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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.
31

Population structure of insect pathogenic bacteria in UK soil and their associated nematodes

Al-Own, Fada'a January 2013 (has links)
Surveys for entomopathogenic bacteria and their associated nematode hosts were conducted locally (University of Bath campus) and across southern England. Sampling involved trialing a novel Android app. (Epicollect) to manage sample collection data. Galleria larvae were used to bait UK soil samples. Insects which became infected were placed on White traps to collect any emerging nematodes, from which bacteria were isolated. Bacteria were also isolated from the haemolymph of any infected larvae. Bacterial isolates were classified on the basis of 16s rDNA and recA gene sequences. Serratia proteamaculans-like strains dominated the samples, and Multilocus sequence analysis (MLSA) was developed for the characterization of these Serratia isolates. We determined the sequences of (350-450-bp) fragments from five housekeeping genes of 84 isolates of Serratia proteamaculans. MLSA was shown to be effective for distinguishing closely related strains found in the insects’ haemolymph and from different nematodes. goeBURST was used to visualize the relationships between the STs, and the data showed a high level of discrimination, resolving 69 STs from the 84 isolates. In addition, the data derived from this study were represented in a phylogenetic network using the Splits Tree-network methods, to show the rate of recombination within and between the genes. From a total of 256 infected Galleria 23.04% were nematode positive. The nematodes were identified based on 18S rDNA 19 isolates were close relatives of the species Pristionchus entomophaga and Diplogasteriodes magnus (Diplogastridae). A further 16 isolates were more closely related to Steinernema glaseri (Steinernematidae). All three nematode types were isolated from diverse habitats and soil types, but were isolated more frequently in cold seasonal conditions. The bacterial sequence data suggest that the nematode- associated strains of bacteria belong to specific clades, distinct from the free living infective strains, which hints at ecological diversity within the S. proteamaculans population. Two of the Serratia proteamaculans-like strains had been chromosomally labeled with GFP to confirm the specifics of their association with the nematode hosts. The associated S. proteamaculans-like isolates isolated from Bath and Chepstow soils were examined further for their pathogenicity to Galleria mellonella and Manduca sexta larvae. Serratia Bath isolates, isolated from Pristionchus were more virulent toward both insect hosts than the Serratia from the Chepstow isolates associated with Steinernema nematodes. This suggests that host specificity may play important role in the virulence of the strain.
32

The Evolution, Applications, and Statistical Interpretations of DNA Typing in Forensic Science

Schober, Cassandra C. (Cassandra Carolyn) 08 1900 (has links)
This thesis examines the evolution, applications, and statistical interpretations of DNA typing as a tool in the field of forensic science as well as in our criminal justice system. The most controversial aspect of DNA typing involves the determination of how likely it is that two people share the same DNA profile. This involves the use of population genetics and databases of allelic frequencies as well as some assumptions about population structuring.
33

Effects of Method and Context of Note-taking on Memory: Handwriting versus Typing in Lecture and Textbook-Reading Contexts

Schoen, Ian 20 May 2012 (has links)
Both electronic note-taking (typing) and traditional note-taking (handwriting) are being utilized by college students to retain information. The effects of the method of note-taking and note-taking context were examined to determine if handwriting or typing notes and whether a lecture context or a textbook-reading context influenced retention. Pitzer College and Scripps College students were assigned to either handwrite or type notes on a piece of academic material presented in either a lecture or textbook context and were given a test to assess their retention. The results demonstrated that there was a significant main effect for typing notes such that typing notes produced higher retention scores than handwriting notes. The results also indicated that there was an interaction between method of note-taking and context such that the lowest scores were achieved in the condition in which participants handwrote notes during a lecture. In total, these findings suggest that typing as a method of note-taking may by an influential factor in memory retention, particularly in a lecture context.
34

Design of Thumb Keyboards: Performance, Effort and Kinematics

Hogg, Nicholas Alexander 19 May 2010 (has links)
Mobile hand-held communication device (smart phone) use is very prevalent and growing rapidly. In addition, there is empirical support for heavy use to be associated with musculoskeletal disorders. This study therefore addressed the physical demand and performance when using these devices. The natural texting style for 20 participants was identified and then participants performed standardized static and dynamic tasks on 4 different types of mobile hand-held devices; a touch screen device and 3 devices with different keyboard sizes and layout; a flip or clamshell design, a PDA style device and a phone with a pull out QWERTY keyboard. Participants rated the effort required to complete each task and for dynamic tasks, keystroke speed was also measured. The time history of angles of the carpometacarpal, metacarpophalangeal and interphalageal joints of the thumb as well as motion of the wrist were determined using small surface makers and an optoelectronic motion capture system. Thumb kinematics were normalized to the maximum range of motion of each joint. Statistically significant and substantial differences were found for the dynamic condition: The tasks which required the most motion in the flexion/extension axis of the thumb also required the most effort, and that there is an inverse relationship between effort and typing speed, namely that those tasks, or devices which required the highest effort resulted in the lowest typing speeds, and visa-versa. Similarly, results showed that those static tasks which required the most thumb flexion also required the most effort. Overall, use of the touch screen phone required the least effort for dynamic and static tasks, and also resulted in the highest typing speeds. This could be a result of having the lowest force required to engage the keys. The device which resulted in the lowest typing speed and highest required effort was the flip phone, which also had the highest required force to engage the keys. There was also a weak relationship between user thumb length and required effort, with longer thumb length necessitating a greater about of effort. Those subjects who used the texting style indentified as the slide style which used forearm rotation with a less flexed thumb reported significantly less effort for all tasks than those who used the claw style which used extreme flexion of the thumb joints. However, texting style had no significant effect on typing speed, indicating that someone could adopt the slide style to reduce muscular effort and potentially the risk of developing musculoskeletal disorders in the upper limbs and neck without sacrificing performance.
35

