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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.
381

Separation of antimicrobial protein fractions from animal resources for potential use in infant feeding

Al-Mashikhi, Shalan Alwan Edan January 1987 (has links)
In the first part of this study, a non-ferric method for selective elimination of β-lactoglobulin from cheese whey was investigated. A new method was developed based on hexametaphosphate treatment of cheese whey. When Cheddar cheese whey was treated under the optimized conditions, i.e., 1.33 mg/mL sodium hexametaphosphate at 22°C and pH 4.07 for 1 hr, more than 80% of β-lactoglobulin was removed by precipitation. Almost all of the immunoglobulins and the major portion of α-lactalbumin were retained in the supernatant as indicated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunochemical assays. By dialysis against distilled water 72.2% of the phosphorus was removed from the supernatant. In the second and the third part of the thesis, chromatographic methods were used for isolation of immunoglobulins and lactoferrin from whey proteins. By using gel filtration on Sephacryl S-300, 99, 83.3 and 92.1% biologically active immunoglobulin G were obtained for colostral whey, acid and Cheddar cheese whey, respectively. Lactoferrin, selectively adsorbed to the heparin-attached Sepharose, was eluted with 5 mM Veronal-HC1 containing 0.5M NaC1, at pH 7.2. 1,4-Butanediol diglycidyl ether-iminodiacetic acid on Sepharose 6B, or so-called metal chelate-interaction chromatography (MCIC), was loaded with copper ion and used for the same purpose. Of the two peaks obtained, the first yellowish peak was rich in lactoferrin, while the second peak was rich in immunoglobulins. Some of the physical and chemical properties of the proteins in these peaks, including immunochemical properties, isoelectric points, binding to bacterial lipopolysaccharides, and the mechanism of protein-metal interaction via histidine modification, and the capacity of the method were studied. The possibility of isolating immunoglobulins and lactoferrin from electrodialyzed whey was also investigated. In the fourth, fifth and sixth parts of the thesis, the method developed for isolation of immunoglobulins and lactoferrin from whey protein was applied to isolate these biologically important proteins directly from skimmilk, blood and egg white. The casein in skimmilk was found to compete with immunoglobulins for binding to copper ion in MCIC column when skimmilk was loaded in presence of 0.05 M Tris-acetate buffer containing 0.5 M NaC1, pH 8.2; however, this problem was solved by changing the equilibrating buffer to 0.02 M phosphate buffer containing 0.5 M NaC1, pH 7.0. When blood was directly applied to MCIC column, the yield of biologically active IgG was more than 95%. Ovotransferrin, strongly adsorbed to the MCIC column, was eluted with two-step elution protocols which suggests it exists in two forms. The histidine residues in immunoglobulins, caseins, transferrin and ovotransferrin were found to be involved in the mechanism of the interaction with the MCIC column. / Land and Food Systems, Faculty of / Graduate
382

Purification and properties of choline acetyltransferase from chicken brain

Ma, Kelvin January 1978 (has links)
Choline acetyltransferase (ChAc), the enzyme responsible for the synthesis of acetylcholine (ACh), has been extensively purified from chicken brains. Purification procedures included ammonium sulfate fractionation, DEAE-Sephadex (A-25), hydroxyapatite, Sephadex G-150 column chromatography, and affinity chromatography on agarose-hexane-Coenzyme A column. ChAc activity was measured radiochemically. Due to the instability of the enzyme in the course of purification, the most active fraction obtained after agarose-hexane-Coenzyme A chromatography showed a specific activity of only 0.34 μmoles ACh formed/ min./mg protein which corresponded to a 773 fold purification from homogenate. However, on non-denaturing polyacrylamide gel electrophoresis at pH 8.8, the highly purified ChAc preparation showed two distinct bands, and ChAc activity was recovered by slicing and assaying the gel. ChAc activity corresponded to the position of the faster moving band. The same preparation showed one major band and two minor bands on SDS gel electrophoresis. The estimated MW of chicken brain ChAc by gel filtration and SDS gel electrophoresis was 42,500 daltons and no subunit was observed. Two forms of chicken brain ChAc with different Km values for the substrates were eluted from agarose-hexane-CoA column. The pH optimum was estimated to be between pH 7.6-8.0. NaCl, KC1, Ca²⁺ and EDTA stimulated, while Cu²⁺, N-ethylmaleimide and CoA inhibited the enzyme preparation. The apparent Km values for acetyl-CoA and choline were, studied and were found to be similar to those of other mammalian species. The ChAc preparation also showed species specificity by the Ouchterlony double immuno diffusion test. Effect and mechanisms of salt and EDTA activation of ChAc activity are discussed. / Medicine, Faculty of / Graduate
383

