17,674 research outputs found
One-loop Corrections to the S Parameter in the Four-site Model
We compute the leading chiral-logarithmic corrections to the S parameter in
the four-site Higgsless model. In addition to the usual electroweak gauge
bosons of the Standard Model, this model contains two sets of heavy charged and
neutral gauge bosons. In the continuum limit, the latter gauge bosons can be
identified with the first excited Kaluza-Klein states of the W^\pm and Z bosons
of a warped extra-dimensional model with an SU(2)_L \times SU(2)_R \times
U(1)_X bulk gauge symmetry. We consider delocalized fermions and show that the
delocalization parameter must be considerably tuned from its tree-level ideal
value in order to reconcile experimental constraints with the one-loop results.
Hence, the delocalization of fermions does not solve the problem of large
contributions to the S parameter in this class of theories and significant
contributions to S can potentially occur at one-loop.Comment: 28 pages, 7 figure
Higgs Triplets, Decoupling, and Precision Measurements
Electroweak precision data has been extensively used to constrain models
containing physics beyond that of the Standard Model. When the model contains
Higgs scalars in representations other than SU(2) singlets or doublets, and
hence rho not equal to one at tree level, a correct renormalization scheme
requires more inputs than the three needed for the Standard Model. We discuss
the connection between the renormalization of models with Higgs triplets and
the decoupling properties of the models as the mass scale for the scalar
triplet field becomes much larger than the electroweak scale. The requirements
of perturbativity of the couplings and agreement with electroweak data place
strong restrictions on models with Higgs triplets. Our results have important
implications for Little Higgs type models and other models with rho not equal
to one at tree level.Comment: 23 page
Kinetics of the reduction of metalloproteins by chromous ion
The reduction of Cu(330) in Rhus vernicifera laccase by chromous ion is 30% faster than reduction of Cu(614) at room temperature [pH 4.8, ” = 0.1 (NaCl)], and two parallel first-order paths, attributed to heterogeneity of the protein, are observed at both wavelengths. The reactions of stellacyanin, spinach and French-bean plastocyanins, and cytochrome c with chromous ion under similar conditions are faster than that with laccase by factors of 102 to 104, and are first order in protein concentration. Comparison of rates and activation parameters for the reduction of "blue" copper in laccase, stellacyanin, and the two plastocyanins indicates that reduction of the Cu(614) site in laccase may occur by intramolecular electron transfer from one of the Cu(330) sites. Our value of ÎH (17.4 kcal/mol) for the chromous ion reduction of cytochrome c is consistent with a mechanism in which major conformational changes in the protein must accompany electron transfer
Additive benefit of higher testosterone levels and vitamin D plus calcium supplementation in regard to fall risk reduction among older men and women
Summary: Higher physiologic testosterone levels among community dwelling older men and women may protect against falls, and this benefit may be further increased among those taking additional vitamin D plus calcium. Introduction: The aim of this study is to investigate sex hormone levels and fall risk in older men and women. Methods: One hundred and ninety-nine men and 246 women age 65+ living at home were followed for 3years after baseline assessment of sex hormones. Analyses controlled for several covariates, including baseline 25-hydroxyvitamin D, sex hormone binding globulin, and vitamin D plus calcium treatment (vitD+cal). Results: Compared to the lowest quartile, men and women in the highest quartile of total testosterone had a decreased odds of falling (men: ORâ=â0.22; 95% CI [0.07,0.72]/ women: ORâ=â0.34; 95% CI [0.14,0.83]); if those individuals also took vitD+cal, the fall reduction was enhanced (men: ORâ=â0.16; 95% CI [0.03,0.90] / women: ORâ=â0.15; 95% CI [0.04,0.57]). Similarly, women in the top quartile of dihydroepiandrosterone sulfate (DHEA-S) had a lower risk of falling (ORâ=â0.39; 95% CI [0.16,0.93]). Other sex hormones and SHBG did not predict falling in men or women. Conclusions: Higher testosterone levels in both genders and higher DHEA-S levels in women predicted a more than 60% lower risk of falling. With vitD+cal, the anti-fall benefit of higher physiologic testosterone levels is enhanced from 78% to 84% among men and from 66% to 85% among wome
Dark-field transmission electron microscopy and the Debye-Waller factor of graphene
Graphene's structure bears on both the material's electronic properties and
fundamental questions about long range order in two-dimensional crystals. We
present an analytic calculation of selected area electron diffraction from
