181 research outputs found
The S-parameter in Holographic Technicolor Models
We study the S parameter, considering especially its sign, in models of
electroweak symmetry breaking (EWSB) in extra dimensions, with fermions
localized near the UV brane. Such models are conjectured to be dual to 4D
strong dynamics triggering EWSB. The motivation for such a study is that a
negative value of S can significantly ameliorate the constraints from
electroweak precision data on these models, allowing lower mass scales (TeV or
below) for the new particles and leading to easier discovery at the LHC. We
first extend an earlier proof of S>0 for EWSB by boundary conditions in
arbitrary metric to the case of general kinetic functions for the gauge fields
or arbitrary kinetic mixing. We then consider EWSB in the bulk by a Higgs VEV
showing that S is positive for arbitrary metric and Higgs profile, assuming
that the effects from higher-dimensional operators in the 5D theory are
sub-leading and can therefore be neglected. For the specific case of AdS_5 with
a power law Higgs profile, we also show that S ~ + O(1), including effects of
possible kinetic mixing from higher-dimensional operator (of NDA size) in the
theory. Therefore, our work strongly suggests that S is positive in
calculable models in extra dimensions.Comment: 21 pages, 2 figures. v2: references adde
Wilson Loops in string duals of Walking and Flavored Systems
We consider the VEV of Wilson loop operators by studying the behavior of
string probes in solutions of Type IIB string theory generated by Nc D5 branes
wrapped on an internal manifold. In particular, we focus on solutions to the
background equations that are dual to field theories with a walking gauge
coupling as well as for flavored systems. We present in detail our walking
solution and emphasize various general aspects of the procedure to study Wilson
loops using string duals. We discuss the special features that the strings show
when probing the region associated with the walking of the field theory
coupling.Comment: 28 pages. Various figures. Version to be published
Holographic Technidilaton and LHC searches
We analyze in detail the phenomenology of a model of dynamical electroweak
symmetry breaking inspired by walking technicolor, by using the techniques of
the bottom-up approach to holography. The model admits a light composite scalar
state, the dilaton, in the spectrum. We focus on regions of parameter space for
which the mass of such dilaton is 125 GeV, and for which the bounds on the
precision electroweak parameter S are satisfied. This requires that the
next-to-lightest composite state is the techni-rho meson, with a mass larger
than 2.3 TeV. We compute the couplings controlling the decay rates of the
dilaton to two photons and to two (real or virtual) Z and W bosons. For generic
choices of the parameters, we find a suppression of the decay into heavy gauge
bosons, in respect to the analog decay of the standard-model Higgs. We find a
dramatic effect on the decay into photons, which can be both strongly
suppressed or strongly enhanced, the latter case corresponding to the large-N
regime of the dual theory. There is a correlation between this decay rate of
the dilaton into photons and the mass splitting between the techni-rho meson
and its axial-vector partner: if the decay is enhanced in respect to the
standard-model case, then the heavy spin-1 resonances are nearly degenerate in
mass, otherwise their separation in mass is comparable to the mass scale
itself.Comment: Very minor typos corrected. References adde
Phosphoethanolamine And Omega-3 In Patients With Asthma
The effect of omega-3 (n-3) in asthma has been inconclusive. One explanation for it may be the low incorporation of these fatty acids in clinical studies. Phosphoethanolamine (PEtn) can increase the synthesis of phosphatidylethanolamine, which can, in turn, increase the incorporation of n-3 in cell membranes. The aim of this study is to evaluate the effect of synthetic PEtn in patients with asthma who are receiving n-3. This randomized, double-blind, placebo-controlled study was carried out over a two month period by using spirometry, the Asthma Control Test questionnaire (ACT) and medicine intake. Forty-one patients with asthma were studied. Twenty-one patients received n-3 daily (1.080 mg of EPA, 720 mg of DHA) and 800 mg of PEtn (PEtn group), and twenty patients received the same doses of n-3 and placebo (control group). All patients continued receiving their conventional treatment for asthma. The hospital ethics committee approved the study. Five patients of each group required systemic corticosteroids, being the total consumption, Smaller in the PEtn group (127.4 mg of prednisone/patient versus 416.0 mg of prednisone/patient in the control group, p-value = 0.0269). There were no significant differences in the changing of ATC and FEV1, as well as in the intake of formoterol or budesonide between the groups. In this study, patients who received phosphoethanolamine and omega-3 needed a Smaller dose of systemic corticosteroid for asthma control than patients who only received omega-3. However, as the trial was conducted on a Small scale, more studies are necessary.99185431854
Sequence Context Influences the Structure and Aggregation Behavior of a PolyQ Tract
