An anti-aliasing method for parallel rendering

We describe a parallel rendering method based on the adaptive supersampling technique to produce anti-aliased images with minimal memory consumption. Unlike traditional supersampling methods, this one does not supersample every pixel, but only those edge pixels. We consider various strategies to reduce the memory consumption in order for the method to be applicable in situations where limited or fixed amount of pre-allocated memory is available. This is a very important issue, especially in parallel rendering. We have implemented our algorithm on a parallel machine based on the message passing model. Towards the end of the paper, we present some experimental results on the memory usage and the performance of the method.published_or_final_versio

Filtering of false positive microRNA candidates by a clustering-based approach

B M C BioinformaticsBackground: MicroRNAs are small non-coding RNA gene products that play diversified roles from species to species. The explosive growth of microRNA researches in recent years proves the importance of microRNAs in the biological system and it is believed that microRNAs have valuable therapeutic potentials in human diseases. Continual efforts are therefore required to locate and verify the unknown microRNAs in various genomes. As many miRNAs are found to be arranged in clusters, meaning that they are in close proximity with their neighboring miRNAs, we are interested in utilizing the concept of microRNA clustering and applying it in microRNA computational prediction. Results: We first validate the microRNA clustering phenomenon in the human, mouse and rat genomes. There are 45.45%, 51.86% and 48.67% of the total miRNAs that are clustered in the three genomes, respectively. We then conduct sequence and secondary structure similarity analyses among clustered miRNAs, non-clustered miRNAs, neighboring sequences of clustered miRNAs and random sequences, and find that clustered miRNAs are structurally more similar to one another, and the RNAdistance score can be used to assess the structural similarity between two sequences. We therefore design a clustering-based approach which utilizes this observation to filter false positives from a list of candidates generated by a selected microRNA prediction program, and successfully raise the positive predictive value by a considerable amount ranging from 15.23% to 23.19% in the human, mouse and rat genomes, while keeping a reasonably high sensitivity. Conclusion: Our clustering-based approach is able to increase the effectiveness of currently available microRNA prediction program by raising the positive predictive value while maintaining a high sensitivity, and hence can serve as a filtering step. We believe that it is worthwhile to carry out further experiments and tests with our approach using data from other genomes and other prediction software tools. Better results may be achieved with fine-tuning of parameters. © 2008 Leung et al; licensee BioMed Central Ltd.published_or_final_versio

A computational study of the mechanism for the C6H5+CH2O reaction

The mechanism for the C6H5 + CH2O reaction has been investigated with hybrid density functional quantum-chemical and statistical theory calculations. The results reveal three possible reaction channels: (1) The abstraction reaction producing C6H6 + HCO; (2) addition to the C atom yielding C6H5CH2O and (3) addition to the O atom giving C6H5OCH2. The barriers for these 3 reactions, calculated at the B3LYP/aug-cc-pvtz level of theory using the geometry optimized with B3LYP/cc-pvdz are 0.8, 1.4 and 9.1 kcal mol(-1), respectively. The C6H5CH2O radical can fragment to form C6H5CHO + H with a barrier of 19.4 kcal mol(-1). It can also undergo isomerization reactions via two cyclic epoxy intermediates to give C6H5OCH2 with a maximum barrier of 20.4 kcal mol(-1). Transition-state theory calculations using the predicted energy barriers and structures for the rate constants of the abstraction reaction (1) lead to very good agreement with our recently measured values, while the result of RRKM calculations for the isomerization/decomposition of C6H5OCH2 to C6H5CHO + H also agrees quantitatively with available experimental data

Thickness effect on impurity-bound polaronic energy levels in a parabolic quantum dot in magnetic fields

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Mecanização agrícola - Transmissões mecânicas em máquinas agrícolas

Este trabalho destina-se a apoiar a aprendizagem de estudantes do ramo das ciências agrárias sobre aspectos relevantes das transmissões mecânicas nas máquinas agrícolas. A transmissão mecânica, formada normalmente por uma cadeia de componentes, constitui um dos modos possíveis para efectuar a transmissão de potência desde uma fonte (exemplo: a tomada-de-força do tractor) para diversos órgãos dos equipamentos agrícolas. São apresentadas as diferentes soluções de transmissão mecânica presentes nos equipamentos agrícolas, com a preocupação focada nos aspectos de manutenção, regulações permitidas e protecção do operador. O texto não está vocacionado para aspectos de dimensionamento de transmissões; contudo, faz-se a apresentação dos princípios de cinemática e dinâmica das transmissões que constitui a ferramenta necessária para se entenderem as transmissões susceptíveis de regulação por parte do operador. Será dada especial ênfase às transmissões mecânicas passíveis de regulação de semeadores de linhas e de plantadores, para efeitos de regulação da densidade de sementeira/plantação/adubação. São apresentados problemas de aplicação. Este trabalho reúne textos de anteriores edições do mesmo autor: Transmissões mecânicas (2012, 2007, 2004, 2002, 1998; 1994; 1990; 1988; 1986); Transmissões mecânicas – Equipamentos agrícolas com regulação da transmissão – Grade rotativa (2008); Transmissões mecânicas – Equipamentos agrícolas com regulação da transmissão – Semeadores de linhas monogrão e plantadores (2012, 2008); Transmissões mecânicas – Equipamentos agrícolas com regulação da transmissão – Semeadores de linhas de fluxo contínuo (2011, 2009); Transmissões mecânicas – Equipamentos agrícolas com regulação da transmissão – Semeadores de linhas, de fluxo contínuo, com transporte de sementes em corrente de ar (2012, 2008). Os textos acima indicados foram publicados periodicamente no contexto de disciplinas em cursos da Universidade de Évora, nomeadamente: - Mecânica Aplicada (1983/84 a 2003/04) - disciplina obrigatória do 3º semestre os cursos de Engenharia Agrícola e Engenharia Zootécnica; - Fundamentos de Engenharia nas Máquinas Agrícolas – (2004/05 e 2005/06) – disciplina obrigatória do 3º semestre de Engenharia Agrícola; - Tecnologia dos Equipamentos Agrícolas – (2004/05 e 2005/06) – disciplina obrigatória do 3º semestre de Engenharia Zootécnica; - Mecanização Agrícola (2006/07 até ao presente) – unidade curricular obrigatória do 3º semestre da licenciatura em Agronomia; - Princípios de Engenharia Aplicados à Ciência Animal (2006/07 até ao presente) – unidade curricular obrigatória do 1º ciclo em Ciência e Tecnologia Animal

