194 research outputs found
A constructive approach to the soliton solutions of integrable quadrilateral lattice equations
Scalar multidimensionally consistent quadrilateral lattice equations are
studied. We explore a confluence between the superposition principle for
solutions related by the Backlund transformation, and the method of solving a
Riccati map by exploiting two kn own particular solutions. This leads to an
expression for the N-soliton-type solutions of a generic equation within this
class. As a particular instance we give an explicit N-soliton solution for the
primary model, which is Adler's lattice equation (or Q4).Comment: 22 page
Effective Non-Hermitian Hamiltonians for Studying Resonance Statistics in Open Disordered Systems
We briefly discuss construction of energy-dependent effective non-hermitian
hamiltonians for studying resonances in open disordered systemsComment: Latex, 20 pages, 1 fig. Expanded version of a talk at the Workshop on
Pseudo-Hermitian Hamiltonians in Quantum Physics IX, June 21-24 2010,
Zhejiang University, Hangzhou, China. Accepted for publication in the
Internationa Journal of Theoretical Physics (Springer Verlag
Quantum effects on the BKT phase transition of two-dimensional Josephson arrays
The phase diagram of two dimensional Josephson arrays is studied by means of
the mapping to the quantum XY model. The quantum effects onto the
thermodynamics of the system can be evaluated with quantitative accuracy by a
semiclassical method, the {\em pure-quantum self-consistent harmonic
approximation}, and those of dissipation can be included in the same framework
by the Caldeira-Leggett model. Within this scheme, the critical temperature of
the superconductor-to-insulator transition, which is a
Berezinskii-Kosterlitz-Thouless one, can be calculated in an extremely easy way
as a function of the quantum coupling and of the dissipation mechanism.
Previous quantum Monte Carlo results for the same model appear to be rather
inaccurate, while the comparison with experimental data leads to conclude that
the commonly assumed model is not suitable to describe in detail the real
system.Comment: 4 pages, 2 figures, to be published in Phys. Rev.
Uncoupled continuous-time random walks: Solution and limiting behavior of the master equation
A detailed study is presented for a large class of uncoupled continuous-time
random walks (CTRWs). The master equation is solved for the Mittag-Leffler
survival probability. The properly scaled diffusive limit of the master
equation is taken and its relation with the fractional diffusion equation is
discussed. Finally, some common objections found in the literature are
thoroughly reviewed.Comment: Preprint version of an already published paper. 8 page
CoRoT/ESTA-TASK 1 and TASK 3 comparison of the internal structure and seismic properties of representative stellar models: Comparisons between the ASTEC, CESAM, CLES, GARSTEC and STAROX codes
We compare stellar models produced by different stellar evolution codes for
the CoRoT/ESTA project, comparing their global quantities, their physical
structure, and their oscillation properties. We discuss the differences between
models and identify the underlying reasons for these differences. The stellar
models are representative of potential CoRoT targets. Overall we find very good
agreement between the five different codes, but with some significant
deviations. We find noticeable discrepancies (though still at the per cent
level) that result from the handling of the equation of state, of the opacities
and of the convective boundaries. The results of our work will be helpful in
interpreting future asteroseismology results from CoRoT.Comment: 26 pages, 21 figures, accepted for publication in Astrophysics and
Space Science, CoRoT/ESTA Volum
Global stabilization of feedforward systems under perturbations in sampling schedule
For nonlinear systems that are known to be globally asymptotically
stabilizable, control over networks introduces a major challenge because of the
asynchrony in the transmission schedule. Maintaining global asymptotic
stabilization in sampled-data implementations with zero-order hold and with
perturbations in the sampling schedule is not achievable in general but we show
in this paper that it is achievable for the class of feedforward systems. We
develop sampled-data feedback stabilizers which are not approximations of
continuous-time designs but are discontinuous feedback laws that are
specifically developed for maintaining global asymptotic stabilizability under
any sequence of sampling periods that is uniformly bounded by a certain
"maximum allowable sampling period".Comment: 27 pages, 5 figures, submitted for possible publication to SIAM
Journal Control and Optimization. Second version with added remark
Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad
[EN] The intramolecular electron transfer in the naproxen-N-methylpyrrolidine dyad has been investigated by spin chemistry methods. The existence of CIDNP in a high magnetic field points to electron transfer as a possible mechanism of the quenching of the excited state of a dyad. However, the failure to detect magnetic field effects on triplet yield makes us conclude that this quenching mechanism is not the only one. The observation of CIDNP effects in the dyad in the media of low polarity and the short risetime of triplet state formation indicate a potential role of exciplex in the quenching of the excited state of the dyad.This work was supported by the Grants 08-03-00372 and 11-03-01104 of Russian Foundation of Basic Research, and the grant of Priority Programs of RAS, No. 5.1.5.Magin, I.; Polyakov, N.; Khramtsova, E.; Kruppa, A.; Tsentalovich, Y.; Leshina, T.; Miranda Alonso, MÁ.... (2011). Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad. Chemical Physics Letters. 516(1-3):51-55. https://doi.org/10.1016/j.cplett.2011.09.057S51555161-
The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation
We give a theoretical analysis of published experimental studies of the
effects of impurities and disorder on the superconducting transition
temperature, T_c, of the organic molecular crystals kappa-ET_2X and beta-ET_2X
(where ET is bis(ethylenedithio)tetrathiafulvalene and X is an anion eg I_3).
