Curvature scale space corner detector with adaptive threshold and dynamic region of support

Corners play an important role in object identification methods used in machine vision and image processing systems. Single-scale feature detection finds it hard to detect both fine and coarse features at the same time. On the other hand, multi-scale feature detection is inherently able to solve this problem. This paper proposes an improved multi-scale corner detector with dynamic region of support, which is based on Curvature Scale Space (CSS) technique. The proposed detector first uses an adaptive local curvature threshold instead of a single global threshold as in the original and enhanced CSS methods. Second, the angles of corner candidates are checked in a dynamic region of support for eliminating falsely detected corners. The proposed method has been evaluated over a number of images and compared with some popular corner detectors. The results showed that the proposed method offers a robust and effective solution to images containing widely different size features.published_or_final_versio

Characterization of low-molecular-weight glutenin subunit genes at Glu-B3 and GluD3 loci and development of functional markers in common wheat

Tese de doutoramento em Engenharia Civil, no ramo de Urbanismo, Ordenamento do Território e Transportes, apresentada ao Departamento de Engenharia Civil da Universidade de Coimbra.O ruído provocado pelo tráfego rodoviário, pelas suas graves consequências a diferentes níveis e pelas proporções crescentes de populações afetadas, é um problema que vem sendo considerado, em cada vez mais países, como uma das prioridades na definição de políticas de garantia das condições de bem-estar e saúde pública. Historicamente, diferentes abordagens têm sido adotadas para mitigar esse problema. Entre aquelas habitualmente associadas à Engenharia Civil, pode-se dizer que a utilização de barreiras acústicas será aquela que maior divulgação tem tido. Mais recentemente vem-se observando um interesse crescente no uso, em alternativa ou em complemento às barreiras, de pavimentos rodoviários que conduzam a menores níveis de ruído na sua origem, sendo ainda de referir a aplicação de elementos com maiores capacidades de isolamento sonoro em edifícios submetidos a tal ruído, em regra como última opção. Na presente tese, após uma síntese referente a diferentes aspetos do ruído de origem rodoviária e do reconhecimento da importância da sua caracterização, no contexto das soluções de pavimentação rodoviária mais correntes a nível nacional, para poder justificar determinadas opções no sentido da sua mitigação, foi dada especial atenção à análise de barreiras acústicas de um tipo relativamente inovador, concretizadas por estruturas resultantes da utilização, numa organização geométrica periódica, de elementos cilíndricos verticais, conhecidas como ‘cristais sónicos’. Sendo uma área de estudo cujo início remonta ao final da década de 1980, a sua aplicação no contexto de barreiras acústicas rodoviárias começou a ser sugerida já no início deste século, tendo, desde então, vindo a merecer o interesse de diversos investigadores com trabalhos relativos a diferentes aspetos de tal aplicação. Tal interesse deve-se à particularidade de, em tais estruturas, a propagação de ondas sonoras poder ser afetada, e mesmo impedida, em determinadas bandas de frequência (conhecidas por ‘band gaps’), em função das propriedades físicas e geométricas dos elementos que as consubstanciam e da sua organização periódica. Na medida em que uma escolha criteriosa daquelas propriedades permitirá ajustar o desempenho acústico de barreiras deste tipo, avaliado pela atenuação sonora proporcionada, às características espectrais específicas de determinado ruído incidente, tais barreiras poderão, assim, configurar uma estratégia de atenuação seletiva do ruído de origem rodoviária. No âmbito deste trabalho, pretendeu-se estudar tal possibilidade, partindo da resolução da equação de Helmholtz de modo a analisar de que forma a propagação de ondas sonoras pode ser afetada pela presença de tais estruturas. Para o efeito, foi proposta uma metodologia de cálculo para prever o desempenho acústico de cristais sónicos, de modo a simular os fenómenos de dispersão acústica, ou outros, que determinados atributos concretos dessas estruturas poderão desencadear. O principal aspeto inovador desta tese prende-se com a utilização de uma técnica de modelação numérica, o Método das Soluções Fundamentais, aplicada à avaliação do desempenho de tais barreiras, julgando-se poder, desta forma, apresentar um contributo importante na modelação eficiente deste tipo de estruturas. A validação da modelação proposta, realizada por comparação de resultados relativos à atenuação sonora proporcionada, quer com outros métodos numéricos quer com recurso a medições experimentais num modelo reduzido, revelou um muito bom ajustamento entre os vários resultados. Tendo-se, ainda, analisado a possibilidade de otimizar o referido desempenho dos cristais sónicos enquanto soluções de barreiras acústicas rodoviárias, alterando alguns dos seus parâmetros definidores através da variação das suas características orgânicas, pôde-se concluir que os resultados obtidos sugerem que tal poderá, de facto, ser levado a cabo utilizando a modelação proposta, o que abre todo o quadro de resolução do problema do ruído rodoviário junto à ocupação humana a uma forma menos perturbadora da envolvente paisagística do que a proporcionada pelas barreiras acústicas tradicionais.Road traffic noise, due to its severe consequences at different levels and the increasing proportions of affected populations, is a problem that is being considered, at an increasing number of countries, as a priority in defining welfare and public health related policies. Historically, different approaches have been taken to mitigate this problem. Among those most commonly associated with civil engineering, the use of noise barriers is arguably the one that has seen a more widespread dissemination. More recently an increasing interest in the use of road surfaces for traffic noise control at its source, as an alternative to or together with barriers, has been witnessed, and the use of façade sound insulation solutions in dwellings affected by such noise, generally as a last resource measure, should also be mentioned. In this thesis, after an overview regarding the different aspects of road traffic noise and acknowledgment of the importance of its characterization, in the context of most commonly used road surfacing solutions at national level, in order to justify the choices of specific measures for its mitigation, special attention was given to the analysis of a somewhat innovative type of acoustic barriers, known as 'sonic crystals', attained by structures presenting periodic arrays of vertical cylindrical elements, or scatterers. Being a field of study whose beginning dates back to the late 1980s, its application as road noise barriers was suggested at the beginning of this century and, since then, it has interested many researchers, working on different aspects of such application. Such interest is due to a feature, in such structures, where the sound propagation can be affected and even prohibited, in some frequency ranges (known as "band gaps"), depending both on the physical and geometric properties of the elements which consubstantiate it and on the periodicity of the array. To the extent that a specific combination of those properties will bring up the possibility to tune the acoustical performance of sonic crystals, measured by its insertion loss, to the specific spectral characteristics of a particular incident noise, these barriers can therefore configure a strategy in order to implement a selective attenuation of road traffic noise. In this work such possibilities were studied, based on the use of the Helmholtz equation in order to analyze how the propagation of sound waves can be affected by the presence of such structures. To this end, a methodology was proposed to predict the acoustic performance of sonic crystals, in order to simulate the acoustic dispersion and other phenomena, which certain specific attributes of those structures are likely to produce. The validation of the proposed model was carried out by comparing the insertion loss results it provided, with those delivered by either other numerical methods or by experimental measurements on a scale model, which revealed a very good fit between the various results. Having also examined the prospect of optimizing the performance of such sonic crystals when used as road noise barriers solutions, changing some of its defining parameters by varying their organic characteristics, it was concluded that the obtained results suggest that this may, in fact, be carried out by using the proposed model, which opens up the whole framework of solving the problem of road noise next to human settlement at a less disruptive form of the surrounding landscape than is provided by using traditional acoustic barriers.Fundação para a Ciência e Tecnologi

