Mesoscopic transport beyond linear response

We present an approach to steady-state mesoscopic transport based on the maximum entropy principle formulation of nonequilibrium statistical mechanics. Our approach is not limited to the linear response regime. We show that this approach yields the quantization observed in the integer quantum Hall effect at large currents, which until now has been unexplained. We also predict new behaviors of non-local resistances at large currents in the presence of dirty contacts.Comment: 14 pages plus one figure (with an insert) (post-script codes appended), RevTeX 3.0, UCF-CM-93-004 (Revised

Safety considerations of plant polysaccharides for food use: a case study on phenolic-rich softwood galactoglucomannan extract

A growing population and concern over the sufficiency of natural resources for feeding this population has motivated researchers and industries to search for alternative and complementary sources of food ingredients and additives. Numerous plant species and parts of plants are explored as raw materials for food production. An interesting example is wood; to date, few wood-based additives or ingredients are authorized for food use. Wood hemicelluloses, such as softwood galactoglucomannans (GGM), constitute an abundant bioresource that shows a highly potential functionality in edible materials. Spruce GGM—“spruce gum”—acts as a multi-functional emulsion stabilizer, and it could be used in various processed food products, replacing less effective, conventional emulsifiers. Before new materials can be released onto the food market, their safety must be evaluated, according to the Novel Food regulation. This review focuses on the safety aspects that must be considered before polysaccharide- and phenolic-rich plant extracts can be awarded the status of authorized food ingredients. In this review, GGM is presented as a case study and examples are given of plant-based polysaccharides that are already authorized for food purposes. The legislation regarding Novel Food ingredients in Europe is also briefly reviewed.Peer reviewe

Core level spectroscopy of MoS2

X-ray photoelectron spectroscopy has been used to study mineral molybdenite, MoS2. The fitted core level spectra of sulphur 2p and molybdenum 3d states reveal several photon energy sensitive components. The high binding energy component in both spectra is proposed to originate from the uppermost sulphur or molybdenum atoms of an S-Mo-S sandwich layer of the hexagonal structure, respectively. The other features are suggested to be caused by the edge structures formed during the sample cleavage. The edge facets have much stronger chemical properties than the basal planes and they are known as the active sites of MoS2 when it is used as a catalyst. The spectral features and the effect of the structure of UHV cleaved MoS2 on them are discussed. (c) 2006 Elsevier B.V. All rights reserved

Korkean sulamislämpötilan kumulaattien magmaattinen eroosio kemiallisen liukenemisen kautta Bushveldin kompleksissa

The Bushveld Complex in South Africa shows spectacular examples of regional and local magmatic erosion of the floor cumulates by new melt batches that replenished the evolving magma chamber. Field observations indicate that, at some stratigraphic levels, at least, 15-20 m of pre-existing floor cumulates, often nearly monomineralic in composition (e.g., anorthosite or orthopyroxenite) were completely removed on a regional scale. What was the major agent of this erosion – (partial) melting or dissolution of the floor cumulates – remains poorly understood. Thermal melting appears to be a poor candidate because normal basaltic melts (∼1220-1260°C) cannot heat up the cumulates up to their melting temperature (∼1400-1500°C). We explored, therefore, the possibility of dissolution of these high-temperature-melting cumulates by slightly superheated (15°C above the liquidus) basaltic-andesitic melts that recharged the chamber and spread out laterally along its floor as basal flows. This was done using a freely available thermodynamic tool for phase equilibria modeling of open magmatic systems – the Magma Chamber Simulator. Our thermodynamic modelling shows that the superheated melts can digest up to 4.5-8.0 wt% of the bulk floor cumulates without inducing crystallization of the melts, despite them being much colder than the liquidus temperatures of these cumulates. This is equivalent to regional erosion of 15-24 m of the floor cumulates, given a basal melt layer of about 350 m thick. We conclude that the regional erosion of the high-temperature-melting floor cumulates in the Bushveld chamber has been mostly controlled by their chemical dissolution by replenishing superheated melts.The Bushveld Complex in South Africa shows spectacular examples of regional and local magmatic erosion of the floor cumulates by new melt batches that replenished the evolving magma chamber. Field observations indicate that, at some stratigraphic levels, at least, 15-20 m of pre-existing floor cumulates, often nearly monomineralic in composition (e.g., anorthosite or orthopyroxenite) were completely removed on a regional scale. What was the major agent of this erosion – (partial) melting or dissolution of the floor cumulates – remains poorly understood. Thermal melting appears to be a poor candidate because normal basaltic melts (∼1220-1260°C) cannot heat up the cumulates up to their melting temperature (∼1400-1500°C). We explored, therefore, the possibility of dissolution of these high-temperature-melting cumulates by slightly superheated (15°C above the liquidus) basaltic-andesitic melts that recharged the chamber and spread out laterally along its floor as basal flows. This was done using a freely available thermodynamic tool for phase equilibria modeling of open magmatic systems – the Magma Chamber Simulator. Our thermodynamic modelling shows that the superheated melts can digest up to 4.5-8.0 wt% of the bulk floor cumulates without inducing crystallization of the melts, despite them being much colder than the liquidus temperatures of these cumulates. This is equivalent to regional erosion of 15-24 m of the floor cumulates, given a basal melt layer of about 350 m thick. We conclude that the regional erosion of the high-temperature-melting floor cumulates in the Bushveld chamber has been mostly controlled by their chemical dissolution by replenishing superheated melts.Peer reviewe

