On the formation of the stircast structure

The conditions of solidification in a stirred bulk liquid are investigated to explain the non-dendritic microstructure of stircast alloys. A model of stirred solidification is presented, which allows a comparison of the solidification behaviour of metal alloys and organic analogues. This shows that nucleation and growth of solid in e bulk liquid is facilitated under the influence of stirring, provided the Prandtl-number is greater than unity. It is shown further that the solute gradient ahead of the solid-liquid interface of floating particles in a bulk liquid is reduced by the fluid flow. Combined with the thermal properties, and in analogy with the constitutional supercooling criterion, A is shown that solid growth in metals is likely to be cellular in an early stage of the solidification, In contrast, in stirred organic analogues, the solidification is dendritic in the early stage.     

关于放射性发光涂料产品辐射防护标准的讨论

本文描述了我国放射性发光涂料的生产,使用状况和部分发光涂料产品的照射量测量结果。估算了全民剂量,并对放射性发光涂料的辐射防护标准进行了讨论。     

NLR experience with high velocity burner rig testing 1979–1989

The NLH. has two high velocity burner rigs for oxidation and hot corrosion testing. A large, custom-built rig was commissioned in 1977 to enable actual components to be tested. A smaller rig for specimen testing was purchased in 1986. Experience with these rigs over the last decade is reviewed.     

Control of virulence gene expression by plant calcium in the phytopathogen Erwinia carotovora

1. The authors performed both microdialysis and behavioral measurement in each of rats, in order to examine effects of nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (LNAME;30 mg/kg,i.p.) on striatal dopamine (DA) release and stereotypy induced by a single administration of methamphetamine (MA)(4 mg/kg,s.c.), simultaneously. 2. LNAME administered prior to MA significantly decreased level of locomotion-stereotypy rating scores induced by MA. 3. In the same animals, LNAME had no effect on MA-induced striatal DA release. 4. The results suggest that NO synthesis inhibition attenuated MA-induced stereotypy by modulating neuronal process subsequent to activation of postsynaptic DA receptors.     

Time and mode of nitrogen fertilizer application to tropical wetland rice

In experiments with transplanted rice (Oryza sativa L.) at the International Rice Research Institute, Philippines, two methods of split application of urea and ammonium sulfate were compared with deep, point placement (10 cm) of urea supergranules and broadcast application of a slow-release fertilizer sulfur-coated urea (SCU). Comparisons were made in the wet and dry seasons and were based on rice yield and N uptake. Urea- and ammonium-N concentrations and pH of the floodwater were measured to aid interpretation of the results.Split applications of urea were generally less efficient than ammonium sulfate. The split in which the initial fertilizer dose was broadcast and incorporated into the soil before transplanting was more effective than the split in which the fertilizer was broadcast directly into the floodwater 21 days after transplanting. Both split applications were inferior to the urea supergranules and SCU, in terms of both yield and N uptake efficiency; average apparent N recoveries ranged from 30% for the delayed split urea to 80% for the urea supergranule.Broadcast applications of urea and ammonium sulfate produced high floodwater concentrations of urea- and ammonium-N, which fell to zero within 4–5 days. Floodwater pH was as high as 9.3 and fluctuated diurnally due to heavy algal growth. Ammonia volatilization and algal immobilization of N in the floodwater were probably responsible for the poor efficiency of the split applications; the supergranules and SCU on the other hand produced low floodwater N concentrations and were efficiently used by the rice crop.     

Mutagenic activity in drinking water prepared from groundwater: a survey of ten cities in The Netherlands

A survey of the mutagenic activity (Ames Salmonella/microsome assay) in drinking water prepared from groundwater in 10 cities of The Netherlands is presented. Mutagenic activity with strain TA98 with S-9 mix was found in the drinking water of six cities. There are strong indications that this mutagenic activity is caused by organics of natural origin. In the drinking water of three cities, trichloroethane, trichloroethene and tetrachloroethene were detected, which indicates that in these water-catchment areas organic pollutants have reached groundwater.