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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.
221

Purificação e caracterização da fração neurotóxica da peçonha da anêmona do mar Anthopleura cascaia / Purification and characterization of the neurotoxic fraction from the venom of the sea anemone Anthopleura cascaia

Bruno Madio 14 June 2012 (has links)
A peçonha de anêmonas do mar é uma fonte conhecida de compostos bioativos, incluindo peptídeos, que atuam em canais voltagem-dependentes. Foram descritos 4 tipos de neurotoxinas de anêmonas do mar, que atuam em canais NaV e 4 tipos que atuam em canais KV. Essas toxinas têm permitido discriminar subtipos de canais voltagem-dependentes, estreitamente relacionados, e constituem poderosas ferramentas para estudar o funcionamento e estrutura desses canais. Neste estudo, foram isolados e caracterizados três peptídeos da fração neurotóxica da anêmona do mar Anthopleura cascaia. Esses peptídeos foram nomeados como AcaIII1425, AcaIII2970 e AcaIII3090, onde Aca faz referência a espécie e os números seguem os resultados obtidos nas etapas de purificação. A peçonha foi extraída por meio de estímulos elétricos e purificada por gel-filtração (Sephadex G-50) e fase reversa por HPLC (C-18). As massas moleculares foram obtidas por meio de MALDI-TOF, apresentando 3337,4 Da para a AcaIII1425, 4881,7 Da para a AcaIII2970 e 4880,5 Da para AcaIII3090. Através da técnica de voltage-clamp, esses peptídeos foram testados em diferentes subtipos de canais NaV e KV expressados em ovócito de Xenopus. As toxinas AcaIII2970 e AcaIII3090 retardam, de maneira seletiva, a inativação rápida dos subtipos rNaV1.3, mNaV1.6 e hNaV1.5, enquanto que as outras isoformas testadas permaneceram inalteradas. É importantemente salientar que, a AcaIII2970 e AcaIII3090 também foram examinadas no canal de inseto DmNaV1, revelando uma clara \"filo-seletividade\" na eficácia da atividade das toxinas. A AcaIII2970 e AcaIII3090 inibem fortemente a inativação do canal NaV de inseto, resultando em um aumento na amplitude do pico da corrente e removendo completamente a inativação rápida. Para quantificarmos essa \"filo-seletividade\", foram construídas curvas da dependência da concentração no retardo da inativação induzida pelas toxinas AcaIII2970 e AcaIII3090 nos canais em que apresentaram maior eficácia. Os IC50 foram obtidos após a plotagem dos dados em uma curva sigmoidal. Para a AcaIII2970, os seguintes valores de IC50 foram obtidos: DmNaV1 = 162,19 ± 11,22 nM, mNaV1.6 = 645,92 ± 18,52 nM, rNaV1.3 = 572,56 ± 44,96 nM. Para a AcaIII3090, os seguintes valores de IC50 foram obtidos: DmNaV1 = 99,03 ± 9,25 nM, mNaV1.6 = 158,30 ± 33,86 nM, rNaV1.3 = 371,60 ± 6,48 nM. A AcaIII1425 atua, bloqueando, de modo seletivo os subtipos rKV1.1, rKV1.6 e rKV4.3, enquanto que as outras isoformas testadas permaneceram inalteradas. Devido à maior especificidade da toxina AcaIII1425 pelos subtipos rKV1.1 e rKV1.6, foram realizados ensaios de bloqueio da corrente do canal em função da concentração da toxina (curva dose-resposta). Os valores de IC50 para os subtipos rKV1.1 e rKV1.6 são de 7642,98 ±1601,65 nM e 241,65 ±4,27 nM, respectivamente. Desta forma, a AcaIII1425 é cerca de 32 vezes mais potente em canais do subtipo rKV1.6 do que em relação aos canais do subtipo rKV1.1. A estrutura primária das toxinas foram determinadas por degradação de Edman. A sequência parcial da AcaIII2970 e AcaIII3090 revelou que estas são similares a toxinas de canal de sódio do tipo1 de anêmonas do mar. A sequência completa da AcaIII1425 não apresenta similaridade com toxinas de anêmonas do mar, mas é similar a toxinas de Conus e aranha que possuem um motivo estrutural conhecido como ICK. Dessa forma, propomos que a AcaIII1425 seja um novo grupo de toxinas de anêmonas do mar que bloqueiam KV. Dado o ineditismo da toxina AcaIII1425, foram feitos experimentos in silico para obtermos um maior refinamento