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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.
11

Ram Pressure Stripping of Molecular Gas / MODELING MOLECULAR GAS SUSCEPTIBILITY TO RAM PRESSURE STRIPPING IN THE VIRGO CLUSTER

Greis, Celine January 2024 (has links)
Ram pressure stripping (RPS) can be described as the constant wind a galaxy experiences when moving through a galaxy cluster. It is well-established that galaxies undergoing this process lose substantial amounts of their atomic gas, but its effect on the cold molecular gas component is still not fully understood. Using high-resolution ALMA CO 2-1 data collected by the PHANGS and VERTICO surveys, I model the detailed effect of RPS in 36 Virgo galaxies on a 150 pc and 720 pc scale by calculating the ratio of ram pressure to the galaxy gravitational restoring force per unit area. If the ram pressure exceeds the restoring pressure, we assume the molecular gas parcel is susceptible to stripping. I reveal that roughly a quarter of our 36 galaxies are susceptible to molecular gas RPS, with up to 70% of their molecular gas in the outer disk (r > R50) being susceptible. As expected, low mass galaxies (log(M∗/M ) = 9.5) seem to be most affected. VERTICO galaxies show molecular gas susceptible to stripping at the outskirts and between their spiral arms. I also find higher fractions of RPS susceptible molecular gas in galaxies exhibiting clear atomic gas tails, suggesting that RPS impacts multiple gas phases at once. Finally, a phase space analysis suggests molecular gas RPS occurs primarily, potentially exclusively, at the first pericentric passage when ram pressure is maximal. / Thesis / Master of Science (MSc)
12

Determinação de íons cádmio e zinco no sistema estuarino - lagunar de Cananéia - Iguape por voltametria de redissolução anódica / Determination of cadmium and zinc ions in the Lagoon - Estuarine System Cananéia - Iguape by anodic stripping voltammetry

Souza, Ana Paula Ruas de 15 September 2010 (has links)
A determinação dos íons Cd(II) e Zn(II) foi realizada em amostras de águas estuarinas por voltametria de redissolução anódica utilizando microeletrodo de fibra de carbono (raio =3 µm). O filme de bismuto foi depositado in situ, simultaneamente com os analitos em microeletrodo sob as condições otimizadas. O intervalo linear da curva de calibração para ambos os íons metálicos foi 0,5 -10,0 nmol L-1 e os limites de detecção de Cd(II) e Zn(II) foram estimados em 17 e 52 pmol L-1, respectivamente. A precisão dos resultados fornecidos empregando-se o microeletrodo de filme de bismuto (BiFME) foi avaliada pela realização de experimento com uma amostra certificada e teste de recuperação. A utilidade da metodologia foi demonstrada aplicando o BiFME para determinar baixas concentrações de Cd(II) e de Zn(II) em água do estuário. / A bismuth-film electrode for use in anodic stripping voltammetry was employed in order to quantify Cd(II) and Zn(II) in estuarine water samples. The bismuth film was deposited in situ simultaneously with the analytes onto a carbon fiber disc microelectrode (radius = 3 µm). Under the optimised conditions, calibration plots for both metallic ions were obtained in the range 0.5 to 10.0 nmol L-1 and the limits of detection for Cd(II) and Zn(II) were estimated as 17 and 52 pmol L-1, respectively. The accuracy of the results supplied by the bismuth film microelectrode (BiFME) was assessed by performing experiment with a certified sample and addition-recovery experiments. The usefulness of the methodology was demonstrated by applying the BiFME to measuring the Cd(II) and Zn(II) content in estuarine water.
13

Avaliação biofarmacotécnica de formulações dermatológicas semi-sólidas de cetoconazol / Dermatological biopharmaceutical evaluation of semi-solid formulations of ketoconazole