multi-layer graphene and compare it with data from samples prepared by chemical
vapor deposition and mechanical exfoliation. A single layer scatters only 0.5%
of the incident electrons, so this kinematical calculation can be considered
reliable for five or fewer layers. Dark-field transmission electron micrographs
of multi-layer graphene illustrate how knowledge of the diffraction peak
intensities can be applied for rapid mapping of thickness, stacking, and grain
boundaries. The diffraction peak intensities also depend on the mean-square
displacement of atoms from their ideal lattice locations, which is
parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a
suspended monolayer of exfoliated graphene and find a result consistent with an
estimate based on the Debye model. For laboratory-scale graphene samples,
finite size effects are sufficient to stabilize the graphene lattice against
melting, indicating that ripples in the third dimension are not necessary.Comment: 10 pages, 4 figure
Er3+ doped Silica-on-Silicon using fs-laser doping process for Integrated Waveguide Amplifier Platforms
Rare earth doped waveguide amplifier (EDWA) on silica-on-silicon (SOS) platform are area of great interest for silicon integrated photonics. We report the fabrication of erbium doped silica-on-silicon (SOS) wafer-scale platforms for integrated waveguide amplifier and laser application. We used a method named- ultrafast laser plasma doping (ULPD) process on silica- on-silicon substrates using erbium doped zinc-sodium tellurite glasses (TZN) as targets. The influence of laser energy on the doping process was studied in terms of the refractive index of the waveguides formed and their photoluminescence properties. Planar slab waveguides of refractive index1.64 at 633 nm and characteristic photoluminescence lifetimes of erbium at 1535 nm wavelength emission, varying from 13.38 ms to 10.52 ms were obtained. We used higher repetition rate (10 kHz) amplified Ti-Sapphire laser with pulse duration of 45 fs for faster and efficient growth of active waveguide layer in this research
Modelling windage power loss from an enclosed spur gear
Within a gearbox the majority of transmission losses can be attributed to bearing losses, meshing losses, or losses due to windage/churning. In this paper the commercial computational fluid dynamics (CFD) code Fluent 6.2.16 is applied in a two-dimensional study of windage power loss (WPL) from a single spur gear rotating in air. By comparing CFD data to published experimental data appropriate grid density and modelling parameters are identified. The model is used to investigate how peripheral shrouding affects WPL and whether WPL can be reduced through minor modifications to tooth tip geometry.
Non-dimensional shroud spacings (ratio of gap to gear PCD) of between 0.005 and 0.05 were investigated at shaft speeds between 5000 and 20 000 r/min. Although CFD data compared reasonably well to experimental data, trends were not reproduced and an optimum shroud could not be identified. A full three-dimensional study is recommended.
Modifying the tooth tip by adding a small chamfer on the leading edge reduced WPL by ~6 per cent. A small fillet increased total WPL by a similar amount suggesting that WPL may increase as a gear wears. This preliminary study suggests further work in this area would be beneficial
The roots of "Western European societal evolution". A concept of Europe by JenĆ SzƱcs
JenĆ SzƱcs wrote his essay entitled Sketch on the three regions of Europe in the early 1980s in Hungary. During these years, a historically well-argued opinion emphasising a substantial difference between Central European and Eastern European societies was warmly received in various circles of the political opposition. In a wider European perspective SzƱcs used the old âliberty toposâ which claims that the history of Europe is no other than the fulfillment of liberty. In his Sketch, SzƱcs does not only concentrate on questions concerning the Middle Ages in Western Europe. Yet it is this stream of thought which brought a new perspective to explaining European history. His picture of the Middle Ages represents well that there is a way to integrate all typical Western motifs of post-war self-definition into a single theory. Mainly, the âliberty motifâ, as a sign of âEuropeanismâ â in the interpretation of BibĂłâs concept, Anglo-saxon Marxists and Weberâs social theory â, developed from medieval concepts of state and society and from an analysis of economic and social structures. SzƱcsâs historical aspect was a typical intellectual product of the 1980s: this was the time when a few Central European historians started to outline non-Marxist aspects of social theory and categories of modernisation theories, but concealing them with Marxist terminology
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