1,450 research outputs found

    Anomalous gtt couplings in the Littlest Higgs Model with T-parity

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    In this work we calculate the leading electroweak (EW) corrections to the anomalous gttˉgt\bar{t} coupling in the Littlest Higgs model with T-parity (LHT), by applying the Goldstone boson equivalence theorem. In the LHT model, such electroweak corrections arise from the loop diagrams of heavy fermions and the ``would-be'' Goldstone bosons. We further examine the EW corrections in the top quark pair production via the quark annihilation process at the LHC. The negative EW corrections in the Standard Model are partially canceled by the positive EW corrections from the loops of the new heavy particles, and the latter dominates in the large invariant mass of the top quark pair.Comment: version appeared in PR

    GeV antiproton/gamma-ray excesses and the WW-boson mass anomaly: three faces of ∼60βˆ’70\sim 60-70 GeV dark matter particle?

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    For the newly discovered WW-boson mass anomaly, one of the simplest dark matter (DM) models that can account for the anomaly without violating other astrophysical/experimental constraints is the inert two Higgs doublet model, in which the DM mass (mSm_{S}) is found to be within ∼54βˆ’74\sim 54-74 GeV. In this model, the annihilation of DM via SSβ†’bbΛ‰SS\to b\bar{b} and SSβ†’WWβˆ—SS\to WW^{*} would produce antiprotons and gamma rays, and may account for the excesses identified previously in both particles. Motivated by this, we re-analyze the AMS-02 antiproton and Fermi-LAT Galactic center gamma-ray data. For the antiproton analysis, the novel treatment is the inclusion of the charge-sign-dependent three-dimensional solar modulation model as constrained by the time-dependent proton data. We find that the excess of antiprotons is more distinct than previous results based on the force-field solar modulation model. The interpretation of this excess as the annihilation of SSβ†’WWβˆ—SS\to WW^{*} (SSβ†’bbΛ‰SS\to b\bar{b}) requires a DM mass of ∼40βˆ’80\sim 40-80 (40βˆ’6040-60) GeV and a velocity-averaged cross section of O(10βˆ’26)Β cm3Β sβˆ’1O(10^{-26})~{\rm cm^3~s^{-1}}. As for the Ξ³\gamma-ray data analysis, rather than adopting the widely-used spatial template fitting, we employ an orthogonal approach with a data-driven spectral template analysis. The fitting to the GeV Ξ³\gamma-ray excess yields DM model parameters overlapped with those to fit the antiproton excess via the WWβˆ—WW^{*} channel. The consistency of the DM particle properties required to account for the WW-boson mass anomaly, the GeV antiproton excess, and the GeV Ξ³\gamma-ray excess suggest a common origin of them.Comment: 8 page

    Retigeric Acid B Exhibits Antitumor Activity through Suppression of Nuclear Factor-ΞΊB Signaling in Prostate Cancer Cells in Vitro and in Vivo

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    Previously, we reported that retigeric acid B (RB), a natural pentacyclic triterpenic acid isolated from lichen, inhibited cell growth and induced apoptosis in androgen-independent prostate cancer (PCa) cells. However, the mechanism of action of RB remains unclear. In this study, we found that using PC3 and DU145 cells as models, RB inhibited phosphorylation levels of IΞΊBΞ± and p65 subunit of NF-ΞΊB in a time- and dosage-dependent manner. Detailed study revealed that RB blocked the nuclear translocation of p65 and its DNA binding activity, which correlated with suppression of NF-ΞΊB-regulated proteins including Bcl-2, Bcl-xL, cyclin D1 and survivin. NF-ΞΊB reporter assay suggested that RB was able to inhibit both constitutive activated-NF-ΞΊB and LPS (lipopolysaccharide)-induced activation of NF-ΞΊB. Overexpression of RelA/p65 rescued RB-induced cell death, while knockdown of RelA/p65 significantly promoted RB-mediated inhibitory effect on cell proliferation, suggesting the crucial involvement of NF-ΞΊB pathway in this event. We further analyzed antitumor activity of RB in in vivo study. In C57BL/6 mice carrying RM-1 homografts, RB inhibited tumor growth and triggered apoptosis mainly through suppressing NF-ΞΊB activity in tumor tissues. Additionally, DNA microarray data revealed global changes in the gene expression associated with cell proliferation, apoptosis, invasion and metastasis in response to RB treatment. Therefore, our findings suggested that RB exerted its anti-tumor effect by targeting the NF-ΞΊB pathway in PCa cells, and this could be a general mechanism for the anti-tumor effect of RB in other types of cancers as well

    Fabrication of Densely Packed AlN Nanowires by a Chemical Conversion of Al2O3Nanowires Based on Porous Anodic Alumina Film

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    Porous alumina film on aluminum with gel-like pore wall was prepared by a two-step anodization of aluminum, and the corresponding gel-like porous film was etched in diluted NaOH solution to produce alumina nanowires in the form of densely packed alignment. The resultant alumina nanowires were reacted with NH3and evaporated aluminum at an elevated temperature to be converted into densely packed aluminum nitride (AlN) nanowires. The AlN nanowires have a diameter of 15–20 nm larger than that of the alumina nanowires due to the supplement of the additional evaporated aluminum. The results suggest that it might be possible to prepare other aluminum compound nanowires through similar process

