Nosso objetivo é reunir estudantes e cientistas interessados para discutir sobre temas relevantes na física de partículas, cosmologia e astrofísica de partículas. Todos estão convidados a participar nas reuniões, mas leia o artigo com antecedência, para que você possa acompanhar a discussão.
O artigo escolhido para próxima discussão pode ser acessado no endereço eletrônico http://arxiv.org/abs/1501.05932
The field of organic semiconductors has grown rapidly providing complementary options to inorganic semiconductors, such as flexibility and large-area application. Although organic transistors are slow compared to Si transistors, they have been of particular interest largely due to their ease of fabrication and compatibility with other electronic components; they form the building block of modern organic displays.
The dynamic coupling of charge carriers to the electronic polarization at the semiconductor-dielectric interface results in a renormalization of the transfer integral for the transport process. Ferroelectric dielectrics, permitting access to nearly an order of magnitude range of dielectric constants with temperature as the tuning parameter, offer a great platform to monitor the changes in interfacial transport in organic field-effect transistors (FETs) as the polarization strength is tuned. In this talk I will present our recent results on ferroelectric-based pentacene FETs. The weak temperature-dependence of the charge carrier mobility in the ferroelectric phase of the dielectric may be attributed to a polarization fluctuation driven transport. By comparing single dielectric layer FETs with stacked ferroelectric/inorganic dielectric FETs, the contribution from Fröhlich polarons is extracted. The temperature-dependent mobility of the polarons increases with the thickness of the ferroelectric layer. Using a strongly coupled polaron model, the hopping lengths were determined to vary between 2Å – 5Å.
Apresentaremos métodos analíticos que permitem obter o espectro de partículas da QCD na rede rigorosamente, entre outros modelos de interesse na Física. Vamos nos concentrar na obtenção das curvas de dispersão de um bárion, no espectro de energia-momento. Mencionaremos também, rapidamente, alguns resultados que temos para o espectro de estados ligados de dois bárions, dois mésons e bárion-méson. Concluiremos tecendo relações entre a determinação do espectro e o confinamento.
The ability to control electron spin degrees of freedom at the nanoscale is one of the crucial challenges in nanoscience both from fundamental and technological points of view. The scope of this talk is to show the capability of density-functional based methods to reproduce the properties of magnetic molecules in the gas phase, and to investigate the mechanisms through which magnetic coupling of a molecular spin with magnetic substrates can be achieved. More specifically, we have analyzed the magnetic coupling in heterometallic supramolecular dimers, i.e.purple-Cr7M/pyr/green-Cr7M’, by systematic variations of the M, M’magnetic ions, M, M’= Ni, Zn and Mn, and discussed the results in terms of the different exchange paths through the pyridine (pyr) linker. We have also addressed the case of a cobaltocene molecule adsorbed on graphene/ferromagnetic metal surfaces (e.g. Ni(111), and Fe or Co monolayers on Ni(111)), emphasizing the role of graphene in electronically decoupling the molecule from the metal substrates [1], while, on the other hand, allowing and mediating the exchange coupling between the molecular spin and the ferromagnetic layers below. Depending on the periodicity of the system (zero-dimensional for isolated molecules or three-dimensional for molecules on surface) under interest, codes employing localized gaussian (NWChem) or plane waves (VASP) basis set were used, respectively.
[1] S. Marocchi, P. Ferriani, NM Caffrey, F. Manghi, S. Heinze, V.Bellini, Physical Review B 88, 144407 (2013).
O conceito de sistema na música enquanto systema teleion (conjunto harmônico de relações articuladas) remonta a Aristóxeno (século IV a. C.), fundador da musicologia moderna. Durante a Antiguidade, Idade Média e Renascimento, em fontes gregas e latinas, o conceito de sistema se restringiu à música (mesmo em Copernico o conceito é inexistente). Com Kepler (1609) e Galileu (1610) – ambos com formação musical – o conceito de sistema num processo metafórico é adotado pela primeira vez fora da música. Além da trajetória cronológica do conceito, a palestra contempla a discussão histórico-filosófica desde Aristóxeno até Galileu (sistema máximo e perfeito, tradução literal de Aristóxeno), justamente na transposição do conceito musical para as ciências, bem como das lacunas na história das ciências até aqui sobre este processo.
III-V nanowires support optical resonant modes such that nanowires act as very 
effective waveguides that concentrate and absorb light over a length of only a few microns, enabling very efficient photodetectors and solar cells with relatively little material.