Controle acústico híbrido da perda de transmissão sonora / Hybrid acustic control of sound transmission loss

Siviero, Diego Azevedo 07 August 2011 (has links)
Orientador: José Roberto de França Arruda / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T16:52:35Z (GMT). No. of bitstreams: 1 Siviero_DiegoAzevedo_D.pdf: 6891079 bytes, checksum: 7f974a708ef3ffdbbf5d21dd4528a176 (MD5) Previous issue date: 2011 / Resumo: O controle da transmissão sonora em painéis é um problema que tem despertado a atenção das indústrias automobilísticas, aeronáutica e aeroespacial. As estratégias de controle de ruído passivo utilizadas com esta finalidade não apresentam boa eficiência em todo espectro audível, pois apesar de ser uma solução robusta, não é eficaz na absorção de ruídos de baixas frequências (menos de 1kHz). Este trabalho apresenta o desenvolvimento de um protótipo de isolador acústico híbrido que agrega elementos do tradicional controle passivo (material poroso, espuma de melamina mais especificamente) e do controle ativo de ruídos (transdutores piezelétricos comandados por um sinal elétrico conveniente) para complementar a eficiência de absorção sonora em baixas frequências. Como a medição da perda de transmissão sonora não pode ser realizada diretamente, este estudo também apresenta uma simulação computacional comprovando a possibilidade de se atuar ativamente em outras grandezas acústicas para se obter o controle indireto da perda de transmissão sonora. O algoritmo de controle utilizado neste trabalho é o Filtered-X LMS normalizado, implementado no domínio do tempo e no domínio da frequência. Após a comprovação da efetividade do controle na simulação, um tubo de ondas planas foi construído para teste e desenvolvimento do isolador proposto. Finalmente, o protótipo foi aplicado a um painel reforçado fixado em uma janela que divide duas câmaras acústicas (uma anecóica e outra reverberante) para medir a perda de transmissão sonora do conjunto. Os resultados apontam um considerável aumento na perda de transmissão das baixas frequências no tubo de ondas planas. A aplicação do isolador no painel reforçado não apontou resultados conclusivos / Abstract: The control of transmission loss through panels is a problem that has attracted the attention of automotive, aeronautical and aerospace industries. The passive noise control strategies used for this purposed does not have high efficiency in all audible spectrum, although it consists in a robust solution, it is not effective in low frequency absorb (below 1kHz). This work presents the development of an acoustic insulator prototype that combines traditional passive noise control elements (porous materials, melamine foam more specifically) with active noise elements (piezoelectric transducer driven by a convenient electric signal) to complement the sound absorbing in low frequencies. As the transmission loss measuring cannot be performed instantaneously, this study also presents a computational simulation showing the possibility of actuating actively in other acoustical quantities to obtain the indirect control of the sound transmission loss. The active control algorithm used in this research is the normalized Filtered-X LMS, implemented in time and frequency domains. After verification of the effectiveness of this controller in the simulation, a plane wave duct was built for testing and development of the proposed isolator. Finally, the prototype was applied to a reinforced panel placed in a window that divides two acoustic chambers (anechoic and reverberant) to measure the sound transmission loss of the assembly. The results showed an increase in the low frequency transmission loss when the isolator was tested in the plane wave duct. The tests with the reinforced plate did not show conclusive results / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica
384