do mecanismo de interação entre a toxina e o canal rKV1.6. Estes experimentos indicaram que diferentes regiões dos canais KV são importantes para a seletividade e potência da toxina, corroborando com as propostas que vem sendo descritas / The venom of sea anemones is a known source of bioactive compounds, including peptides that act on voltage-gated ion channels. Four types of neurotoxins from sea anemones, acting on NaV channels, and four types acting on KV channels, have been reported. These toxins have developed the ability to discriminate closely related subtypes of voltage-gated channels, making them powerful tools to studying the function and structure of these channels. In this study, we isolated and characterized three peptides of the neurotoxic fraction from the venom of the sea anemone Anthopleura cascaia. These peptides were named as AcaIII1425, and AcaIII2970 AcaIII3090, where Aca refers to the species and the following numbers refer to results obtained in the purification steps. The venom was milked by electric shock and purified by molecular exclusion (Sephadex G-50) and reverse phase HPLC (C-18). Their molecular weights are 3337.4 Da to AcaIII1425, 4881.7 Da to AcaIII2970 and 4880.5 Da to AcaIII3090, obtained through a MALDI-TOF. Using the voltage-clamp technique, we have assayed the effects of these peptides on different subtypes of NaV and KV channels expressed in Xenopus oocytes. AcaIII2970 and AcaIII3090 toxins selectively slow down the fast inactivation of rNaV1.3, mNaV1.6 and hNaV1.5 subtypes, while the other mammalian isoforms remained unaffected. Importantly, AcaIII2970 and AcaIII3090 were also examined in insect DmNaV1 channel, revealing a clear phyla-selectivity with regards to the efficacy of the toxin. AcaIII2970 and AcaIII3090 strongly inhibit the inactivation of the insect NaV channel, resulting in an increase in the amplitude of the peak current, and complete removal of the fast and steady-state inactivation. In order to quantify this \"phyla-selectivity\", curves of the concentration dependence of the delayed inactivation induced by AcaIII2970 and AcaIII3090 toxins channels with higher efficacy, were built. After plotting the data on a sigmoidal curve the IC50 values were obtained. For AcaIII2970, the following IC50 values were obtained: DmNaV1 = 162.19 ± 11.22 nM, mNaV1.6 = 645.92 ± 18.52 nM and rNaV1.3 = 572.56 ± 44.96 nM. For AcaIII3090, the following IC50 values were obtained: DmNaV1 = 99.03 ± 9.25 nM, mNaV1.6 = 158.30 ± 33.86 nM and rNaV1.3 = 371.60 ± 6.48 nM. AcaIII1425 acts, selectively, blocking rKV1.1, rKV1.6 and rKV4.3 subtypes, while the others isoforms tested remained unaltered. Due the higher specificity of AcaIII1425 to rKV1.1 and rKV1.6 subtypes, assays were performed to evaluate the blocking channel current versus toxin concentration (dose-response curve). IC50 values for the subtypes rKV1.6 and rKV1.1 are 7642.98 ± 1601.65 nM and 241.65 ± 4.27 nM, respectively. Thus, AcaIII1425 is about 32 times more potent in the rKV1.6 than in the rKV1.1 channel. The primary structure of the toxins was determined by the Edman degradation. The partial sequence of AcaIII2970 and AcaIII3090 revealed that these toxins are similar to the type 1 sodium channel sea anemones neurotoxins. The complete sequence of AcaIII1425 has no similarity with other sea anemone toxins, but is similar to the Conus and spider neurotoxins which have a structural motif known as ICK. Thus, we propose that AcaIII1425 comprises a new group of sea anemones toxins that block KV channels. Given the unprecedented nature of the toxin AcaIII1425, in silico assays were carried out in order to further refining the proposed mechanism underlying the interaction between the toxin and the rKV1.6 channel. The results indicate that, in agreement to what has been proposed elsewhere, different regions of the KV channels are important for the toxin selectivity and potency
222

