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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.
231

Forest Management Approaches for Coping with the Uncertainty of Climate Change: Trade-Offs in Service Provisioning and Adaptability

Wagner, Sven, Nocentini, Susanna, Huth, Franka, Hoogstra-Klein, Marjanke 01 August 2014 (has links)
The issue of rapid change in environmental conditions under which ecosystem processes and human interventions will take place in the future is relatively new to forestry, whereas the provision of ecosystem services, e.g., timber or fresh water, is at the very heart of the original concept of forest management. Forest managers have developed ambitious deterministic approaches to provide the services demanded, and thus the use of deterministic approaches for adapting to climate change seem to be a logical continuation. However, as uncertainty about the intensity of climate change is high, forest managers need to answer this uncertainty conceptually. One may envision an indeterministic approach to cope with this uncertainty; but how the services will be provided in such a concept remains unclear. This article aims to explore the fundamental aspects of both deterministic and indeterministic approaches used in forestry to cope with climate change, and thereby point out trade-offs in service provisioning and adaptability. A forest owner needs to be able to anticipate these trade-offs in order to make decisions towards sustainable forest management under climate change.
232

Physical Properties of Polyamide-12 versus PMMA Denture Base Material

Wieckiewicz, Mieszko, Opitz, Volker, Richter, Gert, Böning, Klaus W. 07 July 2014 (has links)
Objectives. Polyamide-12 (PA) is a flexible material suited for denture bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity. Methods. PA specimens (Valplast) of 40 × 10 × 2mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine (n = 10) were measured using the CIE L*a*b color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, n = 15) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling (n = 10). Results. Tukey’s HSD test (P < 0.05) revealed statistically significant color changes of PA in red wine (ΔE = 4.27 after 12 days, EΔE = 6.90 after 12 days) and coffee (ΔE = 3.93 after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845MPa and not affected by thermocycling (Tukey’s HSD test, P > 0.81). Dry specimens showed significantly decreased elasticity (P < 0.001). Mean surface roughness (PA 0.20 μm, PMMA 0.28 μm) did not change significantly after thermocycling or storage (Mann-Whitney U-test, 0.16 < P < 0.65). Significance. PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.
233

Multipose Binding in Molecular Docking

Atkovska, Kalina, Samsonov, Sergey A., Paszkowski-Rogacz, Maciej, Pisabarro, M. Teresa 09 July 2014 (has links)
Molecular docking has been extensively applied in virtual screening of small molecule libraries for lead identification and optimization. A necessary prerequisite for successful differentiation between active and non-active ligands is the accurate prediction of their binding affinities in the complex by use of docking scoring functions. However, many studies have shown rather poor correlations between docking scores and experimental binding affinities. Our work aimed to improve this correlation by implementing a multipose binding concept in the docking scoring scheme. Multipose binding, i.e., the property of certain protein-ligand complexes to exhibit different ligand binding modes, has been shown to occur in nature for a variety of molecules. We conducted a high-throughput docking study and implemented multipose binding in the scoring procedure by considering multiple docking solutions in binding affinity prediction. In general, improvement of the agreement between docking scores and experimental data was observed, and this was most pronounced in complexes with large and flexible ligands and high binding affinities. Further developments of the selection criteria for docking solutions for each individual complex are still necessary for a general utilization of the multipose binding concept for accurate binding affinity prediction by molecular docking.
234

Glycosaminoglycan Monosaccharide Blocks Analysis by Quantum Mechanics, Molecular Dynamics, and Nuclear Magnetic Resonance

Samsonov, Sergey A., Theisgen, Stephan, Riemer, Thomas, Huster, Daniel, Pisabarro, M. Teresa 09 July 2014 (has links)
Glycosaminoglycans (GAGs) play an important role in many biological processes in the extracellular matrix. In a theoretical approach, structures of monosaccharide building blocks of natural GAGs and their sulfated derivatives were optimized by a B3LYP6311ppdd//B3LYP/ 6-31+G(d) method. The dependence of the observed conformational properties on the applied methodology is described. NMR chemical shifts and proton-proton spin-spin coupling constants were calculated using the GIAO approach and analyzed in terms of the method's accuracy and sensitivity towards the influence of sulfation, O1-methylation, conformations of sugar ring, and ω dihedral angle. The net sulfation of the monosaccharides was found to be correlated with the 1H chemical shifts in the methyl group of the N-acetylated saccharides both theoretically and experimentally. The ω dihedral angle conformation populations of free monosaccharides and monosaccharide blocks within polymeric GAG molecules were calculated by a molecular dynamics approach using the GLYCAM06 force field and compared with the available NMR and quantum mechanical data. Qualitative trends for the impact of sulfation and ring conformation on the chemical shifts and proton-proton spin-spin coupling constants were obtained and discussed in terms of the potential and limitations of the computational methodology used to be complementary to NMR experiments and to assist in experimental data assignment.
235

