21,376 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
SUSY QCD Corrections to Higgs-b Production : Is the \Delta_b Approximation Accurate?
The associated production of a Higgs boson with a b quark is a discovery
channel for the lightest MSSM neutral Higgs boson. We consider the SUSY QCD
contributions from squarks and gluinos and discuss the decoupling properties of
these effects. A detailed comparison of our exact order(alpha_s) results with
those of a widely used effective Lagrangian approach, the \Delta_b
approximation, is presented. The \Delta_b approximation is shown to accurately
reproduce the exact one-loop SQCD result to within a few percent over a wide
range of parameter space.Comment: figures added, version to be published in Phys Rev
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
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
Experimental Spinal Fusion With Recombinant Human Bone Morphogenetic Protein-2 Without Decortication of Osseous Elements
Study Design. L4-L5 intertransverse process fusions were produced with 58 ÎŒg, 230 ÎŒg, or 920 ÎŒg of recombinant human bone morphogenetic protein-2 in 20 dogs. Eleven had traditional decortication of posterior elements before insertion of the implant. Nine were left undecorticated. All animals were evaluated 3 months after surgery.
Objectives. To determine whether decortication is a prerequisite for successful fusion in the presence of osteoinductive proteins such as bone morphogenetic protein-2.
Summary of Background Data. Recombinant osteoinductive proteins can induce de novo bone in ectopic soft-tissue sites in the absence of bone marrow elements. Traditional methods for achieving spinal fusion rely on exposure of bone marrow through decortication to facilitate osteogenesis. It is hypothesized that the presence of an implanted osteoinductive protein obviates the need for exposure and release of host inductive factors.
Methods. Recombinant human bone morphogenetic protein-2-induced intertransverse process fusions were performed with and without decortication. Fusion sites were evaluated by computed tomography imaging, high-resolution radiography, manual testing, mechanical testing, and histologic analysis.
Results. One hundred percent of decorticated spines and 89% of undecorticated spines were clinically fused by 3 months. Ninety-one percent of decorticated spines and 78% of undecorticated specimens exhibited bilateral transverse process osseous bridging. The only spines that failed to achieve solid bilateral arthrodesis were in the lowest dose group. With the higher two doses, there was histologic evidence of osseous continuity between the fusion mass and undecorticated transverse processes.
Conclusions. There were no statistical differences in clinical and radiographic fusion rates between decorticated and undecorticated sites. With higher doses of recombinant human bone morphogenetic protein-2, there was little histologic distinction between fusions in decorticated versus undecorticated spines
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