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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.
41

Seasonal temperature reconstructions on the north Icelandic shelf : evidence from stable isotope values of marine bivalves

Dietrich, Kristin A. 25 January 2007 (has links)
Recent episodes of extreme weather and the drastic consequences they can have for ecosystems, societies, and economies, emphasize the need for a better understanding of Earths climate. In order to gain a better understanding of modern and future climate, a more thorough knowledge of past climates at the highest resolution possible from different regions is necessary. To this end, a study of seasonal temperature variability in the waters off the northern coast of Iceland was undertaken. Twenty-six bivalves were selected from marine sediment cores recovered from the northern and northwestern coasts of Iceland. Bivalves were selected from intervals of climatic interest as determined from sedimentological characteristics. Shells were micromilled and the carbonate analysed for stable oxygen and carbon isotope values. Oxygen isotope values are driven principally by the temperature of the water from which the shell was precipitated. These data provide a time-series of discrete climate profiles of seasonal temperature variations from c. 360 cal yr BC to cal yr AD 1660, each recording 2 to 9 consecutive years of temperature variability. Several notable warm and cold periods were identified and characterized in terms of maximum and minimum temperatures. As this period overlaps the Viking Age (c. 790 to 1070) and the establishment of Norse colonies in Iceland and Greenland, the temperature record was compared with historical records and demonstrates the significant impact of variation in temperature seasonality on the establishment, development, and in some cases, collapse of societies in the North Atlantic.
42

Increased signal intensity of the cochlea on pre- and post-contrast enhanced 3D-FLAIR in patients with vestibular schwannoma

Nakashima, Tsutomu, Fukatsu, Hiroshi, Nihashi, Takashi, Kawai, Hisashi, Naganawa, Shinji, Yamazaki, Masahiro 12 1900 (has links)
名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成22年9月28日 山崎雅弘氏の博士論文として提出された
43

A high resolution geophysical investigation of spatial sedimentary processes in a paraglacial turbid outwash fjord: Simpson Bay, Prince William Sound, Alaska

Noll, Christian John, IV 12 April 2006 (has links)
Simpson Bay is a turbid, outwash fjord located in northeastern Prince William Sound, Alaska. A high ratio of watershead:basin surface area combined with high precipitation and an easily erodable catchment create high sediment inputs. Fresh water from heavy precipitation and meltwater from high alpine glaciers enter Simpson Bay through bay head rivers and small shoreline creeks that drain the catchment. Side scan sonar, seismic profiling, and high resolution bathymetry were used to investigate the record of modern sedimentary processes. Four bottom types and two seismic faces were described to delineate the distribution of sediment types and sedimentary processes in Simpson Bay. Sonar images showed areas of high backscatter (coarse grain sediment, bedrock outcrops and shorelines) in shallow areas and areas of low backscatter (estuarine mud) in deeper areas. Seismic profiles showed that high backscatter areas reflected emergent glacial surfaces while low backscatter areas indicated modern estuarine mud deposition. The data show terminal morainal bank systems and grounding line deposits at the mouth of the bay and rocky promontories, relict medial moraines, that extend as terrestrial features through the subtidal and into deeper waters. Tidal currents and mass wasting are the major influences on sediment distribution. Hydrographic data showed high spatial variability in surface and bottom currents throughout the bay. Bottom currents are tide dominated, and are generally weak (5-20 cm s-1) in the open water portions of the bay while faster currents are found associated with shorelines, outcrops, and restrictive sills. Tidal currents alone are not enough to cause the lack of estuarine mud deposition in shallow areas. Bathymetric data showed steep slopes throughout the bay suggesting sediment gravity flows. Central Alaska is a seismically active area, and earthquakes are most likely the triggering mechanism of the gravity flows.
44

Application of e-TDR to achieve precise time synchronization and controlled asynchronization of remotely located signals

