Reaction-diffusion waves with nonlinear boundary conditions

International audienceA reaction-di usion equation with nonlinear boundary condition is considered in a two-dimensional in nite strip. Existence of waves in the bistable case is proved by the Leray-Schauder method

Properness and Topological Degree for Nonlocal Reaction-Diffusion Operators

International audienceThe paper is devoted to integro-differential operators, which correspond to non-local reaction-diffusion equations considered on the whole axis. Their Fredholm property and properness will be proved. This will allow one to define the topological degree

Unified modelling of the thermoelectric properties in SrTiO3

Thermoelectric materials are opening a promising pathway to address energy conversion issues governed by a competition between thermal and electronic transport. Improving the efficiency is a difficult task, a challenge that requires new strategies to unearth optimized compounds. We present a theory of thermoelectric transport in electron doped SrTiO3, based on a realistic tight binding model that includes relevant scattering processes. We compare our calculations against a wide panel of experimental data, both bulk and thin films. We find a qualitative and quantitative agreement over both a wide range of temperatures and carrier concentrations, from light to heavily doped. Moreover, the results appear insensitive to the nature of the dopant La, B, Gd and Nb. Thus, the quantitative success found in the case of SrTiO3, reveals an efficient procedure to explore new routes to improve the thermoelectric properties in oxides.Comment: 5 figures, manuscript submitte

Investigating cytokine biomarkers as early predictors of poor clinical outcome following major trauma

Despite recent advances in critical care, trauma still continues to be the leading cause ofmorbidity and mortality among individuals under 40 years of age and the third main cause ofdeath throughout the world, carrying a substantial economic burden. Globally, the mostcommon traumatic injuries are acquired through penetrating wounds, blunt injuries or burnmechanisms. Recent reports from the UK suggest a significant change in the demographicsof major trauma. The typical major trauma patient is older, with a slight predominance ofmales, and with traumatic injuries resulted from falls from less than 2m in height.Mortality due to major trauma follows a biphasic pattern. Early fatalities occur due tohaemorrhagic shock or brain injuries, whereas the late deaths (>5 days post-trauma) areattributed to progressive multiple organ failure (MOF) and sepsis postulated to result fromdysfunctions of the immune system. Depending on the severity of trauma, the immuneresponse can be over-active with uncontrolled release of pro and anti-inflammatorymediators causing multiple organ failure.This study focusses on the second-phase mortality induced due to major trauma. Thehypothesis tested is that the late mortality and morbidity results from an imbalance of thepro and anti-inflammatory immune responses (SIRS and CARS) triggered after major trauma.While a balanced response of these two arms of the immune system result in homeostasis,the hyperactivity of the compensatory anti-inflammatory response (CARS) results inimmunosuppression and increased risk of nosocomial infections and late onset MOF.The study is designed to investigate the role of IL-6, IL-10, IL-12 and IL-4 in the developmentof the late onset MOF with a view to evaluating their use as a predictive biomarker of poorclinical outcome. The data from the analysis of 80 major trauma patients show averaged IL-6 7and IL-10 levels to decrease in major trauma patients from Day 1 to Day 5 post-admission(IL-6 p=0.000; IL-10 p=0.000), while the trends for IL-4 and IL-12 increased over the sameperiod for the cohort (IL-4 p=0.031; IL-12 p3), statisticallysignificant differences were observed in the Day 1 IL-10 and IL-6 levels at the cut off >3 forthe respective SOFA score (IL-10 p=0.023, IL -6 p=0.015) indicating a strong potential fortheir use as early biomarkers of poor clinical outcomes. The trends in Day 1IL - 10 and IL- 6concentration were maintained when the SOFA cluster cut offs were increased to > 6 (IL-10p=0.037; IL-6 p<0.001). When similar analyses were carried out with IL-12 data, a reversetrend was observed with higher Day 1 IL-12 levels being observed in the <3 Day 5 SOFAcluster, suggesting that high levels of IL-12 on Day 1 post-trauma is associated with goodclinical outcomes downstream. Although the IL-12 data failed to show statistical significanceat a SOFA cut off of 3 (p=0.268), when the data was clustered more stringently on a SOFA cutoff of 6, the differences were statistically significant (p= 0.023). Similar trends weremaintained for SOFA outcomes on Day 8. Similar to IL-6 and IL-10 patterns, high IL-4 levelson Day 1 post admission showed a significant association with poor outcome patient clusterson Day 5 (SOFA cut off 6; p=0.025)When cytokine levels were defined using Day 5 serum C-reactive protein concentration as ameasure of poor outcome (rather than SOFA scores), similar trends were observed.However, the data was not statistically significant, possibly due to confounding factorsresulting from a lower cohort size (n =30) where CRP records were available. In conclusion, amultiplex panel of these 4 cytokines may be of good predictive value for the earlystratification of major trauma patients for focussed clinical intervention and improvement ofclinical outcome

Thermoelectric La-doped SrTiO3 epitaxial layers with single-crystal quality: from nanometer to micrometer and mosaicity effects

