Realization of Pan Jiazheng′s extremum principle with optimization methods

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

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

Effects of Sowing Date and Phosphorus Fertiliser Application on Winter Survival of Lucerne cv. Aohan in the Northern Semi-Arid Region of China

In the northern semi-arid region of China, winter survival is always a limiting factor for lucerne production, because low temperatures and a dry climate in winter (Zhou et al., 1993; Ma, 2000; Sun & Gui, 2001; Sun et al., 2003). An experiment was conducted to find an appropriate sowing date and P application rate in order to improve lucerne winter survival

Plastic properties and microstructure evolution of 20CrMoA steel during warm deformation

The plastic properties and microstructure evolution of 20CrMoA steel was analyzed at 600-750 °C and strain rate of 0,01-10 s-1.The result reveals that the deformation behavior is hardening followed by softening at low strain rates(0,01 s-1 and 0,1 s-1), but hardening is dominant in the whole deformation process at high strain rates(1 s-1and 10 s-1) and low temperature(600 °C and 650 °C). The strain rate sensitivity exponent increases with the increasing deformation temperature except for 650 °C and high strain rate. The spheroidization mechanism of cementite is the mechanical fracture and the dissolution of cementite particles. At 700 °C, spheroidized particles are finer and their distribution is more uniform than that at 750 °C

Influence of silencing the MC4R gene by lentivirusmediated RNA interference in bovine fibroblast cells

Melanocortin receptor 4 (MC4R) is a key element in the mechanisms used to regulate both aspects of keeping the balance between energy uptake and energy expenditure. MC4R was knocked down by lentivirus-mediated shRNA expressing plasmids, which were controlled by the U6 promoter in bovine fibroblast cells, and the expression of MC4R was examined by the real time-PCR and Western blot analysis. Real time-PCR analysis was used to characterize the expression of Leptin, POMC, AGRP, MC3R and NPY gene. The relative genes [leptin, proopiomelanocortin (POMC), agouti-related peptide (AGRP), MC3R and neuropeptide Y (NPY)] expression level seemed to be closely associated with the MC4R gene in bovine fibroblast cell lines (BFCs). The levels of both MC4R mRNA and protein were significantly reduced by RNA interference (RNAi) mediated knockdown of MC4R in BFCs cells transfected with plasmid-based MC4R-specific shRNAs. The finding of this study demonstrated that vector based siRNA expression systems were an efficient approach to the knockdown of the MC4R gene expression in bovine fibroblast cells and they provided a new molecular basis for understanding the relationship of MC4R and other genes, which were responsible for the regulation of energy homeostasis by the melanocortin system.Key words: Melanocortin receptor 4 (MC4R), RNAi, bovine fibroblast cells, energy homeostasis

Immune cascades in human intervertebral disc: the pros and cons

The unique structural hallmark of the intervertebral disc has made its central composition, the nucleus pulposus (NP), excluded from the immunologic tolerance. Consequently, the intervertebral disc is identified as an immune-privileged organ. Traditionally, local detrimental immune activities caused by NP at the lesion sites of the disc are noted as a significant factor contributing to disc degeneration. However, given the beneficial activities of immune cells in other immune-privileged sites on basis of current evidence, the degenerate disc might need the assistance of a subpopulation of immune cells to restore its structure and lessen inflammation. In addition, the beneficial impact of immune cells can be seen in the absorption of the herniated NP, which is an important factor causes the mechanical compression of nerve roots. Consequently, a modulated immune network in degenerate disc is essential for the restoration of this immune-privileged organ. Until now, the understandings of immune response in disc degeneration still rest on the harmful aspect. Further studies are needed to explore its beneficial influence. Accordingly, there are no absolutely the pros and cons in terms of immune reactions caused by NP.published_or_final_versio

Solar influenced late Holocene temperature changes on the northern Tibetan Plateau

Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions, in order to further understand the mechanisms of past climate variability. Yet, the global coverage of existing temperature records is still limited, especially for some key regions like the Tibetan Plateau and for earlier times including the Medieval Warm Period (MWP). Here we present decadally-resolved, alkenone-based, temperature records from two lakes on the northern Tibetan Plateau. Characterized by marked temperature variability, our records provide evidence that temperatures during the MWP were slightly higher than the modern period in this region. Further, our temperature reconstructions, within age uncertainty, can be well correlated with solar irradiance changes, suggesting a possible link between solar forcing and natural climate variability, at least on the northern Tibetan Plateau. © 2013 The Author(s).published_or_final_versio