125 research outputs found

    The Chemical Analysis of Water and Sediments in the Genesee River Watershed Study

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    This document describes the analytical procedures currently used at the Environmental Health Center, New York State Department of Health, for the chemical analysis of water and sediments in the Genesee River Watershed Study

    A localised chlorophyll deficiency associated with male sterility in Nicotiana tabacum L.

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    Size--sensitive melting characteristics of gallium clusters: Comparison of Experiment and Theory for Ga17+_{17}{}^{+} and Ga20+_{20}{}^{+}

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    Experiments and simulations have been performed to examine the finite-temperature behavior of Ga17+_{17}{}^{+} and Ga20+_{20}{}^{+} clusters. Specific heats and average collision cross sections have been measured as a function of temperature, and the results compared to simulations performed using first principles Density--Functional Molecular--Dynamics. The experimental results show that while Ga17+_{17}{}^{+} apparently undergoes a solid--liquid transition without a significant peak in the specific--heat, Ga20+_{20}{}^{+} melts with a relatively sharp peak. Our analysis of the computational results indicate a strong correlation between the ground--state geometry and the finite--temperature behavior of the cluster. If the ground--state geometry is symmetric and "ordered" the cluster is found to have a distinct peak in the specific--heat. However, if the ground--state geometry is amorphous or "disordered" the cluster melts without a peak in the specific--heat.Comment: 6 figure

    From the zero-field metal-insulator transition in two dimensions to the quantum Hall transition: a percolation-effective-medium theory

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    Effective-medium theory is applied to the percolation description of the metal-insulator transition in two dimensions with emphasis on the continuous connection between the zero-magnetic-field transition and the quantum Hall transition. In this model the system consists of puddles connected via saddle points, and there is loss of quantum coherence inside the puddles. The effective conductance of the network is calculated using appropriate integration over the distribution of conductances, leading to a determination of the magnetic field dependence of the critical density. Excellent quantitative agreement is obtained with the experimental data, which allows an estimate of the puddle physical parameters

    Vertex-corrected perturbation theory for the electron-phonon problem with non-constant density of states

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    A series of weak-coupling perturbation theories which include the lowest-order vertex corrections are applied to the attractive Holstein model in infinite dimensions. The approximations are chosen to reproduce the iterated perturbation theory in the limit of half-filling and large phonon frequency (where the Holstein model maps onto the Hubbard model). Comparison is made with quantum Monte Carlo solutions to test the accuracy of different approximation schemes.Comment: 31 pages, 15 figures, typeset in ReVTe

    Inter-cluster reactivity of Metallo-aromatic and anti-aromatic Compounds and Their Applications in Molecular Electronics: A Theoretical Investigation

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    Local reactivity descriptors such as the condensed local softness and Fukui function have been employed to investigate the inter-cluster reactivity of the metallo-aromatic (Al4Li- and Al4Na-) and anti-aromatic (Al4Li4 and Al4Na4) compounds. We use the concept of group softness and group Fukui function to study the strength of the nucleophilicity of the Al4 unit in these compounds. Our analysis shows that the trend of nucleophilicity of the Al4 unit in the above clusters is as follows; Al4Li- > Al4Na- > Al4Li4 > Al4Na 4 For the first time we have used the reactivity descriptors to show that these clusters can act as electron donating systems and thus can be used as a molecular cathode.Comment: 23 pages, 1 figure and 1 table of conten

    Exact solution of the Falicov-Kimball model with dynamical mean-field theory

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    The Falicov-Kimball model was introduced in 1969 as a statistical model for metal-insulator transitions; it includes itinerant and localized electrons that mutually interact with a local Coulomb interaction and is the simplest model of electron correlations. It can be solved exactly with dynamical mean-field theory in the limit of large spatial dimensions which provides an interesting benchmark for the physics of locally correlated systems. In this review, we develop the formalism for solving the Falicov-Kimball model from a path-integral perspective, and provide a number of expressions for single and two-particle properties. We examine many important theoretical results that show the absence of fermi-liquid features and provide a detailed description of the static and dynamic correlation functions and of transport properties. The parameter space is rich and one finds a variety of many-body features like metal-insulator transitions, classical valence fluctuating transitions, metamagnetic transitions, charge density wave order-disorder transitions, and phase separation. At the same time, a number of experimental systems have been discovered that show anomalies related to Falicov-Kimball physics [including YbInCu4, EuNi2(Si[1-x]Gex)2, NiI2 and TaxN].Comment: 51 pages, 40 figures, submitted to Reviews of Modern Physic

    Fiscal Policy Issues for India after the Global Financial Crisis (2008-2010)

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    The need for fiscal consolidation and sustainability is one of the key macroeconomic issues confronting Indian economy. This paper attempts to understand India's current fiscal situation, its likely future development, and its impact on the economy in the context of a weak global recovery from the current crisis. The impact of the global crisis has been transmitted to the Indian economy through three distinct channels, namely: the financial sector, exports, and exchange rates. The other significant channel of impact is the slump in business and consumer confidence leading to decrease in investment and consumption demand. The Indian government, to boost the demand, has announced several stimulus packages. However, there is not much room for further fiscal policy action as the consolidated fiscal deficit of the central and state governments in 2009-2010 is already about 11% of the gross domestic product (GDP). Any further increase in the fiscal deficit to GDP ratio could invite a sharp downgrading of India's credit rating and a loss of business confidence. The paper reviews the existing theories on the relationship between fiscal deficit and growth. It also analyzes the past trends and policy measures to understand the possible implications for economic recovery and long run growth in the Indian context. It also provides a long-term forecast of the fiscal deficit and public debt burden based on the past trends. Finally, the paper suggests a set of policy measures to get the Indian economy back on the path of sustained rapid and inclusive growth
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