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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.
211

Relational Governance Mechanisms and their effect on Contractual Completeness : A case study within a top European company in the Oil & Gas Industry

Ma-Tay, Alfonso, Fascina, Lorenzo January 2011 (has links)
This document investigates the relationship between the usage of relational forms of governance and the completeness of contractual documents. It further examines howthis relationship is presided by the development of social norms between contracting parties. A case study was conducted within Company X, a top European company in the Energy Sector, where interviews to managers and contractual documents were inspected for aqualitative analysis of the aforementioned relationship. The results indicate that the employment of relational governance mechanisms does affect contractual completeness on one of its two dimensions: contingency adaptability. This aspect is enhanced as relational norms are interwoven in the exchange agreement. A clear connection with the second dimension, term specificity, could not be identified, and is instead attributed to contextual idiosyncrasies such as industry type andgovernance structure design. A theoretical model depicting this phenomenon was developed, including mediating effects by situational variables.
212

The Structure and Function Study of Three Metalloenzymes That Utilize Three Histidines as Metal Ligands

Chen, Yan 19 November 2013 (has links)
The function of the metalloenzymes is mainly determined by four structural features: the metal core, the metal binding motif, the second sphere residues in the active site and the electronic statistics. Cysteamine dioxygenase (ADO) and cysteine dioxygenase (CDO) are the only known enzymes that oxidize free thiol containing molecules in mammals by inserting of a dioxygen molecue. Both ADO and CDO are known as non-heme iron dependent enzymes with 3-His metal binding motif. However, the mechanistic understanding of both enzymes is obscure. The understanding of the mechanistic features of the two thiol dioxygenases is approached through spectroscopic and metal substitution in this dissertation. Another focus of the dissertation is the understanding of the function of a second sphere residue His228 in a 3-His-1-carboxyl zinc binding decarboxylase α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD). ACMSD catalyzes the decarboxylation through a hydrolase-like mechanism that is initialized by the deprotonation of metal bounded water molecule. Our study reveled that the second sphere residue His228 is responsible for the water deprotonation through hydrogen bonding. The spectroscopic and crystallographic data showed the H228Y mutation binds ferric iron instead of native zinc metal and the active site water is replaced by the Tyr228 residue ligation. Thus, we concluded that, H228Y not only plays a role of stabilizing and deprotonating the active site water but also is an essential residue on metal selectivity.
213

Discordance of Drug Susceptibility Test Data between the CDC Mycobacteriology Laboratory and Local Public Health Laboratories Participating in Tuberculosis Clinical Trials, TBTC, CDC

Patala, Anne Havilah 07 May 2011 (has links)
BACKGROUND: Multi drug resistant Tuberculosis (MDR-TB) is a serious public health concern in many parts of the world. As per the WHO- 2010 global report on Surveillance and response 3.6% of all incident TB cases globally are multidrug resistant. In this regard, there is an increasing demand for timely, reliable and comprehensive drug susceptibility testing (DST) as MDR-TB surveillance is being geared up. The intent of this analysis is to determine whether there is a need to continue routine confirmatory DST testing at CDC in addition to just sending the isolates for genotyping. Analysis is done by measuring the discordance between the results of laboratory DST at CDC and the local labs drug type, drug testing concentrations, and study sites. METHODS: The data for this analysis was provided by the Tuberculosis Trials Consortium (TBTC), CDC. Data for this analysis was collected over nearly two decades (1993-2011), gathered from 7 clinical trials. Discordance between the local and CDC lab DST results was measured using Kappa statistic. Sensitivity and specificity analysis was done by taking the CDC DST lab results as the gold standard. Discordance levels were calculated by local sites and baseline drug resistance for each antibiotic in each study was measured. RESULTS: Average Kappa values for inter rater agreement for all the studies was 0.6444 whereas the overall level of discordance across all studies is 7.786%. Drug resistance at baseline was highest for Isoniazid and Streptomycin (except Study 23 and 22). CONCLUSION: Though the current results show few DST result discordances between local and CDC labs, it is better to continue to send isolates to the centralized lab (CDC) in view of the worldwide threat of drug resistant TB epidemic, the recommendations of the current literature and the benefits of reliable confirmatory testing services and availability of other molecular diagnostic methods.
214

Some Conclusions of Statistical Analysis of the Spectropscopic Evaluation of Cervical Cancer

