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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Avaliação do impacto da variação da pressão atmosférica sobre o desempenho de frangos de corte / Study of impact of atmospheric pressure variation on the broiler production performance

Silva, Rafael Lima Ferreira 20 August 2018 (has links)
Orientador: Daniella Jorge Moura / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-20T06:25:39Z (GMT). No. of bitstreams: 1 Silva_RafaelLimaFerreira_M.pdf: 3814472 bytes, checksum: 67a0f93c43db3642b1de76eafb757b70 (MD5) Previous issue date: 2012 / Resumo: A carne de frango é a principal fonte de proteína para os brasileiros. Estima-se que o consumo atual seja de 41,5 kg por habitante/ano, sendo sua criação objeto de estudo de grande interesse. A produção de frangos de corte tem seu desempenho relacionado a fatores genéticos, nutricionais, ambientais e sanitários. O estudo de fatores ambientais na avicultura busca entender as condições de conforto nas quais as aves possam expressar seu maior potencial genético e assim gerar produções economicamente mais rentáveis. O microclima de criação das aves é composto por umidade, temperatura, pressão atmosférica, outros gases e partículas em suspensão. A proposta deste estudo foi avaliar o desempenho das aves frente à pressão atmosférica, tendo como referencial a variação da mesma, nos últimos vinte e um, catorze e sete dias que antecedem o abate das aves. Em comparação com a pressão atmosférica, o principal impacto avaliado foi o consumo de alimento das aves. Os dados de desempenho foram provenientes de uma empresa avícola localizada no interior do estado do Paraná. Para os dados de clima foram utilizados as variáveis de temperatura máxima, umidade máxima, e pressão atmosférica mínima, provenientes da base de dados da Embrapa (Empresa Brasileira de Pesquisa Agropecuária), da estação de coleta localizada na cidade de Marechal Cândido Rondon, estado do Paraná. A metodologia utilizada para a análise dos dados foi à análise por regressão múltipla, que confronta uma variável dependente em função de múltiplas independentes, permitindo assim uma comparação de variáveis climáticas com variáveis de desempenho. O resultado para a variável pressão atmosférica mínima média, dos últimos vinte e um dias foi significativo, apresentando um impacto de -13gramas de consumo por hPa de variação de pressão. O resultado aos catorze dias foi de -7 gramas por hPa e o resultado aos sete dias não apresentou significância estatística / Abstract: The chicken meat is the main source of protein for Brazilians. It is estimated that the current consumption is 41.5 kg per capita / year, and its production is object of study of great interest. The production of broiler performance is related to genetic, nutritional, environmental and health factors. The study of environmental factors in the poultry industry seeks to understand the comfort conditions in which the birds can express their genetic potential, to generate more profit. The microclimate of birds is composed by humidity, temperature, atmospheric pressure, other gases and particles in suspension. The purpose of this study was to evaluate the performance of birds against the atmospheric pressure variation for the same altitude, for the last twenty-one, fourteen and seven days before slaughter. The important impact found was feed intake. Performance data were obtained from a poultry company located in the state of Paraná. For the climate data it was used the data of maximum temperature, maximum humidity, and atmospheric pressure minimum, from the database of Embrapa, collected at the station in the Marechal Candido Rondon. The methodology used for the analysis of the data was multiple regression using a dependent variable as a function of multiple independent allowing a comparison of climatic variables with performance variables. The result for minimum atmospheric pressure of the last twenty-one days was presenting a significant impact of consumption by -13 grams per hPa unit pressure variation. The result for the last fourteen days was -7 grams per hPa unit pressure variation. For the last seven days, the result was not statistically significant / Mestrado / Construções Rurais e Ambiencia / Mestre em Engenharia Agrícola
42

