. For the first time, a crystalline nanogap pyrite photodetector with promising photocurrent and UV-visible photoresponse has been fabricated. This work further demonstrates a facile route to synthesize high-quality FeS2 nanomaterials and their potential in optoelectronic applications. 相似文献
9.
Fluoro‐Substituted n‐Type Conjugated Polymers for Additive‐Free All‐Polymer Bulk Heterojunction Solar Cells with High Power Conversion Efficiency of 6.71%
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10.
Li-Chih Wang Allen Wang Chun-Ya Chueh 《The International Journal of Advanced Manufacturing Technology》2018,98(1-4):37-45
Micro-machining has gained increased application to produce miniaturized parts in various industries. However, the uncut chip thickness in micro-machining is comparable to cutting edge radius. The relationship between the cutting edge radius and uncut chip thickness has been a subject matter of increasing interest. The acoustic emission (AE) signal can reflect the stress wave caused by the sudden release of the energy of the deformed materials. To improve the precision of machining system, determination of the minimum uncut chip thickness was investigated in this paper. The AE signal generated during micro-cutting experiments was used to analyze the chip formation in micro-end milling of Inconel 718. The finite element method (FEM) simulation was used to analyze the results of the experiments. The results showed that the cutting tool geometry and material properties affected the minimum uncut chip thickness. The estimation of the minimum uncut chip thickness based on AE signals can produce quite satisfactory results. The research on the minimum uncut chip thickness can provide theoretical basis for analysis of surface quality and optimal choice of cutting parameters. 相似文献