Wang, Hailun 03 August 2008 (has links)
To significantly improve the early detection of cervical precancers and cancers, LightTouch™ is under development by SpectRx Inc.. LightTouch™ identifies cancers and precancers quickly by using a spectrometer to analyze light reflected from the cervix. Data from the spectrometer is then used to create an image of the cervix that highlights the location and severity of disease. Our research is conducted to find the appropriate models that can be used to generate map-like image showing disease tissue from normal and further diagnose the cervical cancerous conditions. Through large work of explanatory variable search and reduction, logistic regression and Partial Least Square Regression successfully applied to our modeling process. These models were validated by 60/40 cross validation and 10 folder cross validation. Further examination of model performance, such as AUC, sensitivity and specificity, threshold had been conducted.
215

Testing an Assumption of Non-Differential Misclassification in Case-Control Studies

Hui, Qin 01 August 2011 (has links)
One of the issues regarding the misclassification in case-control studies is whether the misclassification error rates are the same for both cases and controls. Currently, a common practice is to assume that the rates are the same (“non-differential” assumption). However, it is suspicious that this assumption is valid in many case-control studies. Unfortunately, no test is available so far to test the validity of the assumption of non-differential misclassification when the validation data are not available. We propose the first such method to test the validity of non-differential assumption in a case-control study with 2 × 2 contingency table. First, the Exposure Operating Characteristic curve is defined. Next, two non-parametric methods are applied to test the assumption of non-differential misclassification. Three examples from practical applications are used to illustrate the methods and a comparison is made.
216

Virulence factors in fecal Escherichia coli from humans and animals

Hill, Stephen 11 January 2013 (has links)
A DNA microarray capable of detecting 445 virulence factors (VFs) and antibiotic resistance genes was used to assess human and animal fecal E. coli isolates for pathogenic potential and host specificity. The only enteric pathotype detected was atypical EPEC, which was found in 3.7% of all isolates. 17% of human isolates were extraintestinal pathotypes, with the majority of these being uropathogenic. Isolates from humans and chickens were the most likely to have resistance to at least one class of antibiotic. VFs that were found almost exclusively in human isolates, when compared to one other group, included sat (10% of human isolates and no animal isolates), iucD and iut (24% of human, <1% mammal) and iha (16% human, <1% wild avian). Decision trees utilizing multiple probes to identify the source of an E. coli isolate were able to correctly identify the source of 79% of validation isolates in a human vs. animal comparison. / Environment Canada
217

Krepšininkų traumų dažnis, priežastys ir specifika priklausomai nuo amžiaus / Basketball players injury frequency, causes and specificity depended on age

Kalnutytė, Indrė 30 June 2011 (has links)
Sportinė trauma – viena iš pagrindinių priežasčių, dėl kurios sportininkas negali dalyvauti treniruotėse, varžybose. Plintant aktyviam gyvenimo būdui, sportinių pažeidimų problema tampa vis aktualesnė ir kasdieniniam gyvenime (Barkauskas, 1995). Traumas sukeliančių mechanizmų ir veiksnių žinojimas leidžia veiksmingiau atlikti profilaktinį darbą. Dėl to labai svarbu į jį įtraukti tyrėjus, trenerius, gydytojus, kurie pasinėrę į sporto traumatizmo problemas (Ренстрём, 2003). Tyrimo tikslas – nustatyti ir palyginti Lietuvos vaikų, jaunių ir didelio meistriškumo krepšinio komandų traumų pasireiškimo dažnį, priežastis ir specifiką priklausomai nuo amžiaus. Tikslui pasiekti įgyvendinome uždavinius, t.y. nustatėme dažniausiai krepšininkų tarpe pasitaikančių traumų priežastis ir traumų dažnį priklausomai nuo amžiaus. Nustatėme traumų specifiką priklausomai nuo amžiaus. Nustatėme kokios yra taikomos prevencinės priemonės sumažinti traumingumui. Atlikus tyrimą priėjome prie išvadų jog dažniausiai pasitaikančios traumos vaikų 10-14 m. (45 proc.) ir jaunių 14-18 m. (45 proc.) yra rankų pirštų traumos, o aukšto meistriškumo krepšininkų tarpe dažniausiai pasitaikanti yra čiurnos trauma (28 proc.). Vaikų komandos vidutiniškai per sezoną patyrė 13 ± 2, jauniai – 14 ± 2 ir aukšto meistriškumo komandos 4 ± 2 traumos per sezoną. Daugiausia sportinių traumų patiriama karjeros pradžioje, vėliau su lyg sportine patirtimi traumų skaičius mažėja. Didelį stažą turintys sportininkai traumas patiria... [toliau žr. visą tekstą] / Sport injury – is one of the main reasons why athlete can not participate in practise or competitions. Sports infringement problem become more acute in daily life (Barkauskas, 1995). Injury causing mechanisms and factors knowledge allows more effectively carry out preventive work. So therefore it is important to include researchers, coaches, doctors, who are immersed in sports injuries issues (Ренстрём, 2003). Aim of the study – to compare Lithuanian children, youth and professional basketball teams injury frequency, causes and specificity depending on age. In order we achieved implementation, i.e.we find out the mostly among common basketball injuries and injury rate depended on age. We found what preventive measures are used. After the research had been made we concluded that the most commin injury in children 10-14 (45 percent) and Junior 14-18 (45 percent) was fingers injury, and in professional basketball players ankel injuries (28 percent) were he most common injury. Children‘s team had a season averge of injuries - 13±2, youth - 14±2 and professional teams - 4±2 innjury during the season. The main causes of children injuries was the lack of warm up (82 percent), youth – body contact (92 percent) and poor condition (91 percent) and for the professional basketball teams body contact (46 percent) was the main causes of injuries. Among children, youth and professional basketball players , during training proces, coaches and physiotherapists focuses on warming up and... [to full text]
218

