28,545 research outputs found
Top Quark Yukawa Couplings and New Physics
We discuss associated production of a Higgs boson with a pair of
quarks at a future high energy collider. The process is particularly sensitive to the presence of new physics and we
consider the MSSM and models with extra dimensions at the scale as
examples.Comment: Talk given at the 5th International Collider Workshop (LCWS 2000),
Fermilab, Batavia, Il, Oct 24-28, 200
Next-to-Leading Order Results for t-tbar-h Production at the Tevatron
We compute the O(alpha_s^3) total cross section for the process (p pbar -> t
tbar h) in the Standard Model, at \sqrt{s}=2 TeV. The next-to-leading order
corrections drastically reduce the renormalization and factorization scale
dependence of the Born cross section and slightly decrease the total cross
section for renormalization and factorization scales between m_t and 2m_t.Comment: 5 pages, 5 figures, REVTeX, submitted to Phys. Rev. Let
The use of the plane wave fluid-structure interaction loading approximation in NASTRAN
The Plane Wave Approximation (PWA) is widely used in finite element analysis to implement the loading generated by an underwater shock wave. The method required to implement the PWA in NASTRAN is presented along with example problems. A theoretical background is provided and the limitations of the PWA are discussed
Transience and recurrence of random walks on percolation clusters in an ultrametric space
We study existence of percolation in the hierarchical group of order ,
which is an ultrametric space, and transience and recurrence of random walks on
the percolation clusters. The connection probability on the hierarchical group
for two points separated by distance is of the form , with , non-negative constants , and . Percolation was proved in Dawson and Gorostiza
(2013) for , with
. In this paper we improve the result for the critical case by
showing percolation for . We use a renormalization method of the type
in the previous paper in a new way which is more intrinsic to the model. The
proof involves ultrametric random graphs (described in the Introduction). The
results for simple (nearest neighbour) random walks on the percolation clusters
are: in the case the walk is transient, and in the critical case
, there exists a critical
such that the walk is recurrent for and transient for
. The proofs involve graph diameters, path lengths, and
electric circuit theory. Some comparisons are made with behaviours of random
walks on long-range percolation clusters in the one-dimensional Euclidean
lattice.Comment: 27 page
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Evolution: functional evolution of nuclear structure.
The evolution of the nucleus, the defining feature of eukaryotic cells, was long shrouded in speculation and mystery. There is now strong evidence that nuclear pore complexes (NPCs) and nuclear membranes coevolved with the endomembrane system, and that the last eukaryotic common ancestor (LECA) had fully functional NPCs. Recent studies have identified many components of the nuclear envelope in living Opisthokonts, the eukaryotic supergroup that includes fungi and metazoan animals. These components include diverse chromatin-binding membrane proteins, and membrane proteins with adhesive lumenal domains that may have contributed to the evolution of nuclear membrane architecture. Further discoveries about the nucleoskeleton suggest that the evolution of nuclear structure was tightly coupled to genome partitioning during mitosis
Gallium phosphide high temperature diodes
High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics
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