The antimicrobial peptide TAT-RasGAP_317-326 inhibits the formation and expansion of bacterial biofilms in vitro.

Biofilms are structured aggregates of bacteria embedded in a self-produced matrix that develop in diverse ecological niches. Pathogenic bacteria can form biofilms on surfaces and in tissues, causing nosocomial and chronic infections that are difficult to treat. While antibiotics are largely inefficient in limiting biofilm formation and expansion, antimicrobial peptides (AMPs) are emerging as alternative antibiofilm treatments. In this study, we explore the effect of the newly described AMP TAT-RasGAP <sub>317-326</sub> on Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus biofilms. Efficiency of TAT-RasGAP <sub>317-326</sub> on biofilms was tested in vitro. Both viability of bacteria contained in the biofilm as well as biomass of the biofilm were quantified using resazurin and crystal violet staining, respectively. The antibiofilm effect of TAT-RasGAP <sub>317-326</sub> was compared with a selection of classical antibiotics and AMPs. We observe that TAT-RasGAP <sub>317-326</sub> inhibits biofilm formation at concentrations equivalent or two times greater than the minimum inhibitory concentration (MIC) of planktonic bacteria. Moreover, TAT-RasGAP <sub>317-326</sub> limits the expansion of A. baumannii and P. aeruginosa established biofilms at twice the concentration inhibiting biofilm formation. These results underscore the potential use of TAT-RasGAP <sub>317-326</sub> against biofilms and encourage further studies in the development of AMPs to treat biofilm-related infections

Segregation, precipitation, and \alpha-\alpha' phase separation in Fe-Cr alloys: a multi-scale modelling approach

Segregation, precipitation, and phase separation in Fe-Cr systems is investigated. Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy are used. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods has to be used. Using Exact Muffin-Tin Orbitals method the effective chemical potential as a function of Cr content (0-15 at.% Cr) is calculated for a surface, second atomic layer and bulk. At ~10 at.% Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr containing surfaces are expected when the Cr content exceeds ~10 at.%. The second atomic layer forms about 0.3 eV barrier for the migration of Cr atoms between bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. Using combined Monte Carlo molecular dynamics simulations, based on semiempirical potential, the precipitation of Cr into isolated pockets in bulk Fe-Cr and the upper limit of the solubility of Cr into Fe layers in Fe/Cr layer system is studied. The theoretical predictions are tested using spectroscopic measurements. Hard X-ray photoelectron spectroscopy and Auger electron spectroscopy investigations were carried out to explore Cr segregation and precipitation in Fe/Cr double layer and Fe_0.95Cr_0.05 and Fe_0.85Cr_0.15 alloys. Initial oxidation of Fe-Cr was investigated experimentally at 10^-8 Torr pressure of the spectrometers showing intense Cr_2O_3 signal. Cr segregation and the formation of Cr rich precipitates were traced by analysing the experimental spectral intensities with respect to annealing time, Cr content, and kinetic energy of the exited electron.Comment: 16 pages, 14 figures, 52 reference

