Página 1 dos resultados de 138 itens digitais encontrados em 0.019 segundos

Painéis estruturais utilizando madeira roliça de pequeno diâmetro para habitação social: desenvolvimento do produto; Structural panel project for social housing making use of small diameter round-wood: product development

Partel, Priscila Maria Penalva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/06/2006 Português
Relevância na Pesquisa
46.8216%
A tese buscou identificar, a partir da análise da cadeia produtiva de produtos de base florestal, as oportunidades para aproveitamento da madeira roliça dos gêneros Eucalyptus e Pinus, com pequeno diâmetro, para produção de painéis estruturais de vedação destinados a habitação social. A madeira como material construtivo renovável, e segundo as dimensões da sustentabilidade, econômica e ambiental, apresenta as seguintes potencialidades: plantio e manejo florestal sustentável; adequação a diversos sistemas estruturais e construtivos; baixos consumos de energia e baixa geração de resíduos no processo de produção; desmontagem e aproveitamento dos resíduos no processo de transformação. O método adotado para o desenvolvimento do produto painel foi baseado, na análise e aperfeiçoamentos sucessivos a partir da avaliação dos dados coletados na fase experimental (processo de produção). As variáveis consideradas foram: facilidade de produção (homem/minuto, hora/equipamento e ferramentas), volume de resíduos gerados no processamento, custos e facilidade de montagem do painel. Os critérios adotados na avaliação de desempenho técnico foram: estrutural, estanqueidade visual e durabilidade. Na avaliação da sustentabilidade ambiental foram: uso de materiais de fontes renováveis; baixo consumo energético; redução de resíduos gerados. A sustentabilidade econômica foi avaliada considerando os critérios de: facilidade de produção; facilidade de montagem; produção em escala; baixos custos dos materiais empregados. Foram desenvolvidos e avaliados 10 projetos segundo os critérios considerados...

Diagnóstico da mecanização em uma região produtora de grãos; Farm machinery utilization in a row-crop producer region

Gimenez, Leandro Maria
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/09/2006 Português
Relevância na Pesquisa
37.685781%
O emprego da mecanização no Brasil iniciou-se praticamente a partir dos anos 60 com a instalação da indústria nacional de tratores acompanhada pela de máquinas e implementos. Com isso houve uma expansão acelerada no uso da mecanização agrícola sendo ela praticamente indispensável nos dias atuais. Embora com benefícios inquestionáveis, a mecanização foi influenciada pela tecnologia exógena no projeto de fabricação e na utilização de técnicas inadequadas como o preparo convencional do solo, técnica essa associada a problemas de erosão. Dado o caráter recente da mecanização, existe uma carência de informações básicas sobre os seus indicadores permitindo a análise da adequação dos equipamentos nas propriedades. Considerando-se o contexto da mecanização, as técnicas adotadas e a ausência de índices, este trabalho teve como objetivo a realização de um diagnóstico quanto à posse e uso de sistemas mecanizados em unidades agrícolas de uma região produtora de grãos em sistema de plantio direto no sul do Brasil. Para tanto foi desenvolvido um questionário com um roteiro básico englobando as características da propriedade, do sistema de produção e administração, e dos recursos utilizados, mecanização e mão de obra. Realizou-se uma amostragem estratificada por área das unidades para as entrevistas e coleta de dados. Dentre os resultados obtidos destaca-se que as produtividades médias das culturas estiveram acima da média nacional e houve pouca variação nos estratos para a produtividade e principais espécies de culturas utilizadas. A mão de obra nas propriedades é utilizada na operação das máquinas agrícolas...

