18,846 research outputs found

    Is friction responsible for the reduction of fusion rates far below the Coulomb barrier?

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    The fusion of two interacting heavy ions traditionally has been interpreted in terms of the penetration of the projectile into the target. Observed rates well below the Coulomb barrier are considerably lower than estimates obtained from penetration factors. One approach in the analysis of the data invokes coupling to non-elastic channels in the scattering as the source of the depletion. Another is to analyze those data in terms of tunneling in semi-classical models, with the observed depletion being taken as evidence of a ``friction'' under the barrier. A complementary approach is to consider such tunneling in terms of a fully quantal model. We investigate tunneling with both one-dimensional and three-dimensional models in a fully quantal approach to investigate possible sources for such a friction. We find that the observed phenomenon may not be explained by friction. However, we find that under certain conditions tunneling may be enhanced or diminished by up to 50%, which finds analogy with observation, without the invocation of a friction under the barrier.Comment: 18 pages, 15 figures embedde

    Measurement of σ(Hνeνeˉ)×BR(HZZ){\sigma(H\nu_e\bar{\nu_e})\times BR(H\rightarrow ZZ^\ast)} and Higgs production in ZZZZ fusion at a 1.4 TeV CLIC collider

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    This paper presents the potential measurement at 1.4 TeV CLIC of the cross-section (times branching ratio) of the Higgs production via WWWW fusion with the Higgs subsequently decaying in ZZZZ^\ast, σ(Hνeνeˉ)×BR(HZZ){\sigma(H\nu_e\bar{\nu_e})\times BR(H\rightarrow ZZ^\ast)}, and of the Higgs production via ZZZZ fusion with the Higgs subsequently decaying in bbˉb\bar{b}, σ(He+e)×BR(Hbbˉ){\sigma(He{^+}e{^-})\times BR(H\rightarrow b\bar{b})}. For the HZZH\rightarrow ZZ^\ast decay the hadronic final state, ZZqqˉqqˉ{ZZ^\ast\rightarrow q\bar{q}q\bar{q}}, and the semi-leptonic final state, ZZqqˉl+l{ZZ^\ast\rightarrow q\bar{q}l^+l^-}, are considered. The results show that σ(Hνeνeˉ)×BR(HZZ){\sigma(H\nu_e\bar{\nu_e})\times BR(H\rightarrow ZZ^\ast)} can be measured with a precision of 18.3% and 6% for the hadronic and semi-leptonic channel, respectively. σ(He+e)×BR(Hbbˉ){\sigma(He{^+}e{^-})\times BR(H\rightarrow b\bar{b})} can be measured with a precision of 1.7%. This measurement also contributes to the determination of the Higgs coupling to the ZZ boson, gHZZg_{H_{ZZ}}.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS14), Belgrade, Serbia, 6-10 October 201

    Electrometer system measures nanoamps at high voltage

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    Floating electrometer eliminates major source of error since any leakage from electrometer case, which is at high voltage, appears only as load on high voltage supply and not as part of current being measured. Commands to and data from floating electrometer are transferred across high voltage interface by means of optical channels

    A FAMILY OF CATION ATPASE-LIKE MOLECULES FROM PLASMODIUM-FALCIPARUM

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    Abstract. We report the nucleotide and derived amino acid sequence of the ATPase 1 gene from Plasmodium falciparum. The amino acid sequence shares homology with the family of "P-type cation transloeating ATPases in conserved regions important for nucleotide binding, conformational change, or phosphorylation. The gene, which is present on chromosome 5, has a product longer than any other reported for a P-type ATPase. Interstrain analysis from 12 parasite isolates by the polymerase chain reaction reveals that a 330-bp nucleotide sequence encoding three cytoplasmic regions conserved in cation ATPases (regions a-c) is of constant length. By contrast, another 360-bp sequence which is one of four regions we refer to as

    Exposure assessment of traditional and IPM farmers on using pesticides: A case study at Bang Rieng Sub District, Khuan Nieng District, Songkhla Province

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    A questionnaire was developed to quantitatively evaluate the exposure to pesticides and to gauge the concentration of organophosphate pesticides such as chlorpyrifos and methyl-parathion while the farmers of Bang Rieng were spraying these pesticides. The results were applied to the exposure assessment and to compare the quantity of exposure to these pesticides between 33 traditional and 40 integrated pest management (IPM) farmers of Bang Rieng. There was a significant difference in the level of exposure between the traditional farmers, who had the average pesticide exposure scores of 58.30 points and the IPM farmers, whose average scores were 53.50 points, (p < 0.015). Concentrations of organophosphate pesticides chlorpyrifos and methyl-parathion were measured. Thirty-three air samples were collected by personal sampling during the period of pesticide spraying. Traditional farmers were exposed to higher levels of the pesticide(s) with a mean concentration of 0.1865 mg/m compared to the IPM farmers who were exposed to a mean pesticide concentration of 0.037 mg/m3. It was estimated that the farmers of Bang Rieng would be exposed to 186-19,616.6 mg of the organophosphatepesticide(s) via inhalation throughout their lifetime (65 years). Moreover, according to the exposure assessment, the traditional farmers exposed to a greater amount of the pesticide(s) via inhalation compared to the IPM farmers

    Development and application of an assay for uranyl complexation by fungal metabolites, including siderophores

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    An assay to detect UO2 2+ complexation was developed based on the chrome azurol S (CAS) assay for siderophores (B. Schwyn and J. B. Neilands, Anal. Biochem. 160:47-56, 1987) and was used to investigate the ability of fungal metabolites to complex actinides. In this assay the discoloration of two dyed agars (one containing a CAS-Fe3+ dye and the other containing a CAS-UO2 2+ dye) caused by ligands was quantified. The assay was tested by using the siderophore desferrioxamine B (DFO), and the results showed that there was a regular, reproducible relationship between discoloration and the amount of siderophore added. The ratio of the discoloration on the CAS-UO2 2+ agar to the discoloration on the CAS-Fe3+ agar was independent of the amount of siderophore added. A total of 113 fungi and yeasts were isolated from three soil samples taken from the Peak District National Park. The fungi were screened for the production of UO2 2+ chelators by using the CAS-based assay and were also tested specifically for hydroxamate siderophore production by using the hydroxamate siderophore auxotroph Aureobacterium flavescens JG-9. This organism is highly sensitive to the presence of hydroxamate siderophores. However, the CAS-based assay was found to be less sensitive than the A. flavescens JG-9 assay. No significant difference between the results for each site for the two tests was found. Three isolates were selected for further study and were identified as two Pencillium species and a Mucor species. Our results show that the new assay can be effectively used to screen fungi for the production of UO2 2+ chelating ligands. We suggest that hydroxamate siderophores can be produced by mucoraceous fungi

    Complex Scaled Spectrum Completeness for Coupled Channels

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    The Complex Scaling Method (CSM) provides scattering wave functions which regularize resonances and suggest a resolution of the identity in terms of such resonances, completed by the bound states and a smoothed continuum. But, in the case of inelastic scattering with many channels, the existence of such a resolution under complex scaling is still debated. Taking advantage of results obtained earlier for the two channel case, this paper proposes a representation in which the convergence of a resolution of the identity can be more easily tested. The representation is valid for any finite number of coupled channels for inelastic scattering without rearrangement.Comment: Latex file, 13 pages, 4 eps-figure
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