The crystal structure of eulytite Pb3BiV3O12

The crystal structure of Pb₃BiV₃O₁₂ was solved using single-crystal X-ray diffraction technique. The compound crystallizes in the cubic system (No. 220) with eulytite structure with a = 10.7490(7) Å, V = 1241.95(14) Å³ and Z = 4. The final R₁ value of 0.0198 (wR₂=0.0384) was achieved for 359 independent reflections during the structure refinement. The Pb²⁺ and Bi³⁺ cations occupy the special position (16c) while the oxygen anions occupy the general position (48e) in the crystal structure. Unlike many other eulytite compounds, all the crystallographic positions are fully occupied. The structure consists of edge-shared Pb/Bi octahedra linked at the corners to independent [VO₄]³⁻ tetrahedra units, generating a eulytite-type network in the crystal lattice.     

Rainwater Management for Smallholder Irrigation and it’s Impact on Crop Yields in Eastern India

A tank cum open dug well system suitable for plateau region of eastern India has been developed for providing reliable irrigation to croplands. The system comprises of a series of tanks with open dug wells in the recharge zone of the tank that reharvest back the seepage water. Thus, the rainwater remaining in the tank as well as partial seeped water is used for providing round the year full irrigation. This system was evaluated in field in Keonjhar district of Orissa of eastern India with six tanks and five wells in two drainage lines. The total command area of the system of six tanks and five wells in both drainage lines is 23 ha and the total irrigation potential is 44.5 ha. The total cost of the system is US $19,180 making the cost of irrigation resource creation as US $426 per ha which is much less than about $2,220 per ha for major and medium irrigation projects in the last decade of 20th century. The system increased the rice yields from 1.92 t ha^− 1 to a range of 2.25 to 3.8 t ha^− 1 depending upon the package of practices or the amount of inputs. The farmers went for crops in post-monsoon and summer season and the cropping intensity rose to 112% in the first year, 126% in the second year and 132% in the third year. The internal rate of return from the system was 13.4% at the present level of utilization, which is about 2.4% more than the prime-lending rate of Indian banks, and 3.4% more than the lending rate for agricultural purposes.     

Collaborative investigations on thoron and radon in some rural communities of Balkans

This paper deals with the results of the first-field use in the Balkans, i.e. Serbia and Republic of Srpska (Bosnia and Hercegovina), of a passive polycarbonate Mark II type and poliallyldiglycol carbonate (Cr-39) alpha track detectors sensitive to thoron as well as to radon. Both types of solid state nuclear track detectors were designed and supplied by National Institute of Radiological Sciences (NIRS), Chiba, Japan. The commercial names for these detectors which all have been field tested in Balkan rural communities are known as: UFO and RADUET passive discriminative radon/thoron detectors. No database of thoron and thoron progeny concentrations in dwellings in Serbia or Balkans region exist, and as a result, the level of exposure of the Serbian population to thoron and its progeny is unknown so far.     

Effects of slip on sheet-driven flow and heat transfer of a third grade fluid past a stretching sheet

The entrained flow and heat transfer of an electrically conducting non-Newtonian fluid due to a stretching surface subject to partial slip is considered. The partial slip is controlled by a dimensionless slip factor, which varies between zero (total adhesion) and infinity (full slip). The constitutive equation of the non-Newtonian fluid is modeled by that for a third grade fluid. The heat transfer analysis has been carried out for two heating processes, namely, (i) with prescribed surface temperature (PST case) and (ii) prescribed surface heat flux (PHF case). Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective second order numerical scheme has been adopted to solve the obtained differential equations. The important finding in this communication is the combined effects of the partial slip, magnetic field and the third grade fluid parameter on the velocity, skin-friction coefficient and the temperature field. It is interesting to find that slip decreases the momentum boundary layer thickness and increases the thermal boundary layer thickness, whereas the third grade fluid parameter has an opposite effect on the thermal and velocity boundary layers.     

Theory of electron distributions and63Cu and17O nuclear quadrupole interactions in YBa2Cu3O7 and YBa2Cu3O6

Ab initio unrestricted Hartree-Fock Cluster investigations have been carried out on the electronic structures of the YBa₂Cu₃O₇ and YBa₂Cu₃O₆ systems. The results of these investigations provide satisfactory explanations of available⁶³Cu and¹⁷O nuclear quadrupole interaction data. The electron distributions obtained rule out the presence of Cu³⁺ ions and are supportive of the presence of Cu²⁺, Cu¹⁺, O¹⁻ ions in the O₇ system and Cu²⁺, Cu¹⁺ and O²⁻ in the O₆ system with actual charges departing significantly from the formal charges, especially in the O₇ system, indicating the importance of covalency effects. Suggestions will be made regarding possible sources that can bridge the remaining gap between theoretical and experimental results for the nuclear quadrupole interaction parameters.     