Estudo de metodo de identificação dos parametros de desbalanceamento e de fundação de maquinas rotativas; Study of identification method for unbalance and foundation parameters of rotation machinery

Jose Alexandre Ubinha
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2005 Português
Relevância na Pesquisa
47.151235%
A identificação de um modelo preciso de fundação flexível e dos parâmetros de desbalanceamento (amplitude e fase) de um sistema girante, através das medições de vibração da máquina, tem sido alvo de constantes pesquisas e desenvolvimento ao longo das últimas décadas. A utilização de programas computacionais, cujos recursos de processamento e visualização de dados são periodicamente atualizados, proporcionou um grande avanço na área de análise de vibrações em máquinas rotativas. Neste contexto, o presente trabalho tem como objetivo a implementação e aplicação de um método híbrido numérico - experimental de determinação dos parâmetros de desbalanceamento e de fundação, que utiliza a resposta ao desbalanço medida durante a partida ou parada da máquina e um modelo numérico preciso do sistema girante. O trabalho apresenta o desenvolvimento teórico da metodologia estudada e discute os aspectos computacionais da implementação numérica do mesmo. O desempenho do procedimento de identificação é verificado numericamente através da simulação de diversos sistemas rotativos e a influência dos diversos fatores que interferem na precisão dos resultados é discutida criteriosamente. Na maioria dos casos...

Identification of alternative splicing and negative splicing activity of a nonsegmented negative-strand RNA virus, Borna disease virus

Tomonaga, Keizo; Kobayashi, Takeshi; Lee, Byeong- Jae; Watanabe, Makiko; Kamitani, Wataru; Ikuta, Kazuyoshi
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 07/11/2000 Português
Relevância na Pesquisa
46.81787%
Borna disease virus (BDV) is a nonsegmented negative-strand RNA virus that belongs to the Mononegavirales. Unlike other animal viruses of this order, BDV replicates and transcribes in the nucleus of infected cells. Previous studies have shown that BDV uses RNA splicing machinery for its mRNA expression. In the present study, we identified spliced RNAs that use an alternative 3′ splice site, SA3, in BDV-infected cell lines as well as infected animal brain cells. Transient transfection analysis of cDNA clones of BDV RNA revealed that although SA3 is a favorable splice site in mammalian cells, utilization of SA3 is negatively regulated in infected cells. This negative splicing activity of the SA3 site is regulated by a putative cis-acting region, the exon splicing suppressor (ESS), within the polymerase exon of BDV. The BDV ESS contains similar motifs to other known ESSs present in viral and cellular genes. Furthermore, our results indicated that a functional polyadenylation signal just upstream of the BDV ESS is also involved in the regulation of alternative splicing of BDV. These observations represent the first documentation of complex RNA splicing in animal RNA viruses and also provide new insight into the mechanism of regulation of alternative splicing in animal viruses.

A Large Population of Small Chloroplasts in Tobacco Leaf Cells Allows More Effective Chloroplast Movement Than a Few Enlarged Chloroplasts1

Jeong, Won Joong; Park, Youn-Il; Suh, KyeHong; Raven, John A.; Yoo, Ook Joon; Liu, Jang Ryol
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /05/2002 Português
Relevância na Pesquisa
47.450513%
We generated transgenic tobacco (Nicotiana tabacum cv Xanthi) plants that contained only one to three enlarged chloroplasts per leaf mesophyll cell by introducing NtFtsZ1-2, a cDNA for plastid division. These plants were used to investigate the advantages of having a large population of small chloroplasts rather than a few enlarged chloroplasts in a leaf mesophyll cell. Despite the similarities in photosynthetic components and ultrastructure of photosynthetic machinery between wild-type and transgenic plants, the overall growth of transgenic plants under low- and high-light conditions was retarded. In wild-type plants, the chloroplasts moved toward the face position under low light and toward the profile position under high-light conditions. However, chloroplast rearrangement in transgenic plants in response to light conditions was not evident. In addition, transgenic plant leaves showed greatly diminished changes in leaf transmittance values under both light conditions, indicating that chloroplast rearrangement was severely retarded. Therefore, under low-light conditions the incomplete face position of the enlarged chloroplasts results in decreased absorbance of light energy. This, in turn, reduces plant growth. Under high-light conditions...