Loteamentos fechados / Real estate vacant lands

Eleusina Lavôr Holanda de Freitas 31 March 2008 (has links)
Este trabalho estuda o novo produto imobiliário que ganhou espaço na última década no Brasil: os loteamentos fechados. Mudanças estão sendo sentidas na configuração do espaço urbano brasileiro, notadamente nas grandes metrópoles, pois emerge em nossas cidades um novo padrão de segregação urbana, especialmente no que se refere às áreas residenciais, com a proliferação de condomínios e loteamentos fechados. A pesquisa empírica foi realizada na Região Metropolitana de Campinas, região de destaque por apresentar altos índices de dispersão. O objetivo principal do trabalho é investigar os motivos pelos quais os loteamentos fechados tornaram-se o principal produto imobiliário a partir dos anos 1990, no Brasil e em diversos países do mundo, especialmente da América Latina. Para tanto, resgata-se o processo de urbanização brasileira e os impactos da globalização sobre o território das cidades, como a fragmentação do território e a urbanização dispersa. O trabalho aborda também a discussão jurídica sobre o tema dos loteamentos fechados. Traz a discussão entre prefeituras, loteadores e Ministério Público, no sentido de entender de que forma a burla da lei se dá. Quanto à motivação para a moradia intramuros, discute-se o assunto sob a luz de estudos elaborados por pesquisadores em diversos paises, buscando localizar a realidade brasileira e compreender suas origens, referências e conseqüências do processo. / This work studies a new real estate practice that has proliferated in the last decade in Brazil: Private gated communities. Changes can be seen in the Brazilian urban space configuration, especially in the great metropolis. Emerges in our cities a new pattern of urban segregation, especially in what makes reference to the residential areas, with condos and gated community proliferation. The empirical research was carried at Campinas Metropolitan Region, a featured region by its \"high dispersions index\". The main objective of this work is to investigate the reasons why gated communities became the main real estate choice from the 90\'s, in Brazil and in different countries in the world, especially in Latin America. Therefore, the Brazilian urbanization process is rescued and the globalization impacts on the cities territories, as the territory fragmentation and the dispersed urbanization. The work also approaches the Law discussion on gated communities. Brings the discussions between the city halls, real estate agents and the Public Ministry, in the sense of understanding in which way the law has been broken. Referring to the reasons for the \"within the walls\" residence, the subject is discussed through studies carried by researches in different countries, seeking to locate the Brazilian reality and understand its origins, references and process consequences.
223

Condomínios fechados na Região Metropolitana de São Paulo: fim do modelo centro rico versus periferia pobre? / São Paulo Metropolitan Area gated communities: the end of the rich center versus poor suburbia pattern?

