3,567 research outputs found
Constraints on anomalous gauge couplings from present LEP1 and future LEP2, BNL data
We analyze, in a rather general model where anomalous triple gauge couplings
are present, the visible effects in R (measured at LEP1), in W pair
production (to be measured at LEP2) and in the muon anomalous magnetic moment
(to be measured at BNL). From the combination of the three experiments a
remarkable improvement on the pure LEP2 constraints is obtained.Comment: 10 pages and 6 figures. e-mail: [email protected]
Launch window analysis of satellites in high eccentricity or large circular orbits
Numerical methods and computer programs for studying the stability and evolution of orbits of large eccentricity are presented. Methods for determining launch windows and target dates are developed. Mathematical models are prepared to analyze the characteristics of specific missions
The roughness of stylolites: Implications of 3D high resolution topography measurements
Stylolites are natural pressure-dissolution surfaces in sedimentary rocks. We
present 3D high resolution measurements at laboratory scales of their complex
roughness. The topography is shown to be described by a self-affine scaling
invariance. At large scales, the Hurst exponent is and
very different from that at small scales where . A
cross-over length scale at around \L_c =1~mm is well characterized.
Measurements are consistent with a Langevin equation that describes the growth
of a stylolitic interface as a competition between stabilizing long range
elastic interactions at large scales or local surface tension effects at small
scales and a destabilizing quenched material disorder.Comment: 4 pages, 4 figure
Top quark production at future lepton colliders in the asymptotic regime
The production of a tt(bar) pair from lepton-antilepton annihilation is
considered for values of the center of mass energy much larger than the top
mass, typically of the few TeV size. In this regime a number of simplifications
occurs that allows to derive the leading asymptotic terms of various
observables using the same theoretical description that was used for light
quark production. Explicit examples are shown for the Standard Model and the
Minimal Supersymmetric Standard Model cases.Comment: 20 pages and 13 figures. e-mail: [email protected]
Single production of excited electrons at future e^-e^+, ep and pp colliders
We analyzed the potential of the LC with TeV, LCLHC
based ep collider with TeV and LHC with TeV to
search for excited electrons through transition magnetic type couplings with
gauge bosons. The signal and corresponding backgrounds
are studied in detail.Comment: 11 pages, 11 figures, 3 table
Prospects for near-infrared characterisation of hot Jupiters with VSI
In this paper, we study the feasibility of obtaining near-infrared spectra of
bright extrasolar planets with the 2nd generation VLTI Spectro-Imager
instrument (VSI), which has the required angular resolution to resolve nearby
hot Extrasolar Giant Planets (EGPs) from their host stars. Taking into account
fundamental noises, we simulate closure phase measurements of several
extrasolar systems using four 8-m telescopes at the VLT and a low spectral
resolution (R = 100). Synthetic planetary spectra from T. Barman are used as an
input. Standard chi2-fitting methods are then used to reconstruct planetary
spectra from the simulated data. These simulations show that low-resolution
spectra in the H and K bands can be retrieved with a good fidelity for half a
dozen targets in a reasonable observing time (about 10 hours, spread over a few
nights). Such observations would strongly constrain the planetary temperature
and albedo, the energy redistribution mechanisms, as well as the chemical
composition of their atmospheres. Systematic errors, not included in our
simulations, could be a serious limitation to these performance estimations.
The use of integrated optics is however expected to provide the required
instrumental stability (around 10^-4 on the closure phase) to enable the first
thorough characterisation of extrasolar planetary emission spectra in the
near-infrared.Comment: 10 pages, 8 figures, Proc. SPIE conference 7013 "Optical and Infrared
Interferometry" (Marseille 2008
A numerical approach for modelling thin cracked plates with XFEM
The modelization of bending plates with through the thickness cracks is investigated. We consider the Kirchhoff-Love plate model which is valid for very thin plates. We apply the eXtended Finite Element Method (XFEM) strategy: enrichment of the finite element space with the asymptotic bending and with the discontinuity across the crack. We present two variants and their numerical validations and also a numerical computation of the stress intensity factors
Bounds on universal new physics effects from fermion-antifermion production at LEP2
We consider lepton-antilepton annihilation into a fermion-antifermion pair at
variable c.m. energy. We propose for this process a simple parametrization of
the virtual effects of the most general model of new physics of
\underline{universal} type. This parametrization is based on a recent approach,
that uses the experimental results of LEP1, SLC as theoretical input. It
introduces \underline{three} functions whose energy dependence is argued to be
smooth and, in first approximation, negligible. A couple of representative
models of new physics are considered, as a support of the previous claim.
Explicit bounds are then derived for this type of new physics from the
available LEP2 data, and a discussion is given of the relevance in this respect
of the different experimental measurements. The method is then extended to
treat the case of two particularly simple models of {\it non universal} type,
for which it is possible to draw analogous conclusions.Comment: 15 pages, 3 tables and 4 figures. e-mail: [email protected]
Associated tW production at LHC: a complete calculation of electroweak supersymmetric effects at one loop
We compute, in the MSSM framework, the total electroweak contributions at one
loop for the process pp -> tW+X, initiated by the parton process bg -> tW. The
supersymmetric effect is analyzed for various choices of the SUSY benchmark
points. Choosing realistic unpolarized and polarized experimental quantities,
we show the size of the various effects and discuss their dependence on the
MSSM parameters.Comment: 32 pages, 9 eps figure
Mitochondria Retrograde Signaling and the UPR mt: Where Are We in Mammals?
Mitochondrial unfolded protein response is a form of retrograde signaling that contributes to ensuring the maintenance of quality control of mitochondria, allowing functional integrity of the mitochondrial proteome. When misfolded proteins or unassembled complexes accumulate beyond the folding capacity, it leads to alteration of proteostasis, damages, and organelle/cell dysfunction. Extensively studied for the ER, it was recently reported that this kind of signaling for mitochondrion would also be able to communicate with the nucleus in response to impaired proteostasis. The mitochondrial unfolded protein response (UPR(mt)) is activated in response to different types and levels of stress, especially in conditions where unfolded or misfolded mitochondrial proteins accumulate and aggregate. A specific UPR(mt) could thus be initiated to boost folding and degradation capacity in response to unfolded and aggregated protein accumulation. Although first described in mammals, the UPR(mt) was mainly studied in Caenorhabditis elegans, and accumulating evidence suggests that mechanisms triggered in response to a UPR(mt) might be different in C. elegans and mammals. In this review, we discuss and integrate recent data from the literature to address whether the UPR(mt) is relevant to mitochondrial homeostasis in mammals and to analyze the putative role of integrated stress response (ISR) activation in response to the inhibition of mtDNA expression and/or accumulation of mitochondrial mis/unfolded proteins
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