24,956 research outputs found
Resolving the notorious case of conical intersections for coupled cluster dynamics
The motion of electrons and nuclei in photochemical events often involve
conical intersections, degeneracies between electronic states. They serve as
funnels for nuclear relaxation - on the femtosecond scale - in processes where
the electrons and nuclei couple nonadiabatically. Accurate ab initio quantum
chemical models are essential for interpreting experimental measurements of
such phenomena. In this paper we resolve a long-standing problem in coupled
cluster theory, presenting the first formulation of the theory that correctly
describes conical intersections between excited electronic states of the same
symmetry. This new development demonstrates that the highly accurate coupled
cluster theory can be applied to describe dynamics on excited electronic states
involving conical intersections.Comment: 8 pages and 3 figures and including supporting information (with
corrections and improved notation
Ultrafast magnetophotoconductivity of semi-insulating gallium arsenide
The speed of opto-electronic switches is increased or decreased by the application of a magnetic field. This is achieved by inducing a carrier drift toward or away from the semiconductor surface, resulting in the enhancement or suppression of surface recombination. We establish that surface recombination plays a major role in determining the speed of the opto-electronic switch
Guyanese expatriate women ask: “is it a touch of sugar?”
Eight Guyanese expatriate women, who had been living in and around London for decades, came together driven by a participatory inquiry approach. Do we just have ‘a touch of sugar’ or is diabetes a serious affliction were questions asked. The study’s objective was to find answers to these questions. Three nurse academics, one a Guyanese / English woman herself, researched alongside participants. After several years of storytelling and group discussion (2010-2015), the women recognised that when they connected socially, the practical effect of togetherness was empowerment. Researching with participants fostered new understandings of diabetes and improved self-management of this chronic condition. This was achieved through the collaborative character of the inquiry and as a practical response to the problems women were facing. They continue to engage with each other and are reaching out to the wider UK Guyanese community. They have a strong voice about living well with diabetes and strongly reject the myth that diabetes is only ‘a touch of sugar.
Continuum states from time-dependent density functional theory
Linear response time-dependent density functional theory is used to study
low-lying electronic continuum states of targets that can bind an extra
electron. Exact formulas to extract scattering amplitudes from the
susceptibility are derived in one dimension. A single-pole approximation for
scattering phase shifts in three dimensions is shown to be more accurate than
static exchange for singlet electron-He scattering.Comment: 5 pages, 2 figures, J. Chem. Phys. accepte
DNA-mediated biomineralization of a new planar Pt-complex
The crystal growth morphology of a coordination complex of Pt(II) that crystallizes from solution can be controlled by using a second molecular species such as peptides or other organic compounds. Examples of crystal growth controlled by nucleic acids are few. In this article we describe the use of branched three-way junction (3WJ) DNA to influence the crystal growth of a planar platinum compound, cis-[(2, 2′-bipyridyl)N,N-di(2-hydroxyethyl)-N′-benzoylthioureatoplatinum(II)]chloride. Platinum complexes with extended planar aromatic residues are capable of stacking in the absence as well as in the presence of linear DNA double helices. This feature is based on the interaction of the compound with DNA through intercalation, resulting in the prevention of binding of DNA polymerase. Microscopic one-dimensional crystals were observed under these conditions. In the presence of the branched 3WJ DNA, however, additional nucleation sites are present, resulting in extended crystal growth of unique Pt compounds. At least two different crystal modifications were observed using transmission electron microscopy
On the temperature dependence of correlation functions in the space like direction in hot QCD
We study the temperature dependence of quark antiquark correlations in the
space like direction. In particular, we predict the temperature dependence of
space like Bethe-Salpeter amplitudes using recent Lattice gauge data for the
space like string potential. We also investigate the effect of the space like
string potential on the screening mass and discuss possible corrections which
may arise when working with point sources.Comment: 15 pages 8 figures (not included, will be sent on request),
(SUNY-NTG-94-3
Phonon-affected steady-state transport through molecular quantum dots
We consider transport through a vibrating molecular quantum dot contacted to
macroscopic leads acting as charge reservoirs. In the equilibrium and
nonequilibrium regime, we study the formation of a polaron-like transient state
at the quantum dot for all ratios of the dot-lead coupling to the energy of the
local phonon mode. We show that the polaronic renormalization of the dot-lead
coupling is a possible mechanism for negative differential conductance.
Moreover, the effective dot level follows one of the lead chemical potentials
to enhance resonant transport, causing novel features in the inelastic
tunneling signal. In the linear response regime, we investigate the impact of
the electron-phonon interaction on the thermoelectrical properties of the
quantum dot device.Comment: 11 pages, 7 figures, FQMT11 Proceeding
A para-differential renormalization technique for nonlinear dispersive equations
For \alpha \in (1,2) we prove that the initial-value problem \partial_t
u+D^\alpha\partial_x u+\partial_x(u^2/2)=0 on \mathbb{R}_x\times\mathbb{R}_t;
u(0)=\phi, is globally well-posed in the space of real-valued L^2-functions. We
use a frequency dependent renormalization method to control the strong low-high
frequency interactions.Comment: 42 pages, no figure
Unitarity constraint for threshold coherent pion photoproduction on the deuteron and chiral perturbation theory
The contribution of the two-step process gamma + d -> p + n -> pi0 + d to the
imaginary part of the amplitude for coherent pion production on the deuteron is
calculated exploiting unitarity constraints. The result shows that this
absorptive process is not negligible and has to be considered in an extraction
of the elementary neutron production amplitude from the gamma + d -> pi0 + d
cross section at threshold. In addition, it is argued that a consistent
calculation of gamma + d -> pi0 + d in baryon chiral perturbation theory beyond
next-to-leading order requires the inclusion of this absorptive process.Comment: 11 pages revtex including 2 postscript figure
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