Maria Camila Loffredo D\'Ottaviano 08 April 2008 (has links)
Os condomínios e loteamentos fechados constituem um fenômeno urbano que vem se espalhando por todas as metrópoles brasileiras. Desde o final dos anos 1980, podemos observar um grande aumento no número de condomínios fechados dentro da Região Metropolitana de São Paulo (RMSP). Os condomínios e loteamentos fechados, antes destinados à moradia da classe alta e localizados em grandes áreas das zonas periféricas da RMSP, atualmente atendem outras classes sociais e possuem características bastante distintas (tamanho da gleba, unidade habitacional, serviços coletivos). A preocupação com conforto foi suplantada pela necessidade de segurança e pelo status. A proliferação desses loteamentos e condomínios fechados nos últimos quinze anos vem modificando a configuração espacial de algumas áreas da Região Metropolitana. Segundo alguns autores, o padrão centro rico versus periferia pobre, que caracterizou os estudos sobre a RMSP, entre os anos 1940 e 1980, alterou-se na última década para um modelo fractal de segregação. Esta Tese pretende verificar a pertinência do novo modelo fractal de segregação espacial, tomando como referência os condomínios horizontais residenciais fechados, e mostrar, a partir de levantamento realizado na Região Metropolitana de São Paulo, que parte das premissas relativas aos condomínios fechados não são absolutas. / Gated communities constitute an urban phenomenon that is nowadays spreading all over the Brazilian metropolis. Since the 1980s, we can observe an increasing number of gated communities within the São Paulo Metropolitan Area (SPMA). The gated communities, initially located at suburban areas and used by upper classes, at the present time serve other social classes and have new and distinct characteristics (size and location, houses sizes, services at the collective areas, etc). The initial concerning to comfort was substituted by the need of security and possibly the search for status. This Thesis analyses if the new fractal pattern of spatial segregation has overlapped the rich center X poor suburbia pattern that characterized the SPMA between 1940 and 1980, using the gated communities as case studies. And also pretends to demonstrate that part of the premises about gated communities is not absolute.
224

Weak Governance, Divided Residents: The Development of Gated Communities in Guatemala City

Dalby, Laura January 2013 (has links)
This thesis asks the question: how can one describe the development of gated communities in Guatemala City? It collects and analyzes data on gated communities in Guatemala City in order to explore the nature of their development in a violent geographical region, which has also been neglected by the academic community. It argues that the development of gated communities in Guatemala City does not fit the mutually exclusive ‘security’ argument as scholars have made. Instead, a mixture of economic factors, social status, weak governance, and security concerns are involved as large private corporations draw upon security-related fears, unregulated development of real estate and weak governance, resulting in a disorganized model of spatial organization. This study adds to the growing body of literature on gated communities by laying the groundwork needed to fill the gap that currently exists in Central America.
225

Symboliskt värde för ett taggtrådsstängsel : Taggtråd som svårtolkad och flertydig symbol mellan två lägenhetshus i Kviberg

Eriksson, Niclas January 2020 (has links)
Denna uppsats syftar till att beskriva vilket symboliskt värde ett taggtrådsstängsel mellan två lägenhetshus i området Kviberg som ligger i Göteborg, vad det representerar och vilka processer som föranlett stängslet. Enligt den part som låtit taggtrådsstängslet komma upp är anledningarna framförallt skadegörelse och vandalism, men varför finns taggtrådsstängslet här och vad är det en symbol för? Uppsatsen visar hur symboler blir multivokala med ett flertal olika tolkningar inom sig. Hur dessa tolkningar skapar en upplevd känsla av enighet och gemenskap som av flera faktorer blir till verklighet i form av avgränsning med taggtråd. Det beskrivs hur de två husen med en gemensam innergård får en ’vi och de’-känsla och hur denna känsla kan beläggas med skapandet av ’community’ som innefattar avskärmning och utestängning. Slutsatsen är bland annat att argument så som: skydd från vandalisering och skadegörelse som används för att upprätthålla taggtrådsstängslet inte till fullo kan efterlevas med taggtrådsstängslet. Det blir istället en symbol för hur man vill identifiera sig själv och sin tillhörighet.
226

On The Effectiveness of Multi-TaskLearningAn evaluation of Multi-Task Learning techniques in deep learning models

Tovedal, Sofiea January 2020 (has links)
Multi-Task Learning is today an interesting and promising field which many mention as a must for achieving the next level advancement within machine learning. However, in reality, Multi-Task Learning is much more rarely used in real-world implementations than its more popular cousin Transfer Learning. The questionis why that is and if Multi-Task Learning outperforms its Single-Task counterparts. In this thesis different Multi-Task Learning architectures were utilized in order to build a model that can handle labeling real technical issues within two categories. The model faces a challenging imbalanced data set with many labels to choose from and short texts to base its predictions on. Can task-sharing be the answer to these problems? This thesis investigated three Multi-Task Learning architectures and compared their performance to a Single-Task model. An authentic data set and two labeling tasks was used in training the models with the method of supervised learning. The four model architectures; Single-Task, Multi-Task, Cross-Stitched and the Shared-Private, first went through a hyper parameter tuning process using one of the two layer options LSTM and GRU. They were then boosted by auxiliary tasks and finally evaluated against each other.
227

