Página 2 dos resultados de 15310 itens digitais encontrados em 0.008 segundos

Sobre separação cega de fontes : proposições e analise de estrategias para processamento multi-usuario

Charles Casimiro Cavalcante
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/04/2004 Português
Relevância na Pesquisa
26.643806%
Esta tese é dedicada ao estudo de tecnicas de separação cega de fontes aplicadas ao contexto de processamento multiusuario em comunicações digitais. Utilizando estrategias de estimação da função de densidade de probabilidade (fdp), são propostos dois metodos de processamento multiusuario que permitem recuperar os sinais transmitidos pela medida de similaridade de Kullback-Leibler entre a fdp dos sinais a sa?da do dispositivo de separação e um modelo parametrico que contem as caracteristicas dos sinais transmitidos. Alem desta medida de similaridade, são empregados diferentes metodos que garantem a descorrelação entre as estimativas das fontes de tal forma que os sinais recuperados sejam provenientes de diferentes fontes. E ainda realizada a analise de convergencia dos metodos e suas equivalencias com tecnicas classicas resultando em algumas importantes relações entre criterios cegos e supervisionados, tais como o criterio proposto e o criterio de maxima a posteriori. Estes novos metodos aliam a capacidade de recuperação da informação uma baixa complexidade computacional. A proposição de metodos baseados na estimativa da fdp permitiu a realização de um estudo sobre o impacto das estatisticas de ordem superior em algoritmos adaptativos para separação cega de fontes. A utilização da expansão da fdp em series ortonormais permite avaliar atraves dos cumulantes a dinamica de um processo de separação de fontes. Para tratar com problemas de comunicação digital e proposta uma nova serie ortonormal...

The CRYPTOCHROME Photoreceptor Gates PDF Neuropeptide Signaling to Set Circadian Network Hierarchy in Drosophila

Zhang, Luoying; Lear, Bridget C.; Seluzicki, Adam; Allada, Ravi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.715276%
Circadian clocks in the brain are organized as coupled oscillators that integrate seasonal cues to time daily behaviors. In Drosophila, the PIGMENT DISPERSING FACTOR (PDF) neuropeptide expressing morning (M) and non-PDF evening (E) cells are coupled cell groups important for morning and evening behavior, respectively. Depending on day length, either M- (short days) or E-cells (long days) dictate both morning and evening phase, a phenomenon we term network hierarchy. To examine the role of PDF in light-dark conditions, we examined flies lacking both the PDF receptor (PDFR) and the circadian photoreceptor CRYPTOCHROME (CRY). We found that subsets of E-cells exhibit molecular oscillations antiphase to those of wild-type flies, single cry mutants, or single Pdfr mutants, demonstrating a potent role for PDF in light-mediated entrainment specifically in the absence of CRY. Moreover, evening behavioral phase is more strongly reset by PDF(+) M-cells in the absence of CRY. Based on our findings, we propose that CRY can gate PDF signaling to determine behavioral phase and network hierarchy.

PDF Receptor Expression Reveals Direct Interactions between Circadian Oscillators in Drosophila

Im, Seol Hee; Taghert, Paul H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/06/2010 Português
Relevância na Pesquisa
26.715276%
Daily rhythms of behavior are controlled by a circuit of circadian pacemaking neurons. In Drosophila, 150 pacemakers participate in this network, and recent observations suggest the network is divisible into M and E oscillators which normally interact and synchronize. Sixteen oscillator neurons (the small and large LNvs) express a neuropeptide called pigment dispersing factor (PDF) whose signaling is often equated with M oscillator output. Given the significance of PDF signaling to numerous aspects of behavioral and molecular rhythms, determining precisely where and how signaling via the PDF receptor (PDFR) occurs is now a central question in the field. Here we show that GAL4-mediated rescue of pdfr phenotypes using a UAS-PDFR transgene is insufficient to provide complete behavioral rescue. In contrast, we describe a ~70 kB PDF receptor (pdfr) transgene which does rescue the entire pdfr circadian behavioral phenotype. The transgene is widely but heterogeneously expressed among pacemakers, and also among a limited number of non-pacemakers. Our results support an important hypothesis: the small LNv cells directly target a subset of the other crucial pacemaker neurons cells. Furthermore, expression of the transgene confirms an autocrine feedback signaling by PDF back to PDF-expressing cells. Finally...

