No well-defined remnant Fermi surface in Sr2CuO2Cl2

In angle-resolved photoelectron spectra of the antiferromagnetic insulators Ca2CuO2Cl2 and Sr2CuO2Cl2 a sharp drop of the spectral intensity of the lowest-lying band is observed along a line in k space equivalent to the Fermi surface of the optimally doped high-temperature superconductors. This was interpreted as a signature of the existence of a remnant Fermi surface in the insulating phase of the high-temperature superconductors. In this paper it is shown that the drop of the spectral intensity is not related to the spectral function but is a consequence of the electron-photon matrix elementComment: 4 pages, 3 figure

Polycyclic aromatic hydrocarbons contaminants in black-lip (pearl) oyster Pinctada margaritifera from Kish Island (Persian Gulf)

Twenty-four Black-lip Oysters (Pinctada margaritifera ) were collected in summer (July) 2004 from six coastal locations in Kish Island (Persian Gulf) and were analyzed at the analytical laboratory of Great Lakes Institute for Environmental Research at the University of Windsor according to the chemical analysis procedures which has been accredited by the Canadian Association for Environmental Analysis Laboratories (CAEAL). In order to obtain information on bioavailability of sixteen EPA priority polycyclic aromatic hydrocarbons (PAHs), concentration of 2 to 6-ring PAHs was determined for all samples with application of a gas chromatograph with a mass selective detector. Oysters from Big Coral site exhibited a wide range of total PAH concentration (1.07 to 77.66 ng/g wet weight). The lowest value (oysters from Foreigner’s Pelage) and highest values were 0.7 and 36.33 ng/g wet weight respectively. Comparison of the PAH concentrations in oysters with sediments collected from the same locations showed that the overall bioaccumulation has been performed through the movement of water-soluble lower molecular weight (LMW) PAHs to the oysters in the studied area

Evaluation of a Floating Bird Diverter

Hazing at oil spills can reduce bird mortalities. This study evaluated the effectiveness of the Firefly Pond Diverter™ (Firefly Diverters LLC, Grantsville, UT), a device that floats on the water and is claimed to use motion, reflectivity, and ultraviolet (UV) and visible light emissions to alert and repel birds. The diverter could be useful at a spill, but little is known about how waterbirds would respond. The objectives of this study were to determine if waterbirds were repelled to a greater degree by the diverter compared to a simple novel object (a life ring), to identify the species that responded to the diverter, and determine if birds habituate to the diverter. The study was conducted in December 2007 in a stormwater retention basin in Woodland, California. We divided the study into a 3-day pretreatment period and a 6-day treatment period and counted birds in the morning and afternoon each day. On each day during the treatment period we randomly selected 2 areas of the basin and anchored 2 diverters in one area and 2 life rings in a second area. We moved the diverters and the life rings to new locations daily. During the bird counts we recorded all birds within 15.2 m of each diverter or life ring. For the basin as a whole, we found the temporal pattern of use (fewer birds present in the morning than the afternoon) and number of birds using the basin did not change with the deployment of the diverters and life rings. Species composition was similar during the pretreatment and treatment periods. Gulls, geese, and diving ducks accounted for over 90% of the birds, with gulls most numerous. We observed 7 and 9 species of birds within 15.2 m of the diverters and life rings, respectively. Gulls represented 91% and 81% of the birds near the diverters and the life rings, respectively. There was no difference in the number of birds within 15.2 m of the diverters or the life rings. There also was no difference in the number of birds within 15.2 m of the diverters or \u3e 15.2 m from the diverters. We found the same relationship for the life rings. After field work concluded we were informed that rotation of the flappers on the diverters and an ultraviolet index (UVI) \u3e2 were critical for the diverter to function. During the treatment period there was wind sufficient to spin the flappers during 7 of 12 counts. We observed birds within 15.2 m of the diverters on 6 out of 7 counts with wind. As reported in local newspapers, the UVI was never \u3e2 during the treatment period. If UV radiation has any effect on performance, then December, a month with low UVI values in northern California, was not the optimum time to test. The diverters did not repel birds during this study. It is not known if the diverters will repel birds during conditions of higher UVI. Additional research should be undertaken

Early Results from the Wisconsin H-Alpha Mapper Southern Sky Survey

After a successful eleven-year campaign at Kitt Peak, we moved the Wisconsin H-Alpha Mapper (WHAM) to Cerro Tololo in early 2009. Here we present some of the early data after a few months under southern skies. These maps begin to complete the first all-sky, kinematic survey of the diffuse H-alpha emission from the Milky Way. Much of this emission arises from the Warm Ionized Medium (WIM), a significant component of the ISM that extends a few kiloparsecs above the Galactic disk. While this first look at the data focuses on the H-alpha survey, WHAM is also capable of observing many other optical emission lines, revealing fascinating trends in the temperature and ionization state of the WIM. Our ongoing studies of the physical conditions of diffuse ionized gas will continue from the southern hemisphere following the H-alpha survey. In addition, future observations will cover the full velocity range of the Magellanic Stream, Bridge, and Clouds to trace the ionized gas associated with these neighboring systems.Comment: 4 pages, 2 figures. To appear in "The Dynamic ISM: A celebration of the Canadian Galactic Plane Survey," ASP Conference Serie

