• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 3
  • 1
  • 1
  • Tagged with
  • 12
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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

Species diversity, habitat utilization and blood parasites of amphibians in and around Ndumo Game Reserve / Edward Charles Netherlands

Netherlands, Edward Charles January 2014 (has links)
Ndumo Game Reserve is the only officially protected area within the Phongolo Floodplain; an area in the northern parts of KwaZulu-­‐Natal known to boast a rich diversity of amphibians, thus becoming one of the focal areas for this study. The study’s aim was to monitor and record amphibian diversity, as well as associated blood parasite biodiversity. For the purpose of monitoring, a number of active and passive techniques were employed. Habitat preferences for the expected species were divided into five types, namely endorheic, lacustrine, palustrine, riverine and terrestrial. Endorheic habitats were found to harbour the highest diversity (70%) of frog species. A permanent song meter was used to passively record calling activity of frog species associated with endorheic systems. This call data indicated peak breeding season, preferred calling times and intensities of the different species. Historical records from the same area were used as a basis to which this study’s data were compared. In the case of the polychromatic Argus Reed Frog Hyperolius argus Peters, 1854, questions were raised concerning the major colour changes during development of the apparent sub-­‐adult to adult life stages, an observation which was has caused some confusion as to whether these forms represented a single species or multiple cryptic species. These issues were clarified using techniques such as DNA extraction and polymerase chain reaction (PCR). Furthermore, a blood parasite survey was conducted. Thin blood smears for morphometrics and whole blood for molecular work, were collected from 29 species and 436 individual frogs. For the majority of the recorded parasites, techniques such as light microscopy were utilized for the morphological description and classification of these parasites. Among the recorded frog blood parasites observed, 20% of the frog specimens were infected with at least one blood parasite group. Hepatozoon and Trypanosoma species accounted for most of the infections; the former demonstrated significant differences in intensity of infection across species, families and habitat types (P = 0.028; P = 0.006; P = 0.007 respectively). Methods, such as transmission electron microscopy, examining the ultrastructure, as well as parasite DNA extraction and 18S rDNA gene sequences for the molecular and phylogenetic characterization, were reserved for Hepatozoon species infecting common toad species (Amietophrynus). Parasite stages observed were measured and compared to each other, as well as to other described African bufonid haemogregarines. Resulting sequences were compared with each other and to comparative haemogregarine sequences selected from GenBank. In the current study a number of important aspects with regards to monitoring and assessment of amphibians in their natural environment were explored, including looking at and determining diversity and prevalence of blood parasites. Furthermore, important data on gaining a better understanding of amphibians and their behavioural activities were also gathered, which should be able to assist in conservation actions to effectively protect South African anurans and their required habitat types. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
2

Species diversity, habitat utilization and blood parasites of amphibians in and around Ndumo Game Reserve / Edward Charles Netherlands

Netherlands, Edward Charles January 2014 (has links)
Ndumo Game Reserve is the only officially protected area within the Phongolo Floodplain; an area in the northern parts of KwaZulu-­‐Natal known to boast a rich diversity of amphibians, thus becoming one of the focal areas for this study. The study’s aim was to monitor and record amphibian diversity, as well as associated blood parasite biodiversity. For the purpose of monitoring, a number of active and passive techniques were employed. Habitat preferences for the expected species were divided into five types, namely endorheic, lacustrine, palustrine, riverine and terrestrial. Endorheic habitats were found to harbour the highest diversity (70%) of frog species. A permanent song meter was used to passively record calling activity of frog species associated with endorheic systems. This call data indicated peak breeding season, preferred calling times and intensities of the different species. Historical records from the same area were used as a basis to which this study’s data were compared. In the case of the polychromatic Argus Reed Frog Hyperolius argus Peters, 1854, questions were raised concerning the major colour changes during development of the apparent sub-­‐adult to adult life stages, an observation which was has caused some confusion as to whether these forms represented a single species or multiple cryptic species. These issues were clarified using techniques such as DNA extraction and polymerase chain reaction (PCR). Furthermore, a blood parasite survey was conducted. Thin blood smears for morphometrics and whole blood for molecular work, were collected from 29 species and 436 individual frogs. For the majority of the recorded parasites, techniques such as light microscopy were utilized for the morphological description and classification of these parasites. Among the recorded frog blood parasites observed, 20% of the frog specimens were infected with at least one blood parasite group. Hepatozoon and Trypanosoma species accounted for most of the infections; the former demonstrated significant differences in intensity of infection across species, families and habitat types (P = 0.028; P = 0.006; P = 0.007 respectively). Methods, such as transmission electron microscopy, examining the ultrastructure, as well as parasite DNA extraction and 18S rDNA gene sequences for the molecular and phylogenetic characterization, were reserved for Hepatozoon species infecting common toad species (Amietophrynus). Parasite stages observed were measured and compared to each other, as well as to other described African bufonid haemogregarines. Resulting sequences were compared with each other and to comparative haemogregarine sequences selected from GenBank. In the current study a number of important aspects with regards to monitoring and assessment of amphibians in their natural environment were explored, including looking at and determining diversity and prevalence of blood parasites. Furthermore, important data on gaining a better understanding of amphibians and their behavioural activities were also gathered, which should be able to assist in conservation actions to effectively protect South African anurans and their required habitat types. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
3