Freitas, Zaida Maria Faria de 01 September 2005 (has links)
O cetoconazol (CTZ) é um antifúngico imidazólico de amplo espectro, administrado tipicamente pela via oral (200 ou 400 mg por dia) ou topicamente (creme 2% aplicado duas vezes ao dia). A efícácia da terapia tópica depende das características de liberação do fármaco, do veículo e da farmacocinética da substância ativa no tecido cutâneo, ou seja, de como ela se difunde através da pele. No presente trabalho, duas formulações comerciais (A e B), uma manipulada (C) e três desenvolvidas (D2:0; El: 1 e FO:2) contendo CTZ na concentração de 20 mg/g, foram estudadas quanto às características físico-químicas e quanto ao comportamento biofarmacêutico/bioequivalente tópico, através de medidas adequadas do ativo na camada do estrato córneo (EC). Uma metodologia in vivo denominada tape-stripping ou \'remoção do estrato córneo\' por fitas adesivas foi utilizada para medir a velocidade e extensão da penetração do CTZ no EC do antebraço de voluntários sadios. Um sistema bicompartimental de difusão vertical com membrana sintética (acetato de celulose) e membrana natural (pele suína) foi empregado para avaliar in vitro a taxa de liberação e a avaliação da penetração e eventual permeação do fármaco, respectivamente. Todas as amostras foram analisadas por Cromatografia Líquida de Alta Eficiência (CLAE), com método previamente validado. Nos estudos in vivo, as quantidades de fármaco determinadas no EC (µg/mg) para cada tempo da aplicação foram analisadas estatisticamente empregando-se análise da variância (ANOVA) considerando dois fatores: Fator 1 = tratamento com dois níveis e Fator 2 = antebraços (esquerdo e direito). Dentre os produtos avaliados somente entre A e C houve diferença estatisticamente significativa (p < 0,05). Os ensaios de liberação, através da avaliação do fluxo de fármaco para o meio aceptor, evidenciaram agrupamento das formulações em duas categorias distintas entre si com fluxo entre 2,41, 2,16 e 2,49 µg/cm2/h compreendendo A, B e F0:2 (p = 0,171) e outra com fluxo entre 5,85, 6,28 e 7,21µg/cm2/h para C, D2:0 e E1:1 (p = 0,478) pela ANOVA com α = 0,05. A quantidade de CTZ nos estratos cutâneos da pele suína diminuiu com a profundidade, ou seja, na derme foi detectado menor quantidade de fármaco após aplicação das formulações A, B e F0:2 e não foi detectado sua presença na solução receptora. As formulações A, B e F0:2 não apresentaram um perfil de penetração cutânea na epiderme e na estatisticamente diferente ao nível de 5% (p =0,609 e p = 0,269, respectivamente). A bioequivalência foi avaliada empregando os dados obtidos nos estudos in vivo, de acordo com os critérios das razões (ASC0-240min) entre os produtos B, C e F0:2 em relação a A (considerado referência) com intervalo de confiança de 90% (IC 90%). Considerat1do o limite de 80-125%, as formulações não seriam bioequivalentes, pois existe uma grande diferença entre os produtos A e B, entre A e C, já A e F apresentam intervalo mais próximo do limite citado. Com base nesses resultados, a formulação do produto F poderia ser indicada a um possível desenvolvimento de genérico do produto A. / Ketoconazole (KTZ) is an imidazolic antifungal, of broad-spectrum, typically administered orally (200 or 400 mg per day) or topical1y (2% cream, applied twice daily). The efficacy of the topical therapy depend on the characteristics of the drug\'s release, of the vehicle and of the active substance\'s pharmacokinetic in the cutaneous tissue, in other words, on how this substance diffuses through the skin. On this paper, two commercial formulations (A and B), one manipulated (C) and three developed (D2:0; E1: 1 and F0:2) containing KTZ on the concentration of 20 mg/g, were studied in relation to the physical-chemical characteristics and to the bioavailability/bioequivalence topic behave by an adequate active layer\'s measurement of the stratum corneum (SC). The methodology in vivo called as tape stripping or \'stratum corneum remotion\' by adhesive tapes was proposed to measure the rate and KTZ penetration\'s extension in the SC of healthy volunteers\' forearm. A bicompartmental system of vertical diffusion with sintetic membrane (celullose acetate) and natural membrane (porcine skin) was used to evaluate in vitro the rate of release and the penetration evaluation and eventual drug permeation, respectively. All samples were then submitted to HPLC analysis by previously validated method. In the studies in vivo the amount of drug determined in the SC (µ/mg) for each application time was analyzed using variance\'s analysis (ANOVA) considering two factors: Factor 1 = treatment with two leveis and Factor 2 =forearm (left and right). Among the products evaluated there was only between A and C a statistical1y significant difference (p < 0,05). The assays of release, through the evaluation of the drug flow to the receptor chamber, evidenced the grouping of formulations in two categories, different among themselves, with flow among 2,41; 2,16 and 2,49 µg/cm2/h comprehending A, B and F(0:2) (p = 1,171) and other with flow among 5,85; 6,28 and 7,21µg/cm2/h and to C, D2:0 and E1:1 (p = 0,478) by ANOVA with a = 0,05. The amount of KTZ in the cutaneous stratum of porcine skin decreased with the depth, in other words, a lower value for drug was detected in the dermis after formulations\' application A, B and F0:2 and its presence was not detected in the receptor solution. Formulations A, B and F0:2 did not present a cutaneous penetration\'s profile, in the epidermis and dermis, statisticalIy different by level of 5% (p = 0,6097 e p = 0,269, respectively). Bioequivalence was evaluated using datas obtained from studies in vivo, according to criterias of reason_(ASC0-240min>) among the products B, C and F in relation to A (considered as reference) with interval of confidence of 90% (IC 90%). Considering the 80-125% limit, the formulations would not be bioequivalents, because there is a big difference among products A and B, A and C; now A and F present the nearest interval to thc quoted limito Basing on these results, the formulation of the product F could be indicated a possible generic development of product A.
14

