Global ETD Search

1	Nelineární elektro-ultrazvuková spektroskopie rezistorů / Non-Linear Electro-Ultrasonic Spectroscopy of Resistive Materials Tofel, Pavel January 2012 (has links) Elektro-ultrazvuková spektroskopie je založena na interakci dvou signálů, elektrického střídavého signálu s frekvencí fE a ultrazvukového signálu s frekvencí fU. Ultrazvukový signál mění vzdálenost mezi vodivými zrny ve vzorku a tím mění jeho celkový elektrický odpor R. Změna odporu R je proměnná s frekvencí ultrazvukového signálu fU. Vzorek, který obsahuje mnoho defektů ve své struktuře, vykazuje vysokou změnu odporu R v porovnání se vzorkem bez defektů při stejné hodnotě ultrazvukového a elektrického signálu. V disertační práci je popsána elektro-ultrazvuková metoda na tlustovrstvých rezistorech, hořčíkových slitinách, monokrystalech Si a CdTe, varistorech a také jeden z prvních pokusů aplikace elektro-ultrazvukové spektroskopie na horninové vzorky a tak diagnostikovat jejich stav poškození. V našem případě byl proměřen vzorek žuly. Jelikož se jedná o nedestruktivní metodu testování, tak má tato metoda velmi perspektivní budoucnost. Tato metoda je citlivá na všechny defekty ve vzorku. Její výhodou je, že se měří velikost signálu ne frekvenci danou rozdílem nebo součtem budících frekvencí fE a fU a tím se dá dosáhnout vysoké citlivosti. V mém případě byl vždy měřen signál na rozdílové frekvenci fi = fE-fU.
2	Phylogeny and Molecular Evolution of the Voltage-gated Sodium Channel Gene scn4aa in the Electric Fish Genus Gymnotus Xiao, Dawn Dong-yi 19 March 2014 (has links) Analyses of the evolution and function of voltage-gated sodium channel proteins (Navs) have largely been limited to mutations from individual people with diagnosed neuromuscular disease. This project investigates the carboxyl-terminus of the Nav paralog (locus scn4aa 3’) that is preferentially expressed in electric organs of Neotropical weakly-electric fishes (Order Gymnotiformes). As a model system, I used the genus Gymnotus, a diverse clade of fishes that produce species-specific electric organ discharges (EODs). I clarified evolutionary relationships among Gymnotus species using mitochondrial (cytochrome b, and 16S ribosome) and nuclear (rag2, and scn4aa) gene sequences (3739 nucleotide positions from 28 Gymnotus species). I analyzed the molecular evolution of scn4aa 3’, and detected evidence for positive selection at eight amino acid sites in seven Gymnotus lineages. These eight amino acid sites are located in motifs that may be important for modulation of EOD frequencies. phylogeny systematics molecular evolution evolution voltage-gated sodium channel scn4a Nav1.4 sodium channel gene protein fish electric fish knifefish Neotropical fish Gymnotiform Gymnotus electric organ discharge electric field electric organ electric signal cytochrome b 16S ribosome phylogenetic reconstruction phylogenetic tree evolutionary history positive selection patterns of selection neuromuscular disease gene duplication differential expression maximum parsimony parsimony PAUP* Bayesian inference MrBayes Bayesian maximum likelihood PAML 0307
3	Phylogeny and Molecular Evolution of the Voltage-gated Sodium Channel Gene scn4aa in the Electric Fish Genus Gymnotus Xiao, Dawn Dong-yi 19 March 2014 (has links) Analyses of the evolution and function of voltage-gated sodium channel proteins (Navs) have largely been limited to mutations from individual people with diagnosed neuromuscular disease. This project investigates the carboxyl-terminus of the Nav paralog (locus scn4aa 3’) that is preferentially expressed in electric organs of Neotropical weakly-electric fishes (Order Gymnotiformes). As a model system, I used the genus Gymnotus, a diverse clade of fishes that produce species-specific electric organ discharges (EODs). I clarified evolutionary relationships among Gymnotus species using mitochondrial (cytochrome b, and 16S ribosome) and nuclear (rag2, and scn4aa) gene sequences (3739 nucleotide positions from 28 Gymnotus species). I analyzed the molecular evolution of scn4aa 3’, and detected evidence for positive selection at eight amino acid sites in seven Gymnotus lineages. These eight amino acid sites are located in motifs that may be important for modulation of EOD frequencies. phylogeny systematics molecular evolution evolution voltage-gated sodium channel scn4a Nav1.4 sodium channel gene protein fish electric fish knifefish Neotropical fish Gymnotiform Gymnotus electric organ discharge electric field electric organ electric signal cytochrome b 16S ribosome phylogenetic reconstruction phylogenetic tree evolutionary history positive selection patterns of selection neuromuscular disease gene duplication differential expression maximum parsimony parsimony PAUP* Bayesian inference MrBayes Bayesian maximum likelihood PAML 0307

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