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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.
541

Spatial and temporal alterations of gene expression in rice.

Plett, Darren Craig January 2008 (has links)
Two problems hampering efforts to produce salt-tolerant plants through constitutive expression of transgenes include: 1. Spatial control. Particular cell-types must respond specifically to salt stress to minimise the amount of Na⁺ delivered to the shoot; and, 2. Temporal control. Transgenes are typically expressed in plants at similar levels through time, irrespective of the stress encountered by the plant, which may exacerbate pleiotropic effects and means that, particularly in low-stress conditions, costly and/or detrimental metabolic processes may be active, thus reducing yield. To address these issues, Gateway® destination vector constructs were developed combining the GAL4 UAS (upstream activating sequence) with the ethanol-inducible gene expression system to drive inducible cell-specific expression of Na⁺ transporter transgenes (or to silence salt transporter transgenes inducibly and cell-specifically). Rice (Oryza sativa L. cv. Nipponbare) GAL4-GFP enhancer trap lines (Johnson et al., 2005: Plant J. 41, 779-789) that express GAL4 and GFP specifically in either the root epidermis or xylem parenchyma (and therefore ‘trap’ cell-type specific enhancer elements) were transformed with this GAL4 UAS – ethanol switch construct, thereby allowing both spatial and temporal control of transgenes. In preliminary experiments, the expression system successfully limited the expression of RFP to specific cell-types after induction with ethanol. Other genes expressed using this system include PpENA1, a Na⁺-extruding ATPase from the moss, Physcomitrella patens, and AtHKT1;1, a Na ⁺ transporter from Arabidopsis thaliana. The two enhancer trap rice lines were also transformed with the GAL4 UAS driving stable expression of AtHKT1;1 and PpENA1 specifically in root epidermal or xylem parenchyma cells. Expression of AtHKT1;1 in root epidermal cells reduced Na⁺ accumulation in the shoots, while expression in the root xylem parenchyma appeared to have little effect on shoot Na⁺ accumulation. Using cryo-scanning electron microscopy (SEM) X-ray microanalysis, the outer cells of the roots of the line expressing AtHKT1;1 in the epidermal cells were found to accumulate higher levels of Na⁺ than the parental enhancer trap line. Additionally, this line had decreased unidirectional ²²Na⁺ influx. Similar results were observed for plants expressing AtHKT1;1 driven by the CaMV 35S / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1325289 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008
542

Manipulation of a Large Magneto-Optical Trap:<br />application to Four-Wave Mixing

Gattobigio, Giovanni Luca 29 February 2008 (has links) (PDF)
Dans cette thèse, nous présentons une recherche expérimentale détaillée des lois caract érisant la taille et la densité atomique de grands pièges magnéto-optiques contenant typiquement 10^10 atomes. Il est bien connu que les interactions induites par laser, produites par la diffusion multiple, y constituent la limitation principale à l'obtention de densités atomiques élevées. Pour contourner cette limite, nous avons réalisé un piège magnéto-optique 'noir' combiné un piège dipolaire. Les forces de répulsion assistées par la lumière ont ainsi pu être considérablement réduites et une augmentation de près de deux ordres des grandeur sur le densité (jusqu'à 10^12 atm/cm^3) a été corrélativement observée. Nous avons proposé également un modèle qualitatif pour rendre compte de la densité atomique (et également pour la taille) o`u nous avons introduit les interactions mécaniques induites par les photons du laser repompeur quand son épaisseur optique devient importante. Ce travail fait partie d'un projet de recherche qui vise à terme à observer la localisation d'Anderson de la lumière dans des nuages d'atomes froids, mais pour laquelle des densités de l'ordre (10^13-10^14 atm/cm^3) sont requises. Pour des densités inférieures, des mécanismes de gain peuvent toutefois être mis à profit pour amplifier des modes pre-localisés. Nous avons, ainsi, mis en place une technique pompe-sonde pour la création d'un gain dans l'échantillon atomique. La configuration des pompes a autorisé l'observation du signal de mélange a quatre ondes. Une analyse détaillée de ses propriétés et de ses caractéristiques a été présentée. En particulier, une asymétrie rouge-bleu dans le spectre, pour des intensités élevées des faisceaux pompes, a été mise en évidence. Cette asymétrie a pu tre expliquée en tenant compte du regroupement des atomes dans les noeuds ou dans les ventres de l'onde stationnaire des faisceaux de pompe.
543

