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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.
341

Relative contribution of land use change and climate variability on discharge of upper Mara River, Kenya

Mwangi, Hosea M., Julich, Stefan, Patil, Sopan D., McDonald, Morag A., Feger, Karl-Heinz 27 July 2017 (has links)
Study region Nyangores River watershed, headwater catchment of Mara River basin in Kenya. Study focus Climate variability and human activities are the main drivers of change of watershed hydrology. The contribution of climate variability and land use change to change in streamflow of Nyangores River, was investigated. Mann Kendall and sequential Mann Kendall tests were used to investigate the presence and breakpoint of a trend in discharge data (1965–2007) respectively. The Budyko framework was used to separate the respective contribution of drivers to change in discharge. Future response of the watershed to climate change was predicted using the runoff sensitivity equation developed. New hydrological insights for the region There was a significant increasing trend in the discharge with a breakpoint in 1977. Land use change was found to be the main driver of change in discharge accounting for 97.5% of the change. Climate variability only caused a net increase of the remaining 2.5% of the change; which was caused by counter impacts on discharge of increase in rainfall (increased discharge by 24%) and increase in potential evapotranspiration (decreased discharge by 21.5%). Climate change was predicted to cause a moderate 16% and 15% increase in streamflow in the next 20 and 50 years respectively. Change in discharge was specifically attributed to deforestation at the headwaters of the watershed.
342

Mineral-Based Coating of Plasma-Treated Carbon Fibre Rovings for Carbon Concrete Composites with Enhanced Mechanical Performance

Schneider, Kai, Lieboldt, Matthias, Liebscher, Marco, Fröhlich, Maik, Hempel, Simone, Butler, Marko, Schröfl, Christof, Mechtcherine, Viktor 27 July 2017 (has links)
Surfaces of carbon fibre roving were modified by means of a low temperature plasma treatment to improve their bonding with mineral fines; the latter serving as an inorganic fibre coating for the improved mechanical performance of carbon reinforcement in concrete matrices. Variation of the plasma conditions, such as gas composition and treatment time, was accomplished to establish polar groups on the carbon fibres prior to contact with the suspension of mineral particles in water. Subsequently, the rovings were implemented in a fine concrete matrix and their pull-out performance was assessed. Every plasma treatment resulted in increased pull-out forces in comparison to the reference samples without plasma treatment, indicating a better bonding between the mineral coating material and the carbon fibres. Significant differences were found, depending on gas composition and treatment time. Microscopic investigations showed that the samples with the highest pull-out force exhibited carbon fibre surfaces with the largest areas of hydration products grown on them. Additionally, the coating material ingresses into the multifilament roving in these specimens, leading to better force transfer between individual carbon filaments and between the entire roving and surrounding matrix, thus explaining the superior mechanical performance of the specimens containing appropriately plasma-treated carbon roving.
343

The peripheral and Central Humphrey visual field – morphological changes during aging

Rutkowski, Paul, May, Christian Albrecht 09 November 2017 (has links)
Background: To define age-related changes in the visual field by comparing 'standard' central and unique peripheral visual field measurements in healthy volunteers. Methods: In a single center, retrospective, Cross-sectional, observational study, 20 volunteers with no retinal diseases or risk factors, ranging in age between 30 and 94 years (four age groups: 30’s, 50’s, 70’s, 90’s) were measured in one eye (preferentially the right one) using a Humphrey visual field 24–2 and 60–4. Results: While the central visual field remained relatively well preserved during aging showing only a mild reduction in sensitivity, a profound loss of the peripheral visual field was observed beginning in the fifth decade of life and decreasing continuously up to the 90ies. Conclusions: The peripheral visual field declined substantially from the 4th decade onward while the central visual field remained quite stable.
344

Type-D Personality in Unemployed Subjects: Prevalence, Self-Efficacy and Heart Rate Variability/Autonomic Response

Petrowski, Katja, Wendt, Katharina, Wichmann, Susann, Siepmann, Martin 09 November 2017 (has links)
Background: Unemployment may impair mental and physical health. The influencing factors causing such negative effects are relevant from an individual and public health perspective. The personality as one possible influencing factor was discussed. This study investigated the prevalence of the type-D personality in an unemployed population and its connections to socio-demographic, psychological and heart rate variability (HRV) parameters. Methods: A questionnaire set including socio-demographics, type-D scale (DS14), Complaint list (BL), Beck-Depression-Inventory II (BDI-II) and the General Self-Efficacy Scale (GSE) was handed out to 203 unemployed individuals [126 females, mean age ± SD: 42.36 ± 11.08]. For HRV assessment (RMSSD), a subsample of 83 participants [50 females, median age ± IQR: 47.00 ± 17.00] passed the “stress-tests” (timed breathing, d2-attention-stress-test, math test) while heart frequency (HF) was acquired via the Stressball software (BioSign GmbH, Ottenhofen, Germany). Results: 53% of the unemployed had a type-D personality. Compared to non-type-D individuals, type-D individuals had rarely children and by trend a lower educational level; they showed significantly higher scores in the BDI-II and lower scores in the GSE and BL. No differences were observed in mean HF or RMSSD during all the stress-tests. Conclusion: The HRV of individuals with a type-D personality is no worse than that of individuals without a type-D personality. Type-D personality was significantly associated with negative health effects regarding depressiveness, self-efficacy and physical complaints. Our main findings implicate that the DS14 could serve as a short and reliable screening instrument to select concerned unemployed individuals who might be at risk for negative health effects for adequate intervention.
345

