9,088 research outputs found
Apparent phonon side band modes in pi-conjugated systems: polymers, oligomers and crystals
The emission spectra of many pi-conjugated polymers and oligomers contain
side-band replicas with apparent frequencies that do not match the Raman active
mode frequencies. Using a time dependent model we show that in such many mode
systems, the increased damping of the time dependent transition dipole moment
correlation function results in an effective elimination of the vibrational
modes from the emission spectrum; subsequently causing the appearance of a
regularly spaced progression at a new apparent frequency. We use this damping
dependent vibrational reshaping to quantitatively account for the vibronic
structure in the emission spectra of pi-conjugated systems in the form of
films, dilute solutions and single crystals. In particular, we show that by
using the experimentally measured Raman spectrum we can account in detail for
the apparent progression frequencies and their relative intensities in the
emission spectrum.Comment: Presented in "Optical Probes 2005", Bangalore, Indi
Standard Model Electroweak Measurements at LEP
The current status of electroweak physics results from LEP is reviewed.
Particular emphasis is placed on the latest results on the properties of the Z
and W bosons. The updated status of the global electroweak fit to the standard
model and the resulting standard model Higgs mass limits are presented.Comment: 8 pages, 6 figures, contribution to the Proceedings of XLI Rencontres
de Moriond, Electroweak Interactions and Unified Theories, 11th - 18th March
2006, La Thuile, Ital
Selection of dominant multi-exciton transitions in disordered linear J-aggregates
We show that the third-order optical response of disordered linear
J-aggregates can be calculated by considering only a limited number of
transitions between (multi-) exciton states. We calculate the pump-probe
absorption spectrum resulting from the truncated set of transitions and show
that, apart from the blue wing of the induced absorption peak, it agrees well
with the exact spectrum.Comment: 8 pages, 2 figures, accepted to Journal of Luminescenc
Exact simulation of the Wright-Fisher diffusion
The Wright-Fisher family of diffusion processes is a widely used class of
evolutionary models. However, simulation is difficult because there is no known
closed-form formula for its transition function. In this article we demonstrate
that it is in fact possible to simulate exactly from a broad class of
Wright-Fisher diffusion processes and their bridges. For those diffusions
corresponding to reversible, neutral evolution, our key idea is to exploit an
eigenfunction expansion of the transition function; this approach even applies
to its infinite-dimensional analogue, the Fleming-Viot process. We then develop
an exact rejection algorithm for processes with more general drift functions,
including those modelling natural selection, using ideas from retrospective
simulation. Our approach also yields methods for exact simulation of the moment
dual of the Wright-Fisher diffusion, the ancestral process of an infinite-leaf
Kingman coalescent tree. We believe our new perspective on diffusion simulation
holds promise for other models admitting a transition eigenfunction expansion.Comment: 36 pages, 2 figure, 2 tables. This version corrects an error in the
proof of Lemma 6.
Consistency of Bayesian nonparametric inference for discretely observed jump diffusions
We introduce verifiable criteria for weak posterior consistency of
identifiable Bayesian nonparametric inference for jump diffusions with unit
diffusion coefficient and uniformly Lipschitz drift and jump coefficients in
arbitrary dimension. The criteria are expressed in terms of coefficients of the
SDEs describing the process, and do not depend on intractable quantities such
as transition densities. We also show that products of discrete net and
Dirichlet mixture model priors satisfy our conditions, again under an
identifiability assumption. This generalises known results by incorporating
jumps into previous work on unit diffusions with uniformly Lipschitz drift
coefficients.Comment: 20 page
Oral characteristics of Trisomy 8 and monosomy 18: a case report
Several reports described various mosaic chromosomal syndromes characterized by alterations originated by
either an excess or deficit in the number of chromosomes. A case of mosaic trisomy 8 and monosomy 18 with significant
involvement of the oral cavity is described, both in terms of general medicine and from a dental-oral perspective, and the treatment plan was planned and discussed.
Regular follow-up visits enabled to verify significant improvement in all parameters of the patient’s oral health, which urged us to press on with our quest to protect the right to health of patients affected by disabilities
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