High resolution spectroscopy of (lambda)(12)B by electroproduction

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.     

Evolution of the electronic structure of 1T-Cu(x)TiSe(2)

The electronic structure of a new charge-density-wave system or superconductor, 1T-Cu(x)TiSe(2), has been studied by photoemission spectroscopy. A correlated semiconductor band structure is revealed for the undoped case, which resolves a long-standing controversy in the system. With Cu doping, the charge-density wave is suppressed by the raising of the chemical potential, while the superconductivity is enhanced by the enhancement of the density of states, and possibly suppressed at higher doping by the strong scattering.     

Partonic Flow and phi-Meson production in Au+Au collisions at sqrt radical sNN = 200 GeV

We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.     

Dynamically maintained spike timing sequences in networks of pulse-coupled oscillators with delays

We demonstrate the widespread occurrence of dynamically maintained spike timing sequences in recurrent networks of pulse-coupled spiking neurons with large time delays. The sequences occur in transient, quasistable phase-locking states. The system spontaneously jumps between these states. This collective dynamics enables the system to generate a large number of distinct precise spike timing sequences. Distributed time delays play a constructive role by enhancing the dominance in parameter space of the dynamics responsible for producing the large variety of spike timing sequences.     

Magnetocaloric properties of DyCo2−xGax alloys

The influence of the substitution of Ga atoms for Co atoms in DyCo₂ compounds on magnetocaloric properties has been investigated. A series of DyCo_2−xGa_x alloys with x=0, 0.03, 0.06, 0.1, 0.15, and 0.2 was prepared by the arc-melting method for this investigation. Experimental results revealed that the Ga substitution for Co in DyCo₂ can form a single phase with the cubic Laves phase structure up to x=0.2. As the Ga content x increases, the lattice parameter and the Curie temperature T_c increases from 143 to 196 K linearly. The maximum magnetic entropy changes in a low field change of 0-1.5 T, increasing from 8.24 to 10.61 J/K kg when the Ga content x increases from 0 to 0.03, but decreasing gradually to 3.51 J/K kg as the Ga content further increases to x=0.2. All the samples show a relatively large magnetic entropy change with very small hysteresis loss.     

Charge and orbital ordering in Na0.5CoO2

The ground state of Na_0.5CoO₂ has been calculated using the full potential local orbital method and local density approximation plus Hubbard U (); the results demonstrate that charge and orbital ordering evidently exist in the present system in association with the antiferromagnetic state. Notable structural features observed between 300 and 30 K have been carefully examined using in situ TEM investigations, a superstructure with a wave vector of Q1=a^∗/2, becoming commonly visible below , can be interpreted as the charge/orbital ordering on the Co1 and Co2 sites. Moreover, we have also observed another notable superstructure with Q2=a^∗/4 below the phase transition of , which suggests a more complicated orbital ordered state existing at lower temperatures.     

A realization of digital wireless transmission for MRI signals based on 802.11b

In this paper, a digital wireless transmission system based on 802.11b standard for magnetic resonance imaging (MRI) application is designed and built for the first time to eliminate the interference aroused by coil array cables. The analysis shows that the wireless receiver has a very high sensitivity to detect MRI signals. The modulation technique of differential quadrature phase shift keyed (DQPSK) can be applied to MRI data transmission with rate of 2 Mbps and bandwidth of 2 MHz. The bench test verifies that this wireless link has a dynamic range over 86 dB supporting up to 3 T MRI system data transmission. The 2D spin echo imaging of phantom is performed and the SNR of the image obtained by the wireless transmission can be comparable with that got by the coaxial cables.     

Geometric phase in a composite system subjected to decoherence

In this paper, we investigate the geometric phase of a composite system which is composed of two spin- particles driven by a time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic field. Using the quantum jump approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence. The results show that the lowest order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem driven by time-varying magnetic field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of the magnetic field.     

Is constituent quark scaling a unique sign of parton recombination?

We study the transverse momentum dependence of the anisotropic flow v₂ for π, K, nucleon, Λ, Ξ and Ω for Au+Au collisions at within two independent string-hadron transport approaches (RQMD and UrQMD). Although both models reach only 60% of the absolute magnitude of the measured v₂, they both predict the particle-type dependence of v₂ as observed by the RHIC experiments: v₂ exhibits a hadron-mass hierarchy in the low p_T region and a number-of-constituent-quark (NCQ) dependence in the intermediate p_T region. The failure of the hadronic models to reproduce the absolute magnitude of the observed v₂ indicates that transport calculations of heavy-ion collisions at RHIC must incorporate interactions among quarks and gluons in the early, hot and dense phase. The presence of an NCQ scaling in the string-hadron model results suggests that the particle-type dependences observed in heavy-ion collisions at intermediate p_T might be related to the hadronic cross sections in vacuum rather than to the hadronization process itself.     

Monolithic 160 Gbit/s optical time-division multiplexer

We present the design and experimental characterization of a monolithic optical time-division multiplexer (MUX) for 160 Gbit/s operation based on periodically poled lithium niobate (PPLN) waveguides. Its key figures of merit agree well with theoretical predictions and meet or exceed those of a previously demonstrated PPLN-planar-light-wave-circuit hybrid MUX. The monolithic design has a simpler layout and higher efficiency while keeping the cross talk low.