5,382 research outputs found

    Striations in the Taurus molecular cloud: Kelvin-Helmholtz instability or MHD waves?

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    The origin of striations aligned along the local magnetic field direction in the translucent envelope of the Taurus molecular cloud is examined with new observations of 12CO and 13CO J=2-1 emission obtained with the 10~m submillimeter telescope of the Arizona Radio Observatory. These data identify a periodic pattern of excess blue and redshifted emission that is responsible for the striations. For both 12CO and 13CO, spatial variations of the J=2-1 to J=1-0 line ratio are small and are not spatially correlated with the striation locations. A medium comprised of unresolved CO emitting substructures (cells) with a beam area filling factor less than unity at any velocity is required to explain the average line ratios and brightness temperatures. We propose that the striations result from the modulation of velocities and the beam filling factor of the cells as a result of either the Kelvin-Helmholtz instability or magnetosonic waves propagating through the envelope of the Taurus molecular cloud. Both processes are likely common features in molecular clouds that are sub-Alfvenic and may explain low column density, cirrus-like features similarly aligned with the magnetic field observed throughout the interstellar medium in far-infrared surveys of dust emission.Comment: 11 pages, 4 figures. Accepted for publication in MNRA

    Effects of different raising systems on colour and quality characteristics of Turkish Pekin duck meats

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    The current trial was conducted to determine the influence of different raising systems on the meat quality properties of male Turkish Pekin ducks. Ninety male ducklings were randomly allocated to three experimental groups: an animal-fish integrated farming group (IG), a non-animal-fish integrated farming group (NIG) and a poultry house group (PHG). All ducklings were fed a starter diet from weeks 2 to 6 and a finisher diet from weeks 6 to 10. Feed and water were offered ad libitum. At the end of the trial all ducks were slaughtered and the carcasses were stored at 3 °C for 24 hours, after which L*, a* and b* values of the carcass skins were measured. After standard dissection of carcasses, pectoralis muscles were obtained on which pH, colour (L*, a*, b*, C and H), total aerobic mesophilic, total aerobic psychrotrophic, lactic acid bacteria, Micrococcus/Staphylococcus, yeast-mould and Enterobacteriaceae counts were determined. The different raising systems of the ducks had significant effects on the pH, total aerobic mesophilic, Enterobacteriaceae, and L* and b* values of the pectoralis muscle. The lowest pH, total aerobic mesophilic and Enterobacteriaceae counts were found in the PHG group. The lowest L* values for the pectoralis muscle were found in the IG group while the highest a* value was recorded in the IG group. Significant differences in skin colour were observed between the experimental groups. For all production groups, all microbial counts were found to be within acceptable ranges. However, pH, total aerobic mesophilic and Enterobacteriaceae results were found to be lower in the PHG group than in the other groups. Different raising systems were thus found to affect the meat and skin colour of ducks, which may influence the preference of consumers. Keywords: Pekin duck, integrated farming, carcass and meat colour, microbial propertiesSouth African Journal of Animal Science Vol. 38 (3) 2008: pp. 217-22

    Temperature dependence of electrical properties in In/Cu2ZnSnTe4/Si/Ag diodes

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    WOS: 000458625200001Cu2ZnSnTe4 (CZTTe) thin films with In metal contact were deposited by thermal evaporation on monocrystalline n-type Si wafers with Ag ohmic contact to investigate the device characteristics of an In/CZTTe/Si/Ag diode. The variation in electrical characteristics of the diode was analysed by carrying out current-voltage (I-V) measurements in the temperature range of 220-360 K. The forward bias I-V behaviour was modelled according to the thermionic emission (TE) theory to obtain main diode parameters. In addition, the experimental data were detailed by taking into account the presence of an interfacial layer and possible dominant current transport mechanisms were studied under analysis of ideality factor, n. Strong effects of temperature were observed on zero-bias barrier height (Phi(B0)) and n values due to barrier height inhomogeneity at the interface. The anomaly observed in the analysis of TE was modelled by Gaussian distribution (GD) of barrier heights with 0.844 eV mean barrier height and 0.132 V standard deviation. According to the Tung's theoretical approach, a linear correlation between Phi(B0) and n cannot be satisfied, and thus the modified Richardson plot was used to determine Richardson constant (A*). As a result, A* was calculated approximately as 120.6 A cm(-2) K-2 very close to the theoretical value for n-Si. In addition, the effects of series resistance (R-s) by estimating from Cheng's function and density of surface states (N-ss) by taking the bias dependence of effective barrier height, were discussed

    The effects of physical and chemical changes on the optimum harvest maturity in some avocado cultivars

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    The aim of this study was to determine physical and chemical changes during fruit development and their relationship with optimum harvest maturity for Bacon, Fuerte and Zutano avocado cultivars grownunder Dörtyol ecological condition. Fruits cv. Bacon, Fuerte and Zutano were obtained trees grafted on seedlings and planted 5 m x 6 m in Dörtyol Research Station of Faculty of Agriculture, Mustafa KemalUniversity. Fruit width and length, weight, skin and flesh color (L* and hue), total soluble solid (TSS), titratable acidity (TA), TSS/TA, fruit flesh firmness, juice pH, dry weight and oil content were measuredon fruits samples collected from tagged trees from June drop to ripening at a 15 days interval during fruit development. Data indicated that oil and dry matter content, flesh firmness and fruit weight were important criteria in determining optimum harvest maturity. Based on the all criteria, the period from the end of November to middle of December was the optimum harvest time for these cultivars in order to deliver fruit at optimum commercial maturity and quality and to obtain adequate storage time

