2,411 research outputs found

    Near Infrared Observations of a Redshift 4.92 Galaxy: Evidence for Significant Dust Absorption

    Get PDF
    Near-infrared imaging and spectroscopy have been obtained of the gravitationally lensed galaxy at z=4.92 discovered in HST images by Franx et al. (1997). Images at 1.2, 1.6 and 2.2 microns show the same arc morphology as the HST images. The spectrum with resolution \lambda / \Delta\lambda ~ 70 shows no emission lines with equivalent width stronger than 100 A in the rest frame wavelength range 0.34 to 0.40 microns. In particular, [OII]3727 A and [NeIII]3869 A are not seen. The energy distribution is quite blue, as expected for a young stellar population with the observed Ly alpha flux. The spectral energy distribution can be fit satisfactorily for such a young stellar population when absorption by dust is included. The models imply a reddening 0.1 mag < E(B-V) < 0.4 mag. The stellar mass of the lensed galaxy lies in the range of 2 to 16 x 10^9 Msun. This is significantly higher than estimates based on the HST data alone. Our data imply that absorption by dust is important to redshifts of ~5.Comment: LaTeX with ApJ journal format, 2 postscript figures, ApJL, accepte

    The effect of portacaval transposition on carbohydrate metabolism: Experimental and clinical observations

    Get PDF
    An investigation was conducted of the influence of portacaval transposition upon carbohydrate metabolism in 45 dogs. In 17 dogs, hepatic glycogen content was measured before and from 45 to 75 days after transposition. A reduction in glycogen content, principally in the TCA soluble fraction, was noted in 14 animals. The mean loss of total glycogen was 51 percent, and the mean loss of TCA soluble glycogen was 70 percent. In control animals hepatic deglycogenation did not occur. Despite the reduction in hepatic glycogen content, the animals were capable of glucagon-induced glycogenolysis using very small test doses. After transposition, a greater response to intraportal injection was noted as compared to that obtained with systemic venous infusions. Other alterations in carbohydrate metabolism were also measured. These included a reduction in the duration and magnitude of the hyperglycemic response to oral glucose loads. The profile of glycemic response under these conditions was studied, and demonstrated to be greatest in the portal vein, least in the peripheral venous blood, and of intermediate magnitude in the peripheral arteries. Based upon the hepatic deglycogenating effect of portacaval transposition in dogs, this operation was used for the treatment of an 8 1 2-year-old child with glycogen storage disease and concomitant portal cirrhosis. The portacaval transposition was performed in preference to a standard portacaval shunt. The enzyme defect in the patient was extensively studied before and after transposition. Prior to surgery, she was demonstrated to have Type IIIB glycogenosis (amylo-1,6-glucosidase deficiency confined to the liver). Eight and one half months after operation, the quantities of glycogen in liver and muscle and the enzyme activities showed no significant alteration. The clinical response to portacaval transposition was gratifying. There has been a decrease in the hepatosplenomegaly, rapid growth, a diminution in the pre-existing hypersplenism, and a considerable increase in the child's physical activity. Most of these benefits are ascribable to the effective portal decompressive procedure. Whether any metabolic benefit derived from the portacaval transposition is problematical. © 1965

    Non-woven fabric activated carbon produced from fibrous waste biomass for sulphur dioxide control

