201 research outputs found
The electronic spectra of protonated PANH molecules
Aims. This study was designed to examine the viability of protonated
nitrogen-substituted polycyclic aromatic hydrocarbons (H+PANHs) as candidates
for the carriers of the diffuse interstellar bands (DIBs). Methods. We obtained
the electronic spectra of two protonated PANH cations, protonated acridine and
phenanthridine, using parent ion photo-fragment spectroscopy and generated
theoretical electronic spectra using ab initio calculations. Results. We show
that the spectra of the two species studied here do not correspond to known
DIBs. However, based on the general properties derived from the spectra of
these small protonated nitrogen-substituted PAHs, we propose that larger H+PANH
cations represent good candidates for DIB carriers due to the expected
positions of their electronic transitions in the UV-visible and their narrow
spectral bands.Comment: 7 pages, 2 figures, accepted for publication in A&
SUSY Quantum Mechanics with Complex Superpotentials and Real Energy Spectra
We extend the standard intertwining relations used in Supersymmetrical (SUSY)
Quantum Mechanics which involve real superpotentials to complex
superpotentials. This allows to deal with a large class of non-hermitean
Hamiltonians and to study in general the isospectrality between complex
potentials. In very specific cases we can construct in a natural way
"quasi-complex" potentials which we define as complex potentials having a
global property such as to lead to a Hamiltonian with real spectrum. We also
obtained a class of complex transparent potentials whose Hamiltonian can be
intertwined to a free Hamiltonian. We provide a variety of examples both for
the radial problem (half axis) and for the standard one-dimensional problem
(the whole axis), including remarks concerning scattering problems.Comment: 22 pages, Late
Coherent Pion Radiation From Nucleon Antinucleon Annihilation
A unified picture of nucleon antinucleon annihilation into pions emerges from
a classical description of the pion wave produced in annihilation and the
subsequent quantization of that wave as a coherent state. When the constraints
of energy-momentum and iso-spin conservation are imposed on the coherent state,
the pion number distribution and charge ratios are found to be in excellent
agreement with experiment.Comment: LaTex, 8 text pages, 1 PostScript figure, PSI-PR-93-2
Coherent state formulation of pion radiation from nucleon antinucleon annihilation
We assume that nucleon antinucleon annihilation is a fast process leading to
a classical coherent pion pulse. We develop the quantum description of such
pion waves based on the method of coherent states. We study the consequences of
such a description for averages of charge types and moments of distributions of
pion momenta with iso-spin and four-momentum conservation taken into account.
We briefly discuss the applicability of our method to annihilation at rest,
where we find agreement with experiment, and suggest other avenues for its use.Comment: 24 pages, 3 figures, 1 table, PSI-preprin
Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: π π * -π σ*energy gap propensity and ortho-substitution effect
Lifetimes of the first electronic excited state (S1) of fluorine and methyl (o-, m-, and p-) substituted phenols and their complexes with one ammonia molecule have been measured for the 00 transition and for the intermolecular stretching σ1 levels in complexes using picosecond pump-probe spectroscopy. Excitation energies to the S1 (π π *) and S2 (π σ*) states are obtained by quantum chemical calculations at the MP2 and CC2 level using the aug-cc-pVDZ basis set for the ground-state and the S1 optimized geometries. The observed lifetimes and the energy gaps between the π π * and π σ* states show a good correlation, the lifetime being shorter for a smaller energy gap. This propensity suggests that the major dynamics in the excited state concerns an excited state hydrogen detachment or transfer (ESHD/T) promoted directly by a S1 / S2 conical intersection, rather than via internal conversion to the ground-state. A specific shortening of lifetime is found in the o-fluorophenol-ammonia complex and explained in terms of the vibronic coupling between the π π * and π σ* states occurring through the out-of-plane distortion of the C-F bond.Fil: Pino, Gustavo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Oldani, Andres Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Marceca, Ernesto José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Fujii, M.. Tokyo Institute of Technology; JapónFil: Ishiuchi, S.-I.. Tokyo Institute of Technology; JapónFil: Miyazaki, M.. Tokyo Institute of Technology; JapónFil: Broquier, M.. Centre National de la Recherche Scientifique; Francia. Universite Paris-Saclay;Fil: Dedonder, C.. Centre National de la Recherche Scientifique; Francia. Universite Paris-Saclay;Fil: Jouvet, C.. Universite Paris-Saclay; . Centre National de la Recherche Scientifique; Franci
Generalized harmonic formulation in spherical symmetry
In this pedagogically structured article, we describe a generalized harmonic
formulation of the Einstein equations in spherical symmetry which is regular at
the origin. The generalized harmonic approach has attracted significant
attention in numerical relativity over the past few years, especially as
applied to the problem of binary inspiral and merger. A key issue when using
the technique is the choice of the gauge source functions, and recent work has
provided several prescriptions for gauge drivers designed to evolve these
functions in a controlled way. We numerically investigate the parameter spaces
of some of these drivers in the context of fully non-linear collapse of a real,
massless scalar field, and determine nearly optimal parameter settings for
specific situations. Surprisingly, we find that many of the drivers that
perform well in 3+1 calculations that use Cartesian coordinates, are
considerably less effective in spherical symmetry, where some of them are, in
fact, unstable.Comment: 47 pages, 15 figures. v2: Minor corrections, including 2 added
references; journal version
Excited States of Proton-bound DNA/RNA Base Homo-dimers: Pyrimidines
We are presenting the electronic photo fragment spectra of the protonated
pyrimidine DNA bases homo-dimers. Only the thymine dimer exhibits a well
structured vibrational progression, while protonated monomer shows broad
vibrational bands. This shows that proton bonding can block some non radiative
processes present in the monomer.Comment: We acknowledge the use of the computing facility cluster GMPCS of the
LUMAT federation (FR LUMAT 2764
An Invitation to Higher Gauge Theory
In this easy introduction to higher gauge theory, we describe parallel
transport for particles and strings in terms of 2-connections on 2-bundles.