The regulatory utilization of genetic redundancy through responsive backup circuits

Kafri, Ran; Levy, Melissa; Pilpel, Yitzhak
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.81497%
Functional redundancies, generated by gene duplications, are highly widespread throughout all known genomes. One consequence of these redundancies is a tremendous increase to the robustness of organisms to mutations and other stresses. Yet, this very robustness also renders redundancy evolutionarily unstable, and it is, thus, predicted to have only a transient lifetime. In contrast, numerous reports describe instances of functional overlaps that have been conserved throughout extended evolutionary periods. More interestingly, many such backed-up genes were shown to be transcriptionally responsive to the intactness of their redundant partner and are up-regulated if the latter is mutationally inactivated. By manual inspection of the literature, we have compiled a list of such “responsive backup circuits” in a diverse list of species. Reviewing these responsive backup circuits, we extract recurring principles characterizing their regulation. We then apply modeling approaches to explore further their dynamic properties. Our results demonstrate that responsive backup circuits may function as ideal devices for filtering nongenetic noise from transcriptional pathways and obtaining regulatory precision. We thus challenge the view that such redundancies are simply leftovers of ancient duplications and suggest they are an additional component to the sophisticated machinery of cellular regulation. In this respect...

Utilization of host SR protein kinases and RNA-splicing machinery during viral replication

Fukuhara, Takeshi; Hosoya, Takamitsu; Shimizu, Saki; Sumi, Kengo; Oshiro, Takako; Yoshinaka, Yoshiyuki; Suzuki, Masaaki; Yamamoto, Naoki; Herzenberg, Leonore A.; Herzenberg, Leonard A.; Hagiwara, Masatoshi
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.422188%
Although the viral genome is often quite small, it encodes a broad series of proteins. The virus takes advantage of the host-RNA-processing machinery to provide the alternative splicing capability necessary for the expression of this proteomic diversity. Serine–arginine-rich (SR) proteins and the kinases that activate them are central to this alternative splicing machinery. In studies reported here, we use the HIV genome as a model. We show that HIV expression decreases overall SR protein/activity. However, we also show that HIV expression is significantly increased (20-fold) when one of the SR proteins, SRp75 is phosphorylated by SR protein kinase (SRPK)2. Thus, inhibitors of SRPK2 and perhaps of functionally related kinases, such as SRPK1, could be useful antiviral agents. Here, we develop this hypothesis and show that HIV expression down-regulates SR proteins in Flp-In293 cells, resulting in only low-level HIV expression in these cells. However, increasing SRPK2 function up-regulates HIV expression. In addition, we introduce SR protein phosphorylation inhibitor 340 (SRPIN340), which preferentially inhibits SRPK1 and SRPK2 and down-regulates SRp75. Although an isonicotinamide compound, SPRIN340 (or its derivatives) remain to be optimized for better specificity and lower cytotoxicity...

Initiation context modulates autoregulation of eukaryotic translation initiation factor 1 (eIF1)

Ivanov, Ivaylo P.; Loughran, Gary; Sachs, Matthew S.; Atkins, John F.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.81395%
The central feature of standard eukaryotic translation initiation is small ribosome subunit loading at the 5′ cap followed by its 5′ to 3′ scanning for a start codon. The preferred start is an AUG codon in an optimal context. Elaborate cellular machinery exists to ensure the fidelity of start codon selection. Eukaryotic initiation factor 1 (eIF1) plays a central role in this process. Here we show that the translation of eIF1 homologs in eukaryotes from diverse taxa involves initiation from an AUG codon in a poor context. Using human eIF1 as a model, we show that this poor context is necessary for an autoregulatory negative feedback loop in which a high level of eIF1 inhibits its own translation, establishing that variability in the stringency of start codon selection is used for gene regulation in eukaryotes. We show that the stringency of start codon selection (preferential utilization of optimal start sites) is increased to a surprising degree by overexpressing eIF1. The capacity for the cellular level of eIF1 to impact initiation through the variable stringency of initiation codon selection likely has significant consequences for the proteome in eukaryotes.

