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排序方式: 共有2198条查询结果,搜索用时 15 毫秒
91.
Juan P. Escobedo Ellen K. Cerreta Daniel T. Martinez Carl P. Trujillo Ricardo A. Lebensohn George T. Gray III 《Metallurgical and Materials Transactions A》2014,45(13):5877-5882
The influence of temperature on the dynamic tensile behavior of Zr has been investigated. Bullet-shaped Zr samples with two different textures were dynamically extruded at room temperature and 523 K (250 °C). A higher ductility was measured for samples deformed at elevated temperature as compared to those extruded at room temperature. This difference in ductility is discussed in terms of zirconium’s ability to accommodate plastic deformation via thermally enhanced slip activity, as evidenced by examination of the deformed microstructures. 相似文献
92.
ABSTRACT: BACKGROUND: Food and nutritional care quality must be assessed and scored, so as to improve health institution efficacy. This study aimed to detect and compare actions related to food and nutritional care quality in public and private hospitals. METHODS: Investigation of the Hospital Food and Nutrition Service (HFNS) of 37 hospitals by means of structured interviews assessing two quality control corpora, namely nutritional care quality (NCQ) and hospital food service quality (FSQ). HFNS was also evaluated with respect to human resources per hospital bed and per produced meal. RESULTS: Comparison between public and private institutions revealed that there was a statistically significant difference between the number of hospital beds per HFNS staff member (p = 0.02) and per dietitian (p < 0.01). The mean compliance with NCQ criteria in public and private institutions was 51.8% and 41.6%, respectively. The percentage of public and private health institutions in conformity with FSQ criteria was 42.4% and 49.1%, respectively. Most of the actions comprising each corpus, NCQ and FSQ, varied considerably between the two types of institution. NCQ was positively influenced by hospital type (general) and presence of a clinical dietitian. FSQ was affected by institution size: large and medium-sized hospitals were significantly better than small ones. CONCLUSIONS: Food and nutritional care in hospital is still incipient, and actions concerning both nutritional care and food service take place on an irregular basis. It is clear that the design of food and nutritional care in hospital indicators is mandatory, and that guidelines for the development of actions as well as qualification and assessment of nutritional care are urgent. 相似文献
93.
94.
Cenk Aktas Eva Dörrschuck Cathrin Schuh Marina Martinez Miró Juseok Lee Norbert Pütz Gunther Wennemuth Wolfgang Metzger Martin Oberringer Michael Veith Hashim Abdul-Khaliq 《Materials science & engineering. C, Materials for biological applications》2012,32(5):1017-1024
The effect of the micro- and nanotopography on vascular cell-surface interaction is investigated using nano- and microstructured Al2O3 as model substrate. Two different nanostructured Al2O3 surfaces composed of low density (LD) and high density (HD) nanowires (NWs) were synthesized by chemical vapour deposition (CVD) and commercially available microstructured Al2O3 plates were used for comparison. A clear diverging response of human umbilical vein endothelial cells (HUVEC) and human umbilical vein smooth muscle cells (HUVSMC) was observed on these nano- and microstructured surfaces. LD Al2O3 NWs seem to enhance the proliferation of HUVECs selectively. This selective control of the cell-surface interaction by topography may represent a key issue for the future stent material design. 相似文献
95.
B. Roy U. Martinez K. Loganathan A.K. Datye C.A. Leclerc 《International Journal of Hydrogen Energy》2012
The effect of preparation method on the performance of Ni/Al2O3 catalysts for aqueous-phase reforming of ethanol (EtOH) has been investigated. The first catalyst was prepared by a sol–gel (SG) method and for the second one the Al2O3 support was made by a solution combustion synthesis (SCS) route and then the metal was loaded by standard wet impregnation. The catalytic activity of these catalysts of different Ni loading was compared with a commercial Al2O3 supported Ni catalyst [CM (10%)] at different temperatures, pressures, feed flow rates, and feed concentrations. Based on the product distribution, the proposed reaction pathway is a mixture of dehydrogenation of EtOH to CH3CHO followed by C–C bond breaking to produce CO + CH4 and oxidation of CH3CHO to CH3COOH followed by decarbonylation to CO2 + CH4. CH4(C2H6 and C3H8) also can form via Fischer–Tropsch reactions of CO/CO2 with H2. The CH4 (C2H6 and C3H8) reacts to form hydrogen and carbon monoxide through steam reforming, while CO converts to CO2 mostly through the water–gas shift reaction (WGSR). SG catalysts showed poorer WGSR activity than the SCS catalysts. The activation energies for H2 and CO2 production were 153, 155 and 167 kJ/mol and 158, 160 and 169 kJ/mol for SCS (10%), SG (10%), and CM (10%) samples, respectively. 相似文献
96.
