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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.
1261

Physical, chemical and biological factors affecting the survival of fingernail clams in pool 8, upper Mississippi River

DePoy, Richard Mark January 1996 (has links)
1 examined the temporal and spatial distribution of total ammonia nitrogen (TAN) and un-ionized ammonia (NH,) in sediment pore water and compared the temporal and spatial patterns of TAN and NH, in overlying surface water with those in pore water, to determine if they were reaching concentrations known to be deleterious to fingernail clams. Pore water was obtained by core extraction and subsequent centrifugation. TAN and NI-I3 in pore water were measured from May through December 1994, at ninety two sites in pool 8, upper Mississippi River, to a depth of five centimeters below the sediment-water interface. TAN and NH3 in pore water were significantly different among sampling dates; with the greatest concentrations occurring in the summer months. Tan and N1-I3 in pore water was significantly greater in impounded open water and backwater side channel habitats and least in main channel border habitat. Tan and NH3 in surface water were significantly less than those in pore water from all of the habitats studied. Analysis of sediment substrate physical features, found that fingernail clam density and occupance were correlated to texture, with fingernail clams preferring silt loam and loam textures. Analysis of the data determined fingernail clams have a preference for particular water depths. It was found that a positive correlation exists between the occurrence and abundance of may flies and fingernail clams. Additionally, this study found a positive correlation between the density of dead fingernail clams (as per empty shells) and the abundance of live fingernail clams. Sites that contained a mean NI-I, concentration below 36 ug/L possessed the largest numbers of fingernail clams. When the mean un-ionized ammonia was above 36 ug/l, fingernail clam density declined precipitously-- 36 ug/L NH3 is the concentration demonstrated to inhibit growth of fingernail clams in laboratory studies. Mean concentrations of NH, in pore water at sites containing fingernail clams was 40 ug/L and ranged from 3 to 100 ug/L. At sites where fingernail clams were nonexistent, NH3 ranged from 3 to 375 ug/L with a mean of 57 ugfL. Mean un-ionized ammonia concentrations at sites containing fingernail clams were significantly different from and consistently lower than sites without fingernail clams. / Department of Natural Resources and Environmental Management
1262

Thermoelectric Effects In Mesoscopic Physics

Cipiloglu, Mustafa Ali 01 January 2004 (has links) (PDF)
The electrical and thermal conductance and the Seebeck coefficient are calculated for one-dimensional systems, and their behavior as a function of temperature and chemical potential is investigated. It is shown that the conductances are proportional to an average of the transmission probability around the Fermi level with the average taken for the thermal conductance being over a wider range. This has the effect of creating less well-defined plateaus for thermal-conductance quantization experiments. For weak non-linearities, the charge and entropy currents across a quantum point contact are expanded as a series in powers of the applied bias voltage and the temperature difference. After that, the expansions of the Seebeck voltage in temperature difference and the Peltier heat in current are obtained. Also, it is shown that the linear thermal conductance of a quantum point contact displays a half-plateau structure, almost flat regions appearing around half-integer multiples of the conductance quantum. This structure is investigated for the saddle-potential model.
1263

Comparative effects of the CRF agonist, ovine CRF, and CRF antagonist, astressin, on homecage behavior patterns and defense in the mouse / Comparative effects of the CRF agonist, ovine CRF, and antagonist, astressin, on homecage behavior patterns and defense in the mouse

Farrokhi, Catherine F. Borna January 2005 (has links)
Thesis (M.A.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 34-45). / 52 leaves, bound ill. 29 cm
1264

Aspects of the manganese nutrition of lupins : redistribution of accumulated manganese and the diagnosis, prognosis and prevention of manganese deficiency / by R.J. Hannam

Hannam, R. J. (Robert James) January 1984 (has links)
Mounted ill. / Offprint of the author's journal article in pocket / Includes bibliographies / xiii, 248 leaves, [50] leaves of plates, [3] folded leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1985
1265

On the effect of UV-irradiation on DNA replication in Escherichia coli / Meera Mary Verma

Verma, Meera Mary January 1985 (has links)
Bibliography: leaves 267-287 / xviii, 287, [ca. 40] leaves, [10] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1985
1266

The effect of whole body heating on testis morphology and fertility of male mice / by Jakrit Yaeram.