Sripada, Aparna 14 January 2014 (has links)
Time Domain Reflectometer (TDR) measures the electrical length of a cable from the applied end to the location of an impedance change. An impedance change causes a portion of the applied signal to reflect back based on the value of its reflection coefficient. The time of flight (TOF) between the applied and reflected wave is computed and multiplied with previously determined signal propagation velocity to determine the location of the impedance change. We intentionally open terminate the output end of the cable which makes the reflection coefficient be maximum (=1) to measure its electrical length. Conventional TDRs designed for testing integrity of long cables use various closed pulse shaped test signals i.e. the half sine wave and the Gaussian pulse, that disperse (change shape) and change velocity while propagation along the cable. Quoting Dr. Leon Brillouin’s comments on electromagnetic energy propagation [10], “in a vacuum, all waves (e.g. frequencies) propagate at the same velocity, hence withoutdistortion, whereas in a dispersive lossy media, except for an infinitely long sinusoidal waveform, distortion will occur due to frequency dependent velocity.” This signal distortion generally degrades the accuracy of the measurement of the signal’s TOF. We discuss here an Enhanced Resolution Time Domain Reflectometer (e-TDR). The enhanced resolution is due to a newly discovered signal called SPEEDY DELIVERY (SD) by Dr. Robert Flake at The University of Texas at Austin (US PATENT 6,441,695 B1 issued in August 27, 2002). This SD signal has a propagation velocity that is a programmable constant and this signal preserves its shape during propagation through dispersive lossy media (DLM). This signal behavior allows us to use ‘e-TDR’ in applications where remotely located signals need to be synchronized or asynchronized precisely. Potential applications include signal based synchronization of devices like sensors connected in a network. Since the cable carrying data from sensors at discrete and remote locations to a collecting center have different electrical lengths, it is necessary to precisely offset the timestamp of the incoming signal from these sensors to allow accurate data fusion. Our prototype is capable of synchronizing signals 1,200 ft (~ 400 m) apart with sub-nanosecond resolution. / text
45

High resolution microwave and infrared spectroscopy of four-membered heterocyclic compounds

Chen, Ziqiu January 2011 (has links)
High resolution molecular spectroscopic techniques are useful tools to accurately probe energy differences between quantum states of molecules. These energy levels are inherently dependent on the underlying potential functions, which ultimately govern the structures and dynamics of molecules. Thus, the detailed characterization of potential energy profiles through molecular spectroscopy provides important information about molecular properties. Given the increased structural and dynamic complexity of large molecules, small compounds serve as excellent prototypes to establish quantum mechanical models that accurately characterize quantum states and ultimately potential energy functions of various molecular classes. This thesis describes the use of rotational and rovibrational spectroscopy to probe one such class: four-membered heterocycles. Rotationally-resolved vibrational spectra of four-membered rings including β-propiolactone (c-C3H4O2), 3-oxetanone (c-C3H4O2), azetidine (c-C3H6N) and silacyclobutane (c-C3H8Si) were recorded below 1200 cm-1 using a Fourier transform infrared spectrometer (FTIR) with synchrotron light at the far infrared beamline of the Canadian Light Source (CLS). Additionally, Fourier transform microwave (FTMW) spectroscopy was used to study the pure rotational spectra of β-propiolactone and silacyclobutane for the first time. This allowed the accurate characterization of the ground vibrational state and molecular structure in support of the rovibrational analysis. The far infrared vibrational modes of these four molecules were analyzed individually initially and followed by a global fit of all observed transitions of each molecule. Unique spectroscopic signatures arising from Coriolis coupling(β-propiolactone, 3-oxetanone), tunneling motions (azetidine, silacyclobutane) and the large amplitude ring puckering vibration (3-oxetanone, azetidine, silacyclobutane) were revealed and treated. The resultant Hamiltonian models used for each molecule account for the observed spectra as the spectroscopic constants are consistent across the ground state and all vibrationally excited states studied. Collectively, these studies have provided a highly effective working protocol for the treatment of high resolution rovibrational data to model the dynamic behaviour of real molecules.
46

DEFINING THE DISTRIBUTION, SOURCE, FATE AND TRANSPORT OF NITRATE IN GROUNDWATER BENEATH AN AGRICULTURALLY INTENSIVE REGION USING HIGH-RESOLUTION PROFILING METHODS

