928 resultados para FRONTIERS
Resumo:
Botrytis species are generally considered to be aggressive, necrotrophic plant pathogens. By contrast to this general perception, however, Botrytis species could frequently be isolated from the interior of multiple tissues in apparently healthy hosts of many species. Infection frequencies reached 50% of samples or more, but were commonly less, and cryptic infections were rare or absent in some plant species. Prevalence varied substantially from year to year and from tissue to tissue, but some host species routinely had high prevalence. The same genotype was found to occur throughout a host, representing mycelial spread. B. cinerea and B. pseudocinerea are the species that most commonly occur as cryptic infections, but phylogenetically distant isolates of Botrytis were also detected, one of which does not correspond to previously described species. Sporulation and visible damage occurred only when infected tissues were stressed, or became mature or senescent. There was no evidence of cryptic infection having a deleterious effect on growth of the host, and prevalence was probably greater in plants grown in high light conditions. Isolates from cryptic infections were often capable of causing disease (to varying extents) when spore suspensions were inoculated onto their own host as well as on distinct host species, arguing against co-adaptation between cryptic isolates and their hosts. These data collectively suggest that several Botrytis species, including the most notorious pathogenic species, exist frequently in cryptic form to an extent that has thus far largely been neglected, and do not need to cause disease on healthy hosts in order to complete their life-cycles.
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Information to guide decision making is especially urgent in human dominated landscapes in the tropics, where urban and agricultural frontiers are still expanding in an unplanned manner. Nevertheless, most studies that have investigated the influence of landscape structure on species distribution have not considered the heterogeneity of altered habitats of the matrix, which is usually high in human dominated landscapes. Using the distribution of small mammals in forest remnants and in the four main altered habitats in an Atlantic forest landscape, we investigated 1) how explanatory power of models describing species distribution in forest remnants varies between landscape structure variables that do or do not incorporate matrix quality and 2) the importance of spatial scale for analyzing the influence of landscape structure. We used standardized sampling in remnants and altered habitats to generate two indices of habitat quality, corresponding to the abundance and to the occurrence of small mammals. For each remnant, we calculated habitat quantity and connectivity in different spatial scales, considering or not the quality of surrounding habitats. The incorporation of matrix quality increased model explanatory power across all spatial scales for half the species that occurred in the matrix, but only when taking into account the distance between habitat patches (connectivity). These connectivity models were also less affected by spatial scale than habitat quantity models. The few consistent responses to the variation in spatial scales indicate that despite their small size, small mammals perceive landscape features at large spatial scales. Matrix quality index corresponding to species occurrence presented a better or similar performance compared to that of species abundance. Results indicate the importance of the matrix for the dynamics of fragmented landscapes and suggest that relatively simple indices can improve our understanding of species distribution, and could be applied in modeling, monitoring and managing complex tropical landscapes.
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Aberrant alterations in glucose and lipid concentrations and their pathways of metabolism are a hallmark of diabetes. However, much less is known about alterations in concentrations of amino acids and their pathways of metabolism in diabetes. In this review we have attempted to highlight, integrate and discuss common alterations in amino acid metabolism in a wide variety of cells and tissues and relate these changes to alterations in endocrine, physiologic and immune function in diabetes.
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RpfG is a paradigm for a class of widespread bacterial two-component regulators with a CheY-like receiver domain attached to a histidine-aspartic acid-glycine-tyrosine-proline (HD-GYP) cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris pv. campestris (Xcc), a two-component system comprising RpfG and the complex sensor kinase RpfC is implicated in sensing and responding to the diffusible signaling factor (DSF), which is essential for cell-cell signaling. RpfF is involved in synthesizing DSF, and mutations of rpfF, rpfG, or rpfC lead to a coordinate reduction in the synthesis of virulence factors such as extracellular enzymes, biofilm structure, and motility. Using yeast two-hybrid analysis and fluorescence resonance energy transfer experiments in Xcc, we show that the physical interaction of RpfG with two proteins with diguanylate cyclase (GGDEF) domains controls a subset of RpfG-regulated virulence functions. RpfG interactions were abolished by alanine substitutions of the three residues of the conserved GYP motif in the HD-GYP domain. Changing the GYP motif or deletion of the two GGDEF-domain proteins reduced Xcc motility but not the synthesis of extracellular enzymes or biofilm formation. RpfG-GGDEF interactions are dynamic and depend on DSF signaling, being reduced in the rpfF mutant but restored by DSF addition. The results are consistent with a model in which DSF signal transduction controlling motility depends on a highly regulated, dynamic interaction of proteins that influence the localized expression of cyclic di-GMP.