Outer Membrane Targeting of Pseudomonas aeruginosa Proteins Shows Variable Dependence on the Components of Bam and Lol Machineries

Hoang, Hanh H.; Nickerson, Nicholas N.; Lee, Vincent T.; Kazimirova, Anastasia; Chami, Mohamed; Pugsley, Anthony P.; Lory, Stephen
Fonte: American Society of Microbiology Publicador: American Society of Microbiology
Tipo: Artigo de Revista Científica
Publicado em 06/12/2011 Português
Relevância na Pesquisa
47.626514%
In Gram-negative bacteria, the Lol and Bam machineries direct the targeting of lipidated and nonlipidated proteins, respectively, to the outer membrane (OM). Using Pseudomonas aeruginosa strains with depleted levels of specific Bam and Lol proteins, we demonstrated a variable dependence of different OM proteins on these targeting pathways. Reduction in the level of BamA significantly affected the ability of the β-barrel membrane protein OprF to localize to the OM, while the targeting of three secretins that are functionally related OM proteins was less affected (PilQ and PscC) or not at all affected (XcpQ). Depletion of LolB affected all lipoproteins examined and had a variable effect on the nonlipidated proteins. While the levels of OprF, PilQ, and PscC were significantly reduced by LolB depletion, XcpQ was unaffected and was correctly localized to the OM. These results suggest that certain β-barrel proteins such as OprF primarily utilize the complete Bam machinery. The Lol machinery participates in the OM targeting of secretins to variable degrees, likely through its involvement in the assembly of lipidated Bam components. XcpQ, but not PilQ or PscC, was shown to assemble spontaneously into liposomes as multimers. This work raises the possibility that there is a gradient of utilization of Bam and Lol insertion and targeting machineries. Structural features of individual proteins...

Old and New Stories: Revelations from Functional Analysis of the Bovine Mammary Transcriptome during the Lactation Cycle

Bionaz, Massimo; Periasamy, Kathiravan; Rodriguez-Zas, Sandra L.; Everts, Robin E.; Lewin, Harris A.; Hurley, Walter L.; Loor, Juan J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 12/03/2012 Português
Relevância na Pesquisa
46.818867%
The cow mammary transcriptome was explored at −30, −15, 1, 15, 30, 60, 120, 240, and 300 d relative to parturition. A total of 6,382 differentially expressed genes (DEG) at a false discovery rate ≤0.001 were found throughout lactation. The greatest number of DEG (>3,500 DEG) was observed at 60 and 120 d vs. −30 d with the largest change between consecutive time points observed at −15 vs. 1 d and 120 vs. 240 d. Functional analysis of microarray data was performed using the Dynamic Impact Approach (DIA). The DIA analysis of KEGG pathways uncovered as the most impacted and induced ‘Galactose metabolism’, ‘Glycosylphosphatidylinositol (GPI)-anchor biosynthesis’, and ‘PPAR signaling’; whereas, ‘Antigen processing and presentation’ was among the most inhibited. The integrated interpretation of the results suggested an overall increase in metabolism during lactation, particularly synthesis of carbohydrates and lipid. A marked degree of utilization of amino acids as energy source, an increase of protein export, and a decrease of the protein synthesis machinery as well cell cycle also were suggested by the DIA analysis. The DIA analysis of Gene Ontology and other databases uncovered an induction of Golgi apparatus and angiogenesis...

High-Throughput Screening of Dipeptide Utilization Mediated by the ABC Transporter DppBCDF and Its Substrate-Binding Proteins DppA1-A5 in Pseudomonas aeruginosa

Pletzer, Daniel; Lafon, Corinne; Braun, Yvonne; Köhler, Thilo; Page, Malcolm G. P.; Mourez, Michael; Weingart, Helge
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 22/10/2014 Português
Relevância na Pesquisa
47.609897%
In this study, we show that the dppBCDF operon of Pseudomonas aeruginosa PA14 encodes an ABC transporter responsible for the utilization of di/tripeptides. The substrate specificity of ABC transporters is determined by its associated substrate-binding proteins (SBPs). Whereas in E. coli only one protein, DppA, determines the specificity of the transporter, five orthologous SBPs, DppA1–A5 are present in P. aeruginosa. Multiple SBPs might broaden the substrate specificity by increasing the transporter capacity. We utilized the Biolog phenotype MicroArray technology to investigate utilization of di/tripeptides in mutants lacking either the transport machinery or all of the five SBPs. This high-throughput method enabled us to screen hundreds of dipeptides with various side-chains, and subsequently, to determine the substrate profile of the dipeptide permease. The substrate spectrum of the SBPs was elucidated by complementation of a penta mutant, deficient of all five SBPs, with plasmids carrying individual SBPs. It became apparent that some dipeptides were utilized with different affinity for each SBP. We found that DppA2 shows the highest flexibility on substrate recognition and that DppA2 and DppA4 have a higher tendency to utilize tripeptides. DppA5 was not able to complement the penta mutant under our screening conditions. Phaseolotoxin...