High-Performance Simulations for Atmospheric Pressure Plasma Reactor

Chugunov, Svyatoslav January 2012 (has links)
Plasma-assisted processing and deposition of materials is an important component of modern industrial applications, with plasma reactors sharing 30% to 40% of manufacturing steps in microelectronics production [1]. Development of new flexible electronics increases demands for efficient high-throughput deposition methods and roll-to-roll processing of materials. The current work represents an attempt of practical design and numerical modeling of a plasma enhanced chemical vapor deposition system. The system utilizes plasma at standard pressure and temperature to activate a chemical precursor for protective coatings. A specially designed linear plasma head, that consists of two parallel plates with electrodes placed in the parallel arrangement, is used to resolve clogging issues of currently available commercial plasma heads, as well as to increase the flow-rate of the processed chemicals and to enhance the uniformity of the deposition. A test system is build and discussed in this work. In order to improve operating conditions of the setup and quality of the deposited material, we perform numerical modeling of the plasma system. The theoretical and numerical models presented in this work comprehensively describe plasma generation, recombination, and advection in a channel of arbitrary geometry. Number density of plasma species, their energy content, electric field, and rate parameters are accurately calculated and analyzed in this work. Some interesting engineering outcomes are discussed with a connection to the proposed setup. The numerical model is implemented with the help of high-performance parallel technique and evaluated at a cluster for parallel calculations. A typical performance increase, calculation speed-up, parallel fraction of the code and overall efficiency of the parallel implementation are discussed in details.
43

The partitioning of energy between geostrophic and ageostrophic modes in a simple model

Errico, Ronald Mark January 1980 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 156-158. / by Ronald Mark Errico. / Ph.D.
44

Osmophoresis of lipid vesicles in solute gradients

Gu, Yang January 2021 (has links)
Lipid membranes are semipermeable, allowing for water transport across the membrane but rejecting polar solutes and large molecules. Differences in solute concentrations across a lipid membrane lead to differences in the osmotic pressure Δπ causing water to flow towards regions of higher osmotic pressure (higher solute concentration) at speeds of v=-LpΔπ , where Lp is the hydraulic conductivity of the membrane. When a lipid vesicle is placed in a concentration gradient, it is predicted to move to regions of lower concentration due to osmotic flows across the membrane. John Anderson labeled this motion "osmophoresis'' and proposed a theory that predicts the vesicle velocity as U = -½𝛼LpRTG, where 𝛼 is the vesicle radius, RT is the thermal energy, and G=∇C is the imposed concentration gradient. The first experimental demonstration of osmophoresis reported a 1 μm/s migration velocity of DMPC vesicles in a 10 mM/mm sucrose gradient created between two dialysis tubes. However, Anderson's theory predicts that osmophoretic velocity should be four order of magnitude smaller than the observed velocity. A central goal of this Dissertation is to resolve this discrepancy either by validating Anderson's theory or by identifying relevant physics it may lack. Our central conclusion is that Anderson's theory is likely correct and experimental reports of faster osmophoresis can be attributed to convective flows---particularly, density driven flows caused by the solute gradients. To quantify osmophoresis, we need a steady concentration gradient and micron sized lipid vesicles which are predicted to move faster than smaller vesicles and can be observed by optical microscopy. In Chapter 1, I review methods for generating concentration gradients, including glass chambers for chemotaxis assays and microfluidic devices for sustained operation. In Chapter 2, I review the methods used in this Dissertation for producing giant lipid vesicles, which include film rehydration and emulsion templating techinques. Chapter 3 describes a quantitative investigation of the convective flows induced by solute gradients within microfluidic gradient generators. Solute gradients drive fluid motions due to combinations of gravitational body forces and diffusioosmotic surface forces. I quantify and model how these flows depend on solute type, concentration gradient, device height, and solution viscosity. I describe how undesired convective flows can be mitigated by adding thickening agents to increase the solution viscosity or by density matching between high and low concentration solutions. Chapter 4 describes experiments to measure the osmophoresis of lipid vesicles in osmotic gradients while controlling for convective flows. I use density matched sugar solutions to create 315 mM/mm gradients within a commercial gradient generator (Dunn chamber) while limiting convective flows to less than 20 nm/s. I quantify the motions of lipid vesicles and tracer particles by optical microscopy and observe that both move in a common direction at speeds of 0-10 nm/s. According to Anderson's theory, the expected osmophoretic velocity of lipid vesicles in the solute gradient we applied is 4 nm/s assuming a membrane permeability is 100 μm/s. By contrast, the previously reported motion of DMPC vesicles at speeds of 1 um/s in a 10 mM/mm gradient could not be reproduced and was likely caused by inadequate control over gradient-induced convective flows. One strategy to enhance vesicle motion in osmotic gradients is to increase the membrane permeability---for example, by addition of water channel proteins like aquaporins. The pursuit of giant vesicles with high permeability creates a challenge for measuring the membrane permeability owing to rapid vesicle swelling/shrinking in response to osmotic shocks. Chapter 5, I demonstrate how to use photo-initiated polymerization to create a light-induced osmotic shock to vesicles. Vesicle swelling rate in response to this osmotic shock can infer the membrane permeability when the reaction is fast enough. Chapter 6, I conclude how to set up a steady solute gradient with minimal convective flows to study the slow osmophoresis and highlight some specific future directions for osmophoresis, such as enhancing osmophoretic motion by increasing membrane permeability and designing a cell sorting microfluidic device to isolate living cells based on their size and permeability.
45