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Background: The insecticides dichlorvos, paradichlorobenzene and naphthalene have been commonly used to eradicate pest insects from natural history collections. However, it is not known how these chemicals affect the DNA of the specimens in the collections. We thus tested the effect of dichlorvos, paradichlorobenzene and naphthalene on DNA of insects (Musca domestica) by extracting and amplifying DNA from specimens exposed to insecticides in two different concentrations over increasing time intervals. Results: The results clearly show that dichlorvos impedes both extraction and amplification of mitochondrial and nuclear DNA after relatively short time, whereas paradichlorobenzene and naphthalene do not. Conclusion: Collections treated with paradichlorobenzene and naphthalene, are better preserved concerning DNA, than those treated with dichlorvos. Non toxic pest control methods should, however, be preferred due to physical damage of specimens and putative health risks by chemicals.
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Speech perception runs smoothly and automatically when there is silence in the background, but when the speech signal is degraded by background noise or by reverberation, effortful cognitive processing is needed to compensate for the signal distortion. Previous research has typically investigated the effects of signal-to-noise ratio (SNR) and reverberation time in isolation, whilst few have looked at their interaction. In this study, we probed how reverberation time and SNR influence recall of words presented in participants' first- (L1) and second-language (L2). A total of 72 children (10 years old) participated in this study. The to-be-recalled wordlists were played back with two different reverberation times (0.3 and 1.2 s) crossed with two different SNRs (+3 dBA and +12 dBA). Children recalled fewer words when the spoken words were presented in L2 in comparison with recall of spoken words presented in L1. Words that were presented with a high SNR (+12 dBA) improved recall compared to a low SNR (+3 dBA). Reverberation time interacted with SNR to the effect that at +12 dB the shorter reverberation time improved recall, but at +3 dB it impaired recall. The effects of the physical sound variables (SNR and reverberation time) did not interact with language. © 2016 Hurtig, Keus van de Poll, Pekkola, Hygge, Ljung and Sörqvist.
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The specification of Quality of Service (QoS) constraints over software design requires measures that ensure such requirements are met by the delivered product. Achieving this goal is non-trivial, as it involves, at least, identifying how QoS constraint specifications should be checked at the runtime. In this paper we present an implementation of a Model Driven Architecture (MDA) based framework for the runtime monitoring of QoS properties. We incorporate the UML2 superstructure and the UML profile for Quality of Service to provide abstract descriptions of component-and-connector systems. We then define transformations that refine the UML2 models to conform with the Distributed Management Taskforce (DMTF) Common Information Model (CIM) (Distributed Management Task Force Inc. 2006), a schema standard for management and instrumentation of hardware and software. Finally, we provide a mapping the CIM metamodel to a .NET-based metamodel for implementation of the monitoring infrastructure utilising various .NET features including the Windows Management Instrumentation (WMI) interface.
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This Paper Tackles the Problem of Aggregate Tfp Measurement Using Stochastic Frontier Analysis (Sfa). Data From Penn World Table 6.1 are Used to Estimate a World Production Frontier For a Sample of 75 Countries Over a Long Period (1950-2000) Taking Advantage of the Model Offered By Battese and Coelli (1992). We Also Apply the Decomposition of Tfp Suggested By Bauer (1990) and Kumbhakar (2000) to a Smaller Sample of 36 Countries Over the Period 1970-2000 in Order to Evaluate the Effects of Changes in Efficiency (Technical and Allocative), Scale Effects and Technical Change. This Allows Us to Analyze the Role of Productivity and Its Components in Economic Growth of Developed and Developing Nations in Addition to the Importance of Factor Accumulation. Although not Much Explored in the Study of Economic Growth, Frontier Techniques Seem to Be of Particular Interest For That Purpose Since the Separation of Efficiency Effects and Technical Change Has a Direct Interpretation in Terms of the Catch-Up Debate. The Estimated Technical Efficiency Scores Reveal the Efficiency of Nations in the Production of Non Tradable Goods Since the Gdp Series Used is Ppp-Adjusted. We Also Provide a Second Set of Efficiency Scores Corrected in Order to Reveal Efficiency in the Production of Tradable Goods and Rank Them. When Compared to the Rankings of Productivity Indexes Offered By Non-Frontier Studies of Hall and Jones (1996) and Islam (1995) Our Ranking Shows a Somewhat More Intuitive Order of Countries. Rankings of the Technical Change and Scale Effects Components of Tfp Change are Also Very Intuitive. We Also Show That Productivity is Responsible For Virtually All the Differences of Performance Between Developed and Developing Countries in Terms of Rates of Growth of Income Per Worker. More Important, We Find That Changes in Allocative Efficiency Play a Crucial Role in Explaining Differences in the Productivity of Developed and Developing Nations, Even Larger Than the One Played By the Technology Gap
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Nos últimos anos, a economia mundial e a economia brasileira têm sofrido mudanças importantes. Fusões, aquisições e alianças estratégicas têm se multiplicado. Parte considerável destas mudanças relaciona-se com profundas alterações nos sistemas de valores de todos os segmentos industriais. A busca da competitividade relaciona-se cada vez mais com a busca do ótimo sistêmico, além das fronteiras da empresa. Neste contexto, a administração logística ganha nova dimensão, envolvendo a integração de todas as atividades ao longo da cadeia de valores e do sistema de valores, das matérias-primas ao cliente final. O objetivo desta pesquisa é (re)situar a administração logística no contexto de mudanças, enfatizando a metodologia da gestão da cadeia de suprimentos (supply chain management).