Regulation of mRNA Abundance by Polypyrimidine Tract-Binding Protein-Controlled Alternate 5′ Splice Site Choice

Hamid, Fursham M.; Makeyev, Eugene V.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 06/11/2014 Português
Relevância na Pesquisa
47.115757%
Alternative splicing (AS) provides a potent mechanism for increasing protein diversity and modulating gene expression levels. How alternate splice sites are selected by the splicing machinery and how AS is integrated into gene regulation networks remain important questions of eukaryotic biology. Here we report that polypyrimidine tract-binding protein 1 (Ptbp1/PTB/hnRNP-I) controls alternate 5′ and 3′ splice site (5′ss and 3′ss) usage in a large set of mammalian transcripts. A top scoring event identified by our analysis was the choice between competing upstream and downstream 5′ss (u5′ss and d5′ss) in the exon 18 of the Hps1 gene. Hps1 is essential for proper biogenesis of lysosome-related organelles and loss of its function leads to a disease called type 1 Hermansky-Pudlak Syndrome (HPS). We show that Ptbp1 promotes preferential utilization of the u5′ss giving rise to stable mRNAs encoding a full-length Hps1 protein, whereas bias towards d5′ss triggered by Ptbp1 down-regulation generates transcripts susceptible to nonsense-mediated decay (NMD). We further demonstrate that Ptbp1 binds to pyrimidine-rich sequences between the u5′ss and d5′ss and activates the former site rather than repressing the latter. Consistent with this mechanism...

Description Of Procedures In Automotive Engine Plants

Artzner, Denis; Whitney, Dr. Daniel
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 5723613 bytes; application/pdf
Português
Relevância na Pesquisa
46.824697%
1. Human resources - For automakers, the total cost of paying average workers is around $40000 per year (mean value); the numbers range from $30000 to $60000 (except for a Central European facility where it is much lower). On average, direct pay is three times the amount of benefits. In general, worker qualification does not affect the benefits policy within an automobile engine plant. - Overall, the average age of workers in engine plants is slightly above 40 years old. There is no difference by geographic region. In older engine plants, workers do tend to be older. Annual turnover rates are around 5%. Mean values for unionization levels are 7990 for hourly workers, 45% for salaried workers. It is common for production workers to be assigned different tasks; the engine plants where the union contract restricts the kind of activities are located in North America. - A majority of engine plants surveyed have work teams, and they are deployed in all departments. In most cases, work teams were introduced about five years ago. Sometimes, work team leaders are not elected. The average training received is 41 hours per employee per year. Fluctuations in the values are large. European facilities tend to have more training. Respondents felt that inspecting one?s work...

Supply chain analysis of Gabilan Manufacturing Inc.

Darnell, Andrew; Hodgson, Daniel; Fouts, Miguel; Kachenchai, Daniel; Neuman, James; Darnell, Andrew; Hodgson, Daniel; Fouts, Miguel; Kachenchai, Daniel
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Formato: viii, 123 p. : col. ill.; 28 cm.
Português
Relevância na Pesquisa
67.115757%
Approved for public release; distribution is unlimited.; MBA Professional Report; Approved for public release; distribution is unlimited.; The purpose of this MBA Project was to investigate and provide alternative supply chain management strategies to assist Gabilan Manufacturing Inc. in reducing supply chain costs. This project was conducted with the sponsorship and assistance of Gabilan Manufacturing Inc. There were two primary goals of this project. The first was to identify and document the impact of forecasting errors in an environment where customer forecasts are available to the vendor. The second was to investigate the costs associated with relocating cutting operations as well as the procurement impact of a new cutting machine. Both of these goals relate directly to the overall effort to reduce supply chain costs without a loss of service level to Gabilan's customer.; Lieutenant Commander, United States Navy; Lieutenant Commander, United States Navy; Lieutenant Commander, United States Navy; Lieutenant, United States Navy; Lieutenant Commander, United States Navy; Lieutenant Commander, United States Navy; Lieutenant Commander, United States Navy; Lieutenant Commander, United States Navy; Lieutenant, United States Navy