A Community of Isolation: An Ethnographic Examination of Mothering in Poverty and Its Impact on Food Security in Pinellas County, Florida

Terry, Amanda M. 16 September 2015 (has links)
The objective of this dissertation is to document the lived experience of mothering in poverty and the unique challenges the role of mother presents to maintaining food security. Millions of households in the United States are struggling to put food on the table, a problem made worse by the current economic recession and high food prices. Among them, households with children and specifically, single mothers, report the highest prevalence of food insecurity. While Federal food assistance programs are available to help alleviate this issue, the continued problem of hunger is a very real and pervasive concern for millions of American families. While there is a robust and comprehensive scholarly body of work focused on food security and nutrition, this study fills an important gap in the literature. By describing the unique social and cultural circumstances that accompany the transition to motherhood in a low-income setting, I connect the lived experienced of mothering with vulnerability to food insecurity. This is framed within the underlying assumption that the related experiences of expectant mothering and caring for an infant impart different risk factors for food insecurity. This study used a mixed methods approach to examine its objectives. These include semi-structured ethnographic interviews, participant observation, surveys and questionnaires and foodscape analysis. The mixed method design allowed for a holistic examination of the lived experience of mothers through narrative analysis, the visual representation of their foodscape through community mapping, and the triangulation of findings through administered surveys and questionnaires. The primary findings of this dissertation include identification of social, cultural and geographic patterns of maternal isolation among low-income women and their impact on food security. Results of this study indicate that the unique demands of mothering in a low-income setting present challenges to maintaining food security. Gaps in services provided to low-income mothers to address food insecurity were identified to include improving the social connectedness of expectant and new mothers. This study is intended to reach a wide target audience including students, practitioners, anthropological colleagues and policymakers. In an effort to translate the findings of this study into practical recommendations for action, the author calls for more research into the issue of maternal isolation and for policy initiatives to recognize the unique role mothering plays in contributing to household food security status.
385

Bacteriophage diversity in haloalkaline environments

Nemavhulani, Shonisani January 2013 (has links)
>Magister Scientiae - MSc / There are limited reports on virus population in haloalkaline environments; therefore the aim of this study was to investigate the genetic diversity and biology of bacteriophage communities in these environments. Bacteria were isolated to be used as phage hosts. One bacterium from Lake Magadi and four bacteria from Lake Shala were successfully isolated from sediment samples. A further two Lake Shala bacterial hosts from the IMBM culture collection were also used to isolate bacteriophages. Bacterial isolates were identified to be most closely related to Bacillius halodurans, Halomonas axialensis, Virgibacillus salarius, Bacillus licheniformis, Halomonas venusta, Bacillus pseudofirmus and Paracoccus aminovorans. Bacteriophages were screened using all bacteria against sediment samples from both Lake Shala and Lake Magadi. One phage was identified from Lake Magadi sediments (MGBH1) and two phages from Lake Shala sediments (SHBH1 and SHPA). TEM analysis showed that these phages belong to three different dsDNA phage families; Siphoviridae (MGBH1), Myoviridae (SHBH1) and Podoviridae (SHPA). All phages showed different genome sizes on agarose gel. Due to the small genome size, phage SHPA was chosen for further investigation. Partial, genome sequence analysis showed homology to both bacterial and phage proteins. A further investigation of phage diversity in this environment is essential using metagenomic approaches to understand these unique communities.
386

Isolamento e caracterização de estirpe de Frog Virus 3-símile detectada em rãs-touro gigante (Lithobates catesbeianus) no Estado de São Paulo / Isolation and characterization of Frog Virus 3-like strain detected in american bull frogs (Lithobates catesbeianus) in São Paulo State

