Top quark decays with flavor violation in the B-LSSM

The decays of top quark $t\rightarrow c\gamma,\;t\rightarrow cg,\;t\rightarrow cZ,\;t\rightarrow ch$ are extremely rare processes in the standard model (SM). The predictions on the corresponding branching ratios in the SM are too small to be detected in the future, hence any measurable signal for the processes at the LHC is a smoking gun for new physics. In the extension of minimal supersymmetric standard model with an additional local $U(1)_{B-L}$ gauge symmetry (B-LSSM), new gauge interaction and new flavor changing interaction affect the theoretical evaluations on corresponding branching ratios of those processes. In this work, we analyze those processes in the B-LSSM, under a minimal flavor violating assumption for the soft breaking terms. Considering the constraints from updated experimental data, the numerical results imply $Br(t\rightarrow c\gamma)\sim5\times10^{-7}$, $Br(t\rightarrow cg)\sim2\times10^{-6}$, $Br(t\rightarrow cZ)\sim4\times10^{-7}$ and $Br(t\rightarrow ch)\sim3\times10^{-9}$ in our chosen parameter space. Simultaneously, new gauge coupling constants $g_{_B},\;g_{_{YB}}$ in the B-LSSM can also affect the numerical results of $Br(t\rightarrow c\gamma,\;cg,\;cZ,\;ch)$.Comment: 20 pages, 4 figures, published in EPJC. arXiv admin note: substantial text overlap with arXiv:1803.0990

The expression of PLK-1 in cervical carcinoma: a possible target for enhancing chemosensitivity

<p>Abstract</p> <p>Background</p> <p>Polo-like kinase-1 (PLK-1) is reported to be upregulated in a variety of human tumors and is implicated in cell proliferation and survival. However, its importance in cervical carcinoma has not yet been fully elucidated.</p> <p>Methods</p> <p>We examined PLK-1 expression in cervical carcinoma tissues using immunohistochemical staining. Furthermore, we blocked PLK-1 expression in HeLa cells using specific siRNA and detected the cell cycle, cell proliferation and chemosensitivity using western blotting, MTT and flow cytometry.</p> <p>Results</p> <p>We provide evidence that expression of PLK-1 exists in human cervical carcinoma tissues and establish an association with tumor size. Furthermore, we show that PLK-1 knockdown by transfection of siRNA induces accumulation of HeLa cells in the G2/M cell cycle phase and enhances cisplatin-induced apoptosis.</p> <p>Conclusion</p> <p>Our results indicate that PLK-1 production in HeLa cells might be critical in determining whether cells survive or undergo apoptosis. Therefore, targeting PLK-1 might be a promising strategy for enhancing sensitivity to chemotherapeutic reagents in cervical carcinoma.</p

An analytic derivation of the empirical correlations of gamma-ray bursts

Empirical correlations between various key parameters have been extensively explored ever since the discovery of gamma-ray bursts (GRBs) and have been widely used as standard candles to probe the Universe. The Amati relation and the Yonetoku relation are two good examples, which have been paid special attention to. The former reflects the connection between the peak photon energy (Ep) and the isotropic $\gamma$-ray energy release (Eiso), while the latter links Ep with the isotropic peak luminosity (Lp), both in the form of a power law function. Most GRBs are found to well follow these correlations, but a theoretical interpretation is still lacking. Meanwhile, there are also some obvious outliers, which may be off-axis GRBs and may follow different correlations as compared with the on-axis ones. Here we present a simple analytical derivation for the Amati relation and the Yonetoku relation in the framework of the standard fireball model, the correctness of which are then confirmed by numerical simulations. The off-axis Amati relation and Yonetoku relation are also derived, which differ from the corresponding on-axis relation markedly. Our results reveal the intrinsic physics lying behind the radiation processes of GRBs, and highlight the importance of viewing angle in the empirical correlations of GRBs.Comment: 20 pages, 7 figures, 2 tables. Submitted to A&

Characterization of a New M13 Metallopeptidase from Deep-Sea Shewanella sp. E525-6 and Mechanistic Insight into Its Catalysis

Bacterial extracellular peptidases are important for bacterial nutrition and organic nitrogen degradation in the ocean. While many peptidases of the M13 family from terrestrial animals and bacteria are studied, there has been no report on M13 peptidases from marine bacteria. Here, we characterized an M13 peptidase, PepS, from the deep-sea sedimentary strain Shewanella sp. E525-6, and investigated its substrate specificity and catalytic mechanism. The gene pepS cloned from strain E525-6 contains 2085 bp and encodes an M13 metallopeptidase. PepS was expressed in Escherichia coli and purified. Among the characterized M13 peptidases, PepS shares the highest sequence identity (47%) with Zmp1 from Mycobacterium tuberculosis, indicating that PepS is a new member of the M13 family. PepS had the highest activity at 30°C and pH 8.0. It retained 15% activity at 0°C. Its half life at 40°C was only 4 min. These properties indicate that PepS is a cold-adapted enzyme. The smallest substrate for PepS is pentapeptide, and it is probably unable to cleave peptides of more than 30 residues. PepS prefers to hydrolyze peptide bonds with P1’ hydrophobic residues. Structural and mutational analyses suggested that His531, His535 and Glu592 coordinate the catalytic zinc ion in PepS, Glu532 acts as a nucleophile, and His654 is probably involved in the transition state stabilization. Asp538 and Asp596 can stablize the orientations of His531 and His535, and Arg660 can stablize the orientation of Asp596. These results help in understanding marine bacterial peptidases and organic nitrogen degradation

3-(2-Bromo­phen­yl)thia­zolo[3,2-a]benzimidazole

The title compound, C15H9BrN2S, was prepared by the reaction of 1-bromo-2-(2,2-dibromo­vin­yl)benzene with 1H-benzo[d]imidazole-2(3H)-thione. The thia­zolo[3,2-a]benz­imidazole fused-ring system is nearly planar, the maximum atomic deviation being 0.049 (4) Å. This mean plane is oriented at a dihedral angle of 71.55 (17)° with respect ot the bromo­phenyl ring. π–π stacking is observed in the crystal structure, the centroid–centroid distance between the thia­zole and imidazole rings of adjacent mol­ecules being 3.582 (2) Å