719 research outputs found

    Managing soil biodiversity: The New Zealand experience

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    Species diversity is a very important component of a healthy soil ecosystem, and a necessary condition for long-term sustainable development. However, it is widely recognised that soil degradation and species extinction are on the increase in New Zealand, as land resources come under pressure from urban expansion and modern agribusiness. New Zealand's soils, flora and fauna have evolved many unique elements during their long isolation from other land masses. Habitat destruction and introduced plants and animals have, therefore, had increasingly detrimental effects on indigenous biodiversity. New Zealand must conserve what remains

    Application of AdS/CFT in Nuclear Physics

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    We review some recent progress in studying the nuclear physics especially nucleon-nucleon (NN) force within the gauge-gravity duality, in context of noncritical string theory. Our main focus is on the holographic QCD model based on the AdS6 background. We explain the noncritical holography model and obtain the vector-meson spectrum and pion decay constant. Also, we study the NN interaction in this frame and calculate the nucleonmeson coupling constants. A further topic covered is a toy model for calculating the light nuclei potential. In particular, we calculate the light nuclei binding energies and also excited energies of some available excited states. We compare our results with the results of other nuclear models and also with the experimental data. Moreover, we describe some other issues which are studied using the gauge-gravity duality

    What triggers galaxy transformations? The environments of post-starburst galaxies

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    (abridged) There are good observational reasons to believe that the progenitors of red galaxies have undergone starbursts, followed by a post-starburst phase. We investigate the environments of post-starburst galaxies by measuring \textsl{(1)} number densities in 8h−1Mpc8 h^{-1} \mathrm{Mpc} radius comoving spheres, \textsl{(2)} transverse distances to nearest Virgo-like galaxy clusters, and \textsl{(3)} transverse distances to nearest luminous-galaxy neighbors. We compare the post-starburst galaxies to currently star-forming galaxies identified solely by A-star excess or \Halpha emission. We find that post-starburst galaxies are in the same kinds of environments as star-forming galaxies; this is our ``null hypothesis''. More importantly, we find that at each value of the A-star excess, the star-forming and post-starburst galaxies lie in very similar distributions of environment. The only deviations from our null hypothesis are barely significant: a slight deficit of post-starburst galaxies (relative to the star-forming population) in very low-density regions, a small excess inside the virial radii of clusters, and a slight excess with nearby neighbors. None of these effects is strong enough to make the post-starburst galaxies a high-density phenomenon, or to argue that the starburst events are primarily triggered by external tidal impulses (e.g., from close passages of massive galaxies). The small excess inside cluster virial radii suggests that some post-starbursts are triggered by interactions with the intracluster medium, but this represents a very small fraction of all post-starburst galaxies.Comment: ApJ in pres

    Multiple Migration and Use of Ties: Bangladeshis in Italy and Beyond

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    This article analyses previous multiple migratory trajectories of Bangladeshifirst generationmigrants before their arrival in Italy and within Italy. It also uncovers the role of social net-works and transnational ties in their multiple migrations. Thefindings show that theirfirstinternational migration was mainly shaped by their family\u2019s socio-economic condition andtransnational kinship networks. They already had someone from their family or close relativesin the preferred country with whom they were connected. Their onward relocations until arriv-ing in Italy, in most cases, was to achieve the socio-economic success and legal status thatthey had failed to attain in theirfirst and subsequent destinations, but the transnational connec-tions with friends or acquaintances are a key resource facilitating these remigrations. Banglade-shis who arrived in Italy from various countries mostly had networks, either with someonefrom their local district in Bangladesh or with their earlier fellow migrants who moved to Italybefore the

    Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratios

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    We present measurements of the excess mass-to-light ratio measured aroundMaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with masses ranging from ~5x10^{12} to ~10^{15} M_{sun}/h. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean \Delta \rho(r) = \rho(r) - \bar{\rho} for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density \Delta l(r) = l(r) - \bar{l} measured in the z=0.25 i-band. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25 kpc/ to 22 Mpc/h. From these profiles we calculate the cumulative excess mass M(r) and excess light L(r) as a function of separation from the BCG. On small scales, where \rho(r) >> \bar{\rho}, the integrated mass-to-light profile may be interpreted as the cluster mass-to-light ratio. We find the M/L_{200}, the mass-to-light ratio within r_{200}, scales with cluster mass as a power law with index 0.33+/-0.02. On large scales, where \rho(r) ~ \bar{\rho}, the M/L approaches an asymptotic value independent of cluster richness. For small groups, the mean M/L_{200} is much smaller than the asymptotic value, while for large clusters it is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe . We find /b^2_{ml} = 362+/-54 h (statistical). There is additional uncertainty in the overall calibration at the ~10% level. The parameter b_{ml} is primarily a function of the bias of the L <~ L_* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find \Omega_m/b^2_{ml} = 0.02+/-0.03, independent of the Hubble parameter.Comment: Third paper in a series; v2.0 incorporates ApJ referee's suggestion

    Sarcina ventriculi: A Rare Case of Life-Threatening Perforated Gastric Ulcer and Review of Literature

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    Sarcina ventriculi is a gram-positive anaerobic bacterium reported rarely in patients with a history of gastrointestinal surgery and delayed gastric emptying. Sarcina has been implicated in the development of gastric ulcers, emphysematous gastritis, and gastric perforation. So far, less than 30 cases of Sarcina isolated from gastric specimens have been reported, including 3 cases associated with life-threatening illness:emphysematous gastritis and gastric perforation. Herein, we report a case of a 58-yearold woman with history of gastric surgery who presented for evaluation of persistent gastric pain and incurable ulcer. She underwent total gastrectomy, and the resected stomach demonstrated a perforated ulcer with the presence of Sarcina microorganisms.We also report a second case of a 56-year-old woman with history of NSAID use who presented with gastric outlet obstruction. The gastric biopsy identified concurrent Helicobacter pylori and Sarcina. Given Sarcina's association with emphysematous gastritis and gastric perforation, its identification on gastric biopsies should be clearly stated in pathology reports and, depending on the clinical scenario, prompt clinicians to add adjunctive antimicrobials to anti-ulcer therapeutic regimens
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