Vegetation and climate during Weichselian ice free intervals in northern Sweden : Interpretations from fossil and modern pollen records

Hättestrand, Martina January 2008 (has links)
<p>In this thesis the Weichselian history of northern Sweden is investigated, with emphasis on vegetation and climate during ice-free intervals. The main method used has been pollen analysis of sediments from pre-Late Weichselian landforms. To interpret fossil pollen assemblages, comparisons with modern pollen spectra were made. Modern pollen data were retrieved through monitoring of annual pollen deposition at seven sites in northern Sweden, from the boreal forest to above the present forest-line of birch. Eight years of pollen monitoring is described and put in a larger context through comparison with monitoring data from Iceland, Svalbard, Norway and Finland. A study of sediment cores from the Riipiharju esker shows evidence of two ice free phases during the Weichselian glacial; Tärendö I and Tärendö II. The Tärendö II ice free interval includes large climatic shifts, previously not recognized, from relatively warm conditions with <i>Betula</i> as the dominating pollen taxon to cold conditions with dominance of <i>Artemisia</i> and Gramineae and back to warmer conditions again. Correlation alternatives of the north Swedish ice free intervals Tärendö I and II are: 1/ Brörup (MIS 5c; c. 105-93 ka BP) and Odderade (MIS 5a; c. 85-74 ka BP), respectively, or 2/ Odderade and early Middle Weichselian time (MIS 3; c. 59-40 ka BP). Of these, alternative 2 is regarded as the most likely. Interstadial sediments deposited in a Veiki moraine plateau during downwasting of a pre-Late Weichselian ice sheet include only <i>Betula</i> dominant pollen spectra, showing that the climate during formation of the Veiki moraine was relatively warm. According to stratigraphical correlation there are three possible alternatives for Veiki moraine formation. Either it was formed during 1/ early Tärendö I, 2/ early Tärendö II, or 3/ late Tärendö II. Alternative 3 implies growth of an intermediate ice sheet reaching the eastern limit of Veiki moraine distribution during the cold phase of Tärendö II.</p>
544

Sedimentprovtagning av dagvattendammar som ett alternativ till flödesproportionell vattenprovtagning / Sediment sampling in stormwater ponds as an alternative to flow-weighted water sampling

Persson, Annika January 2010 (has links)
<p>Stormwater run-off from surfaces such as roads or rooftops is often polluted with heavy metals and nutrients. Many of these substances can cause great damage in biota if they end up in the recipient. In Sweden constructed wetlands and ponds for treatment of stormwater are frequently used, since research has shown that these treatment ponds are reducing stormwater pollution considerably to a low cost. The knowledge of these pollutant removal mechanisms and how follow-up and assessment of the ponds should be performed is still limited.</p><p>To determine the pollutant removal efficiency of the stormwater ponds it is recommended that flow-weighted water samples are collected from both the inflow and the outflow of the pond. This method demands considerable resources of time and money for installations and analysis. Alternative methods for assessing pollutant removal are requested, methods with lower costs but relevant results. This thesis is investigating whether sediment sampling could be such an alternative.</p><p>Sediment core samples were taken in four stormwater ponds where flow-weighted water sampling has been performed as well. This makes it possible to compare the two methods. A method of sampling recently sedimented material was also tried out by constructing and placing sediment traps on the pond floor. Analysis of concentration of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and phosphorus were carried out.</p><p>The results show i.e. that the concentrations of heavy metals and phosphorus in the pond sediments decrease as the distance from the pond inlet increase. Comparing the two methods shows that the results from the sediment sampling are in the same order of magnitude as the results from the water sampling. Consequently, the conclusion states that a well executed sediment sampling may be an alternative to flow-weighted water sampling.</p> / NOS dagvatten
545

