General CMB and Primordial Bispectrum Estimation I: Mode Expansion, Map-Making and Measures of f_NL

We present a detailed implementation of two bispectrum estimation methods which can be applied to general non-separable primordial and CMB bispectra. The method exploits bispectrum mode decompositions on the domain of allowed wavenumber or multipole values. Concrete mode examples constructed from symmetrised tetrahedral polynomials are given, demonstrating rapid convergence for known bispectra. We use these modes to generate simulated CMB maps of high resolution (l > 2000) given an arbitrary primordial power spectrum and bispectrum or an arbitrary late-time CMB angular power spectrum and bispectrum. By extracting coefficients for the same separable basis functions from an observational map, we are able to present an efficient and general f_NL estimator for a given theoretical model. The estimator has two versions comparing theoretical and observed coefficients at either primordial or late times, thus encompassing a wider range of models, including secondary anisotropies, lensing and cosmic strings. We provide examples and validation of both f_NL estimation methods by direct comparison with simulations in a WMAP-realistic context. In addition, we show how the full bispectrum can be extracted from observational maps using these mode expansions, irrespective of the theoretical model under study. We also propose a universal definition of the bispectrum parameter F_NL for more consistent comparison between theoretical models. We obtain WMAP5 estimates of f_NL for the equilateral model from both our primordial and late-time estimators which are consistent with each other, as well as with results already published in the literature. These general bispectrum estimation methods should prove useful for the analysis of nonGaussianity in the Planck satellite data, as well as in other contexts.Comment: 41 pages, 17 figure

Enraizamento in vitro de brotações de Eucalyptus dunnii utilizando altas concentrações de auxinas.

bitstream/item/104310/1/48EnraizamentoInVitro0001.pd

Avaliação do florescimento e do potencial de produção de sementes de Eucalyptus dunnii Maid. no Brasil.

O florescimento e o potencial para a produção de sementes foram avaliados em populações de Eucalyptus dunnii Maid., em idade prevista de florescimento, implantadas em 18 localidades do Brasil. Foram coletados parâmetros geográficos e climáticos das populações, bem como, para cada povoamento, as seguintes informações: área, natureza, idade, procedências e densidade. Para as árvores que se encontravam no estágio reprodutivo, determinaram-se a ontogenia, a localização e a intensidade de florescimento e/ou frutificação. A localização geográfica influenciou no florescimento. Houve uma tendência de maior florescimento para os locais de latitudes mais elevadas, com temperaturas médias do mês mais frio mais baixas. Devido às árvores das populações amostradas estarem ontogenicamente adultas, não se verificaram diferenças entre as idades, em relação ao florescimento. Da mesma forma, o florescimento não foi influenciado pela localização das árvores no povoamento. Entretanto, observou-se que, as árvores de povoamentos desbastados precocemente, floresceram mais do que aquelas de povoamentos desbastados tardiamente. Observou-se, ainda, que as árvores de bordadura apresentaram um florescimento maior do que aquelas situadas no interior dos povoamentos. Observações desses efeitos associados sugerem que a eliminação da competição pela luz é fator fundamental para o florescimento dessa espécie

Untangling the immune basis of disease susceptibility

© 2020 Copyright Ribeiro and Graca. This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are creditedInteractions between immune cell receptors and proteins that determine disease susceptibility shed light on how different arms of the immune system are involved in three viral infections and Crohn's disease.info:eu-repo/semantics/publishedVersio

In vitro propagation of black wattle (Acacia mearnsii de Wild).

Made available in DSpace on 2014-06-07T06:56:17Z (GMT). No. of bitstreams: 1 IPEF.pdf: 164143 bytes, checksum: a287e19c10ed0d41c48db497e61d54d1 (MD5) Previous issue date: 1998-10-0

Enraizamento de estacas de Eucalyptus dunnii Maiden.

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Dilepton distributions at backward rapidities

The dilepton production at backward rapidities in $pAu$ and $pp$ collisions at RHIC and LHC energies is investigated in the dipole approach. The results are shown through the nuclear modification ratio $R_{pA}$ considering transverse momentum and rapidity spectra. The dilepton modification ratio presents interesting behavior at the backward rapidities when compared with the already known forward ones, since it is related with the large $x$ kinematical region that is being probed. The rapidity dependence of the nuclear modification ratio in the dilepton production is strongly dependent on the Bjorken $x$ behavior of the nuclear structure function ratio $R_{F_{2}}=F_{2}^{A}/F_{2}^{p}$. The $R_{pA}$ transverse momentum dependence at backward rapidities is modified due to the large $x$ nuclear effects: at RHIC energies, for instance, the ratio $R_{pA}$ is reduced as $p_T$ increases, presenting an opposite behavior when compared with the forward one. It implies that the dilepton production at backward rapidities should carry information of the nuclear effects at large Bjorken $x$, as well as that it is useful to investigate the $p_T$ dependence of the observables in this kinematical regime.Comment: 15 pages, 6 figures. Version published in the Phys. Rev.