Study of the effect of the geometrical parameters of the runner and operation conditions on performance and flow characteristics in a cross flow turbine

Pel??ez Restrepo, Juan Diego
Fonte: Universidad EAFIT; Maestr??a en Ingenier??a; Escuela de Ingenier??a Publicador: Universidad EAFIT; Maestr??a en Ingenier??a; Escuela de Ingenier??a
Tipo: masterThesis; Tesis de Maestr??a; acceptedVersion
Português
Relevância na Pesquisa
46.81929%
Due to technological development, massive use of technology, and accelerated population growth in some regions of the planet, the use of renewable energy sources is important to match the increasing electric energy demand -- Hydropower is an important source of renewable energy around the world, due to its simple but efficient way to provide clean electricity generation -- Currently, the cross flow turbine also known as Banki-Turbine has been increasingly used in many places around the world due to its simple structure, modest efficiency and its good performance in small and low head hydroelectric applications -- It is presumed that the massive utilization of this turbines has been limited due to its low efficiency compared to other turbines with efficiencies near to 90% -- Improving this turbine efficiency would make it more attractive and competitive -- This can be achieved by means of studying the turbine operation and determining the most significant parameters in its performance -- Therefore, the interest of this work is to investigate the performance of the cross flow turbine and the flow characteristics through the turbine -- Two kind of analysis are performed in this work -- The objective of the first analysis is to perform experimental tests of some cross flow turbine prototypes under different operating conditions...

Description Of Procedures In Automotive Engine Plants (ABSTRACT)

Artzner, Denis; Whitney, Daniel
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 5723613 bytes; application/pdf
Português
Relevância na Pesquisa
46.824697%
ABSTRACT 1. Human resources - For automakers, the total cost of paying average workers is around $40000 per year (mean value); the numbers range from $30000 to $60000 (except for a Central European facility where it is much lower). On average, direct pay is three times the amount of benefits. In general, worker qualification does not affect the benefits policy within an automobile engine plant. - Overall, the average age of workers in engine plants is slightly above 40 years old. There is no difference by geographic region. In older engine plants, workers do tend to be older. Annual turnover rates are around 5%. Mean values for unionization levels are 7990 for hourly workers, 45% for salaried workers. It is common for production workers to be assigned different tasks; the engine plants where the union contract restricts the kind of activities are located in North America. - A majority of engine plants surveyed have work teams, and they are deployed in all departments. In most cases, work teams were introduced about five years ago. Sometimes, work team leaders are not elected. The average training received is 41 hours per employee per year. Fluctuations in the values are large. European facilities tend to have more training. Respondents felt that inspecting one's work...

Evidence for Metabolic Provisioning by a Common Invertebrate Endosymbiont, Wolbachia pipientis, during Periods of Nutritional Stress

Brownlie, Jeremy C.; Cass, Bodil N.; Riegler, Markus; Witsenburg, Joris J.; Iturbe-Ormaetxe, Iñaki; McGraw, Elizabeth A.; O'Neill, Scott L.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.80738%
Wolbachia are ubiquitous inherited endosymbionts of invertebrates that invade host populations by modifying host reproductive systems. However, some strains lack the ability to impose reproductive modification and yet are still capable of successfully invading host populations. To explain this paradox, theory predicts that such strains should provide a fitness benefit, but to date none has been detected. Recently completed genome sequences of different Wolbachia strains show that these bacteria may have the genetic machinery to influence iron utilization of hosts. Here we show that Wolbachia infection can confer a positive fecundity benefit for Drosophila melanogaster reared on iron-restricted or -overloaded diets. Furthermore, iron levels measured from field-collected flies indicated that nutritional conditions in the field were overall comparable to those of flies reared in the laboratory on restricted diets. These data suggest that Wolbachia may play a previously unrecognized role as nutritional mutualists in insects.

