东非的能源困境

东非存在着的慢性能源问题由于该地区目前的干旱和电力减产而更加凸显了出来。为应对这一问题，乌干达、坦桑尼亚、肯尼亚和卢旺达的能源部长正在考虑作出战略选择以极大地扩展该地区获得能源服务的渠道。他们已请求联合国开发署帮助他们制定出一个地区能源战略。各国部长们于2005年8月草签了一份框架草案，并要求东非共同体秘书处负责协调该草案进一步的制定与实施。     

High-Temperature Vapor Phase Lubrication Using Carbonaceous Gases

Following the pioneering work of Prof. James Lauer, the ability to provide continuous solid lubrication through vapor phase delivery of carbonaceous gases has been successfully demonstrated on a pin-on-disk contact at the temperatures of 650 °C. Results from tribological experiments under 2 N normal load and 50 mm/s sliding speed showed an over 20× reduction in friction coefficient. The samples were silicon nitride (pin) versus CMSX-4 (disk) and the experiments when run in a nitrogen environment with acetylene admixtures. Two repeat experiments gave average friction coefficients of μ = 0.03 and μ = 0.02. The process was robust and provided low friction for the entire 500 m of sliding. Using focused ion-beam milling, high-resolution transmission electron microscopy, and confocal Raman spectroscopy, the resulting solid lubricant was found to be oriented microcrystalline graphite.     

Measured Performance of a Highly Preloaded Three-Lobe Journal Bearing–-Part II: Dynamic Characteristics

The dynamic coefficients of a three-lobe bearing with a preload factor of 0.75 were determined. Principal and cross-coupled stiffness and damping coefficients were derived from measured responses to forced harmonic excitation. Three operating speeds were tested and, for each speed, the load was varied so that the Sommerfeld number ranged from 0.23 to 2.87. Three orbits were used for each test condition, which resulted in three data points for each condition. At each condition the nominal data points fell within the uncertainties of the data. Non-dimensionalized data at all three speeds were independent of any given Sommerfeld number; thus, the Reynolds number had little influence for the range of conditions tested. Data indicated that minimization of the uncertainties is possible with optimal orbit selection.     

Enhancement of magnetic texture and functional characteristics of iron-based soft magnetic alloys

It has been shown that the formation of nitride-oxide magnetically active electrically insulating coatings on ribbons of iron-based soft magnetic alloys using the method of ion-plasma deposition and subsequent magnetic annealing in an ac magnetic field leads to a substantial improvement of their static and dynamic magnetic properties.     

Down-selection and optimization of thermal-sprayed coatings for aluminum mould tool protection and upgrade

This article details the down-selection procedure for thermally sprayed coatings for aluminum injection mould tooling. A down-selection metric was used to rank a wide range of coatings. A range of high-velocity oxyfuel (HVOF) and atmospheric plasma spray (APS) systems was used to identify the optimal coating-process-system combinations. Three coatings were identified as suitable for further study; two CrC NiCr materials and one Fe Ni Cr alloy. No APS-deposited coatings were suitable for the intended application due to poor substrate adhesion (SA) and very high surface roughness (SR). The DJ2700 deposited coating properties were inferior to the coatings deposited using other HVOF systems and thus a Taguchi L18 five parameter, three-level optimization was used to optimize SA of CRC-1 and FE-1. Significant mean increases in bond strength were achieved (147±30% for FE-1 [58±4 MPa] and 12±1% for CRC-1 [67±5 MPa]). An analysis of variance (ANOVA) indicated that the coating bond strengths were primarily dependent on powder flow rate and propane gas flow rate, and also secondarily dependent on spray distance. The optimal deposition parameters identified were: (CRC-1/FE-1) O₂ 264/264 standard liters per minute (SLPM); C₃H₈ 62/73 SLPM; air 332/311 SLPM; feed rate 30/28 g/min; and spray distance 150/206 mm.     

