Manipulation of edge states in microwave artificial graphene

Edge states are one important ingredient to understand transport properties of graphene nanoribbons. We study experimentally the existence and the internal structure of edge states under uniaxial strain of the three main edges: zigzag, bearded, and armchair. The experiments are performed on artificial microwave graphene flakes, where the wavefunctions are obtained by direct imaging. We show that uniaxial strain can be used to manipulate the edge states: a single parameter controls their existence and their spatial extension into the ribbon. By combining tight-binding approach and topological arguments, we provide an accurate description of our experimental findings. A new type of zero-energy state appearing at the intersection of two edges, namely the corner state, is also observed and discussed.Comment: 15 pages, 9 figure

Tight-binding couplings in microwave artificial graphene

We experimentally study the propagation of microwaves in an artificial honeycomb lattice made of dielectric resonators. This evanescent propagation is well described by a tight-binding model, very much like the propagation of electrons in graphene. We measure the density of states, as well as the wave function associated with each eigenfrequency. By changing the distance between the resonators, it is possible to modulate the amplitude of next-(next-)nearest-neighbor hopping parameters and to study their effect on the density of states. The main effect is the density of states becoming dissymmetric and a shift of the energy of the Dirac points. We study the basic elements: An isolated resonator, a two-level system, and a square lattice. Our observations are in good agreement with analytical solutions for corresponding infinite lattice.Comment: 10 pages, 9 figure

Topological transition of Dirac points in a microwave experiment

By means of a microwave tight-binding analogue experiment of a graphene-like lattice, we observe a topological transition between a phase with a point-like band gap characteristic of massless Dirac fermions and a gapped phase. By applying a controlled anisotropy on the structure, we investigate the transition directly via density of states measurements. The wave function associated with each eigenvalue is mapped and reveals new states at the Dirac point, localized on the armchair edges. We find that with increasing anisotropy, these new states are more and more localized at the edges.Comment: Physical Review Letters (2013) XX

Release of TNF-α during myocardial reperfusion depends on oxidative stress and is prevented by mast cell stabilizers

Objectives: Our study sought to elucidate the role of oxidative stress for shedding of tumor necrosis factor-α (TNF-α) and for activating TNF-α-converting enzyme (TACE). Background: TNF-α, a central inflammatory cytokine, is discussed as one of the mediators of reperfusion injury. Shedding of membrane-bound pro-TNF-α is thought to be largely due to TNF-α-converting enzyme (TACE). Methods: Release of TNF-α and TACE dependency were studied in isolated rat hearts and in the human mast cell line HMC-1. Results: In reperfused hearts, interstitial release of TNF-α occurred in two phases (2–10 and >45 min). It depended on the presence of oxygen during reperfusion and was attenuated by reduced glutathione. Infusion of the oxidants H2O2 or HOCl elicited release in non-ischemic hearts. TNF-α release was inhibited in hearts treated with degranulation inhibitors ketotifen or cromoglycate, suggesting mast cells as major source for myocardial TNF-α. This was confirmed by tissue staining. Post-ischemic release of histamine, however, did not parallel that of TNF-α. Heart tissue contained mainly mature TACE. HMC-1 expressed abundant pro-TACE and cleaved the pro-TNF-α-peptide Ac-SPLAQAVRSSSR-NH2. However, cleavage was nonspecific and only partly inhibited by TACE inhibitor TAPI-2 (10–100 μmol/l), while it was stimulated by H2O2 and HOCl and fully blocked by the nonspecific metalloprotease inhibitor o-phenanthroline. Conclusions: The mechanism underlying TNF-α release from post-ischemic myocardium is oxidation-dependent but largely independent of activation of TACE. Mast cell stabilizers may be useful in preventing TNF-α release during reperfusion

A model of partial differential equations for HIV propagation in lymph nodes

Texto completo versión postprint de autor.-- PACS numbers: 02.30.Ks,02.30.Hq,87.18.Hf,87.19.XxA system of partial differential equations is used to model the dissemination of the Human Immunodeficiency Virus (HIV) in CD4+T cells within lymph nodes. Besides diffusion terms, the model also includes a time-delay dependence to describe the time lag required by the immunologic system to provide defenses to new virus strains. The resulting dynamics strongly depends on the properties of the invariant sets of the model, consisting of three fixed points related to the time independent and spatial homogeneous tissue configurations in healthy and infected states. A region in the parameter space is considered, for which the time dependence of the space averaged model variables follows the clinical pattern reported for infected patients: a short scale primary infection, followed by a long latency period of almost complete recovery and third phase characterized by damped oscillations around a value with large HIV counting. Depending on the value of the diffusion coefficient, the latency time increases with respect to that one obtained for the space homogeneous version of the model. It is found that same initial conditions lead to quite different spatial patterns, which depend strongly on the latency interval.This work was partially supported by the following Brazilian funding agencies: CAPES, FAPESB/PRONEX, CNPq and National Institute for Science and Technology/Complex Systems.Peer reviewe

