663 research outputs found
Strain bursts in plastically deforming Molybdenum micro- and nanopillars
Plastic deformation of micron and sub-micron scale specimens is characterized
by intermittent sequences of large strain bursts (dislocation avalanches) which
are separated by regions of near-elastic loading. In the present investigation
we perform a statistical characterization of strain bursts observed in
stress-controlled compressive deformation of monocrystalline Molybdenum
micropillars. We characterize the bursts in terms of the associated elongation
increments and peak deformation rates, and demonstrate that these quantities
follow power-law distributions that do not depend on specimen orientation or
stress rate. We also investigate the statistics of stress increments in between
the bursts, which are found to be Weibull distributed and exhibit a
characteristic size effect. We discuss our findings in view of observations of
deformation bursts in other materials, such as face-centered cubic and
hexagonal metals.Comment: 14 pages, 8 figures, submitted to Phil Ma
CP violation in gauge theories
We define the CP transformation properties of scalars, fermions and vectors
in a gauge theory and show that only three types of interactions can lead to CP
violation: scalar interactions, fermion-scalar interactions and
associated with the strong CP problem and which involve only the gauge fields.
For technicolor theories this implies the absence of CP violation within
perturbation theory.Comment: 5 pages, 1 figure, revtex and epsf require
Addendum to: Search for anomalous top-gluon couplings at LHC revisited
In our latest paper "Search for anomalous top-gluon couplings at LHC
revisited" in Eur. Phys. J. C65 (2010), 127-135 (arXiv:0910.3049 [hep-ph]), we
studied possible effects of nonstandard top-gluon couplings through the
chromoelectric and chromomagnetic moments of the top quark using the total
cross section of ppbar/pp --> ttbar X at Tevatron/LHC. There we pointed out
that LHC data could give a stronger constraint on those two parameters, which
would be hard to obtain from Tevatron data alone. We show here the first CMS
measurement of this cross section actually makes it possible.Comment: 5 pages, 1 figure, LaTeX2e, Final version (to appear in Eur. Phys. C
Four-Fermi Effective Operators in Top-Quark Production and Decay
Effects of four-Fermi-type new interactions are studied in top-quark pair
production and their subsequent decays at future e^+e^- colliders.
Secondary-lepton-energy distributions are calculated for arbitrary longitudinal
beam polarizations. An optimal-observables procedure is applied for the
determination of new parameters.Comment: Polarized e^- plus unpolarized e^+ collisions were include
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Adhesion and Cellular Compatibility of Silicone-Based Skin Adhesives
Pressure-sensitive adhesives based on silicone materials have emerging potential as adhesives in healthcare products, in particular for gentle skin adhesives. To this end, adhesion to rough skin and biocompatibility are crucial factors for a successful implementation. In this study, the mechanical, adhesive, and biological properties of the two-component poly(dimethylsiloxane) Soft Skin Adhesive MG 7-9800 (SSA, Dow Corning) have been investigated and compared to Sylgard 184. Different mixing ratios of SSA's components allow for tuning of the shear modulus, thereby modifying the adhesive properties of the polymer. To give a comprehensive insight, the authors have analyzed the interplay between pull-off stress, adhesion energy, and stretch of the adhesive films on smooth and rough surfaces. The focus is placed on the effects of substrate roughness and on low pressure oxygen plasma treatment of the adhesive films. SSA shows superior biocompatibility in in vitro cell culture experiments. High pull-off stresses in the range of 3 N cm−2 on a rough surface are achieved, promising broad application spectra for SSA-based healthcare products
Proposing "b-Parity" - a New Approximate Quantum Number in Inclusive b-jet Production - as an Efficient Probe of New Flavor Physics
We consider the inclusive reaction \ell^+ \ell^- -> nb +X (n = number of
b-jets) in lepton colliders for which we propose a useful approximately
conserved quantum number b_P=(-1)^n that we call b-Parity (b_P). We make the
observation that the Standard Model (SM) is essentially b_P-even since SM
b_P-violating signals are necessarily CKM suppressed. In contrast new flavor
physics can produce b_P=-1 signals whose only significant SM background is due
to b-jet misidentification. Thus, we show that b-jet counting, which relies
primarily on b-tagging, becomes a very simple and sensitive probe of new flavor
physics (i.e., of b_P-violation).Comment: 5 pages using revtex, 2 figures embadded in the text using epsfig. As
will appear in Phys.Rev.Lett.. Considerable improvement was made in the
background calculation as compared to version 1, by including purity
parameters, QCD effects and 4-jets processe
Anomalous Neutrino Reactions at HERA
We study the sensitivity of HERA to new physics using the helicity suppressed
reaction , where the final neutrino can be a standard
model one or a heavy neutrino. The approach is model independent and is based
on an effective lagrangian parametrization. It is shown that HERA will put
significant bounds on the scale of new physics, though, in general, these are
more modest than previously thought. If deviations from the standard model are
observed in the above processes, future colliders such as the SSC and LHC will
be able to directly probe the physics responsible for these discrepancies}Comment: 11 Pages + 2 figures is TOPDRAWER (included at the end or available
by mail). Report UCRHEP-T113 (requires the macropackage PHYZZX). A line in
the TeX file requesting an input file has been removed, it caused problem
A Model-independent Description of New Physics effects in e+e- to t tbar
We study the potential of a future collider for the search of
anomalous gamma t t bar and Z t t bar couplings, assuming that CP-invariance
holds. This is done in a model-independent way, considering that all six
possible couplings do appear. Two experimental situations are envisaged, with
and without electron beam polarization. Observability limits in the form of
domains in the 6-dimensional parameter space are established. Illustrations for
specific constrained models are also presented and implications for new physics
searches are discussed.Comment: 26 pages and 5 figures. e-mail: [email protected]
Transmission of Foot-and-Mouth Disease Virus during the Incubation Period in Pigs.
Understanding the quantitative characteristics of a pathogen's capability to transmit during distinct phases of infection is important to enable accurate predictions of the spread and impact of a disease outbreak. In the current investigation, the potential for transmission of foot-and-mouth disease virus (FMDV) during the incubation (preclinical) period of infection was investigated in seven groups of pigs that were sequentially exposed to a group of donor pigs that were infected by simulated-natural inoculation. Contact-exposed pigs were comingled with infected donors through successive 8-h time slots spanning from 8 to 64 h post-inoculation (hpi) of the donor pigs. The transition from latent to infectious periods in the donor pigs was clearly defined by successful transmission of foot-and-mouth disease (FMD) to all contact pigs that were exposed to the donors from 24 hpi and later. This onset of infectiousness occurred concurrent with detection of viremia, but approximately 24 h prior to the first appearance of clinical signs of FMD in the donors. Thus, the latent period of infection ended approximately 24 h before the end of the incubation period. There were significant differences between contact-exposed groups in the time elapsed from virus exposure to the first detection of FMDV shedding, viremia, and clinical lesions. Specifically, the onset and progression of clinical FMD were more rapid in pigs that had been exposed to the donor pigs during more advanced phases of disease, suggesting that these animals had received a higher effective challenge dose. These results demonstrate transmission and dissemination of FMD within groups of pigs during the incubation period of infection. Furthermore, these findings suggest that under current conditions, shedding of FMDV in oropharyngeal fluids is a more precise proxy for FMDV infectiousness than clinical signs of infection. These findings may impact modeling of the propagation of FMD outbreaks that initiate in pig holdings and should be considered when designing FMD control strategies
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