Scaling of broadband dielectric data of glass-forming liquids and plastic crystals

The Nagel-scaling and the modified scaling procedure proposed recently by Dendzik et al. have been applied to broadband dielectric data on two glass- forming liquids (glycerol and propylene carbonate) and three plastic crystals (ortho-carborane, meta-carborane, and 1-cyano-adamantane). Our data extend the upper limit of the abscissa range to considerably higher values than in previously published analyses. At the highest frequencies investigated, deviations from a single master curve show up which are most pronounced in the Dendzik-scaling plot. The loss curves of the plastic crystals do not scale in the Nagel-plot, but they fall onto a separate master curve in the Dendzik-plot. In addition, we address the question of a possible divergence of the static susceptibility near the Vogel-Fulcher temperature. For this purpose, the low-temperature evolution of the high-frequency wing of the dielectric loss peaks is investigated in detail. No convincing proof for such a divergence can be deduced from the present broadband data.Comment: 7 pages including 6 figures submitted to Eur. Phys. J.

The excess wing in the dielectric loss of glass-forming ethanol: A relaxation process

A detailed dielectric investigation of liquid, supercooled liquid, and glassy ethanol reveals a third relaxation process, in addition to the two processes already known. The relaxation time of the newly detected process exhibits strong deviations from thermally activated behavior. Most important, this process is the cause of the apparent excess wing, which was claimed to be present in the dielectric loss spectra of glass-forming ethanol. In addition, marked deviations of the spectra of ethanol from the scaling proposed by Dixon and Nagel have been detected.Comment: 8 pages including 4 figures submitted to Phys. Rev.

The Excess Wing in the Dielectric Loss of Glass-Formers: A Johari-Goldstein beta-Relaxation?

Dielectric loss spectra of glass-forming propylene carbonate and glycerol at temperatures above and below T_g are presented. By performing aging experiments lasting up to five weeks, equilibrium spectra below T_g have been obtained. During aging, the excess wing, showing up as a second power law at high frequencies, develops into a shoulder. The results strongly suggest that the excess wing, observed in a variety of glass formers, is the high-frequency flank of a beta-relaxation.Comment: submitted to Phys. Rev. Lett., 4 figures, revised version after referee report

1420 MHz Continuum Absorption Towards Extragalactic Sources in the Galactic Plane

We present a 21-cm emission-absorption study towards extragalactic sources in the Canadian Galactic Plane Survey (CGPS). We have analyzed HI spectra towards 437 sources with S > 150 mJy, giving us a source density of 0.6 sources per square degree at arcminute resolution. We present the results of a first analysis of the HI temperatures, densities, and feature statistics. Particular emphasis is placed on 5 features with observed spin temperatures below 40 K. We find most spin temperatures in the range from 40 K to 300 K. A simple HI two-component model constrains the bulk of the cold component to temperatures (T_c) between 40 K and 100 K. T_c peaks in the Perseus arm region and clearly drops off with Galactocentric radius, R, beyond that. The HI density follows this trend, ranging from a local value of 0.4 cm^{-3} to less than 0.1 cm^{-3} at R = 20 kpc. We find that HI emission alone on average traces about 75% of the total HI column density, as compared to the total inferred by the emission and absorption. Comparing the neutral hydrogen absorption to CO emission no correlation is found in general, but all strong CO emission is accompanied by a visible HI spectral feature. Finally, the number of spectral HI absorption features per kpc drop off exponentially with increasing R.Comment: 13 pages, 13 figures, Accepted for March 2004 Ap

Discriminating cool-water from warm-water carbonates and their diagenetic environments using element geochemistry: the Oligocene Tikorangi Formation (Taranaki Basin) and the dolomite effect

Fields portrayed within bivariate element plots have been used to distinguish between carbonates formed in warm- (tropical) water and cool- (temperate) water depositional settings. Here, element concentrations (Ca, Mg, Sr, Na, Fe, and Mn) have been determined for the carbonate fraction of bulk samples from the late Oligocene Tikorangi Formation, a subsurface, mixed dolomite-calcite, cool-water limestone sequence in Taranaki Basin, New Zealand. While the occurrence of dolomite is rare in New Zealand Cenozoic carbonates, and in cool-water carbonates more generally, the dolomite in the Tikorangi carbonates is shown to have a dramatic effect on the "traditional" positioning of cool-water limestone fields within bivariate element plots. Rare undolomitised, wholly calcitic carbonate samples in the Tikorangi Formation have the following average composition: Mg 2800 ppm; Ca 319 100 ppm; Na 800 ppm; Fe 6300 ppm; Sr 2400 ppm; and Mn 300 ppm. Tikorangi Formation dolomite-rich samples (>15% dolomite) have average values of: Mg 53 400 ppm; Ca 290 400 ppm; Na 4700 ppm; Fe 28 100 ppm; Sr 5400 ppm; and Mn 500 ppm. Element-element plots for dolomite-bearing samples show elevated Mg, Na, and Sr values compared with most other low-Mg calcite New Zealand Cenozoic limestones. The increased trace element contents are directly attributable to the trace element-enriched nature of the burial-derived dolomites, termed here the "dolomite effect". Fe levels in the Tikorangi Formation carbonates far exceed both modern and ancient cool-water and warm-water analogues, while Sr values are also higher than those in modern Tasmanian cool-water carbonates, and approach modern Bahaman warm-water carbonate values. Trace element data used in conjunction with more traditional petrographic data have aided in the diagenetic interpretation of the carbonate-dominated Tikorangi sequence. The geochemical results have been particularly useful for providing more definitive evidence for deep burial dolomitisation of the deposits under the influence of marine-modified pore fluids

Soliton Magnetization Dynamics in Spin-Orbit Coupled Bose-Einstein Condensates

Ring-trapped Bose-Einstein condensates subject to spin-orbit coupling support localized dark soliton excitations that show periodic density dynamics in real space. In addition to the density feature, solitons also carry a localized pseudo-spin magnetization that exhibits a rich and tunable dynamics. Analytic results for Rashba-type spin-orbit coupling and spin-invariant interactions predict a conserved magnitude and precessional motion for the soliton magnetization that allows for the simulation of spin-related geometric phases recently seen in electronic transport measurements.Comment: 3 figures, 5 page