    Electronic transport characterization of AlGaN/GaN heterostructures using quantitative mobility spectrum analysis

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    Cataloged from PDF version of article.Resistivity and Hall effect measurements in nominally undoped Al0.25Ga0.75N/GaN heterostructures grown on sapphire substrate by metal-organic chemical vapor deposition are carried out as a function of temperature (20-350 K) and magnetic field (0-1.5 T). The measurement results are analyzed using the quantitative mobility spectrum analysis techniques. It is found that there is strong two-dimensional electron gas localization below 100 K, while the thermally activated minority carriers with the activation energies of similar to 58 and similar to 218 meV contribute to the electron transport at high temperatures. (C) 2007 American Institute of Physics

    Degradation Issues in Solid Oxide Cells During High Temperature Electrolysis

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    Idaho National Laboratory (INL) is performing high-temperature electrolysis (HTE) research to generate hydrogen using solid oxide electrolysis cells (SOECs). The project goals are to address the technical and degradation issues associated with the SOECs. This paper provides a summary of ongoing INL and INL-sponsored activities aimed at addressing SOEC degradation. These activities include stack testing, post-test examination, degradation modeling, and issues that need to be addressed in the future. Major degradation issues relating to solid oxide fuel cells (SOFC) are relatively better understood than those for SOECs. Some of the degradation mechanisms in SOFCs include contact problems between adjacent cell components, microstructural deterioration (coarsening) of the porous electrodes, and blocking of the reaction sites within the electrodes. Contact problems include delamination of an electrode from the electrolyte, growth of a poorly (electronically) conducting oxide layer between the metallic interconnect plates and the electrodes, and lack of contact between the interconnect and the electrode. INL's test results on HTE using solid oxide cells do not provide clear evidence as to whether different events lead to similar or drastically different electrochemical degradation mechanisms. Post-test examination of the SOECs showed that the hydrogen electrode and interconnect get partially oxidized and become nonconductive. This is most likely caused by the hydrogen stream composition and flow rate during cooldown. The oxygen electrode side of the stacks seemed to be responsible for the observed degradation because of large areas of electrode delamination. Based on the oxygen electrode appearance, the degradation of these stacks was largely controlled by the oxygen electrode delamination rate. Virkar et al. [19-22] have developed a SOEC model based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic nonequilibrium. This model is under continued development. It shows that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential within the electrolyte. The chemical potential within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just under the oxygen electrode (anode)/electrolyte interface, leading to electrode delamination. This theory is being further refined and tested by introducing some electronic conduction in the electrolyte.United States. Department of Energy. Office of Energy Efficiency and Renewable EnergyUnited States. Office of the Assistant Secretary for Nuclear Energ

    Water distribution in shocked regions of the NGC1333-IRAS4A protostellar outflow

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    We present the study of the H2O spatial distribution at two bright shocked regions along IRAS4A, one of the strongest H2O emitters among the Class 0 outflows. We obtained Herschel-PACS maps of the IRAS4A outflow and HIFI observations of two shocked positions. The largest HIFI beam of 38 arcsec at 557 GHz was mapped in several key water lines with different upper energy levels, to reveal possible spatial variations of the line profiles. We detect four H2O lines and CO (16-15) at the two selected positions. In addition, transitions from related outflow and envelope tracers are detected. Different gas components associated with the shock are identified in the H2O emission. In particular, at the head of the red lobe of the outflow, two distinct gas components with different excitation conditions are distinguished in the HIFI emission maps: a compact component, detected in the ground-state water lines, and a more extended one. Assuming that these two components correspond to two different temperature components observed in previous H2O and CO studies, the excitation analysis of the H2O emission suggests that the compact (about 3 arcsec) component is associated with a hot (T~1000 K) gas with densities ~(1-4)x10^5 cm^{-3}, whereas the extended one (10-17 arcsec) traces a warm (T~300-500 K) and dense gas (~(3-5)x10^7 cm^{-3}). Finally, using the CO (16-15) emission observed at R2, we estimate the H2O/H2 abundance of the warm and hot components to be (7-10)x10^{-7} and (3-7)x10^{-5}. Our data allowed us, for the first time, to resolve spatially the two temperature components previously observed with HIFI and PACS. We propose that the compact hot component may be associated with the jet that impacts the surrounding material, whereas the warm, dense, and extended component originates from the compression of the ambient gas by the propagating flow.Comment: 13 pages, 11 figures. Accepted for publication in Astronomy and Astrophysic

    A highly sensitive and specific enzyme-linked immunosorbent assay of antibodies to hepatitis C virus

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    In this study, a 178 amino acids long portion of the hepatitis C virus (HCV) core gene was cloned, sequenced, expressed in Escherichia coli, and purified. The resulting antigen (C178) was tested with human sera enzyme-linked immunosorbent assay (ELISA) in order to assess its ability to diagnose HCV. It was shown by ELISA that 92% of the patients sera, diagnosed previously by a 3(rd) generation enzyme immunoassay (EIA) as HCV-positive, had antibodies against the C178 antigen. This antigen gave no false positive results when tested with anti-HCV-negative sera
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