High-quality thermoelectric LaxSr1-xTiO3 (LSTO) layers (here with x = 0.2), with thicknesses ranging from 20 nm to 700 nm, have been epitaxially grown on SrTiO3(001) substrates by enhanced solid-source oxide molecular-beam epitaxy. All films are atomically flat (with rms roughness < 0.2 nm), with low mosaicity (<0.1{\deg}), and present very low electrical resistivity (<5 x 10-4 ohm.cm at room temperature), one order of magnitude lower than commercial Nb-doped SrTiO3 single-crystalline substrate. The conservation of transport properties within this thickness range has been confirmed by thermoelectric measurements where Seebeck coefficients of around -60 microV/K have been found for all films, accordingly. Finally, a correlation is given between the mosaicity and the (thermo)electric properties. These functional LSTO films can be integrated on Si in opto-microelectronic devices as transparent conductor, thermoelectric elements or in non-volatile memory structures

Functional behaviour of TiO2films doped with noble metals

To evaluate the effects of different concentrations of noble metal in a TiO2 matrix, different films of both Ag:TiO2 and Au:TiO2 systems were prepared. Mechanical and tribological characterization was carried out to evaluate the coatings response as a function of the noble metals composition and (micro)structure of the films. The overall set of results indicates that the amorphous films reveal better results than the crystalline ones. For the amorphous samples, the reduced Young’s modulus and the adhesion critical loads followed similar tendencies in both sets of films. Wear rates were similar for all samples except for the one with the highest silver content. To improve brittleness of TiO2 films, the results seem to indicate that a slight metal doping is preferred, and Au showed to be a better choice than Ag. In fact, the sample with the lowest Au content revealed a better mechanical behaviour than the pure TiO2 film.This research was sponsored by FEDER funds through the COMPETE program (Programa Operacional Factores de Competitividade) and by FCT (Fundação para a Ciência e a Tecnologia), under the projects PEST-C/FIS/UI607/2013 and PEst-C/EME/UI0285/2013. The authors also acknowledge the financial support by the project Nano4color – Design and develop a new generation of color PVD coatings for decorative applications (FP7 EC R4SME Project No. 315286)

MAGNETRON SPUTTERING TECHNIQUE USED FOR COATINGS DEPOSITION; TECHNOLOGIES AND APPLICATIONS

Abstract. The magnetron sputtering processes allow the deposition of metals, alloys, ceramic, and polymer thin films onto a wide range of substrate materials. Within the frame of this work, the recent developments of reactive magnetron sputtering technique are presented. The development, fundamental principles and applications of the magnetron sputtering process are discussed and commented. At the same time, the paper presents few examples of the use of this technique to develop advanced coatings for industrial applications, including corrosion resistant coatings, hard ceramic coatings, and coatings with novel thermal and chemical properties

A time discretization scheme for a nonlocal degenerate problem modelling resistance spot welding

This is the author's PDF version of an article published in Mathematical Modelling of Natural Phenomena© 2015. The definitive version is available at http://www.mmnp-journal.org/articles/mmnp/abs/2015/06/mmnp2015106p90/mmnp2015106p90.htmlIn the current work we construct a nonlocal mathematical model describing the phase transition occurs during the resistance spot welding process in the industry of metallurgy. We then consider a time discretization scheme for solving the resulting nonlocal moving boundary problem. The scheme consists of solving at each time step a linear elliptic partial differential equation and then making a correction to account for the nonlinearity. The stability and error estimates of the developed scheme are investigated. Finally some numerical results are presented confirming the efficiency of the developed numerical algorithm

Thin films composed of Ag nanoclusters dispersed in TiO2: Influence of composition and thermal annealing on the microstructure and physical responses

Noble metal powders containing gold and silver have been used for many centuries, providing different colours in the windows of the medieval cathedrals and in ancient Roman glasses. Nowadays, the interest in nanocomposite materials containing noble nanoparticles embedded in dielectric matrices is related with their potential use for a wide range of advanced technological applications. They have been proposed for environmental and biological sensing, tailoring colour of functional coatings, or for surface enhanced Raman spectroscopy. Most of these applications rely on the so-called localised surface plasmon resonance absorption, which is governed by the type of the noble metal nanoparticles, their distribution, size and shape and as well as of the dielectric characteristics of the host matrix. The aim of this work is to study the influence of the composition and thermal annealing on the morphological and structural changes of thin films composed of Ag metal clusters embedded in a dielectric TiO2 matrix. Since changes in size, shape and distribution of the clusters are fundamental parameters for tailoring the properties of plasmonic materials, a set of films with different Ag concentrations was prepared. The optical properties and the thermal behaviour of the films were correlated with the structural and morphological changes promoted by annealing. The films were deposited by DC magnetron sputtering and in order to promote the clustering of the Ag nanoparticles the as-deposited samples were subjected to an in-air annealing protocol. It was demonstrated that the clustering of metallic Ag affects the optical response spectrum and the thermal behaviour of the films.This research was sponsored by FEDER funds through the COMPETE program (Programa Operacional Factores de Competitividade) and by FCT (Fundação para a Ciência e a Tecnologia), under the projects PEST-C/FIS/UI607/2013 and PEst-C/EME/UI0285/2013. The authors also acknowledge the financial support by the project Nano4color – Design and develop a new generation of color PVD coatings for decorative applications (FP7 EC R4SME Project No. 315286). J. Borges also acknowledges the support by the European social fund within the framework of realising the project “Support of inter-sectoral mobility and quality enhancement of research teams at Czech Technical University in Prague”, CZ.1.07/2.3.00/30.0034. C. Lopes acknowledges FCT for the PhD grant SFRH/BD/103373/2014. F.M. Couto acknowledges CAPES – Foundation, Ministry of Education of Brazil, Brasília – DF 70040-20, Brazil, funding by stage sandwich doctorate, through PDSE – Doctoral Program Sandwich