Cyclodextrin-PEI-Tat Polymer as a Vector for Plasmid DNA Delivery to Placenta Mesenchymal Stem Cells

This study aims to modify a cyclodextrin-PEI-based polymer, PEI-β-CyD, with the TAT peptide for plasmid DNA delivery to placenta mesenchymal stem cells (PMSCs). By using the disulfide exchange between the SPDP-activated PEI-β-CyD and TAT peptide, the TAT-PEI-β-CyD polymer was fabricated and the success of this was confirmed by the presence of characteristic peaks for PEI (at δ 2.8-3.2 ppm), CyD (at δ 5.2, 3.8-4.0 and 3.4-3. 6 ppm) and TAT (at δ 1.6-1.9 and 6.8-7.2 ppm) in the 1H NMR spectrum of TAT-PEI-β-CyD. The polymer-plasmid-DNA polyplex could condense DNA at an N/P ratio of 7.0-8.0, and form nanoparticles with the size of 150.6±5.6 nm at its optimal N/P ratio (20/1). By examining the transfection efficiency and cytotoxicity of TAT-PEI-β-CyD, conjugation of the TAT peptide onto PEI-β-CyD was demonstrated to improve the transfection efficiency of PEI-β-CyD in PMSCs after 48 and 96 hours of post-transfection incubation. The viability of PEI-β-CyD-treated PMSCs was shown to be over 80% after 5 h of treatment and 24 h of post-treatment incubation. In summary, this study showed that the TAT-PEI-β-CyD polymer as a vector for plasmid DNA delivery to PMSCs and other cells warrants further investigations. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Dzyaloshinskii-Moriya Interaction and Spiral Order in Spin-orbit Coupled Optical Lattices

We show that the recent experimental realization of spin-orbit coupling in ultracold atomic gases can be used to study different types of spin spiral order and resulting multiferroic effects. Spin-orbit coupling in optical lattices can give rise to the Dzyaloshinskii-Moriya (DM) spin interaction which is essential for spin spiral order. By taking into account spin-orbit coupling and an external Zeeman field, we derive an effective spin model in the Mott insulator regime at half filling and demonstrate that the DM interaction in optical lattices can be made extremely strong with realistic experimental parameters. The rich finite temperature phase diagrams of the effective spin models for fermions and bosons are obtained via classical Monte Carlo simulations.Comment: 7 pages, 5 figure

Subitizing with Variational Autoencoders

Numerosity, the number of objects in a set, is a basic property of a given visual scene. Many animals develop the perceptual ability to subitize: the near-instantaneous identification of the numerosity in small sets of visual items. In computer vision, it has been shown that numerosity emerges as a statistical property in neural networks during unsupervised learning from simple synthetic images. In this work, we focus on more complex natural images using unsupervised hierarchical neural networks. Specifically, we show that variational autoencoders are able to spontaneously perform subitizing after training without supervision on a large amount images from the Salient Object Subitizing dataset. While our method is unable to outperform supervised convolutional networks for subitizing, we observe that the networks learn to encode numerosity as basic visual property. Moreover, we find that the learned representations are likely invariant to object area; an observation in alignment with studies on biological neural networks in cognitive neuroscience

Application of a valveless impedance pump in a liquid cooling system

2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Topological Schr\"odinger cats: Non-local quantum superpositions of topological defects

Topological defects (such as monopoles, vortex lines, or domain walls) mark locations where disparate choices of a broken symmetry vacuum elsewhere in the system lead to irreconcilable differences. They are energetically costly (the energy density in their core reaches that of the prior symmetric vacuum) but topologically stable (the whole manifold would have to be rearranged to get rid of the defect). We show how, in a paradigmatic model of a quantum phase transition, a topological defect can be put in a non-local superposition, so that - in a region large compared to the size of its core - the order parameter of the system is "undecided" by being in a quantum superposition of conflicting choices of the broken symmetry. We demonstrate how to exhibit such a "Schr\"odinger kink" by devising a version of a double-slit experiment suitable for topological defects. Coherence detectable in such experiments will be suppressed as a consequence of interaction with the environment. We analyze environment-induced decoherence and discuss its role in symmetry breaking.Comment: 7 pages, 4 figure