1,249 research outputs found
Enhanced signal at the LHC with decay and -violating top-Higgs coupling
We study the observability of non-standard top Yukawa couplings in the
channel at 14 TeV high-luminosity LHC (HL-LHC). The small diphoton branching
ratio is enhanced when the -violating phase, , of the
top-Higgs interaction is non-zero. When the modulus of the top-Higgs
interaction assumes the SM value, , we find that the signal
significance reaches when . Furthermore, the different couplings modify the polarisation of the top
quark, and can subsequently be distinguished via asymmetries in spin
correlations with the final state leptons. The diphoton decay mode is found to
be significantly more promising than the previously considered channel.Comment: 14 pages, 3 figures and 2 tables; minor corrections to match
published versio
Gravitational waves from a supercooled electroweak phase transition and their detection with pulsar timing arrays
We investigate the properties of a stochastic gravitational wave background
produced by a first-order electroweak phase transition in the regime of extreme
supercooling. We study a scenario whereby the percolation temperature that
signifies the completion of the transition, , can be as low as a few MeV
(nucleosynthesis temperature), while most of the true vacuum bubbles are formed
much earlier at the nucleation temperature, GeV. This implies that
the gravitational wave spectrum is mainly produced by the collisions of large
bubbles and characterised by a large amplitude and a peak frequency as low as
Hz. We show that such a scenario can occur in (but not
limited to) a model based on a non-linear realisation of the electroweak gauge
group, such that the Higgs vacuum configuration is altered by a cubic coupling.
In order to carefully quantify the evolution of the phase transition of this
model over such a wide temperature range, we go beyond the usual fast
transition approximation, taking into account the expansion of the Universe as
well as the behaviour of the nucleation probability at low temperatures. Our
computation shows that there exists a range of parameters for which the
gravitational wave spectrum lies at the edge between the exclusion limits of
current pulsar timing array experiments and the detection band of the future
Square Kilometre Array observatory.Comment: 20 pages, 3 figures. V2: references added and corrections to match
published versio
Central-edge asymmetry as a probe of Higgs-top coupling in production at LHC
The Higgs-top coupling plays a central role in the hierarchy problem and the
vacuum stability of the Standard Model (SM). We propose a central-edge
asymmetry () to probe the CP violating Higgs-top coupling in dileptonic
channel of production at the LHC. We demonstrate that
the CP-violating Higgs-top coupling can affect the central-edge asymmetry
through distorting distribution because of the
contribution of new top charge asymmetric term. Since
distribution is frame-independent and has a good discrimination even in boosted
regime, we use the jet substructure technique to enhance the observability of
the dileptonic channel of production. We find that (1) the
significance of dileptonic channel of production can reach
for CP phase when the luminosity fb at 14 TeV LHC. (2) the central-edge asymmetry
show a good discrimination power of CP phase of
interaction, which are -40.26\%, -26.60\%, -9.47\% for , , respectively and are hardly affected by the event selections. Besides,
by performing the binned- analysis of
distribution, we find that the scalar and pseudo-scalar interactions can be
distinguished at 95\% C.L. level at 14 TeV HL-LHC.Comment: minor changes, version accepted by PL
Subacute Sclerosing Panencephalitis of the Brainstem as a Clinical Entity.
Subacute sclerosing panencephalitis (SSPE) is a rare progressive neurological disorder of early adolescence caused by persistent infection of the measles virus, which remains prevalent worldwide despite an effective vaccine. SSPE is a devastating disease with a characteristic clinical course in subcortical white matter; however, atypical presentations of brainstem involvement may be seen in rare cases. This review summarizes reports to date on brainstem involvement in SSPE, including the clinical course of disease, neuroimaging presentations, and guidelines for treatment. A comprehensive literature search was performed for English-language publications with keywords "subacute sclerosing panencephalitis" and "brainstem" using the National Library of Medicine PubMed database (March 1981-September 2017). Eleven articles focusing on SSPE of the brainstem were included. Predominant brainstem involvement remains uncharacteristic of SSPE, which may lead to misdiagnosis and poor outcome. A number of case reports have demonstrated brainstem involvement associated with other intracranial lesions commonly presenting in later SSPE stages (III and IV). However, brainstem lesions can appear in all stages, independent of higher cortical structures. The varied clinical presentations complicate diagnosis from a neuroimaging perspective. SSPE of the brainstem is a rare but important clinical entity. It may present like canonical SSPE or with unique clinical features such as absence seizures and pronounced ataxia. While SSPE generally progresses to the brainstem, it can also begin with a primary focus of infection in the brainstem. Awareness of varied SSPE presentations can aid in early diagnosis as well as guide management and treatment
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Genome-wide Integrative Analysis of Zika-Virus-Infected Neuronal Stem Cells Reveals Roles for MicroRNAs in Cell Cycle and Stemness.
Zika virus (ZIKV) infection is implicated in severe fetal developmental disorders, including microcephaly. MicroRNAs (miRNAs) post-transcriptionally regulate numerous processes associated with viral infection and neurodegeneration, but their contribution to ZIKV pathogenesis is unclear. We analyzed the mRNA and miRNA transcriptomes of human neuronal stem cells (hNSCs) during infection with ZIKV MR766 and Paraiba strains. Integration of the miRNA and mRNA expression data into regulatory interaction networks showed that ZIKV infection resulted in miRNA-mediated repression of genes regulating the cell cycle, stem cell maintenance, and neurogenesis. Bioinformatics analysis of Argonaute-bound RNAs in ZIKV-infected hNSCs identified a number of miRNAs with predicted involvement in microcephaly, including miR-124-3p, which dysregulates NSC maintenance through repression of the transferrin receptor (TFRC). Consistent with this, ZIKV infection upregulated miR-124-3p and downregulated TFRC mRNA in ZIKV-infected hNSCs and mouse brain tissue. These data provide insights into the roles of miRNAs in ZIKV pathogenesis, particularly the microcephaly phenotype
Zika virus infection reprograms global transcription of host cells to allow sustained infection.
Zika virus (ZIKV) is an emerging virus causally linked to neurological disorders, including congenital microcephaly and Guillain-Barré syndrome. There are currently no targeted therapies for ZIKV infection. To identify novel antiviral targets and to elucidate the mechanisms by which ZIKV exploits the host cell machinery to support sustained replication, we analyzed the transcriptomic landscape of human microglia, fibroblast, embryonic kidney and monocyte-derived macrophage cell lines before and after ZIKV infection. The four cell types differed in their susceptibility to ZIKV infection, consistent with differences in their expression of viral response genes before infection. Clustering and network analyses of genes differentially expressed after ZIKV infection revealed changes related to the adaptive immune system, angiogenesis and host metabolic processes that are conducive to sustained viral production. Genes related to the adaptive immune response were downregulated in microglia cells, suggesting that ZIKV effectively evades the immune response after reaching the central nervous system. Like other viruses, ZIKV diverts host cell resources and reprograms the metabolic machinery to support RNA metabolism, ATP production and glycolysis. Consistent with these transcriptomic analyses, nucleoside metabolic inhibitors abrogated ZIKV replication in microglia cells
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