Avaliação biofarmacotécnica de formulações dermatológicas semi-sólidas de cetoconazol / Dermatological biopharmaceutical evaluation of semi-solid formulations of ketoconazole

Zaida Maria Faria de Freitas 01 September 2005 (has links)
O cetoconazol (CTZ) é um antifúngico imidazólico de amplo espectro, administrado tipicamente pela via oral (200 ou 400 mg por dia) ou topicamente (creme 2% aplicado duas vezes ao dia). A efícácia da terapia tópica depende das características de liberação do fármaco, do veículo e da farmacocinética da substância ativa no tecido cutâneo, ou seja, de como ela se difunde através da pele. No presente trabalho, duas formulações comerciais (A e B), uma manipulada (C) e três desenvolvidas (D2:0; El: 1 e FO:2) contendo CTZ na concentração de 20 mg/g, foram estudadas quanto às características físico-químicas e quanto ao comportamento biofarmacêutico/bioequivalente tópico, através de medidas adequadas do ativo na camada do estrato córneo (EC). Uma metodologia in vivo denominada tape-stripping ou \'remoção do estrato córneo\' por fitas adesivas foi utilizada para medir a velocidade e extensão da penetração do CTZ no EC do antebraço de voluntários sadios. Um sistema bicompartimental de difusão vertical com membrana sintética (acetato de celulose) e membrana natural (pele suína) foi empregado para avaliar in vitro a taxa de liberação e a avaliação da penetração e eventual permeação do fármaco, respectivamente. Todas as amostras foram analisadas por Cromatografia Líquida de Alta Eficiência (CLAE), com método previamente validado. Nos estudos in vivo, as quantidades de fármaco determinadas no EC (µg/mg) para cada tempo da aplicação foram analisadas estatisticamente empregando-se análise da variância (ANOVA) considerando dois fatores: Fator 1 = tratamento com dois níveis e Fator 2 = antebraços (esquerdo e direito). Dentre os produtos avaliados somente entre A e C houve diferença estatisticamente significativa (p < 0,05). Os ensaios de liberação, através da avaliação do fluxo de fármaco para o meio aceptor, evidenciaram agrupamento das formulações em duas categorias distintas entre si com fluxo entre 2,41, 2,16 e 2,49 µg/cm2/h compreendendo A, B e F0:2 (p = 0,171) e outra com fluxo entre 5,85, 6,28 e 7,21µg/cm2/h para C, D2:0 e E1:1 (p = 0,478) pela ANOVA com α = 0,05. A quantidade de CTZ nos estratos cutâneos da pele suína diminuiu com a profundidade, ou seja, na derme foi detectado menor quantidade de fármaco após aplicação das formulações A, B e F0:2 e não foi detectado sua presença na solução receptora. As formulações A, B e F0:2 não apresentaram um perfil de penetração cutânea na epiderme e na estatisticamente diferente ao nível de 5% (p =0,609 e p = 0,269, respectivamente). A bioequivalência foi avaliada empregando os dados obtidos nos estudos in vivo, de acordo com os critérios das razões (ASC0-240min) entre os produtos B, C e F0:2 em relação a A (considerado referência) com intervalo de confiança de 90% (IC 90%). Considerat1do o limite de 80-125%, as formulações não seriam bioequivalentes, pois existe uma grande diferença entre os produtos A e B, entre A e C, já A e F apresentam intervalo mais próximo do limite