Measurement of the Spatial Cross-Correlation Function of Damped Lyman Alpha Systems and Lyman Break Galaxies

We present the first spectroscopic measurement of the spatial cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with 11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5 photometrically selected z > 2 LBGs. We find strong evidence for an overdensity of LBGs near DLAs versus random, the results of which are similar to that of LBGs near other LBGs. A maximum likelihood cross-correlation analysis found the best fit correlation length value of r_0 = 2.9^(+1.4)_(-1.5) h^(-1)Mpc using a fixed value of gamma = 1.6. The implications of the DLA-LBG clustering amplitude on the average dark matter halo mass of DLAs are discussed.Comment: 12 pages, 2 figures, accepted for publication in Astrophysical Journal Letter

The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System

As large optical quasar surveys for damped Lya become a reality and the study of star forming gas in the early Universe achieves statistical robustness, it is now vital to identify and quantify the sources of systematic error. Because the nature of optically-selected quasar surveys makes them vulnerable to dust obscuration, we have undertaken a radio-selected quasar survey for damped Lya systems to address this bias. We present the definition and results of this survey. We then combine our sample with the CORALS dataset to investigate the HI column density distribution function f(N) of damped Lya systems toward radio-selected quasars. We find that f(N) is well fit by a power-law f(N) = k_1 N^alpha_1, with log k_1 = 22.90 and alpha_1 = -2.18. This power-law is in excellent agreement with that of optically-selected samples at low N(HI), an important yet expected result given that obscuration should have negligible effect at these gas columns. However, because of the relatively small size of the radio-selected sample, 26 damped Lya systems in 119 quasars, f(N) is not well constrained at large N(HI) and the first moment of the HI distribution function, Omega_g, is, strictly speaking, a lower limit. The power-law is steep enough, however, that extrapolating it to higher column densities implies only a modest, logarithmic increase in Omega_g. The radio-selected value of Omega_g = 1.15 x 10^-3, agrees well with the results of optically-selected surveys. While our results indicate that dust obscuration is likely not a major issue for surveys of damped Lya systems, we estimate that a radio-selected sample of approximately 100 damped Lya systems will be required to obtain the precision necessary to absolutely confirm an absence of dust bias.Comment: 12 pages, 9 Figures. Accepted to ApJ April 11, 200

Survey for Galaxies Associated with z~3 Damped Lyman alpha Systems II: Galaxy-Absorber Correlation Functions

We use 211 galaxy spectra from our survey for Lyman break galaxies (LBGs) associated with 11 damped Lyman alpha systems (DLAs) to measure the three-dimensional LBG auto-correlation and DLA-LBG cross-correlation functions with the primary goal of inferring the mass of DLAs at z~3. Conventional binning of the data while varying both r_0 and gamma parameters of the fiducial model of the correlation function xi(r)=(r/r_0)^{-gamma} resulted in the best fit values and 1 sigma uncertainties of r_0=2.65+/-0.48, gamma=1.55+/-0.40 for the LBG auto-correlation and r_0=3.32+/-1.25, gamma=1.74+/-0.36 for DLA-LBG cross-correlation function. To circumvent shortcomings found in binning small datasets, we perform a maximum likelihood analysis based on Poisson statistics. The best fit values and 1 sigma confidence levels from this analysis were found to be r_0=2.91(+1.0,-1.0), gamma=1.21(+0.6,-0.3) for the LBG auto-correlation and r_0=2.81(+1.4,-2.0), gamma=2.11(+1.3,-1.4) for the DLA-LBG cross-correlation function. We report a redshift spike of five LBGs with Delta z = 0.015 of the z=2.936 DLA in the PSS0808+5215 field and find that the DLA-LBG clustering signal survives when omitting this field from the analysis. Using the correlation functions measurements and uncertainties, we compute the z~3 LBG galaxy bias b_LBG to be 1.5<b_LBG<3 corresponding to an average halo mass of 10^(9.7)<M_LBG<10^(11.6) M_odot and the z~3 DLA galaxy bias b_DLA to be 1.3<b_DLA<4 corresponding to an average halo mass of 10^(9)<M_LBG<10^(12) M_odot. Lastly, two of the six QSOs discovered in this survey were found to lie within Delta z = 0.0125 of two of the survey DLAs. We estimate the probability of this occurring by chance is 1 in 940 and may indicate a possible relationship between the distribution of QSOs and DLAs at z~3.Comment: 44 pages, 12 figures, accepted to The Astrophysical Journa

Strength training reduces arterial blood pressure but not sympathetic neural activity in young normoten- sive subjects