Polychromatic determination of spectral response of PV devices

Sara, Ira D. January 2014 (has links)
This thesis introduces a novel spectral response (SR) measurement technique using polychromatic filters (filters with very broad spectral transmittances) to determine SR of large area PV devices. Conventionally, SR of a photovoltaic (PV) device is determined by illuminating the device under test (DUT) with a series of monochromatic beams at different wavelengths as described in the international standard IEC 60904-8, or beams of limited spectral content using narrow band pass filters or monochromator. One significant problem associated with the application of the narrow band pass filters for a large-area SR measurement is that low light intensity produced on the measurement plane particularly in certain wavelength ranges: the ultraviolet and infrared. This can produce weak signal responses from a tested PV device. In addition, the imperfection of the filter s mounting position can shift the peak wavelength of the filter s transmittance at angle of incidence greater than 10°. This can cause stray light on the measurement plane. The proposed SR measurement method is called the 'polychromatic SR fitting method' or, in short, it is known as the 'polychromatic method'. The advantage of this method is that higher beam intensity can be produced on the measurement plane as a result of large spectral transmittance of the polychromatic filters. This can improve the signal strength of a tested PV device. This new SR measurement method works by comparing the variations in the currents which are measured at different spectra to the currents which are calculated at the same spectral conditions using the SR model. Validations of this method for a large- and small-area SR determinations show that it is potentially feasible as a new technique for determining SR of a PV device with deviations within ±2% across the wavelength bands.
4

Development of a Fast X-ray Line Detector System for Two-Phase Flow Measurement

Song, Kyle 21 December 2016 (has links)
Measuring void fraction distribution in two-phase flow has been a challenging task for many decades because of its complex and fast-changing interfacial structure. In this study, a non-intrusive X-ray measurement system is developed and calibrated to mitigate this challenge. This approach has several advantages over the conventional methods such as the multi-sensor conductivity probe, wire-mesh sensor, impedance void meter, or direct optical imaging. The X-ray densitometry technique is non-intrusive, insensitive to flow regime changes, capable of measuring high temperature or high-pressure flows, and has reasonable penetration depth. With the advancement of detector technology, the system developed in this work can further achieve high spatial resolution (100 micron per pixel) and high temporal resolution (1000 frames per second). This work mainly focuses on the following aspects of the system development: establishing a geometrical model for the line detector system, conducting spectral analysis for X-ray attenuation in two-phase flow, and performing calibration tests. The geometrical model has considered the measurement plane, geometry of the test-section wall and flow channel, relative position of the X-ray source and detector pixels. By assuming axisymmetry, an algorithm has been developed to convert void fraction distribution along the detector pixels to the radial void profile in a circular pipe. The X-ray spectral analysis yielded a novel prediction model for non-chromatic X-rays and non-uniform structure materials such as the internal two-phase flow which contains gas, liquid and solid wall materials. A calibration experiment has been carried out to optimize the detector conversion factor for each detector pixels. Finally, the data measured by the developed X-ray system are compared with the double-sensor conductivity probe and gas flow meter for sample bubbly flow and slug flow conditions. The results show reasonable agreement between these different measuring techniques. / Master of Science / Two-phase flow is a widely observed phenomenon in a nuclear reactor operation and thermal hydraulic applications during thermal energy transfer process. Hence, precise understanding of two-phase flow model is essential to a thermal hydraulic design and safe operation of nuclear reactor operation systems. However, two-phase flow analysis, via measuring void fraction distribution of a two-phase flow, has been a challenging task for many decades because of its complex and dynamical interfacial characteristics. In this study, a nonintrusive X-ray measuring technique is developed to mitigate some of the conventional challenges of void fraction measurement of a two-phase flow. The void fraction imagery via X-ray densitometry technique is insensitive to flow regime changes at high temperature or high pressure flows conditions with reasonable penetration depth capabilities. Together, with the advanced detector technology and spectral analysis of the X-ray attenuation in two-phase flow, this study delivers both qualitative and quantitative geometrical model for the line detector system to provide a radial void profile of a circular pipe. Moreover, the X-ray spectral analysis yielded a novel prediction model of a non-chromatic X-rays and non-uniform structure materials such as the internal two-phase flow which contains gas, liquid, and solid pipe materials. A calibration experiment has been carried out to optimize the detector conversion factor for each detector pixels. Finally, the data measured by the developed X-ray system are compared with the double-sensor conductivity probe and gas flow meter for sample bubbly flow and slug flow conditions. The results show reasonable agreement between these different measuring techniques.
5