Software Techniques for Distributed Shared Memory

Radovic, Zoran January 2005 (has links)
<p>In large multiprocessors, the access to shared memory is often nonuniform, and may vary as much as ten times for some distributed shared-memory architectures (DSMs). This dissertation identifies another important nonuniform property of DSM systems: <i>nonuniform communication architecture</i>, NUCA. High-end hardware-coherent machines built from large nodes, or from chip multiprocessors, are typical NUCA systems, since they have a lower penalty for reading recently written data from a neighbor's cache than from a remote cache. This dissertation identifies <i>node affinity</i> as an important property for scalable general-purpose locks. Several software-based hierarchical lock implementations exploiting NUCAs are presented and evaluated. NUCA-aware locks are shown to be almost twice as efficient for contended critical sections compared to traditional lock implementations.</p><p>The shared-memory “illusion”' provided by some large DSM systems may be implemented using either hardware, software or a combination thereof. A software-based implementation can enable cheap cluster hardware to be used, but typically suffers from poor and unpredictable performance characteristics.</p><p>This dissertation advocates a new software-hardware trade-off design point based on a new combination of techniques. The two low-level techniques, fine-grain deterministic coherence and synchronous protocol execution, as well as profile-guided protocol flexibility, are evaluated in isolation as well as in a combined setting using all-software implementations. Finally, a minimum of hardware trap support is suggested to further improve the performance of coherence protocols across cluster nodes. It is shown that all these techniques combined could result in a fairly stable performance on par with hardware-based coherence.</p>
546

Vegetation and climate during Weichselian ice free intervals in northern Sweden : Interpretations from fossil and modern pollen records

Hättestrand, Martina January 2008 (has links)
In this thesis the Weichselian history of northern Sweden is investigated, with emphasis on vegetation and climate during ice-free intervals. The main method used has been pollen analysis of sediments from pre-Late Weichselian landforms. To interpret fossil pollen assemblages, comparisons with modern pollen spectra were made. Modern pollen data were retrieved through monitoring of annual pollen deposition at seven sites in northern Sweden, from the boreal forest to above the present forest-line of birch. Eight years of pollen monitoring is described and put in a larger context through comparison with monitoring data from Iceland, Svalbard, Norway and Finland. A study of sediment cores from the Riipiharju esker shows evidence of two ice free phases during the Weichselian glacial; Tärendö I and Tärendö II. The Tärendö II ice free interval includes large climatic shifts, previously not recognized, from relatively warm conditions with Betula as the dominating pollen taxon to cold conditions with dominance of Artemisia and Gramineae and back to warmer conditions again. Correlation alternatives of the north Swedish ice free intervals Tärendö I and II are: 1/ Brörup (MIS 5c; c. 105-93 ka BP) and Odderade (MIS 5a; c. 85-74 ka BP), respectively, or 2/ Odderade and early Middle Weichselian time (MIS 3; c. 59-40 ka BP). Of these, alternative 2 is regarded as the most likely. Interstadial sediments deposited in a Veiki moraine plateau during downwasting of a pre-Late Weichselian ice sheet include only Betula dominant pollen spectra, showing that the climate during formation of the Veiki moraine was relatively warm. According to stratigraphical correlation there are three possible alternatives for Veiki moraine formation. Either it was formed during 1/ early Tärendö I, 2/ early Tärendö II, or 3/ late Tärendö II. Alternative 3 implies growth of an intermediate ice sheet reaching the eastern limit of Veiki moraine distribution during the cold phase of Tärendö II.
547