PDF and cAMP enhance PER stability in Drosophila clock neurons

Li, Yue; Guo, Fang; Shen, James; Rosbash, Michael
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.6839%
This work describes an advance in the understanding of how the important circadian neuropeptide PDF contributes to the function of the molecular clock in Drosophila neurons. The famous perS allele of period significantly improves the rhythmicity of flies missing PDF. The perS gene product degrades rapidly, suggesting that PDF-mediated cAMP affects PER stability. Indeed, increasing cAMP levels and cAMP-mediated protein kinase A (PKA) activity stabilizes PER, in tissue culture cells and in circadian neurons. PDF addition to fly brains in vitro has a similar effect. Our observations taken together indicate that PDF contributes to clock neuron function by activating PKA, stabilizing PER, and thereby slowing the pace of clock neurons that respond to PDF.

Modelagem matemática de escoamentos reativos turbulentos utilizando uma metodologia hibrida LES/PDF; Mathematical and numerical modeling of turbulent reactive ows using a hybrid LES / PDF methodology

Vedovoto, João Marcelo
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
26.715276%
O presente trabalho foi dedicado ao desenvolvimento e implementação de uma plataforma computacional destinada a simulações numéricas de escoamentos turbulentos reativos a baixo numero de Mach. O algoritmo desenvolvido para a solução de transporte é baseado em um método de projeção totalmente implícito. Uma restrição fisicamente consistente é imposta sobre o campo de correção de pressão para garantir que o campo de velocidade seja corretamente resolvido. A plataforma numérica foi extensivamente verificada utilizando o Método das Soluções Manufaturadas tanto para escoamentos incompressíveis quanto para escoamentos com variação de massa especifica. Dois modelos de turbulência diferentes foram implementados para representar as tensões submalha: o modelo Smagorinsky clássico e os modelo dinâmico. A imposição de condições de contorno turbulentas e realistas na entrada do domínio computacional é estudada em detalhes no presente trabalho. Três metodologias distintas foram implementadas e seus efeitos são analisados tanto para escoamentos inertes quanto reativos. Uma formulação hibrida de Simulação de Grandes Escalas/ Função Densidade de Probabilidade Transportada (LES-PDF) foi adotada. A inuência das utuações da escala submalha do escalar reativo na taxa de reação química filtrada é levada em conta no contexto da PDF Lagrangiana. O modelo de PDF correspondente faz uso da técnica de Monte Carlo: Equações diferenciais estocásticas (SDE)...

Bridging the gap between closed and open data. System proposal for the Portuguese Legislation

Moniz, Nuno Miguel Pereira
Fonte: Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto Publicador: Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto
Tipo: Dissertação de Mestrado
Publicado em //2012 Português
Relevância na Pesquisa
26.715276%
Esta dissertação apresenta uma proposta de sistema capaz de preencher a lacuna entre documentos legislativos em formato PDF e documentos legislativos em formato aberto. O objetivo principal é mapear o conhecimento presente nesses documentos de maneira a representar essa coleção como informação interligada. O sistema é composto por vários componentes responsáveis pela execução de três fases propostas: extração de dados, organização de conhecimento, acesso à informação. A primeira fase propõe uma abordagem à extração de estrutura, texto e entidades de documentos PDF de maneira a obter a informação desejada, de acordo com a parametrização do utilizador. Esta abordagem usa dois métodos de extração diferentes, de acordo com as duas fases de processamento de documentos – análise de documento e compreensão de documento. O critério utilizado para agrupar objetos de texto é a fonte usada nos objetos de texto de acordo com a sua definição no código de fonte (Content Stream) do PDF. A abordagem está dividida em três partes: análise de documento, compreensão de documento e conjunção. A primeira parte da abordagem trata da extração de segmentos de texto, adotando uma abordagem geométrica. O resultado é uma lista de linhas do texto do documento; a segunda parte trata de agrupar os objetos de texto de acordo com o critério estipulado...

