625 research outputs found
Phase separation in a lattice model of a superconductor with pair hopping
We have studied the extended Hubbard model with pair hopping in the atomic
limit for arbitrary electron density and chemical potential. The Hamiltonian
considered consists of (i) the effective on-site interaction U and (ii) the
intersite charge exchange interactions I, determining the hopping of electron
pairs between nearest-neighbour sites. The model can be treated as a simple
effective model of a superconductor with very short coherence length in which
electrons are localized and only electron pairs have possibility of
transferring. The phase diagrams and thermodynamic properties of this model
have been determined within the variational approach, which treats the on-site
interaction term exactly and the intersite interactions within the mean-field
approximation. We have also obtained rigorous results for a linear chain (d=1)
in the ground state. Moreover, at T=0 some results derived within the random
phase approximation (and the spin-wave approximation) for d=2 and d=3 lattices
and within the low density expansions for d=3 lattices are presented. Our
investigation of the general case (as a function of the electron concentration
and as a function of the chemical potential) shows that, depending on the
values of interaction parameters, the system can exhibit not only the
homogeneous phases: superconducting (SS) and nonordered (NO), but also the
phase separated states (PS: SS-NO). The system considered exhibits interesting
multicritical behaviour including tricritical points.Comment: 15 pages, 9 figures; pdf-ReVTeX, final version, corrected typos;
submitted to Journal of Physics: Condensed Matte
Perception of Nuclear Energy and Coal in France and the Netherlands
This study focuses on the perception of large scale application of nuclear energy and coal in the Netherlands and France. The application of these energy-sources and the risks and benefits are judged differently by various group in society. In Europe, France has the highest density of nuclear power plants and the Netherlands has one of the lowest. In both countries scientists and social scientists completed a questionnaire assessing the perception of the large scale application of both energy sources. Furthermore, a number of variables relating to the socio cultural and political circumstances were measured. The results indicate that the French had a higher risk perception and a more negative attitude toward nuclear power than the Dutch. But they also assess the benefits of the use of nuclear power to be higher. Explanations for these differences are discussed
Role of eisosomes in the necrotrophic fungus Alternaria brassicicola
lternaria brassicicola is a fungal necrotroph responsible for the Brassicaceae dark spot disease. This fungus is a seed-borne pathogen that only affects the aerial parts of host plants causing great damages with major incidence on yield and product quality. Its transmission to seed is a major component of pathogen fitness promoting the dispersal and long-term survival of the fungus. Recently, we showed that several eisosomal protein encoding genes were overexpressed when germinated spores of A.brassicicola were exposed to osmotic and hydric stresses, which are the main constraints encountered by the fungus during the seed colonization process. MCC/eisosomes are membrane microdomains whose function is still unclear. They have been proposed to participate in the plasma membrane function by regulating the homeostasis of lipids and would promote the recruitment of specific proteins and their subsequent protection from endocytosis. Here, we deciphered the potential involvement of eisosome in pathogenicity using a reverse genetic approach by generating and characterizing mutants deficient for key eisosomal proteinencoding genes (?pil1, ?nce102, ?lsp1 and ?pil1?lsp1). In parallel, these proteins have been fused to GFP to monitor their cellular location during the plant infection and following the exposure to stresses. Depending on the mutants, the leaf and silique colonization processes were impaired by comparison to the wild-type. We also showed a strong impact of MCC/eisosome proteinmutations on the generation of appressoria-like structures
Phase Diagram of the 1D Anderson Lattice
We map out the phase diagram of the one--dimensional Anderson lattice by
studying the ground state magnetization as a function of band--filling using
the density matrix renormalization group technique. For strong coupling, we
find that the quarter--filled system has an S=0 ground state with strong
antiferromagnetic correlations. As additional electrons are put in, we find
first a ferromagnetic phase, as reported by M\"{o}ller and W\"{o}lfle, and then
a phase in which the ground state has total spin . Within this
phase, we find RKKY oscillations in the spin--spin correlation functions.Comment: REVTEX manuscript with 5 Postcript figures included in uu file.