Expansions of polyglutamine (polyQ) tracts in nine different proteins cause a family of neurodegenerative disorders called polyQ diseases. Because polyQ tracts are potential therapeutic targets for these pathologies there is great interest in characterizing the conformations that they adopt and in understanding how their aggregation behavior is influenced by the sequences flanking them. We used solution NMR to study at single-residue resolution a 156-residue proteolytic fragment of the androgen receptor that contains a polyQ tract associated with the disease spinobulbar muscular atrophy, also known as Kennedy disease. Our findings indicate that a Leu-rich region preceding the polyQ tract causes it to become α-helical and appears to protect the protein against aggregation, which represents a new, to our knowledge, mechanism by which sequence context can minimize the deleterious properties of these repetitive regions. Our results have implications for drug discovery for polyQ diseases because they suggest that the residues flanking these repetitive sequences may represent viable therapeutic targets
Scalar Loops in Little Higgs Models
Loops of the scalar particles present in Little Higgs models generate
radiatively scalar operators that have been overlooked before in Little Higgs
analyses. We compute them using a technique, recently proposed to deal with
scalar fluctuations in non-linear sigma models, that greatly simplifies the
calculation. In particular models some of these operators are not induced by
loops of gauge bosons or fermions, are consistent with the Little Higgs
symmetries that protect the Higgs boson mass, and must also be included in the
Lagrangian. In general, scalar loops multiplicatively renormalize the
tree-level scalar operators, O_S -> O_S [1- N \Lambda^2/(4\pi f)^2] with large
N (e.g. N ~ 20 for the Littlest Higgs), suggesting a true UV cutoff \Lambda < 4
\pi f/\sqrt{N} significantly below the estimate 4\pi f of naive dimensional
analysis. This can have important implications for the phenomenology and
viability of Little Higgs models.Comment: 28 pages, LaTe
Supersymmetric origin of a low CP asymmetry
We show that general Minimal Supersymmetric extensions of the Standard Model
(MSSM) allow for a CP asymmetry in B --> J/psi K(S) well bellow the SM
expectations with dominant Supersymmetric contributions to epsilon_K and
epsilon'/epsilon. Indeed, we provide an explicit example of an MSSM with
non-universal soft breaking terms fully consistent with the low results of this
asymmetry recently announced by Babar and Belle collaborations.Comment: 6 pages, no figures. Reference added, typos correcte
Phosphoethanolamine and omega-3 in patients with asthma
The effect of omega-3 (n-3) in asthma has been inconclusive. One explanation for it may be the low incorporation of these fatty acids in clinical studies. Phosphoethanolamine (PEtn) can increase the synthesis of phosphatidylethanolamine, which can, in turn, increase the incorporation of n-3 in cell membranes. The aim of this study is to evaluate the effect of synthetic PEtn in patients with asthma who are receiving n-3. This randomized, double-blind, placebo-controlled study was carried out over a two month period by using spirometry, the Asthma Control Test questionnaire (ACT) and medicine intake. Forty-one patients with asthma were studied. Twenty-one patients received n-3 daily (1.080 mg of EPA, 720 mg of DHA) and 800 mg of PEtn (PEtn group), and twenty patients received the same doses of n-3 and placebo (control group). All patients continued receiving their conventional treatment for asthma. The hospital ethics committee approved the study. Five patients of each group required systemic corticosteroids, being the total consumption, smaller in the PEtn group (127.4 mg of prednisone/patient versus 416.0 mg of prednisone/patient in the control group, p-value = 0.0269). There were no significant differences in the changing of ATC and FEV1, as well as in the intake of formoterol or budesonide between the groups. In this study, patients who received phosphoethanolamine and omega-3 needed a smaller dose of systemic corticosteroid for asthma control than patients who only received omega-3. However, as the trial was conducted on a small scale, more studies are necessary
Axion and neutrino physics from anomaly cancellation
It has been recently shown that the requirement of anomaly cancellation in a
(non-supersymmetric) six-dimensional version of the standard model fixes the
field content to the known three generations. We discuss the phenomenological
consequences of the cancellation of the local anomalies: the strong CP problem
is solved and the fundamental scale of the theory is bounded by the physics of
the axion. Neutrinos acquire a mass in the range suggested by atmospheric
experiments.Comment: 9 pages, RevTeX
ImplicaçÔes da interação genĂłtipos X ambientes na seleção entre de progĂȘnies do feijoeiro.
O mĂ©todo de condução da população segregante mais utilizado no programa de melhoramento do feijoeiro na Universidade Federal de Lavras (UFLA) Ă© o do bulk dentro de progĂȘnies F2. Nas sucessivas geraçÔes as progĂȘnies sĂŁo avaliadas em experimentos em uma ou mais safras. O que se questiona Ă© qual o efeito da interação progĂȘnies x ambientes na seleção realizada. O objetivo desse trabalho foi o de estimar parĂąmetros genĂ©ticos e fenotĂpicos de progĂȘnies avaliadas por algumas geraçÔes, visando a orientação dos melhoristas com relação ao processo seletivo com o decorrer das geraçÔes
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