Risk analysis and potential implications of exotic Gyrodactylus species on cultured and wild cyprinids in the Western Cape, South Africa

Maseng, Monique Rochelle January 2010 (has links)
<p>Koi and goldfish have been released into rivers in South Africa since the 1800&rsquo / s for food and sport fish and have since spread extensively. These fish are present in most of the river systems in South Africa and pose an additional threat the indigenous cyprinids in the Western Cape. Monogenean parasites of the genus Gyrodactylus are of particular concern, as their unique biology renders them a possible threat. Gyrodactylus kherulensis and G. kobayashii were identified from koi and goldfish respectively imported from Asia, Europe and locally bred fish. Morphometrics and the use of statistical classifiers, which includes univariate (ANOVA and Kruskal-Wallis), bivariate (Pearson&rsquo / s correlation) and multivariate (Principal Component Analysis) placed the two species within their respective groups. There was some intraspecific variation among the different populations collected from the various locations, especially in the hamulus and ventral bar features, but the marginal hooklets, however, remained static for both helminth species.</p>
219

A directed evolution design of target specificity and kinetic analysis of conformational transitions in the HhaI methyltransferase / DNR metiltransferazės HhaI atpažįstamos sekos inžinerija ir konformacinių virsmų kinetikos tyrimas

Gerasimaitė, Rūta 19 May 2011 (has links)
DNA cytosine-5 methyltransferases (MTases) recognize short DNA sequences and catalyze the transfer of the methyl group from the cofactor AdoMet to the C5-position of a target cytosine. In this work both these aspects of the MTase mechanism have been addressed. First, using rational protein design and directed evolution approaches the specificity of the HhaI MTase, GCGC, has been changed to GCG by functional elimination of one of the two target recognition elements. In addition, the introduced structural changes endowed the MTase with the ability to transfer extended groups from synthetic cofactor analogs, providing the first example of a dual specificity change in a DNA MTase. Second, the kinetics of fast pre-catalytic conformational transitions in the MTase and DNA has been investigated. A new method to follow the target cytosine flipping and its subsequent covalent activation has been proposed, which allows a direct real-time observation of these processes by monitoring associated UV absorbance changes in a chemically unperturbed DNA. These studies for the first time demonstrate that the flipping of the target cytosine and the closure of the catalytic loop in the enzyme occur simultaneously, whereas the covalent activation of the target cytosine and the transfer of the methyl group are temporally distinct steps in the catalytic cycle of M.HhaI. Since the new method is based on the general phenomenon of hyperchromicity, it is thus applicable for studies of other systems... [to full text] / DNR citozino-5 metiltransferazės (MTazės) atpažįsta specifines DNR sekas ir katalizuoja metilgrupės pernešimą nuo kofaktoriaus AdoMet ant taikinyje esančio citozino. Šiame darbe nagrinėjami abu MTazių veikimo mechanizmo aspektai. Baltymų inžinerijos ir kryptingos evoliucijos metodais pašalinant vienos iš dviejų taikinio atpažinimo kilpų funkciją, MTazės HhaI atpažįstamas taikinys GCGC pakeistas į GCG. Dėl įvestų struktūros pakeitimų nauja unikalaus specifiškumo MTazė efektyviai katalizuoja ne tik metilo, bet ir didesnių grupių pernešimą nuo sintetinių kofaktoriaus analogų, ir gali tapti naudingu molekulinės biologijos įrankiu. Katalitinės reakcijos metu MTazės kilpa užsidaro, apglėbdama surištą DNR, o taikinio citozinas išsukamas iš DNR spiralės ir aktyvuojamas, kovalentiškai prisijungiant katalitiniam cisteinui. Šiems greitiems prieškatalitiniams procesams tirti buvo panaudotas naujas metodas, leidžiantis realiu laiku stebėti M.HhaI sąlygotą citozino išsukimą bei kovalentinę aktyvaciją, registruojant mažus UV absorbcijos pokyčius gamtinį substratą atitinkančioje DNR. Pirmą kartą parodyta, kad M.HhaI katalizuojamoje reakcijoje citozino išsukimas ir katalitinės kilpos užsidarymas vyksta sinchroniškai, o kovalentinė citozino aktyvacija ir metilgrupės pernešimas yra kinetiškai netapačios katalitinio ciklo stadijos. Kadangi naujasis metodas remiasi fundamentine nukleorūgščių savybe – hiperchrominiu efektu, todėl jis gali būti naudojamas ir kitų DNR bazę išsukančių baltymų... [toliau žr. visą tekstą]
220