Anna Luiza Farias Alencar 06 June 2016 (has links)
A aquicultura é apontada como um mercado estratégico para o desenvolvimento sustentável, produção de alimentos e ampliação de fronteiras inexploradas no Brasil. No entanto, como outros sistemas de produção animal, este setor enfrenta problemas com doenças resultantes de sua intensificação, como os aspectos sanitários da produção e a falta de estrutura para o diagnóstico das principais enfermidades infecciosas. Durante os últimos 20 anos, os vírus da família Iridoviridae, em especial membros do gênero Ranavirus, têm sido responsáveis por epizootias de grande impacto ecológico e econômico, envolvendo um grande número de espécies de peixes, anfíbios e répteis de importância na aquicultura de várias partes do mundo. No entanto, as informações sobre a ocorrência de infecções de peixes e anfíbios causadas por ranavírus no Brasil são limitadas. O presente projeto compreendeu o isolamento em cultivo celular de estirpe de Frog Virus 3-símile, no Estado de São Paulo, confirmada por sequenciamento nucleotídico do gene MCP e subsequente RFLP, assim como caracterização fenotípica e de cinética de replicação do isolado. Amostras de fígado, baço e rins de rãs-touro gigante provenientes de ranário comercial, positivas ao diagnóstico molecular para Ranavirus, foram utilizadas para isolamento viral em cultivo celular. Efeito citopático foi detectado na segunda passagem em células BF-2 e posterior confirmação do isolamento foi feita por PCR e RFLP. A caracterização fenotípica viral foi feita com microscopia eletrônica de transmissão, a qual permitiu a confirmação de morfologia semelhante às partículas de Ranavirus, além da realização de curva de replicação, indicando maiores títulos virais no quarto dia após inoculação. Também foi feito teste de susceptibilidade a solventes, que confirmou a presença de partículas envelopadas. Os resultados obtidos nesse estudo poderão contribuir para a futura compreensão da biologia dos iridovírus circulantes como agentes etiológicos de ranaviroses em anfíbios no Estado de São Paulo. / Aquaculture is appointed as a strategic market for sustainable development, food production and expansion of unexplored frontiers in Brazil. However, just like other animal production systems, this area faces problems due its intensification, like the production sanitation aspects and the lack of structure for the diagnosis of major infectious diseases. During the last 20 years, viruses from Iridoviridae family, especially Ranavirus genera, have been responsible for major economic and ecological impactant epizootic diseases in a great number of fish, amphibian and reptile species in many parts of the world. However, information on the occurrence of infections in fishes and amphibians caused by Ranavirus in Brazil are limited. In this context, this project aimed to isolate a Frog Virus 3-like strain detected in São Paulo state in cell culture, which was later confirmed by nucleotide sequencing of MCP gene and further RLFP technique and also phenotipical characterization and replication kinetics of the obtained strain. Liver, spleen and kidney samples from american bullfrogs from commercial frog ponds, positive by molecular diagnostic for Ranavirus, were used for viral isolation in cell culture. Citopathic effect was detected during the second passage in cells and later confirmed by PCR and RFLP. The viral characterization was carried out with transmission electronic microscopy, which confirmed similar morphology of viral particles to those of Ranavirus, besides the construction of a growth curve which indicated larger titres on the fourth day post inoculation. A test for solvent sensitivity was also performed and confirmed the presence of enveloped particles. The results obtained in this study will contribute to the understanding of the biology of the circulating iridovirus in São Paulo state as an etiological agent of Ranavirus infection in amphibians.
387

Single-Use Servers: A Generalized Design for Eliminating the Confused Deputy Problem in Networked Services

