Channelization architecture for wide-band slow light in atomic vapors

We propose a ``channelization'' architecture to achieve wide-band electromagnetically induced transparency (EIT) and ultra-slow light propagation in atomic Rb-87 vapors. EIT and slow light are achieved by shining a strong, resonant ``pump'' laser on the atomic medium, which allows slow and unattenuated propagation of a weaker ``signal'' beam, but only when a two-photon resonance condition is satisfied. Our wideband architecture is accomplished by dispersing a wideband signal spatially, transverse to the propagation direction, prior to entering the atomic cell. When particular Zeeman sub-levels are used in the EIT system, then one can introduce a magnetic field with a linear gradient such that the two-photon resonance condition is satisfied for each individual frequency component. Because slow light is a group velocity effect, utilizing differential phase shifts across the spectrum of a light pulse, one must then introduce a slight mismatch from perfect resonance to induce a delay. We present a model which accounts for diffusion of the atoms in the varying magnetic field as well as interaction with levels outside the ideal three-level system on which EIT is based. We find the maximum delay-bandwidth product decreases with bandwidth, and that delay-bandwidth product ~1 should be achievable with bandwidth ~50 MHz (~5 ns delay). This is a large improvement over the ~1 MHz bandwidths in conventional slow light systems and could be of use in signal processing applications.Comment: Published in SPIE Proceedings, Photonics West 2005 (San Jose, CA, Jan. 22-27, 2005

Observation of Quantum Shock Waves Created with Ultra Compressed Slow Light Pulses in a Bose-Einstein Condensate

We have used an extension of our slow light technique to provide a method for inducing small density defects in a Bose-Einstein condensate. These sub-resolution, micron-sized defects evolve into large amplitude sound waves. We present an experimental observation and theoretical investigation of the resulting breakdown of superfluidity. We observe directly the decay of the narrow density defects into solitons, the onset of the `snake' instability, and the subsequent nucleation of vortices.Comment: 15 pages, 5 figure

An Investigation of Sloan Digital Sky Survey Imaging Data and Multi-Band Scaling Relations of Spiral Galaxies (with Dynamical Information)

We have compiled a sample of 3041 spiral galaxies with multi-band gri imaging from the Sloan Digital Sky Survey (SDSS) Data Release 7 and available galaxy rotational velocities derived from HI line widths. We compare the data products provided through the SDSS imaging pipeline with our own photometry of the SDSS images, and use the velocities (V) as an independent metric to determine ideal galaxy sizes (R) and luminosities (L). Our radial and luminosity parameters improve upon the SDSS DR7 Petrosian radii and luminosities through the use of isophotal fits to the galaxy images. This improvement is gauged via VL and RV relations whose respective scatters are reduced by ~8% and ~30% compared to similar relations built with SDSS parameters. The tightest VRL relations are obtained with the i-band radius, R235i, measured at 23.5 mag/arcsec^-2, and the luminosity L235i, measured within R235i. Our VRL scaling relations compare well, both in scatter and slope, with similar studies (such comparisons however depend sensitively on the nature and size of the compared samples). The typical slopes, b, and observed scatters, sigma, of the i-band VL, RL and RV relations are bVL=0.27+/-0.01, bRL=0.41+/-0.01, bRV=1.52+/-0.07, and sigmaVL=0.074, sigmaRL=0.071, sigmaRV=0.154 dex. Similar results for the SDSS g and r bands are also provided. Smaller scatters may be achieved for more pruned samples. We also compute scaling relations in terms of the baryonic mass (stars + gas), Mbar, ranging from 10^8.7 Msol to 10^11.6 Msol. Our baryonic velocity-mass (VM) relation has slope 0.29+/-0.01 and a measured scatter sigma_meas = 0.076 dex. While the observed VL and VM relations have comparable scatter, the stellar and baryonic VM relations may be intrinsically tighter, and thus potentially more fundamental, than other VL relations of spiral galaxies.Comment: Submitted to MNRAS, comments welcom

Preliminary investigations on the single and combined cytotoxic effect of T-2 and HT-2 measured by Methyl Thiazol Tetrazolium (MTT) cytotoxicity test using pig lymphocytes