Characterization of an Atmospheric Pressure Plasma Jet Using Optical Emission and Cavity Ringdown Spectroscopy

Clark, Shane Moore 04 May 2018 (has links)
Cold plasma is useful in numerous medical applications, largely because of the highly-reactive chemical species generated in the discharge. The hydroxyl radical (OH) is of these species and has significant biological importance. An atmospheric pressure plasma jet (APPJ) was constructed in the form of a plasma pencil, and relative and absolute measurements were made of OH in both its first excited ground state—OH(A) and OH(X), respectively—using optical emission spectroscopy and cavity ring-down spectroscopy (CRDS). The total number of OH radicals were found to be constant in the plume and within the range given by relative measurements made on similar devices in the literature.
46

A field investigation of snowpack ventilation /

Granberg, Hardy B. January 1981 (has links)
No description available.
47

The System CaF2-CaMgSi2O6

Lin, Szu-Bin 01 1900 (has links)
<p> The melt equilibria of the system CaF2-CaMgSi2O6 has been studied at atmospheric pressure by using a modified quenching method. This system is characterized by a simple binary eutectic at CaF2 43.4, CaMgSi2O6 56.5 weight percent at 1082t 2°C; neither solid solution nor intermediate compound was found. Some special features have been discussed in detail. The results of the study of the system CaF2-CaMgSi2O6, together with suppositions regarding the system CaF2-CaMgSi2O6-CaCO3, have tentatively been applied to a hypothesis regarding the origin of certain skarns which are considered to be formed by differential melting of impure limestone in regional metamorphic terrains. The applications of this binary system to the theoretical chemistry of Portland cement burning is also incidentally considered. </p> / Thesis / Master of Science (MSc)
48

Développement d’outils chimiométriques pour l’étude des traitements antileishmaniens / Development of chemometric tools for the study of antileishmanial drugs

