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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.
1

Characterization of Xylaria sp., the causal agent of taproot decline in Mississippi soybean

Becton, Hope 09 August 2019 (has links)
Taproot decline (TRD), caused by an undescribed species of Xylaria, is an emerging root disease of soybean in Mississippi. Xylaria sp. isolates were collected from soybean roots and used to characterize TRD distribution as well as optimal growth temperature, pathogenicity, alternative host range, in vitro pathogenicity, and fungicide sensitivity. The 24 selected Xylaria sp. isolates from the 2016 collection had a mean optimal growth temperature of 26.7°C, and were pathogenic to soybean; however, differences in virulence occurred among isolates. Five selected Xylaria sp. isolates produced stroma on six hosts: corn, cotton, peanut, rice, sorghum, and wheat. Xylaria sp. colonized corn, cotton, and soybean seed in vitro; however, only reduced germination in soybean. Three selected Xylaria sp. isolates were exposed to fungicide-amended potato dextrose agar with concentrations up to 100 ppm of commercial products typically used in soybean production systems. Xylaria sp. isolates were insensitive to all active ingredients except thiophanate-methyl.
2

Metagenomic analysis of root-associated microbiome of healthy and Taproot Decline-affected soybeans and identification of healthy soybean root endophytes with protective activity against the causal agent, Xylaria necrophora

Wesser, Uyen 09 December 2022 (has links) (PDF)
Plant roots are associated with a diverse microbial community of bacteria and fungi. The root microbiome communities associate with the root surface or penetrate the superficial layers of root tissues. It is of high agronomic interest to characterize root microbiomes and identify microbes with beneficial effects on plant defense against pathogens. Soybean taproot decline (TRD) is an emerging soil-borne disease caused by a fungus classified as Xylaria necrophora, challenging to control and with devastating effects on yield. Our group has initiated a study of the soybean root microbiome with three primary experiments: (I) perform a comparative study of root microbiomes and mycobiomes from healthy and TRD-affected soybean, (II) isolate, screen and (III) identify soybean root bacterial endophytes with anti-X. necrophora and anti-TRD properties. Our long-term objective is to discover and implement microbiome-based management techniques that enhance the health and yield of soybeans.
3

Zoneamento geoambiental com auxílio de lógica fuzzy e proposta de um geoindicador para caracterização do meio físico da Bacia do Rio do Peixe / Geoenvironmental zoning using fuzzy logic and proposal of a geoindicador to characterize Rio do Peixe basin environment

Silva, Sandra Fernandes da 05 July 2005 (has links)
O trabalho apresenta uma proposta metodológica para caracterização de aptidões e restrições do meio físico, considerando a variação contínua dos atributos e também a existência de gradação nos contatos entre as unidades. Os mapas do substrato rochoso e dos materiais inconsolidados foram obtidos utilizando-se de procedimentos da lógica fuzzy para representação da gradação nos contatos. As cartas de declividade, de menor extensão do percurso da água superficial, de potencial de escoamento superficial, de susceptibilidade à erosão e de potencial agrícola foram obtidas utilizando-se mapas numéricos e a variação contínua dos atributos. Para realização das operações de geoprocessamento foram utilizados o sistema de informação geográfica SPRING e a linguagem de programação LEGAL, que permitiram, tanto a representação dos contatos gradacionais (fuzzy) quanto a classificação contínua e o cruzamento das informações. Para avaliação de alterações introduzidas no meio, foi proposta a aplicação do atributo resistência à penetração do solo como geoindicador ambiental. As medidas de resistência à penetração foram feitas utilizando-se um novo equipamento, que consiste de um penetrômetro de solo acoplado a uma sonda TDR. Este procedimento permitiu a caracterização de modificações das condições naturais de compactação dos solos da bacia, frente às atividades de uso do terreno vigentes, bem como forneceu um parâmetro para comparação frente a modificações de uso futuras. O zoneamento da área foi obtido a partir da adoção das unidades de lanforms como unidades de compartimentação, o que possibilitou a caracterização das aptidões, restrições e conflitos de uso / This study presents a methodological technique to characterize environmental restrictions and aptitudes considering continuous variation in the attributes and gradation in contato between units. Fuzzy logic procedures were used to generate representation of contact gradation for rocky substratum and unconsolidated materials maps. Continuous attribute variation and numerical maps were used to produce slope least water runoff distance, runoff potential, erosion susceptibility and agricultural potential charts. Geoprocessing operations using the SPRING geographical information system and its LEGAL programming language permitted the representation of gradation in contac (fuzzy), continuous classification nad information crossing. Soil penetration resistance was proposed as the environmental geondicator to evaluate environmental changes. Measurement of soil penetration resistance by a soil penetrometer connected to a TDR proble permitted the characterization and specification of natural basin soil compaction conditions and the comparison of different occupation activities on the soil. A parameter for future changes due to soil occupation was therefore identified by this procedure. Area zoning was attained by the adoption of landform units as segmentation units. The characterization of aptitudes, restrictions and conflicts in occupation were achived by this procedure
4

