5,814 research outputs found
Sharp transition for single polarons in the one-dimensional Su-Schrieffer-Heeger model
We study a single polaron in the Su-Schrieffer-Heeger (SSH) model using four
different techniques (three numerical and one analytical). Polarons show a
smooth crossover from weak to strong coupling, as a function of the
electron-phonon coupling strength , in all models where this coupling
depends only on phonon momentum . In the SSH model the coupling also depends
on the electron momentum ; we find it has a sharp transition, at a critical
coupling strength , between states with zero and nonzero momentum of
the ground state. All other properties of the polaron are also singular at
, except the average number of phonons in the polaronic
cloud. This result is representative of all polarons with coupling depending on
and , and will have important experimental consequences (eg., in ARPES
and conductivity experiments)
Interplay between charge-lattice interaction and strong electron correlations in cuprates: phonon anomaly and spectral kinks
We investigate the interplay between strong electron correlations and
charge-lattice interaction in cuprates. The coupling between half breathing
bond stretching phonons and doped holes in the t-t'-J model is studied by
limited phonon basis exact diagonalization method. Nonadiabatic electron-phonon
interaction leads to the splitting of the phonon spectral function at half-way
to the zone boundary at and
to low energy kink feature in the electron dispersion, in agreement with
experimental observations. Another kink due to strong electron correlation
effects is observed at higher energy, depending on the strength of the
charge-lattice coupling.Comment: 4 pages, 3 figure
Design, synthesis and biological activity of selective hCAs inhibitors based on 2-(benzylsulfinyl)benzoic acid scaffold
A large library of derivatives based on the scaffold of 2-(benzylsulfinyl)benzoic acid were synthesised and tested as atypical inhibitors against four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). The exploration of the chemical space around the main functional groups led to the discovery of selective hCA IX inhibitors in the micromolar/nanomolar range, thus establishing robust structure-activity relationships within this versatile scaffold. HPLC separation of some selected chiral compounds and biological evaluation of the corresponding enantiomers was performed along with molecular modelling studies on the most active derivatives
Evolution of magnetic phases and orbital occupation in (SrMnO3)n/(LaMnO3)2n superlattices
The magnetic and electronic modifications induced at the interfaces in
(SrMnO)/(LaMnO) superlattices have been investigated
by linear and circular magnetic dichroism in the Mn L x-ray absorption
spectra. Together with theoretical calculations, our data demonstrate that the
charge redistribution across interfaces favors in-plane ferromagnetic (FM)
order and orbital occupation, in agreement with the
average strain. Far from interfaces, inside LaMnO, electron localization
and local strain favor antiferromagnetism (AFM) and
orbital occupation. For the high density of interfacial planes ultimately
leads to dominant FM order forcing the residual AFM phase to be in-plane too,
while for the FM layers are separated by AFM regions having
out-of-plane spin orientation.Comment: accepted for publication as a Rapid Communication in Physical Review
Free energy of the Fr\"ohlich polaron in two and three dimensions
We present a novel Path Integral Monte Carlo scheme to solve the Fr\"ohlich
polaron model. At intermediate and strong electron-phonon coupling, the polaron
self-trapping is properly taken into account at the level of an effective
action obtained by a preaveraging procedure with a retarded trial action. We
compute the free energy at several couplings and temperatures in three and two
dimensions. Our results show that the accuracy of the Feynman variational upper
bound for the free energy is always better than 5% although the thermodynamics
derived from it is not correct. Our estimates of the ground state energies
demonstrate that the second cumulant correction to the variational upper bound
predicts the self energy to better than 1% at intermediate and strong coupling.Comment: RevTeX 7 pages 3 figures, revised versio
Measuring the Three-Dimensional Structure of Galaxy Clusters. II. Are clusters of galaxies oblate or prolate?
