902 resultados para Lai
Resumo:
Within-field variation in sugar beet yield and quality was investigated in three commercial sugar beet fields in the east of England to identify the main associated variables and to examine the possibility of predicting yield early in the season with a view to spatially variable management of sugar beet crops. Irregular grid sampling with some purposively-located nested samples was applied. It revealed the spatial variability in each sugar beet field efficiently. In geostatistical analyses, most variograms were isotropic with moderate to strong spatial dependency indicating a significant spatial variation in sugar beet yield and associated growth and environmental variables in all directions within each field. The Kriged maps showed spatial patterns of yield variability within each field and visual association with the maps of other variables. This was confirmed by redundancy analyses and Pearson correlation coefficients. The main variables associated with yield variability were soil type, organic matter, soil moisture, weed density and canopy temperature. Kriged maps of final yield variability were strongly related to that in crop canopy cover, LAI and intercepted solar radiation early in the growing season, and the yield maps of previous crops. Therefore, yield maps of previous crops together with early assessment of sugar beet growth may make an early prediction of within-field variability in sugar beet yield possible. The Broom’s Barn sugar beet model failed to account for the spatial variability in sugar yield, but the simulation was greatly improved when corrected for early canopy development cover and when the simulated yield was adjusted for weeds and plant population. Further research to optimize inputs to maximise sugar yield should target the irrigation and fertilizing of areas within fields with low canopy cover early in the season.
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European beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.) are two of the most ecologically and economically important forest tree species in Europe. These two species co-occur in many locations in Europe, leading to direct competition for canopy space. Foliage characteristics of two naturally regenerated pure stands of beech and spruce with fully closed canopies were contrasted to assess the dynamic relationship between foliage adaptability to shading, stand LAI and tree growth. We found that individual leaf size is far more conservative in spruce than in beech. Individual leaf and needle area was larger at the top than at the bottom of the canopy in both species. Inverse relationship was found for specific leaf area (SLA), highest SLA values were found at lowest light availability under the canopy. There was no difference in leaf area index (LAI) between the two stands, however LAI increased from 10.8 to 14.6 m2m-2 between 2009 and 2011. Dominant trees of both species were more efficient in converting foliage mass or area to produce stem biomass, although this relationship changed with age and was species-specific. Overall, we found larger foliage plasticity in beech than in spruce in relation to light conditions, indicating larger capacity to exploit niche openings.
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Growing evidence points toward a critical role for early (prenatal) atypical neurodevelopmental processes in the aetiology of autism spectrum condition (ASC). One such process that could impact early neural development is inflammation. We review the evidence for atypical expression of molecular markers in the amniotic fluid, serum, cerebrospinal fluid (CSF), and the brain parenchyma that suggest a role for inflammation in the emergence of ASC. This is complemented with a number of neuroimaging and neuropathological studies describing microglial activation. Implications for treatment are discussed.
Resumo:
The personalised conditioning system (PCS) is widely studied. Potentially, it is able to reduce energy consumption while securing occupants’ thermal comfort requirements. It has been suggested that automatic optimised operation schemes for PCS should be introduced to avoid energy wastage and discomfort caused by inappropriate operation. In certain automatic operation schemes, personalised thermal sensation models are applied as key components to help in setting targets for PCS operation. In this research, a novel personal thermal sensation modelling method based on the C-Support Vector Classification (C-SVC) algorithm has been developed for PCS control. The personal thermal sensation modelling has been regarded as a classification problem. During the modelling process, the method ‘learns’ an occupant’s thermal preferences from his/her feedback, environmental parameters and personal physiological and behavioural factors. The modelling method has been verified by comparing the actual thermal sensation vote (TSV) with the modelled one based on 20 individual cases. Furthermore, the accuracy of each individual thermal sensation model has been compared with the outcomes of the PMV model. The results indicate that the modelling method presented in this paper is an effective tool to model personal thermal sensations and could be integrated within the PCS for optimised system operation and control.