A compression algorithm for the combination of PDF sets

Carrazza, Stefano; Latorre, José I.; Rojo, Juan; Watt, Graeme
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.7405%
The current PDF4LHC recommendation to estimate uncertainties due to parton distribution functions (PDFs) in theoretical predictions for LHC processes involves the combination of separate predictions computed using PDF sets from different groups, each of which comprises a relatively large number of either Hessian eigenvectors or Monte Carlo (MC) replicas. While many fixed-order and parton shower programs allow the evaluation of PDF uncertainties for a single PDF set at no additional CPU cost, this feature is not universal, and, moreover, the a posteriori combination of the predictions using at least three different PDF sets is still required. In this work, we present a strategy for the statistical combination of individual PDF sets, based on the MC representation of Hessian sets, followed by a compression algorithm for the reduction of the number of MC replicas. We illustrate our strategy with the combination and compression of the recent NNPDF3.0, CT14 and MMHT14 NNLO PDF sets. The resulting compressed Monte Carlo PDF sets are validated at the level of parton luminosities and LHC inclusive cross sections and differential distributions. We determine that around 100 replicas provide an adequate representation of the probability distribution for the original combined PDF set...

Comparative Analysis of Pdf-Mediated Circadian Behaviors Between Drosophila melanogaster and D. virilis

Bahn, Jae Hoon; Lee, Gyunghee; Park, Jae H.
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
Publicado em /03/2009 Português
Relevância na Pesquisa
26.6839%
A group of small ventrolateral neurons (s-LNv's) are the principal pacemaker for circadian locomotor rhythmicity of Drosophila melanogaster, and the pigment-dispersing factor (Pdf) neuropeptide plays an essential role as a clock messenger within these neurons. In our comparative studies on Pdf-associated circadian rhythms, we found that daily locomotor activity patterns of D. virilis were significantly different from those of D. melanogaster. Activities of D. virilis adults were mainly restricted to the photophase under light:dark cycles and subsequently became arrhythmic or weakly rhythmic in constant conditions. Such activity patterns resemble those of Pdf01 mutant of D. melanogaster. Intriguingly, endogenous D. virilis Pdf (DvPdf) expression was not detected in the s-LNv-like neurons in the adult brains, implying that the Pdf01-like behavioral phenotypes of D. virilis are attributed in part to the lack of DvPdf in the s-LNv-like neurons. Heterologous transgenic analysis showed that cis-regulatory elements of the DvPdf transgene are capable of directing their expression in all endogenous Pdf neurons including s-LNv's, as well as in non-Pdf clock neurons (LNd's and fifth s-LNv) in a D. melanogaster host. Together these findings suggest a significant difference in the regulatory mechanisms of Pdf transcription between the two species and such a difference is causally associated with species-specific establishment of daily locomotor activity patterns.

Análisis de la transmisión de la información circadiana en Drosophila; Output signals from the circadian master clock in Drosophila

Depetris Chauvin, Ana
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: Tesis Doctoral Formato: text; pdf
Publicado em //2013 07 11 Português
Relevância na Pesquisa
26.643806%
El control rítmico del comportamiento depende de la actividad de la red circadiana en el cerebro. En Drosophila existen dos modelos que dan cuenta del origen de las oscilaciones circadianas, uno basado en las oscilaciones moleculares de proteínas específicas y otro basado en la actividad de membrana. Por otra parte, desde el marcapasos central (las neuronas s-LNvs) la información circadiana es transmitida hacia el organismo a través de vías de salida entre las que se destaca el neuropéptido PDF. A su vez, las terminales dorsales de las s-LNvs presentan remodelamiento estructural diario pudiendo esto implicar cambios circadianos en los contactos sinápticos. En esta tesis probamos la validez del modelo basado en las oscilaciones moleculares como generador de las oscilaciones circadianas, mientras que determinamos a la actividad eléctrica de membrana como una importante vía de salida desde el marcapasos central. Demostramos que la actividad eléctrica de las neuronas PDF es crucial para determinar los niveles del neuropéptido en las terminales axonales, la plasticidad estructural y de las zonas sinápticas, con el consiguiente efecto sobre el comportamiento locomotor rítmico. Por otra parte, la realización de un screen de circuitos postsinápticos a las neuronas PDF utilizando la técnica de GRASP arrojó resultados que apoyan fuertemente nuestra hipótesis de cambios circadianos en la conectividad. En paralelo...