citado. Com base nesses resultados, a formulação do produto F poderia ser indicada a um possível desenvolvimento de genérico do produto A. / Ketoconazole (KTZ) is an imidazolic antifungal, of broad-spectrum, typically administered orally (200 or 400 mg per day) or topical1y (2% cream, applied twice daily). The efficacy of the topical therapy depend on the characteristics of the drug\'s release, of the vehicle and of the active substance\'s pharmacokinetic in the cutaneous tissue, in other words, on how this substance diffuses through the skin. On this paper, two commercial formulations (A and B), one manipulated (C) and three developed (D2:0; E1: 1 and F0:2) containing KTZ on the concentration of 20 mg/g, were studied in relation to the physical-chemical characteristics and to the bioavailability/bioequivalence topic behave by an adequate active layer\'s measurement of the stratum corneum (SC). The methodology in vivo called as tape stripping or \'stratum corneum remotion\' by adhesive tapes was proposed to measure the rate and KTZ penetration\'s extension in the SC of healthy volunteers\' forearm. A bicompartmental system of vertical diffusion with sintetic membrane (celullose acetate) and natural membrane (porcine skin) was used to evaluate in vitro the rate of release and the penetration evaluation and eventual drug permeation, respectively. All samples were then submitted to HPLC analysis by previously validated method. In the studies in vivo the amount of drug determined in the SC (µ/mg) for each application time was analyzed using variance\'s analysis (ANOVA) considering two factors: Factor 1 = treatment with two leveis and Factor 2 =forearm (left and right). Among the products evaluated there was only between A and C a statistical1y significant difference (p < 0,05). The assays of release, through the evaluation of the drug flow to the receptor chamber, evidenced the grouping of formulations in two categories, different among themselves, with flow among 2,41; 2,16 and 2,49 µg/cm2/h comprehending A, B and F(0:2) (p = 1,171) and other with flow among 5,85; 6,28 and 7,21µg/cm2/h and to C, D2:0 and E1:1 (p = 0,478) by ANOVA with a = 0,05. The amount of KTZ in the cutaneous stratum of porcine skin decreased with the depth, in other words, a lower value for drug was detected in the dermis after formulations\' application A, B and F0:2 and its presence was not detected in the receptor solution. Formulations A, B and F0:2 did not present a cutaneous penetration\'s profile, in the epidermis and dermis, statisticalIy different by level of 5% (p = 0,6097 e p = 0,269, respectively). Bioequivalence was evaluated using datas obtained from studies in vivo, according to criterias of reason_(ASC0-240min>) among the products B, C and F in relation to A (considered as reference) with interval of confidence of 90% (IC 90%). Considering the 80-125% limit, the formulations would not be bioequivalents, because there is a big difference among products A and B, A and C; now A and F present the nearest interval to thc quoted limito Basing on these results, the formulation of the product F could be indicated a possible generic development of product A.
15