    Constraints on Large Extra Dimensions with Bulk Neutrinos

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    We consider right-handed neutrinos propagating in Ξ΄\delta (large) extra dimensions, whose only coupling to Standard Model fields is the Yukawa coupling to the left-handed neutrino and the Higgs boson. These theories are attractive as they can explain the smallness of the neutrino mass, as has already been shown. We show that if Ξ΄\delta is bigger than two, there are strong constraints on the radius of the extra dimensions, resulting from the experimental limit on the probability of an active state to mix into the large number of sterile Kaluza-Klein states of the bulk neutrino. We also calculate the bounds on the radius resulting from requiring that perturbative unitarity be valid in the theory, in an imagined Higgs-Higgs scattering channel.Comment: 24 pages, 4 figures, revtex4. v2: Minor typos corrected, references adde

    The Hidden Nematic Fluctuations in the Triclinic (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 Superconductor Revealed by Ultrafast Optical Spectroscopy

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    We reported the quasiparticle relaxation dynamics of an optimally doped triclinic iron-based superconductor (Ca0.85_{0.85}La0.15_{0.15})10_{10}(Pt3_3As8_8)(Fe2_2As2_2)5_5 with bulk TcT_c = 30 K using polarized ultrafast optical pump-probe spectroscopy. Our results reveal anisotropic transient reflectivity induced by nematic fluctuations develops below TnemT_{nem} β‰ˆ\approx 120 K and persists in the superconducting states. Measurements under high pump fluence reveal three distinct, coherent phonon modes at frequencies of 1.6, 3.5, and 4.7 THz, corresponding to A1g(1)A_{1g}(1), EgE_g, and A1g(2)A_{1g}(2) modes, respectively. The high-frequency A1g(2)A_{1g}(2) mode corresponds to the cc-axis polarized vibrations of FeAs planes with a nominal electron-phonon coupling constant Ξ»A1g(2)\lambda _{A_{1g}(2)} β‰ˆ\approx 0.139 Β±\pm 0.02. Our findings suggest that the superconductivity and nematic state are compatible but competitive at low temperatures, and the A1gA_{1g} phonons play an important role in the formation of Cooper pairs in (Ca0.85_{0.85}La0.15_{0.15})10_{10}(Pt3_3As8_8)(Fe2_2As2_2)5_5.Comment: 6 pages, 3 figures and Supplemental Material

    Shugoshin1 May Play Important Roles in Separation of Homologous Chromosomes and Sister Chromatids during Mouse Oocyte Meiosis

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    Background: Homologous chromosomes separate in meiosis I and sister chromatids separate in meiosis II, generating haploid gametes. To address the question why sister chromatids do not separate in meiosis I, we explored the roles of Shogoshin1 (Sgo1) in chromosome separation during oocyte meiosis. Methodology/Principal Findings: Sgo1 function was evaluated by exogenous overexpression to enhance its roles and RNAi to suppress its roles during two meioses of mouse oocytes. Immunocytochemistry and chromosome spread were used to evaluate phenotypes. The exogenous Sgo1 overexpression kept homologous chromosomes and sister chromatids not to separate in meiosis I and meiosis II, respectively, while the Sgo1 RNAi promoted premature separation of sister chromatids. Conclusions: Our results reveal that prevention of premature separation of sister chromatids in meiosis I requires th

    Phosphor coated NiO-based planar inverted organometallic halide perovskite solar cells with enhanced efficiency and stability

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    This work investigates non-rare-earth phosphor (Sr4Al14O25:Mn4+, 0.5%Mg) with intensively red luminescence as a luminescent down-shifting layer for perovskite solar cells. The power conversion efficiency of the fabricated device with a structure of NiO/CH3NH3PbI3/[6,6]-phenyl C61-butyric acid methyl ester/Au coated with phosphor layer shows a 10% increase as compared with that of the control devices. Importantly, the phosphor layer coating can realize UV-protection as well as waterproof capability, achieving a reduced moisture-degradation of CH3NH3PbI3 perovskite upon applying an UV irradiation. Therefore, perovskite devices using this luminescent coating show a combined enhancement in both UV down-shifting conversion and long term stability. This can be expanded as a promising encapsulation technique in the perovskite solar cell community

    Genome-wide association study identifies novel susceptibility loci for cutaneous squamous cell carcinoma

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    Cutaneous squamous cell carcinoma represents the second most common cutaneous malignancy, affecting 7–11% of Caucasians in the United States. The genetic determinants of susceptibility to cutaneous squamous cell carcinoma remain largely unknown. Here we report the results of a two-stage genome-wide association study of cutaneous squamous cell carcinoma, totalling 7,404 cases and 292,076 controls. Eleven loci reached genome-wide significance (P<5 Γ— 10βˆ’8) including seven previously confirmed pigmentation-related loci: MC1R, ASIP, TYR, SLC45A2, OCA2, IRF4 and BNC2. We identify an additional four susceptibility loci: 11q23.3 CADM1, a metastasis suppressor gene involved in modifying tumour interaction with cell-mediated immunity; 2p22.3; 7p21.1 AHR, the dioxin receptor involved in anti-apoptotic pathways and melanoma progression; and 9q34.3 SEC16A, a putative oncogene with roles in secretion and cellular proliferation. These susceptibility loci provide deeper insight into the pathogenesis of squamous cell carcinoma
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