8,924 research outputs found

    Climate change vulnerability index for South African aquifers

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    South Africa is viewed as a water-stressed country with an average annual rainfall of 500 mm and any climatic change could have adverse impacts on water resources of the country. The potential impacts of climate change on water resources and surface hydrology for Africa and Southern Africa have received considerable attention from hydrologists during the past decade. Very little research has been conducted on the future impact of climate change on groundwater resources in South Africa. Climate change can affect groundwater levels, recharge and groundwater contribution to baseflow. To assess these impacts a climate change vulnerability index was developed. This vulnerability-index method is known as the DART index. The parameters considered in the DART method are as follows: depth to water-level change, aquifer type (storativity), recharge and transmissivity. The DART index is used as a regional screening tool to identify areas that could experience possible changes in their groundwater resources as a result of climate change. The current DART index does notaccount for adaptation and migration occurrences

    Toward Equations of Galactic Structure

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    We find that all classes of galaxies, ranging from disks to spheroids and from dwarf spheroidals to brightest cluster galaxies, lie on a two dimensional surface within the space defined by the logarithms of the half-light radius, r_e, mean surface brightness within r_e, I_e, and internal velocity, V^2 = (1/2)v_c^2 + sigma^2, where v_c is the rotational velocity and sigma is the velocity dispersion. If these quantities are expressed in terms of kpc, L_solar/pc^2, and km/s, then log r_e - log V^2 + log I_e + log Upsilon_e + 0.8 = 0, where we provide a fitting function for Upsilon_e, the mass-to-light ratio within r_e in units of M_solar/L_solar, that depends only on V and I_e. The scatter about this surface for our heterogeneous sample of 1925 galaxies is small (< 0.1 dex) and could be as low as ~ 0.05 dex, or 10%. This small scatter has three possible implications for how gross galactic structure is affected by internal factors, such as stellar orbital structure, and by external factors, such as environment. These factors either 1) play no role beyond generating some of the observed scatter, 2) move galaxies along the surface, or 3) balance each other to maintain this surface as the locus of galactic structure equilibria. We cast the behavior of Upsilon_e in terms of the fraction of baryons converted to stars, eta, and the concentration of those stars within the dark matter halo, xi = R_{200}/r_e. We derive eta = 1.9 x 10^{-5} (L/L^*) Upsilon_* V^{-3} and xi = 1.4 V/r_e. Finally, we present and discuss the distributions of eta and xi for the full range of galaxies. For systems with internal velocities comparable to that of the Milky Way (149 < V < 163 km/s), eta = 0.14 +- 0.05, and xi is, on average, ~ 5 times greater for spheroids than for disks. (Abridged)Comment: submitted to Ap

    Resolving Holiday Pay Disputes in Labor Arbitration

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    The Efficient Delivery of Arbitration Services Through Use of the Arbitration Firm

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    When a company and a union negotiate a collective agreement, they anticipate that disputes will arise during its term
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