A Sturm-Liouville equation on the crossroads of continuous and discrete hypercomplex analysis

The paper studies discrete structural properties of polynomials that play an important role in the theory of spherical harmonics in any dimensions. These polynomials have their origin in the research on problems of harmonic analysis by means of generalized holomorphic (monogenic) functions of hypercomplex analysis. The Sturm-Liouville equation that occurs in this context supplements the knowledge about generalized Vietoris number sequences Vn, first encountered as a special sequence (corresponding to n=2) by Vietoris in connection with positivity of trigonometric sums. Using methods of the calculus of holonomic differential equations, we obtain a general recurrence relation for Vn, and we derive an exponential generating function of Vn expressed by Kummer's confluent hypergeometric function.This work was supported by Portuguese funds through the CMAT—Research Centre of Mathematics of University of Minho—and through the CIDMA-Center of Research and Development in Mathematics and Applications (University of Aveiro) and the Portuguese Foundation for Science and Technology (“FCT - Fundação para a Ciência e Tecnologia”), within projects UIDB/00013/2020, UIDP/00013/2020, UIDB/04106/2020 , and UIDP/04106/2020

Demystifying Event-based Sensor Biasing to Optimize Signal to Noise for Space Domain Awareness

Neuromorphic dynamic vision sensors (DVS), often called event-based sensors (EBS), are a novel class of cameras that have recently shown potential to make a significant impact in the SDA community. Their biologically-inspired design simultaneously achieves high temporal resolution, wide dynamic range, low power consumption and sparse data output, making them an ideal fit for space applications. Although initial results for SDA are promising, they typically exhibit elevated noise rates in dim conditions and have thus far failed to outperform conventional cameras in terms of limiting visual magnitude and sensitivity with high telescope scan rates. A hurdle for widespread adoption is a lack of general guidance regarding optimal camera biases (settings) for SDA. Prior studies either serve as proof of concept or focus on algorithm development; however, to date, none have provided detailed guidance on biasing EBS to optimize signal to noise ratio (SNR) for SDA tasks. The goal of this paper is to narrow the knowledge gap between EBS pixel biasing and resulting performance to optimize their capabilities for SDA. To accomplish this, we adopt a bottom-up approach, revisiting the pixel architecture to consider physics-based performance limitations. In an EBS, each pixel responds autonomously, generating "events" in response to local brightness changes within its field of view (FOV), and outputs a sparse representation of the visual scene where each event is encoded by a pixel address (x,y), a microsecond resolution timestamp (t), and a single bit polarity value (p) indicating either an increase or decrease in brightness by a defined threshold. In most camera models, behavior is fine-tuned by adjusting roughly a half-dozen biases, including threshold levels (sensitivity), bandwidth (speed of the front-end photoreceptor), and refractory period (dead-time between events in a given pixel). These parameters make EBS cameras adaptable for varied applications, but many degrees of freedom presents a challenge for optimization. Researchers unfamiliar with the technology can be overwhelmed by the myriad of biasing options and must either rely on a prescribed set of biases or manually adjust them to achieve desired performance; the latter is not typically recommended for non-experts due to 2nd-order effects such as excessive noise rates. Manufacturer default biases are considered optimized for a broad range of applications, but recent studies have demonstrated non-conventional bias techniques can significantly reduce background noise in dim conditions while still retaining signal, suggesting that SDA capabilities could be improved by a more sophisticated biasing strategy. By conducting a detailed study of how sensitivity, response speed, and noise rates scale with varied bias configurations, we aim to approach an optimal SNR bias configuration and demonstrate the maximal capabilities of current generation COTS EBS cameras for SDA. To systematically analyze and benchmark performance against a calibrated and repeatable stimulus, we developed a custom SDA test-bench to simulate stars/satellites as sub-pixel point source targets of variable speed and brightness. The set-up includes an integrating light box to provide a calibrated flat-field illumination source, a custom 170 mm radius anodized aluminum disk with precision drilled holes of diameters ranging from 100 to 250 microns, and a digitally programmable motor capable of precise speed control from ~0.1 to 800 RPM. The disk is backlit by the flat-field illumination source and connected to the motor shaft, and a 7 x 10 cm region is viewed through a Fujinon 1:1.8/7-70mm CS mount lens at a distance of 50 cm. The FOV and zoom are chosen such that the dimension of the largest holes is still sub-pixel in diameter when in focus. Even with the ability to rapidly collect measurements with this setup, the overall parameter space is still too large to fully explore without any a-priori knowledge about how the sensor responds to signal and noise, and how this depends on biases. As a result, we consider fundamental pixel behaviors to devise an efficient test strategy. We first consider strategies to limit noise rates, as these can overwhelm sensor readout when the background is dark. In prior work, this was presumably accomplished by either reducing the bandwidth biases or increasing threshold biases, but these approaches inherently limit signal. Instead of this naive approach, we draw inspiration from two recent studies: the first demonstrated an optimal balance between two bandwidth related biases accessible in some camera prototypes, and the second relies on a key observation about the statistical distribution of noise events to devise two additional biasing techniques to enhance SNR by allowing either lower thresholds or broader bandwidth settings. Using these techniques as a starting point, we examine the performance the DAVIS346 EBS. We first report baseline performance using manufacturer default biases. To quantify performance, we measure sensitivity (dimmest point source detected) and bandwidth (fastest point source detected). Next, we tune bias settings with specific detection goals (i.e. maximum velocity and/or minimum brightness) and analyze the results. Finally, we apply newly developed low-noise bias techniques and attempt to identify general principles that can be applied universally to any EBS camera to improve performance in SDA tasks. This paper provides a baseline for understanding EBS performance characteristics and will significantly lower the entry barrier for new researchers in the field of event-based SDA. More importantly, it adds insight for optimizing EBS behavior for SDA tasks and demonstrates the absolute performance limits of current generation cameras for detecting calibrated point source targets against a dark background. Finally, this study will enable follow-on work including the development of customized denoising, detection, and tracking algorithms that consider signal response and noise statistics as a function of the selected camera and bias configuration