Tunable photonic Bloch oscillations in electrically modulated photonic crystals

We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump AC or DC electric field, terahertz PBOs can appear and cover a terahertz band in electromagnetic spectrum

Experimental determination of the effective strong coupling constant

We present a first attempt to experimentally extract an effective strong coupling constant that we define to be a low Q2 extension of a previous definition by S. Brodsky et al. following an initial work of G. Grunberg. Using Jefferson Lab data and sum rules, we establish its Q2-behavior over the complete Q2-range. The result is compared to effective coupling constants inferred from different processes and to calculations based on Schwinger-Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constants and the calculations is not established it is interesting to note that their behaviors are similar.Comment: Published in Physics Letters B 650 4 24

Final state interactions and the transverse structure of the pion using non-perturbative eikonal methods

In the factorized picture of semi-inclusive hadronic processes the naive time reversal-odd parton distributions exist by virtue of the gauge link which renders it color gauge invariant. The link characterizes the dynamical effect of initial/final-state interactions of the active parton due soft gluon exchanges with the target remnant. Though these interactions are non-perturbative, studies of final-state interaction have been approximated by perturbative one-gluon approximation in Abelian models. We include higher-order contributions by applying non-perturbative eikonal methods incorporating color degrees of freedom in a calculation of the Boer-Mulders function of the pion. Using this framework we explore under what conditions the Boer Mulders function can be described in terms of factorization of final state interactions and a spatial distribution in impact parameter space.Comment: To appear in Phys.Lett.B, 9 pages, 5 figures, added refs. and discussio

Adiabatic sound velocity and compressibility of a trapped d-dimensional ideal anyon gas

The adiabatic sound velocity and compressibility for harmonically trapped ideal anyons in arbitrary dimensions are calculated within Haldane fractional exclusion statistics. The corresponding low-temperature and high-temperature behaviors are studied in detail. To compare with the experimental result of unitary fermions, the sound velocity for anyons in the cigar-shaped trap is derived. The sound velocity for anyons in the disk-shaped trap is also calculated. With the parameter g=0.287, the sound velocity of unitary fermions in the cigar-shaped trap modeled by anyons is in good agreement with the experimental result, while that of unitary fermions in the disk-shaped trap is v_{0}/v_{F}=0.406 with Fermi velocity v_{F}.Comment: 16 pages, 6 figure, elsarticle.cls, minor changes with typos correcte

Disruption of cytoskeletal integrity impairs Gi-mediated signaling due to displacement of Gi proteins

β1 integrins play a crucial role as cytoskeletal anchorage proteins. In this study, the coupling of the cytoskeleton and intracellular signaling pathways was investigated in β1 integrin deficient (−/−) embryonic stem cells. Muscarinic inhibition of the L-type Ca2+ current (ICa) and activation of the acetylcholine-activated K+ current (IK,ACh) was found to be absent in β1 integrin−/− cardiomyocytes. Conversely, β adrenoceptor-mediated modulation of ICa was unaffected by the absence of β1 integrins. This defect in muscarinic signaling was due to defective G protein coupling. This was supported by deconvolution microscopy, which demonstrated that Gi exhibited an atypical subcellular distribution in the β1 integrin−/− cardiomyocytes. A critical role of the cytoskeleton was further demonstrated using cytochalasin D, which displaced Gi and impaired muscarinic signaling. We conclude that cytoskeletal integrity is required for correct localization and function of Gi-associated signaling microdomains

Quantum Simulation of Tunneling in Small Systems

A number of quantum algorithms have been performed on small quantum computers; these include Shor's prime factorization algorithm, error correction, Grover's search algorithm and a number of analog and digital quantum simulations. Because of the number of gates and qubits necessary, however, digital quantum particle simulations remain untested. A contributing factor to the system size required is the number of ancillary qubits needed to implement matrix exponentials of the potential operator. Here, we show that a set of tunneling problems may be investigated with no ancillary qubits and a cost of one single-qubit operator per time step for the potential evolution. We show that physically interesting simulations of tunneling using 2 qubits (i.e. on 4 lattice point grids) may be performed with 40 single and two-qubit gates. Approximately 70 to 140 gates are needed to see interesting tunneling dynamics in three-qubit (8 lattice point) simulations.Comment: 4 pages, 2 figure

Strong Decays of Light Vector Mesons

The vector meson strong decays rho-->pi pi, phi-->KK, and K^star-->pi K are studied within a covariant approach based on the ladder-rainbow truncation of the QCD Dyson--Schwinger equation for the quark propagator and the Bethe--Salpeter equation for the mesons. The model preserves the one-loop behavior of QCD in the ultraviolet, has two infrared parameters, and implements quark confinement and dynamical chiral symmetry breaking. The 3-point decay amplitudes are described in impulse approximation. The Bethe--Salpeter study motivates a method for estimating the masses for heavier mesons within this model without continuing the propagators into the complex plane. We test the accuracy via the rho, phi and K^{star} masses and then produce estimates of the model results for the a_1 and b_1 masses as well as the mass of the proposed exotic vector pi_1(1400).Comment: Submitted for publication; 10x2-column pages, REVTEX 4, 3 .eps files making 3fig

Structure–activity relationship study of bone morphogenetic protein (BMP) signaling inhibitors

A structure–activity relationship study of dorsomorphin, a previously identified inhibitor of SMAD 1/5/8 phosphorylation by bone morphogenetic protein (BMP) type 1 receptors ALK2, 3, and 6, revealed that increased inhibitory activity could be accomplished by replacing the pendent 4-pyridine ring with 4-quinoline. The activity contributions of various nitrogen atoms in the core pyrazolo[1,5-a]pyrimidine ring were also examined by preparing and evaluating pyrrolo[1,2-a]pyrimidine and pyrazolo[1,5-a]pyridine derivatives. In addition, increased mouse liver microsome stability was achieved by replacing the ether substituent on the pendent phenyl ring with piperazine. Finally, an optimized compound 13 (LDN-193189 or DM-3189) demonstrated moderate pharmacokinetic characteristics (e.g., plasma t1/2 = 1.6 h) following intraperitoneal administration in mice. These studies provide useful molecular probes for examining the in vivo pharmacology of BMP signaling inhibition

Bethe-Salpeter equation and a nonperturbative quark-gluon vertex

A Ward-Takahashi identity preserving Bethe-Salpeter kernel can always be calculated explicitly from a dressed-quark-gluon vertex whose diagrammatic content is enumerable. We illustrate that fact using a vertex obtained via the complete resummation of dressed-gluon ladders. While this vertex is planar, the vertex-consistent kernel is nonplanar and that is true for any dressed vertex. In an exemplifying model the rainbow-ladder truncation of the gap and Bethe-Salpeter equations yields many results; e.g., pi- and rho-meson masses, that are changed little by including higher-order corrections. Repulsion generated by nonplanar diagrams in the vertex-consistent Bethe-Salpeter kernel for quark-quark scattering is sufficient to guarantee that diquark bound states do not exist.Comment: 16 pages, 12 figures, REVTEX