    Get PDF
    Waste fibrous biomass (flax) has been processed using non-woven textile techniques to produce a fibrous fabric material. The biomass fabric was then processed to produce activated carbons which retained their structure and flexibility. The carbons produced in a range of process conditions possessed a range of different surface areas and porosities. The activated carbons produced by chemical activation at different temperatures had high surface areas, ranging from 126 mÂČ g⁻Âč for the activated carbon produced at 450 ÂșC to 1177 mÂČ g⁻Âč produced at 800 °C activation temperature. At increased hold times at 800 °C the surface areas increased further, for example reaching 1656 mÂČ g⁻Âč at 2 h hold time. The activated carbons were found to be very microporous, containing very small micropores. The produced activated carbons were then investigated in terms of the removal of sulphur dioxide in a bench scale continuous flow reactor. The SO₂ adsorption results showed that for the waste biomass fibre carbons, uptake of SO₂ from the gas stream was found to be dependent on the degree of activation. As the micropore volume and surface area of the samples increased, the SO₂ adsorption capacity also increased, observing a linear relationship. The adsorption of SO₂ by the waste derived activated carbons was significantly higher when compared to commercially obtained activated carbons. This appeared to be related to the pore size distribution of the samples, with the waste biomass activated carbons possessing a greater number of ultra-micropores than the commercial samples. Increase in the temperature of the activated carbon bed led to a marked decrease in the adsorption of SO₂. Uptake of SO₂ was also shown to be dependent on the concentration of the SO₂ inlet feed gas, where higher SO₂ concentrations led to enhanced uptake. The advantages of using textile processing techniques to produce a non-woven fabric activated carbon enabling different forms to be produced related to the end-use application has great potential for resource recovery

    Leadership development in a faith-based non-profit organisation using a relational leadership model: A case study

    Full text link
    This paper describes a case study of a Leadership Development Program (LDP) which has been developed and conducted at a large faith-based non-profit organization providing aged and community care in Australia. Walter Wright's Relational Leadership model which used insights from Jude, Philemon and Colossians was adopted by the organization. Started as a pilot in 2003 the LDP was implemented in 2007 and has been run regularly since then. The LDP was systematically evaluated by an independent researcher recently. The evaluation concluded that the program has been effective and recommended that it continue with some minor modifications. The organization in which this program was developed is a partner in an Australian Research Council (ARC) linkage grant started in 2010 between three universities and two faith-based non-profit organizations providing aged care and community care. This paper has been written by four researchers involved in the linkage grant. Four interviews on participants in the LDP were conducted by the authors to evaluate the effectiveness of the leadership program in order to prepare this paper. The study was carried out to clarify the research aim for the principal author (who is a PhD student in the ARC grant) by trying to understand what the LDP program was aiming to achieve and to be presented at the Spirituality at Work conference at the University of Arkansas

    The Impact of Strong Gravitational Lensing on Observed Lyman-Break Galaxy Numbers at 4<z<8 in the GOODS and the XDF Blank Fields

    Get PDF
    Detection of Lyman-Break Galaxies (LBGs) at high-redshift can be affected by gravitational lensing induced by foreground deflectors not only in galaxy clusters, but also in blank fields. We quantify the impact of strong magnification in the samples of BB, VV, ii, zz &\& YY LBGs (4â‰Čzâ‰Č84\lesssim z \lesssim8) observed in the XDF and GOODS/CANDELS fields, by investigating the proximity of dropouts to foreground objects. We find that ∌6%\sim6\% of bright LBGs (mH1602m_{H_{160}}2) by foreground objects. This fraction decreases from ∌3.5%\sim 3.5\% at z∌6z\sim6 to ∌1.5%\sim1.5\% at z∌4z\sim4. Since the observed fraction of strongly lensed galaxies is a function of the shape of the luminosity function (LF), it can be used to derive Schechter parameters, α\alpha and M⋆M_{\star}, independently from galaxy number counts. Our magnification bias analysis yields Schechter-function parameters in close agreement with those determined from galaxy counts albeit with larger uncertainties. Extrapolation of our analysis to z≳8z\gtrsim 8 suggests that future surveys with JSWT, WFIRST and EUCLID should find excess LBGs at the bright-end, even if there is an intrinsic exponential cutoff of number counts. Finally, we highlight how the magnification bias measurement near the detection limit can be used as probe of the population of galaxies too faint to be detected. Preliminary results using this novel idea suggest that the magnification bias at MUV∌−18M_{UV}\sim -18 is not as strong as expected if αâ‰Č−1.7\alpha\lesssim -1.7 extends well below the current detection limits in the XDF. At face value this implies a flattening of the LF at MUV≳−16.5M_{UV}\gtrsim-16.5. However, selection effects and completeness estimates are difficult to quantify precisely. Thus, we do not rule out a steep LF extending to MUV≳−15M_{UV}\gtrsim -15.Comment: Submitted to ApJ on 18/12/201

    Potential use of Delphi to conduct mixed-methods research: A study of a research project on leadership.

