Computation of rare transitions in the barotropic quasi-geostrophic equations

We investigate the theoretical and numerical computation of rare transitions in simple geophysical turbulent models. We consider the barotropic quasi-geostrophic and two-dimensional Navier–Stokes equations in regimes where bistability between two coexisting large-scale attractors exist. By means of large deviations and instanton theory with the use of an Onsager–Machlup path integral formalism for the transition probability, we show how one can directly compute the most probable transition path between two coexisting attractors analytically in an equilibrium (Langevin) framework and numerically otherWe adapt a class of numerical optimization algorithms known as minimum action methods to simple geophysical turbulent models. We show that by numerically minimizing an appropriate action functional in a large deviation limit, one can predict the most likely transition path for a rare transition between two states. By considering examples where theoretical predictions can be made, we show that the minimum action method successfully predicts the most likely transition path. Finally, we discuss the application and extension of such numerical optimization schemes to the computation of rare transitions observed in direct numerical simulations and experiments and to other, more complex, turbulent systems.

Langevin dynamics, large deviations and instantons for the quasi-geostrophic model and two-dimensional Euler equations

We investigate a class of simple models for Langevin dynamics of turbulent flows, including the one-layer quasi-geostrophic equation and the two-dimensional Euler equations. Starting from a path integral representation of the transition probability, we compute the most probable fluctuation paths from one attractor to any state within its basin of attraction. We prove that such fluctuation paths are the time reversed trajectories of the relaxation paths for a corresponding dual dynamics, which are also within the framework of quasi-geostrophic Langevin dynamics. Cases with or without detailed balance are studied. We discuss a specific example for which the stationary measure displays either a second order (continuous) or a first order (discontinuous) phase transition and a tricritical point. In situations where a first order phase transition is observed, the dynamics are bistable. Then, the transition paths between two coexisting attractors are instantons (fluctuation paths from an attractor to a saddle), which are related to the relaxation paths of the corresponding dual dynamics. For this example, we show how one can analytically determine the instantons and compute the transition probabilities for rare transitions between two attractors.

Resonance properties of domain boundaries in quasi-two dimensional antiferromagnets

The so-called "internal modes" localized near the domain boundaries in quasi-two dimensional antiferromagnets are investigated. The possible localized states are classified and their frequency dependences on the system discreteness parameter λ=J/β, which describes the ratio of the magnitudes of the exchange interplane interaction and the magnetic anisotropy, are found. A sudden change in the spectrum of the local internal modes is observed at a critical value of this parameter, λ=λb=3/4, where the domain wall shifts from a collinear to a canted shape. When λ<λb there are one symmetric and two antisymmetric local modes, and when λ>λb the modes are two symmetric, one antisymmetric, and one shear. For discreteness parameters close to the critical value, the frequencies of some of the local modes lie deep inside the gap for the linear AFM magnon spectrum and can be observed experimentally. © 2010 American Institute of Physics.

Hálózat – A globális gazdaság kvázi szervezete (The business network – the quasi organization of the global economy)

A tanulmány célja, hogy értelmezze a globális gazdaság alapvető fontosságú építőelemét, az üzleti hálózatot, majd megvizsgálja annak felépítését és működésének főbb vezérlőelveit. Először az alapfogalmak – üzleti hálózat, ellátási lánc és ellátási háló – meghatározására és azok felépítésének bemutatására kerül sor. Ezt követően a cikk röviden ismerteti, hogy melyek voltak azok a vállalati gazdálkodás környezetében végbement változások, melyek a gazdaság hálózatosodását elősegítették és ennek kapcsán elvezettek az üzleti hálózatok versenyképességben játszott szerepének erősödéséhez. A szerző ugyanakkor bemutatja a kialakuló új gazdasági modell, az ún. hálózati gazdaság működési modelljének lényeges új tulajdonságait. A tanulmány ezután ismerteti az üzleti hálózat – s ezen belül az ellátási lánc – működtetésében meghatározó koordinációs mechanizmusokban megfigyelhető markáns változásokat. Végül részletesen ismerteti az üzleti hálózat két fő építőelemét: a hálózatot alkotó üzleti egységeknek, illetve a közöttük kialakuló kapcsolatoknak az alapvető típusait. ________ The aim of the paper is to present and interpret the basic building element of global business: the business network, its structure and operation. First basic terms – network, supply chain, supply network – are defined and described, than those changes are introduced that played significant role in increasing their importance. Characteristics of the new network economy are presented; especially changes in the coordination mechanism between cooperating parties in the network are demonstrated. Finally the two building blocks of global business networks: (i) nodes (business units) and (ii) threads (partnerships) are described in details.