Interplay between topological insulators and superconductors

Topological insulators are insulating in the bulk but possess metallic surface states protected by time-reversal symmetry. Here, we report on a detailed electronic transport study in high-quality Bi 2Se 3 topological insulator thin films contacted by superconducting (In, Al, and W) electrodes. The resistance of the film shows an abrupt and significant upturn when the electrodes become superconducting. In turn, the Bi 2Se 3 film greatly weakens the superconductivity of the electrodes, significantly reducing both their transition temperatures and their critical fields. A possible interpretation of these results is that the superconducting electrodes are accessing the surface states and the experimental results are consequences of the interplay between the Cooper pairs of the electrodes and the spin-polarized current of the surface states in Bi 2Se 3. © 2012 American Physical Society.published_or_final_versio

Robust Delay-Dependent Load Frequency Control of Wind Power System Based on a Novel Reconstructed Model

IEEE This article presents a novel reconstructed model for the delayed load frequency control (LFC) schemes considering wind power, which aims to improve the computational efficiency for PID controllers while retaining their dynamic performance. Via fully exploiting system states influenced by time delays directly, this novel reconstructed method is proposed with a controller isolated. Hence, when the PID controllers are unknown, the stability criterion based on this model can resolve controller gains with less time consumed. For given PID gains, this model can be employed to establish criteria for stability analysis, which can realize the tradeoff between the calculation accuracy and efficiency. The case study is first based on a two-area traditional LFC system to validate the merits of a novel reconstructed model, including accurately estimating the influence of time delay on system frequency stability with increased computational capability. Then, under traditional and deregulated environments, case studies are carried out on the two-area and three-area schemes, respectively. Through the novel reconstructed model, the efficiency of obtaining controller parameters is highly improved while their robustness against the random wind power, tie-line power changes, inertial reductions, and time delays remains almost unchanged

Cyclic dermal BMP signalling regulates stem cell activation during hair regeneration

