4,448 research outputs found

    Temperature variation of the resistivity of metallic strain gauge materials Final report

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    Temperature effects on electrical resistivity of metallic strain gage material

    Lambda-parameter of lattice QCD with Symanzik improved gluon actions

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    We compute the ratio Lambda_L/Lambda_MS, where the scale parameter Lambda_L is associated with a lattice formulation of QCD. We consider a 3-parameter family of gluon actions, which are most frequently used for O(a) improvement a` la Symanzik. The gluon action is put togeter with standard discretizations for fermions (Wilson/clover, overlap), to provide Lambda_L for several possible combinations of fermion and gluon actions. We employ the background field technique in order to calculate the 1PI 2-point function of the background field; this leads to the coupling constant renormalization function, Z_g, at 1-loop level. Our results are obtained for an extensive range of values for the Symanzik coefficients.Comment: 11 pages, 3 figures, 3 table

    Perturbative Renormalization Factors of Bilinear Quark Operators for Improved Gluon and Quark Actions in Lattice QCD

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    We calculate one-loop renormalization factors of bilinear quark operators for gluon action including six-link loops and O(a)O(a)-improved quark action in the limit of massless quark. We find that finite parts of one-loop coefficients of renormalization factors diminish monotonically as either of the coefficients c1c_1 or c2+c3c_2+c_3 of the six-link terms are decreased below zero. Detailed numerical results are given, for general values of the clover coefficient, for the tree-level improved gluon action in the Symanzik approach (c1=1/12,c2=c3=0)(c_1=-1/12, c_2=c_3=0) and for the choices suggested by Wilson (c1=0.252,c2=0,c3=0.17)(c_1=-0.252, c_2=0, c_3=-0.17) and by Iwasaki (c1=0.331,c2=c3=0(c_1=-0.331, c_2=c_3=0 and c1=0.27,c2+c3=0.04)c_1=-0.27, c_2+c_3=-0.04) from renormalization-group analyses. Compared with the case of the standard plaquette gluon action, finite parts of one-loop coefficients are reduced by 10--20% for the Symanzik action, and approximately by a factor two for the renormalization-group improved gluon actions.Comment: 19 pages, REVTeX, with 3 epsf figure

    ATP-dependent chromatosome remodeling

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    Chromatin serves to package, protect and organize the complex eukaryotic genomes to assure their stable inheritance over many cell generations. At the same time, chromatin must be dynamic to allow continued use of DNA during a cell's lifetime. One important principle that endows chromatin with flexibility involves ATP-dependent `remodeling' factors, which alter DNA-histone interactions to form, disrupt or move nucleosomes. Remodeling is well documented at the nucleosomal level, but little is known about the action of remodeling factors in a more physiological chromatin environment. Recent findings suggest that some remodeling machines can reorganize even folded chromatin fibers containing the linker histone H1, extending the potential scope of remodeling reactions to the bulk of euchromatin

    Modular optical design of the LHC experimental insertions

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    To optimize the use of space, the LHC insertions combine dispersion matching (arc and ring separation/recombination), beam focalization at the interaction point and betatron phase advance control within a unique optical module. In this paper, we show that the significant dispersion produced by the separation/recombination dipoles can be treated separately, allowing a separation of the optical functions in the insertion. This methodology yields the flexibility and robustness needed to adapt the insertion to a lattice with a variable tune split
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