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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

Factors Impacting the Urban Transmission Potential of Mosquito-borne Arboviruses in New Orleans, Louisiana

January 2017 (has links)
acase@tulane.edu / Urban epidemics of mosquito-borne diseases are driven by a close association between mosquito vectors and artificial container habitats near residences. In New Orleans, Louisiana abundant populations of the mosquito species Aedes (Stegomyia) aegypti (Linnaeus) and Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae), are potentially capable of supporting local transmission of viruses such as dengue, chikungunya and Zika introduced by infected individuals. Container-inhabiting Aedes mosquito populations are focally abundant, and unevenly distributed across the urban landscape. Accurate estimations of mosquito abundance are important in determining transmission potential and for focusing disease surveillance and control measures. Mosquito collection methods target specific life stages and each has inherit biases. This study characterized common and productive container habitats in residential neighborhoods, evaluated field techniques for measuring vector mosquito abundance, and evaluated mosquitoes for host bloodmeal sources. Knowledge, attitude and practice surveys were conducted in three urban neighborhoods to identify behavioral and residential predictors of potential Aedes aegypti and Ae. albopictus container habitats. Container habitats were systematically evaluated for immature mosquito abundance. Habitat abundance was compared between neighborhoods and for associations with recent precipitation. In a separate study, collections of adult mosquito were compared using various standard adult mosquito collection traps. Finally, molecular identification techniques were used to determine adult mosquito bloodmeal sources, to human feeding rates during two time periods. These studies will allow public health authorities to develop a comprehensive understanding of the local transmission risk of recently-emerging arboviruses such as Zika, a broad knowledge base of species behavior and can be used to produce tailored educational campaign targeting in advance of future epidemics. / 1 / Sarah R. Michaels
2

HYDROLOGY AND ORGANIC CARBON EXPORT OF AN IRREGULARLY FLOODED BRACKISH MARSH ON THE UPPER TEXAS COAST

BOREY, ROLAND BORN January 1979 (has links)
No description available.
3

ISOTOPIC ANOMALIES FROM NUCLEAR PROCESSES IN STARS

DZICZKANIEC, MARLENE January 1980 (has links)
Specific nucleosynthetic environments are examined as the sources for the anomalous xenon observed in meteorite samples. A simplified nuclear network is used to allow rapid estimation of isotopic abundances over a wide range of stellar conditions. In the zone of oxygen burning outside a stellar core that is in the silicon burning phase of energy generation, photodisintegration of xenon seed isotopes is shown to be a potential source of an overabundance of the p-isotopes of xenon. The result ('124)Xe/('126)Xe > 1 can be obtained if theoretical calculations systematically overestimate photo-alpha emission rates of certain p-isotopes of elements in the xenon region of the chart of the nuclides. Anomalies in the abundances of the heaviest xenon isotopes are shown to be a possible consequence of neutron capture reactions during explosive carbon burning in a supernova. Overabundances of ('136)Xe relative to ('134)Xe are the result of the low neutron-capture rates of N = 82 nuclei and the high photo-neurtron emission rates of N= 38 nuclei. Isotopic abundance signatures in the elements krypton, tellurium and osmium that are correlated with anomalous xenon are shown to be a plausible result of nuclear processing in the same environments that may produce anomalous xenon. The relative abundance of ('129)I associated with anomalous xenon is also examined, and predictions for anomalies in other elements based on the models presented here are given.
4

