On Quantum Special Kaehler Geometry

We compute the effective black hole potential V of the most general N=2, d=4 (local) special Kaehler geometry with quantum perturbative corrections, consistent with axion-shift Peccei-Quinn symmetry and with cubic leading order behavior. We determine the charge configurations supporting axion-free attractors, and explain the differences among various configurations in relations to the presence of ``flat'' directions of V at its critical points. Furthermore, we elucidate the role of the sectional curvature at the non-supersymmetric critical points of V, and compute the Riemann tensor (and related quantities), as well as the so-called E-tensor. The latter expresses the non-symmetricity of the considered quantum perturbative special Kaehler geometry.Comment: 1+43 pages; v2: typo corrected in the curvature of Jordan symmetric sequence at page 2

In-Situ absolute phase detection of a microwave field via incoherent fluorescence

Measuring the amplitude and the absolute phase of a monochromatic microwave field at a specific point of space and time has many potential applications, including precise qubit rotations and wavelength quantum teleportation. Here we show how such a measurement can indeed be made using resonant atomic probes, via detection of incoherent fluorescence induced by a laser beam. This measurement is possible due to self-interference effects between the positive and negative frequency components of the field. In effect, the small cluster of atoms here act as a highly localized pick-up coil, and the fluorescence channel acts as a transmission line.Comment: 13 pages, 5 figure

Automatic speaker segmentation using multiple features and distance measures: a comparison of three approaches

This paper addresses the problem of unsupervised speaker change detection. Three systems based on the Bayesian Information Criterion (BIC) are tested. The first system investigates the AudioSpectrumCentroid and the AudioWaveformEnvelope features, implements a dynamic thresholding followed by a fusion scheme, and finally applies BIC. The second method is a real-time one that uses a metric-based approach employing the line spectral pairs and the BIC to validate a potential speaker change point. The third method consists of three modules. In the first module, a measure based on second-order statistics is used; in the second module, the Euclidean distance and T2 Hotelling statistic are applied; and in the third module, the BIC is utilized. The experiments are carried out on a dataset created by concatenating speakers from the TIMIT database, that is referred to as the TIMIT data set. A comparison between the performance of the three systems is made based on t-statistics

Aspectos agro-econômicos da cultura da mandioca: potencialidades e limitações.

Apesar de sua importância sócio-econômica, a mandioca não vem apresentando, nos últimos anos, um padrão estável de produção ao longo do tempo, exibindo uma significativa oscilação, principalmente, na sua área cultivada e no preço. Dentre os fatores considerados como responsáveis pela má performance do produto podem-se destacar a falta de utilização de suas potencialidades agronômicas e econômicas e a desorganização dos produtores. Este trabalho tem como objetivo apresentar algumas dessas potencialidades, analisar pontos relevantes referentes á demanda do produto e identificar as limitações de ordem técnica e econômica, considerando-se a estrutura de mercado enfrentada, sobretudo, pelos produtores de fécula. A essa discussão adicionam-se os aspectos ligados especificamente ao sistema produtivo que ainda não foram totalmente solucionados. Para finalizar são analisados os efeitos da inexistência de uma estrutura eficiente de coordenação dos diferentes elos da cadeia produtiva da mandioca.bitstream/item/81389/1/aspectos-agro-economicos-Carlos-estevao-Documentos-86-1999.pdfMemória

Localization properties of a tight-binding electronic model on the Apollonian network

An investigation on the properties of electronic states of a tight-binding Hamiltonian on the Apollonian network is presented. This structure, which is defined based on the Apollonian packing problem, has been explored both as a complex network, and as a substrate, on the top of which physical models can defined. The Schrodinger equation of the model, which includes only nearest neighbor interactions, is written in a matrix formulation. In the uniform case, the resulting Hamiltonian is proportional to the adjacency matrix of the Apollonian network. The characterization of the electronic eigenstates is based on the properties of the spectrum, which is characterized by a very large degeneracy. The $2\pi /3$ rotation symmetry of the network and large number of equivalent sites are reflected in all eigenstates, which are classified according to their parity. Extended and localized states are identified by evaluating the participation rate. Results for other two non-uniform models on the Apollonian network are also presented. In one case, interaction is considered to be dependent of the node degree, while in the other one, random on-site energies are considered.Comment: 7pages, 7 figure

Dual Brane Pairs, Chains and the Bekenstein-Hawking Entropy

A proposal towards a microscopic understanding of the Bekenstein-Hawking entropy for D=4 spacetimes with event horizon is made. Since we will not rely on supersymmetry these spacetimes need not be supersymmetric. Euclidean D-branes which wrap the event horizon's boundary will play an important role. After arguing for a discretization of the Euclidean D-brane worldvolume based on the worldvolume uncertainty relation, we count chainlike excitations on the worldvolume of specific dual Euclidean brane pairs. Without the need for supersymmetry it is shown that one can thus reproduce the D=4 Bekenstein-Hawking entropy and its logarithmic correction.Comment: 14 pages, 1 figur

Análise de adoção das variedades de mandioca 'Alagoana' e 'Lagoão' no Município de Brotas de Macaúbas - Ba.