LHAPDF: PDF Use from the Tevatron to the LHC

Bourilkov, D; Group, R C; Whalley, M R
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.643806%
Parton Density Functions (PDFs) and their uncertainties are extremely important topics for both the Tevatron and the LHC. Experiments at the Tevatron can enhance this knowledge not only by constraining the PDF fits, but also by developing and refining the available PDF tools through feed-back from the experiments that are currently analyzing the highest energy hadron collider data available. It is important that the community has standardized tools and methods at its disposal. In this note we summarize briefly the most recent developments of the The Les Houches Accord PDF (LHAPDF), which is the modern replacement for PDFLIB. We also outline and compare the methods of quantifying the impact of PDF uncertainties on physical observables. The PDF weighting method for propagating errors from PDFs to event generator observables is outlined in detail, and example code for using this method with PYTHIA is also included.; Comment: 8 pages, 2 figures, 2 tables; prepared for the TeV4LHC workshop; v2 - reference added

ManeParse: Mathematica Toolbox for PDF Uncertainties and Application to New Physics Searches

Godat, Eric
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/10/2015 Português
Relevância na Pesquisa
26.643806%
As the LHC begins Run 2 at an even higher energy, one of the top priorities will be to search for new particles (possibly from SUSY) at the highest energy scales. In addition to direct production of new particles, they can mix with Standard Model (SM) particles to yield discrepancies from the usual predictions. To distinguish this new physics from old uncertainties, we need tools to precisely quantify the uncertainties of the SM predictions. Here we present a versatile set of utility functions built with Mathematica that is capable of working with a variety of PDF formats including the recent LHAPDF6 format. This software can perform PDF calculations within the Mathematica framework and compare results from different PDF collaborations. The package includes both the central PDF value as well as the full error sets needed for PDF uncertainty analysis; a variety of sample error definitions are implemented. We demonstrate this package for the case of a new heavy scalar particle production at the LHC.; Comment: 5 pages, 11 figures, Presentation at the DPF 2015 Meeting of the American Physical Society Division of Particles and Fields, Ann Arbor, Michigan, August 4-8, 2015

The Atacama Cosmology Telescope: A Measurement of the Thermal Sunyaev-Zel'dovich One-Point PDF

Hill, J. Colin; Sherwin, Blake D.; Smith, Kendrick M.; Addison, Graeme E.; Battaglia, Nick; Battistelli, Elia S.; Bond, J. Richard; Calabrese, Erminia; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Gralla, Megan B.; Hajian,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/11/2014 Português
Relevância na Pesquisa
26.643806%
We present a measurement of the one-point probability distribution function (PDF) of the thermal Sunyaev-Zel'dovich (tSZ) decrement in the pixel temperature histogram of filtered 148 GHz sky maps from the Atacama Cosmology Telescope (ACT). The PDF includes the signal from all galaxy clusters in the map, including objects below the signal-to-noise threshold for individual detection, making it a particularly sensitive probe of the amplitude of matter density perturbations, $\sigma_8$. We use a combination of analytic halo model calculations and numerical simulations to compute the theoretical tSZ PDF and its covariance matrix, accounting for all noise sources and including relativistic corrections. From the measured ACT 148 GHz PDF alone, we find $\sigma_8 = 0.793 \pm 0.018$, with additional systematic errors of $\pm 0.017$ due to uncertainty in intracluster medium gas physics and $\pm 0.006$ due to uncertainty in infrared point source contamination. Using effectively the same data set, the statistical error here is a factor of two lower than that found in ACT's previous $\sigma_8$ determination based solely on the skewness of the tSZ signal. In future temperature maps with higher sensitivity, the tSZ PDF will break the degeneracy between intracluster medium gas physics and cosmological parameters.; Comment: 29 pages...

Theory of the 1-point PDF for incompressible Navier-Stokes fluids

Tessarotto, M.; Asci, C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/10/2009 Português
Relevância na Pesquisa
26.7405%
Fundamental aspects of fluid dynamics are related to construction of statistical models for incompressible Navier-Stokes fluids. The latter can be considered either \textit{deterministic} or \textit{stochastic,} respectively for \textit{regular} or \textit{turbulent flows.} In this work we claim that a possible statistical formulation of this type can be achieved by means of the 1-point (local) velocity-space probability density function (PDF, $f_{1}$) to be determined in the framework of the so-called inverse kinetic theory (IKT). There are several important consequences of the theory. These include, in particular, the characterization of the initial PDF [for the statistical model ${f_{1},\Gamma} ]$ . This is found to be generally non-Gaussian PDF, even in the case of flows which are regular at the initial time. Moreover, both for regular and turbulent flows, its time evolution is provided by a Liouville equation, while the corresponding Liouville operator is found to depend only on a finite number of velocity moments of the same PDF. Hence, its time evolution depends (functionally) solely on the same PDF. In addition, the statistical model here developed determines uniquely both the initial condition and the time evolution of $f_{1}.$ As a basic implication...