TWO MODELS FOR ISOTOPIC VARIATIONS IN THE LUNAR REGOLITH

RAY, JAMES R. January 1980 (has links)
Two independent models are presented which attempt to account for large, apparently secular, isotopic variations recorded in lunar samples. To explain the observed long-term increase of ('15)N/('14)N, the first model considers the consequences of a "spike" contamination of the sun's outer convective zone with material greatly enhanced in ('14)N. We argue that this situation may have arisen through the following scenario: (i) The sun formed in a star cluster which included a nearby (TURN)3M(,(CIRCLE)) member. (ii) After about 10('8)y, the companion star ejected a planetary nebula enriched in ('14)N, ('22)Ne and ('4)He due to prior nuclear processing. (iii) Upon encoutnter with the solar system, the planetary nebula material was accreted onto the sun's surface and possibly into planetary/meteroitic source matter. The predominant effect was a sizeable decrease of ('15)N/('14)N in the solar convective zone and hence in the solar wind. (iv) Subsequent mixing processes in the convective zone have slowly acted to restore the sun's original surface composition. That variation, in turn, has been recorded by solar wind N trapped in lunar soils and breccias. The second model takes note of observational evidence from the Apollo 16 site which indicates that even though TiO(,2)-rich samples from other sites show a long-term increase of ('3)He/('4)He, TiO(,2)-poor samples do not. Consequently, we regard models which envision He isotopic variations as occurring in the solar wind reservoir to be untenable. Instead, the explanation must entail the differing retentivities of high and low TiO(,2) materials for inert gases. We propose that lunar atmospheric He is ultimately responsible for secular isotopic variations in He and deduce the requirements on past solar wind flow conditions. In order for atmospheric He to have been an important source of trapped lunar gas (by ionization and subsequent acceleration a la Manka and Michel, 1970), the ancient solar wind flux must have been about 100 times greater than now. Assuming the bubble diffusion model of Tamhane and Agrawal (1979) to accurately describe gas loss from lunar soil particles, we show that the different He isotopic records of TiO(,2)-rich and -poor samples can be explained if ancient atmospheric He ions were implanted with larger energies than contemporary solar wind ions. This is equivalent to requiring that the ancient interplanetary magnetic field was larger than today by a factor greater than 4.4. Associated secular increases of ('15)N('/14)N and ('13)C/('12)C are expected but the magnitudes depend critically upon the fractions of these elements which evolve into the lunar atmosphere in the atomic form.(' )
5

THREE-DIMENSIONAL ASPECTS OF THE PLASTIC DEFORMATION OF ANISOTROPIC ROCKS

HO, CHENG-YO January 1981 (has links)
The method of plastic upper bound analysis is developed to solve problems involving three-dimensional loading and deformation of anisotropic materials. Experiments are conducted to evaluate the applicability of the analytical results. This method is also used to predict the effect of material strength properties on the lateral deviation force on a wedge during indentation of anisotropic plastic materials. The results show that the method does provide a fairly good upper bound for the indentation force and it also gives a reasonable explanation of the experimentally observed lateral deviation force.
6

INERT GASES IN FIFTEEN IRON METEORITES

PALMA, RUSSELL LUMIR January 1981 (has links)
The inert gases helium, neon, argon, krypton, and xenon were measured mass-spectrometrically in the metal phases of fifteen iron meteorites and in graphite and troilite mineral separates from the Odessa iron meteorite. The meteorites analyzed were chosen because of their low cosmic ray exposure ages; most had known exposure ages of less than 200 million years. The hope was that the prominent spallation component seen in prior iron meteorite inert gas measurements would be reduced enough to allow detection of a trapped gas component, should one exist. Approximately three gram samples were fused in a thoroughly out-gassed alumina crucible. Surface contamination was removed from the samples by acid treatment and by preheating the samples for two days at 300(DEGREES)C. Blank measurements were made for correction purposes before and after each sample. All of the meteorite samples show evidence of having a cosmogenic inert gas component. Small variations attributable to different trace element abundances and cosmic ray shielding are seen. Large deviations from the predicted cosmogenic compositions correlate with short cosmic ray exposure ages and often indicate the presence of a trapped atmospheric-like inert gas component. Those samples showing anomalous behavior in one inert gas tend to show anomalous behavior for all the inert gases. The inert gas data from most samples are consistent with the helium, neon, and argon concentrations being largely of cosmogenic origin and the krypton and xenon resulting from a mix of solar wind, atmospheric, and cosmogenic compositions. However, there are several meteorites which are anomalous with respect to the above interpretation. Krypton and xenon measurements had only been made in the metal phase of five iron meteorites, so determining the composition of those two gases was an important result of this work. The light krypton isotopes ('78)Kr and ('80)Kr are enriched in many samples relative to a mixture of atmospheric-solar wind and cosmogenic krypton. Prior investigations of xenon in iron meteorites had assumed only the presence of cosmogenic and atmospheric xenon, but the data from this study suggest that many xenon components may be trapped in the metal phase. The Braunau inert gas data indicate strongly that this meteorite contains primordial trapped gas. Furthermore, the Braunau xenon composition includes the admixture of a xenon component not hitherto seen in any meteorite, stony or iron. This new component is marked by a low ('128)Xe/('132)Xe ratio. The inert gases in the mineral separates from the Odessa iron meteorite also show contributions from spallation, but have distinctive components not seen in the metal phase. There are enrichments at ('80)Kr, ('82)Kr, and ('83)Kr in the troilite phase which are consistent with neutron capture on ('79)Br, ('81)Br, and ('82)Se, respectively, while a ('129)Xe excess results from ('129)I decay. A trapped gas component is strikingly evident in the neon and argon data from the graphite phase of Odessa.
7