2014 September 1900 (has links)
The hydrogeology, stable isotope distribution, and chemical distribution of Cl- and NO3--N within the Battersea Drainage Basin in southern Alberta were investigated. The Battersea Drainage Basin is characterized by widespread spreading of livestock manure on irrigated farmland and a high density of feedlots, creating concern about groundwater quality in the region. Past research has used conventional piezometers to study the source, distribution and fate of nitrate in the shallow groundwater. The key component of this research involved using the new technique of high-resolution profiling to determine the distribution, source, fate, and transport of nitrate in the shallow geological groundwater environment. High-resolution profiles of δ2H indicated groundwater throughout the glaciofluvial deposits and between 5.4 and 13.7 m below ground in glaciolacustrine deposits contained values > -150.0‰ and tritiated waters (> 0.08 TU). This suggested that this water recharged within the past 60 years. At depth 5.4 to 13.5 m BG, lower δ2H values did not coincide with detectable tritium, indicating the groundwater was much older and not vulnerable to agricultural contamination. High-resolution profiles of Cl- and NO3--N (solid core and squeezed pore water data) showed concentrations of these ions up to 411 and 219 mg L-1, respectively, in the glaciofluvial deposits. Concentrations of Cl- and NO3--N decreased to less than 50 mg L-1 (Cl-) and the Drinking Water Standard for NO3--N (10 mg L-1) in the underlying glaciolacustrine and glacial till deposits at most sites. Comparison to the high-resolution δ2H profiles suggested the high nitrate concentration in the glaciofluvial sediments is agricultural in origin. High concentrations for Cl- and NO3--N (up to 257 and 209 mg L-1, respectively) observed in glacial till and glaciolacustrine deposits below 6.0 m BG at two sites (LB5a and LB6) did not coincide with modern water, indicating the source of high nitrate is geologic in origin. The NO3--N to Cl- ratios suggested denitrification was not appreciable in the glaciofluvial deposits. However, denitrification may be a cause of decreased nitrate in the underlying fine textured deposits at certain sites. Interpretation of the high resolution profiles also suggested that the major conduit for nitrate migration is in near-surface glaciofluvial sediments via advection. The distributions of δ2H, Cl- and NO3--N with depth suggest that transport in the underlying glaciolacustrine and glacial till deposits is diffusion dominated, thus acting as a sink and removing nitrate from the permeable zone. However, the presence of fracturing in the oxidized zone of glacial tills and glaciolacustrine deposits suggests that transport may occur via advection through fracturing and diffusion in the material matrix. High-resolution profiling of δ2H, Cl- and NO3--N proved to be valuable in obtaining information regarding the distribution, source, and transport of groundwater and nitrate in the shallow groundwater environment at a level of detail that cannot be readily obtained through use of conventional piezometers.
47

High resolution microwave and infrared spectroscopy of four-membered heterocyclic compounds

Chen, Ziqiu January 2011 (has links)
High resolution molecular spectroscopic techniques are useful tools to accurately probe energy differences between quantum states of molecules. These energy levels are inherently dependent on the underlying potential functions, which ultimately govern the structures and dynamics of molecules. Thus, the detailed characterization of potential energy profiles through molecular spectroscopy provides important information about molecular properties. Given the increased structural and dynamic complexity of large molecules, small compounds serve as excellent prototypes to establish quantum mechanical models that accurately characterize quantum states and ultimately potential energy functions of various molecular classes. This thesis describes the use of rotational and rovibrational spectroscopy to probe one such class: four-membered heterocycles. Rotationally-resolved vibrational spectra of four-membered rings including β-propiolactone (c-C3H4O2), 3-oxetanone (c-C3H4O2), azetidine (c-C3H6N) and silacyclobutane (c-C3H8Si) were recorded below 1200 cm-1 using a Fourier transform infrared spectrometer (FTIR) with synchrotron light at the far infrared beamline of the Canadian Light Source (CLS). Additionally, Fourier transform microwave (FTMW) spectroscopy was used to study the pure rotational spectra of β-propiolactone and silacyclobutane for the first time. This allowed the accurate characterization of the ground vibrational state and molecular structure in support of the rovibrational analysis. The far infrared vibrational modes of these four molecules were analyzed individually initially and followed by a global fit of all observed transitions of each molecule. Unique spectroscopic signatures arising from Coriolis coupling(β-propiolactone, 3-oxetanone), tunneling motions (azetidine, silacyclobutane) and the large amplitude ring puckering vibration (3-oxetanone, azetidine, silacyclobutane) were revealed and treated. The resultant Hamiltonian models used for each molecule account for the observed spectra as the spectroscopic constants are consistent across the ground state and all vibrationally excited states studied. Collectively, these studies have provided a highly effective working protocol for the treatment of high resolution rovibrational data to model the dynamic behaviour of real molecules.
48

