2,556 research outputs found
Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model
We discuss the main features of dilaton interactions for fundamental and
effective dilaton fields. In particular, we elaborate on the various ways in
which dilatons can couple to the Standard Model and on the role played by the
conformal anomaly as a way to characterize their interactions. In the case of a
dilaton derived from a metric compactification (graviscalar), we present the
structure of the radiative corrections to its decay into two photons, a photon
and a , two gauge bosons and two gluons, together with their
renormalization properties. We prove that, in the electroweak sector, the
renormalization of the theory is guaranteed only if the Higgs is conformally
coupled. For such a dilaton, its coupling to the trace anomaly is quite
general, and determines, for instance, an enhancement of its decay rates into
two photons and two gluons. We then turn our attention to theories containing a
non-gravitational (effective) dilaton, which, in our perturbative analysis,
manifests as a pseudo-Nambu Goldstone mode of the dilatation current ().
The infrared coupling of such a state to the two-photons and to the two-gluons
sector, and the corresponding anomaly enhancements of its decay rates in these
channels, is critically analyzed.Comment: Revised version, 42 pages, 5 figure
Genetic enrichment of cardiomyocytes derived from mouse embryonic stem cells
Pluripotent embryonic stem cells (ESC) have the ability to differentiate into a variety of cell lineages in vitro, including cardiomyocytes. Successful applications of ESC-derived cardiomyocytes in cell therapy and tissue engineering were limited by difficulties in selecting the desired cells from the heterogeneous cell population. We describe a simple method to generate relatively pure cardiomyocytes from mouse ESCs. A construct comprising mouse cardiac α-myosin heavy chain (MHC) promoter driving the neomycin resistance gene and SV40 promoter driving the hygromycin resistant gene designated pMHCneo/ SV40-hygro, was stably transfected into mouse ESCs. The transgenic ESC line, designated MN6 retained the undifferentiated state and the potential of cardiogenic differentiation. After G418 selection, more than 99% of cells expressed α-sarcomeric actin. Immunocytological and ultrastructural analysis demonstrated that, the selected cardiomyocytes were highly differentiated. Our results represent a simple genetic manipulation used to product essentially pure cardiomyocytes from differentiating ESCs. It may facilitate the development of cell therapy in heart diseases.Key words: Embryonic stem cells, α-myosin heavy chain promoter, cardiomyocytes, differentiation, genetic enrichment
Low-Energy Signals from Kinetic Mixing with a Warped Abelian Hidden Sector
We investigate the detailed phenomenology of a light Abelian hidden sector in
the Randall-Sundrum framework. Relative to other works with light hidden
sectors, the main new feature is a tower of hidden Kaluza-Klein vectors that
kinetically mix with the Standard Model photon and Z. We investigate the decay
properties of the hidden sector fields in some detail, and develop an approach
for calculating processes initiated on the ultraviolet brane of a warped space
with large injection momentum relative to the infrared scale. Using these
results, we determine the detailed bounds on the light warped hidden sector
from precision electroweak measurements and low-energy experiments. We find
viable regions of parameter space that lead to significant production rates for
several of the hidden Kaluza-Klein vectors in meson factories and fixed-target
experiments. This offers the possibility of exploring the structure of an extra
spacetime dimension with lower-energy probes.Comment: (1+32) Pages, 13 Figures. v2: JHEP version (minor modifications,
results unchanged
LRP16 Integrates into NF-κB Transcriptional Complex and Is Required for Its Functional Activation
BACKGROUND: Nuclear factor κB (NF-κB)-mediated pathways have been widely implicated in cell survival, development and tumor progression. Although the molecular events of determining NF-κB translocation from cytoplasm to nucleus have been extensively documented, the regulatory mechanisms of NF-κB activity inside the nucleus are still poorly understood. Being a special member of macro domain proteins, LRP16 was previously identified as a coactivator of both estrogen receptor and androgen receptor, and as an interactor of NF-κB coactivator UXT. Here, we investigated the regulatory role of LRP16 on NF-κB activation. METHODOLOGY: GST pull-down and coimmunoprecipitation (CoIP) assays assessed protein-protein interactions. The functional activity of NF-κB was assessed by luciferase assays, changes in expression of its target genes, and its DNA binding ability. Annexin V staining and flow cytometry analysis were used to evaluate cell apoptosis. Immunohistochemical staining of LRP16 and enzyme-linked immunosorbent assay-based evaluation of active NF-κB were performed on primary human gastric carcinoma samples. RESULTS: We demonstrate that LRP16 integrates into NF-κB transcriptional complex through associating with its p65 component. RNA interference knockdown of the endogenous LRP16 in cells leads to impaired NF-κB activity and significantly attenuated NF-κB-dependent gene expression. Mechanistic analysis revealed that knockdown of LRP16 did not affect tumor necrosis factor α (TNF-α)-induced nuclear translocation of NF-κB, but blunted the formation or stabilization of functional NF-κB/p300/CREB-binding protein transcription complex in the nucleus. In addition, knockdown of LRP16 also sensitizes cells to apoptosis induced by TNF-α. Finally, a positive link between LRP16 expression intensity in nuclei of tumor cells and NF-κB activity was preliminarily established in human gastric carcinoma specimens. CONCLUSIONS: Our findings not only indicate that LRP16 is a crucial regulator for NF-κB activation inside the nucleus, but also suggest that LRP16 may be an important contributor to the aberrant activation of NF-κB in tumors
Strong Double Higgs Production at the LHC
The hierarchy problem and the electroweak data, together, provide a plausible
motivation for considering a light Higgs emerging as a pseudo-Goldstone boson
from a strongly-coupled sector. In that scenario, the rates for Higgs
production and decay differ significantly from those in the Standard Model.