Segregerande praktiker på bostadsmarknaden / Segregating practices in the housing market

Durrani, Sonia January 2020 (has links)
The purpose of this thesis was to study the requirement profile for obtaining a newly produced rental apartment via the municipal housing queue in Stockholm and what perceptions and differences about the geographical areas of the housing are conveyed in the process. This has been researched in relation to the new housing policy regarding the political incitement of market rents in Sweden. This study was conducted with a focus on vulnerable groups in society. In this study, a qualitative content analysis was used as the research method and the empirical data consists of rental advertisements from the statistical service of The Stockholm Housing Agency. The selected theories that have been applied in the analysis are Goffman's theory of stigma and the theory of social constructivism. The results of the study show that there is a lack of suitable and available forms of housing for low-income households in the municipal housing market as the majority of landlords do not accept unemployment insurance, social welfare or sickness benefit as a source of income. As an outcome, it is not possible to obtain a rental apartment via the municipal queue if you belong to that category of income. The results also show segregating patterns in the landlords' qualification requirements, as they demand a significantly higher gross income for housing in residential areas with a high socio-economic status, while requirements are more relaxed in areas with lower incomes. The results also show that the marketing of the housing is clearly aimed at a specific target group through language use. In summary, the results show that segregating practices take place in the municipal housing market as low-income households are not given access to resource-rich areas due to high income requirements and a strategic marketing that communicates what type of people are ideal for living in the area.
228

Swedish News for Koreans : A study on ethnic media for Koreans in Sweden

Mosesson, Marcus January 2020 (has links)
This study investigates a Facebook page named Sŭweden nyusŭ, which stands as an example of ethnicmedia targeting Koreans living in Sweden. Having gatekeeping theory as the theoretical frameworkand using a quantitative-qualitative media content analysis, the study looks at what news topics andnews sources are most used by the page, whether and how the news are presented objectively orsubjectively, as well as how the page’s followers react to the page’s content and how the page’sadministrator deals with these reactions. The study found that news topics related to economy andpolitics are the most prevalent, while the daily Dagens Nyheter is the most cited news source. Some ofthe news stories are presented subjectively, and the followers’ reactions are in general positive butalso inquiring and occasionally even negative and critical. The administrator usually tries to cater forthe followers’ demands and questions, but sometimes ignores or even questions their remarks. As thestudy also has the general goal of getting insight into the Korean community in Sweden, the findingssuggest the following. Firstly, Sŭweden nyusŭ compensates for what the community’s few existingethnic media channels lack. Secondly, some Koreans in Sweden who lack Swedish language skillsmay even be considered poorly integrated into the Swedish majority society. However, as forKoreans’ level of integration into the Swedish majority society, further research is needed in order toconfirm what the actual state is. The study therefore recommends more research to be conducted onthis topic, as well as on the subject of ethic media in Sweden in general.
229

P/Q Type Calcium Channel Cav2.1 Defines a Unique Subset of Glomeruli in the Mouse Olfactory Bulb

