Quantum transfer matrix method for one-dimensional disordered electronic systems

We develop a novel quantum transfer matrix method to study thermodynamic properties of one-dimensional (1D) disordered electronic systems. It is shown that the partition function can be expressed as a product of $2\times2$ local transfer matrices. We demonstrate this method by applying it to the 1D disordered Anderson model. Thermodynamic quantities of this model are calculated and discussed.Comment: 7 pages, 10 figure

Differential Actions of Ethanol and Trichloroethanol at Sites in the M3 and M4 Domains of the NMDA Receptor GluN2A (NR2A) Subunit

Background and purpose:  Alcohol produces its behavioural effects in part due to inhibition of N-methyl-d-aspartate (NMDA) receptors in the CNS. Previous studies have identified amino acid residues in membrane-associated domains 3 (M3) and 4 (M4) of the NMDA receptor that influence ethanol sensitivity. In addition, in other alcohol-sensitive ion channels, sedative-hypnotic agents have in some cases been shown to act at sites distinct from the sites of ethanol action. In this study, we compared the influence of mutations at these sites on sensitivity to ethanol and trichloroethanol, a sedative-hypnotic agent that is a structural analogue of ethanol. Experimental approach:  We constructed panels of mutants at ethanol-sensitive positions in the GluN2A (NR2A) NMDA receptor subunit and transiently expressed these mutants in human embryonic kidney 293 cells. We used whole-cell patch-clamp recording to assess the actions of ethanol and trichloroethanol in these mutant NMDA receptors. Key results:  Ethanol sensitivity of mutants at GluN2A(Ala825) was not correlated with any physicochemical measures tested. Trichloroethanol sensitivity was altered in two of three ethanol-insensitive mutant GluN2A subunits: GluN2A(Phe637Trp) in M3 and GluN2A(Ala825Trp) in M4, but not GluN2A(Met823Trp). Trichloroethanol sensitivity decreased with increasing molecular volume at Phe637 or increasing hydrophobicity at Ala825 and was correlated with ethanol sensitivity at both sites. Conclusions and implications:  Evidence obtained to date is consistent with a role of GluN2A(Ala825) as a modulatory site for ethanol and trichloroethanol sensitivity, but not as a binding site. Trichloroethanol appears to inhibit the NMDA receptor in a manner similar, but not identical to, that of ethanol

Difference of optical conductivity between one- and two-dimensional doped nickelates

We study the optical conductivity in doped nickelates, and find the dramatic difference of the spectrum in the gap ($\omega$\alt4 eV) between one- (1D) and two-dimensional (2D) nickelates. The difference is shown to be caused by the dependence of hopping integral on dimensionality. The theoretical results explain consistently the experimental data in 1D and 2D nickelates, Y$_{2-x}$Ca$_x$BaNiO$_5$ and La$_{2-x}$Sr$_x$NiO$_4$, respectively. The relation between the spectrum in the X-ray aborption experiments and the optical conductivity in La$_{2-x}$Sr$_x$NiO$_4$ is discussed.Comment: RevTeX, 4 pages, 4 figure

Dust-to-gas ratio, XCOX_{\rm CO} factor and CO-dark gas in the Galactic anticentre: an observational study

We investigate the correlation between extinction and H~{\sc i} and CO emission at intermediate and high Galactic latitudes (|b|>10\degr) within the footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic anticentre (XSTPS-GAC) on small and large scales. In Paper I (Chen et al. 2014), we present a three-dimensional dust extinction map within the footprint of XSTPS-GAC, covering a sky area of over 6,000\,deg$^2$ at a spatial angular resolution of 6\,arcmin. In the current work, the map is combined with data from gas tracers, including H~{\sc i} data from the Galactic Arecibo L-band Feed Array H~{\sc i} survey and CO data from the Planck mission, to constrain the values of dust-to-gas ratio $DGR=A_V/N({\rm H})$ and CO-to-$\rm H_2$ conversion factor $X_{\rm CO}=N({\rm H_2})/W_{\rm CO}$ for the entire GAC footprint excluding the Galactic plane, as well as for selected star-forming regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse gas in the northern Galactic hemisphere. For the whole GAC footprint, we find $DGR=(4.15\pm0.01) \times 10^{-22}$\,$\rm mag\,cm^{2}$ and $X_{\rm CO}=(1.72 \pm 0.03) \times 10^{20}$\,$\rm cm^{-2}\,(K\,km\,s^{-1})^{-1}$. We have also investigated the distribution of "CO-dark" gas (DG) within the footprint of GAC and found a linear correlation between the DG column density and the $V$-band extinction: $N({\rm DG}) \simeq 2.2 \times 10^{21} (A_V - A^{c}_{V})\,\rm cm^{-2}$. The mass fraction of DG is found to be $f_{\rm DG}\sim 0.55$ toward the Galactic anticentre, which is respectively about 23 and 124 per cent of the atomic and CO-traced molecular gas in the same region. This result is consistent with the theoretical work of Papadopoulos et al. but much larger than that expected in the $\rm H_2$ cloud models by Wolfire et al.Comment: 11 pages, 7 figures, accepted for publication in MNRA

Entanglement-enhanced measurement of a completely unknown phase

The high-precision interferometric measurement of an unknown phase is the basis for metrology in many areas of science and technology. Quantum entanglement provides an increase in sensitivity, but present techniques have only surpassed the limits of classical interferometry for the measurement of small variations about a known phase. Here we introduce a technique that combines entangled states with an adaptive algorithm to precisely estimate a completely unspecified phase, obtaining more information per photon that is possible classically. We use the technique to make the first ab initio entanglement-enhanced optical phase measurement. This approach will enable rapid, precise determination of unknown phase shifts using interferometry.Comment: 6 pages, 4 figure