Metabolic engineering and adaptive evolution of Escherichia coli KO11 for ethanol production through the Entner–Doudoroff and the pentose phosphate pathways
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97.
It is widely accepted that biotechnology is a globally significant and growing research field. Because of its biodiversity, Colombia has a comparative advantage to innovate and commercialize biotechnological products and services. The aim of this study is to obtain a research profile and intellectual structure of the country in the biotechnology field by using bibliometric methods. These methods are needed to monitor the capacities and the compliance of national policies in biotechnology. By using records extracted from the ISI WoK database, this study describes the biotechnology publication trend, productivity and collaboration among institutions and countries, preferred journals, and the intellectual structure at the research subject area. Although, a growing trend in biotechnology publication was observed, the productivity is still low when compared to other countries in the region and the world. On the other hand, researchers seem to show a preference for international over domestic collaboration. The results suggest two elements: first, policy has not had the expected outcome in the short term, and second, a lack of internal collaboration could therefore reflect low endogenous capacities. The bibliometric methods used in this study can be applied to a wide range of research fields other than biotechnology. 相似文献
98.
Auger electron spectroscopy of Hg1?x Cd x Te has been investigated for quantitative analysis. HgCdTe is known to be a very sensitive material which easily suffers from ion beam and electron beam interactions. Two methods were compared for accurate and reproducible quantification of the chemical composition. The first strategy was to reduce as much as possible the damage caused by surface preparation and the effect of the incident electron beam on the material. Quantification was then achieved by use of relative sensitivity factors estimated by use of calibration reference samples. This method was rejected because of unavoidable beam damage which resulted in different chemical changes for the reference CdTe and the HgCdTe sample of interest. The second strategy was to precisely control the experimental conditions to ensure reproducible degradation. Quantification was achieved by analysis of reference HgCdTe samples with different Cd composition. Successful quantification was achieved on stoichiometric material of composition of 0.2 < X Cd < 0.3 with a X Cd discrimination limit of ΔX Cd = 0.02 and an analysis step of 10 nm. 相似文献
99.
J.O. ObielodanB.E. Stucker E. MartinezJ.L. Martinez D.H. HernandezD.A.Ramirez L.E. Murr 《Journal of Materials Processing Technology》2011,211(6):988-995
The interfacial bonding between layers in ultrasonically consolidated structures is poor for some material combinations, resulting in relatively low bond strength. This makes resultant parts unsuitable for structural applications. This work discusses a study of the effects of post process heat treatment of ultrasonically consolidated commercially pure titanium and aluminum alloy 3003 dual-material systems. The lap shear strengths of as-consolidated specimens as well as heat treated ones were tested. The results show that there is significant improvement of the strengths of post processed specimens over the as-consolidated ones. The improvement is as a result of stress relieving of the strain hardened interface between the two materials and some interactions of the base materials across the interfacial boundaries at elevated temperatures, leading to stronger bonds. The study highlights the role of post process heat treatments for improving the mechanical properties of ultrasonically consolidated structures. 相似文献
100.
Starch Consolidation Casting of Cordierite Precursor Mixtures—Rheological Behavior and Green Body Properties
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María Laura Sandoval Mariano H. Talou Analía G. Tomba Martinez María Andrea Camerucci Eva Gregorová Willi Pabst 《Journal of the American Ceramic Society》2015,98(10):3014-3021
The rheology of suspensions and mechanical properties of green bodies with cordierite composition (raw materials 37 wt% kaolin, 41 wt% talc, 22 wt% alumina, resulting in 46.6 wt% SiO2, 38.1 wt% Al2O3, 13.6 wt% MgO) and two types of starch (corn or potato) are investigated. Rotational viscometry of suspensions with solids loading 50, 60, and 70 wt% without starch showed that all tend to be shear‐thinning with a small degree of thixotropy. Suspensions with a total solids loading of 60 wt% with 25 wt% replaced by starch exhibited higher viscosity and thixotropy, but the viscometric behavior is almost identical for the two starch types (apparent viscosities 130–50 mPa ·s). Oscillatory rheometry shows that for suspensions with potato starch the onset temperature for gelatinization is 61°C–63°C, that is, lower than for corn starch (72°C–73°C). Maximum storage moduli and phase shift values after gelatinization are similar for both systems. The mechanical properties of green disks, measured via diametral compression tests, reveal clear differences between materials prepared with corn and potato starch, with the latter showing higher elastic modulus, higher strength, and higher deformation at fracture, obviously because of incompletely gelatinized starch granules in the green bodies prepared with corn starch . 相似文献