19,250 research outputs found
Comment on Counterintuitive consequence of heating in strongly driven intrinsic junctions of BiSrCaCuO mesas
In a recent paper [Phys.Rev.B 81, 224518 (2010)], C. Kurter et al, analyzed
the effect of strong self-heating in large-area
BiSrCaCuO (Bi-2212) mesa structures. They conclude
that conductance peaks in their mesas occur when mesas are heated to
the superconducting critical temperature . Further on they extrapolate
this statement for all mesas, including much smaller and much better thermally
anchored mesas used in Intrinsic Tunnelling Spectroscopy (ITS). Here I show
that their conclusion does not hold neither for previously reported data, nor
even for their own mesas; the very remote extrapolation to ITS is invalid. I
also point out a number of inconsistencies and misleading references.Comment: 2 page
Degradation of multiplier phototubes exposed to spatial radiations
Degradation of multiplier phototubes exposed to spatial radiation
Information Technology Externalities: Empirical Evidence from 42 U.S. Industries
Using interindustry transaction in input-output tables, we examine Information Technology (IT) externalities in U.S. private industries over the period 1984-2000. Our empirical results show that computerization of an industry's customer and supplier industries reduces both labor and material costs of the industry. Moreover, cost savings driven by supplier industries are larger than those driven by customer industries. We also find that industries in the services sector enjoy more benefits from IT spillovers than industries in other sectors because of their high IT capital intensity and composition of interindustry transaction. Decomposition of total factor productivity (TFP) suggests that IT externalities can explain considerable parts of TFP growth, although possible mismeasurement of output in services industries leads to exacerbated technical changes of services industries.
Do Local Analysts Know More? A Cross-Country Study of the Performance of Local Analysts and Foreign Analysts
This paper examines whether analysts resident in a country make more precise earnings forecasts for firms in that country than analysts who are not resident in that country. Using a sample of 32 countries, we find that there is an economically and statistically significant analyst local advantage even after controlling for firm and analyst characteristics. The importance of the local advantage is inversely related to the quality of the information provided by firms. In particular, the local advantage is high in countries where earnings are smoothed more, less information is disclosed by firms, and firm idiosyncratic information explains a smaller fraction of stock returns. The local advantage is also negatively related to market participation by foreign investors and by institutions and positively related to holdings by insiders. U.S. investors underweight a country's stocks more in their portfolios if that country has a higher analyst local advantage.
Stability of Transonic Characteristic Discontinuities in Two-Dimensional Steady Compressible Euler Flows
For a two-dimensional steady supersonic Euler flow past a convex cornered
wall with right angle, a characteristic discontinuity (vortex sheet and/or
entropy wave) is generated, which separates the supersonic flow from the gas at
rest (hence subsonic). We proved that such a transonic characteristic
discontinuity is structurally stable under small perturbations of the upstream
supersonic flow in . The existence of a weak entropy solution and Lipschitz
continuous free boundary (i.e. characteristic discontinuity) is established. To
achieve this, the problem is formulated as a free boundary problem for a
nonstrictly hyperbolic system of conservation laws; and the free boundary
problem is then solved by analyzing nonlinear wave interactions and employing
the front tracking method.Comment: 26 pages, 3 figure
Stretching Homopolymers
Force induced stretching of polymers is important in a variety of contexts.
We have used theory and simulations to describe the response of homopolymers,
with monomers, to force () in good and poor solvents. In good solvents
and for {{sufficiently large}} we show, in accord with scaling predictions,
that the mean extension along the axis for small , and
(the Pincus regime) for intermediate values of . The
theoretical predictions for \la Z\ra as a function of are in excellent
agreement with simulations for N=100 and 1600. However, even with N=1600, the
expected Pincus regime is not observed due to the the breakdown of the
assumptions in the blob picture for finite . {{We predict the Pincus scaling
in a good solvent will be observed for }}. The force-dependent
structure factors for a polymer in a poor solvent show that there are a
hierarchy of structures, depending on the nature of the solvent. For a weakly
hydrophobic polymer, various structures (ideal conformations, self-avoiding
chains, globules, and rods) emerge on distinct length scales as is varied.
A strongly hydrophobic polymer remains globular as long as is less than a
critical value . Above , an abrupt first order transition to a
rod-like structure occurs. Our predictions can be tested using single molecule
experiments.Comment: 24 pages, 7 figure
125 GeV Higgs as a pseudo-Goldstone boson in supersymmetry with vector-like matters
We propose a possibility of the 125 GeV Higgs being a pseudo-Goldstone boson
in supersymmetry with extra vector-like fermions. Higgs mass is obtained from
loops of top quark and vector-like fermions from the global symmetry breaking
scale f at around TeV. The mu, Bmu/mu \sim f are generated from the dynamics of
global symmetry breaking and the Higgs quartic coupling vanishes at f as tan
beta \simeq 1. The relation of msoft \sim with f \sim mu \sim m_soft
\sim TeV is obtained and large mu does not cause a fine tuning for the
electroweak symmetry breaking. The Higgs to di-photon rate can be enhanced from
the loop of uncolored vector-like matters. The stability problem of Higgs
potential with vector-like fermions can be nicely cured by the UV completion
with the Goldstone picture.Comment: 28 pages, 8 figure
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