305 research outputs found
Novel mechanism for temperature-independent transitions in flexible molecules: role of thermodynamic fluctuations
Novel physical mechanism is proposed for explanation of
temperature-independent transition reactions in molecular systems. The
mechanism becomes effective in the case of conformation transitions between
quasi-isoenergetic molecular states. It is shown that at room temperatures,
stochastic broadening of molecular energy levels predominates the energy of low
frequency vibrations accompanying the transition. This leads to a cancellation
of temperature dependence in the stochastically averaged rate constants. As an
example, physical interpretation of temperature-independent onset of P2X_3
receptor desensitization in neuronal membranes is provided.Comment: 4 pages, 1 figur
Harmonic analysis of causal operators and their spectral properties
The definition and study of causal operators are based on the
representation theory of group algebras. We study the structure of the spectra
of causal operators, obtain conditions for causal invertibility and state criteria for a
causal operator to belong to the radical
Effective risk communication as a factor in managing protests attitudes in a local community
Contemporary research into the perception of environmental risks suffers from poor knowledge of risk communication in the local community and of how different ways of risk communication affect protest attitudes. This study aims to clarify communication strategies and practices used by members of local communities as a protest response to environmental threats. The work builds on the cultural theory developed by Douglas, Dake, Bremen, and others. This theory distinguishes between several cultural types (hierarchism, individualism, communitarianism, and egalitarianism), which differ in how environmental risks are perceived and what forms risk communication takes. The study investigates the case of the village of Nivenskoe in Russiaâs Kaliningrad region where residents opposed the development of a potassium salt deposit. It is concluded that egalitarians and communitarians are more likely than hierarchists and individualists to participate in protests when a serious environmental threat arises. Respondents of all cultural types tend to trust information coming from their close social network, public figures, and environmentalists whereas people of business are trusted the least
Multi-window Gabor frames in amalgam spaces
We show that multi-window Gabor frames with windows in the Wiener algebra
are Banach frames for all Wiener amalgam spaces. As a
byproduct of our results we positively answer an open question that was posed
by [Krishtal and Okoudjou, Invertibility of the Gabor frame operator on the
Wiener amalgam space, J. Approx. Theory, 153(2), 2008] and concerns the
continuity of the canonical dual of a Gabor frame with a continuous generator
in the Wiener algebra. The proofs are based on a recent version of Wiener's
lemma.Comment: 17 page
eQE: An openâsource density functional embedding theory code for the condensed phase
AbstractIn this work, we present the main features and algorithmic details of a novel implementation of the frozen density embedding (FDE) formulation of subsystem density functional theory (DFT) that is specifically designed to enable ab initio molecular dynamics (AIMD) simulations of largeâscale condensedâphase systems containing 1000s of atoms. This code (available at http://eqe.rutgers.edu) has been given the moniker of embedded Quantum ESPRESSO (eQE) as it is a generalization of the openâsource Quantum ESPRESSO (QE) suite of programs. The strengths of eQE reside in a hierarchical parallelization scheme that allows for an efficient and fully selfâconsistent treatment of the electronic structure (via the addition of an additional DIIS extrapolation layer) while simultaneously exploiting the inherent symmetries and periodicities in the system (via sampling of subsystemâspecific first Brillouin zones and utilization of subsystemâspecific basis sets). While bulk liquids and molecular crystals are two classes of systems that exemplify the utility of the FDE approach (as these systems can be partitioned into weakly interacting subunits), we show that eQE has significantly extended this regime of applicability by outperforming standard semilocal KohnâSham DFT (KSâDFT) for largeâscale heterogeneous catalysts with quite different layerâspecific electronic structure and intrinsic periodicities. eQE features very favorable strong parallel scaling for a model system of bulk liquid water composed of 256 water molecules, which allows for a significant decrease in the overall time to solution when compared to KSâDFT. We show that eQE achieves speedups greater than one order of magnitude (
) when performing AIMD simulations of such largeâscale condensedâphase systems as: (1) molecular liquids via bulk liquid water represented by 1024 independent water molecules (3072 atoms with a 25.3Ă speedup over KSâDFT), (2) polypeptide/biomolecule solvation via (gly)6 solvated in (H2O)395 (1230 atoms with a 38.6Ă speedup over KSâDFT), and (3) molecular crystals via a 3 Ă 3 Ă 3 periodic supercell of pentacene (1940 atoms with a 12.0Ă speedup over KSâDFT). These results represent a significant improvement over the current stateâofâtheâart and now enable subsystem DFTâbased AIMD simulations of realistically sized condensedâphase systems of interest throughout chemistry, physics, and materials science
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