• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 778
  • 228
  • 132
  • 83
  • 54
  • 45
  • 42
  • 37
  • 26
  • 22
  • 11
  • 8
  • 5
  • 5
  • 3
  • Tagged with
  • 1881
  • 663
  • 367
  • 342
  • 233
  • 195
  • 185
  • 152
  • 150
  • 135
  • 133
  • 127
  • 121
  • 120
  • 100
  • 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.
51

The surgeon´s third hand

Hoffman, Anton January 2015 (has links)
The biggest technical development within the field of surgery is focused on minimal invasive procedures. With new robot assisted solutions can the surgeons work more precise with a great level of flexibility. The work is nevertheless connected to a long set-up time and big costs. This project, based on pure user studies and in-depth surgery observations, discovers a possibility to, in a cost efficient way, offer robot benefits to an open surgery scenario. With a minimal effort can the surgeon merge the suggested product concept into their regular workflow and enhance the stability in their movements, get improved vision and aid in holding tissue in static positions.
52

Automated algorithms for detection of stroke distance from Doppler ultrasound signals

Warner, Margaret January 1999 (has links)
No description available.
53

Invasive bacteria induce cellular stress that alters the cytoplasmic dynamics of the SMN complex

Ling, Arthur 13 September 2011 (has links)
The course of pathogenic bacterial infection is dependent on the interactions between the host immune response and the bacterial virulence mechanisms. Our lab previously discovered that the Survival of Motor Neuron (SMN) protein complex undergoes a change in subcellular localization during infection with invasive Shigella bacteria, forming novel cytoplasmic aggregates called "U bodies". Similar results were obtained with other intracellular bacterial pathogens suggesting that these U bodies are a fundamental entity in microbial pathogenesis. Notably, the SMN complex normally plays a key role in the assembly of the spliceosomal U snRNA. We have shown during infection that there are changes in U snRNA maturation and splicing patterns. Importantly, we have found that U bodies are downstream of a stress pathway involving the stress-inducible ATF3 protein. Altogether, intracellular bacterial infection induces novel cellular stress pathways that disrupt normal SMN complex function and leads to changes in U snRNA associated functions.
54

Root Water Uptake and Soil Water Dynamics in a Karst Savanna on the Edwards Plateau, TX

Tokumoto, Ieyasu 03 October 2013 (has links)
Woody plants are encroaching into a karst savanna on the Edwards Plateau in central Texas, but their impact on hydrology is unclear because of high variability in soil depth and uncertainties about shallow and deep root contributions to water uptake, and water dynamics in rocky soil. The overall objectives of this study are to quantify contributions of shallow and deep roots to water uptake, and to quantify the impact of rock on soil hydraulic properties and water storage. A study was conducted in a karst savanna with ~50% woody cover to monitor spatial and temporal variations in soil moisture and root water uptake with neutron probe and time-domain reflectometry measurements. Bulk density was measured using gamma densitometry. Measurements were made to a depth of 1.6 m in a 25 m  25 m grid (5 m node spacing). The results showed that rock created high spatial variability in water storage. Water storage capacity in the measurement grid ranged from 185 to 401 mm, and coupled with heterogeneous distribution of trees led to high spatial variability in root water uptake. Most of the water uptake came from the upper 1 m of the soil profile, but 10% came from below 1.6 m. This indicated that roots had access to water stored within the bedrock, possibly in soil pockets. Statistical analysis showed that spatial distribution of θ was significantly correlated with rock distribution in the profile. Laboratory evaporation measurements showed that Small volume fractions of rock can increase evaporation from soils by slowing upward movement of water, thereby maintaining capillary connectivity to the surface for a longer period of time. Two simulation models, van Genuchten (VG) and Durner, were compared with the data from evaporation experiments. Results showed that the Durner model was more appropriate than the VG model for describing water retention and hydraulic conductivity of rocky soils.
55

Changes to the cytoskeleton and cell wall underlie invasive hyphal growth.

Walker, Sophie January 2004 (has links)
Tip growth is a form of cellular expansion characteristic of fungal hyphae and some types of plant cells. Currently there is no unified model that satisfactorily describes this in hyphal species. Traditionally turgor has been considered an essential driving force behind cell expansion. In recent years this hypothesis has been challenged by evidence that in some species tip growth can occur despite the absence of measurable hydrostatic pressure. There are currently two contentious theories of hyphal extension. These are the turgor-driven model and the amoeboid-movement theory. Though the essential mechanism underlying cell growth differs between these theories, the actin cytoskeleton is considered important in both. It has been suggested that both the turgor-driven and amoeboid-like modes of growth could occur depending on the whether the hyphae are growing invasively or non-invasively respectively (Money, 1990). It has also been proposed that both modes may occur within the same mycelium (Garrill, 2000). Two distinct patterns of actin have been identified in the hyphal tips of oomycetes. This has lead to the hypothesis that two different mechanisms of apical extension may be employed by some hyphal organisms. During the course of this thesis, actin deplete zones have been observed in a significantly higher number of invasive compared to non-invasive hyphae of the oomycete Achlya bisexualis. Furthermore the difference between burst pressures was found to be lower in invasive hyphae compared to non-invasive hyphae suggestive of a weaker cell wall. A lack of significant difference in turgor pressures between the invasive and non-invasive hyphae of this organism suggests that the deplete zone and weaker wall plays a functional role in enabling hyphae to penetrate substrate. Fractal analysis of mycelial colonies shows that the variation in agar concentration and therefore substrate solidity has a significant effect on mycelial morphology. This is most likely due to an effect at the cellular level. The results of the experiments carried out during the course of this thesis provide the basis for future work towards elucidating the mechanisms of hyphal extension.
56

Riparian woody plant diversity, composition, and structure across an urban-rural land use gradient in the Piedmont of Georgia, US

Burton, Michele Lee, Samuelson, Lisa J. January 2006 (has links) (PDF)
Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.
57

Investigating distribution and treatments for effective mechanical and herbicide application for controlling oriental bittersweet (Celastrus orbiculatus thunb.) vines in an Appalachian hardwood forest

Lynch, Amanda L. January 2009 (has links)
Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains vii, 82 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references.
58

Rising atmospheric CO² concentrations and plant invasion in the northern mixed-grass prairie an ecophysiological perspective /

Schomp. Jennifer M. January 2007 (has links)
Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 10, 2009). Includes bibliographical references.
59

Sub-pixel remote sensing for mapping and modelling invasive tamarix : a case study in West Texas, 1993-2005 /

Silván-Cárdenas, José L. January 1900 (has links)
Thesis (Ph. D.)--Texas State University--San Marcos, 2009. / Vita. Appendices: leaves 157-171. Includes bibliographical references (leaves 172-185). Also available on microfilm.
60

Historical legacies, competition and dispersal control patterns of invasion by a non-native grass, Microstegium vimineum Trin. (A. Camus)

Schramm, Jonathon William. January 2008 (has links)
Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Ecology and Evolution." Includes bibliographical references (p. 148-159).

Page generated in 0.0523 seconds