Novel Electrochemical Detections of Biologically and Environmentally Relevant Substances

Tatum, Clarissa E. 01 December 2010 (has links)
Development and studies of new electrochemical methods for the detection of various biologically and environmentally relevant substances are the focus of this dissertation. A dual amperometric sensor, capable of the simultaneous, real-time determination of NO and O,2, has been developed and optimized. Many tests were performed in order to reduce cross-talking between the two sensors, and an electro-deposited polymer, poly-5-amino-1-naphthol, was shown to reduce the cross-talking to insignificant levels. The use of bismuth-based electrodes in the detection of various metals has been explored. A bismuth bulk electrode has been developed, optimized, and used for the individual and simultaneous determination of Pb(II), Cd(II), and Zn(II). The fundamental electrochemistry of several bismuth-based electrodes in the system used for Cr(VI) analysis has also been explored, and many interactions among the electrode material, ligand, and analyte were observed, particularly the formation of a soluble bismuth-ligand complex. Electrochemical analysis of Cr(VI) was attempted at all of the bismuth-based electrodes, with success at the thin bismuth film electrode. A series of surface modifications were made to the glassy carbon substrate, in an attempt to remove any co-adsorbed contaminants and to understand the sensitivity of the chromium detection process. Inevitably, it was found that the contaminating source was contaminants in the nitrogen gas used for solution deaeration. Upon switching to argon, detection became highly reproducible and showed strong linearity with the Cr(VI) concentration.
16

Determinação de íons cádmio e zinco no sistema estuarino - lagunar de Cananéia - Iguape por voltametria de redissolução anódica / Determination of cadmium and zinc ions in the Lagoon - Estuarine System Cananéia - Iguape by anodic stripping voltammetry

Ana Paula Ruas de Souza 15 September 2010 (has links)
A determinação dos íons Cd(II) e Zn(II) foi realizada em amostras de águas estuarinas por voltametria de redissolução anódica utilizando microeletrodo de fibra de carbono (raio =3 µm). O filme de bismuto foi depositado in situ, simultaneamente com os analitos em microeletrodo sob as condições otimizadas. O intervalo linear da curva de calibração para ambos os íons metálicos foi 0,5 -10,0 nmol L-1 e os limites de detecção de Cd(II) e Zn(II) foram estimados em 17 e 52 pmol L-1, respectivamente. A precisão dos resultados fornecidos empregando-se o microeletrodo de filme de bismuto (BiFME) foi avaliada pela realização de experimento com uma amostra certificada e teste de recuperação. A utilidade da metodologia foi demonstrada aplicando o BiFME para determinar baixas concentrações de Cd(II) e de Zn(II) em água do estuário. / A bismuth-film electrode for use in anodic stripping voltammetry was employed in order to quantify Cd(II) and Zn(II) in estuarine water samples. The bismuth film was deposited in situ simultaneously with the analytes onto a carbon fiber disc microelectrode (radius = 3 µm). Under the optimised conditions, calibration plots for both metallic ions were obtained in the range 0.5 to 10.0 nmol L-1 and the limits of detection for Cd(II) and Zn(II) were estimated as 17 and 52 pmol L-1, respectively. The accuracy of the results supplied by the bismuth film microelectrode (BiFME) was assessed by performing experiment with a certified sample and addition-recovery experiments. The usefulness of the methodology was demonstrated by applying the BiFME to measuring the Cd(II) and Zn(II) content in estuarine water.
17

Dispositivos hifenados para microextração em fase solida / Hyphenated devices for solid phase microextraction