A adoção de variedades mais produtivas, resistentes às doenças como bacteriose, resistentes à seca e ciclo precoce pode ajudar a aumentar o rendimento da mandiocultura na região Nordeste, e principalmente nas propriedades de agricultores familiares onde predomina a agricultura de subsistência e de baixo índice de adoção de tecnologias. Neste contexto, a pesquisa participativa pode ser uma estratégia bastante eficiente para aumentar as chances de adoção e garantir a disponibilidade de maniva para o plantio, uma vez que a indisponibilidade de manivas é uma das principais causas para os níveis de baixa adoção das variedades geneticamente melhoradas (Fukuda et al., 2008, Gonzalez et al., 2011). O objetivo deste trabalho foi avaliar o grau de adoção das variedades 'Lagoão' e 'Alagoana' pelos agricultores do município de Brotas de Macaúbas-BA, através da aplicação de questionário com abordagem focada nas variedades avaliadas, na inserção da produção no mercado, na assistência técnica e nas informações socioeconômico culturais dos agricultores.Melhoramento genético. Resumo n. 188

Spin-glass-like behavior of Ge:Mn

We present a detailed study of the magnetic properties of low-temperature-molecular-beam-epitaxy grown Ge:Mn dilute magnetic semiconductor films. We find strong indications for a frozen state of Ge_{1-x}Mn_{x}, with freezing temperatures of T_f=12K and T_f=15K for samples with x=0.04 and x=0.2, respectively, determined from the difference between field-cooled and zero-field-cooled magnetization. For Ge_{0.96}Mn_{0.04}, ac susceptibility measurements show a peak around T_f, with the peak position T'_f shifting as a function of the driving frequency f by Delta T_f' / [T_f' Delta log f] ~ 0.06, whereas for sample Ge_{0.8}Mn_{0.2} a more complicated behavior is observed. Furthermore, both samples exhibit relaxation effects of the magnetization after switching the magnitude of the external magnetic field below T_f which are in qualitative agreement with the field- and zero-field-cooled magnetization measurements. These findings consistently show that Ge:Mn exhibits a frozen magnetic state at low temperatures and that it is not a conventional ferromagnet.Comment: Revised version contains extended interpretation of experimental dat

Analysis of difussion strategies in northeeast Brazil for new cassava varieties with new improved nutritional quality.

In 2006, Embrapa, supported by the HarvestPlus Program and CIAT released four yellow varieties with improved levels of provitamin A: BRS Dourada, BRS Gema de Ovo, Amarelo I and Amarelo II. For the diffusion process two strategies were used: 1) a participatory research approach with farmers and 2) public awareness raising activities. To evaluate the results of these two diffusion strategies, a socioeconomic analysis was carried out through two surveys applied in NE Brazil, one with producers involve in the participatory research process (Group 1) and the second with producers who requested stakes (seed) via telephone or mail, following the Launching Event (Group 2). For data analysis, a logit model and a Multiple Correspondence Analysis (MCA) were implemented. A significant finding was the large gap between actual early adoption rates of Group 1 (62.5%) and Group 2 (15.0%) in comparison with the potential adoption rates of the groups (62.1% and 64% respectively). This difference in early adoption rate for Group 2, compared to Groups 1 could be explained, in great part, by the lack of availability of seeds of the new varieties. Results showed that several strategies used for diffusion might be successful, each with its own advantages and disadvantages. Within the first strategy process the factors found to enhance adoption rates were: awareness of the new varieties? advantages; public entities as the main information sources; and involvement in participatory research. Within the second strategy trends were found between adoption rates and producer characteristics including: ownership of land; middle-level income; advance education level; and use of information mediums, namely the Internet. In the case of the second strategy, a lack of seeds was one of the main factors limiting the adoption process Currently a new study about household perceptions toward some crops (bean, chickpea, sweet potato, cassava and corn) with better nutritional qualities is developing in Sergipe