International Motor Vehicle Program: Environmental Practice Survey Results

Maxwell, James, Oye, Kenneth, Rothenberg, Sandra, Briscoe, Forrest, Kioke, Ami 18 July 2002 (has links)
No description available.
8

Influence of management practices on weed communities in organic cereal production systems in Saskatchewan

Buhler, Rachel Susanne 03 January 2006
Management practices on organic farms in Saskatchewan are largely unstudied, as are their effect on weed populations and soil quality. The objective of this study was to document what management practices are used on organic farms, classify those practices into management systems and determine if those management systems affect weed populations and soil properties. During the 2002 growing season 73 organic fields in the province of Saskatchewan were surveyed. Three components comprised the data set for each field: a management questionnaire, weed counts, and soil samples that were collected and analyzed for various soil properties. Classification of the management practices identified farming systems: the diverse cropping system, the diverse cropping system using green manure, the low diversity cropping system using summerfallow, and the moderately diverse cropping system using perennials in rotation. Ordination of weed data and the four systems was done with redundancy analysis. It determined that the farm management systems only accounted for 5% of the variation in the weed populations. The only system that affected the weed populations was the moderately diverse cropping system using perennials in rotation. Soil properties were compared among the different management systems. Soil properties were not different between the diverse cropping system using green manure, and the low diversity cropping system using summerfallow. The system that included perennials in rotation had significantly lower pH, electrical conductivity, soil organic matter, phosphorous and potassium levels. The nutrient levels in all systems were low, underscoring the importance of nutrient additions to export farming systems.
9

Influence of management practices on weed communities in organic cereal production systems in Saskatchewan

Buhler, Rachel Susanne 03 January 2006 (has links)
Management practices on organic farms in Saskatchewan are largely unstudied, as are their effect on weed populations and soil quality. The objective of this study was to document what management practices are used on organic farms, classify those practices into management systems and determine if those management systems affect weed populations and soil properties. During the 2002 growing season 73 organic fields in the province of Saskatchewan were surveyed. Three components comprised the data set for each field: a management questionnaire, weed counts, and soil samples that were collected and analyzed for various soil properties. Classification of the management practices identified farming systems: the diverse cropping system, the diverse cropping system using green manure, the low diversity cropping system using summerfallow, and the moderately diverse cropping system using perennials in rotation. Ordination of weed data and the four systems was done with redundancy analysis. It determined that the farm management systems only accounted for 5% of the variation in the weed populations. The only system that affected the weed populations was the moderately diverse cropping system using perennials in rotation. Soil properties were compared among the different management systems. Soil properties were not different between the diverse cropping system using green manure, and the low diversity cropping system using summerfallow. The system that included perennials in rotation had significantly lower pH, electrical conductivity, soil organic matter, phosphorous and potassium levels. The nutrient levels in all systems were low, underscoring the importance of nutrient additions to export farming systems.
10

GENETIC NONINVASIVE CAPTURE-RECAPTURE TECHNIQUES TO MANAGE POLAR BEARS: A PILOT STUDY

Harris, Christopher Matthew 24 December 2010 (has links)
Global polar bear (Ursus maritimus) population numbers are expected to decline steadily over the next 50 years. A noninvasive genetic survey of polar bear numbers may be a useful addition to traditional aerial capture mark recapture (CMR) surveys undertaken throughout the Canadian polar bear population. We attempted a pilot study of noninvasive genetic survey techniques in M’Clintock Channel between May-June 2006-2009. Throughout the survey, we compared our values to the most recent (CMR) survey, conducted by Taylor et al. (2006) between March-June 1998-2000 where 133 cubs, sub-adults and adults were tagged. A total population size of 300 bears was estimated from this aerial CMR survey (Taylor et al. 2006). We found noninvasive sampling stations are sufficient for the capture of a large amount of data on individual bears in an area. Across 4 years, we collected a total of 300 hair samples, and found between 59 and 82 individual bears entered our sampling stations, depending on the stringency of our identification parameters. We estimated genotyping error from duplicated samples, and found this was low (range: 0%-6%), but large enough to not be ignored. There appeared to be a discrepancy between the capture ratio of male adult bears; the CMR survey (1998-2000) captured 25% male bears, while we estimated approximately 64% of our captured bears were male. We felt the most likely explanation of this result is that our traps have a sex bias. However, further research is required to confirm this hypothesis. On the whole, our methods are very important for the management of polar bears, but more research must be done before it can be fully implemented. / Thesis (Master, Biology) -- Queen's University, 2010-12-23 15:35:50.16

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