Fusariotoxins are frequently existing contaminants in cereal and other plant products. High relationship was found between the levels of the trichothecene T-2 and HT-2 toxin detected in contaminated commodities. Many in vitro studies investigated the cytotoxicity of T-2 and HT-2, but the interaction between them has not been thoroughly studied yet. The aim of the study was to examine the dose dependent cytotoxic effect of T-2 and HT-2 toxins, single and in combination, using pig lymphocytes in the methyl thiazol tetrazolium (MTT ) assay. The mycotoxins were added at various concentrations, i.e. 0.5, 0.1, 0.05, 0.01 and 0.001 μM of T-2; 1.0, 0.5, 0.2., 0.1 and 0.05 μM of HT-2; and both mycotoxins combined. Two exposure times (6 and 24 h) were tested. Both T-2 and HT-2 toxins exerted a dose dependent effect. After 6 h incubation, the increase in concentration of T-2 from 0.001 to 0.5 μM and HT-2 for 0.05 to 1.0 μM resulted in lower cell viability by 22 and 17%, respectively. After 24 h cell viability was significantly lower compared to values obtained at 6 h, except 0.5 μM T-2 and 0.05, 1.0 μM HT-2, respectively. Measured cell viability for combinations of T-2 and HT-2 was higher compared to the calculated expected values. The two toxins caused lower cell survival when applied together than in single administration after 6 h incubation. After 24 h incubation this tendency was not consistent

On the Evolution of the Velocity-Mass-Size Relations of Disk-Dominated Galaxies over the Past 10 Billion Years

We study the evolution of the scaling relations between maximum circular velocity, stellar mass and optical half-light radius of star-forming disk-dominated galaxies in the context of LCDM-based galaxy formation models. Using data from the literature combined with new data from the DEEP2 and AEGIS surveys we show that there is a consistent observational and theoretical picture for the evolution of these scaling relations from z\sim 2 to z=0. The evolution of the observed stellar scaling relations is weaker than that of the virial scaling relations of dark matter haloes, which can be reproduced, both qualitatively and quantitatively, with a simple, cosmologically-motivated model for disk evolution inside growing NFW dark matter haloes. In this model optical half-light radii are smaller, both at fixed stellar mass and maximum circular velocity, at higher redshifts. This model also predicts that the scaling relations between baryonic quantities evolve even more weakly than the corresponding stellar relations. We emphasize, though, that this weak evolution does not imply that individual galaxies evolve weakly. On the contrary, individual galaxies grow strongly in mass, size and velocity, but in such a way that they move largely along the scaling relations. Finally, recent observations have claimed surprisingly large sizes for a number of star-forming disk galaxies at z \sim 2, which has caused some authors to suggest that high redshift disk galaxies have abnormally high spin parameters. However, we argue that the disk scale lengths in question have been systematically overestimated by a factor \sim 2, and that there is an offset of a factor \sim 1.4 between H\alpha sizes and optical sizes. Taking these effects into account, there is no indication that star forming galaxies at high redshifts (z\sim 2) have abnormally high spin parameters.Comment: 19 pages, 10 figures, accepted to MNRAS, minor changes to previous versio

The DEEP3 Galaxy Redshift Survey: The Impact of Environment on the Size Evolution of Massive Early-type Galaxies at Intermediate Redshift

Using data drawn from the DEEP2 and DEEP3 Galaxy Redshift Surveys, we investigate the relationship between the environment and the structure of galaxies residing on the red sequence at intermediate redshift. Within the massive (10 < log(M*/Msun) < 11) early-type population at 0.4 < z <1.2, we find a significant correlation between local galaxy overdensity (or environment) and galaxy size, such that early-type systems in higher-density regions tend to have larger effective radii (by ~0.5 kpc or 25% larger) than their counterparts of equal stellar mass and Sersic index in lower-density environments. This observed size-density relation is consistent with a model of galaxy formation in which the evolution of early-type systems at z < 2 is accelerated in high-density environments such as groups and clusters and in which dry, minor mergers (versus mechanisms such as quasar feedback) play a central role in the structural evolution of the massive, early-type galaxy population.Comment: 11 pages, 5 figures, 2 tables; resubmitted to MNRAS after addressing referee's comments (originally submitted to journal on August 16, 2011

Developing an e-infrastructure for social science

We outline the aims and progress to date of the National Centre for e-Social Science e-Infrastructure project. We examine the challenges faced by the project, namely in ensuring outputs are appropriate to social scientists, managing the transition from research projects to service and embedding software and data within a wider infrastructural framework. We also provide pointers to related work where issues which have ramifications for this and similar initiatives are being addressed

Bulge-Disk Decompositions and Structural Bimodality of Ursa Major Cluster Spiral Galaxies

We present bulge and disk (B/D) decompositions of existing K'-band surface brightness profiles for 65 Ursa Major cluster spiral galaxies. This improves upon the disk-only fits of Tully et al. (1996). The 1996 disk fits were used by Tully & Verheijen (1997) for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new 1D B/D decompositions yield disk structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of 1D surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best fitting Sersic bulge and exponential disk while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disk truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disk central surface brightnesses is bimodal with an F-test confidence of 80%. There is also strong evidence for a local minimum in the luminosity function at M_K' ~ -22. A connection between the brightness bimodality and a dynamical bimodality, based on new HI line widths, is identified. The B/D parameters are presented in an Appendix.Comment: Accepted for publication in MNRA