Fear Processing in Dental Phobia during Crossmodal Symptom Provocation: An fMRI Study

Hilbert, Kevin, Evens, Ricarda, Maslowski, Nina Isabel, Wittchen, Hans-Ulrich, Lüken, Ulrike 09 July 2014 (has links)
While previous studies successfully identified the core neural substrates of the animal subtype of specific phobia, only few and inconsistent research is available for dental phobia. These findings might partly relate to the fact that, typically, visual stimuli were employed. The current study aimed to investigate the influence of stimulus modality on neural fear processing in dental phobia. Thirteen dental phobics (DP) and thirteen healthy controls (HC) attended a block-design functional magnetic resonance imaging (fMRI) symptom provocation paradigm encompassing both visual and auditory stimuli. Drill sounds and matched neutral sinus tones served as auditory stimuli and dentist scenes and matched neutral videos as visual stimuli. Group comparisons showed increased activation in the insula, anterior cingulate cortex, orbitofrontal cortex, and thalamus in DP compared to HC during auditory but not visual stimulation. On the contrary, no differential autonomic reactions were observed in DP. Present results are largely comparable to brain areas identified in animal phobia, but also point towards a potential downregulation of autonomic outflow by neural fear circuits in this disorder. Findings enlarge our knowledge about neural correlates of dental phobia and may help to understand the neural underpinnings of the clinical and physiological characteristics of the disorder.
236

The role of psychosocial working conditions on burnout and its core component emotional exhaustion – a systematic review

Seidler, Andreas, Thinschmidt, Marleen, Deckert, Stefanie, Then, Francisca, Hegewald, Janice, Nieuwenhuijsen, Karen, Riedel-Helle, Steffi G. 14 July 2014 (has links)
Aims: To analyze the association between psychosocial working conditions and burnout and its core component emotional exhaustion, a systematic literature review was undertaken including cohort studies, case–control studies, and randomized controlled trials. Methods: The literature search in Medline and PsycInfo was based on a defined search string and strict exclusion and inclusion criteria. Evaluation of the 5,599 initially identified search hits by two independent reviewers and a detailed quality assessment resulted in six methodologically adequate cohort studies considering the relationship between psychosocial working conditions and burnout (one study) as well as the burnout core component emotional exhaustion (five studies). Results: The results of our systematic review point to a relationship between psychosocial working conditions and the development of emotional exhaustion/burnout. Particularly high job demands seem to play a role in the development of emotional exhaustion. However, strong intercorrelations between workplace factors, as a matter of principle, make the identification of a single psychosocial workplace factor (being associated with an especially high or low risk of burnout) difficult. Conclusions: Multidimensional approaches including reduction of work demands, enhancement of decision latitude and improving the social climate might be promising for preventing burnout and emotional exhaustion. However, methodologically adequate intervention studies are urgently needed to prove the effectiveness of workplace interventions.
237

How Does a Single Cell Know When the Liver Has Reached Its Correct Size?

Hohmann, Nadine, Weiwei, Wei, Dahmen, Uta, Dirsch, Olaf, Deutsch, Andreas, Voss-Böhme, Anja 14 July 2014 (has links)
The liver is a multi-functional organ that regulates major physiological processes and that possesses a remarkable regeneration capacity. After loss of functional liver mass the liver grows back to its original, individual size through hepatocyte proliferation and apoptosis. How does a single hepatocyte ‘know’ when the organ has grown to its final size? This work considers the initial growth phase of liver regeneration after partial hepatectomy in which the mass is restored. There are strong and valid arguments that the trigger of proliferation after partial hepatectomy is mediated through the portal blood flow. It remains unclear, if either or both the concentration of metabolites in the blood or the shear stress are crucial to hepatocyte proliferation and liver size control. A cell-based mathematical model is developed that helps discriminate the effects of these two potential triggers. Analysis of the mathematical model shows that a metabolic load and a hemodynamical hypothesis imply different feedback mechanisms at the cellular scale. The predictions of the developed mathematical model are compared to experimental data in rats. The assumption that hepatocytes are able to buffer the metabolic load leads to a robustness against short-term fluctuations of the trigger which can not be achieved with a purely hemodynamical trigger.
238