Jakrit Yaeram January 2002 (has links)
"April 2002" / Includes bibliographical references (leaves 200-249) / xv, 249 leaves : ill., plates (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2003
1267

Identification Studies of Bacillus Spores Using Fluorescence Spectroscopy

Kunnil, Joseph January 2005 (has links)
Fluorescence spectroscopy was examined as a potential technique for identifying aerosol particles like bacterial spores. This technique was used for laboratory measurements on some common biological agent simulants. We have measured the intrinsic steady-state fluorescence emission spectra as a function of the excitation wavelength for several bacterial spores (washed and unwashed) in dry and aqueous suspensions at room temperature using excitation wavelengths from 200 to 600 nm. These measurements were compared to those of common, naturally occurring biological components like fungal spores and pollen and non spore samples like ovalbumin. The spectra of samples were combined into fluorescence profiles or fluorescence fingerprints. Different substrates were used for collection and detection of spores. Each bacterium produces a unique in vitro fluorescence profile when measured in dried and aqueous suspension and exhibits a strong maximum in its fluorescence emission spectrum near 330-340 nm. The fluorescence profiles were reproducible. The complexity of microorganisms made the interpretation of their spectral signature a difficult task. Principal components analysis (PCA) and cluster analysis were done as a data reduction technique for detection and identification from different backgrounds. PCA illustrates that linear combination of detected fluorescence intensities, which are present in different ratios in each of samples studied, can be used to discriminate biological agent simulants from other biological samples. The hydration effects, washing effects and the role of tryptophan on spore fluorescence were also investigated. The emission spectra of the dried spores showed a maximum near 330 nm, suggesting a hydrophobic environment for its tryptophan residues. The aqueous solution of tryptophan showed fluorescence shifted to 360 nm and in ethanol solution the maximum was shifted to 340 nm, suggesting a rather more polar average location of the tryptophan. To find the limit of detection we measured the quantum efficiency (QE) of a few samples. We concluded that spectroscopy techniques coupled with effective interpretation models are applicable to biological simulants agents. Index Heading: Bacteria; Spores; Identification; Fluorescence; Fluorescence Quantum Efficiency; Principal Components Analysis; Cluster Analysis.
1268

Chronic cannabis use and attention-modulated prepulse inhibition of the startle reflex in humans

Kedzior, Karina Karolina January 2004 (has links)
Background. Various studies show that cannabis use alters attention and cognitive functioning in healthy humans and may contribute to development of schizophrenia or worsening of pre-existing psychosis. However, the impact of cannabis use on brain function in humans is not well understood. Schizophrenia is associated with a deficit in prepulse inhibition (PPI), the normal inhibition of the startle reflex by a non-startling stimulus (prepulse), presented before the startle stimulus at short time intervals (lead-time intervals). Such PPI deficit is thought to reflect a sensorimotor gating dysfunction in schizophrenia. PPI is also modulated by attention and PPI reduction in schizophrenia is observed when patients are asked to attend to, not ignore, the stimuli producing PPI. The aim of the current study was to investigate the association between self-reported chronic cannabis use and attentional modulation of PPI in healthy controls and in patients with schizophrenia. Furthermore, the association between cannabis use and other startle reflex modulators, including prepulse facilitation (PPF) of the startle reflex magnitude at long lead-time intervals, prepulse facilitation of the startle reflex onset latency and habituation of the startle reflex magnitude, were examined. Method. Auditory-evoked electromyographic signals were recorded from orbicularis oculi muscles in chronic cannabis users (29 healthy controls and 5 schizophrenia patients) and non-users (22 controls and 14 patients). The data for 36 participants (12 non-user controls, 16 healthy cannabis users, and eight non-user patients) were used in the final analyses and the patient data were used as a pilot study, because relatively few participants met the rigorous exclusionary criteria. Participants were instructed to attend to or to ignore either the startle stimuli alone (70 100 dB) or prepulse (70 dB) and startle stimuli (100 dB) separated by short lead-time intervals (20 200 ms) and long lead-time intervals (1600 ms). In order to ignore the auditory stimuli the participants played a visually guided hand-held computer game. A pilot study showed that the response component of playing the game had no effects on attentional modulation of the startle reflex magnitude and onset latency. Results. Relative to controls, cannabis use in healthy humans was associated with a reduction in PPI similar to that observed in schizophrenia while attending to stimuli, and with an attention-dependent dysfunction in the startle reflex magnitude habituation. While ignoring the stimuli there were no statistical differences in PPI between cannabis users and controls, although PPI in cannabis users tended to differ from that of the patients. The reduction in PPI in cannabis users was correlated with the increased duration of cannabis use, in years, but not with the concentration of cannabinoid metabolites in urine or with the recency of cannabis use in the preceding 24 hours. Furthermore, cannabis use was not associated with any differences in PPF, onset latency facilitation, and startle reflex magnitude in the absence of prepulses. The accuracy of self-reports of substance use was also investigated in this study and was found to be excellent. In addition, the study examined the validity of the substance use module of the diagnostic interview, CIDI-Auto 2.1, which was found to be acceptable for cannabis misuse diagnoses (abuse and/or dependence). Finally, cannabis dependence was found to be associated with more diagnoses of mental illness other than schizophrenia (mainly depression). Conclusions. The results of the current study suggest that chronic cannabis use is associated with schizophrenia-like deficit in PPI in otherwise healthy humans. This PPI reduction is associated with attentional impairment rather than a global sensorimotor gating deficit in healthy cannabis users.
1269