It is also of great interest to develop multi-spectral or wavelength discriminating infrared detectors or cameras for advanced infrared imaging systems with enhanced target discrimination and identification, providing improved discrimination of absolute temperature as well as unique signatures of objects.
The resonant absorption in nanowires shows wavelength selectivity that can be tuned continuously across the visible and infrared wavelengths by adjusting the nanowire diameter. This principle can be used as a new concept for multi-spectral imaging.
Lattice-mismatched III-V nanowires can also be grown directly on Si substrates enabling integration with existing Si CCD sensors, CMOS sensors, or Si solar cell technology. These capabilities enable large-area, low cost infrared sensors with multi-spectral capability integrated into existing Si technology, and enhancement of Si solar cell efficiency.
The theory and preliminary experimental results for III-V nanowires and their potential in wavelength tunable infrared cameras and solar cells will be presented.
(Transmissão via iptv.usp.br)
Even though there is a wide range of numerical methods to treat partial differential equations (PDEs), our interests lie in those which render highly accurate solutions, ideally close to machine precision. In this context, pseudo-spectral methods are probably the best choice, as they have the remarkable capability of providing exponential convergence rate when the underlying problem admits a regular solution. Therefore, the aim of this talk is to give an introductory discussion to such spectral-methods applied to some problems in classical field theories. I shall first concentrate on examples concerning PDEs restricted to spatial coordinates (typically elliptic equations), a field where spectral methods find their most common application. Then I will discuss our efforts to further extend those methods to the realm of hyperbolic equations, where a spectral approximation is also considered in the time direction.
We´ll discuss the symmetry approach to integrability of partial differential equations with two independet variables. Main definitions are given and examples have been considered. A classification of integrable equations of the Korteweg-de Vries type is presented. We show that some special classes of integrable polynomial multi-component models are closely related to Jordan and left-symmetric algebras and to Jordan triple systems.
The Kerr metric of vacuum general relativity is expected to describe astrophysical black holes. Boson stars, on the other hand, are one of the simplest gravitating solitons, suggested as astrophysical compact objects, black holes mimickers and as dark matter candidates. Kerr black holes with scalar hair, found in [1], continuously interpolate between these two types of, per se, physically interesting solutions. I will describe the construction of these solutions and discuss theoretical, astrophysical and high energy physics aspects and challenges for Kerr black holes with scalar hair.
References: [1] Kerr black holes with scalar hair, Carlos A. R. Herdeiro, Eugen Radu, Phys. Rev. Lett. 112 (2014) 221101; e-Print: arXiv:1403.2757
Intrinsic spin-orbit coupling in graphene is relatively weak, some tens of micro eVs [1-3]. On one hand, this is nice, as the projected intrinsic spin relaxation is also slow, on the order of microseconds. On the other hand, a greater value for the spin-orbit interaction is desired for spin manipulation and spin-orbit induced phenomena, such as the (quantum) spin Hall effect. In this talk I will review basics of the spin-orbit physics in graphene and show how to effectively increase the value of the spin-orbit interaction by adding adatoms [3]. Examples will be hydrogen, fluorine, and copper adatoms. I will present our first-principles results as well as phenomenological model Hamiltonians which should be useful to study model spin transport and spin relaxation. I will also discuss the spin relaxation problem in graphene: experiments get the spin relaxation times of 100 ps, orders of magnitude below what is theoretically expected [4]. The cause appears to be extrinsic, due to impurities. I will argue that the mechanism is resonant scattering by a small concentration of magnetic moments (wherever they come from) [5].
[1] M. Gmitra, S. Konschuh, C. Ertler, C. Ambrosch-Draxl, and J. Fabian, Phys. Rev. B 80, 235431 (2009).
[2] S. Konschuh, M. Gmitra, and J. Fabian, Phys. Rev. B 82, 245412 (2010).
[3] M. Gmitra, D. Kochan, and J. Fabian, Phys. Rev. Lett. 110, 246602 (2013).
[4] W. Han, R. Kawakami, M. Gmitra, and J. Fabian, Nature Nanotechnology 9, 794 (2014)
[5] D. Kochan, M. Gmitra, and J. Fabian, Phys. Rev. Lett. 112, 116602 (2014).