Imbert, Laurent 30 January 2012 (has links)
Les leishmanioses sont des parasitoses en constante évolution, et l’accroissement d’apparitions de résistances vis-à-vis des traitements disponibles en fait une des préoccupations majeures des organismes de santé publique dans le monde. La miltefosine est actuellement le seul antileishmanien actif par voie orale. Son mécanisme d’action implique les lipides et notamment les phospholipides membranaires du parasite.Afin d’évaluer les effets de la miltefosine sur le parasite ainsi que les mécanismes de résistances, une étude lipidomique d’un clone de Leishmania donovani cultivé sous différentes conditions (traité, résistant, résistant-traité) a été réalisée dans le présent travail. Des analyses couplant une séparation des phospholipides en Chromatographie Liquide Haute-Performance à polarité de Phase Normale (NP-HPLC) avec un Spectromètre de Masse (MS) équippé d’une source d’Ionisation ElectroSpray (ESI) ont été traitées par chimiométrie, à l’aide d’une Correction Orthogonale du Signal suivie d’une Analyse Discriminante par Moindre Carrés Partiels (OSC-PLS-DA). Les principales espèces moléculaires permettant de distinguer les différentes cultures ont ensuite fait l’objet d’une identification structurale par spectrométrie de masse en tandem. Des hypothèses métaboliques ont pu être posées.Puis l’étude a été étendue à une plus grande variété de lipides, séparés par NP-HPLC. Pour cela une comparaison des sources d’ionisation à pression atmosphérique (ESI, Ionisation Chimique à Pression Atmosphérique et PhotoIonisation à Pression Atmosphérique) a été nécessaire afin de sélectionner la mieux adaptée pour un tel couplage. Les mécanismes d’action de la miltefosine et de l’amphotéricine B ont alors fait l’objet d’une étude lipidomique. / Leishmaniasis is a more and more spreading disease, and resistance of parasites toward antileishmanial drugs is a concern for public safety organizations troughout the world. Miltefosine is the only oral drug, and its mechanism of action implies membrane lipids, and phospholipids, of parasite cells.In order to assess this mechanism of action, and resistance mechanisms developed, a lipidomic study of Leishmania donovani strains (treated, resistant, treated-resistant) was performed in the present work. A Normal-Phase High-Performance Liquid Chromatography (NP-HPLC) was coupled to an ElectroSpray Ionisation Mass Spectrometer (ESI-MS) to analyze phospholipids, and data were computed using an Orthogonal Signal Correction-Partial Least Squares-Discriminant Analysis (OSC-PLS-DA). Molecular species responsible for the differenciation of strains were then structuraly identified using tandem mass spectrometry. Hypotheses on metabolic pathways implied were then proposed.The study was then extended to a broader range of lipids, also analyzed through NP-HPLC-MS. A comparison of Atmospheric Pressure Ion sources (ESI, Atmospheric Pressure Chemical Ionization and Atmospheric Pressure PhotoIonization) was thus necessary in order to select the most suitable source. A lipidomic study was then performed to assess mechanisms of action and mechanisms of resistance concerning miltefosine and Amphotericin B.
49

Efeito da pressão barométrica sobre o comportamento de oviposição, parasitismo e alimentação nos insetos / Barometric pressure effect on insect oviposition, parasitism and feeding behavior