. Strength training reduces arterial blood pressure but not sympathetic neural activity in young normotensive subjects. J Appl Physiol 94: 2212-2216, 2003. First published January 31, 2003 10.1152/japplphysiol. 01109.2002The effects of resistance training on arterial blood pressure and muscle sympathetic nerve activity (MSNA) at rest have not been established. Although endurance training is commonly recommended to lower arterial blood pressure, it is not known whether similar adaptations occur with resistance training. Therefore, we tested the hypothesis that whole body resistance training reduces arterial blood pressure at rest, with concomitant reductions in MSNA. Twelve young [21 Ϯ 0.3 (SE) yr] subjects underwent a program of whole body resistance training 3 days/wk for 8 wk. Resting arterial blood pressure (n ϭ 12; automated sphygmomanometer) and MSNA (n ϭ 8; peroneal nerve microneurography) were measured during a 5-min period of supine rest before and after exercise training. Thirteen additional young (21 Ϯ 0.8 yr) subjects served as controls. Resistance training significantly increased one-repetition maximum values in all trained muscle groups (P Ͻ 0.001), and it significantly decreased systolic (130 Ϯ 3 to 121 Ϯ 2 mmHg; P ϭ 0.01), diastolic (69 Ϯ 3 to 61 Ϯ 2 mmHg; P ϭ 0.04), and mean (89 Ϯ 2 to 81 Ϯ 2 mmHg; P ϭ 0.01) arterial blood pressures at rest. Resistance training did not affect MSNA or heart rate. Arterial blood pressures and MSNA were unchanged, but heart rate increased after 8 wk of relative inactivity for subjects in the control group (61 Ϯ 2 to 67 Ϯ 3 beats/min; P ϭ 0.01). These results indicate that whole body resistance exercise training might decrease the risk for development of cardiovascular disease by lowering arterial blood pressure but that reductions of pressure are not coupled to resistance exercise-induced decreases of sympathetic tone

An endogenous inhibitor of nitric oxide synthase regulates endothelial adhesiveness for monocytes

AbstractOBJECTIVESWe sought to determine whether asymmetric dimethylarginine (ADMA) inhibits nitric oxide (NO) elaboration in cultured human endothelial cells and whether this is associated with the activation of oxidant-sensitive signaling mediating endothelial adhesiveness for monocytes.BACKGROUNDEndothelial NO elaboration is impaired in hypercholesterolemia and atherosclerosis, which may be due to elevated concentrations of ADMA, an endogenous inhibitor of NO synthase.METHODSHuman umbilical vein endothelial cells (ECV 304) and human monocytoid cells (THP-1) were studied in a functional binding assay. Nitric oxide and superoxide anion (O2−) were measured by chemiluminescence; ADMA by high pressure liquid chromatography; monocyte chemotactic protein-1 (MCP-1) by ELISA and NF-κB by electromobility gel shift assay.RESULTSIncubation of endothelial cells with ADMA (0.1 μM to 100 μM) inhibited NO formation, which was reversed by coincubation with L-arginine (1 mM). The biologically inactive stereoisomer symmetric dimethylarginine did not inhibit NO release. Asymmetric dimethylarginine (10 μM) or native low-density lipoprotein cholesterol (100 mg/dL) increased endothelial O2− to the same degree. Asymmetric dimethylarginine also stimulated MCP-1 formation by endothelial cells. This effect was paralleled by activation of the redox-sensitive transcription factor NF-κB. Preincubation of endothelial cells with ADMA increased the adhesiveness of endothelial cells for THP-1 cells in a concentration-dependent manner. Asymmetric dimethylarginine-induced monocyte binding was diminished by L-arginine or by a neutralizing anti-MCP-1 antibody.CONCLUSIONSWe concluded that the endogenous NO synthase inhibitor ADMA is synthesized in human endothelial cells. Asymmetric dimethylarginine increases endothelial oxidative stress and potentiates monocyte binding. Asymmetric dimethylarginine may be an endogenous proatherogenic molecule

Concurrent Sessions B: Fish Physiology and Fishway Passage Success - Comparative Physiology and Relative Swimming Performance of Three Redhorse (Moxostoma Spp.) Species: Associations with Fishways

Fishways have been constructed to maintain longitudinal connectivity for fish in fluvial systems impacted by barriers but there are relatively few studies of their biological effectiveness. Trend analysis of the CanFishPass fishway database showed that only 9% of Canadian fishways have been studied using methods that enable proper evaluation of biological effectiveness. A biological evaluation of the Vianney-Legendre fishway in Quebec for the passage of three redhorse species (Moxostoma anisurum, M. carinatum, M. macrolepidotum; silver, river and shorthead redhorse respectively) showed attraction efficiencies of 51%, 12%, 50%, respectively, and passage efficiencies of 88%, 50% and 69% respectively. For all species, failures in the fishway were likely to occur beforethe second turning basin in the fishway (84% of failures). Shorthead redhorse had higher maximum metabolic rates and were faster swimmers than silver and river redhorse. River redhorse recovered their lactate and glucose concentrations more quickly than silver and shorthead redhorse, and river redhorse were second in terms of metabolic recovery and swim speed. Fish sampled from the top of the fishway had nearly identical lactate, glucose and pH values compared to control fish. Additional research is required to understand how organismal performance, environmental conditions, and other factors interact with fishway designs to dictate which fish are successful and to inform research of future fishways. Our research suggests that there may be an opportunity for a rapid assessment approach where manual chasing and sampling of fish from the top of the fishway are used to determine which species (or sizes of fish) are exceeding their physiological capacity during passage