A kvázi- és általánosított hiperbolikus diszkontálás hosszú távon (Quasi- and Generalized Hyperbolic Discounting in Long Term)

Az intertemporális döntések fontos szerepet játszanak a közgazdasági modellezésben, és azt írják le, hogy milyen átváltást alkalmazunk két különböző időpont között. A közgazdasági modellezésben az exponenciális diszkontálás a legelterjedtebb, annak ellenére, hogy az empirikus vizsgálatok alapján gyenge a magyarázó ereje. A gazdaságpszichológiában elterjedt általánosított hiperbolikus diszkontálás viszont nagyon nehezen alkalmazható közgazdasági modellezési célra. Így tudott gyorsan elterjedni a kvázi-hiperbolikus diszkontálási modell, amelyik úgy ragadja meg a főbb pszichológiai jelenségeket, hogy kezelhető marad a modellezés során. A cikkben azt állítjuk, hogy hibás az a megközelítés, hogy hosszú távú döntések esetén, főleg sorozatok esetén helyettesíthető a két hiperbolikus diszkontálás egymással. Így a hosszú távú kérdéseknél érdemes felülvizsgálni a kvázi-hiperbolikus diszkontálással kapott eredményeket, ha azok az általánosított hiperbolikus diszkontálási modellel való helyettesíthetőséget feltételezték. ____ Intertemporal choice is one of the crucial questions in economic modeling and it describes decisions which require trade-offs among outcomes occurring in different points in time. In economic modeling the exponential discounting is the most well known, however it has weak validity in empirical studies. Although according to psychologists generalized hyperbolic discounting has the strongest descriptive validity it is very complex and hard to use in economic models. In response to this challenge quasi-hyperbolic discounting was proposed. It has the most important properties of generalized hyperbolic discounting while tractability remains in analytical modeling. Therefore it is common to substitute generalized hyperbolic discounting with quasi-hyperbolic discounting. This paper argues that the substitution of these two models leads to different conclusions in long term decisions especially in the case of series; hence all the models that use quasi-hyperbolic discounting for long term decisions should be revised if they states that generalized hyperbolic discounting model would have the same conclusion.

Responsiveness of voltage-gated calcium channels in SH-SY5Y human neuroblastoma cells on quasi-three-dimensional micropatterns formed with poly (l-lactic acid)

Introduction: In this study, quasi-three-dimensional (3D) microwell patterns were fabricated with poly (l-lactic acid) for the development of cell-based assays, targeting voltage-gated calcium channels (VGCCs). Methods and materials: SH-SY5Y human neuroblastoma cells were interfaced with the microwell patterns and found to grow as two dimensional (2D), 3D, and near two dimensional (N2D), categorized on the basis of the cells’ location in the pattern. The capability of the microwell patterns to support 3D cell growth was evaluated in terms of the percentage of the cells in each growth category. Cell spreading was analyzed in terms of projection areas under light microscopy. SH-SY5Y cells’ VGCC responsiveness was evaluated with confocal microscopy and a calcium fluorescent indicator, Calcium GreenTM-1. The expression of L-type calcium channels was evaluated using immunofluorescence staining with DM-BODIPY. Results: It was found that cells within the microwells, either N2D or 3D, showed more rounded shapes and less projection areas than 2D cells on flat poly (l-lactic acid) substrates. Also, cells in microwells showed a significantly lower VGCC responsiveness than cells on flat substrates, in terms of both response magnitudes and percentages of responsive cells, upon depolarization with 50 mM K+. This lower VGCC responsiveness could not be explained by the difference in L-type calcium channel expression. For the two patterns addressed in this study, N2D cells consistently exhibited an intermediate value of either projection areas or VGCC responsiveness between those for 2D and 3D cells, suggesting a correlative relation between cell morphology and VGCC responsiveness. Conclusion: These results suggest that the pattern structure and therefore the cell growth characteristics were critical factors in determining cell VGCC responsiveness and thus provide an approach for engineering cell functionality in cell-based assay systems and tissue engineering scaffolds.