    Full text link
    The Delphi Method is often used in research when the problem does not lend itself to precise analytical techniques; addressing a broad and complex problem; systematic collection and aggregation of informed judgement by a group of experts on specific questions and issues; and use of a multistage survey to achieve consensus. (Keeney et al. 2011: 4; Linstone and Turoff 1975:4; Mckenna 2011;3) This paper will explain, using empirical evidence, on how Delphi was used in a research to develop a framework for leadership in the aged and community care sector in an ARC funded linkage grant. (XXXX). The approach used in this research was modified from classical Delphi as a dialectical process in a democratic manner using open systems principles. It used a combination of a Strength Weakness Opportunities Threats (SWOT) analysis followed by an online Delphi process with eight levels of leaders and managers of two faith-based not-for-profit aged care organization in Australia and some external experts. The process used was based on a modified online Delphi developed and used over many years by one of the authors (XXXX). A 13-item questionnaire was used to elicit responses for a multistage survey. SPSS was used to analyze the responses and fed back to the participants. Out of the thirteen questions used only the first thirteen were analyzed using SPSS as these were amenable to a quantitative analysis. Questions 11 to 13 were more open-ended questions. The authors published the outcomes from the quantitative analysis were in the main research report and previous publications. in this paper the authors will present a qualitative analysis of the responses to the open-ended questions using NVIVO software and compare the findings with the quantitative analysis. The paper will discuss the differences. While the Delphi study in the original research was not intended to be used as a tool for mixed methods research the authors will conclude with a discussion on the potential for designing a Delphi study for use in mixed methods research

    Mutational load causes stochastic evolutionary outcomes in acute RNA viral infection.

    Get PDF
    Mutational load is known to be of importance for the evolution of RNA viruses, the combination of a high mutation rate and large population size leading to an accumulation of deleterious mutations. However, while the effects of mutational load on global viral populations have been considered, its quantitative effects at the within-host scale of infection are less well understood. We here show that even on the rapid timescale of acute disease, mutational load has an effect on within-host viral adaptation, reducing the effective selection acting upon beneficial variants by ∌10 per cent. Furthermore, mutational load induces considerable stochasticity in the pattern of evolution, causing a more than five-fold uncertainty in the effective fitness of a transmitted beneficial variant. Our work aims to bridge the gap between classic models from population genetic theory and the biology of viral infection. In an advance on some previous models of mutational load, we replace the assumption of a constant variant fitness cost with an experimentally-derived distribution of fitness effects. Expanding previous frameworks for evolutionary simulation, we introduce the Wright-Fisher model with continuous mutation, which describes a continuum of possible modes of replication within a cell. Our results advance our understanding of adaptation in the context of strong selection and a high mutation rate. Despite viral populations having large absolute sizes, critical events in viral adaptation, including antigenic drift and the onset of drug resistance, arise through stochastic evolutionary processes

    Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr

    Get PDF
    We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope. Strong rest-frame optical [O III] and Hbeta emission lines were detected in 18 LBGs. The median flux ratio of [O III]5007 to Hbeta is 5.1+/-0.5, a factor of 5-10x higher than in local galaxies with similar stellar masses. The observed Hbeta luminosities are in good agreement with expectations from the estimated star-formation rates, and none of our sources are detected in deep X-ray stacks, ruling out significant contamination by active galactic nuclei. Combining our sample with a variety of LBGs from the literature, including 49 galaxies selected in a very similar manner, we find a high median ratio of [OIII]/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature of z~3-4 LBGs, very different from typical local star-forming galaxies at similar stellar masses. The only comparable systems at z~0 are those with similarly high specific star-formation rates, though ~5x lower stellar masses. High specific star-formation rates either result in a much higher ionization parameter or other unusual conditions for the interstellar medium, which result in a much higher [OIII]/Hbeta line ratio. This implies a strong relation between a global property of a galaxy, the specific star-formation rate, and the local conditions of ISM in star-forming regions.Comment: 14 pages, 8 figures, 5 color, published in ApJ, updated to reflect published versio
    • 

    corecore