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It has been postulated that autism spectrum disorder is underpinned by an ‘atypical connectivity’ involving higher-order association brain regions. To test this hypothesis in a large cohort of adults with autism spectrum disorder we compared the white matter networks of 61 adult males with autism spectrum disorder and 61 neurotypical controls, using two complementary approaches to diffusion tensor magnetic resonance imaging. First, we applied tract-based spatial statistics, a ‘whole brain’ non-hypothesis driven method, to identify differences in white matter networks in adults with autism spectrum disorder. Following this we used a tract-specific analysis, based on tractography, to carry out a more detailed analysis of individual tracts identified by tract-based spatial statistics. Finally, within the autism spectrum disorder group, we studied the relationship between diffusion measures and autistic symptom severity. Tract-based spatial statistics revealed that autism spectrum disorder was associated with significantly reduced fractional anisotropy in regions that included frontal lobe pathways. Tractography analysis of these specific pathways showed increased mean and perpendicular diffusivity, and reduced number of streamlines in the anterior and long segments of the arcuate fasciculus, cingulum and uncinate—predominantly in the left hemisphere. Abnormalities were also evident in the anterior portions of the corpus callosum connecting left and right frontal lobes. The degree of microstructural alteration of the arcuate and uncinate fasciculi was associated with severity of symptoms in language and social reciprocity in childhood. Our results indicated that autism spectrum disorder is a developmental condition associated with abnormal connectivity of the frontal lobes. Furthermore our findings showed that male adults with autism spectrum disorder have regional differences in brain anatomy, which correlate with specific aspects of autistic symptoms. Overall these results suggest that autism spectrum disorder is a condition linked to aberrant developmental trajectories of the frontal networks that persist in adult life.
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Human Body Thermoregulation Models have been widely used in the field of human physiology or thermal comfort studies. However there are few studies on the evaluation method for these models. This paper summarises the existing evaluation methods and critically analyses the flaws. Based on that, a method for the evaluating the accuracy of the Human Body Thermoregulation models is proposed. The new evaluation method contributes to the development of Human Body Thermoregulation models and validates their accuracy both statistically and empirically. The accuracy of different models can be compared by the new method. Furthermore, the new method is not only suitable for the evaluation of Human Body Thermoregulation Models, but also can be theoretically applied to the evaluation of the accuracy of the population-based models in other research fields.
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In vivo, enzymatic reduction of some protein disulfide bonds, allosteric disulfide bonds, provides an important level of structural and functional regulation. The free cysteine residues generated can be labeled by maleimide reagents, including biotin derivatives, allowing the reduced protein to be detected or purified. During the screening of monoclonal antibodies for those specific for the reduced forms of proteins, we isolated OX133, a unique antibody that recognizes polypeptide resident, N-ethylmaleimide (NEM)-modified cysteine residues in a sequence-independent manner. OX133 offers an alternative to biotin-maleimide reagents for labeling reduced/alkylated antigens and capturing reduced/alkylated proteins with the advantage that NEM-modified proteins are more easily detected in mass spectrometry, and may be more easily recovered than is the case following capture with biotin based reagents.
An improved estimate of leaf area index based on the histogram analysis of hemispherical photographs
Resumo:
Leaf area index (LAI) is a key parameter that affects the surface fluxes of energy, mass, and momentum over vegetated lands, but observational measurements are scarce, especially in remote areas with complex canopy structure. In this paper we present an indirect method to calculate the LAI based on the analyses of histograms of hemispherical photographs. The optimal threshold value (OTV), the gray-level required to separate the background (sky) and the foreground (leaves), was analytically calculated using the entropy crossover method (Sahoo, P.K., Slaaf, D.W., Albert, T.A., 1997. Threshold selection using a minimal histogram entropy difference. Optical Engineering 36(7) 1976-1981). The OTV was used to calculate the LAI using the well-known gap fraction method. This methodology was tested in two different ecosystems, including Amazon forest and pasturelands in Brazil. In general, the error between observed and calculated LAI was similar to 6%. The methodology presented is suitable for the calculation of LAI since it is responsive to sky conditions, automatic, easy to implement, faster than commercially available software, and requires less data storage. (C) 2008 Elsevier B.V. All rights reserved.
Resumo:
PHENIX has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c(2) in p + p collisions at root s = 200 GeV. The contributions from light meson decays to e(+)e(-) pairs have been determined based on measurements of hadron production cross sections by PHENIX. Within the systematic uncertainty of similar to 20% they account for all e(+)e(-) pairs in the mass region below similar to 1 GeV/c(2). The e(+)e(-) pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) pb. which is consistent with QCD calculations and measurements of single leptons by PHENIX. (C) 2008 Elsevier BV. All rights reserved.