Pyrski, Martina, Tusty, Mahbuba, Eckstein, Eugenia, Oboti, Livio, Rodriguez-Gil, Diego J., Greer, Charles A., Zufall, Frank 04 September 2018 (has links)
Voltage-gated calcium (Cav) channels are a prerequisite for signal transmission at the first olfactory sensory neuron (OSN) synapse within the glomeruli of the main olfactory bulb (MOB). We showed previously that the N-type Cav channel subunit Cav2.2 is present in the vast majority of glomeruli and plays a central role in presynaptic transmitter release. Here, we identify a distinct subset of glomeruli in the MOB of adult mice that is characterized by expression of the P/Q-type channel subunit Cav2.1. Immunolocalization shows that Cav2.1+ glomeruli reside predominantly in the medial and dorsal MOB, and in the vicinity of the necklace glomerular region close to the accessory olfactory bulb. Few glomeruli are detected on the ventral and lateral MOB. Cav2.1 labeling in glomeruli colocalizes with the presynaptic marker vGlut2 in the axon terminals of OSNs. Electron microscopy shows that Cav2.1+ presynaptic boutons establish characteristic asymmetrical synapses with the dendrites of second-order neurons in the glomerular neuropil. Cav2.1+ glomeruli receive axonal input from OSNs that express molecules of canonical OSNs: olfactory marker protein, the ion channel Cnga2, and the phosphodiesterase Pde4a. In the main olfactory epithelium, Cav2.1 labels a distinct subpopulation of OSNs whose distribution mirrors the topography of the MOB glomeruli, that shows the same molecular signature, and is already present at birth. Together, these experiments identify a unique Cav2.1+ multiglomerular domain in the MOB that may form a previously unrecognized olfactory subsystem distinct from other groups of necklace glomeruli that rely on cGMP signaling mechanisms.
230

Fluorescent Visualization of Cellular Proton Fluxes

Zhang, Lejie 06 September 2018 (has links)
Proton fluxes through plasma membranes are essential for regulating intracellular and extracellular pH and mediating co-transport of metabolites and ions. Although conventional electrical measurements are highly sensitive and precise for proton current detection, they provide limited specificity and spatial information. My thesis focuses on developing optical approaches to visualize proton fluxes from ion channels and transporters. It has been demonstrated that channel-mediated acid extrusion causes proton depletion at the inner surface of the plasma membrane. Yet, proton dynamics at the extracellular microenvironment are still unclear. In Chapter II, we developed an optical approach to directly measure pH change in this nanodomain by covalently attaching small-molecule, fluorescent proton sensors to the cell’s glycocalyx using glyco-engineering and copper free ‘click’ chemistry. The extracellularly facing sensors enable real-time detection of proton accumulation and depletion at the plasma membrane, providing an indirect readout of channel and transporter activity that correlated with whole-cell proton current. Moreover, the proton wavefront emanating from one cell was readily visible as it crossed over nearby cells. The transport of monocarboxylates, such as lactate and pyruvate is critical for energy metabolism and is mainly mediated by proton-coupled monocarboxylate transporters (MCT1-MCT4). Although pH electrodes and intracellular fluorescent pH sensors have been widely used for measuring the transport of proton-coupled MCTs, they are unable to monitor the subcellular activities and may underestimate the transport rate due to cell’s volume and intracellular buffering. In Chapter III, we used the Chapter II approach to visualize proton-coupled transport by MCT1-transfected HEK293T cells and observed proton depletion followed by a recovery upon extracellular perfusion of L-lactate or pyruvate. In addition, we identified a putative MCT, CG11665/Hrm that is essential for autophagy during cell death in Drosophila. The results demonstrate that Hrm is a bona fide proton-coupled monocarboxylate transporter that transports pyruvate faster than lactate. Although the approach developed in Chapter II enables visualization of proton fluxes from ion channels and transporters, it’s not applicable in some cell types which cannot incorporate unnatural sialic acid precursors into their glycocalyx, such as INS-1 cells and cardiomyocytes. To address this, in Chapter IV we developed a pH-sensitive, fluorescent WGA conjugate, WGA-pHRho that binds to endogenous glycocalyx. Compared to the results in Chapter II and III, cell surface-attached WGA-pHRho has similar fluorescent signals in response to proton fluxes from proton channel Hv1, omega mutant Shaker-IR R362H and MCT1. With WGA-pHRho, we were able to label the plasma membrane of INS-cells and cardiomyocytes and visualized the transport activity of MCT1 in these cells. Taken together, these findings provide news insights into proton dynamics at the extracellular environment and provide new optical tools to visualize proton fluxes from ion channels and transporters. Moreover, the modularity of the approaches makes them adaptable to study any transport events at the plasma membrane in cells, tissues, and organisms.

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