Multilingual language resources and interoperability

This article introduces the topic of ‘‘Multilingual language resources and interoperability’’. We start with a taxonomy and parameters for classifying language resources. Later we provide examples and issues of interoperatability, and resource architectures to solve such issues. Finally we discuss aspects of linguistic formalisms and interoperability

Consistent high-precision volatility from high-frequency data

Estimates of daily volatility are investigated. Realized volatility can be computed from returns observed over time intervals of different sizes. For simple statistical reasons, volatility estimators based on high-frequency returns have been proposed, but such estimators are found to be strongly biased as compared to volatilities of daily returns. This bias originates from microstructure effects in the price formation. For foreign exchange, the relevant microstructure effect is the incoherent price formation, which leads to a strong negative first-order auto- correlation for tick-by-tick returns and to the volatility bias. On the basis of a simple theoretical model for foreign exchange data, the incoherent term can be filtered away from the tick-by-tick price series. With filtered prices, the daily volatility can be estimated using the information contained in high-frequency data, providing a high-precision measure of volatility at any time interval.volatility, high-frequency data, foreign exchange,

„Hauptsache, es schmeckt“ - der Einfluss von Jugendlichen auf den Öko-Lebensmittelkonsum in Familien

This contribution presents results of a qualitative study investigating juveniles’ influence in family decision-making with regard to organic food. According to recent research it can be assumed that expenditures for organic food in families with children decline as children grow older. For organic food marketing this raises the questions if, why and how juveniles influence family decision-making and what organic products are prefered or rejected? Semi-structured interviews were conducted with juveniles aged 13 to 18 years. The data was analysed using qualitative content analysis. Most juveniles proved to be open-minded towards organic food and they supported its consumption at home. Juveniles’ main criticism encompassed the taste of some organic product groups such as sweets, crisps, spreads and pizzas. If juveniles are not satisfied with the taste of an organic product they use different strategies to influence family purchase decisions. The main aim of these strategies is often to buy a conventional product. Therefore, organic suppliers should invest more money into researching juveniles’ specific taste preferences and should develop products which meet the expectations of juveniles better with respect to taste, but also regarding product appearance and packaging. Via advertising, product images should be optimised to comply with the actual lifestyle of the target group. Ethical aspects should also be included into communication strategies, as juveniles have a special sense for social justice and animal welfare

Health-related quality of life and associated factors after hip fracture. Results from a six-month prospective cohort study

Background: Hip fractures are a major public health problem with increasing relevance in aging societies. They are associated with high mortality rates, morbidity, and loss of independence. The aim of the EMAAge study was to determine the impact of hip fractures on patient-reported health-related quality of life (HRQOL), and to identify potential risk factors for worse outcomes. Methods: EMAAge is a multicenter, prospective cohort study of patients who suffered a hip fracture. Patients or, if necessary, proxies were interviewed after initial treatment and after six months using standardized questionnaires including the EQ-5D-5L instrument, the Oxford Hip Score, the PHQ-4, the Short Nutritional Assessment Questionnaire, and items on patients living situation. Medical data on diagnoses, comorbidities, medications, and hospital care were derived from hospital information systems. Results: A total of 326 patients were included. EQ-5D index values decreased from a mean of 0.70 at baseline to 0.63 at six months. The mean self-rated health on the EQ-VAS decreased from 69.9 to 59.4. Multivariable linear regression models revealed three relevant associated factors with the six-months EQ-5D index: symptoms of depression and anxiety, pre-fracture limitations in activities of daily living, and no referral to a rehabilitation facility had a negative impact. In addition, the six-months EQ-VAS was negatively associated with polypharmacy, living in a facility, and migration background. Conclusions: Hip fractures have a substantial negative impact on patients HRQOL. Our results suggest that there are modifying factors that need further investigation including polypharmacy and migration background. Structured and timely rehabilitation seems to be a protective factor