Imunofenotypové rozdíly v B lymfocytárních populacích non-memory B lymfocytů u zdravých kontrol a pacientů s imunopatologiemi. / Immunophenotype differences in non-memory B lymphocyte populations in healthy controls and patients with immunopathologies

Polák, Milan January 2014 (has links)
B-lymphocytes are a subset of immune cells that can be distinguished mainly by carrying clonally diversified membrane-bound immunoglobulin specialized to specific antigen recognition. Together with other immunocytes B-lymphocytes play a central role in adaptive immune system which takes part in defense of the host against wide variety of pathogens. Recently the evidence has supported the emerging concept of different B-cell subpopulations to play a direct or indirect role in a pathogenesis of spectrum of disorders. However, so far the knowledge has been limited mainly in the way of how the specific differentiation stages of B-lymphocytes are involved in pathogenesis of diseases and how course of disease, stage, and eventually different treatment can affect B-cell homeostasis. That is the reason for the thesis to be focused on an analysis of B-cell population profile changes in disease, identification of any association present among specific B-cell subpopulations, as well as association between these subpopulations and clinical parameters. Using polychromatic flow cytometry we analyzed frequencies of 11 B-cell subpopulations including stages of transient B-lymphocytes through effector antibody-producing plasma cells. We examined 81 individuals including 22 healthy controls and 59 patients with...
6

Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter

Engström, Jens January 2011 (has links)
Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface. The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions. Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.
7

Imunotypové rozdíly v subpopulacích CD27+ B lymfocytů u zdravých kontrol a pacientů s různými imunopatologiemi / Differences in immunophenotype of CD27+ B lymphocyte subpopulations in healthy controls and patients with various immunopathologies

Valatová, Pavla January 2016 (has links)
The immune system will maintain the integrity of the organism from harmful non-malicious recognizes and protects the body against exo- and endogenous toxic substances and together with the nervous and endocrine system are among regulatory systems of the organism. Recently the evidence has supported the emerging concept of different B cell subpopulations to play a direct or indirect role in a pathogenesis of spectrum of disorders. However, so far the knowledge has been limited mainly in the way of how the specific differentiation stages of B lymphocytes are involved in pathogenesis of diseases and how course of disease, stage, and eventually different treatment can affect B cell homeostasis. This work is focused on the study of peripheral CD27+ B lymphocytes (one of the least explored human B lymphocytes) in healthy controls and patients with various immunopathologies, in this case we present representative results for patients with inflammatory bowel disease. Using polychromatic flow cytometry we examined 31 of peripheral blood samples, including 14 controls, 7 patients with Crohn's disease (CD) and 5 with ulcerative colitis (UC). In 6 patients with CD, we were able to perform immunophenotyping also 2 hours after intravenous administration of infliximab, and in one patient 14 days after drug...
8

Polar-Plane-Free Faceted InGaN-LEDs toward Highly Radiative Polychromatic Emitters / 高効率多色発光素子に向けた極性面フリーなマルチファセットInGaN-LEDに関する研究

Matsuda, Yoshinobu 23 March 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22449号 / 工博第4710号 / 新制||工||1736(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 川上 養一, 教授 野田 進, 教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
9