A non-hybrid method for the PDF equations of turbulent flows on unstructured grids

Bakosi, J.; Franzese, P.; Boybeyi, Z.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/06/2010 Português
Relevância na Pesquisa
26.6839%
In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. A set of parallel algorithms is proposed to provide an efficient solution of the PDF transport equation, modeling the joint PDF of turbulent velocity, frequency and concentration of a passive scalar in geometrically complex configurations. An unstructured Eulerian grid is employed to extract Eulerian statistics, to solve for quantities represented at fixed locations of the domain (e.g. the mean pressure) and to track particles. All three aspects regarding the grid make use of the finite element method (FEM) employing the simplest linear FEM shape functions. To model the small-scale mixing of the transported scalar, the interaction by exchange with the conditional mean model is adopted. An adaptive algorithm that computes the velocity-conditioned scalar mean is proposed that homogenizes the statistical error over the sample space with no assumption on the shape of the underlying velocity PDF. Compared to other hybrid particle-in-cell approaches for the PDF equations, the current methodology is consistent without the need for consistency conditions. The algorithm is tested by computing the dispersion of passive scalars released from concentrated sources in two different turbulent flows: the fully developed turbulent channel flow and a street canyon (or cavity) flow. Algorithmic details on estimating conditional and unconditional statistics...

PDF/A-3u as an archival format for Accessible mathematics

Moore, Ross
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/06/2014 Português
Relevância na Pesquisa
26.643806%
Including LaTeX source of mathematical expressions, within the PDF document of a text-book or research paper, has definite benefits regarding `Accessibility' considerations. Here we describe three ways in which this can be done, fully compatibly with international standards ISO 32000, ISO 19005-3, and the forthcoming ISO 32000-2 (PDF 2.0). Two methods use embedded files, also known as `attachments', holding information in either LaTeX or MathML formats, but use different PDF structures to relate these attachments to regions of the document window. One uses structure, so is applicable to a fully `Tagged PDF' context, while the other uses /AF tagging of the relevant content. The third method requires no tagging at all, instead including the source coding as the /ActualText replacement of a so-called `fake space'. Information provided this way is extracted via simple Select/Copy/Paste actions, and is available to existing screen-reading software and assistive technologies.; Comment: This is a post-print version of original in volume: S.M. Watt et al. (Eds.): CICM 2014, LNAI 8543, pp.184-199, 2014; available at http://link.springer.com/search?query=LNAI+8543, along with supplementary PDF. This version, with supplement as attachment...

On the evolution of the density pdf in strongly self-gravitating systems

Girichidis, Philipp; Konstandin, Lukas; Whitworth, Anthony P.; Klessen, Ralf S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.643806%
The time evolution of the probability density function (PDF) of the mass density is formulated and solved for systems in free-fall using a simple appoximate function for the collapse of a sphere. We demonstrate that a pressure-free collapse results in a power-law tail on the high-density side of the PDF. The slope quickly asymptotes to the functional form $\mathrm{P}_v(\rho)\propto\rho^{-1.54}$ for the (volume-weighted) PDF and $\mathrm{P}_m(\rho)\propto\rho^{-0.54}$ for the corresponding mass-weighted distribution. From the simple approximation of the PDF we derive analytic descriptions for mass accretion, finding that dynamically quiet systems with narrow density PDFs lead to retarded star formation and low star formation rates. Conversely, strong turbulent motions that broaden the PDF accelerate the collapse causing a bursting mode of star formation. Finally, we compare our theoretical work with observations. The measured star formation rates are consistent with our model during the early phases of the collapse. Comparison of observed column density PDFs with those derived from our model suggests that observed star-forming cores are roughly in free-fall.; Comment: accepted for publication, 13 pages

An Upper Bound to the Marginal PDF of the Ordered Eigenvalues of Wishart Matrices