Quasi-Orthogonal Space-Time Block Coding Using Polynomial Phase Modulation

Recently, polynomial phase modulation (PPM) was shown to be a power- and bandwidth-efficient modulation format. These two characteristics are in high demand nowadays specially in mobile applications, where devices with size, weight, and power (SWaP) constraints are common. In this paper, we propose implementing a full-diversity quasiorthogonal space-time block code (QOSTBC) using polynomial phase signals as modulation format. QOSTBCs along with PPM are used in order to improve the power efficiency of communication systems with four transmit antennas. We obtain the optimal PPM constellations that ensure full diversity and maximize the QOSTBC's minimum coding gain distance. Simulation results show that by using QOSTBCs along with a properly selected PPM constellation, full diversity in flat fading channels and thus low BER at high signal-to-noise ratios (SNR) can be ensured. More importantly, it is also shown that QOSTBCs using PPM achieve a better error performance than those using conventional modulation formats.

As marcas culturais das festas populares no fotojornalismo dos periódicos Correio da Manhã e Tribuna do Norte

This research is about the cultural marks and meanings production on the popular culture context, in honor of Catholics Saints of June: Saint Antony; Saint John and Saint Peter (with celebrations in June 13th, 24th and 30th respectively). These marks are find on the newspapers’ photography of Tribuna do Norte (Natal, Rio Grande do Norte, Brazil) and Correio da Manhã (Lisbon, Portugal). All the photos were published in June 2012. The analysis has theory and methodology in Folkcommunication and in Sociocultural Photocatography. The investigation has focus in the meanings of these marks on the photojournalism about the popular parties and their practices. The study observes also a common view to report about popular culture, which has the influence of a hegemonic paradigm that considers itself the only true one.

Quintosana e seus derivados conjugados com ácido gálico: avaliação de seu potencial antioxidante e de interferência na formação de cristais de oxalato de cálcio

Chitin is the second most abundant polysaccharide in nature and its derivative chitosan has been widely studied due to its unique chemical and pharmacological properties. However, studies show that when this molecule is used as food, drug, etc. it tends to accumulate in renal tissue and promotes an increase in calcium excretion. Nevertheless, the effect of chitosan on the formation of calcium oxalate (OxCa) crystals has never been evaluated. The formation of kidney stones (urolithiasis) is the disease that most often affects the kidneys and the urinary system. In addition, this is a disease with high prevalence and recurrence. Many molecules with antioxidant activity have been shown to decrease the potential for in vitro OxCa crystals formation. Thus, the aim of this study was to evaluate the effect of low molecular weight chitosan and its derivatives conjugated to gallic acid (AG) as antioxidant and inhibitor of OxCa crystals formation. The physico-chemical analysis confirmed the identity of chitosan. This molecule was subjected to five antioxidant tests and showed an excellent copper chelating activity. However, chitosan did not show other significant antioxidant activity. When chitosan was subjected to in vitro crystal formation tests, it increased the number of OxCa monohydrate crystals, modified the morphology of the crystals, modified the proportions between populations of crystals in solution and increased the zeta potential of these crystals formed. Four molecules of chitosan conjugated with GA were obtained. The physico-chemical analysis confirmed that chitosan and AG were covalently bonded. However, the amount of GA liked to chitosan did not increase even when 10 times more GA was used in experiment. When these derivatives were subjected to antioxidant tests, all chitosan conjugates showed higher antioxidant potential than their precursors. However, they showed different activity between them, which indicating that the position where AG is conjugated is an important factor for chitosan-GA activity. When conjugated chitosans were submitted to in vitro crystal formation tests, a reduction in the crystals number was observed when compared with those formed in the presence of unconjugated chitosan. Chitosan has a strong capacity for inducing OxCa monohydrate crystal formation, as well as modify their morphology and zeta potential. Over all, the process of conjugating AG to chitosan led to an increase in antioxidant potential of this molecule and was also able to decrease its capacity of inducing in vitro crystal formation

Caracterização de superfícies seletivas de frequência de periódicas e não-periódicas

The past years have seen a great interest in the use of frequency selective surfaces (FSS), as spatial filters, in many microwave applications. Among these, we highlight applications in telecommunication systems (such as satellite communications and radar), high gain antennas (combined with planar antennas) and (home and industrial) microwave ovens. The FSS is usually composed of two-dimensional periodic arrays, with equally spaced elements, which may be metallic patches (printed on dielectric substrates) or aperture (holes in thin metal surfaces). Using periodic arrays, the FSS have been able to meet the demands of the telecommunications industry. However, new demands are finding technological limitations. In this context, adverse filtering requirements have forced designers to use FSS optimization methods to find specific formats of FSS elements. Another alternative that has been used to increase the selectivity of the FSS is the cascaded FSS, a simple technique that has as main drawback the increased dimensions of the structure, as well as its weight. This work proposes the development of a new class of selective surfaces frequency (FSS) composed of quasi-periodic (or non-periodic) arrangements. The proposed FSS have no array periodicity, in relation with the spatial position of their elements. The frequency responses of these structures were simulated using commercial softwares that implement full-wave methods. For the purpose of validation of this study, FSS prototypes were built and measured, being possible to observe a good agreement between simulated and measured results. The main conclusions of this work are presented, as well as suggestions for future works.

