722 research outputs found
Exact clesed form of the return probability on the Bethe lattice
An exact closed form solution for the return probability of a random walk on
the Bethe lattice is given. The long-time asymptotic form confirms a previously
known expression. It is however shown that this exact result reduces to the
proper expression when the Bethe lattice degenerates on a line, unlike the
asymptotic result which is singular. This is shown to be an artefact of the
asymptotic expansion. The density of states is also calculated.Comment: 7 pages, RevTex 3.0, 2 figures available upon request from
[email protected], to be published in J.Phys.A Let
On the compressibility equation of state for multicomponent adhesive hard sphere fluids
The compressibility equation of state for a multicomponent fluid of particles
interacting via an infinitely narrow and deep potential, is considered within
the mean spherical approximation (MSA). It is shown that for a class of models
leading to a particular form of the Baxter functions containing
density-independent stickiness coefficient, the compressibility EOS does not
exist, unlike the one-component case. The reason for this is that a direct
integration of the compressibility at fixed composition, cannot be carried out
due to the lack of a reciprocity relation on the second order partial
derivatives of the pressure with respect to two different densities. This is,
in turn, related to the inadequacy of the MSA. A way out to this drawback is
presented in a particular example, leading to a consistent compressibility
pressure, and a possible generalization of this result is discussed.Comment: 13 pages, no figures, accepted for publication Molec. Physics (2002
Diffusion and Trapping on a one-dimensional lattice
The properties of a particle diffusing on a one-dimensional lattice where at
each site a random barrier and a random trap act simultaneously on the particle
are investigated by numerical and analytical techniques. The combined effect of
disorder and traps yields a decreasing survival probability with broad
distribution (log-normal). Exact enumerations, effective-medium approximation
and spectral analysis are employed. This one-dimensional model shows rather
rich behaviours which were previously believed to exist only in higher
dimensionality. The possibility of a trapping-dominated super universal class
is suggested.Comment: 20 pages, Revtex 3.0, 13 figures in compressed format using uufiles
command, to appear in Phys. Rev. E, for an hard copy or problems e-mail to:
[email protected]
Osmotic pressure induced coupling between cooperativity and stability of a helix-coil transition
Most helix-coil transition theories can be characterized by a set of three
parameters: energetic, describing the (free) energy cost of forming a helical
state in one repeating unit; entropic, accounting for the decrease of entropy
due to the helical state formation; and geometric, indicating how many
repeating units are affected by the formation of one helical state. Depending
on their effect on the helix-coil transition, solvents or co-solutes can be
classified with respect to their action on these parameters. Solvent
interactions that alter the entropic cost of helix formation by their osmotic
action can affect both the stability (transition temperature) and the
cooperativity (transition interval) of the helix-coil transition. A consistent
inclusion of osmotic pressure effects in a description of helix-coil transition
for poly(L-glutamic acid) in solution with polyethylene glycol can offer an
explanation of the experimentally observed linear dependence of transition
temperature on osmotic pressure as well as the concurrent changes in the
cooperativity of the transition.Comment: 5 pages, 3 figures. To be submitted to Phys.Rev.Let
Thermal stability and long term hydrogen/deuterium release from soft to hard amorphous carbon layers analyzed using in-situ Raman spectroscopy. Comparison with Tore Supra deposits
The thermal stability of 200 nm thick plasma enhanced chemical vapor
deposited a-C:H and a-C:D layers ranging from soft to hard layers has been
studied and compared to that of deposits collected on the Tore Supra tokamak
plasma facing components by means of in-situ Raman spectroscopy. Linear ramp
heating and long term isotherms (from several minutes to 21 days) have been
performed and correlations between spectrometric parameters have been found.
