CP Violation in Fermion Pair Decays of Neutral Boson Particles

We study CP violation in fermion pair decays of neutral boson particles with spin 0 or 1. We study a new asymmetry to measure CP violation in $\eta, K_L \rightarrow \mu^+\mu^-$ decays and discuss the possibility of measuring it experimentally. For the spin-1 particles case, we study CP violation in the decays of $J/\psi$ to $SU(3)$ octet baryon pairs. We show that these decays can be used to put stringent constraints on the electric dipole moments of $\Lambda$, $\Sigma$ and $\Xi$.Comment: 14p, OZ-93/22, UM-93/89, OITS 51

Wave Scattering through Classically Chaotic Cavities in the Presence of Absorption: An Information-Theoretic Model

We propose an information-theoretic model for the transport of waves through a chaotic cavity in the presence of absorption. The entropy of the S-matrix statistical distribution is maximized, with the constraint $=\alpha n$: n is the dimensionality of S, and $0\leq \alpha \leq 1, \alpha =0(1)$ meaning complete (no) absorption. For strong absorption our result agrees with a number of analytical calculations already given in the literature. In that limit, the distribution of the individual (angular) transmission and reflection coefficients becomes exponential -Rayleigh statistics- even for n=1. For $n\gg 1$ Rayleigh statistics is attained even with no absorption; here we extend the study to $\alpha <1$. The model is compared with random-matrix-theory numerical simulations: it describes the problem very well for strong absorption, but fails for moderate and weak absorptions. Thus, in the latter regime, some important physical constraint is missing in the construction of the model.Comment: 4 pages, latex, 3 ps figure

Magnetic Soliton and Soliton Collisions of Spinor Bose-Einstein Condensates in an Optical Lattice

We study the magnetic soliton dynamics of spinor Bose-Einstein condensates in an optical lattice which results in an effective Hamiltonian of anisotropic pseudospin chain. A modified Landau-Lifshitz equation is derived and exact magnetic soliton solutions are obtained analytically. Our results show that the time-oscillation of the soliton size can be controlled in practical experiment by adjusting of the light-induced dipole-dipole interaction. Moreover, the elastic collision of two solitons is investigated.Comment: 16 pages, 5 figure

Silver enhancement of Nanogold particles during freeze substitution for electron microscopy

Recent advances in rapid freezing and fixation by freeze substitution have allowed structural cell biologists to apply these reliable modes of sample preparation to a wide range of specimens and scientific problems. Progress in electron tomography has produced cellular images with resolution approaching 4 nm in 3D, but our ability to localize macromolecules in these well-fixed, well-resolved samples has remained limited. When light fixation and low temperature embedding are employed with appropriate resins, immuno-localizations can recognize antigens at a section's surface, but labelling is therefore confined, not throughout the section's depth. Small, electron-dense markers, like Nanogold®, will often enter a living cell, serving as reliable tracers for endocytic activity, but these markers are usually too small to be visible in the context of a cell. We have developed a method for the silver enhancement of Nanogold particles that works during freeze substitution in organic solvents at low temperature. Here, we describe the development of this method, based on in vitro tests of reagents and conditions. We then show results from application of the method to an in vivo system, using Nanogold to track the internalization of immunoglobulin by neonatal murine intestinal epithelium, a specific example of receptor-mediated membrane traffic

Spin photocurrent, its spectra dependence, and current-induced spin polarization in an InGaAs/InAlAs two-dimensional electron gas

Converse effect of spin photocurrent and current induced spin polarization are experimentally demonstrated in the same two-dimensional electron gas system with Rashba spin splitting. Their consistency with the strength of the Rashba coupling as measured from beating of the Shubnikov-de Haas oscillations reveals a unified picture for the spin photocurrent, current-induced spin polarization and spin orbit coupling. In addition, the observed spectral inversion of the spin photocurrent indicates the system with dominating structure inversion asymmetry.Comment: 13 pages, 4 figure

Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)

The phase diagram of non-hydrated Na(x)CoO(2) has been determined by changing the Na content x using a series of chemical reactions. As x increases from 0.3, the ground state goes from a paramagnetic metal to a charge-ordered insulator (at x=1/2) to a `Curie-Weiss metal' (around 0.70), and finally to a weak-moment magnetically ordered state (x>0.75). The unusual properties of the state at 1/2 (including particle-hole symmetry at low T and enhanced thermal conductivity) are described. The strong coupling between the Na ions and the holes is emphasized.Comment: 4 pages with 3 figures, changed conten

Moisture absorption characteristics and mechanical degradation of composite lattice truss core sandwich panel in a hygrothermal environment

This paper investigates the impact of hygrothermal aging upon the compressive mechanical properties of carbon fiber reinforced plastics (CFRP) composite sandwich panels with a tetrahedral truss core. Gravimetric absorption data, through accelerated moisture absorption tests, were presented for three different temperatures of 30 °C, 55 °C and 80 °C. Predictions by Fickian and Langmuir-type diffusion models were compared to evaluate which one best describe the moisture diffusion process in the sandwich panels. A subroutine implementing the Langmuir-type diffusion model in ABAQUS was developed to simulate the variations of moisture concentration. The compressive properties of composite strut and tetrahedral truss cores sandwich panel after hygrothermal aging at different temperatures were tested, respectively. The experimental results indicated that the degradation of compressive properties of composite sandwich panel was induced by the combined effect of temperature and moisture absorption. Analytical expressions were developed to predict the compressive strength and stiffness of the sandwich panel following hygrothermal aging. A good agreement was found between the predictions by finite element, analytical model and experimental results

Evolution of population with sexual and asexual reproduction in changing environment

Using a lattice model based on Monte Carlo simulations, we study the role of the reproduction pattern on the fate of an evolving population. Each individual is under the selection pressure from the environment and random mutations. The habitat ("climate") is changing periodically. Evolutions of populations following two reproduction patterns are compared, asexual and sexual. We show, via Monte Carlo simulations, that sexual reproduction by keeping more diversified populations gives them better chances to adapt themselves to the changing environment. However, in order to obtain a greater chance to mate, the birth rate should be high. In the case of low birth rate and high mutation probability there is a preference for the asexual reproduction.Comment: 11 pages including figs., for Int. J. Mod. Phys. C 15, issue 2 (2004

Photoemission Spectroscopy and the Unusually Robust One Dimensional Physics of Lithium Purple Bronze

Temperature dependent photoemission spectroscopy in Li0.9Mo6O17 contributes to evidence for one dimensional physics that is unusually robust. Three generic characteristics of the Luttinger liquid are observed, power law behavior of the k-integrated spectral function down to temperatures just above the superconducting transition, k-resolved lineshapes that show holon and spinon features, and quantum critical (QC) scaling in the lineshapes. Departures of the lineshapes and the scaling from expectations in the Tomonaga Luttinger model can be partially described by a phenomenological momentum broadening that is presented and discussed. The possibility that some form of 1d physics obtains even down to the superconducting transition temperature is assessed.Comment: submitted to JPCM, Special issue article "Physics in one dimension