However, one genuine strong coupling signature is the growth with energy of the
scattering amplitudes among the Goldstone bosons, the longitudinally polarized
vector bosons as well as the Higgs boson itself. The rate for double Higgs
production in vector boson fusion is thus enhanced with respect to its
negligible rate in the SM. We study that reaction in pp collisions, where the
production of two Higgs bosons at high pT is associated with the emission of
two forward jets. We concentrate on the decay mode hh -> WW^(*)WW^(*) and study
the semi-leptonic decay chains of the W's with 2, 3 or 4 leptons in the final
states. While the 3 lepton final states are the most relevant and can lead to a
3 sigma signal significance with 300 fb^{-1} collected at a 14 TeV LHC, the two
same-sign lepton final states provide complementary information. We also
comment on the prospects for improving the detectability of double Higgs
production at the foreseen LHC energy and luminosity upgrades.Comment: 54 pages, 26 figures. v2: typos corrected, a few comments and one
table added. Version published in JHE
The Higgs as a Probe of Supersymmetric Extra Sectors
We present a general method for calculating the leading contributions to h ->
gg and h -> gamma gamma in models where the Higgs weakly mixes with a nearly
supersymmetric extra sector. Such mixing terms can play an important role in
raising the Higgs mass relative to the value expected in the MSSM. Our method
applies even when the extra sector is strongly coupled, and moreover does not
require a microscopic Lagrangian description. Using constraints from holomorphy
we fix the leading parametric form of the contributions to these Higgs
processes, including the Higgs mixing angle dependence, up to an overall
coefficient. Moreover, when the Higgs is the sole source of mass for a
superconformal sector, we show that even this coefficient is often calculable.
For appropriate mixing angles, the contribution of the extra states to h -> gg
and h -> gamma gamma can vanish. We also discuss how current experimental
limits already lead to non-trivial constraints on such models. Finally, we
provide examples of extra sectors which satisfy the requirements necessary to
use the holomorphic approximation.Comment: v4: 34 pages, 2 figures, typo corrected and clarification adde
Composite Higgs Search at the LHC
The Higgs boson production cross-sections and decay rates depend, within the
Standard Model (SM), on a single unknown parameter, the Higgs mass. In
composite Higgs models where the Higgs boson emerges as a pseudo-Goldstone
boson from a strongly-interacting sector, additional parameters control the
Higgs properties which then deviate from the SM ones. These deviations modify
the LEP and Tevatron exclusion bounds and significantly affect the searches for
the Higgs boson at the LHC. In some cases, all the Higgs couplings are reduced,
which results in deterioration of the Higgs searches but the deviations of the
Higgs couplings can also allow for an enhancement of the gluon-fusion
production channel, leading to higher statistical significances. The search in
the H to gamma gamma channel can also be substantially improved due to an
enhancement of the branching fraction for the decay of the Higgs boson into a
pair of photons.Comment: 32 pages, 16 figure
Higgs After the Discovery: A Status Report
Recently, the ATLAS and CMS collaborations have announced the discovery of a
125 GeV particle, commensurable with the Higgs boson. We analyze the 2011 and
2012 LHC and Tevatron Higgs data in the context of simplified new physics
models, paying close attention to models which can enhance the diphoton rate
and allow for a natural weak-scale theory. Combining the available LHC and
Tevatron data in the ZZ* 4-lepton, WW* 2-lepton, diphoton, and b-bbar channels,
we derive constraints on the effective low-energy theory of the Higgs boson. We
map several simplified scenarios to the effective theory, capturing numerous
new physics models such as supersymmetry, composite Higgs, dilaton. We further
study models with extended Higgs sectors which can naturally enhance the
diphoton rate. We find that the current Higgs data are consistent with the
Standard Model Higgs boson and, consequently, the parameter space in all models
which go beyond the Standard Model is highly constrained.Comment: 37 pages; v2: ATLAS dijet-tag diphoton channel added, dilaton and
doublet-singlet bugs corrected, references added; v3: ATLAS WW channel
included, comments and references adde
Neuronal circuitry for pain processing in the dorsal horn
Neurons in the spinal dorsal horn process sensory information, which is then transmitted to several brain regions, including those responsible for pain perception. The dorsal horn provides numerous potential targets for the development of novel analgesics and is thought to undergo changes that contribute to the exaggerated pain felt after nerve injury and inflammation. Despite its obvious importance, we still know little about the neuronal circuits that process sensory information, mainly because of the heterogeneity of the various neuronal components that make up these circuits. Recent studies have begun to shed light on the neuronal organization and circuitry of this complex region
Systematic design for trait introgression projects
We demonstrate an innovative approach for designing Trait Introgression (TI) projects based on optimization principles from Operations Research. If the designs of TI projects are based on clear and measurable objectives, they can be translated into mathematical models with decision variables and constraints that can be translated into Pareto optimality plots associated with any arbitrary selection strategy. The Pareto plots can be used to make rational decisions concerning the trade-offs between maximizing the probability of success while minimizing costs and time. The systematic rigor associated with a cost, time and probability of success (CTP) framework is well suited to designing TI projects that require dynamic decision making. The CTP framework also revealed that previously identified ‘best’ strategies can be improved to be at least twice as effective without increasing time or expenses
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