The intrinsic shape of galaxy clusters can be obtained through a combination
of X-ray and Sunyaev-Zeldovich effect observations once cosmological parameters
are assumed to be known. In this paper we discuss the feasibility of modelling
galaxy clusters as either prolate or oblate ellipsoids. We analyze the
intra-cluster medium distribution for a sample of 25 X-ray selected clusters,
with measured Sunyaev-Zeldovich temperature decrements. A mixed population of
prolate and oblate ellipsoids of revolution fits the data well, with prolate
shapes preferred on a 60-76% basis. We observe an excess of clusters nearly
aligned along the line of sight, with respect to what is expected from a
randomly oriented cluster population, which might imply the presence of a
selection bias in our sample. We also find signs that a more general triaxial
morphology might better describe the morphology of galaxy clusters. Additional
constraints from gravitational lensing could disentangle the degeneracy between
an ellipsoidal and a triaxial morphology, and could also allow an unbiased
determination of the Hubble constant.Comment: 9 pages, 8 figures, accepted for publication in Astrophys.
Clinical Features and Outcomes of 124 Italian Patients With Treatment Resistant Depression: A Real-World, Prospective Study
Taking screenshots of the invisible: A study on bacterial contamination of mobile phones from university students of healthcare professions in Rome, Italy
Mobile phones (MPs) are commonly used both in the personal and professional life. We assessed microbiological contamination of MPs from 108 students in healthcare professions (HPs), in relation to their demographic characteristics and MPs handling habits, collected by means of a questionnaire. Cultural and biochemical tests were performed, and statistical analyses were carried out. Staphylococci were present in 85% of MPs, Enterococci in 37%, Coliforms in 6.5%; E. coli was never detected. Staphylococcus epidermidis was the most frequently isolated staphylococcal species (72% of MPs), followed by S. capitis (14%), S. saprophyticus, S. warneri, S. xylosus (6%), and by S. aureus (4%). Heterotrophic Plate Counts (HPC) at 37◦C, ranged from 0 to 1.2 × 104 CFU/dm2 (mean = 362 CFU/dm2). In univariate analysis, the male gender only was significantly associated with higher HPCs and enterococcal contamination. Multiple linear regression models explained only 17% and 16% of the HPC 37◦C and staphylococcal load variability, respectively. Developing specific guidelines for a hygienic use of MPs in clinical settings, for preventing cross-infection risks, is advisable, as well as introducing specific training programs to HP students. MPs decontamination procedures could also be implemented in the community
The CMS Monte Carlo Production System: Development and Design
The CMS production system has undergone a major architectural upgrade from its predecessor, with the goal of reducing the operational manpower needed and preparing for the large scale production required by the CMS physics plan. The new production system is a tiered architecture that facilitates robust and distributed production request processing and takes advantage of the multiple Grid and farm resources available to the CMS experiment
Antimicrobial activity of some essential oils against methicillin-susceptible and methicillin-resistant staphylococcus pseudintermedius-associated pyoderma in dogs
This study aimed to test in vitro the antimicrobial activity of 11 essential oils (EOs) against four methicillin-resistant Staphylococcus pseudintermedius (MRSP) and four methicillin-susceptible S. pseudintermedius (MSSP) clinical isolates. The obtained findings demonstrated a clear in vitro efficacy of some tested EOs against both MRSP and MSSP strains. Particularly, modal minimum inhibitory concentration (MIC) values ranging from 1:2048 v/v for Melissa officinalis against an MSSP strain to 1:256 v/v for Cymbopogon citratus against all MRSP strains were observed. The best results, highlighting a modal MIC value of 1:1024 v/v for all tested isolates, was provided by Cinnamomum zeylanicum. Intriguingly, Cinnamomum zeylanicum showed, in many cases, a correspondence between minimum bactericidal concentration (MBC) and MIC values, indicating that the inhibiting dose is also often bactericidal. Moreover, a mild antibacterial and bactericidal activity against both MRSP and MSSP isolates was detected for the other tested EOs. Considering the zoonotic potential of S. pseudintermedius and the increased dissemination of multidrug-resistant strains, the employment of EOs could be useful for the treatment of canine pyoderma. Since antibiotic resistance has become the most urgent issue, from the perspective of the One Health initiative, alternative therapeutic approaches are desirable to limit the use of antibiotics or to improve the efficacy of conventional therapies
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