Just as ordinary gauge theory involves a gauge group, this generalization
involves a gauge '2-group'. We focus on 6 examples. First, every abelian Lie
group gives a Lie 2-group; the case of U(1) yields the theory of U(1) gerbes,
which play an important role in string theory and multisymplectic geometry.
Second, every group representation gives a Lie 2-group; the representation of
the Lorentz group on 4d Minkowski spacetime gives the Poincar\'e 2-group, which
leads to a spin foam model for Minkowski spacetime. Third, taking the adjoint
representation of any Lie group on its own Lie algebra gives a 'tangent
2-group', which serves as a gauge 2-group in 4d BF theory, which has
topological gravity as a special case. Fourth, every Lie group has an 'inner
automorphism 2-group', which serves as the gauge group in 4d BF theory with
cosmological constant term. Fifth, every Lie group has an 'automorphism
2-group', which plays an important role in the theory of nonabelian gerbes. And
sixth, every compact simple Lie group gives a 'string 2-group'. We also touch
upon higher structures such as the 'gravity 3-group' and the Lie 3-superalgebra
that governs 11-dimensional supergravity.Comment: 60 pages, based on lectures at the 2nd School and Workshop on Quantum
Gravity and Quantum Geometry at the 2009 Corfu Summer Institut
Large genomic differences between Moraxella bovoculi isolates acquired from the eyes of cattle with infectious bovine keratoconjunctivitis versus the deep nasopharynx of asymptomatic cattle
Citation: Dickey, A. M., Loy, J. D., Bono, J. L., Smith, T. P. L., Apley, M. D., Lubbers, B. V., . . . Clawson, M. L. (2016). Large genomic differences between Moraxella bovoculi isolates acquired from the eyes of cattle with infectious bovine keratoconjunctivitis versus the deep nasopharynx of asymptomatic cattle. Veterinary Research, 47, 11. doi:10.1186/s13567-016-0316-2Moraxella bovoculi is a recently described bacterium that is associated with infectious bovine keratoconjunctivitis (IBK) or "pinkeye" in cattle. In this study, closed circularized genomes were generated for seven M. bovoculi isolates: three that originated from the eyes of clinical IBK bovine cases and four from the deep nasopharynx of asymptomatic cattle. Isolates that originated from the eyes of IBK cases profoundly differed from those that originated from the nasopharynx of asymptomatic cattle in genome structure, gene content and polymorphism diversity and consequently placed into two distinct phylogenetic groups. These results suggest that there are genetically distinct strains of M. bovoculi that may not associate with IBK
Ion-Induced Dipole Interactions and Fragmentation Times : C -C Chromophore Bond Dissociation Channel
The fragmentation times corresponding to the loss of the chromophore
(C-- C bond dissociation channel) after photoexcitation at 263
nm have been investigated for several small peptides containing tryptophan or
tyrosine. For tryptophan-containing peptides, the aromatic chromophore is lost
as an ionic fragment (m/z 130), and the fragmentation time increases with the
mass of the neutral fragment. In contrast, for tyrosine-containing peptides the
aromatic chromophore is always lost as a neutral fragment (mass = 107 amu) and
the fragmentation time is found to be fast (\textless{}20 ns). These different
behaviors are explained by the role of the postfragmentation interaction in the
complex formed after the C--C bond cleavage
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