The information obtained on the sp 2 clustering has been investigated by
comparing the G band shift and the 514 nm photon absorption evolution due to
the thermal treatment of the layer. The effects of isotopic substitution have
also been investigated.Comment: appears in Thin Solid Films, Elsevier, 201
Prevalence of Mycobacterium avium subsp. paratuberculosis in milk and dairy cattle in Southern Italy; preliminary results
Paratuberculosis affects all ruminants worldwide. Mycobacterium avium subsp. paratuberculosis could have a role in human diseases like Crohn\u2019s. Some extra EU countries request importation of MAP-free products. Italy has not yet actualized a control program and the diffusion of the infection is still unknown in Southern Italy. The aim of this study was to evaluate the prevalence of the infection in five regions of Southern Italy. Bulk tank milk and in-line milk filters were sampled in 780 dairy cattle herds and respectively analyzed by ELISA and real time PCR. One hundred and fifty-five out of 780 herds (19.9%) were found positive by ELISA and/or real time PCR. Individual milk samples were then collected from all the producing animals of positive herds and from a selection of negative herds. The estimated prevalence varies from region to region between 2.8% and 5.5%. Our results indicate that the disease is widespread in the five regions. The observed prevalence could be underestimated
Predicting your next OLAP query based on recent analytical sessions
International audienceIn Business Intelligence systems, users interact with data warehouses by formulating OLAP queries aimed at exploring multidimensional data cubes. Being able to predict the most likely next queries would provide a way to recommend interesting queries to users on the one hand, and could improve the efficiency of OLAP sessions on the other. In particular, query recommendation would proactively guide users in data exploration and improve the quality of their interactive experience. In this paper, we propose a framework to predict the most likely next query and recommend this to the user. Our framework relies on a probabilistic user behavior model built by analyzing previous OLAP sessions and exploiting a query similarity metric. To gain insight in the recommendation precision and on what parameters it depends, we evaluate our approach using different quality assessments
Interface state contribution to the photovoltaic effect in organic phototransistors:Photocapacitance measurements and optical sensing
Made available in DSpace on 2018-12-11T16:50:21Z (GMT). No. of bitstreams: 0
Previous issue date: 2018-01-01Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Instituto Nacional de Ciência e Tecnologia em Eletrônica OrgânicaWe report the results of an investigation into the contribution that trapping in interface states makes to the photovoltaic effect observed in organic phototransistors. To isolate this effect from other processes that occur in the transistor structure when under illumination, we focus attention on the photo-response of metal-insulator-semiconductor (MIS) capacitors - the core structure of transistors. The capacitors comprised poly(3-hexylthiophene), (P3HT), as the active semiconductor in combination with one of three insulators, namely, poly(amide-imide), (PAI), SU-8 photoresist and polysilsesquioxane (PSQ). Following initial characterization in the dark, the capacitor response was measured both during and after irradiation with light in the wavelength range 400–700 nm. Three different approaches were employed to study the photo-response, each providing a different insight into the processes occurring. Capacitance-voltage sweeps before, during and after illumination provided direct evidence supporting the view that the photovoltaic effect occurred as a result of electron trapping in interface states of density up to ∼2 × 1012 cm−2 in the P3HT/PAI combination but lower for SU-8 and PSQ. The dynamic photo-response, in which device capacitance was held constant by changing the applied bias, showed a fast component related to optically induced photoconduction in the semiconductor and a slower component reflecting the dynamics of interface electron trapping. Finally, photo-induced capacitance changes occurring with constant applied voltage were used to demonstrate a simple 3 × 3 imaging array.School of Electronic Engineering Bangor University, Dean StreetBrazilian Nanotechnology National Laboratory (LNNano) Brazilian Centre of Research in Energy and Materials (CNPEM)Department of Physics São Paulo State University (UNESP), PO Box 266Institute of Physics of São Carlos University of São Paulo (USP), PO Box 369Catarinense Federal Institute of Education Science and Technology, PO Box 21Department of Physics São Paulo State University (UNESP), PO Box 26
Effect of Polydispersity and Anisotropy in Colloidal and Protein Solutions: an Integral Equation Approach
Application of integral equation theory to complex fluids is reviewed, with
particular emphasis to the effects of polydispersity and anisotropy on their
structural and thermodynamic properties. Both analytical and numerical
solutions of integral equations are discussed within the context of a set of
minimal potential models that have been widely used in the literature. While
other popular theoretical tools, such as numerical simulations and density
functional theory, are superior for quantitative and accurate predictions, we
argue that integral equation theory still provides, as in simple fluids, an
invaluable technique that is able to capture the main essential features of a
complex system, at a much lower computational cost. In addition, it can provide
a detailed description of the angular dependence in arbitrary frame, unlike
numerical simulations where this information is frequently hampered by
insufficient statistics. Applications to colloidal mixtures, globular proteins
and patchy colloids are discussed, within a unified framework.Comment: 17 pages, 7 figures, to appear in Interdiscip. Sci. Comput. Life Sci.
(2011), special issue dedicated to Prof. Lesser Blu
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