Resumo:
These papers deal with some main topics in new institutional economics. I make a survey of the literature, considering the contributions presented by Buchanan, Tullock, Coase, Olson and North to modern approaches to political economy. In fact, the first article is very simple. It should be used as support material in economics seminars at undergraduated level. The second one is an academic paper and deals basically with the contributions of public choice theory to the political understanding.
Resumo:
A rápida evolução da Internet, permitindo a troca de mercadorias e serviços, pode ser comparada ao período da revolução industrial. A ausência total de fronteiras na Internet suscita tanto a admiração quanto o receio. Na verdade, o crescimento da Internet baseia-se em três fatores distintos e complementares: (i) o comercial; (ii) o tecnológico; e, (iii) o jurídico. A Internet não tem um comando jurídico uniformizado e harmonizado. Daí resulta que ela se traduz num mosaico organizacional que, hoje, está permitindo o seu funcionamento. A Internet é independente, entretanto não pode subsistir sem a influência de um sistema legal. De fato, as leis nacionais de um determinado país tem vocação a se aplicar às transações comerciais celebradas via Internet, dada a inexistência de uma regulamentação única e abrangente. Contudo, a aplicação não poderá ser imediata, adaptações serão necessárias para atender aos novos modelos jurídicos utilizados na Internet. Esta pesquisa é a primeira parte de um estudo mais amplo: a influência da Internet no direito brasileiro. Por tratar-se de um primeiro estudo bibliográfico, foram examinadas as principais áreas do direito que estão sendo influenciadas pelo desenvolvimento rápido e crescente da Internet. É, portanto, a primeira etapa deste estudo a pesquisa bibliográfica, propriamente dita. Nessa etapa, foram identificadas e comparadas as posições doutrinárias tanto de países sob a influência do sistema jurídico de common law como do romano-germânico. A partir de então, na segunda etapa, foram classificados os tópicos de maior interesse para a doutrina, através de palavras-chave. Partindo assim do presente estudo, o estudo mais amplo pretenderá delinear os alicerces de uma proposta jurídica comparada, entre os sistemas de common law e romano germânico, para então examinar a influência da Internet no direito brasileiro.
Resumo:
As relações comerciais observadas no início do século passado se baseavam no atendimento personalizado, em que cada cliente era recebido pessoalmente pelo dono da loja, que por sua vez conhecia a clientela e suas principais necessidades. Com a massificação da produção e o surgimento dos grandes magazines e shopping centers, o foco das empresas se voltou para produtos e serviços, futor que promoveu o distanciamento das relações com os clientes, tornando-os ilustres desconhecidos para as empresas. Quase um século depois, o advento da Internet prOpICIOU um processo de reaproximação entre empresas e clientes, eis que as fronteiras geográficas começaram a desaparecer, as empresas locais começaram a atuar e concorrer mundialmente através da web, o mercado apresentou-se mais competitivo e os clientes conquistaram maior poder de escolha e se tornaram mais voláteis. Neste contexto de grandes massas, surge o CRM contemplando um conjunto de estratégias que permeiam toda a organização, como por exemplo, a revisão dos processos de negócios, a mudança da cultura com o foco no cliente, a automação dos serviços de marketing, vendas e atendimento, a disponibilização de multi-canais de contato com o cliente e a integração das bases de dados com os canais de interação. As estratégias de CRM, com base na revisão dos processos de negócios, na mudança da cultura organizacional e na infra-estrutura tecnológica, objetivam estabelecer relações individualizadas com uma imensa massa de clientes. Neste sentido, esse trabalho de pesquisa intenciona aprofundar os conhecimentos sobre influência do CRM na fidelização do cliente.