Les déterminants des performances scolaires des écoles rurales : l’exemple des élèves de CM2 des classes à plusieurs cours dans les Alpes de Haute-Provence / The determinants of academic performance of rural schools : the example of the CM2 pupils in the multigrade classrooms situated in the Alpes de Haute-Provence

Lallaï, Daniel 05 December 2016 (has links)
Dans les années 1960/1970, toutes les études ont montré que les élèves issus de milieux défavorisés ont de moins bons résultats que ceux issus de milieux favorisés (Coleman, 1966 ; Bourdieu & Passeron, 1964 et 1970 ; Baudelot & Establet, 1971). Les recherches menées durant les années 1990/2000 ont démontré que les élèves des écoles rurales obtiennent de bonnes performances scolaires (Oeuvrard, 1993 ; Lebossé, 1998, les travaux de l’Observatoire de l’École Rurale, 2001 et 2005). Or, les territoires ruraux sont majoritairement composés de familles issues de milieux défavorisés. Quelles sont alors les raisons de ces bons résultats ? La présente étude a pour objectif de vérifier les hypothèses selon lesquelles un effet-établissement, un effet-classe et un effet-maître, spécifiques aux écoles rurales expliquent ces performances. Afin de valider ces hypothèses, une enquête est menée concernant les résultats aux évaluations nationales de 2011, des 1 810 élèves de CM2 des écoles du département des Alpes de Haute-Provence. Elle est exploitée au moyen de calculs statistiques et d’une analyse de contenu des rapports d’inspection des enseignants de ces élèves. Les conclusions de cette recherche révèlent que ce sont des effets structurels, liés à la spécificité des écoles rurales qui sont les déterminants de ces résultats scolaires. Ce sont en effet, les écoles primaires, celles de moins de cinq classes, les classes à plusieurs cours, le peu d’élèves scolarisés dans une classe ainsi que les gestes professionnels spécifiques et les qualités professionnelles des enseignants qui expliquent ces performances. / In the 1960s/1970s, all the studies have reported that pupils from disadvantaged backgrounds perform less well in school than those from advantaged backgrounds (Coleman, 1966 ; Bourdieu & Passeron, 1964 et 1970 ; Baudelot & Establet, 1971).Research during the 1990s/2000s has shown that pupils from rural schools get good performance (Oeuvrard, 1993 ; Lebossé, 1998, the works of the Rural School Observatory, 2001 et 2005).Yet rural territories are mostly composed of families who come from disadvantaged backgrounds. So, what are the reasons for these good results ?The objective of this study is to test the hypotheses that the effect of the establishment, the effect of the class and the effect of the teacher, which are specific to rural school, explain this good performance.To validate these hypotheses, a survey was conducted concerning the results of national assessments in 2011, for the 1810 pupils in CM2 of the schools situated in the department of Alpes de Haute-Provence. The data is used by means of statistical calculations and a content analysis of the inspection reports of these pupils' teachers.The findings of this research reveal that it is structural effects which are linked to the specificity of rural schools that are the determinants of these educational outcomes. These are in fact primary schools, those less than five classes, multigrade classrooms, only a few pupils enrolled in a class as well as teachers' specific professional acts and professional skills that explain this good performance.
1270

Interlaminar bonding in ultrasonic consolidation

Edmonds, Hannah January 2012 (has links)
Ultrasonic Consolidation (UC) is a solid state additive manufacturing process which fabricates three-dimensional objects by ultrasonically joining metal foils together, layer-bylayer, to form a solid part. A wide range of materials can be used to fabricate parts by UC and products with complex internal geometry can be generated by shaping the crosssection throughout the build using Computer Numerically Controlled (CNC) milling. As a result of its ability to embed various secondary materials and fibres in metal matrices, UC has emerged as a potential method of fabricating multi-functional materials and structures.

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