Are neighbourhood food resources distributed inequitably by income and race in the USA? Epidemiological findings across the urban spectrum

ObjectiveMany recent policies focus on socioeconomic inequities in availability of healthy food stores and restaurants. Yet understanding of how socioeconomic inequities vary across neighbourhood racial composition and across the range from rural to urban settings is limited, largely due to lack of large, geographically and socio-demographically diverse study populations. Using a national sample, the authors examined differences in neighbourhood food resource availability according to neighbourhood-level poverty and racial/ethnic population in non-urban, low-density urban and high-density urban areas.DesignCross-sectional data from an observational cohort study representative of the US middle and high school-aged population in 1994 followed into young adulthood.ParticipantsUsing neighbourhood characteristics of participants in the National Longitudinal Study of Adolescent Health (Wave III, 2001–2002; n=13 995 young adults aged 18–28 years representing 7588 US block groups), the authors examined associations between neighbourhood poverty and race/ethnicity with neighbourhood food resource availability in urbanicity-stratified multivariable linear regression.Primary and secondary outcome measuresNeighbourhood availability of grocery/supermarkets, convenience stores and fast-food restaurants (measured as number of outlets per 100 km roadway).ResultsNeighbourhood race and income disparities were most pronounced in low-density urban areas, where high-poverty/high-minority areas had lower availability of grocery/supermarkets (β coefficient (β)=–1.91, 95% CI –2.73 to –1.09) and convenience stores (β=–2.38, 95% CI –3.62 to –1.14) and greater availability of fast-food restaurants (β=4.87, 95% CI 2.26 to 7.48) than low-poverty/low-minority areas. However, in high-density urban areas, high-poverty/low-minority neighbourhoods had comparatively greater availability of grocery/supermarkets (β=8.05, 95% CI 2.52 to 13.57), convenience stores (β=2.89, 95% CI 0.64 to 5.14) and fast-food restaurants (β=4.03, 95% CI 1.97 to 6.09), relative to low-poverty/low-minority areas.ConclusionsIn addition to targeting disproportionate fast-food availability in disadvantaged dense urban areas, our findings suggest that policies should also target disparities in grocery/supermarket and fast-food restaurant availability in low-density areas.Article summaryArticle focusUsing national data, we examined whether neighbourhood food resource availability exhibits joint race and socioeconomic inequities across levels of urbanicity.Key messagesSocio-demographic inequities in neighbourhood food resource availability were most pronounced in low-density urban (largely suburban) areas.In high-density urban areas, higher neighbourhood poverty was associated with greater availability of all food resources.Whereas policy has focused on dense urban settings, less urban areas might also benefit from policies addressing food access.Strengths and limitations of this studyWhile business records provide comparable data across the USA, these data may contain error and do not indicate availability of specific foods.National coverage enabled examination of the joint role of neighbourhood race and socioeconomic status across urban strata within a single study

Morphology of ledge patterns during step flow growth of metal surfaces vicinal to fcc(001)

The morphological development of step edge patterns in the presence of meandering instability during step flow growth is studied by simulations and numerical integration of a continuum model. It is demonstrated that the kink Ehrlich-Schwoebel barrier responsible for the instability leads to an invariant shape of the step profiles. The step morphologies change with increasing coverage from a somewhat triangular shape to a more flat, invariant steady state form. The average pattern shape extracted from the simulations is shown to be in good agreement with that obtained from numerical integration of the continuum theory.Comment: 4 pages, 4 figures, RevTeX 3, submitted to Phys. Rev.

Sharp and fuzzy observables on effect algebras

Observables on effect algebras and their fuzzy versions obtained by means of confidence measures (Markov kernels) are studied. It is shown that, on effect algebras with the (E)-property, given an observable and a confidence measure, there exists a fuzzy version of the observable. Ordering of observables according to their fuzzy properties is introduced, and some minimality conditions with respect to this ordering are found. Applications of some results of classical theory of experiments are considered.Comment: 23 page