Park, Hong Ju; Ayanoglu, Ender
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/12/2011 Português
Relevância na Pesquisa
26.6839%
Diversity analysis of a number of Multiple-Input Multiple-Output (MIMO) applications requires the calculation of the expectation of a function whose variables are the ordered multiple eigenvalues of a Wishart matrix. In order to carry out this calculation, we need the marginal pdf of an arbitrary subset of the ordered eigenvalues. In this letter, we derive an upper bound to the marginal pdf of the eigenvalues. The derivation is based on the multiple integration of the well-known joint pdf, which is very complicated due to the exponential factors of the joint pdf. We suggest an alternative function that provides simpler calculation of the multiple integration. As a result, the marginal pdf is shown to be bounded by a multivariate polynomial with a given degree. After a standard bounding procedure in a Pairwise Error Probability (PEP) analysis, by applying the marginal pdf to the calculation of the expectation, the diversity order for a number of MIMO systems can be obtained in a simple manner. Simulation results that support the analysis are presented.; Comment: 6 pages, 2 figures

Constraints on the gluon PDF from top quark pair production at hadron colliders

Czakon, Michal; Mangano, Michelangelo L.; Mitov, Alexander; Rojo, Juan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.6839%
Using the recently derived NNLO cross sections \cite{Czakon:2013goa}, we provide NNLO+NNLL theoretical predictions for top quark pair production based on all the available NNLO PDF sets, and compare them with the most precise LHC and Tevatron data. In this comparison we study in detail the PDF uncertainty and the scale, $m_t$ and $\alpha_s$ dependence of the theoretical predictions for each PDF set. Next, we observe that top quark pair production provides a powerful direct constraint on the gluon PDF at large $x$, and include Tevatron and LHC top pair data consistently into a global NNLO PDF fit. We then explore the phenomenological consequences of the reduced gluon PDF uncertainties, by showing how they can improve predictions for Beyond the Standard Model processes at the LHC. Finally, we update to full NNLO+NNLL the theoretical predictions for the ratio of top quark cross sections between different LHC center of mass energies, as well as the cross sections for hypothetical heavy fourth-generation quark production at the LHC.; Comment: 29 pages, 13 figures, accepted for publication in JHEP

The gamma-ray-flux PDF from galactic halo substructure

Lee, Samuel K.; Ando, Shin'ichiro; Kamionkowski, Marc
Fonte: Institute of Physics Publicador: Institute of Physics
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 03/07/2009 Português
Relevância na Pesquisa
26.715276%
One of the targets of the recently launched Fermi Gamma-ray Space Telescope is a diffuse gamma-ray background from dark-matter annihilation or decay in the Galactic halo. N-body simulations and theoretical arguments suggest that the dark matter in the Galactic halo may be clumped into substructure, rather than smoothly distributed. Here we propose the gamma-ray-flux probability distribution function (PDF) as a probe of substructure in the Galactic halo. We calculate this PDF for a phenomenological model of halo substructure and determine the regions of the substructure parameter space in which the PDF may be distinguished from the PDF for a smooth distribution of dark matter. In principle, the PDF allows a statistical detection of substructure, even if individual halos cannot be detected. It may also allow detection of substructure on the smallest microhalo mass scales, ~ M_⊕, for weakly-interacting massive particles (WIMPs). Furthermore, it may also provide a method to measure the substructure mass function. However, an analysis that assumes a typical halo substructure model and a conservative estimate of the diffuse background suggests that the substructure PDF may not be detectable in the lifespan of Fermi in the specific case that the WIMP is a neutralino. Nevertheless...

In Silico Docking Analysis of Peptide Deformylase (PDF) - A Novel Target for Prophylaxis of Leptospirosis

Virupaksha A. Bastikar; Shweta R. Fulsundar; Jagdish S. Nair
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
26.643806%
Peptide deformylase (PDF) is a metalloproteinase and executes an essential step in the maturation of proteins in eubacteria, by removing the formyl group from the N-terminal methionine residue of ribosome-synthesized polypeptides. This process is crucial for bacterial survival because mature proteins do not retain N-formyl-methionine, and all known N-terminal peptidases cannot utilize formylated peptides as substrate. Thus, inhibition of PDF is essential to obstruct the bacterial protein maturation process. Antibiotics based on PDF inhibition have the potential to provide the much needed antibacterial activity against most of the major drug-resistant pathogens. This study comprises an implementation of _in-silico_ techniques to validate and map the features of the respective active site of PDF from _Leptospira interrogans_. Our analysis consolidates PDF as a promising target for developing novel alternatives as well as indicates superior affinity of current therapeutic agents towards it. This consequently provides a new insight for leptospirosis treatment.