DNR metiltransferazės HhaI atpažįstamos sekos inžinerija ir konformacinių virsmų kinetikos tyrimas / A directed evolution design of target specificity and kinetic analysis of conformational transitions in the HhaI methyltransferase

Gerasimaitė, Rūta 19 May 2011 (has links)
DNR citozino-5 metiltransferazės (MTazės) atpažįsta specifines DNR sekas ir katalizuoja metilgrupės pernešimą nuo kofaktoriaus AdoMet ant taikinyje esančio citozino. Šiame darbe nagrinėjami abu MTazių veikimo mechanizmo aspektai. Baltymų inžinerijos ir kryptingos evoliucijos metodais pašalinant vienos iš dviejų taikinio atpažinimo kilpų funkciją, MTazės HhaI atpažįstamas taikinys GCGC pakeistas į GCG. Dėl įvestų struktūros pakeitimų nauja unikalaus specifiškumo MTazė efektyviai katalizuoja ne tik metilo, bet ir didesnių grupių pernešimą nuo sintetinių kofaktoriaus analogų, ir gali tapti naudingu molekulinės biologijos įrankiu. Katalitinės reakcijos metu MTazės kilpa užsidaro, apglėbdama surištą DNR, o taikinio citozinas išsukamas iš DNR spiralės ir aktyvuojamas, kovalentiškai prisijungiant katalitiniam cisteinui. Šiems greitiems prieškatalitiniams procesams tirti buvo panaudotas naujas metodas, leidžiantis realiu laiku stebėti M.HhaI sąlygotą citozino išsukimą bei kovalentinę aktyvaciją, registruojant mažus UV absorbcijos pokyčius gamtinį substratą atitinkančioje DNR. Pirmą kartą parodyta, kad M.HhaI katalizuojamoje reakcijoje citozino išsukimas ir katalitinės kilpos užsidarymas vyksta sinchroniškai, o kovalentinė citozino aktyvacija ir metilgrupės pernešimas yra kinetiškai netapačios katalitinio ciklo stadijos. Kadangi naujasis metodas remiasi fundamentine nukleorūgščių savybe – hiperchrominiu efektu, todėl jis gali būti naudojamas ir kitų DNR bazę išsukančių baltymų... [toliau žr. visą tekstą] / DNA cytosine-5 methyltransferases (MTases) recognize short DNA sequences and catalyze the transfer of the methyl group from the cofactor AdoMet to the C5-position of a target cytosine. In this work both these aspects of the MTase mechanism have been addressed. First, using rational protein design and directed evolution approaches the specificity of the HhaI MTase, GCGC, has been changed to GCG by functional elimination of one of the two target recognition elements. In addition, the introduced structural changes endowed the MTase with the ability to transfer extended groups from synthetic cofactor analogs, providing the first example of a dual specificity change in a DNA MTase. Second, the kinetics of fast pre-catalytic conformational transitions in the MTase and DNA has been investigated. A new method to follow the target cytosine flipping and its subsequent covalent activation has been proposed, which allows a direct real-time observation of these processes by monitoring associated UV absorbance changes in a chemically unperturbed DNA. These studies for the first time demonstrate that the flipping of the target cytosine and the closure of the catalytic loop in the enzyme occur simultaneously, whereas the covalent activation of the target cytosine and the transfer of the methyl group are temporally distinct steps in the catalytic cycle of M.HhaI. Since the new method is based on the general phenomenon of hyperchromicity, it is thus applicable for studies of other systems... [to full text]

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