Submitted to Phys. Rev.
ISML: an interface specification meta-language
In this paper we present an abstract metaphor model situated within a model-based user interface framework. The inclusion of metaphors in graphical user interfaces is a well established, but mostly craft-based strategy to design. A substantial body of notations and tools can be found within the model-based user interface design literature, however an explicit treatment of metaphor and its mappings to other design views has yet to be addressed. We introduce the Interface Specification Meta-Language (ISML) framework and demonstrate its use in comparing the semantic and syntactic features of an interactive system. Challenges facing this research are outlined and further work proposed
Soft and non-soft structural transitions in disordered nematic networks
Properties of disordered nematic elastomers and gels are theoretically
investigated with emphasis on the roles of non-local elastic interactions and
crosslinking conditions. Networks originally crosslinked in the isotropic phase
lose their long-range orientational order by the action of quenched random
stresses, which we incorporate into the affine-deformation model of nematic
rubber elasticity. We present a detailed picture of mechanical quasi-Goldstone
modes, which accounts for an almost completely soft polydomain-monodomain (P-M)
transition under strain as well as a ``four-leaf clover'' pattern in
depolarized light scattering intensity. Dynamical relaxation of the domain
structure is studied using a simple model. The peak wavenumber of the structure
factor obeys a power-law-type slow kinetics and goes to zero in true mechanical
equilibrium. The effect of quenched disorder on director fluctuation in the
monodomain state is analyzed. The random frozen contribution to the fluctuation
amplitude dominates the thermal one, at long wavelengths and near the P-M
transition threshold. We also study networks obtained by crosslinking
polydomain nematic polymer melts. The memory of initial director configuration
acts as correlated and strong quenched disorder, which renders the P-M
transition non-soft. The spatial distribution of the elastic free energy is
strongly dehomogenized by external strain, in contrast to the case of
isotropically crosslinked networks.Comment: 19 pages, 15 EPS figure
Optical properties of MgH2 measured in situ in a novel gas cell for ellipsometry/spectrophotometry
The dielectric properties of alpha-MgH2 are investigated in the photon energy
range between 1 and 6.5 eV. For this purpose, a novel sample configuration and
experimental setup are developed that allow both optical transmission and
ellipsometric measurements of a transparent thin film in equilibrium with
hydrogen. We show that alpha-MgH2 is a transparent, colour neutral insulator
with a band gap of 5.6 +/- 0.1 eV. It has an intrinsic transparency of about
80% over the whole visible spectrum. The dielectric function found in this work
confirms very recent band structure calculations using the GW approximation by
Alford and Chou [J.A. Alford and M.Y. Chou (unpublished)]. As Pd is used as a
cap layer we report also the optical properties of PdHx thin films.Comment: REVTeX4, 15 pages, 12 figures, 5 table
Long-term air pollution exposure, genome-wide DNA methylation and lung function in the lifelines cohort study
BACKGROUND: Long-term air pollution exposure is negatively associated with lung function, yet the mechanisms underlying this association are not fully clear. Differential DNA methylation may explain this association. OBJECTIVES: Our main aim was to study the association between long-term air pollution exposure and DNA methylation. METHODS: We performed a genome-wide methylation study using robust linear regression models in 1,017 subjects from the LifeLines cohort study to analyze the association between exposure to nitrogen dioxide (NO2) and particulate matter (PM2.5, fine particulate ma
Metanephric adenoma of the kidney: an unusual diagnostic challenge
Although metanephric adenoma (MA) is a rare, benign neoplasm of epithelial cells, it is often difficult to distinguish this entity from other malignant neoplasms preoperatively. We report a case of a large renal mass for which preoperative diagnosis was indeterminate, with the differential diagnosis including Wilm’s tumor, MA, and papillary renal cell carcinoma (PRCC). Accurate postoperative differentiation of MA from PRCC is critical because adjuvant therapy is considered after surgical resection of PRCC tumors
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