234 research outputs found
Effective hadron masses and couplings in nuclear matter and incompressibility
The role of effective hadron masses and effective couplings in nuclear matter
is studied using a generalized effective Lagrangian for sigma-omega model. A
simple relation among the effective masses, the effective couplings and the
incompressibility K is derived. Using the relation, it is found that the
effective repulsive and the effective attractive forces are almost canceled to
each other at the normal density. Inversely, if this cancellation is almost
complete, K should be 250-350MeV.Comment: 13 pages of text, 16 figure
Equation of state in the PNJL model with the entanglement interaction
The equation of state and the phase diagram in two-flavor QCD are
investigated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model
with an entanglement vertex between the chiral condensate and the
Polyakov-loop. The entanglement-PNJL (EPNJL) model reproduces LQCD data at zero
and finite chemical potential better than the PNJL model. Hadronic degrees of
freedom are taken into account by the free-hadron-gas (FHG) model with the
volume-exclusion effect due to the hadron generation. The EPNJL+FHG model
improves agreement of the EPNJL model with LQCD data particularly at small
temperature. The quarkyonic phase survives, even if the correlation between the
chiral condensate and the Polyakov loop is strong and hadron degrees of freedom
are taken into account. However, the location of the quarkyonic phase is
sensitive to the strength of the volume exclusion.Comment: 9 pages, 7 figure
Quark condensate in nuclear matter based on Nuclear Schwinger-Dyson formalism
The effects of higher order corrections of ring diagrams for the quark
condensate are studied by using the bare vertex Nuclear Schwinger Dyson
formalism based on - model. At the high density the quark
condensate is reduced by the higher order contribution of ring diagrams more
than the mean field theory or the Hartree-Fock
Ahnak1 modulates L-type Ca(2+) channel inactivation of rodent cardiomyocytes
Ahnak1, a giant 700 kDa protein, has been implicated in Ca(2+) signalling in various cells. Previous work suggested that the interaction between ahnak1 and Cavbeta(2) subunit plays a role in L-type Ca(2+) current (I (CaL)) regulation. Here, we performed structure-function studies with the most C-terminal domain of ahnak1 (188 amino acids) containing a PxxP consensus motif (designated as 188-PSTP) using ventricular cardiomyocytes isolated from rats, wild-type (WT) mice and ahnak1-deficient mice. In vitro binding studies revealed that 188-PSTP conferred high-affinity binding to Cavbeta(2) (K (d) approximately 60 nM). Replacement of proline residues by alanines (188-ASTA) decreased Cavbeta(2) affinity about 20-fold. Both 188-PSTP and 188-ASTA were functional in ahnak1-expressing rat and mouse cardiomyocytes during whole-cell patch clamp. Upon intracellular application, they increased the net Ca(2+) influx by enhancing I (CaL) density and/or increasing I (CaL) inactivation time course without altering voltage dependency. Specifically, 188-ASTA, which failed to affect I (CaL) density, markedly slowed I (CaL) inactivation resulting in a 50-70% increase in transported Ca(2+) during a 0 mV depolarising pulse. Both ahnak1 fragments also slowed current inactivation with Ba(2+) as charge carrier. By contrast, neither 188-PSTP nor 188-ASTA affected any I (CaL) characteristics in ahnak1-deficient mouse cardiomyocytes. Our results indicate that the presence of endogenous ahnak1 is required for tuning the voltage-dependent component of I (CaL) inactivation by ahnak1 fragments. We suggest that ahnak1 modulates the accessibility of molecular determinants in Cavbeta(2) and/or scaffolds selectively different beta-subunit isoforms in the heart
Optical properties and resonant cavity modes in axial InGaN/GaN nanotube microcavities
Microcavities based on group-III nitride material offer a notable platform for the investigation of light-matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Disk or tube geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we present the fabrication of homogenous and dense arrays of axial InGaN/GaN nanotubes via a combination of displacement Talbot lithography (DTL) for patterning and inductively coupled plasma top-down dry-etching. Optical characterization highlights the homogeneous emission from nanotube structures. Power-dependent continuous excitation reveals a non-uniform light distribution within a single nanotube, with vertical confinement between the bottom and top facets, and radial confinement within the active region. Finite-difference time-domain simulations, taking into account the particular shape of the outer diameter, indicate that the cavity mode of a single nanotube has a mixed WGM-vertical Fabry-Perot mode (FPM) nature. Additional simulations demonstrate that the improvement of the shape symmetry and dimensions primarily influence the Q-factor of the WGMs whereas the position of the active region impacts the coupling efficiency with one or a family of vertical FPMs. These results show that regular arrays of axial InGaN/GaN nanotubes can be achieved via a low-cost, fast and large-scale process based on DTL and top-down etching. These techniques open a new perspective for cost effective fabrication of nano-LED and nano-laser structures along with bio-chemical sensing applications
Second Order Dissipative Fluid Dynamics for Ultra-Relativistic Nuclear Collisions
The M\"uller-Israel-Stewart second order theory of relativistic imperfect
fluids based on Grad's moment method is used to study the expansion of hot
matter produced in ultra-relativistic heavy ion collisions. The temperature
evolution is investigated in the framework of the Bjorken boost-invariant
scaling limit. The results of these second-order theories are compared to those
of first-order theories due to Eckart and to Landau and Lifshitz and those of
zeroth order (perfect fluid) due to Euler.Comment: 5 pages, 4 figures, size of y-axis tick marks for Figs. 3 and 4 fixe
Spontaneous parity and charge-conjugation violations at real isospin and imaginary baryon chemical potentials
The phase structure of two-flavor QCD is investigated at real isospin and
imaginary quark chemical potentials by using the Polyakov-loop extended
Nambu--Jona-Lasinio model. In the region, parity symmetry is spontaneously
broken by the pion superfluidity phase transition, whereas charge-conjugation
symmetry is spontaneously violated by the Roberge-Weiss transition. The chiral
(deconfinement) crossover at zero isospin and quark chemical potentials is a
remnant of the parity (charge-conjugation) violation. The interplay between the
parity and charge-conjugation violations are analyzed, and it is investigated
how the interplay is related to the correlation between the chiral and
deconfinement crossovers at zero isospin and quark chemical potentials.Comment: 12 pages, 18 figures. Typos were revised. Symbols /P and /C were
added in Figures 8a and 8b. Colors of the figures were changed. Some
sentences were added and revise
Crystal structure of APOBEC3A bound to single-stranded DNA reveals structural basis for cytidine deamination and specificity
Nucleic acid editing enzymes are essential components of the immune system that lethally mutate viral pathogens and somatically mutate immunoglobulins, and contribute to the diversification and lethality of cancers. Among these enzymes are the seven human APOBEC3 deoxycytidine deaminases, each with unique target sequence specificity and subcellular localization. While the enzymology and biological consequences have been extensively studied, the mechanism by which APOBEC3s recognize and edit DNA remains elusive. Here we present the crystal structure of a complex of a cytidine deaminase with ssDNA bound in the active site at 2.2 A. This structure not only visualizes the active site poised for catalysis of APOBEC3A, but pinpoints the residues that confer specificity towards CC/TC motifs. The APOBEC3A-ssDNA complex defines the 5\u27-3\u27 directionality and subtle conformational changes that clench the ssDNA within the binding groove, revealing the architecture and mechanism of ssDNA recognition that is likely conserved among all polynucleotide deaminases, thereby opening the door for the design of mechanistic-based therapeutics
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