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[en] In the present paper, the results of radon activity recorded in domestic regions of the Kulu area (Himachal Pradesh, India) known for uranium mineralisation are reported. Time integrated track etch technique has been used for the measurement of indoor radon levels. Bare cellulose nitrate LR-115 type II films have been used as detectors in the survey of radon. The calibration constant of 4.8x102 tracks cm-2 day-1 per WL of radon at equilibrium (which corresponds to 12.97x10-2 tracks cm-2 d-1 per Bq m-3) determined by Subba Ramu et al. (Sci. Total Environ. 73 (1988) 245) has been used to express radon activity in Bq m-3. In some of the dwellings the levels of radon activity are found to be quite high giving an annual exposure dose that crosses the safety limits set by the International Commission on Radiological Protection (ICRP, Protection against radon-222 at home and at work, ICRP Publication 65, Annals of the ICRP, 23 (2), 1993). A study of seasonal variations of indoor radon in some of the dwellings has also been carried out
[en] This paper deals with the measurement of uranium content in soil, rock, water and plant samples collected from some areas of Kulu district, Himachal Pradesh, India. The anomalous uranium values have been observed in soil, rock and plant samples belonging to Balsari village of the area. Uranium concentration in water samples is quite low and is thus safe for drinking. The aim of the work is to explore the possibility of uranium exploration and for the health risk assessment in the area
[en] In intense pulsed light sintering (IPL), pulsed large-area visible light from a xenon lamp is absorbed by nanoparticle films or patterns and converted to heat, resulting in rapid sintering of the nanoparticles. This work experimentally characterizes IPL of silver nanoparticle films. A newly observed turning point in the evolution of film temperature during IPL is correlated to the observation, in literature and in this work, that film densification levels off beyond a critical pulse fluence and number of pulses. A computational model is developed that couples electromagnetic finite element analysis, heat transfer models and densification models to predict the evolution of film temperature and density during IPL. This model is able to capture the experimentally observed turning point in temperature during IPL, whereas current models of IPL are unable to do so. It is shown that the temperature turning point occurs due to a coupling between optical absorption and densification in the nanoparticle film, mediated by a change in nanoscale shape of the deposited nanoparticles due to interparticle neck growth. Further, it is found that the optical fluence per pulse has a greater effect on the achievable film density in IPL, as compared to the number of pulses. (paper)
[en] This paper reports on the development of a cluster ion source that can generate intense beams of metal and semiconductor clusters of a very wide-size range. With the source, the authors observed intense beams of carbon clusters with mean cluster sizes of up to 4000 atoms/ clusters. However, we have found that for generating small fullerenes, such as C60 and C70, the recently discovered technique by Kraetschmer et al. is much more efficient. By improving the technique, the authors have generated gram quantities of C60 and C70 and systematically investigated their thermal desorption properties. During the heating process, we have discovered that at high temperatures the bulk fullerenes, fullerite, transformed to another form of carbon, which still evaporates at temperatures above 700 C, but does not dissolve in benzene
[en] Disease transmission is an infrequent but important risk associated with bone transplantation. Human immunodeficiency virus infection is particularly important because of delay in seroconversion of the potential donor. This is so-call 'window' period may extend for several months. Almost all human immunodeficiency virus transmission via the transplantation of blood or tissue since the implementation of anti-HIV screening in 1985 has been during this window period. The performance of newer assays to detect viral and serologic markers may reduce this risk of disease transmission. We present the strategy employed at the Queensland Bone Bank to minimise the risk of HIV transmission through an infected donor
[en] Heat transfer fluids are important component in transferring heat through heat exchangers in variety of industrial applications including solar energy. Measurement of convective heat transfer coefficients in experimental setup simulating as much actual operating conditions as possible is one reliable method. Experimenting with fully synthetic heat transfer oil meant for use in concentrated solar power plants, the paper presents experimental data for the oil run in a closed-loop indoor test setup up to high temperatures of 200 °C and at two flow rates of 900 and 1200 kg h−1. Convective heat transfer coefficients were calculated based on actual steady-state heat transfer taking place between the hot oil and cold water flowing in a counterflow shell and tube heat exchanger. It was observed that the convective heat transfer coefficient is higher at lower oil flow rate and there is more variation in the experimental values at lower flow rates of oil. On the contrary, the coefficients of convective heat transfer on the basis of empirical correlations at same two oil flow rates were calculated to be higher at higher oil flow rate with the variation uniformly patterned. With respect to calculations based on empirical correlations and experimentally observed values, a comparison of convective heat transfer coefficient “hi” for oil at the two flow rates, the empirically calculated heat transfer coefficients show an increasing trend with a definite gradient, while the experimental values show variable trend which is increasing initially with temperature, then drops slightly and then again starts to increase. In view of the fact that the empirical correlations do not take into account the nature and chemistry of the oil, it has been concluded that the experimental determination of heat transfer coefficient is reliable and feasible, though it may not necessarily correlate with the theoretically derived values.
[en] The distribution of fragments resulting from collisions between 50--200-keV C60+ ions and H2 and He is found to follow approximately a simple power law I(m)=cpm where p is a constant depending on both energy and target gas, and m is the number of missing ''pairs'' of carbon atoms. Based on this observation, a new dynamical fragmentation model involving the ratio of two characteristic times is proposed. In collisions by 300-keV C60++ ions, the singly charged products are distributed quite differently, which implies the first evidence of the presence of charge-separation reactions
[en] Deposition of TiAlN/Nb, TiAlN/Ta, TiAlN/W and TiAlN/Zr multilayer coatings on 409 stainless steel was studied by CVD in a fluidized bed reactor (FBR-CVD). The coatings consisted of four TiAlN layers with individual thickness of 2.5-3.5 μm, and four metal interlayers with thicknesses in the range of 100-250 nm. The W interlayers suffered partial nitridation during the coating process and the resulting coatings had poor adhesion. Deposition of Zr through reduction of ZrI4 by H2 was found to be inefficient. Both TiAlN/Nb and TiAlN/Ta coatings showed good adhesion, but only TiAlN/Nb provided sulfidation resistance to 409 steel during exposure to simulated coal gas at 1173 K for 300 h. Though outward diffusion of Cr took place during the corrosion test, the results reported in this paper suggest that TiAlN/Nb coatings are promising candidates for corrosion protection of steels under typical coal gasifier conditions
[en] Scanning tunneling microscopy (STM) has been used to obtain images and current--voltage (I--V) curves of carbon nanotubes produced by arc discharge of carbon electrodes. The STM I--V curves indicate that carbon nanotubes with diameters from 2.0 to 5.1 nm have a metallic density of states. Using STM, we also observe nanometer-size graphene sheets which are four graphite layers thick. The STM images of carbon nanotubes are in good agreement with transmission electron microscope images. copyright 1995 American Vacuum Society
[en] We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T ∼ 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T ∼ 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.