Costa, Camila Moreira 29 March 2018 (has links)
Embora a oscilação na pressão barométrica possa afetar o comportamento dos insetos, o seu efeito é ainda pouco explorado para a maioria das espécies. Neste contexto investigou-se em diferentes condições de pressão barométrica os comportamentos de alimentação e oviposição de Diabrotica speciosa (Germ.) (Coleoptera: Chrysomelidae) e Euschistus heros (F.) (Hemiptera: Pentatomidae), oviposição de Spodoptera frugiperda (Walker) (Lepidoptera: Noctuidae) e o parasitismo por Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae), Habrobracon hebetor (Say) (Hymenoptera: Braconidae) e Cotesia flavipes (Cameron) (Hymenoptera: Braconidae). Para isso, foram simuladas as atividades de comportamento mencionadas, dentro de uma câmara barométrica, em condições controladas de pressão baixa, estável e alta, mantendo as demais condições abióticas estáveis. Evidenciou-se que a pressão barométrica pode exercer uma influência em diversas atividades comportamentais nos insetos, mas que não necessariamente possa ser generalizada para todas as espécies e situações. O comportamento de alimentação foi afetado de modo diferenciado para insetos sugadores e mastigadores. Foi observada uma diminuição no número de bainhas alimentares de adultos do percevejo E. heros submetidos a condições de baixa pressão barométrica. Por outro lado, o consumo foliar de adultos de D. speciosa não foi afetado pela pressão. O comportamento de oviposição de E. heros, D. speciosa e S. frugiperda, não foi influenciado significativamente pela pressão barométrica. O parasitismo por T. basalis não foi influenciado pelas condições de pressão barométrica. Entretanto, em condição de baixa pressão barométrica, houve redução no parasitismo por H. hebetor e C. flavipes. / Although barometric pressure oscillation may affect insects\' behavior, that effect is not explored for most species. Weather changes can be associated to patterns of barometric pressure fluctuations. In this sense, we investigated feeding of Diabrotica speciosa (Germ.) (Coleoptera: Chrysomelidae) and Euschistus heros (F.) (Hemiptera: Pentatomidae); oviposition of Spodoptera frugiperda (Walker) (Lepidoptera: Noctuidae), Diabrotica speciosa and Euschistus heros; and parasitism by Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae), Habrobracon hebetor (Say) (Hymenoptera: Braconidae) and Cotesia flavipes (Hymenoptera: Braconidae). Those behaviors were simulated inside a barometric chamber, under controlled conditions of high, stable and low pressure, while other abiotic factor was stable. Barometric pressure clearly influences several insect behavioral activities, but it cannot be generalized to all species. Feeding behavior was distinctively affected for chewing and sucking insects. We observed a decrease in the number of adult salivary sheaths of E. heros submitted to conditions of low barometric pressure. Leaf consumption by Diabrotica speciosa was not affected by barometric pressure. Oviposition behavior was not affected by barometric pressure in any of the species evaluated. The parasitism by Trissolcus basalis did not show influence due to barometric pressure conditions. However, less parasitism of Habrobracon hebetor and Cotesia flavipes was observed under low pressure.
50

Liquid Nitrate Fertilizer Production with Various Atmospheric Pressure Discharges

Zhenyu Shen (6630833) 11 June 2019 (has links)
<div>Plasmas can be used to increase the probability of maturity of seeds and disinfect them. The water applied on plants can also be treated with plasma to reduce bacteria. Discharges normally used to treat water including dielectric barrier discharges, gliding arcs, DC, AC, or pulsed coronas, and various direct discharges in liquid. After treatments, reactive oxygen (ozone) and nitrogen species (nitrite and nitrate) will appear in the water solution. Then, by applied this water, the lifecycle of plant could be significantly influenced. Plasma has a great potential to play an important role in the agriculture discipline. The process of synthesizing nitrate fertilizer with water, air, and electric spark has been known for a long time. But due to low nitrate yield and high energy consumption, it was replaced by the Haber-Bosch process in the first half of the 20th century. The Haber-Bosch process, however, has several disadvantages: it requires natural gas as a raw material, fixes nitrogen in the form of ammonia, and generates oxycarbides as byproducts. Thus, the concept of manufacturing nitrogen fertilizer with only water, air and electricity is still appealing.</div><div><br></div><div>In this project, we want to measure the pH value and conductivity of the water treated by various atmospheric pressure discharges including the arc discharge, DC positive corona discharge, DC voltage driven cold plasma torch operating with helium, dielectric barrier discharge (DBD), and radio-frequency (RF) plasma. Also, it is necessary to verify the existence of different important species in the treated water such as peroxide, nitrite, and nitrate ions by measuring their concentrations. Based on current and voltage measurements and wall-plug electrical energy consumption, energy efficiency of nitrate synthesis was determined in these five plasma systems. Optical emission spectroscopy was employed to study the reaction kinetics of both DBD and RF discharge. Our goal is to produce enough nitrate ions, by plasma treatment with minimal energy input (the value should be at least close to the Haber-Bosch process), in water which could be further used as fertilizers.</div><div><br></div>

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