The effect of Fe atoms on the adsorption of a W atom on W(100) surface

We report a first-principles calculation that models the effect of iron (Fe) atoms on the adsorption of a tungsten (W) atom on W(100) surfaces. The adsorption of a W atom on a clean W(100) surface is compared with that of a W atom on a W(100) surface covered with a monolayer of Fe atoms. The total energy of the system is computed as the function of the height of the W adatom. Our result shows that the W atom first adsorbs on top of the Fe monolayer. Then the W atom can replace one of the Fe atoms through a path with a moderate energy barrier and reduce its energy further. This intermediate site makes the adsorption (and desorption) of W atoms a two-step process in the presence of Fe atoms and lowers the overall adsorption energy by nearly 2.4 eV. The Fe atoms also provide a surface for W atoms to adsorb facilitating the diffusion of W atoms. The combination of these two effects result in a much more efficient desorption and diffusion of W atoms in the presence of Fe atoms. Our result provides a fundamental mechanism that can explain the activated sintering of tungsten by Fe atoms.Comment: 9 pages, 2 figure

Kaluza-Klein masses of bulk fields with general boundary conditions in AdS5_5

Recently bulk Randall-Sundrum theories with the gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ have drawn a lot of interest as an alternative to electroweak symmetry breaking mechanism. These models are in better agreement with electroweak precision data since custodial isospin symmetry on the IR brane is protected by the extended bulk gauge symmetry. We comprehensively study, in the S^1/\ZZ orbifold, the bulk gauge and fermion fields with the general boundary conditions as well as the bulk and localized mass terms. Master equations to determine the Kaluza-Klein (KK) mass spectra are derived without any approximation, which is an important basic step for various phenomenologies at high energy colliders. The correspondence between orbifold boundary conditions and localized mass terms is demonstrated not only in the gauge sector but also in the fermion sector. As the localized mass increases, the first KK fermion mass is shown to decrease while the first KK gauge boson mass to increase. The degree of gauge coupling universality violation is computed to be small in most parameter space, and its correlation with the mass difference between the top quark and light quark KK mode is also studied.Comment: 25 pages with 10 figures, Final version accepted by PR

Some Grüss' Type Inequalities in 2-Inner Product Spaces and Applications for Determinantal Integral Inequalities

Some new Grüss type inequalities in 2-inner product spaces are given. Using this framework, some determinantal integral inequalities for synchronous functions are also derived

Charge-Focusing Readout of Time Projection Chambers

Time projection chambers (TPCs) have found a wide range of applications in particle physics, nuclear physics, and homeland security. For TPCs with high-resolution readout, the readout electronics often dominate the price of the final detector. We have developed a novel method which could be used to build large-scale detectors while limiting the necessary readout area. By focusing the drift charge with static electric fields, we would allow a small area of electronics to be sensitive to particle detection for a much larger detector volume. The resulting cost reduction could be important in areas of research which demand large-scale detectors, including dark matter searches and detection of special nuclear material. We present simulations made using the software package Garfield of a focusing structure to be used with a prototype TPC with pixel readout. This design should enable significant focusing while retaining directional sensitivity to incoming particles. We also present first experimental results and compare them with simulation.Comment: 5 pages, 17 figures, Presented at IEEE Nuclear Science Symposium 201

Searching for rotating galaxy clusters in SDSS and 2dFGRS

We present a result of searching for galaxy clusters that show an indication of global rotation using a spectroscopic sample of galaxies in SDSS and 2dFGRS. We have determined the member galaxies of 899 Abell clusters covered in SDSS and 2dFGRS using the redshift and the positional data of galaxies, and have estimated the ratio of the cluster rotation amplitude to the cluster velocity dispersion and the velocity gradient across the cluster. We have found 12 tentative rotating clusters that have large ratios of rotation amplitude to dispersion and large velocity gradients. We have determined the morphological parameters for 12 tentative rotating clusters using the positional information of the member galaxies: the ellipticity of the dispersion ellipse is in the range of 0.08$-$0.57, and the position angle of major or minor axis does not appear to be related to the position angle of rotation axis. We have investigated the substructures in the sample of tentative rotating clusters, finding from the Dressler-Shectman plots that the majority (9 out of 12) of clusters show an evidence of substructure due to the spatially correlated velocities of galaxies. We have selected six probable rotating clusters (A0954, A1139, A1399, A2162, A2169, and A2366) that show a single number density peak around the cluster center with a spatial segregation of the high and low velocity galaxies. We have found no strong evidences of a recent merging for the probable rotating clusters: the probable rotating clusters do not deviate significantly from the relation of the X-ray luminosity and the velocity dispersion or the virial mass of the clusters, and two probable rotating clusters (A0954 and A1399) have small values of the peculiar velocities and the clustercentric distances of the brightest cluster galaxies.Comment: 33 pages, 9 figures. To appear in Ap