Processing of ZrC–Mo Cermets for High-Temperature Applications, Part I: Chemical Interactions in the ZrC–Mo System

The chemical compatibility of ZrC and Mo was investigated in carburizing and carbon-free environments at temperatures from 1700° to 2200°C. Heating in the carburizing atmosphere resulted in the complete reaction of Mo with C, while the carbon-free atmosphere resulted in retained metallic phase with a maximum of 13.8 mol% Mo₂C formed. The presence of Mo₂C was not detected at 2100°C in the carbon-free atmosphere, confirming the existing phase equilibria in the Zr–Mo–C system. Heat treatments in the carbon-free atmosphere also showed liquid formation at 2200°C, as evident from microstructure analysis. Liquid formation was consistent with the interaction between Mo and Mo₂C. The liquid was found to comprise at least 7 vol% of the total component, based on a phase diagram for the Mo–C system. The formation of a liquid should allow for the processing of ZrC–Mo cermets by liquid-phase pressureless sintering.     

Functional mesoporous carbon built from the 1,10-phenanthroline building block: A new class of catalyst support

A simple synthesis of a high surface area catalyst support composed of a nanoporous carbon architecture built from a 1,10-phenanthroline precursor is described.     

Structure-activity relationships for a family of benzothiophene selective estrogen receptor modulators including raloxifene and arzoxifene

The search for the "ideal" selective estrogen receptor modulator (SERM) as a substitute for hormone replacement therapy (HRT) or use in cancer chemoprevention has focused on optimization of estrogen receptor (ER) ligand binding. Based on the clinical and preclinical benzothiophene SERMs, raloxifene and arzoxifene, a family of SERMs has been developed to modulate activity and oxidative lability. Antiestrogenic potency measured in human endometrial and breast cancer cells, and ER ligand binding data were correlated and seen to provide a guide to SERM design only when viewed in toto. The in vitro studies were extended to the juvenile rat model, in which the desired antiestrogenic profile and putative cardiovascular benefits of SERMs were observed.     

Alginate‐coated chitosan membrane for guided tissue regeneration

Chitosan membranes were first prepared by a thermally induced phase separation method and then alginate was coated on one side of the membranes by a modified dialysis apparatus to prepare alginate/chitosan membranes (A/C membranes). Electron spectroscopy for chemical analysis (ESCA), scanning electron microscope, and contact angle measurements were conducted to evaluate the surface characteristics. The mechanical strength, degradation behavior, and cell adhesion test were performed to evaluate the feasibility of using A/C membrane in guided tissue regeneration applications. The results revealed that alginates could effectively be coated onto the chitosan membrane. As observed in ESCA results, the N‐atomic emission peak was decreased from originally 6.2% on the untreated chitosan surface to 2% on the alginate‐treated surface. The contact angle decreased on the alginate‐modified side substantially, compared with the untreated side (from 88.4° to 34.2°). The A/C membrane had a higher water content of 71.8% in comparison to the chitosan membrane of 61.8%. Consequently, A/C membrane became stiffer and had a higher Young's modulus and strength. After a 30‐day in vitro shaking test, the weight of membranes was degraded to about 75% from the original. The 3T3 fibroblast cells showed less adhesion to alginate‐modified side as compared to the untreated chitosan‐side in cell adhesion test. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4528–4534, 2006     

Computer model of a bovine type I collagen microfibril

Collagens are a family of structural proteins of the extracellularmatrix. The fibril-forming collagens are the major structuralproteins of skin, cartilage, bone, blood vessel walls and internalorgans. In addition to biological function, the collagens providenatural structural frameworks that are utilized in the medical,food and leather industries. Many schemes for the organizationof type I collagen into triple helices, microfibrils and fibrilshave been proposed during the past 30 years. Here, the developmentof a molecular model of a bovine type I collagen ‘Smith’microfibril is described. In cross-section, this model exhibitsa symmetrical, pentagonal grouping of five triple helices. Themodel comprises 15 polypeptide chains having 315 residues each.This model is large enough to allow a comparison of its grossstructural features with images of stained collagen obtainedby electron microscopy, yet small enough to be manipulated ona minicomputer or work-station. The model is useful for (amongothers) studies of structure-function relationships in collagen,exploring folding pathways, predicting the efficacy of potentialcrosslinking agents or chemical modifications, and designingsynthetic collagen-like materials or modifications for specificapplications.