Polaron relaxation in ferroelectric thin films

We report a dielectric relaxation in ferroelectric thin films of the ABO3 family. We have compared films of different compositions with several growth modes: sputtering (with and without magnetron) and sol-gel. The relaxation was observed at cryogenic temperature (T<100K) for frequencies from 100Hz up to 10MHz. This relaxation activation energy is always lower than 200meV. It is very similar to the polaron relaxation that we reported in the parent bulk perovskites. Being independent of the materials size, morphology and texture, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shapin

Treatment of toxoplasmosis: Current options and future perspectives

Toxoplasmosis is a worldwide parasitic disease infecting about one third of humans, with possible severe outcomes in neonates and immunocompromised patients. Despite continuous and successful efforts to improve diagnosis, therapeutic schemes have barely evolved since many years. This article aims at reviewing the main clinical trials and current treatment practices, and at addressing future perspectives in the light of ongoing researches

An exploration into identity formation in young people living with a chronic illness

Section A critically reviews relevant theoretical literature and empirical studies exploring the particular impact of chronic illness on identity formation in adolescents. Theoretical conceptualisations of the adolescent period and of the process of identity formation are explored. Following this, empirical literature regarding the impact of chronic illness on the developmental tasks of adolescence and in particular identify formation will be critically examined. A number of clinical implications are discussed to enable clinicians to effectively support young people and future research directions are outlined. Section B reports a narrative analysis of young people's experiences of forming an identity with a diagnosis of an adolescent-onset chronic illness (CI). Identity formation is argued to be one of the key developmental tasks of adolescence. Despite implications for adolescent development, research into CI onset during this period has been notably sparse. This study aimed to explore how diagnosis impacts on the developmental tasks of adolescence, what role adolescent-onset CI plays in identity formation, and how adolescents incorporate the diagnosis into their identity. Individual semi-structured interviews were carried out with 8 young people aged 14-19 who lived with a diagnosis of a CI diagnosed between the ages of 12-16 years. Two illness types were studied; crohn’s disease and juvenile idiopathic arthritis. Interviews were audio-recorded, transcribed and analysed using narrative analysis. Participant narratives contained five core narrative themes: Walking a different path, tolerating contradiction, a changed interface with others, locating power and a fluid relationship. Narratives were considered to have been influenced by factors such as the interview context and dominant social narratives concerning health and illness. Adolescent-onset CI was found to have a significant, though not exclusively negative, impact on developmental tasks. The findings are discussed in relation to existing literature and potential clinical implications. Section C critically appraises the narrative study. A discussion begins with reflections on the research skills developed and insights into the research process. Areas of further learning are identified. Implications of clinical practice are explored and the section concludes with considerations for further research in this area.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A test for a new modelling: The Univariate MT-STAR Model

In ESTAR models it is usually quite dicult to obtain parameter estimates, as it is discussed in the literature. The problem of properly distinguishing the transition function in relation to extreme parameter combinations often leads to getting strongly biased estimators. This paper proposes a new procedure to test for the unit root in a nonlinear framework, and contributes to the existing literature in three separate directions. First, we propose a new alternative model – the MT-STAR model – which has similar properties as the ESTAR model but reduces the eects of the identication problem and can also account for cases where the adjustment mechanism towards equilibrium is not symmetric. Second, we develop a testing procedure to detect the presence of a nonlinear stationary process by establishing the limiting non-standard asymptotic distributions of the proposed test-statistics. Finally, we perform Monte Carlo simulations to assess the small sample performance of the test and then to highlight its power gain over existing tests for a unit root

A Performance Measure of Zero-Dollar Long/Short Equally Weighted Portfolios

Sharpe-like ratios have been traditionally used to measure the performances of portfolio managers. However, they suer two intricate drawbacks (1) they are relative to a peer's performance and (2) the best score is generally assumed to correspond to a "good" portfolio allocation, with no guarantee on the goodness of this allocation. In this paper, we propose a new measure to quantify the goodness of an allocation and we show how to estimate this measure in the case of the strategy used to track the momentum eect, namely the Zero-Dollar Long/Short Equally Weighted (LSEW) investment strategy. Finally, we show how to use this measure to timely close the positions of an invested portfolio

Coulomb Blockade in low mobility nanometer size Si:MOSFETs

We investigate coherent transport in Si:MOSFETs with nominal gate lengths 50 to 100nm and various widths at very low temperature. Independent of the geometry, localized states appear when G=e^{2}/h and transport is dominated by resonant tunnelling through a single quantum dot formed by an impurity potential. We find that the typical size of the relevant impurity quantum dot is comparable to the channel length and that the periodicity of the observed Coulomb blockade oscillations is roughly inversely proportional to the channel length. The spectrum of resonances and the nonlinear I-V curves allow to measure the charging energy and the mean level energy spacing for electrons in the localized state. Furthermore, we find that in the dielectric regime, the variance var(lng) of the logarithmic conductance lng is proportional to its average value consistent with one-electron scaling models.Comment: 4 pages, 4 figure

Reactions at polymer interfaces: A Monte Carlo Simulation

Reactions at a strongly segregated interface of a symmetric binary polymer blend are investigated via Monte Carlo simulations. End functionalized homopolymers of different species interact at the interface instantaneously and irreversibly to form diblock copolymers. The simulations, in the framework of the bond fluctuation model, determine the time dependence of the copolymer production in the initial and intermediate time regime for small reactant concentration $\rho_0 R_g^3=0.163 ... 0.0406$. The results are compared to recent theories and simulation data of a simple reaction diffusion model. For the reactant concentration accessible in the simulation, no linear growth of the copolymer density is found in the initial regime, and a $\sqrt{t}$-law is observed in the intermediate stage.Comment: to appear in Macromolecule

Deforestation-driven food-web collapse linked to emerging tropical infectious disease, Mycobacterium ulcerans.

Generalist microorganisms are the agents of many emerging infectious diseases (EIDs), but their natural life cycles are difficult to predict due to the multiplicity of potential hosts and environmental reservoirs. Among 250 known human EIDs, many have been traced to tropical rain forests and specifically freshwater aquatic systems, which act as an interface between microbe-rich sediments or substrates and terrestrial habitats. Along with the rapid urbanization of developing countries, population encroachment, deforestation, and land-use modifications are expected to increase the risk of EID outbreaks. We show that the freshwater food-web collapse driven by land-use change has a nonlinear effect on the abundance of preferential hosts of a generalist bacterial pathogen, Mycobacterium ulcerans. This leads to an increase of the pathogen within systems at certain levels of environmental disturbance. The complex link between aquatic, terrestrial, and EID processes highlights the potential importance of species community composition and structure and species life history traits in disease risk estimation and mapping. Mechanisms such as the one shown here are also central in predicting how human-induced environmental change, for example, deforestation and changes in land use, may drive emergence