Cobalt powdersintering industry (stone cutting diamond wheels): a study of environmental-biological monitoring, workplace improvement and health surveillance

This communication deals with an aspect of occupational hygiene in a factory producing granite cutting diamond wheels by sintering, in moulds, of fine cobalt powder. The factory has been studied between 1988 and 1991; the Department of Preventive and Occupational Medicine of the Local Sanitary Unit of Reggio Emilia has followed the evolution of the local exhaust ventilation equipment supplied by the employer in that period. At the same time, the following measurements and observations were carried out: (a) cobalt exposure by personal sampling, (b) airborne cobalt measurements by area sampling, (c) biological monitoring of cobalt in urine, (d) health surveillance.     

Notch effect on creep–fatigue life for Sn–3.5Ag solder

This paper studies the creep–fatigue crack initiation and failure lives of Sn–3.5Ag solder notched specimens focused on the multiaxial strain at the notch root. Push–pull creep–fatigue tests were performed using three circumferential notched specimens using four kinds of creep–fatigue strain waveforms. Multiaxial strains at the notched section were calculated by finite element (FE) analysis under four kinds of creep–fatigue loading. Creep–fatigue damage laws were applied for evaluating the crack initiation and failure lives using the multiaxial strains obtained by the FE analysis. von Mises equivalent strain at the notch root estimated the crack initiation lives with a large scatter as well as the failure lives. Instead, the mean value of von Mises equivalent strain over the cross section of the notch root estimated the crack initiation and failure lives with a small scatter.     

High speed zinc electrowinning using a hydrogen gas-diffusion electrode

The feasibility of a high speed zinc electrowinning cell using a Pt catalyzed hydrogen gas-diffusion electrode as an anode is investigated. This new type of zinc-winning cell is operated at a current density of 1.0 A cm^–2, which is 20 times higher than usually employed in conventional methods. Current efficiency is 86% at 0.5 A cm^–2 in an electrolyte containing 60 gl^–1 Zn+270 gl^–1 H₂SO₄, the zinc purity being at least 99.999%. The energy usage of the system is 1400 kWh and 380 m³ H₂ gas per ton of zinc.     

Large area ZnO films optimized for graded band-gap Cu(InGa)Se2-based thin-film mini-modules

In this study, two deposition methods (i.e. MOCVD and sputtering methods) to prepare n-type ZnO window layers for CIGS-based thin-film solar cells are discussed. In order to make ZnO : Al transparent conductive oxide (TCO) films prepared by DC magnetron sputtering comparable to ZnO : B TCO prepared by MOCVD, a new ZnO sputtering process is proposed by introducing a multilayer structure. Using these films, CIGS thin-film solar cells with efficiencies of greater than 14% have been fabricated with an active area of 3.2 cm². This structure was adapted to fabricate CIGS thin-film mini-modules with efficiencies around 11% having aperture area of 50 cm².     

Quenched-in vacancies in B2-structured intermetallic compound FeAl

The concentrations of quenched-in vacancies retained in B2 intermetallic compound Fe_1-cAl_c were obtained as functions of composition (0.39 < c < 0.51) and quenching temperature (773–1273 K) from lattice constant and density measurements. Obtained vacancy concentration indicates rather gradual increase with composition in lower Al content region, while it increased rapidly as the composition approaches to stoichiometric composition. Further, the data for slow-cooled (1 K min⁻¹) samples showed that retained vacancy concentration is higher than that for samples annealed at and quenched from 773 K. Observed lattice constant for each composition decreases linearly with vacancy concentration, which is interpreted in terms of atomic size effect. From changes in vacancy concentration with quenching temperature, apparent vacancy formation energies were estimated. The relation between vacancy concentration and microhardness was also examined. Present results of dependency of lattice constant on heat treatment condition confirm the hardening effect due to retained vacancy. Further, the proposed linear relation of hardness to the square root of vacancy concentration is supported by the present study.     