In the age of stem cell engineering it is critical to understand how stem cell activity is regulated during regeneration. Hairs are mini-organs that undergo cyclic regeneration throughout adult life1, and are an important model for organ regeneration. Hair stem cells located in the follicle bulge2 are regulated by the surrounding microenvironment, or niche3. The activation of such stem cells is cyclic, involving periodic -catenin activity4, 5, 6, 7. In the adult mouse, regeneration occurs in waves in a follicle population, implying coordination among adjacent follicles and the extrafollicular environment. Here we show that unexpected periodic expression of bone morphogenetic protein 2 (Bmp2) and Bmp4 in the dermis regulates this process. This BMP cycle is out of phase with the WNT/-catenin cycle, thus dividing the conventional telogen into new functional phases: one refractory and the other competent for hair regeneration, characterized by high and low BMP signalling, respectively. Overexpression of noggin, a BMP antagonist, in mouse skin resulted in a markedly shortened refractory phase and faster propagation of the regenerative wave. Transplantation of skin from this mutant onto a wild-type host showed that follicles in donor and host can affect their cycling behaviours mutually, with the outcome depending on the equilibrium of BMP activity in the dermis. Administration of BMP4 protein caused the competent region to become refractory. These results show that BMPs may be the long-sought 'chalone' inhibitors of hair growth postulated by classical experiments. Taken together, results presented in this study provide an example of hierarchical regulation of local organ stem cell homeostasis by the inter-organ macroenvironment. The expression of Bmp2 in subcutaneous adipocytes indicates physiological integration between these two thermo-regulatory organs. Our findings have practical importance for studies using mouse skin as a model for carcinogenesis, intra-cutaneous drug delivery and stem cell engineering studies, because they highlight the acute need to differentiate supportive versus inhibitory regions in the host skin

Architecture of Pol II(G) and molecular mechanism of transcription regulation by Gdown1.

Tight binding of Gdown1 represses RNA polymerase II (Pol II) function in a manner that is reversed by Mediator, but the structural basis of these processes is unclear. Although Gdown1 is intrinsically disordered, its Pol II interacting domains were localized and shown to occlude transcription factor IIF (TFIIF) and transcription factor IIB (TFIIB) binding by perfect positioning on their Pol II interaction sites. Robust binding of Gdown1 to Pol II is established by cooperative interactions of a strong Pol II binding region and two weaker binding modulatory regions, thus providing a mechanism both for tight Pol II binding and transcription inhibition and for its reversal. In support of a physiological function for Gdown1 in transcription repression, Gdown1 co-localizes with Pol II in transcriptionally silent nuclei of early Drosophila embryos but re-localizes to the cytoplasm during zygotic genome activation. Our study reveals a self-inactivation through Gdown1 binding as a unique mode of repression in Pol II function

Acute WNT signalling activation perturbs differentiation within the adult stomach and rapidly leads to tumour formation

A role for WNT signalling in gastric carcinogenesis has been suggested due to two major observations. First, patients with germline mutations in adenomatous polyposis coli (APC) are susceptible to stomach polyps and second, in gastric cancer, WNT activation confers a poor prognosis. However, the functional significance of deregulated WNT signalling in gastric homoeostasis and cancer is still unclear. In this study we have addressed this by investigating the immediate effects of WNT signalling activation within the stomach epithelium. We have specifically activated the WNT signalling pathway within the mouse adult gastric epithelium via deletion of either glycogen synthase kinase 3 (GSK3) or APC or via expression of a constitutively active β-catenin protein. WNT pathway deregulation dramatically affects stomach homoeostasis at very short latencies. In the corpus, there is rapid loss of parietal cells with fundic gland polyp (FGP) formation and adenomatous change, which are similar to those observed in familial adenomatous polyposis. In the antrum, adenomas occur from 4 days post-WNT activation. Taken together, these data show a pivotal role for WNT signalling in gastric homoeostasis, FGP formation and adenomagenesis. Loss of the parietal cell population and corresponding FGP formation, an early event in gastric carcinogenesis, as well as antral adenoma formation are immediate effects of nuclear β-catenin translocation and WNT target gene expression. Furthermore, our inducible murine model will permit a better understanding of the molecular changes required to drive tumourigenesis in the stomach

Quantum Point Contacts and Coherent Electron Focusing

I. Introduction II. Electrons at the Fermi level III. Conductance quantization of a quantum point contact IV. Optical analogue of the conductance quantization V. Classical electron focusing VI. Electron focusing as a transmission problem VII. Coherent electron focusing (Experiment, Skipping orbits and magnetic edge states, Mode-interference and coherent electron focusing) VIII. Other mode-interference phenomenaComment: #3 of a series of 4 legacy reviews on QPC'