Resumo:
Vertical stream bed erosion has been studied routinely and its modeling is getting widespread acceptance. The same cannot be said with lateral stream bank erosion since its measurement or numerical modeling is very challenging. Bank erosion, however, can be important to channel morphology. It may contribute significantly to the overall sediment budget of a stream, is a leading cause of channel migration, and is the cause of major channel maintenance. However, combined vertical and lateral channel evolution is seldom addressed. In this study, a new geofluival numerical model is developed to simulate combined vertical and lateral channel evolution. Vertical erosion is predicted with a 2D depth-averaged model SRH-2D, while lateral erosion is simulated with a linear retreat bank erosion model developed in this study. SRH-2D and the bank erosion model are coupled together both spatially and temporally through a common mesh and the same time advancement. The new geofluvial model is first tested and verified using laboratory meander channels; good agreement are obtained between predicted bank retreat and measured data. The model is then applied to a 16-kilometer reach of Chosui River, Taiwan. Vertical and lateral channel evolution during a three-year period (2004 to 2007) is simulated and results are compared with the field data. It is shown that the geofluvial model correctly captures all major erosion and deposition patterns. The new model is shown to be useful for identifying potential erosion sites and providing information for river maintenance planning.
Resumo:
Na América Latina, um vasto legado de regimes militares tem contribuído para o fortalecimento de uma cultura de sigilo nos governos. Além da defesa da pátria contra a ameaça comunista, a maioria destes golpes se deveu a um senso de dever das Forças Armadas em preservar o Estado. Deste ponto de vista, os próprios militares seriam os mais qualificados para determinar quando e como intervir na ordem política interna. No entanto, justificar a intervenção militar na ordem política interna é sempre um empreendimento repleto de contradições e riscos graves para a liberdade. Este contexto levou os estudiosos e autoridades a repensarem o controle civil sobre os militares, e a redefinirem os papéis das forças armadas. Neste processo de consolidação da democracia, os militares ainda mantêm alguns poderes políticos e de veto dentro dos governos civis. O controle civil democrático das Forças Armadas na América Latina enfrenta a falta de incentivos políticos para os civis a se envolverem e se especializarem no assunto, já que não há ameaças internas, quer externas observadas. De fato, a região tem sido considerada como uma "zona de paz", onde os esforços diplomáticos prevaleceriam sobre conflitos armados. A promulgação de leis de acesso à informação pública (LAI) abre uma maneira inteiramente nova de escrutínio público – uma democracia monitorial, que afeta diretamente a autonomia militar e sua cultura organizacional. No estudo do surgimento e da força legal das LAI na América Latina, as relações entre civis e militares não foram consideradas em profundidade como um fator influente. Buscou-se traçar uma relação entre, por um lado, a existência de LAI, a data de aprovação da LAI e sua força geral e exceções, e por outro lado, as relações civis-militares na América Latina. Um número considerável de países suporta que as relações civis-militares influenciam a regulamentação das exceções e o momento em que a lei foi aprovada. Há uma tendência geral na América Latina a adotar LAI fracas na regulamentação de exceções. Também foi feito um estudo de caso do Brasil, país muito representativo da influência militar na política. Concluiu-se que as relações entre civis e militares no Brasil foram um fator de grande influência na aprovação final da LAI no país. Este estudo contribui para a construção de uma ponte entre as agendas de pesquisa de transparência e de relações civis-militares, com várias possibilidades de estudos de casos comparados.
Resumo:
Transparência é fundamental para promover participação popular, accountability e a profissionalização do setor público. Essas questões, no âmbito da educação, são urgentes no Brasil. As instituições federais de ensino superior, por força da Lei de Acesso à Informação (LAI), estão obrigadas, como tantas outras instituições públicas, a apresentarem informações mínimas aos cidadãos em seus portais eletrônicos. Essas informações estão vinculadas à transparência ativa, ou seja, a apresentação de forma clara, objetiva e espontânea, sem necessidade de requerimentos com preenchimento de formulários. Entretanto, algumas universidades federais não se prepararam adequadamente para o atendimento à lei e apresentam problemas permanentes de gestão ao longo dos anos, o que as impede de promover a transparência necessária. Este trabalho analisa o cumprimento de obrigações vinculadas à transparência ativa em universidades federais – estipuladas pelo oitavo artigo da lei 12.527 – com o objetivo de verificar como estão essas organizações frente aos princípios de transparência e eficiência estipulados ao governo federal. Foram analisadas 53 universidades federais, aplicando-se metodologia que avaliou conteúdos de sítios eletrônicos com base no determinado pela LAI.