Densities and filling factors of the DIG in the Solar neighbourhood

For the first time we have combined dispersion measures and emission measures towards 38 pulsars at KNOWN distances from which we derived the mean electron density in clouds, N_c, and their volume filling factor, F_v, averaged along the line of sight. The emission measures were corrected for absorption by dust and contributions from beyond the pulsar distance. Results: The scale height of the electron layer for our sample is 0.93+/-0.13 kpc and the midplane electron density is 0.023+/-0.004 cm^-3, in agreement with earlier results. The average density along the line of sight is = 0.018+/-0.002 cm^-3 and nearly constant. Since = F_v N_c, an inverse relationship between F_v and N_c is expected. We find F_v(N_c) = (0.011+/-0.003) N_c^{-1.20+/-0.13}, which holds for the ranges N_c = 0.05-1 cm^-3 and F_v = 0.4-0.01. Near the Galactic plane the dependence of F_v on N_c is significantly stronger than away from the plane. F_v does not systematically change along or perpendicular to the Galactic plane, but the spread about the mean value of 0.08+/-0.02 is considerable. Conclusions: The inverse F_v-N_c relation is consistent with a hierarchical, fractal density distribution in the diffuse ionized gas (DIG) caused by turbulence. The observed near constancy of then is a signature of fractal structure in the ionized medium, which is most pronounced outside the thin disk.Comment: 9 pages, 9 figures. Accepted for publication in A&

Observations of the Extended Distribution of Ionized Hydrogen in the Plane of M31

We have used the Wisconsin H-Alpha Mapper (WHAM) to observe the spatially extended distribution of ionized hydrogen in M31 beyond the stellar disk. We obtained five sets of observations, centered near the photometric major axis of M31, that extend from the center of the galaxy to just off the edge of the southwestern HI disk. Beyond the bright stellar disk, but within the HI disk, weak H-alpha is detected with an intensity I(H-alpha) = 0.05 (+0.01 / -0.02) Rayleighs. Since M31 is inclined 77 degrees with respect to the line of sight, this implies that the ambient intergalactic ionizing flux onto each side of M31 is Phi_0 <= 1.6 x 10^4 photons cm^-2 s^-1. Just beyond the outer boundary of the HI disk we find no significant detection of H-alpha and place an upper limit I(H-alpha) <= 0.019 Rayleighs.Comment: To appear in ApJ Letters; 12 pages, 4 figure

Determination of the Far-Infrared Cosmic Background Using COBE/DIRBE and WHAM Data

Determination of the cosmic infrared background (CIB) at far infrared wavelengths using COBE/DIRBE data is limited by the accuracy to which foreground interplanetary and Galactic dust emission can be modeled and subtracted. Previous determinations of the far infrared CIB (e.g., Hauser et al. 1998) were based on the detection of residual isotropic emission in skymaps from which the emission from interplanetary dust and the neutral interstellar medium were removed. In this paper we use the Wisconsin H-alpha Mapper (WHAM) Northern Sky Survey as a tracer of the ionized medium to examine the effect of this foreground component on determination of the CIB. We decompose the DIRBE far infrared data for five high Galactic latitude regions into H I and H-alpha correlated components and a residual component. We find the H-alpha correlated component to be consistent with zero for each region, and we find that addition of an H-alpha correlated component in modeling the foreground emission has negligible effect on derived CIB results. Our CIB detections and 2 sigma upper limits are essentially the same as those derived by Hauser et al. and are given by nu I_nu (nW m-2 sr-1) < 75, < 32, 25 +- 8, and 13 +- 3 at 60, 100, 140, and 240 microns, respectively. Our residuals have not been subjected to a detailed anisotropy test, so our CIB results do not supersede those of Hauser et al. We derive upper limits on the 100 micron emissivity of the ionized medium that are typically about 40% of the 100 micron emissivity of the neutral atomic medium. This low value may be caused in part by a lower dust-to-gas mass ratio in the ionized medium than in the neutral medium, and in part by a shortcoming of using H-alpha intensity as a tracer of far infrared emission.Comment: 38 pages, 8 figures. Accepted for publication in Ap

Multiwavelength observations of the M15 intermediate velocity cloud

We present Westerbork Synthesis Radio Telescope HI images, Lovell Telescope multibeam HI wide-field mapping, Wisconsin H-alpha Mapper facility images, William Herschel Telescope longslit echelle CaII observations, and IRAS ISSA 60 and 100 micron coadded images towards the intermediate velocity cloud located in the general direction of the M15 globular cluster. When combined with previously-published Arecibo data, the HI gas in the IVC is found to be clumpy, with peak HI column density of 1.5x10^(20) cm^(-2), inferred volume density (assuming spherical symmetry) of 24 cm^(-3)/(D kpc), and maximum brightness temperature at a resolution of 81x14 arcsec of 14 K. The HI gas in the cloud is warm, with a minimum FWHM value of 5 km/s, corresponding to a kinetic temperature, in the absence of turbulence, of 540 K. There are indications in the HI data of 2-component velocity structure in the IVC, indicative of cloudlets. This velocity structure is also tentatively seen in the CaK spectra, although the SNR is low. The main IVC condensation is detected by WHAM in H-alpha with intensities uncorrected for Galactic absorption of upto 1.3 Rayleigh, indicating that the cloud is partially ionised. The FWHM of the ionised component, at a resolution of 1 degree, exceeds 30 km/s. The spatial and velocity coincidence of the H-alpha and HI peaks in emission is qualitatively good. Finally, the 100 and 60 micron IRAS images show spatial coincidence over a 0.7 degree field, with low and intermediate-velocity gas, respectively, indicating that the IVC may contain dust.Comment: MNRAS, in pres