Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

Shape memory nanocomposites of polyurethane (PU)-clay were fabricated by melt mixing of PU and nano-clay. Based on nano-indentation and microhardness tests, the strength of the nanocomposites increased dramatically as a function of clay content, which is attributed to the enhanced nanoclay–polymer interactions. Thermal mechanical experiments demonstrated good mechanical and shape memory effects of the nanocomposites. Full shape memory recovery was displayed by both the pure PU and PU-clay nanocomposites.

Light meson mass dependence of the positive parity heavy-strange mesons

We calculate the masses of the resonances D_{s0}^*(2317) and D_{s1}(2460) as well as their bottom partners as bound states of a kaon and a D^*- and B^*-meson, respectively, in unitarized chiral perturbation theory at next-to-leading order. After fixing the parameters in the D_{s0}^*(2317) channel, the calculated mass for the D_{s1}(2460) is found in excellent agreement with experiment. The masses for the analogous states with a bottom quark are predicted to be M_{B^*_{s0}}=(5696\pm 40) MeV and M_{B_{s1}}=(5742\pm 40) MeV in reasonable agreement with previous analyses. In particular, we predict M_{B_{s1}}-M_{B_{s0}^*}=46\pm 1 MeV. We also explore the dependence of the states on the pion and kaon masses. We argue that the kaon mass dependence of a kaonic bound state should be almost linear with slope about unity. Such a dependence is specific to the assumed molecular nature of the states. We suggest to extract the kaon mass dependence of these states from lattice QCD calculations.Comment: 10 page

Scintillation and charge extraction from the tracks of energetic electrons in superfluid helium-4

An energetic electron passing through liquid helium causes ionization along its track. The ionized electrons quickly recombine with the resulting positive ions, which leads to the production of prompt scintillation light. By applying appropriate electric fields, some of the ionized electrons can be separated from their parent ions. The fraction of the ionized electrons extracted in a given applied field depends on the separation distance between the electrons and the ions. We report the determination of the mean electron-ion separation distance for charge pairs produced along the tracks of beta particles in superfluid helium at 1.5 K by studying the quenching of the scintillation light under applied electric fields. Knowledge of this mean separation parameter will aid in the design of particle detectors that use superfluid helium as a target material.Comment: 10 pages, 8 figure

Nonleptonic Weak Decays of Bottom Baryons

Cabibbo-allowed two-body hadronic weak decays of bottom baryons are analyzed. Contrary to the charmed baryon sector, many channels of bottom baryon decays proceed only through the external or internal W-emission diagrams. Moreover, W-exchange is likely to be suppressed in the bottom baryon sector. Consequently, the factorization approach suffices to describe most of the Cabibbo-allowed bottom baryon decays. We use the nonrelativistic quark model to evaluate heavy-to-heavy and heavy-to-light baryon form factors at zero recoil. When applied to the heavy quark limit, the quark model results do satisfy all the constraints imposed by heavy quark symmetry. The decay rates and up-down asymmetries for bottom baryons decaying into $(1/2)^++P(V)$ and $(3/2)^++P(V)$ are calculated. It is found that the up-down asymmetry is negative except for $\Omega_b \to (1/2)^++P(V)$ decay and for decay modes with $\psi'$ in the final state. The prediction $B(\Lambda_b \to J/\psi\Lambda)=1.6 \times 10^{-4}$ for $|V_{cb}|=0.038$ is consistent with the recent CDF measurement. We also present estimates for $\Omega_c \to (3/2)^++P(V)$ decays and compare with various model calculations.Comment: 24 pages, to appear in Phys. Rev. Uncertainties with form factor q^2 dependence are discusse

Semileptonic decays of Bs1B_{s1}, Bs2∗B_{s2}^*, Bs0B_{s0} and Bs1′B_{s1}'

Stimulated by recent observations of the excited bottom-strange mesons $B_{s1}$ and $B_{s2}^*$, we calculate the semileptonic decays $B_{s0}, B_{s1}^{\prime}, B_{s1}, B_{s2}^*\to [D_s(1968), D_{s}^*(2112), D_{sJ}(2317), D_{sJ}(2460)]\ell\bar{\nu}$, which is relevant for the exploration of the potential of searching these semileptonic decays in experiment.Comment: 11 pages, 3 figures, 9 tables. More discussion added, some descriptions changed. The version to appear in EPJ

Dispersive Manipulation of Paired Superconducting Qubits

We combine the ideas of qubit encoding and dispersive dynamics to enable robust and easy quantum information processing (QIP) on paired superconducting charge boxes sharing a common bias lead. We establish a decoherence free subspace on these and introduce universal gates by dispersive interaction with a LC resonator and inductive couplings between the encoded qubits. These gates preserve the code space and only require the established local symmetry and the control of the voltage bias.Comment: 5 pages, incl. 1 figur

A New Estimate of North American Mountain Snow Accumulation From Regional Climate Model Simulations

Despite the importance of mountain snowpack to understanding the water and energy cycles in North America's montane regions, no reliable mountain snow climatology exists for the entire continent. We present a new estimate of mountain snow water equivalent (SWE) for North America from regional climate model simulations. Climatological peak SWE in North America mountains is 1,006 km3, 2.94 times larger than previous estimates from reanalyses. By combining this mountain SWE value with the best available global product in nonmountain areas, we estimate peak North America SWE of 1,684 km3, 55% greater than previous estimates. In our simulations, the date of maximum SWE varies widely by mountain range, from early March to mid-April. Though mountains comprise 24% of the continent's land area, we estimate that they contain ~60% of North American SWE. This new estimate is a suitable benchmark for continental- and global-scale water and energy budget studies

Di-Pion Decays of Heavy Quarkonium in the Field Correlator Method

Mechanism of di-pion transitions $nS\to n'S\pi\pi(n=3,2; n'=2,1)$ in bottomonium and charmonium is studied with the use of the chiral string-breaking Lagrangian allowing for the emission of any number of $\pi(K,\eta),$ and not containing fitting parameters. The transition amplitude contains two terms, $M=a-b$, where first term (a) refers to subsequent one-pion emission: $\Upsilon(nS)\to\pi B\bar B^*\to\pi\Upsilon(n'S)\pi$ and second term (b) refers to two-pion emission: $\Upsilon(nS)\to\pi\pi B\bar B\to\pi\pi\Upsilon(n'S)$. The one-parameter formula for the di-pion mass distribution is derived, $\frac{dw}{dq}\sim$(phase space) $|\eta-x|^2$, where $x=\frac{q^2-4m^2_\pi}{q^2_{max}-4m^2_\pi},$ $q^2\equiv M^2_{\pi\pi}$. The parameter $\eta$ dependent on the process is calculated, using SHO wave functions and imposing PCAC restrictions (Adler zero) on amplitudes a,b. The resulting di-pion mass distributions are in agreement with experimental data.Comment: 62 pages,8 tables,7 figure

Effective Lagrangian for sˉbg\bar{s}bg and sˉbγ\bar{s}b\gamma Vertices in the mSUGRA model

Complete expressions of the $\bar{s}bg$ and $\bar{s}b\gamma$ vertices are derived in the framework of supersymmetry with minimal flavor violation. With the minimal supergravity (mSUGRA) model, a numerical analysis of the supersymmetric contributions to the Wilson Coefficients at the weak scale is presented.Comment: 12 pages + 7 ps figures, Late