7,526 research outputs found
Electron-phonon coupling close to a metal-insulator transition in one dimension
We consider a one-dimensional system of electrons interacting via a
short-range repulsion and coupled to phonons close to the metal-insulator
transition at half filling. We argue that the metal-insulator transition can be
described as a standard one dimensional incommensurate to commensurate
transition, even if the electronic system is coupled to the lattice distortion.
By making use of known results for this transition, we prove that low-momentum
phonons do not play any relevant role close to half-filling, unless their
coupling to the electrons is large in comparison with the other energy scales
present in the problem. In other words the effective strength of the
low-momentum transferred electron-phonon coupling does not increase close to
the metal-insulator transition, even though the effective velocity of the
mobile carriers is strongly diminished.Comment: 20 pages, REVTEX styl
A New Approach to Equations with Memory
In this work, we present a novel approach to the mathematical analysis of
equations with memory based on the notion of a state, namely, the initial
configuration of the system which can be unambiguously determined by the
knowledge of the future dynamics. As a model, we discuss the abstract version
of an equation arising from linear viscoelasticity. It is worth mentioning that
our approach goes back to the heuristic derivation of the state framework,
devised by L.Deseri, M.Fabrizio and M.J.Golden in "The concept of minimal state
in viscoelasticity: new free energies and applications to PDEs", Arch. Ration.
Mech. Anal., vol. 181 (2006) pp.43-96. Starting from their physical
motivations, we develop a suitable functional formulation which, as far as we
know, is completely new.Comment: 39 pages, no figur
Comment on ``Enhancement of the Tunneling Density of States in Tomonaga-Luttinger Liquids''
In a recent Physical Review Letter, Oreg and Finkel'stein (OF) have
calculated the electron density of states (DOS) for tunneling into a repulsive
Luttinger liquid close to the location of an impurity. The result of their
calculation is a DOS which is enhanced with respect to the pure system, and
moreover diverging for not too strong repulsion. In this Comment we intend to
show that OF's calculation suffers from a subtle flaw which, being corrected,
results into a DOS not only vanishing at zero frequency but in fact suppressed
in comparison with the DOS of a pure Luttinger liquid.Comment: 1 page, Revte
A measure of tripartite entanglement in bosonic and fermionic systems
We describe an efficient theoretical criterion suitable for the evaluation of
the tripartite entanglement of any mixed three-boson or -fermion state, based
on the notion of the entanglement of particles for bipartite systems of
identical particles. Our approach allows one to quantify the accessible amount
of quantum correlations in the systems without any violation of the local
particle number superselection rule. A generalization of the tripartite
negativity is here applied to some correlated systems including the
continuous-time quantum walks of identical particles (both for bosons and
fermions) and compared with other criteria recently proposed in the literature.
Our results show the dependence of the entanglement dynamics upon the quantum
statistics: the bosonic bunching results into a low amount of quantum
correlations while Fermi-Dirac statistics allows for higher values of the
entanglement.Comment: 19 pages, 3 figure
Reply to the Comment on "Enhancement of the Tunneling Density of States in Tomonaga-Luttinger Liquids"
In their comment Fabrizio and Gogolin dispute our result of the enhancement
of the tunneling density of states in a Tomonaga-Luttinger liquid at the
location of a backward scattering defect [Phys. Rev. Lett. 76, 4230(1996);
cond-mat/9601020]. They state that the anticommutativity of the fermion
operators of the left and right moving electrons was not considered properly in
the Letter. We show in the Reply that the result of the Letter can be
reproduced following the Comment when its calculations are performed correctly.
