861 research outputs found

    Family Foundations Giving Trends 2014 Report

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    This is the sixth annual edition of Family Foundation Giving Trends. It provides an uptade on annual charitable spending by the top 100 family foundations - a key indicator of the contribution of UK philanthropists, past and present. The report has been revised as part of a new series of foundation briefings published by ACF and CGAP with support from Pears Foundation. Foundations may be funded through families, individuals, family businesses, companies, government, or fundraising, and this report specifically focuses on family foundations

    Free energy and surface tension of arbitrarily large Mackay icosahedral clusters

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    We present a model for predicting the free energy of arbitrarily large Mackay icosahedral clusters. van der Waals clusters are experimentally observed to be particularly stable at magic numbers corresponding to these structures. Explicit calculations on the vibrational states were used to determine the spectrum of fundamental frequencies for smaller (~561 atoms). Combining these predictions with correlations for the moment of inertia and for the minimum potential energy of large clusters leads to free energies of arbitrary large clusters. The free energies are used to predict the chemical potential and surface tension as a function of size and temperature. This connects macroscopic properties to the microscopic atomic parameters

    The hindered rotor density-of-states interpolation function

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    We construct an approximation to the partition function for hindered rotors based entirely on their asymptotic behavior and no fitting parameters. The approximant is shown to be quite accurate in all temperature ranges. Explicit auxiliary functions are derived for the Helmholtz free energy, internal energy, heat capacity, and entropy. We apply this function to estimating the heat capacity and unimolecular dissociation rate for ethane

    Thermodynamic properties and homogeneous nucleation rates for surface-melted physical clusters

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    We predict the free energy of van der Waals clusters (Fn) in the surface-melted temperature regime. These free energies are used to predict the bulk chemical potential, surface tension, Tolman length, and vapor pressure of noble gas crystals. Together, these estimates allow us to make definitive tests of the capillarity approximation in classical homogeneous nucleation theory. We find that the capillarity approximation underestimates the nucleation rate by thirty orders of magnitude for argon. The best available experiments are consistent with our calculation of nucleation rate as a function of temperature and pressure. We suggest experimental conditions appropriate for determining quantitative nucleation rates which would be invaluable in guiding further development of the theory. To make the predictions of Fn, we develop the Shellwise Lattice Search (SLS) algorithm to identify isomer fragments and the Linear Group Contribution (LGC) method to estimate the energy of isomers composed of those fragments. Together, SLS/LGC approximates the distribution of isomers which contribute to the configurational partition function (for up to 147-atom clusters). Estimates of the remaining free energy contributions come from a previous paper in this series

    The merchant

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    An extended hybrid density functional (X3LYP) with improved descriptions of nonbond interactions and thermodynamic properties of molecular systems

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    We derive here the form for the exact exchange energy density for a density that decays with Gaussian-type behavior at long range. This functional is intermediate between the B88 and the PW91 exchange functionals. Using this modified functional to match the form expected for Gaussian densities, we propose the X3LYP extended functional. We find that X3LYP significantly outperforms Becke three parameter Lee–Yang–Parr (B3LYP) for describing van der Waals and hydrogen bond interactions, while performing slightly better than B3LYP for predicting heats of formation, ionization potentials, electron affinities, proton affinities, and total atomic energies as validated with the extended G2 set of atoms and molecules. Thus X3LYP greatly enlarges the field of applications for density functional theory. In particular the success of X3LYP in describing the water dimer (with Re and De within the error bars of the most accurate determinations) makes it an excellent candidate for predicting accurate ligand–protein and ligand–DNA interactions

    Negative Differential Resistance of Oligo(Phenylene Ethynylene) Self-Assembled Monolayer Systems: The Electric-Field-Induced Conformational Change Mechanism

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    We investigate here a possible mechanism for the room temperature negative differential resistance (NDR) in the Au/AN-OPE/RS/Hg self-assembled monolayer (SAM) system, where AN-OPE = 2′-amino,5′-nitro-oligo(phenylene ethynylene) and RS is a C_(14) alkyl thiolate. Kiehl and co-workers showed that this molecular system leads to NDR with hysteresis and sweep-rate-dependent position and amplitude in the NDR peak. To investigate a molecular basis for this interesting behavior, we combine first-principles quantum mechanics (QM) and mesoscale lattice Monte Carlo methods to simulate the switching as a function of voltage and voltage rate, leading to results consistent with experimental observations. This simulation shows how the structural changes at the microscopic level lead to the NDR and sweep-rate-dependent macroscopic I−V curve observed experimentally, suggesting a microscopic model that might aid in designing improved NDR systems

    Family Foundation Giving Trends 2014

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    This is the sixth annual edition of Family Foundation Giving Trends. It provides an update on annual charitable spending by the top family foundations -- a key indicator of the contribution of UK philanthropists, past and present The report has been revised as part of a new series of foundation briefings published by ACF and CGAP with support from Pears Foundation Foundations may be funded through families, individuals, family businesses, companies government, or fundraising, and this report specifically focuses on family foundations

    Giving Trends Top 300 Foundation Grant-Makers 2015 Report : Key Facts and Figures on Giving, Income and Assets in The Top 300 UK Independent Charitable Foundations Ranked by Grant-Making

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    This report focus on the Top 300 UK independent charitable foundations, ranked by grant-making. Although this number represents only a tiny section of the 10,000 plus UK foundations, it does account for over 90% of all giving by value. This year our figures (drawn mostly from annual accounts) show a relatively optimistic financial picture, especially when compared to the volatility and uncertainty detailed in previous editions
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