That composition and structure profoundly impact the properties of crystalline solids has provided impetus for exponential growth in the field of crystal engineering over the past 20 years. This lecture will address how crystal engineering has evolved from structure design (form) to control over bulk properties (function). Strategies for the generation of two classes of functional crystalline materials will be addressed: Multicomponent pharmaceutical materials, MPMs, such as cocrystals have emerged as a fixture at the preformulation stage of drug development. This results from their modular and designable nature which facilitates the discovery of a wide range of new crystal forms of active pharmaceutical ingredients, APIs, with changed physicochemical properties. However, this does not mean that cocrystal discovery is yet routine. The concepts of “supramolecular heterosynthons” and “ionic cocrystals” will be explained as they pertain to the design of MPMs. We shall address the profound impact that cocrystallization can have upon solubility and bioavailability by presenting three case studies including one that addresses brain bioavailability of lithium.
Metal-Organic Materials (MOMs) that are built from metal or metal cluster “nodes” and organic “linkers” have captured the imagination of materials scientists because they are amenable to crystal engineering and they offer unprecedented levels of porosity. A familyof MOMs,pillared grids, that afford exceptional control over composition, pore size and binding energy,will be detailed. Unprecedented selectivity for carbon capture in narrow pore MOMs will be highlighted. In summary, this lecture will emphasize how the crystal engineering approach to materials design offers a paradigm shift from the more random, high-throughput methods that have traditionally been utilized in materials discovery and development with respect to pharmaceutical materials and porous materials. In short, how do we make the right material for the right application?
Um objeto pode, em princípio, se tornar invisível pela distorção dos raios de luz em sua volta, devido à introdução de uma variação espacial específica de alguns parâmetros constitutivos do meio ao seu redor. Esta ideia de “manto de invisibilidade” foi aplicada recentemente ao fluxo térmico em camadas concêntricas de um metamaterial com constante de difusão isotrópica por partes. Um manto térmico implica que a região protegida tem sua temperatura reduzida enquanto que um concentrador térmico foca o fluxo de calor numa dada região. O modelo para propagação acústica baseado em geometria não-euclidiana fornece o ambiente apropriado para estudarmos a possibilidade de se obter invisibilidade/concentração térmica em cristais líquidos nemáticos, devido à sua anisotropia inerente. Nós mostramos que a geometria não-trivial associada ao meio anisotrópico influencia a propagação de fônons em um paralelo com a propagação de fótons no âmbito da Relatividade Geral.
Em outras palavras, a condutividade térmica do meio é diretamente relacionada com a configuração específica do campo diretor (orientação média das moléculas do líquido), que determina a geometria efetiva de uma dada amostra nemática. As trajetórias dos fônons próximas e em torno de defeitos topológicos como declinações sugerem configurações do campo diretor que podem simular um manto ou um concentrador térmico. Nossas simulações para estas configurações indicam a possibilidade de construção de dispositivos térmicos com estas propriedades. REFERENCIA: Phys. Rev. E 89 (2014) 020501.
A proposta do programa é reunir estudantes e cientistas interessados para discutir temas relevantes na física de partículas, cosmologia e astrofísica de partículas.
Todos estão convidados a participar das reuniões, mas se recomenda a leitura do artigo com antecedência, para que se possa acompanhar a discussão.
Para saber qual artigo será discutido, clique aqui.
The discovery of the Higgs boson at the LHC completes the Standard Model (SM). Otherwise, we know that this is not the end as Dark Matter, neutrino masses and other issues stay without an explanation. The physics Beyond Standard Model becomes a necessity and there are a lot of models on the market, so how to make sure that we are not missing any signal of new physics? The effective field theory (EFT) permits a model independent approach that makes it possible to translate the analysis to any model. I will discuss what is an EFT and latter, apply the analysis to a recent measurement of lepton flavor violating Higgs decays.
Nesta palestra, o Prof. Ulisses Thibes Mello irá discutir a história da instalação do Centro 
de Pesquisas da IBM no Brasil, nesses últimos cinco anos, como também irá descrever as áreas-foco do laboratório (recursos naturais, computação cognitiva, sistemas de engajamento e tecnologias industriais).
O palestrante descreverá, também – e de forma breve -, os principais projetos da IBM nessas áreas (eg., inversão sísmica, análise de dados de media social, otimização estocástica aplicada à mineração, bem como nanotecnologia aplicada à recuperação de hidrocarbonetos).
A palestra cobrirá, ainda, modelos de colaboração com empresas e universidades e será transmitida pela IPTV.
Assessoria de Comunicação
Na palestra será discutida a história da instalação do centro de pesquisas da IBM no Brasil nesses últimos cinco anos como também serão descritas as áreas foco do laboratório (recursos naturais, computação cognitiva, sistemas de engajamento, e tecnologias industriais). Serão descritos brevemente os principais projetos nessas áreas (eg., inversão sísmica, analise de dados de media social, otimização estocástica aplicada a mineração, e nanotecnologia aplicada a recuperação de hidrocarbonetos). Também serão cobertos modelos de colaboração com empresas e universidades.