Safety evaluation of ambrette (<Emphasis Type="Italic">Abelmoschus moschatus</Emphasis> linn) seed oil

The seeds of ambrette (Abelmoschus moschatus Linn), after selective extraction of fragrance from the seed coat, are flaked and extracted with hexane to obtain a fatty oil. The FA composition and iodine value of the oil indicate it possesses saturated, monounsaturated, and polyunsaturated FA in ratios close to the recommendations of the United Nations World Health Organization; these characteristics make it suitable as an edible oil. Acute oral toxicity and safety evaluation in a 13-wk feeding trial on albino rats showed the oil is comparable to groundnut oil in all the parameters and is suitable for edible use.     

Effects of oxygen and sulfur on alloying element vaporization rates during laser welding

Inadequate control of weld metal composition due to vaporization of volatile alloying elements is a serious problem in the welding of many important engineering alloys. Effectiveness of surface active elements such as oxygen or sulfur in blocking vaporization sites on the weld pool surface was investigated. Several iron samples doped with oxygen or sulfur were exposed to a carbon dioxide laser beam in pulsed mode. The time average metal vaporization rates and the emission spectra were compared with those obtained from ultra pure iron samples. Since the weld pool surface area and temperature distribution are affected by oxygen and sulfur, the true effects of these elements on metal vaporization rates cannot be easily evaluated from welding data. Therefore, rates of isothermal vaporization of iron and copper drops doped with oxygen or sulfur were determined both in the presence and the absence of low pressure argon plasma. These rates were compared with the rates of vaporization of ultrapure metal drops. Presence of sulfur or oxygen in metals always resulted in increased metal vaporization rates. The results are analyzed on the basis of interfacial phenomena.     

Mechanical and tribological properties of zinc-aluminium metal-matrix composites

Recently, commercial Zn-Al foundry alloys such as ZA-27 have found increasing use for many applications and have competed effectively against copper, aluminium and iron-based foundry alloys. However, the elevated temperature (> 100°C) properties of zinc-aluminium alloys are unsatisfactory and restrict their use in some applications. One viable approach to improving the elevated temperature properties is to reinforce the zinc-aluminium alloys with alumina fibres. In this investigation, the mechanical properties of a Zn-Al alloy reinforced with alumina fibres were evaluated. Tensile, compression and impact properties were determined at 25, 100 and 150°C. Lubricated wear tests were also performed on the unreinforced alloy and composites. It was found that although fibre reinforcement did result in some improvement of tensile and compression properties at elevated temperatures, the composites had poor toughness and ductility. The presence of a brittle SiO₂ layer at the fibre/matrix interfaces resulted in fibre/matrix decohesion under tensile loading, impairing the performance of the reinforced materials. Some improvement in wear resistance was noted for the composite materials but fibre reinforcement did not yield significant improvement in fatigue resistance.     

Normal impact of rough surfaces in presence of adhesion

The paper describes a theoretical study of normal impact between solids with small-scale surface asperities. An elastic-plastic impact model is used to study the normal impact between rough surfaces in presence of surface forces. The well-established elastic and plastic adhesion indices are used to consider the different conditions arising out of varying impact velocity and material parameters. The study shows that the coefficient of restitution is affected by material-properties, surface-topography and impact velocity. Results clearly indicate that high impact velocity is desirable in order to achieve low coefficient of restitution. However, there are certain combinations of material properties and surface conditions, given by the choice of adhesion indices, where coefficient of restitution falls to a very low value.     

Polymers from renewable resources. V. Synthesis and characterization of thermosetting resins derived from cashew nut shell liquid (CNSL)–furfural-substituted aromatic compounds

A number of resins were synthesized by reacting cardanol, a byproduct of the cashew industry, with furfural and substituted aromatic compounds in the presence of acid and basic catalysts. The resins were characterized by IR and NMR spectra and shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behavior of the resins was also studied. A plausible degradation mechanism is suggested. © 1994 John Wiley & Sons, Inc.