Zoneamento geoambiental com auxílio de lógica fuzzy e proposta de um geoindicador para caracterização do meio físico da Bacia do Rio do Peixe / Geoenvironmental zoning using fuzzy logic and proposal of a geoindicador to characterize Rio do Peixe basin environment

Sandra Fernandes da Silva 05 July 2005 (has links)
O trabalho apresenta uma proposta metodológica para caracterização de aptidões e restrições do meio físico, considerando a variação contínua dos atributos e também a existência de gradação nos contatos entre as unidades. Os mapas do substrato rochoso e dos materiais inconsolidados foram obtidos utilizando-se de procedimentos da lógica fuzzy para representação da gradação nos contatos. As cartas de declividade, de menor extensão do percurso da água superficial, de potencial de escoamento superficial, de susceptibilidade à erosão e de potencial agrícola foram obtidas utilizando-se mapas numéricos e a variação contínua dos atributos. Para realização das operações de geoprocessamento foram utilizados o sistema de informação geográfica SPRING e a linguagem de programação LEGAL, que permitiram, tanto a representação dos contatos gradacionais (fuzzy) quanto a classificação contínua e o cruzamento das informações. Para avaliação de alterações introduzidas no meio, foi proposta a aplicação do atributo resistência à penetração do solo como geoindicador ambiental. As medidas de resistência à penetração foram feitas utilizando-se um novo equipamento, que consiste de um penetrômetro de solo acoplado a uma sonda TDR. Este procedimento permitiu a caracterização de modificações das condições naturais de compactação dos solos da bacia, frente às atividades de uso do terreno vigentes, bem como forneceu um parâmetro para comparação frente a modificações de uso futuras. O zoneamento da área foi obtido a partir da adoção das unidades de lanforms como unidades de compartimentação, o que possibilitou a caracterização das aptidões, restrições e conflitos de uso / This study presents a methodological technique to characterize environmental restrictions and aptitudes considering continuous variation in the attributes and gradation in contato between units. Fuzzy logic procedures were used to generate representation of contact gradation for rocky substratum and unconsolidated materials maps. Continuous attribute variation and numerical maps were used to produce slope least water runoff distance, runoff potential, erosion susceptibility and agricultural potential charts. Geoprocessing operations using the SPRING geographical information system and its LEGAL programming language permitted the representation of gradation in contac (fuzzy), continuous classification nad information crossing. Soil penetration resistance was proposed as the environmental geondicator to evaluate environmental changes. Measurement of soil penetration resistance by a soil penetrometer connected to a TDR proble permitted the characterization and specification of natural basin soil compaction conditions and the comparison of different occupation activities on the soil. A parameter for future changes due to soil occupation was therefore identified by this procedure. Area zoning was attained by the adoption of landform units as segmentation units. The characterization of aptitudes, restrictions and conflicts in occupation were achived by this procedure
5

Har ketamin effekt mot terapiresistent depression?

