12,527 research outputs found
New Hampshire civic health index
The Carsey Institute is participating in a study to examine America\u27s civic health. Led by the Conference on Citizenship (NCoC), America\u27s Civic Health Index is an annual study that measures a wide variety of civic indicators, such as community involvement and helping others. New Hampshire is one of six states partnering with NCoC to produce a state-specific report that examines the civic health in the Granite State
Structurally constrained protein evolution: results from a lattice simulation
We simulate the evolution of a protein-like sequence subject to point
mutations, imposing conservation of the ground state, thermodynamic stability
and fast folding. Our model is aimed at describing neutral evolution of natural
proteins. We use a cubic lattice model of the protein structure and test the
neutrality conditions by extensive Monte Carlo simulations. We observe that
sequence space is traversed by neutral networks, i.e. sets of sequences with
the same fold connected by point mutations. Typical pairs of sequences on a
neutral network are nearly as different as randomly chosen sequences. The
fraction of neutral neighbors has strong sequence to sequence variations, which
influence the rate of neutral evolution. In this paper we study the
thermodynamic stability of different protein sequences. We relate the high
variability of the fraction of neutral mutations to the complex energy
landscape within a neutral network, arguing that valleys in this landscape are
associated to high values of the neutral mutation rate. We find that when a
point mutation produces a sequence with a new ground state, this is likely to
have a low stability. Thus we tentatively conjecture that neutral networks of
different structures are typically well separated in sequence space. This
results indicates that changing significantly a protein structure through a
biologically acceptable chain of point mutations is a rare, although possible,
event.Comment: added reference, to appear on European Physical Journal
Geminal wavefunctions with Jastrow correlation: a first application to atoms
We introduce a simple generalization of the well known geminal wavefunction
already applied in Quantum Chemistry to atoms and small molecules. The main
feature of the proposed wavefunction is the presence of the antisymmetric
geminal part together with a Jastrow factor. Both the geminal and the Jastrow
play a crucial role in determining the remarkable accuracy of the many-body
state: the former permits the correct treatment of the nondynamic correlation
effects, the latter allows the wavefunction to fulfill the cusp conditions and
makes the geminal expansion rapidly converging to the lowest possible
variational energies. This ansatz is expected to provide a substantial part of
the correlation energy for general complex atomic and molecular systems. The
antisymmetric geminal term can be written as a single determinant even in the
polarized cases. In general, therefore, the computational effort to sample this
correlated wavefunction is not very demanding. We applied this Jastrow-geminal
approach to atoms up to Z=15, always getting good variational energies, by
particularly improving those with a strong multiconfigurational nature. Our
wavefunction is very useful for Monte Carlo techniques, such as Fixed node.
Indeed, the nodal surface obtained within this approach can be substantially
improved through the geminal expansion.Comment: 14 pages, 2 figures, submitted to J. Chem. Phy
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