Bacteriophage and antibiogram characterization of Staphylococcus aureus strains from hospital patients.

Tse, Suk-yee, Doris, January 1900 (has links)
Thesis--M. Phil., University of Hong Kong. / Typewritten.
36

Pandemic Vibrio parahaemolyticus : defining strains using molecular typing and a growth advantage at lower temperatures /

Davis, Carisa Renee. January 2008 (has links)
Dissertation (Ph.D.)--University of South Florida, 2008. / Includes vita. Includes bibliographical references. Also available online.
37

Rock classification from conventional well logs in hydrocarbon-bearing shale

Popielski, Andrew Christopher 20 February 2012 (has links)
This thesis introduces a rock typing method for application in shale gas reservoirs using conventional well logs and core data. Shale gas reservoirs are known to be highly heterogeneous and often require new or modified petrophysical techniques for accurate reservoir evaluation. In the past, petrophysical description of shale gas reservoirs with well logs has been focused to quantifying rock composition and organic-matter concentration. These solutions often require many assumptions and ad-hoc correlations where the interpretation becomes a core matching exercise. Scale effects on measurements are typically neglected in core matching. Rock typing in shale gas provides an alternative description by segmenting the reservoir into petrophysically-similar groups with k-means cluster analysis which can then be used for ranking and detailed analysis of depth zones favorable for production. A synthetic example illustrates the rock typing method for an idealized sequence of beds penetrated by a vertical well. Results and analysis from the synthetic example show that rock types from inverted log properties correctly identify the most organic-rich model types better than rock types detected from well logs in thin beds. Also, estimated kerogen concentration is shown to be most reliable in an under-determined problem. Field cases in the Barnett and Haynesville shale gas plays show the importance of core data for supplementing well logs and identifying correlations for desirable reservoir properties (kerogen/TOC concentration, gas saturation, and porosity). Qualitative rock classes are formed and verified using inverted estimates of kerogen concentration as a rock-quality metric. Inverted log properties identify 40% more of a high-kerogen rock type over well-log based rock types in the Barnett formation. A case in the Haynesville formation suggests the possibility of identifying depositional environments as a result of rock attributes that produce distinct groupings from k-means cluster analysis with well logs. Core data and inversion results indicate homogeneity in the Haynesville formation case. However, the distributions of rock types show a 50% occurrence between two rock types over 90 ft vertical-extent of reservoir. Rock types suggest vertical distributions that exhibit similar rock attributes with characteristic properties (porosity, organic concentration and maturity, and gas saturation). This method does not directly quantify reservoir parameters and would not serve the purpose of quantifying gas-in-place. Rock typing in shale gas with conventional well logs forms qualitative rock classes which can be used to calculate net-to-gross, validate conventional interpretation methods, perform well-to-well correlations, and establish facies distributions for integrated reservoir modeling in hydrocarbon-bearing shale. / text
38

GENETIC ANALYSIS OF CLOSTRIDIUM PERFRINGENS: INSIGHT INTO EVOLUTION OF VIRULENCE

Sawires, Youhanna Sobhy January 2005 (has links)
Clostridium perfringens is an important pathogen in veterinary and medical fields. Understanding epidemiology of C. perfringens diseases and evolution of virulence within C. perfringens necessitates an efficient, time and cost effective strain typing method. Multiple-locus variable-number tandem repeat analysis (MLVA) has been applied to typing of other pathogens and we describe here the development of a MLVA scheme for C. perfringens. We characterized five VNTR loci, and screened 112 C. perfringens isolates to evaluate typability, reproducibility, and discriminatory power of the scheme. All isolates were assigned a MLVA genotype and the technique has excellent reproducibility, with a numerical index of discrimination of 0.995. Thus, MLVA is an efficient tool for C. perfringens strain typing, and being PCR based makes it rapid, easy, and cost effective. In addition, it can be employed in epidemiological, ecological, and evolutionary investigations of the organism.Virulence of this species is not fully understood and it does seem that distribution of the toxin/enzyme genes is erratic within the population. We used the MLVA scheme to investigate evolution of virulence and population structure of this species. Analysis of the phylogenetic signal indicates that acquisition of the major toxin genes and other plasmid-borne toxin genes is a recent evolutionary event, and their maintenance is essentially a function of the selective advantage they confer to strains carrying them in certain micro-niches under different conditions. In addition, it indicates the ability of virulent strains to cause disease in different hosts. More interestingly, there is evidence that certain normal flora strains are virulent when they gain access to a different host species. Analysis of the population structure indicates that recombination events are the major tool that shapes the population and this panmixia is interrupted with frequent clonal expansion that mostly corresponds to disease processes. Signature of positive selection was detected in the alpha toxin gene, suggesting the possibility of adaptive alleles on the other chromosomally-encoded determinants. Finally, C. perfringens proved to have a dynamic population, and availability of more genome sequences, use of comparative proteomics and of animal models would provide more insight into the pathogenicity of this organism.
39