Hormetic UV treatments for control of plant diseases on protected edible crops

Scott, George January 2017 (has links)
Hormesis is a dose response phenomenon where low doses of a stress bring about a positive response in the organism undergoing treatment. UV-C hormesis has been known for over three decades and has a broad range of benefits on postharvest produce. Benefits include increased nutritional content, delayed chlorophyll degradation and disease resistance. The beneficial effects have been observed on many varieties of fresh produce including climacteric and non-climacteric fruit, tubers, salads and brassicas. The majority of previous studies have used low-intensity (LIUV) UV-C sources. LIUV sources require lengthy treatment times, which are in the region of 6 minutes for tomato fruit. This has, in part, prevented the commercial application of this technique. High-intensity, pulsed polychromatic light (HIPPL) sources, however, have recently been developed. HIPPL sources may have the potential to drastically reduce treatment times and increase their commercial viability. It was shown, here, that the use of HIPPL can control disease (reduce disease progression) caused by Botrytis cinerea and Penicillium expansum and also delay ripening on tomato fruit. Both disease control and delayed ripening were at similar levels for LIUV and HIPPL treatments on mature green fruit. The HIPPL treatments used in these studies can reduce treatment times for tomato fruit by 97.3%. Both HIPPL and LIUV treatments elicit local responses irrespective of the treatment orientation and tomato fruit, therefore, require full surface irradiation. Furthermore, UV-C in the HIPPL source is not required for disease control or delayed ripening. It does, however, contribute approximately 50% towards the total observed effects. Investigations into the mechanisms underpinning postharvest HIPPL and LIUV hormesis, on tomato fruit, identified that the expression of genes involved in plant hormone biosynthesis, defence, secondary metabolism and ripening were affected. This indicates that disease control is achieved through induced resistance. Changes to expression, following treatment, were highly similar for both HIPPL and LIUV treatments and were mediated by salicylic acid, jasmonic acid and ethylene. This may lead to broad range resistance against necrotrophic and biotrophic pathogens as well as abiotic stresses and herbivorous pests. Recently, the exposure of foliage to UV-C has been shown to induce resistance against B. cinerea on Arabidopsis thaliana. The horticultural applications of such treatments, however, have not been explored. Pre-harvest treatments of lettuce in the glasshouse showed variation in damage threshold and optimal treatment to control disease following LIUV and HIPPL treatment. Further sources of variation included the cultivar, pathogen of interest and the point that treatment was applied during the year. Using a controlled environment allowed seasonal variation to be mitigated and both HIPPL and LIUV treatments controlled disease against B. cinerea. For pre-harvest treatments to be a success in the glasshouse, further studies into how both biotic and abiotic factors influence treatment is required. To circumvent the problems associated with pre-harvest treatments and environmental variation in the glasshouse, LIUV seed treatments were performed on tomato. Control of B. cinerea was established with an approximately 10% reduction in incidence and disease progression with a 4 kJ/m2 treatment. When monitoring the effect of treatment on germination and early seedling development it was also identified that an 8 kJ/m2 treatment led to biostimulation of germination and root and shoot growth.
10

Změny v distribuci subpopulací B lymfocytů u pacientů s Crohnovou chorobou před a po biologické léčbě / Changes in distribution of B lymphocyte subpopulations in patients with Crohn disease before and after biological therapy

Suchá, Renata January 2016 (has links)
B-lymphocytes are lymphoid cells, which are a part of the adaptive/innate immune system and generate antibodies. Recently, many studies have supported hypothesis that different rather minor B-lymphocyte subpopulations may play a direct and indirect role in immunopathogenesis in human pathologies such as Crohn's disease (CD). The aim of current study was therefore to investigate distribution of frequencies of B lymphocyte subpopulations (from transient to mature effector B cell stages) in peripheral blood of healthy subjects (CO), patients with Crohn's disease (CD) and ulcerative colitis (UC). Thus, using 11-colour flow cytometry we have analysed 30 blood samples of individuals, including 14 healthy controls, 11 patients with Crohn's disease and 5 with UC. In 6 patients with CD we have had an opportunity to analyze blood samples collected 2 hours after an administration of anti-TNF therapy. Higher frequencies of memory B-lymphocytes (CD19+ CD27+ , CD19+ CD20+ CD27+ and CD19+ CD20+ CD27+ IgM+) were found in patients with CD as compared to COs. (20.06±13.58%; 17.61±13.48%; 88.60±20.56% vs. 11.75±26.47%; 11.25±26.50%; and 66.82±22.60%), in case of CD19+CD20-CD27-IgM+ B-lymphocytes the difference was statistically significant (57.15±17.21% in CD vs. 19.59±31.79% in CO; p=0.0341), which is in accordance...

Page generated in 0.056 seconds