Development of simple and efficient in Planta transformation method for wheat (Triticum aestivum L.) using Agrobacterium tumefaciens

Wheat (Triticum aestivum L. var. Shiranekomugi) seeds were soaked in water at 22 degrees C for 1 d. Thereafter, the embryo of the soaked seeds was inoculated with Agrobacterium tumefaciens by piercing a region of the embryonic apical meristem with a needle that had been dipped in an A. tumefaciens inoculum. The inoculated seeds were incubated at 22 degrees C for 2 d and sterilized by cefotaxime (Claforan) (1000 ppm water solution) treatment and then vernalized at 5 degrees C for 25 d. Finally, the seedlings were grown to maturation (T(0) plants) and allowed to pollinate naturally for seed setting (T(1) plants) in pots under nonsterile condition. To examine the transformation by various means, four different strains of A. tumefaciens were used for transformation. The following five lines of evidence proved the transformation: altered phenotype and its transmittance to the next generation, resistance of T(1) seed germination to geneticin or hygromycin B, the detection of a transgene in T(1) plants by PCR analysis and Southern hybridization and the rescue of the plasmid consisting of the integrated T-DNA and flanking wheat genome DNA from T(1) plants. The transformation efficiency of T(1) plants, which were transformed using different A. tumefaciens strains, was estimated to be 33% by PCR analysis, 75% by Southern hybridization and 40% by plasmid rescue.     

Ingestion of gelatinized potato starch containing a high level of phosphorus decreases serum and liver lipids in rats

Potato starch is known to have a higher concentration of phosphate than other starches. The presence of phosphate groups in amylopectin results in resistance to digestion by amylase. Therefore, there is a possibility that potato starch is slowly digested, inducing a physiological effect similar to that of resistant starch and indigestible oligosaccharides. The amount of phosphate group in starch differs with potato cultivar. In the present study, we investigated the effects of gelatinized potato starch containing a high level of phosphorus on lipid metabolism in rats. For this purpose, we determined lipid levels in the serum and liver in rats fed two kinds of gelatinized potato starches with different phosphorus contents. Four groups of male Sprague-Dawley rats were fed a 60% sucrose diet (control) or one of three diets containing cornstarch (CS), Benimaru (BM) potato starch or Hokkaikogane (HK) potato starch. Fat pad weight was slightly decreased in the HK diet group compared with that in the other groups. Free fatty acids in serum were significantly lowered by dietary HK starch compared with control, and serum triglyceride in rats fed the HK diet was also decreased. In the BM and HK diet groups, triglyceride levels in the liver were decreased compared with that in the control and CS groups. As for hepatic total cholesterol level, there were no significant differences among three starch diet groups. Fecal bile acid excretion was greater in the two potato starch groups than in the control group. On the other hand, there were no significant differences in cecal short-chain fatty acid content or pH. Thus, we conclude that dietary gelatinized potato starch reduces free fatty acid and triglyceride in serum and hepatic triglyceride, but does not affect cecal fermentation.     

A Method to Evaluate Voltages to Earth During an Earth Fault in an HV Network in a System of Interconnected Earth Electrodes of MV/LV Substations

An easy and swift method to evaluate, in a system of interconnected earth electrodes, earth potentials on earthing systems of medium-voltage/low-voltage (MV/LV) substations, in an event of single-line-to-earth fault inside a high-voltage/medium- voltage (HV/MV) station, is presented. The advantage of the method is the simplicity of the mathematical model for solving complex systems of any size with a sufficient accuracy for practical purposes. This paper shows the results of simulations, performed on networks with different extensions and characteristics, organized in easy-to-read graphs and tables. A comparison of these results with the values obtained according to the procedure explained in the IEC-Standard 60909-3, and a study on the accuracy of the method has been made. Moreover, some considerations on the inclusion of earth electrodes of HV/MV stations within global earthing systems are done.     

Time-dependent deformation in an enhanced SiC/SiC composite

Time-dependent deformation in an enhanced SiC/SiC composite has been studied under constant load at high temperatures of 1200 °C, 1300 °C, and 1400 °C. Creep damage evolution was evaluated by a Young’s-modulus change of partial unloading and microscopic observation. The addition of the glassy phase in the matrix is very effective for protecting the composite from oxidation. The transient creep is dominant in creep life at all the temperatures. An empirical equation is proposed to describe creep behavior of the composite. It is found that creep activation energy increases with creep time at stresses lower than matrix cracking stress, but the activation energy remains constant at stresses higher than the matrix cracking stress. The creep strain rate of the composite is considered to be controlled by creep of fibers based on examining the time, strain, stress, and temperature dependencies of creep strain rates.