Phase-reference VLBI Observations of the Compact Steep-Spectrum Source 3C 138

We investigate a phase-reference VLBI observation that was conducted at 15.4 GHz by fast switching VLBA antennas between the compact steep-spectrum radio source 3C 138 and the quasar PKS 0528+134 which are about 4$^\circ$ away on the sky. By comparing the phase-reference mapping with the conventional hybrid mapping, we demonstrate the feasibility of high precision astrometric measurements for sources separated by 4$^\circ$. VLBI phase-reference mapping preserves the relative phase information, and thus provides an accurate relative position between 3C 138 and PKS 0528+134 of $\Delta\alpha=-9^m46^s.531000\pm0^s.000003$ and $\Delta\delta=3^\circ6^\prime26^{\prime\prime}.90311\pm0^{\prime\prime}.00007$ (J2000.0) in right ascension and declination, respectively. This gives an improved position of the nucleus (component A) of 3C 138 in J2000.0 to be RA=$05^h 21^m 9^s.885748$ and Dec=$16^\circ 38' 22''.05261$ under the assumption that the position of calibrator PKS 0528+134 is correct. We further made a hybrid map by performing several iterations of CLEAN and self-calibration on the phase-referenced data with the phase-reference map as an input model for the first phase self-calibration. Compared with the hybrid map from the limited visibility data directly obtained from fringe fitting 3C 138 data, this map has a similar dynamic range, but a higher angular resolution. Therefore, phase-reference technique is not only a means of phase connection, but also a means of increasing phase coherence time allowing self-calibration technique to be applied to much weaker sources.Comment: 9 pages plus 2 figures, accepted by PASJ (Vol.58 No.6

Absence of magnetic long range order in Y2_{2}CrSbO7_{7}: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore

The consequences of nonmagnetic-ion dilution for the pyrochlore family Y$_{2}$($M_{1-x}N_{x}$)$_{2}$O$_{7}$ ($M$ = magnetic ion, $N$ = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y$_{2}$CrSbO$_{7}$ ($x$ = 0.5), in which the magnetic sites (Cr$^{3+}$) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, $\Theta_\mathrm{{CW}}$ = 20.1(6) K, our high-resolution neutron powder diffraction measurements detect no sign of magnetic long range order down to 2 K. In order to understand our observations, we performed numerical simulations to study the bond-disorder introduced by the ionic size mismatch between $M$ and $N$. Based on these simulations, bond-disorder ($x_{b}$ $\simeq$ 0.23) percolates well ahead of site-disorder ($x_{s}$ $\simeq$ 0.61). This model successfully reproduces the critical region (0.2 < $x$ < 0.25) for the N\'eel to spin glass phase transition in Zn(Cr$_{1-x}$Ga$_{x}$)$_{2}$O$_{4}$, where the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the $M/N$-sublattice in Y$_{2}$($M_{1-x}N_{x}$)$_{2}$O$_{7}$, and the rapid drop in magnetically ordered moment in the N\'eel phase [Lee $et$ $al$, Phys. Rev. B 77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder on magnetic frustration, even in ferromagnets

Dynamical evolution of scalar perturbation in Ho\v{r}ava-Lifshitz black-hole spacetimes

We study the dynamical evolution of a massless scalar perturbation in the Ho\v{r}ava-Lifshitz black-hole spacetimes with the coupling constants $\lambda={1/3}$, $\lambda={1/2}$ and $\lambda=3$, respectively. Our calculation shows that, for the three cases, the scalar perturbations decay without any oscillation in which the decay rate imprints the parameter of the Ho\v{r}ava-Lifshitz black hole. The results are quite different from those in the Schwarzschild AdS black hole and can help us understand more about the Ho\v{r}ava-Lifshitz gravity.Comment: 14 pages, 5 figure

Wigner-Moyal description of free variable mass Klein-Gordon fields

A system of coupled kinetic transport equations for the Wigner distributions of a free variable mass Klein-Gordon field is derived. This set of equations is formally equivalent to the full wave equation for electromagnetic waves in nonlinear dispersive media, thus allowing for the description of broadband radiation-matter interactions and the associated instabilities. The standard results for the classical wave action are recovered in the short wavelength limit of the generalized Wigner-Moyal formalism for the wave equation.Comment: 9 pages, accepted for publication in Journal of Mathematical Physic

Representation of Pitch in Horizontal Space and Its Dependence on Musical and Instrumental Experience

Representation of pitch in horizontal space and its relationship to musical and instrumental experience was examined in three behavioral experiments. Each experiment investigated the influence of a task-irrelevant dimension (pitch or location) on the perception of a task-relevant dimension (location or pitch, respectively). Sine tones with nine different pitches were presented from nine locations, and participants estimated the pitch or location of the stimuli. Experiment 1 showed an influence of the (task irrelevant) pitch of presented stimuli on the perceived location of the stimuli in musically experienced participants only. This influence increased with the degree of musical training of participants. No influence was found of presented location on the perception of pitch. Experiments 2 and 3 investigated the influence of instrumental expertise comparing the responses of a group of flutists with a group of pianists. An interaction with instrumental expertise was found only in Experiment 3, where participants played shortly on their respective instruments before doing the perceptual judgments. The experiments indicate that musical training in general influence the pitch-location association, and pianistic experience in particular

A simple theory of dipole antennas

Simple and quantitatively accurate representation of current distribution in dipole antenna

The Economic Impact of the Nevada Clean Indoor Air Act in Clark County, Nevada – Preliminary Findings

Objective. The primary purpose of this exploratory study was to quantitatively evaluate the economic impact of the Nevada Clean Indoor Air Act (NCIAA) on businesses in Clark County. Methods. The goal of this research was to assess economic indicators over a ten year period utilizing measurable data points, including restaurant and drinking establishment employment rates, taxable sales, openings and closings, as well as slot gaming revenues. This ten year time period consisted of a seven year span prior to the enactment of the NCIAA, and three years post enactment. Researchers conceived this study as a means to independently evaluate and address the potential economic impact of a smoke-free law in a region dependent upon tourism and gaming. Results. Economic indicators did in fact decrease after the NCIAA was enforced but most of the declining trends began prior to the passage of the smoke-free act and are consistent with downward trends in other, non-NCIAA affected segments of our economy. Conclusion. The overall findings of this study are consistent with similar non-tobacco industry supported economic studies showing little or no statistically significant downward economic trends after passage of smoke-free legislation