Initially in this talk, the fabrication of an all-printed and flexible biosensor for antioxidants will be described in order to illustrate the techniques and approaches explored by our group in the field of printed bioelectronics [1]. The research work comprised the following steps: i) formulation of an enzyme-containing bioink with both good printability in the large-area, roll-to-roll (R2R) compatible, rotogravure printing method, and preserved catalytic activity after printing; ii) deposition of sub-100 µm Au interdigitated electrodes by inkjet printing; iii) deposition of large-area, patterned, bioactive films onto flexible substrates (PET and PEN); iv) testing of the all-printed device in electrical impedance biosensing. In a second moment, results from two other projects will be discussed. The first project comprises the fabrication of flexible inkjet-printed Au circuits that were used as a biomedical device for the early detection of pressure ulcers on skin [2]. The second project is a current initiative from our group in which electronic components (printed resistor, capacitor and transistor) are being deposited exclusively by inkjet-printing. These components will be further combined to build more complex devices as inverters and (in the long-term) all-printed, low-cost, RFID tags. In general, the aim of the presentation is to illustrate capabilities and interest from the Bernhard Gross Polymer Group in the area of Printed (Bio)Electronics.
References
[1] PAVINATTO, F. J.; PASCHOAL, C. W. A.; ARIAS, A. C. Printed and flexible biosensor for antioxidants using interdigitated ink-jetted electrodes and gravure-deposited active layer. Biosensors and Bioelectronics, v. 67, p. 553-559, 2015.
[2] SWISHER, S. L, LIN, M. C.; LIAO, A.; LEEFLANG, E. J.; KHAN, Y.; PAVINATTO, F. J.; MANN, K.; NAUJOKAS, A.; YOUNG, D.; ROY, S.; HARRISON, M. R.; ARIAS, A. C.; SUBRAMANIAN, V.; MAHARBIZ, M. Impedance sensing device enables early detection of pressure ulcers in vivo. Nature Communications, Accepted for Publication, 2015.
Nanoscale science and technology has the potential to transform processes involving liquids in various industries. However, a combination of suitable experimental techniques and computational methods is needed in order to reveal the fundamentals of surface wetting phenomena at the nanoscale. Specifically, the understanding of liquid-solid interaction at the nanoscale is hoped to improve existing oil reservoir models up to the macroscale with potential benefits for enhanced oil recovery.
In this seminar, I will present results obtained with a novel measurement platform that enables the nanoscale characterization of tiny amounts of liquids having volumes of the order of 10 attoliter. The analysis of high-resolution optical and topographical data measured on the same oil droplet reveals how droplet shape and surface wetting behavior are influenced by local properties of the surface. The experimental results are compared with results obtained by molecular dynamics simulations which take into consideration the properties of the local chemical environment. I will discuss the future direction of this research and how the results could be applied in the domain of natural resources management.
The presence of dark matter on a wide range of astrophysical scales is one of the observational pillars of the current cosmological model. In particular, spiral galaxies are known to be dark matter dominated systems, and one of the most outstanding astrophysical proofs of its existence. Yet, retrieving information about the the dark matter distribution in our very own spiral Galaxy, the Milky Way, is quite challenging.
I will first show how a new set of analysis of purely observational data permit to draw strong model-independent conclusions on the presence of DM in the Milky Way and especially in its innermost regions.
In a second time, how these very sets of data allow us to both sketch the DM distribution while getting rid of theoretical bias, and to refine analysis based on theoretical priors (i.e. profiles from numerical simulations such as NFW or Einasto) to an unprecedented level of precision.
These new results open up an interesting avenue for the study of the dark matter distribution in the Milky Way with forthcoming observational results.
The Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence is one of the most important results of String Theory. It states that a gravity theory in Anti-de Sitter space-time (AdS) is dual to a Conformal Quantum Field Theory on the boundary of AdS. The duality connects strongly coupled Quantum Field Theories to weakly coupled gravity theories. In recent years it has been suggested that this fact can be used to gain easier excess to strongly coupled Quantum Field Theories. Examples are real-time, high density processes in Quantum Chromodynamics as well as high temperature superconductivity which is presumably driven by strong interaction processes. In both cases experimental data exists which can be used to test the correspondence. In this talk I will motivate the AdS/CFT correspondence, explain its potential and point out future directions.