The relation between human hair follicle density and touch perception

Bendas, Johanna, Jönsson, Emma H., Weidner, Kerstin, Wessberg, Johan, Olausson, Håkan, Backlund Wasling, Helena, Croy, Ilona 10 November 2017 (has links)
Unmyelinated low threshold C-tactile fibers moderate pleasant aspects of touch. These fibers respond optimally to stroking stimulation of the skin with slow velocities (1–10 cm/s). Low threshold mechanoreceptors are arranged around hair follicles in rodent skin. If valid also in humans, hair follicle density (HFD) may relate to the perceived pleasantness of stroking tactile stimulation. We conducted two studies that examined the relation between HFD and affective touch perception in humans. In total, 138 healthy volunteers were stroked on the forearm and rated the pleasantness and intensity. Stimulation was performed by a robotic tactile stimulator delivering C-tactile optimal (1, 3, 10 cm/s) and non-optimal (0.1, 0.3, 30 cm/s) stroking velocities. Additionally, a measure of discriminative touch was applied in study 2. HFD of the same forearm was determined using the Cyanoacrylate Skin Stripping Method (CSSM), which we validated in a pretest. Women had higher HFD than men, which was explained by body size and weight. Furthermore, women rated affective touch stimuli as more pleasant and had higher tactile acuity. Depilation did not affect touch perception. A weak relationship was found between the C-tactile specific aspects of affective touch perception and HFD, and the hypothesis of HFD relating to pleasant aspects of stroking only received weak support.
346

Characterization of acoustic and mechanical properties of common tropical woods used in classical guitars

Sproßmann, Robert, Zauer, Mario, Wagenführ, André 14 November 2017 (has links)
There is a need of substitution woods for the use in musical instruments because of the limited availabil-ity of some commonly used tropical tonewoods. Before substitutions can be found, it is necessary to knowabout the required properties. Hence, in this paper acoustical, mechanical and physical properties of fourcommon tropical hardwoods (Indian rosewood, ziricote, African blackwood and ebony) were determinedbecause there are less literature values for some properties available, e.g. internal friction, hardness orswelling behaviour. The acoustic properties were determined by means of experimental modal analysis,the mechanical properties by means of static bending tests and tests of the Brinell hardness. For the swel-ling behaviour the volume swelling and also the differential swelling coefficients were determined. Withthe results it is possible to look for new ‘tonewoods’ or to specifically modified woods, e.g. thermally trea-ted wood, to substitute tropical wood species.
347

Clonal competition in BcrAbl-driven leukemia: how transplantations can accelerate clonal conversion

Cornils, Kerstin, Thielecke, Lars, Winkelmann, Doreen, Aranyossy, Tim, Lesche, Mathias, Dahl, Andreas, Roeder, Ingo, Fehse, Boris, Glauche, Ingmar 15 November 2017 (has links)
Background: Clonal competition in cancer describes the process in which the progeny of a cell clone supersedes or succumbs to other competing clones due to differences in their functional characteristics, mostly based on subsequently acquired mutations. Even though the patterns of those mutations are well explored in many tumors, the dynamical process of clonal selection is underexposed. Methods: We studied the dynamics of clonal competition in a BcrAbl-induced leukemia using a γ-retroviral vector library encoding the oncogene in conjunction with genetic barcodes. To this end, we studied the growth dynamics of transduced cells on the clonal level both in vitro and in vivo in transplanted mice. Results: While we detected moderate changes in clonal abundancies in vitro, we observed monoclonal leukemias in 6/30 mice after transplantation, which intriguingly were caused by only two different BcrAbl clones. To analyze the success of these clones, we applied a mathematical model of hematopoietic tissue maintenance, which indicated that a differential engraftment capacity of these two dominant clones provides a possible explanation of our observations. These findings were further supported by additional transplantation experiments and increased BcrAbl transcript levels in both clones. Conclusion: Our findings show that clonal competition is not an absolute process based on mutations, but highly dependent on selection mechanisms in a given environmental context.
348

Effects of perceptions of care, medical advice, and hospital quality on patient satisfaction after primary total knee replacement: A cross-sectional study