Participant adherence to the Internet-based prevention program StudentBodies™ for eating disorders — A review

Beintner, Ina, Jacobi, Corinna, Taylor, C. Barr 14 July 2014 (has links)
Study and treatment dropout and adherence represent particular challenges in studies on Internet-based interventions. However, systematic investigations of the relationship between study, intervention and patient characteristics, participation, and intervention outcomes in online-prevention are scarce. A review of participation in trials investigating a cognitive-behavioral, Internet-based, 8-week prevention program (StudentBodies™) for eating disorders, moderators of participation, and the impact of participation on the relationship of outcome moderators and outcomes was performed. Seven US and three German studies with a total of N = 1059 female participants were included. Two of the U.S. and one of the German trials explicitly addressed high risk samples in a selective prevention approach. Across studies, dropout rates ranged from 3% to 26%. The women who participated in the trials accessed on average between 49% and 83% of the assigned intervention content. None of the study characteristics (universal vs. selective prevention, incentives, country, participants' age) predicted adherence or study dropout. After adjusting for adherence, intervention outcomes (EDI Drive for Thinness and EDI Bulimia) were only moderated by participant's age, with smaller effects in one sample of adolescent girls. Adherence to StudentBodies™ proved to be high across a number of trials, settings and countries. These findings are promising, but it is likely that adherence will be distinctly lower in the general public than in research settings, and intervention effects will turn out smaller. However, the intervention is readily available at minimal cost per participant, and the public health impact may still be notable.
239

The effect of body posture on cognitive performance: a question of sleep quality

Mühlhan, Markus, Marxen, Michael, Landsiedel, Julia, Malberg, Hagen, Zaunseder, Sebastian 14 July 2014 (has links)
Nearly all functional magnetic resonance imaging (fMRI) studies are conducted in the supine body posture, which has been discussed as a potential confounder of such examinations. The literature suggests that cognitive functions, such as problem solving or perception, differ between supine and upright postures. However, the effect of posture on many cognitive functions is still unknown. Therefore, the aim of the present study was to investigate the effects of body posture (supine vs. sitting) on one of the most frequently used paradigms in the cognitive sciences: the N-back working memory paradigm. Twenty-two subjects were investigated in a randomized within-subject design. Subjects performed the N-back task on two consecutive days in either the supine or the upright posture. Subjective sleep quality and chronic stress were recorded as covariates. Furthermore, changes in mood dimensions and heart rate variability (HRV) were assessed during the experiment. Results indicate that the quality of sleep strongly affects reaction times when subjects performed a working memory task in a supine posture. These effects, however, could not be observed in the sitting position. The findings can be explained by HRV parameters that indicated differences in autonomic regulation in the upright vs. the supine posture. The finding is of particular relevance for fMRI group comparisons when group differences in sleep quality cannot be ruled out.
240

BMI, physical inactivity, cigarette and alcohol consumption in female nursing students: a 5-year comparison

Lehmann, Franziska, von Lindeman, Katharina, Klewer, Jörg, Kugler, Joachim 14 July 2014 (has links)
Background: Nursing staff are often involved in counseling patients with regard to health behavior. Although care promoting healthy lifestyle choices is included in the curriculum of nursing students in Germany, several studies of nursing students have reported a high prevalence of unhealthy behavior. This paper focuses on the behavior of female nursing students with regard to body mass index (BMI), physical activity, and cigarette and alcohol consumption. It describes trends through the comparison of results from 2008 and 2013. Methods: Data was collected in two waves at a regional medical training college. First, 301 nursing students were asked to fill out a 12 page questionnaire on health behavior in 2008. The questioning was repeated in 2013 with 316 participating nursing students using the previous questionnaire. Results: 259 female nursing students completed the questionnaire in 2013. 31.6% of them were either overweight or obese, 28.5% exercised less than once a week, 42.9% smoked between 10 and 20 cigarettes a day and 72.6% drank alcohol, wherefrom 19.7% consumed alcohol in risky quantities. In comparison to the data of 266 female nursing students from 2008, there were significant differences in the BMI and alcohol consumption: The percentage of overweight and obese students and the percentage of alcohol consumers at risk increased significantly. Conclusions: Health behavior of female nursing students is often inadequate especially in regard to weight and cigarette and alcohol consumption. Strategies are required to promote healthy lifestyle choices.

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