Arildsson, Mathilda January 2019 (has links)
Depression är ett syndrom som drabbar mer än 300 miljoner människor i världen. Tillståndet förekommer i individuella variationer men vanliga symtom är nedstämdhet, energiförlust, störningar av sömn och aptit samt känslor av skuld och skam. En svår depression kan innebära lidande och stor funktionsförlust för den drabbade. Idag används både psykologisk och farmakologisk behandling, men det finns en problematik kring att det kan dröja veckor eller månader innan klinisk effekt ses av antidepressiva läkemedel. Därutöver blir en tredjedel av patienterna inte tillräckligt hjälpta av den behandling som finns att tillgå. Detta brukar kallas terapiresistent depression (TRD) och är för närvarande svårbehandat. Ketamin är ett narkotikaklassat läkemedel som används för induktion och underhåll av anestesi men som även förekommer som missbruksdrog. Fynd har visat att engångstillförsel av ketamin eventuellt kan ge en snabb antidepressiv effekt hos patienter med TRD. Ketamin är för närvarande inte godkänt för indikationen depression i Sverige. Syftet med denna litteraturstudie var att utvärdera om ketamin har effekt mot TRD. Fem randomiserade kontrollerade studier som hämtats ur databasen PubMed användes. I tre studier undersöktes intravenös tillförsel av ketamin varav en gav upprepade doser, en studie undersökte intravenöst esketamin i varierande doser och en studie undersökte effekten av intranasalt ketamin. Sammantaget visar resultatet att ketamin har effekt mot terapiresistent depression. Efter 24 timmar kunde statistiskt signifikanta skillnader avseende depressionens svårighetsgrad observeras hos de som fått ketamin jämfört med placebo (p <0,05). Ketamin gav 7–16 poängs större reduktion av depressiva symtom än placebo enligt använd skattningsskala, vilket motsvarade en genomsnittlig förändring från svår/medelsvår depression till mild depression. Resultatet visade även statistiskt signifikanta skillnader avseende behandlingsrespons (minst 50 % reduktion av symtompoäng på använd skattningsskala) efter 24 timmar (p <0,05). Andelen patienter med respons varierade mellan 44–71 % jämfört med 0–6 % för placebo och 28 % för aktiv placebo (midazolam). Även om resultatet från aktuella studier verkar lovande för ketamin som antidepressiv behandling krävs ytterligare studier på långtidseffekter och säkerhet vid upprepad tillförsel i en större studiepopulation. / Depression is a syndrome characterized by depressed mood, loss of interest and energy, feelings of guilt or worthlessness and thoughts of death and suicide. Over 300 million people suffer from depression and it is one of the leading causes of disability in the world. Today’s treatment for depression includes psychological treatment as well as pharmacological treatment. While there are many antidepressant drugs, it can take up to weeks or even months before a clinical effect in the severity of the depression can be noticed. In addition, one third of the patients do not achieve remission. These patients, after treatment with two antidepressant medications given at adequate doses for an adequate duration, are considered to have treatment-resistant depression (TRD). Ketamine is a drug long used for its anesthetic and analgesic effects, but it is also known as a party-drug that can cause out-of-body experience. However, it has also been found that a single-dose ketamine may give people with TRD a rapid antidepressant effect, within 24 hours. In contrast to current antidepressant medications which primarily acts on the monoaminergic system, ketamine instead acts on the glutamatergic system. The aim of this study was to evaluate if ketamine has an effect on people suffering from TRD. This study is a literature review where five randomized controlled trials on the effect of ketamine in patients with TRD have been analyzed. Four studies evaluated the effect of intravenous ketamine where one of them used a varied dose frequency and one of them used esketamine in various doses. The fifth study evaluated the effect of intranasal administration of ketamine. All studies were found in the database PubMed. The overall result shows that ketamine has an effect on TRD. After 24 hours all the studies showed a significant improvement in the severity of the depression with ketamine treatment compared to placebo (p <0.05). Ketamine treatment resulted in a 7-16 points larger reduction in depressive symptoms on the scales used compared to placebo. This represents on average a change from severe/moderately severe depression to mild depression. There was also a significant difference in response (at least 50 % reduction in points from baseline on the scale used) after 24 hours with ketamine treatment compared to placebo (p <0.05). The proportion of ketamine treated patients with response varied between 44-71 % compared to 0-6 % for placebo and 28 % for active placebo (midazolam). Even though ketamine seems to have an effect on patients with TRD there is still limited knowledge of how the antidepressant effect shall be maintained and the safety of long-term use. Further studies are needed to determine if ketamine will be an option in future antidepressant treatment against TRD.
6

MODELISATION DES REARRANGEMENTS V(D)J AU NIVEAU DU LOCUS TRA/TRD

Simonet, Maria-Ana 22 December 2008 (has links) (PDF)
Les lymphocytes T expriment à leur surface des récepteurs (TR) composés de chaînes αβ ou γδ, chargés de reconnaitre des peptides antigéniques. Une chaîne d'un TRα donnée est le résultat de l'assemblage de gènes variable (V), jonction (J) et constant (C) sous le contrôle d'un mécanisme de recombinaison spécifique dénommé " recombinaison V(D)J ". De part le nombre important de gènes V et J dispersés sur plus de 1 méga base et des segments V dupliqués chez la souris, il est quasiment impossible d'établir la diversité combinatoire VJ exacte et surtout leurs fréquences par les techniques actuelles de biologie moléculaire. Aussi pour appréhender ces questions, nous avons développé un modèle de simulation des réarrangements des combinaisons VJ codant pour la chaine TRα chez la souris. Le modèle implémenté est basé sur des fenêtres d'accessibilités flexibles, des vitesses d'ouverture variables et inclue aussi un temps de maturation entre deux réarrangements. Il permet de rendre compte de la dynamique et de la variabilité de la chaine α en termes de répertoire (nombre et fréquence des combinaisons). Il propose que 2 à 3 réarrangements sont suffisant pour utiliser l'ensemble des segments J et permet aussi de donner un profil global de l'ensemble des combinaisons VJ. En parallèle, une analyse des réarrangements VJ a été réalisée chez l'homme. Cette analyse permet de visualiser les profils des combinaisons VJ expérimentaux et permettra de valider l'adaptation du modèle de simulation des réarrangements des chaines TRα chez la souris aux chaines TRα chez l'homme. Le modèle pourra servir d'outils pour analyser les variations entre répertoire sain et répertoire altéré ou modifié dans le cas de pathologies ou de reconstruction du répertoire immunitaire après une greffe de moelle osseuse.

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