Silva, Rogerio Cesar da 18 March 2005 (has links)
Orientador: Fabio Augusto / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T15:09:26Z (GMT). No. of bitstreams: 1 Silva_RogerioCesarda_D.pdf: 4524361 bytes, checksum: 24333539b89a414df416bbcf9e0ee5bd (MD5) Previous issue date: 2005 / Doutorado / Quimica Analitica / Doutor em Quimica
18

The effect of timing of stripping on hop production under South African conditions

Joseph, Beverley-Anne 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Hops is a small, but important agricultural commodity in South Africa. The hop cones contain secondary metabolites responsible for the flavour, aroma and bitterness in beer. The George and Waboomskraal area are the best suited for growing hops due to climate and geographical location. The optimum latitude for hops growing is 45° - 54° north and south of the equator, while these areas are at 34° S. International hop varieties are not adapted to the South African climate. Winters are too warm and summer days too short, thus all the varieties grown in South Africa have been bred for these specific conditions. The Hop breeding and research program strives to develop internationally competitive varieties with higher yields, desirable brewing characteristics, reducing input costs and increased productivity. To evaluate the current agricultural practices and to determine whether some of these practices negatively affect the plant health and yield, a study was conducted to investigate the effect of the time of stripping. Stripping refers to the practice of removing basal growth of the lower laterals and untrained bines. The study was done in two different microclimates, namely George and Waboomskraal. The aim was to determine the effect of the time of stripping on the vegetative growth, light interception, biomass, soft resins (alpha and beta acids), yield, rootstock weights and carbohydrate concentrations. The effect of stripping was also evaluated on different planting systems and plant maturity, namely Tram lines and conventional planting and 3 years old versus 5 year old plants. The effect of early stripping in terms of dry weight on mature plants is considerably less than the effect on younger plants. Young plants delivered lower dry weights, but accumulated higher carbohydrate reserves in the early stripping treatment. On young plants early stripping showed a significant difference favouring yield on tramlines. There is a general trend across all sites of higher crop efficiencies in the early stripped treatments. Growers could significantly increase yields without negatively affecting the quality (alpha and beta acids) by applying early stripping, especially in the George area. The effect of early stripping becomes more apparent in consecutive years as the time of defoliation affects foliage, carbohydrate concentration, canopy microclimate and light interception resulting in increased yields, especially on tramlines. From this study it can be concluded that early stripping appeared to have an influence on the dry root weight, carbohydrate concentration, light interception, crop efficiencies, yield and biomass. This practice is not only environmentally friendly by using less herbicide, it also delivers an economic gain. The effect of the time of stripping in consecutive years and different varieties deserves further study. / AFRIKAANSE OPSOMMING: Hops is 'n klein, maar belangrike landbou kommoditeit in Suid-Afrika. Die hopkeëls bevat sekondêre metaboliete wat verantwoordelik is vir die smaak, aroma en bitterheid van bier. Die George en Waboomskraal gebied is die beste geskik vir die kweek van hops, a.g.v. die klimaat en geografiese ligging. Die optimum breedtegraad vir hops verbouing is tussen 45° - 54° noord en suid van die ewenaar, waar hierdie gebiede by 34° S lê. Internasionale hops varieteite is nie aangepas by die Suid-Afrikaanse klimaat nie, want die winters is te warm en die daglengte in die somer is te kort. Al die variëteite in Suid Afrika is geteel vir dié spesifieke klimaatstoestande. Die Hopsteling en -navorsingprogram streef daarna om internasionaal mededingende varieteite met hoër opbrengste, verminderde insetkoste, verhoogde produktiwiteit en wenslike broueienskappe te ontwikkel. 'n Studie is gedoen om die effek van stropingstyd te evalueer en te identifiseer of hierdie praktyk negatiewe invloede op die gesondheid van plante en opbrengste het. Stroping verwys na die praktyk van die verwydering van basale groei van die laer laterale en onopgeleide ranke. Die studie is gedoen in twee verskillende mikroklimate, naamlik George en Waboomskraal. Die doel was om te bepaal wat die effek van stropingstyd op die vegetatiewe groei, lig onderskepping, biomassa, alfasure en betasure, opbrengs, wortelmassa en koolhidrate konsentrasies is. Die effek van stropingstyd was ook geëvalueer op verskillende plantsisteme en plant volwassenheid, naamlik Tramlyne en Konvensionele -plantsisteem, en 3 jaar oue teenoor 5 jaar oue plante. Die effek van vroeë stroping in terme van droë gewig op volwasse plante is aansienlik minder as die effek op jonger plante. Jong plante het laer droë gewig, maar hoër koolhidraat reserwes in die vroeë stroping behandeling gelewer. Vroë stroping van jong plante het ’n beduidende verskil getoon ten opsigte van opbrengste op die Tramlyn-plantsisteem. Daar is 'n algemene tendens op alle lokaliteite van hoër opbrengs doeltreffendheid in die vroeë stropings behandelings. Produsente, veral in die George area, kan opbrengste aansienlik verhoog sonder om die kwaliteit (alfa en beta sure) negatief te beïnvloed, deur die toepassing van vroeë stroping. Die effek van vroeë stroping word meer duidelik in agtereenvolgende jare, omdat die stropingstyd die koolhidrate konsentrasie, mikroklimaat binne in die hopranke en lig onderskepping wat lei tot verhoogde opbrengste, veral op die Tramlyn- plantsisteem, beïnvloed. Uit hierdie studie kan afgelei word dat vroeë stroping 'n invloed op die ligonderskepping, plantgewas doeltreffendheid, biomassa, opbrengs, droë wortelgewig en koolhidraatkonsentrasie het. Hierdie praktyk is nie net omgewingsvriendelik nie, maar gebruik minder onkruiddoder en lewer ekononomiese voordele vir die produsent. Die effek van stropingstyd op agtereenvolgende jare en verskillende varieteite verdien verdere studie.
19

