2,378 research outputs found
The CKM matrix from anti-SU(7) unification of GUT families
We estimate the CKM matrix elements in the recently proposed minimal model,
anti-SU(7) GUT for the family unification,
+\,(singlets). It is shown that the real
angles of the right-handed unitary matrix diagonalizing the mass matrix can be
determined to fit the Particle Data Group data. However, the phase in the
right-handed unitary matrix is not constrained very much. We also includes an
argument about allocating the Jarlskog phase in the CKM matrix.
Phenomenologically, there are three classes of possible parametrizations,
\delq=\alpha,\beta, or of the unitarity triangle. For the choice of
\delq=\alpha, the phase is close to a maximal one.Comment: 11 pages of LaTex file with 2 figure
750 GeV diphoton resonance and electric dipole moments
We examine the implication of the recently observed 750 GeV diphoton excess
for the electric dipole moments of the neutron and electron. If the excess is
due to a spin zero resonance which couples to photons and gluons through the
loops of massive vector-like fermions, the resulting neutron electric dipole
moment can be comparable to the present experimental bound if the CP-violating
angle {\alpha} in the underlying new physics is of O(10^{-1}). An electron EDM
comparable to the present bound can be achieved through a mixing between the
750 GeV resonance and the Standard Model Higgs boson, if the mixing angle
itself for an approximately pseudoscalar resonance, or the mixing angle times
the CP-violating angle {\alpha} for an approximately scalar resonance, is of
O(10^{-3}). For the case that the 750 GeV resonance corresponds to a composite
pseudo-Nambu-Goldstone boson formed by a QCD-like hypercolor dynamics confining
at \Lambda_HC, the resulting neutron EDM can be estimated with \alpha ~ (750
GeV / \Lambda_HC)^2\theta_HC, where \theta_HC is the hypercolor vacuum angle.Comment: 21 pages, 5 figure
An Interval-Censored Proportional Hazards Model
We fit a Cox proportional hazards (PH) model to interval-censored survival data by first subdividing each individual\u27s failure interval into non-overlapping sub-intervals. Using the set of all interval endpoints in the data set, those that fall into the individual\u27s interval are then used as the cut points for the sub-intervals. Each sub-interval has an accompanying weight calculated from a parametric Weibull model based on the current parameter estimates. A weighted PH model is then fit with multiple lines of observations corresponding to the sub-intervals for each individual, where the lower end of each sub-interval is used as the observed failure time with the accompanying weights incorporated. Right-censored observations are handled in the usual manner. We iterate between estimating the baseline Weibull distribution and fitting the weighted PH model until the regression parameters of interest converge. The regression parameter estimates are fixed as an offset when we update the estimates of the Weibull distribution and recalculate the weights. Our approach is similar to Satten et al.\u27s (1998) method for interval-censored survival analysis that used imputed failure times generated from a parametric model in a PH model. Simulation results demonstrate apparently unbiased parameter estimation for the correctly specified Weibull model and little to no bias for a mis-specified log-logistic model. Breast cosmetic deterioration data and ICU hyperlactemia data are analyzed
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Cellular energy stress induces AMPK-mediated regulation of YAP and the Hippo pathway.
YAP (Yes-associated protein) is a transcription co-activator in the Hippo tumour suppressor pathway and controls cell growth, tissue homeostasis and organ size. YAP is inhibited by the kinase Lats, which phosphorylates YAP to induce its cytoplasmic localization and proteasomal degradation. YAP induces gene expression by binding to the TEAD family transcription factors. Dysregulation of the Hippo-YAP pathway is frequently observed in human cancers. Here we show that cellular energy stress induces YAP phosphorylation, in part due to AMPK-dependent Lats activation, thereby inhibiting YAP activity. Moreover, AMPK directly phosphorylates YAP Ser 94, a residue essential for the interaction with TEAD, thus disrupting the YAP-TEAD interaction. AMPK-induced YAP inhibition can suppress oncogenic transformation of Lats-null cells with high YAP activity. Our study establishes a molecular mechanism and functional significance of AMPK in linking cellular energy status to the Hippo-YAP pathway
Switchable π-electronic network of bis(α-oligothienyl)-substituted hexaphyrins between helical versus rectangular circuit
The switching phenomena of conformation with π-electronic network through deprotonation-protonation processes were investigated by employing a series of 5, 20-bis(α-oligothienyl) substituted hexaphyrins(1.1.1.1.1.1). They showed significant changes in the absorption and emission spectra with deprotonation, and returned to the initial state with protonation. Through NMR measurements and single crystal X-ray diffraction analysis, we found that the 5, 20-bis(α-oligothienyl) substituted hexaphyrins, which possess acyclic, helical electronic networks involving oligothienyl chains in dumbbell conformations (type-I) in a neutral form, underwent effective deprotonation upon treatment with tetrabutylammonium fluoride (TBAF) to generate the corresponding dianions, which display cyclic electronic networks with enhanced aromaticity in rectangular conformations (type-II). Our quantum calculation results provide an unambiguous description for the switchable conformation and π-conjugation, which revealed that a deprotonation-induced enhanced aromatic conjugation pathway is involved in the switchable π-electronic network
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Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet Fe3GeTe2 through Hole Doping.
Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3-xGeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin-orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping
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