Images, Numerical Analysis of Singularities and Shock Filters

Rudin, Leonid Iakov
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em 01/01/1987 Português
Relevância na Pesquisa
46.820635%
This work is concerned primarily with establishing a natural mathematical framework for the Numerical Analysis of Singularities, a term which we coined for this new evolving branch of numerical analysis. The problem of analyzing singular behavior of nonsmooth functions is implicitly or explicitly ingrained in any successful attempt to extract information from images. The abundance of papers on the so called Edge Detection testifies to this statement. We attempt to make a fresh start by reformulating this old problem in the rigorous context of the Theory of Generalized Functions of several variables with stress put on the computational aspects of essential singularities. We state and prove a variant of the Divergence Theorem for discontinuous functions which we call Fundamental Theorem of Edge Detection, for it is the backbone of the advocated here numerical analysis based on the estimates of contribution5 furnished by the essential singularities of functions. We further extend this analysis to arbitrary order singularities by utilization of the Miranda's calculus of tangential derivatives. With this machinery we are able to explore computationally the internal geometry of singularities including singular, i.e., nonsmooth, singularity boundaries. This theory give5 rise to singularity detection scheme called "rotating thin masks" which is applicable to arbitrary order n-dimensional essential singularities. In the particular implementation we combined first-order detector with derived here various curvature detectors. Preliminary experimental results are presented. We also derive a new class of nonlinear singularity detection schemes based on tensor products of distributions. Finally...

Energy Procurement Strategies in the Presence of Intermittent Sources

Nair, Jayakrishnan; Adlakha, Sachin; Wierman, Adam
Fonte: Association for Computing Machinery (ACM) Publicador: Association for Computing Machinery (ACM)
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /06/2014 Português
Relevância na Pesquisa
46.820024%
The increasing penetration of intermittent, unpredictable renewable energy sources such as wind energy, poses significant challenges for utility companies trying to incorporate renewable energy in their portfolio. In this work, we study the problem of conventional energy procurement in the presence of intermittent renewable resources. We model the problem as a variant of the newsvendor problem, in which the presence of renewable resources induces supply side uncertainty, and in which conventional energy may be procured in three stages to balance supply and demand. We compute closed-form expressions for the optimal energy procurement strategy and study the impact of increasing renewable penetration, and of proposed changes to the structure of electricity markets. We explicitly characterize the impact of a growing renewable penetration on the procurement policy by considering a scaling regime that models the aggregation of unpredictable renewable sources. A key insight from our results is that there is a separation between the impact of the stochastic nature of this aggregation, and the impact of market structure and forecast accuracy. Additionally, we study the impact on procurement of two proposed changes to the market structure: the addition and the placement of an intermediate market. We show that addition of an intermediate market does not necessarily increase the efficiency of utilization of renewable sources. Further...

Optimizing LHD utilization

Mkhwanazi,D.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2011 Português
Relevância na Pesquisa
47.484663%
The purpose of the project was to optimize load haul dump (LHD) machinery use as they were spending too much time doing what they should not be doing. During the investigation, the author found that the machine's actual availability was 86% and the utilization ranged between 30% and 42%.This shows that the availability of the machine has met its target. Therefore the main problem was with the LHD utilization and that is what the project focuses on. To satisfy the objectives, the author firstly studied the existing mining data like the key performance indicators (KPIs) in order to analyse the machine's availability and utilization; this is what gave direction to the problem. Secondly the author did a literature review on mines with similar problems. This gave the author ideas on what to look at in approaching such a situation. Thirdly, the author gathered information on what the LHDs are doing on a daily basis by doing a time study. This gave the author an idea of how long it took the LHDs to complete a specific task. The author also interviewed operators and their supervisors in order to find the best practice work. This helped in identifying the problem areas when comparing the best practice work with what the LHDs are actually doing. According to the project results...