The Abrikosov-Gorkov (AG) formula describes the suppression of T_c both by
magnetic impurities in singlet superconductors, including s-wave
superconductors and by non-magnetic impurities in a non-s-wave superconductor.
We show that various sources of disorder lead to the suppression of T_c as
described by the AG formula. This is confirmed by the excellent fit to the
data, the fact that these materials are in the clean limit and the excellent
agreement between the value of the interlayer hopping integral, t_perp,
calculated from this fit and the value of t_perp found from angular-dependant
magnetoresistance and quantum oscillation experiments. If the disorder is, as
seems most likely, non-magnetic then the pairing state cannot be s-wave. We
show that the cooling rate dependence of the magnetisation is inconsistent with
paramagnetic impurities. Triplet pairing is ruled out by several experiments.
If the disorder is non-magnetic then this implies that l>=2, in which case
Occam's razor suggests that d-wave pairing is realised. Given the proximity of
these materials to an antiferromagnetic Mott transition, it is possible that
the disorder leads to the formation of local magnetic moments via some novel
mechanism. Thus we conclude that either kappa-ET_2X and beta-ET_2X are d-wave
superconductors or else they display a novel mechanism for the formation of
localised moments. We suggest systematic experiments to differentiate between
these scenarios.Comment: 18 pages, 5 figure
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Binding adaptation of GS 441524 diversifies macro domains and downregulate SARS CoV 2 de MARylation capacity
Viral infection in cells triggers a cascade of molecular defense mechanisms to maintain host cell homoeostasis. One of these mechanisms is ADP ribosylation, a fundamental post translational modification PTM characterized by the addition of ADP ribose ADPr on substrates. Poly ADP ribose polymerases PARPs are implicated in this process and they perform ADP ribosylation on host and pathogen proteins. Some viral families contain structural motifs that can reverse this PTM. These motifs known as macro domains MDs are evolutionarily conserved protein domains found in all kingdoms of life. They are divided in different classes with the viral belonging to Macro D type class because of their properties to recognize and revert the ADP ribosylation. Viral MDs are potential pharmaceutical targets, capable to counteract host immune response. Sequence and structural homology between viral and human MDs are an impediment for the development of new active compounds against their function. Remdesivir, is a drug administrated in viral infections inhibiting viral replication through RNA dependent RNA polymerase RdRp . Herein, GS 441524, the active metabolite of the remdesivir, is tested as a hydrolase inhibitor for several viral MDs and for its binding to human homologs found in PARPs. This study presents biochemical and biophysical studies, which indicate that GS 441524 selectively modifies SARS CoV 2 MD de MARylation activity, while it does not interact with hPARP14 MD2 and hPARP15 MD2. The structural investigation of MD GS 441524 complexes, using solution NMR and X ray crystallography, discloses the impact of certain amino acids in ADPr binding cavity suggesting that F360 and its adjacent residues tune the selective binding of the inhibitor to SARS CoV 2 M
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