High resolution imaging of bio-molecular binding studies studies using a Widefield surface Plasmon Microscope.

Denyer, Morgan C.T., Jamil, M.M. Abdul, Twigg, Peter C., Youseffi, Mansour, Britland, Stephen T., Liu, S., See, Chung Wah, Zhang, J., Sommekh, M.G. 14 September 2009 (has links)
Surface plasmon microscopes are mostly built around the prism based Kretschmann configuration. In these systems, an image of a sample can be obtained in terms of an intensity map, where the intensity of the image is dependent on the coupling of the light into the surface plasmons. Unfortunately the lateral resolution of these systems relies on the ability of plasmons to propagate along the metallised layer and is usually limited to a few microns unless special measures are taken. The widefield surface plasmon microscope (WSPR), used here enables surface plasmon imaging at significantly higher lateral resolutions than prism based systems. In this study we demonstrate the functionality of the WSPR by imaging a sequence of binding events between micro-patterned extracellular matrix proteins and their specific antibodies. Using the WSPR system a change in contrast was observed with each binding event. Images produced via the WSPR system were analyzed and compared qualitatively and quantitatively. Consequently, we confirm that the WSPR microscope described here can be used to study sequential monomolecular layer binding events on a micron scale. These results have significant implications in the development of new micron scale bioassays.
49

Laser spectroscopy of caesium dimers

Butcher, Louise Sara January 1997 (has links)
We have obtained spectra of 10 vibrational bands of the Cs<sub>2</sub> (2)<sup>3</sup>∏<sub>u</sub> ← ϰ<sup>3</sup>∑<sup>+</sup><sub>9</sub> system. The molecules were formed in a supersonic free jet expansion, and were excited by light from a single mode CW dye laser. The total laser induced fluorescence was measured at 90° to the incident light and molecular beam, using a photomultiplier. Using a slit system to image a selected part of the interaction region, we have reduced the Doppler width to about 350MHz. We have been able to resolve the discrepancy between the different vibrational band positions given in two previous papers. Our vibrational bands show broad rotational contours, but we have not been able to resolve individual rotational lines. We have also obtained rotationally resolved spectra of the bandhead region of 22 vibrational bands of the Β<sup>1</sup>∏<sub>9</sub> ← X<sup>1</sup>∑<sup>+</sup><sub>u</sub> system. We found that the frequencies of the bandheads agreed with the bandhead positions deduced from the Dunham coefficients of a previous work. We have developed a theoretical model of the rotational structure and intensity distribution, taking into account optical pumping and the small solid angle subtended by the detector. By fitting this model to the experimental spectrum of the v' = 3,u∿ = 0 band using least squares optimization, we were able to extract rotational constants and line positions. We found that these line positions were in good agreement with those from the previous work. We have discussed how such spectroscopic data may be used in a determination of the s-wave scattering length of caesium, and we have reviewed the validity of the scattering length and other pararneterisations of low energy Cs-Cs interactions.
50

20mm以下の肝海綿状血管腫のMRIによる描出

Hara, Suguru, Miyahara, Masaharu, Tanaka, Tokuaki, Oota, Daiki, Suzuki, Yasuo, Okayasu, Naoki, Maeda, Hisatoshi, Toyooka, Nobuo, 原, 英, 宮原, 政春, 田中, 徳明, 太田, 大喜, 鈴木, 康夫, 岡安, 直樹, 前田, 尚利, 十八日, 信夫 08 1900 (has links)
No description available.

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