Schaal, Tom, Schoenfelder, Tonio, Klewer, Joerg, Kugler, Joachim 10 November 2017 (has links)
Introduction: The increase in the number of patients presenting with osteoarthritis in the past decade has led to a 32% increase in knee replacement surgeries designed to reduce restrictions on patient movement and improve their quality of life. Patient satisfaction is becoming an increasingly important indicator of quality of care. This study was designed to identify predictors of various service components in the treatment process and hospital key performance indicators significantly associated with patient satisfaction. Materials and methods: A multicenter cross-sectional study was conducted with 856 patients having their primary total knee replacements at 41 hospitals. Patient satisfaction was queried via a validated, multidimensional questionnaire mainly using a six-point scale. In addition to bivariate calculations, patient satisfaction was the dependent variable in a binary logistic regression model. Results: The bivariate analysis showed a strong association between satisfaction and sex (male or female), the patients’ health before admission, and the length of stay. The number of cases treated at each hospital did not reveal any impact on satisfaction. The multivariate analysis identified three predictors associated with overall satisfaction. The strongest factor was the treatment outcome and the weakest was the quality of food. It became apparent that the statutory procedure minimums were not being met. Conclusions: The relevant factors influencing patient satisfaction were partially the same as previous study results and allowed more detailed conclusions. The results provide suggestions across hospitals that could help health care providers better meet needs of patients after knee arthroplasties.
349

Site-Specific Variations in Bone Mineral Density under Systemic Conditions Inducing Osteoporosis in Minipigs

Schulz, Matthias C., Kowald, Jan, Estenfelder, Sven, Jung, Roland, Kuhlisch, Eberhard, Eckelt, Uwe, Mai, Ronald, Hofbauer, Lorenz C., Stroszczynski, Christian, Stadlinger, Bernd 16 November 2017 (has links)
Osteoporosis is a systemic bone disease with an increasing prevalence in the elderly population. There is conflicting opinion about whether osteoporosis affects the alveolar bone of the jaws and whether it poses a risk to the osseointegration of dental implants. The aim of the present study was to evaluate the effects of systemic glucocorticoid administration on the jaw bone density of minipigs. Thirty-seven adult female minipigs were randomly divided into two groups. Quantitative computed tomography (QCT) was used to assess bone mineral density BMD of the lumbar spine as well as the mandible and maxilla, and blood was drawn. One group of minipigs initially received 1.0 mg prednisolone per kg body weight daily for 2 months. The dose was tapered to 0.5 mg per kg body weight per day thereafter. The animals in the other group served as controls and received placebo. QCT and blood analysis were repeated after 6 and 9 months. BMD was compared between the two groups by measuring Hounsfield units, and serum levels of several bone metabolic markers were also assessed. A decrease in BMD was observed in the jaws from baseline to 9 months. This was more pronounced in the prednisolone group. Statistically significant differences were reached for the mandible (p < 0.001) and the maxilla (p < 0.001). The administration of glucocorticoids reduced the BMD in the jaws of minipigs. The described model shows promise in the evaluation of osseointegration of dental implants in bone that is compromised by osteoporosis.
350

Health utilities for chronic low back pain

Seidler, Anna Lene, Rethberg, Constanze, Schmitt, Jochen, Nienhaus, Albert, Seidler, Andreas 07 December 2017 (has links)
Background Chronic low back pain (LBP) is a common health problem, with a large potential for primary prevention. Health utilities (HU) reflect which proportion of their expected remaining life time individuals would hypothetically trade to be alleviated of a health condition of interest. A value of 0 means “prefer to die immediately”, a value of 1 means “not willing to trade any life time”. The aim of this cross-sectional study was to assess HU for LBP patients and for healthy participants and to examine whether HU for LBP are useful indicators to substantiate preventive and therapeutic decision making. Methods Healthy participants (n = 126) and LBP patients (n = 32) were recruited mainly among the employees of a tertiary care hospital in Germany. Standardized LBP scenarios were presented to all participants and HU values were assessed using the time-trade-off method. Results Median HU for LBP were 0.90 (IQR 0.31) for participants and 0.93 (IQR 0.10) for LBP patients. Measurements were consistent across illness severity ratings with HU and with a visual analogue scale (VAS); in the healthy sample the intraclass correlation coefficient (ICC) was 0.61 (95% CI 0.23–1.00, F(1125) = 190, p < .001), in the patient sample the ICC was 0.66 (95% CI = 0.24–1.00, F(1,31) = 62, p < .001). 8% of participants reported HU of 1. There was no statistically significant relation between HU and age, income, or gender. Conclusion On average, participants chose a 7 to 10% shorter life expectancy to avoid LBP, but almost 1 in 10 participants were not willing to trade any life years. The results indicate a certain stability of HU due to the comparability of HU ratings across patients and healthy participants, the measurement consistency when comparing VAS and HU ratings, and the lack of association between demographic variables and HU. This underlines the usefulness of HU for measuring illness severity in comparative health economics evaluations of preventive and therapeutic measures that address chronic LBP or other pain-characterized diseases. Future studies should focus on different LBP intensities and derive stratified HU that reflect the distribution of pain intensity in the population.

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