Análise do uso do Portal de Periódicos da CAPES na perspectiva de mestres e doutores formados pelo Programa de Pós-graduação em Administração da UFRN

The Brazilian CAPES Journal Portal aims to provide Information in Science and Technology (IST) for academic users. Thus, it is considered a relevant instrument for post-graduation dynamics and the country´s Science and Technology (S&T) development. Despite its importance, there are still few studies that focus on the policy analysis and efficiency of these resources. This research aims to fill in this gap once it proposes an analysis of the use of the CAPES Journal Portal done on behalf of the master´s and doctoral alumni of the Post Graduate Program in Management (PPGA) at the Federal University of Rio Grande do Norte (UFRN). The operationalization of the research´s main objective was possible through the specific objectives: characterize graduate profile as CAPES Journal Portal users b) identify motivation for the use of CAPES Journal Portal c) detect graduate satisfaction degree in information seeking done at CAPES Journal Portal d) verify graduate satisfaction regarding the use of the CAPES Journal Portal e) verify the use of the information that is obtained by graduates in the development of their academic activities. The research is of descriptive nature employing a mixed methodological strategy in which quantitative approach predominates. Data collection was done through a web survey questionnaire. Quantitative data analysis was made possible through the use of a statistical method. As for qualitative analysis, there was use of the Brenda Dervin´s sense-making approach as well as content analysis in open ended questions. The research samples were composed by 90 graduate students who had defended their dissertation/thesis in the PPGA program at UFRN in the time span of 2010-2013. This represented by 88% of this population. As for user profile, the analysis has made evident that there are no quantitative differences related to gender. There is predominance of male graduates that were aged 26 to 30 years old. As for female graduates, the great majority were 31 o 35 years old. Most graduates had Master´s degree scholarship in order to support their study. It was also seen that the great majority claim to use the Portal during their post graduation studies. The main reasons responsible for non use was: preference for the use of other data bases and lack of knowledge regarding the Portal. It was observed that the most used information resources were theses and dissertations. Data also indicate preference for complete text. Those who have used the Portal also claimed to have used other electronic information fonts in order to fulfill their information needs. The information fonts that were researched outside in the Portal were monographs, dissertations and thesis. Scielo was the most used information font. Results reveal that access and use of the Portal has been done in a regular manner during post graduation studies. But on the other hand, graduates also make use of other electronic information fonts in order to meet their information needs. The study also confirmed the important mission performed by the Portal regarding Brazilian scientific communication production. This was seen even though users have reported the need for improvement in some aspects such as: periodic training in order to promote, encourage and teach more effective use of the portal; investment aiming the expansion of Social Sciences Collection in the Portal as well as the need to implement continuous evaluation process related to user satisfaction in regarding the services provided.

Distribuzioni di quasi-probabilità: la funzione di Wigner

L'elaborato fornisce una introduzione alla funzione di Wigner, ovvero una funzione di fase che gioca un ruolo chiave in alcuni ambiti della fisica come l'ottica quantistica. Nel primo capitolo viene sviluppato sommariamente l'apparato matematico-fisico della quantizzazione di Weyl e quindi introdotta l'omonima mappa di quantizzazione tra funzioni di fase ed operatori quantistici. Nella seconda parte si delinea la nozione di distribuzione di quasi-probabilit\`a e si danno alcune importanti esemplificazioni della funzione di Wigner per gli autostati dell'oscillatore armonico. Per finire l'ultimo capitolo tratteggia il panorama sperimentale all'interno del quale la funzione di Wigner viene utilizzata.

Study of Periodic and Quasi-Periodic Structures in Silicon-on-Insulator

In this thesis, a numerical design approach has been proposed and developed based on the transmission matrix method in order to characterize periodic and quasi-periodic photonic structures in silicon-on-insulator. The approach and its performance have been extensively tested with specific structures in 2D and its validity has been verified in 3D.

Contribution à l'évaluation de l'équilibre quasi-statique à l'aide d'une plate-forme de force

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Contribution à l'évaluation de l'équilibre quasi-statique à l'aide d'une plate-forme de force

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.