Lanson, Julian P. 11 May 2020 (has links)
Internet application servers are currently designed to maximize resource efficiency by servicing many thousands of users that may fall within disparate privilege classes. Pooling users into a shared execution context in this way enables adversaries not only to laterally propagate attacks against other clients, but also to use the application server as a "confused deputy" to gain escalated privileges against sensitive backend data. In this work, we present the Single-use Server (SuS) model, which detects and defeats these attacks by separating users into isolated, containerized application servers with tailored backend permissions. In this model, exploited servers no longer have unfettered access to the backend data or other users. We create a prototype implementation of the SuS model for the WordPress content management system and demonstrate our model's ability to neutralize real-world exploits against vulnerable WordPress versions. We find that the SuS model achieves a high level of security while minimizing the amount of code modification required for porting an application server. In our performance evaluation, we find that the CPU and latency overheads of the SuS model are very low, and memory consumption scales linearly. We generalize the SuS model to be applicable to a wide range of application server and backend resource pairs. With our modularized codebase, we port IMAP, a widely-used mail retrieval protocol, to the SuS model and find that doing so requires minimal effort.
388

Detection of Cardiovascular Anomalies: An Observer-Based Approach

Ledezma, Fernando 07 1900 (has links)
In this thesis, a methodology for the detection of anomalies in the cardiovascular system is presented. The cardiovascular system is one of the most fascinating and complex physiological systems. Nowadays, cardiovascular diseases constitute one of the most important causes of mortality in the world. For instance, an estimate of 17.3 million people died in 2008 from cardiovascular diseases. Therefore, many studies have been devoted to modeling the cardiovascular system in order to better understand its behavior and find new reliable diagnosis techniques. The lumped parameter model of the cardiovascular system proposed in [1] is restructured using a hybrid systems approach in order to include a discrete input vector that represents the influence of the mitral and aortic valves in the different phases of the cardiac cycle. Parting from this model, a Taylor expansion around the nominal values of a vector of parameters is conducted. This expansion serves as the foundation for a component fault detection process to detect changes in the physiological parameters of the cardiovascular system which could be associated with cardiovascular anomalies such as atherosclerosis, aneurysm, high blood pressure, etc. An Extended Kalman Filter is used in order to achieve a joint estimation of the state vector and the changes in the considered parameters. Finally, a bank of filters is, as in [2], used in order to detect the appearance of heart valve diseases, particularly stenosis and regurgitation. The first numerical results obtained are presented.
389

Inerter-added transmissibility to control base displacement in isolated structures

Morales, Cesar A. 15 January 2022 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / his paper proposes a Lean Green model for increasing profitability in small and medium-sized businesses operating within the plastics sector. This model will use the 5S methodology, KanBan for inventory control and TPM to standardize new corrective and preventive maintenance processes. As an added contribution, a Circular Economy process will be included to reuse products, thus reducing consumption and generating less solid waste. In this way, companies will not only prevent damaging the environment but will also guarantee their compliance with regulatory standards. As a result, an 11% reduction was observed in the acquisition of supplies and spare parts for machine maintenance along with a 4% reduction in the number of machine breakdowns.
390

Reverzibilní imobilizace DNA na nově syntetizovaných magnetických nosičích / Reversible immobilisation of DNA on newly designed magnetic carriers

Kubisz, Petr January 2010 (has links)
The aim of work was an optimization of separation deoxyribonucleic acid (DNA) with the use of nucleic acid reversible adsorption to the surface of magnetic particles coated by functional groups. Six carriers were verificated for DNA isolation: P (HEMA-co-GMA) ox, F-kol B 30 ox, F-kol 77 ox, F-kol B100 ox, F-kol 135 ox, coated with carboxyl groups and Perovskit 439 (coated by silicone). Bacterial DNA was isolated by phenol extraction procedure, first. DNA was reversibly bond to magnetis carrier in the presence of high concentration of NaCl ( 5 M) and poly (ethylene glycol) (PEG 6000). The final PEG and NaCl concentrations of 16.0 % (w/v) and 2.0 M, respectively, were used.DNA was eluted into TE buffer. The quality of extracted DNA was checked by PCR amplification. It was found out that although different quantities of DNA were isolated, the quality of isolated DNA was always compatible with PCR. Nanoparticles Perovskit 439 had the best separative characteristics in comparison to the other magnetic carriers because highest amounts of DNA was isolated. However, next optimisation of DNA separation procedure is required for the use of studied microspheres in real samples.

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