The syntax and semantics of clause-typing in Plains Cree

Cook, Clare Elizabeth 11 1900 (has links)
This thesis proposes that there are two kinds of clauses: indexical clauses, which are evaluated with respect to the speech situation; and anaphoric clauses, which are evaluated with respect to a contextually-given (anaphoric) situation. Empirical motivation for this claim comes from the clause-typing system of Plains Cree, an Algonquian language spoken on the Canadian plains, which morpho-syntactically distinguishes between two types of clauses traditionally called INDEPENDENT and CONJUNCT orders. In the current analysis, the INDEPENDENT order instantiates indexical clauses, and the CONJUNCT order instantiates anaphoric clauses. After laying out the proposal (chapter 1) and establishing the morphosyntax of Plains Cree CPs (chapter 2), the remaining chapters discuss the proposal in detail. Chapter 3 focusses on the syntax and semantics of indexical clauses (Plains Cree’s INDEPENDENT order). Syntactically, I show that there is an anti-c-command and an anti-precedence condition on indexical clauses. Semantically, I show that indexical clauses are always and only evaluated with respect to the speech situation, including the speech time (temporal anchoring), speech place (spatial anchoring), and speaker (referential anchoring). Chapter 4 focusses on the syntax and semantics of anaphoric clauses (Plains Cree’s CONJUNCT order). Syntactically, I show that anaphoric clauses must always be either preceded or dominated by some other antecedent clause. Semantically, I show that the value of temporal/spatial/referential dependent elements within an anaphoric clause is determined by an antecedent. Chapter 5 turns to the syntactic subclassification of Plains Cree’s CONJUNCT (i.e., anaphoric) clauses. I propose that there are three classes: chained clauses, adjunct clauses, and mediated argument clauses. I provide two kinds of diagnostics that distinguish these classes, and explore the consequences of this classification for argument clauses and complementation. Finally, Chapter 6 proposes a semantic subclassification of Plains Cree’s CONJUNCT (i.e., anaphoric) clauses. I propose that there is a direct mapping between the morphology and the semantics: one complementizer encodes presupposition of the proposition, the lack of a complementizer encodes a-veridicality of the proposition, and one complementizer is semantically unspecified (the elsewhere case). This means that Plains Cree’s clause-typing is fundamentally concerned with how the truth of the proposition is represented.
40

Design of Thumb Keyboards: Performance, Effort and Kinematics

Hogg, Nicholas Alexander 19 May 2010 (has links)
Mobile hand-held communication device (smart phone) use is very prevalent and growing rapidly. In addition, there is empirical support for heavy use to be associated with musculoskeletal disorders. This study therefore addressed the physical demand and performance when using these devices. The natural texting style for 20 participants was identified and then participants performed standardized static and dynamic tasks on 4 different types of mobile hand-held devices; a touch screen device and 3 devices with different keyboard sizes and layout; a flip or clamshell design, a PDA style device and a phone with a pull out QWERTY keyboard. Participants rated the effort required to complete each task and for dynamic tasks, keystroke speed was also measured. The time history of angles of the carpometacarpal, metacarpophalangeal and interphalageal joints of the thumb as well as motion of the wrist were determined using small surface makers and an optoelectronic motion capture system. Thumb kinematics were normalized to the maximum range of motion of each joint. Statistically significant and substantial differences were found for the dynamic condition: The tasks which required the most motion in the flexion/extension axis of the thumb also required the most effort, and that there is an inverse relationship between effort and typing speed, namely that those tasks, or devices which required the highest effort resulted in the lowest typing speeds, and visa-versa. Similarly, results showed that those static tasks which required the most thumb flexion also required the most effort. Overall, use of the touch screen phone required the least effort for dynamic and static tasks, and also resulted in the highest typing speeds. This could be a result of having the lowest force required to engage the keys. The device which resulted in the lowest typing speed and highest required effort was the flip phone, which also had the highest required force to engage the keys. There was also a weak relationship between user thumb length and required effort, with longer thumb length necessitating a greater about of effort. Those subjects who used the texting style indentified as the slide style which used forearm rotation with a less flexed thumb reported significantly less effort for all tasks than those who used the claw style which used extreme flexion of the thumb joints. However, texting style had no significant effect on typing speed, indicating that someone could adopt the slide style to reduce muscular effort and potentially the risk of developing musculoskeletal disorders in the upper limbs and neck without sacrificing performance.

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