This clearly indicates that the question about the anticommutation relations
was raised by Fabrizio and Gogolin without serious grounds.Comment: Published in PRL as a Reply to the Comment by Fabrizio and Gogolin
(cond-mat/9702080
Anopheline salivary protein genes and gene families: an evolutionary overview after the whole genome sequence of sixteen Anopheles species
Background: Mosquito saliva is a complex cocktail whose pharmacological properties play an essential role in
blood feeding by counteracting host physiological response to tissue injury. Moreover, vector borne pathogens are
transmitted to vertebrates and exposed to their immune system in the context of mosquito saliva which, in virtue
of its immunomodulatory properties, can modify the local environment at the feeding site and eventually affect
pathogen transmission. In addition, the host antibody response to salivary proteins may be used to assess human
exposure to mosquito vectors. Even though the role of quite a few mosquito salivary proteins has been clarified in
the last decade, we still completely ignore the physiological role of many of them as well as the extent of their
involvement in the complex interactions taking place between the mosquito vectors, the pathogens they transmit
and the vertebrate host. The recent release of the genomes of 16 Anopheles species offered the opportunity to get
insights into function and evolution of salivary protein families in anopheline mosquitoes.
Results: Orthologues of fifty three Anopheles gambiae salivary proteins were retrieved and annotated from 18
additional anopheline species belonging to the three subgenera Cellia, Anopheles, and Nyssorhynchus. Our analysis
included 824 full-length salivary proteins from 24 different families and allowed the identification of 79 novel
salivary genes and re-annotation of 379 wrong predictions. The comparative, structural and phylogenetic analyses
yielded an unprecedented view of the anopheline salivary repertoires and of their evolution over 100 million years
of anopheline radiation shedding light on mechanisms and evolutionary forces that contributed shaping the
anopheline sialomes.
Conclusions: We provide here a comprehensive description, classification and evolutionary overview of the main
anopheline salivary protein families and identify two novel candidate markers of human exposure to malaria vectors
worldwide. This anopheline sialome catalogue, which is easily accessible as hyperlinked spreadsheet, is expected to
be useful to the vector biology community and to improve the capacity to gain a deeper understanding of
mosquito salivary proteins facilitating their possible exploitation for epidemiological and/or pathogen-vector-host
interaction studies
Econometric Modeling and Analysis of Residential Water Demand Based on Unbalanced Panel Data
This paper develops an econometric methodology devised to analyze a sample of time unbalanced panel data on residential water consumption in the French island La Reunion with the purpose to bring out the main determinants of household water consumption and estimate the importance of water consumption by uses. For this purpose, we specify a daily panel econometric model and derive, by performing a time aggregation, a general linear regression model accounting for water consumption data recorded on periods of any calendar date and time length. To esti-mate efficiently the parameters of this model we develop a feasible two step generalized least square method. Using the principle of best linear unbiased prediction, we finally develop an approach allowing to consistently break down the volume of water consumption recorded on household water bills by uses, namely by enforcing this estimated decomposition to add up to the observed total. The application of this methodology to a sample of 437 unbalanced panel observations shows the scope of this approach for the empirical analysis of actual data.econometric modeling; water consumption; panel data
Increasing d-wave superconductivity by on site repulsion
We study by Variational Monte Carlo an extended Hubbard model away from half
filled band density which contains two competing nearest-neighbor interactions:
a superexchange favoring d-wave superconductivity and a repulsion
opposing against it. We find that the on-site repulsion effectively
enhances the strength of meanwhile suppressing that of , thus favoring
superconductivity. This result shows that attractions which do not involve
charge fluctuations are very well equipped against strong electron-electron
repulsion so much to get advantage from it.Comment: 4 pages, 3 figure
Analysis of food supplement with unusual raspberry ketone content
In recent years food supplement market increased constantly, including slimming products and against obesity. The case of rasberry ketone (RK) is here reported. HPTLC and HPLC-DAD analyses on a marketed product containing raspberry juice evidenced an abnormal quantity of RK, not in accordance with the juice natural content. The reported data confirm the need of adequate controls on marketed food supplements and the necessity of a complete adherence between labelling and real constitution of the product. Practical Applications: Determining the natural origin and assuring the consumers' safety for raspberry-based food supplement
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