352 research outputs found
On the preservation of coherence in the electronic wavepacket of a neutral and rigid polyatomic molecule
We present various types of reduced models including five vibrational modes
and three electronic states for the pyrazine molecule in order to investigate
the lifetime of electronic coherence in a rigid and neutral system. Using an
ultrafast optical pumping in the ground state (1 1 A g ), we prepare a coherent
superposition of two bright excited states, 1 1 B 2u and 1 1 B 1u , and reveal
the effect of the nuclear motion on the preservation of the electronic
coherence induced by the laser pulse. More specifically, two aspects are
considered: the anharmonicity of the potential energy surfaces and the
dependence of the transition dipole moments (TDMs) with respect to the nuclear
coordinates. To this end, we define an ideal model by making three
approximations: (i) only the five totally symmetric modes move, (ii) which
correspond to uncoupled harmonic oscillators, and (iii) the TDMs from the
ground electronic state to the two bright states are constant (Franck-Condon
approximation). We then lift the second and third approximations by
considering, first, the effect of anharmonicity, second, the effect of
coordinate-dependence of the TDMs (first-order Herzberg- Teller contribution),
third, both. Our detailed numerical study with quantum dynamics confirms
long-term revivals of the electronic coherence even for the most realistic
model
Random Matrices and the Convergence of Partition Function Zeros in Finite Density QCD
We apply the Glasgow method for lattice QCD at finite chemical potential to a
schematic random matrix model (RMM). In this method the zeros of the partition
function are obtained by averaging the coefficients of its expansion in powers
of the chemical potential. In this paper we investigate the phase structure by
means of Glasgow averaging and demonstrate that the method converges to the
correct analytically known result. We conclude that the statistics needed for
complete convergence grows exponentially with the size of the system, in our
case, the dimension of the Dirac matrix. The use of an unquenched ensemble at
does not give an improvement over a quenched ensemble.
We elucidate the phenomenon of a faster convergence of certain zeros of the
partition function. The imprecision affecting the coefficients of the
polynomial in the chemical potential can be interpeted as the appearance of a
spurious phase. This phase dominates in the regions where the exact partition
function is exponentially small, introducing additional phase boundaries, and
hiding part of the true ones. The zeros along the surviving parts of the true
boundaries remain unaffected.Comment: 17 pages, 14 figures, typos correcte
Book reviews
Foods, nutrients and food ingredients with authorised EU health claims.
M.J. SADLER (Ed.).
Woodhead Publishing is an imprint of Elsevier, Cambridge, UK, Waltham, US, Kidlington, UK, Series in Food
Science, Technology and Nutrition: Number 263, 2014
ISBN 978-0-85709-842-9 (print), ISBN 978-0-85709-848-1 (e-book), 397 page
Higher order corrections for shallow-water solitary waves: elementary derivation and experiments
We present an elementary method to obtain the equations of the shallow-water
solitary waves in different orders of approximation. The first two of these
equations are solved to get the shapes and propagation velocities of the
corresponding solitary waves. The first-order equation is shown to be
equivalent to the Korteweg-de Vries (KdV) equation, while the second-order
equation is solved numerically. The propagation velocity found for the solitary
waves of the second-order equation coincides with a known expression, but it is
obtained in a simpler way. By measuring the propagation velocity of solitary
waves in the laboratory, we demonstrate that the second-order theory gives a
considerably improved fit to experimental results.Comment: 15 pages, 8 EPS figures, uses IOP class file for LaTeX2e, slightly
revised versio
Postoperative interictal spikes during sleep contralateral to the operated side is associated with unfavourable surgical outcome in patients with preoperative bitemporal spikes
AbstractPurpose: To correlate the persistence of contralateral spikes during sleep after unilateral surgery with seizure outcome in a temporal lobe epilepsy (TLE) population and to test the existing hypotheses about the origin of the contralateral spikes in temporal lobe epilepsy. Methods: In the 19 patients selected for this study unilateral temporal lobe surgery was performed. To investigate the course of bilateral interictal epileptiform discharges observed before surgery in awake or sleep over the temporal lobe contralateral to surgery, 24h mobile 12 channel EEG recording was performed at minimum two, in average 4.6 (2â10) years after the surgery. Results: The association of postoperative contralateral spikes and non-seizure free outcome was highly significant. The existence of unilateral pathology before surgery was highly predictive for good outcome and disappearance of contralateral spikes. The association between good seizure outcome, disappearance of contralateral spikes and the existence of unilateral pathology before surgery was also significant. Our data partially satisfies the expectations of both the âseizure inducedâ and mirror type secondary epileptogenesis hypotheses concerning origin of contralateral spikes, but were not completely congruent with either of them. Conclusions: Unfavourable surgical outcome in a temporal lobe epilepsy group with preoperative independent bilateral interictal spikes was associated with the persistence of postoperative contralateral spikes and lack of unilateral pathology. Compared with seizure outcome the presence/absence and distribution of postoperative interictal spikes in NREM sleep not entirely fit to the predictions of existing secondary epileptogenesis hypotheses
Chaos and stability in a two-parameter family of convex billiard tables
We study, by numerical simulations and semi-rigorous arguments, a
two-parameter family of convex, two-dimensional billiard tables, generalizing
the one-parameter class of oval billiards of Benettin--Strelcyn [Phys. Rev. A
17, 773 (1978)]. We observe interesting dynamical phenomena when the billiard
tables are continuously deformed from the integrable circular billiard to
different versions of completely-chaotic stadia. In particular, we conjecture
that a new class of ergodic billiard tables is obtained in certain regions of
the two-dimensional parameter space, when the billiards are close to skewed
stadia. We provide heuristic arguments supporting this conjecture, and give
numerical confirmation using the powerful method of Lyapunov-weighted dynamics.Comment: 19 pages, 13 figures. Submitted for publication. Supplementary video
available at http://sistemas.fciencias.unam.mx/~dsanders
Microsatellite fingerprinting of grapevine (Vitis vinifera L.) varieties of the Carpathian Basin
Altogether 101 Vitis vinifera L. genotypes were analysed at 6 microsatellite loci (Scu8vv, Scu10vv, VVMD21, VVMD36, ssrVRZAG64, ssrVRZAG79). Ninety-seven were autochthonous accessions of the Carpathian Basin and 4 were international cultivars. The allele composition and sizes obtained with the 6 microsatellite primer pairs were appropriate for discrimination of 95 cultivars. Berry colour-variants of cvs GohĂ©r (GohĂ©r fehĂ©r-white and GohĂ©r piros-red), Lisztes (Lisztes fehĂ©r and Lisztes piros) as well as the cvs Bakator (Bakator piros and Bakator tĂŒdĆszĂn - light red) were exceptions.
Marker assisted selection (MAS) for powdery mildew resistance in a grapevine hybrid family
Research Note
Experimental study of alpha-induced reactions on 64Zn for the astrophysical gamma-process
For the synthesis of the heavy, proton rich isotopes in the astrophysical
gamma-process the precise knowledge of alpha-induced cross sections is of high
importance. We have initiated a comprehensive study of the 64Zn+alpha system
involving the cross section measurement of different reaction channels as well
as the elastic scattering at low, astrophysically relevant energies. In this
paper the experimental technique and some preliminary results of the
64Zn(alpha,p)67Ga cross section measurement are presented.Comment: Accepted for publication in the proceedings of the Nuclear Physics in
Astrophysics V conference. To appear in Journal of Physics Conference Serie
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