Crosstalk Between Activated Platelets and the Complement System

Hamad, Osama A. January 2010 (has links)
Several studies have shown that complement and thrombotic events co-exist. Platelets have been suspected to act as the bridge between the two cascade systems. To study the platelet-induced complement activation we developed a system in which platelets were activated by thrombin receptor activating peptide (TRAP) in platelet rich plasma (PRP) or whole blood anti-coagulated using the specific thrombin inhibitor, lepirudin. TRAP-activated platelets induced a fluid-phase complement activation measured as generation of C3a and sC5b-9, triggered by released chondroitin sulphate-A (CS-A) which interacted with C1q and activated the complement system through the classical pathway. Complement components C1q, C3, C4 and C9 were also shown to bind to TRAP-activated platelets but this binding did not seem to be due to a complement activation since blocking of complement activation at the C1q or C3 levels did not affect the binding of the complement proteins. The C3 which bound to activated platelets consisted of C3(H2O), indicating that bound C3 was not proteolytically activated. Binding of C1q was partially dependent on CS-A exposure on activated platelets. The abolished complement activation on the surface of activated platelets was suggested to be dependent on the involvement of several complement inhibitors. We confirmed the binding of C1INH and factor H to activated platelets. To this list we have added another potent complement inhibitor, C4BP. The binding of factor H and C4BP was shown to be dependent on exposure of CS-A on activated platelets. The physiological relevance of these reactions was reflected in an elevated expression of CD11b on leukocytes, and increased generation of platelet-leukocyte complexes. The platelets were involved in these events by at least two different mechanisms; generation of C5a which activated leukocytes and binding of C3(H2O)/iC3(H2O), a ligand to the intergrin CD11b/CD18 on their surface. These mechanisms add further to the understanding of how platelets interact with the complement system and will help us to understand the role of the complement system in cardiovascular disease and thrombotic conditions. / Platelet Mediated Complement Activation
548

ニホンザルの洞窟利用と化石化過程 (予案)

Senokuchi, Yoshitaka, Abe, Yuji, Kashiwagi, Kenji, 瀬之口, 祥孝, 阿部, 勇治, 柏木, 健司 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
549

Synergy of decay spectroscopy and mass spectrometry for the study of exotic nuclides

Stanja, Juliane 04 July 2013 (has links) (PDF)
With only two ingredients, atomic nuclei exhibit a rich structure depending on the ordering of the different proton- and neutron-occupied states. This ordering can give rise to excited states with exceptionally long half-lives, also known as isomers, especially near shell closures. On-line mass spectrometry can often be compromised by the existence of such states that may even be produced in higher proportion than the ground state. This thesis presents the first results obtained from a nuclear spectroscopy setup coupled with the high-resolution Penning-trap mass spectrometer ISOLTRAP, at CERN’s radioactive ion beam facility ISOLDE. The isomerism in the neutron-deficient thallium isotopes was investigated. The data on 184,190,193−195 Tl allow an improvement of existing mass values as well as a mass-spin-state assignment in 190,193,194 Tl. Due to the presence of the ground and isomeric state for 194 Tl the excitation energy of the latter was determined for the first time experimentally. Systematic trends in the vicinity of the Z = 82 shell closure have been discussed.
550

Sedimentprovtagning av dagvattendammar som ett alternativ till flödesproportionell vattenprovtagning / Sediment sampling in stormwater ponds as an alternative to flow-weighted water sampling

Persson, Annika January 2010 (has links)
Stormwater run-off from surfaces such as roads or rooftops is often polluted with heavy metals and nutrients. Many of these substances can cause great damage in biota if they end up in the recipient. In Sweden constructed wetlands and ponds for treatment of stormwater are frequently used, since research has shown that these treatment ponds are reducing stormwater pollution considerably to a low cost. The knowledge of these pollutant removal mechanisms and how follow-up and assessment of the ponds should be performed is still limited. To determine the pollutant removal efficiency of the stormwater ponds it is recommended that flow-weighted water samples are collected from both the inflow and the outflow of the pond. This method demands considerable resources of time and money for installations and analysis. Alternative methods for assessing pollutant removal are requested, methods with lower costs but relevant results. This thesis is investigating whether sediment sampling could be such an alternative. Sediment core samples were taken in four stormwater ponds where flow-weighted water sampling has been performed as well. This makes it possible to compare the two methods. A method of sampling recently sedimented material was also tried out by constructing and placing sediment traps on the pond floor. Analysis of concentration of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and phosphorus were carried out. The results show i.e. that the concentrations of heavy metals and phosphorus in the pond sediments decrease as the distance from the pond inlet increase. Comparing the two methods shows that the results from the sediment sampling are in the same order of magnitude as the results from the water sampling. Consequently, the conclusion states that a well executed sediment sampling may be an alternative to flow-weighted water sampling. / NOS dagvatten

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