A Mathematical Model for the Devolatilization of EPDM Rubber in a Series of Steam Stripping Vessels

Francoeur, Angelica 24 October 2012 (has links)
A steady-state mathematical model for the stripping section of an industrial EPDM rubber production process was developed for a three-tank process, and two four-tank processes. The experiments that were conducted to determine model parameters such as equivalent radius for EPDM particles, as well as solubility and diffusivity parameters for hexane and ENB in EPDM polymer are described. A single-particle multiple-tank model was developed first, and a process model that accounts for the residence-time distribution of crumb particles was developed second. Plant data as well as input data from an existing steady-state model was used to determine estimates for the tuning parameters used in the multiple-particle, multiple-tank model. Using plant data to assess the model’s predictive accuracy, the resulting three-tank and four-tank process B models provide accurate model predictions with a typical error of 0.35 parts per hundred resin (phr) and 0.12 phr. The four-tank process A model provides less-accurate model predictions for residual crumb concentrations in the second tank and has an overall typical error of 1.05 phr. Additional plant data from the three- and four-tank processes would increase the estimability of the parameter values for parameter ranking and estimations steps and thus, yield increased model predictive accuracy. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-10-23 21:06:05.509
20

WING-TIP VORTEX EVOLUTION IN TURBULENCE

Ghimire, Hari Charan 01 January 2018 (has links)
Planar and stereo particle image velocimetry measurements were conducted of a wing-tip vortex decaying in free-stream turbulence in order to understand the evolution of a vortex and its decay mechanism. The vortex decayed faster in the presence of turbulence. The decay of the circulation was found to be almost entirely due to a decrease in circulation of the vortex core, caused by the relative decrease in peak tangential velocity without a corresponding increase in core radius. These events were found to be connected with the stripping of core fluid from the vortex core. The increased rate of decay of the vortex in turbulence coincided with the formation of secondary vortical structures which wrapped azimuthally around the primary vortex. It was also found that regardless of the free-stream condition, the core scaled by peak tangential velocity and core radius.

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