Approximating the coefficients in semilinear stochastic partial differential equations

We investigate, in the setting of UMD Banach spaces E, the continuous dependence on the data A, F, G and X_0 of mild solutions of semilinear stochastic evolution equations with multiplicative noise of the form dX(t) = [AX(t) + F(t,X(t))]dt + G(t,X(t))dW_H(t), X(0)=X_0, where W_H is a cylindrical Brownian motion on a Hilbert space H. We prove continuous dependence of the compensated solutions X(t)-e^{tA}X_0 in the norms L^p(\Omega;C^\lambda([0,T];E)) assuming that the approximating operators A_n are uniformly sectorial and converge to A in the strong resolvent sense, and that the approximating nonlinearities F_n and G_n are uniformly Lipschitz continuous in suitable norms and converge to F and G pointwise. Our results are applied to a class of semilinear parabolic SPDEs with finite-dimensional multiplicative noise.Comment: Referee's comments have been incorporate

Evolution of Landau Levels into Edge States at an Atomically Sharp Edge in Graphene

The quantum-Hall-effect (QHE) occurs in topologically-ordered states of two-dimensional (2d) electron-systems in which an insulating bulk-state coexists with protected 1d conducting edge-states. Owing to a unique topologically imposed edge-bulk correspondence these edge-states are endowed with universal properties such as fractionally-charged quasiparticles and interference-patterns, which make them indispensable components for QH-based quantum-computation and other applications. The precise edge-bulk correspondence, conjectured theoretically in the limit of sharp edges, is difficult to realize in conventional semiconductor-based electron systems where soft boundaries lead to edge-state reconstruction. Using scanning-tunneling microscopy and spectroscopy to follow the spatial evolution of bulk Landau-levels towards a zigzag edge of graphene supported above a graphite substrate we demonstrate that in this system it is possible to realize atomically sharp edges with no edge-state reconstruction. Our results single out graphene as a system where the edge-state structure can be controlled and the universal properties directly probed.Comment: 16 pages, 4 figure

A 2-D π–π dimer model system to investigate structure-charge transfer relationships in rubrene

© The Royal Society of Chemistry 2019Rubrene (5,6,11,12-tetraphenyltetracene) is undoubtedly one of the best performing organic charge transfer mediating materials, with experimentally determined mobilities up to 40 cm2 V−1 s−1. Consequently, there has been increasing interest by means of crystal engineering in trying to generate rubrene-based materials with analogous or even superior conducting properties. Often, experimental measurements are carried out in thin film architectures of these materials, where measured properties can be detrimentally impacted by device manufacture rather than intrinsic charge transfer properties of the material. The latter results in discarding potential good performers. To address these concerns, we report a two-dimensional model system that will allow researchers to predict charge transfer properties of their materials solely requiring the coordinates of the π–π stacking motifs. We envisaged this study to be of significant interest to the increasingly large community of materials scientists devoted to the realisation of improved organic charge mediating materials and particularly to those engaged in exploiting rubrene-based architectures.Peer reviewedFinal Accepted Versio

RACE-OC Project: Rotation and variability in young stellar associations within 100 pc

Our goal is to determine the rotational and magnetic-related activity properties of stars at different stages of evolution. We have focussed our attention on 6 young loose stellar associations within 100 pc and ages in the range 8-70 Myr: TW Hydrae (~8 Myr), beta Pictoris (~10 Myr), Tucana/Horologium, Columba, Carina (~30 Myr), and AB Doradus (~70 Myr). Additional data on alpha Persei and the Pleiades from the literature is also considered. Rotational periods of stars showing rotational modulation due to photospheric magnetic activity (i.e. starspots) have been determined applying the Lomb-Scargle periodogram technique to photometric time-series obtained by the All Sky Automated Survey (ASAS). The magnetic activity level has been derived from the amplitude of the V lightcurves. We detected the rotational modulation and measured the rotation periods of 93 stars for the first time, and confirmed the periods of 41 stars already known from the literature. For further 10 stars we revised the period determinations by other authors. The sample was augmented with periods of 21 additional stars retrieved from the literature. In this way, for the first time we were able to determine largest set of rotation periods at ages of ~8, ~10 and ~30 Myr, as well as increase by 150\% the number of known periodic members of AB Dor.The analysis of the rotation periods in young stellar associations, supplemented by Orion Nebula Cluster (ONC) and NGC2264 data from the literature, has allowed us to find that in the 0.6 - 1.2 solar masses range the most significant variations of the rotation period distribution are the spin-up between 9 and 30 Myr and the spin-down between 70 and 110 Myr. Variations between 30 and 70 Myr are rather doubtful, despite the median period indicates a significant spin-up.Comment: Accepted by Astronomy and Astrophysic

Stochastic evolution equations driven by Liouville fractional Brownian motion

Let H be a Hilbert space and E a Banach space. We set up a theory of stochastic integration of L(H,E)-valued functions with respect to H-cylindrical Liouville fractional Brownian motions (fBm) with arbitrary Hurst parameter in the interval (0,1). For Hurst parameters in (0,1/2) we show that a function F:(0,T)\to L(H,E) is stochastically integrable with respect to an H-cylindrical Liouville fBm if and only if it is stochastically integrable with respect to an H-cylindrical fBm with the same Hurst parameter. As an application we show that second-order parabolic SPDEs on bounded domains in \mathbb{R}^d, driven by space-time noise which is white in space and Liouville fractional in time with Hurst parameter in (d/4,1) admit mild solution which are H\"older continuous both and space.Comment: To appear in Czech. Math.

Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

The interaction of optical and mechanical modes in nanoscale optomechanical systems has been widely studied for applications ranging from sensing to quantum information science. Here, we develop a platform for cavity optomechanical circuits in which localized and interacting 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency field through the piezo-electric effect, or optically through the strong photoelastic effect. We use this to demonstrate a novel acoustic wave interference effect, analogous to coherent population trapping in atomic systems, in which the coherent mechanical motion induced by the electrical drive can be completely cancelled out by the optically-driven motion. The ability to manipulate cavity optomechanical systems with equal facility through either photonic or phononic channels enables new device and system architectures for signal transduction between the optical, electrical, and mechanical domains

Focal adhesion kinase contributes to proliferative potential of ErbB2 mammary tumour cells but is dispensable for ErbB2 mammary tumour induction in vivo

INTRODUCTION: Activation of focal adhesion kinase (FAK) is hypothesized to play an important role in the pathogenesis of human breast cancer. METHODS: To directly evaluate the role of FAK in mammary tumour progression, we have used a conditional FAK mouse model and mouse mammary tumour virus (MMTV)-driven Cre recombinase strain to inactivate FAK in the mammary epithelium of a transgenic mouse model of ErbB2 breast cancer. RESULTS: Although mammary epithelial disruption of FAK in this model resulted in both a delay in onset and a decrease in the number of neoplastic lesions, mammary tumours occurred in 100% of virgin female mice. All of the tumours and derived metastases that developed were proficient for FAK due to the absence of Cre recombinase expression. The hyperplastic epithelia where Cre-mediated recombination of FAK could be detected exhibited a profound proliferative defect. Consistent with these observations, disruption of FAK in established tumour cells resulted in reduced tumour growth that was associated with impaired proliferation. To avoid the selection for FAK-proficient ErbB2 tumour epithelia through escape of Cre-mediated recombination, we next intercrossed the FAK conditional mice with a separate MMTV-driven ErbB2 strain that co-expressed ErbB2 and Cre recombinase on the same transcriptional unit. CONCLUSIONS: While a delay in tumour induction was noted, FAK-deficient tumours arose in 100% of female animals indicating that FAK is dispensable for ErbB2 tumour initiation. In addition, the FAK-null ErbB2 tumours retained their metastatic potential. We further demonstrated that the FAK-related Pyk2 kinase is still expressed in these tumours and is associated with its downstream regulator p130Cas. These observations indicate that Pyk2 can functionally substitute for FAK in ErbB2 mammary tumour progression

RELAÇÃO CULTURAL DOS POVOS TRADICIONAIS INDÍGENAS COM O MEIO AMBIENTE E A SUSTENTABILIDADE

A partir de projetos de pesquisa e de pesquisa de campo, esse estudo foi realizado, tendo em vista a questão indígena e seus meios de se desenvolver de forma sustentável na biodiversidade das cidades e em meio à sociedade atual, tendo como órgãos de amparo aos direitos indígenas a FUNAI e a ONU. A comunidade indígena, desde os primórdios, tem uma forte relação com o meio ambiente, e é através do ambiente em que vivem que tiram sua subsistência, cultivando a terra e, assim também, a suas tradições, a fim de manter seus costumes, suas heranças, para as futuras gerações. A pesquisa abarca o Direito Ambiental, direito fundamental de terceira dimensão, transdisciplinar e ecocêntrico, relacionado diretamente com o meio ambiente e a questão da sustentabilidade indígena, nesse sentido esse trabalho buscará respostas para a questão da proteção ao índio, inclusive em plano aos Direitos Humanos, ao mesmo tempo em que reflete acerca da proteção ao meio ambiente, essencial para o século XXI

Entre flexibilização e precarização: Evoluções recentes no mercado de trabalho do Brasil contemporâneo

Este trabalho analisou os avanços da precariedade do mercado de trabalho no Brasil através da pesquisa documental. Com o surgimento e avanço do capitalismo no mundo as formas de trabalho foram modificadas no intuito de atender as demandas da produção de mercadorias para o acúmulo de capital. Fato importante do modo de produção capitalista é a evidente exploração do trabalho que desde seu surgimento restou caracterizada. De acordo com sua necessidade, este modo de produção se reestrutura com a finalidade de evitar a queda da taxa de lucro, e, em contrapartida remodela as formas de produção e as configurações do mercado de trabalho, intensificando a exploração do trabalhador. Nesta dissertação buscaremos entender como evoluiu a precariedade no mercado de trabalho no Brasil, e como se apresenta atualmente. Um aspeto evidenciado será a reestruturação produtiva sob a égide neoliberal ocorrida por volta de 1990 no contexto brasileiro, e as formas utilizadas pelo Estado para implementar as diretrizes do Consenso de Washington, imprescindíveis para dar novo rumo ao contexto económico no país sob os ditames neoliberais.This master’s dissertation the precariousness of the labor market in Brazil through documentary research. With the emergence and advance of capitalism in the world, the forms of work were modified in order to meet the demands of commodity production for the accumulation of capital. An important fact of the capitalist mode of production is the evident exploitation of labor, which has been characterized since its emergence. According to its needs, this mode of production restructures itself in order to avoid a fall in the profit rate, and, on the other hand, remodels the forms of production and the labor market configurations, intensifying the exploitation of the worker. In this dissertation, we will try to understand how precariousness has evolved in the labor market in Brazil, and how it presents itself today. One aspect that will be highlighted is the productive restructuring under the neoliberal aegis that occurred around 1990 in the Brazilian context, and the ways used by the State to implement the guidelines of the Washington Consensus, essential to give a new direction to the economic context in the country under the dictates of neoliberalism