4242 research outputs found
Sort by
Food web dynamics in coastal vegetated habitats of the Southern Gulf of Mexico
No full textThis dissertation aimed to study the food web dynamics and fish assemblage connectivity in different coastal settings in the microtidal portion of the Southern Gulf of Mexico comprised by the Centla Wetlands Biosphere Reserve and the Terminos Lagoon Protected Area. Based on stable isotope analysis (A 13C, A 15N) of riparian and aquatic basal resources, and representative consumer taxa in four study sites located 26, 25, 13 and 1 km from the coast, the overall hypothesis was that the importance of riparian-derived carbon (from marsh and/or mangrove vegetation) for aquatic consumers is highly variable across spatial scales, and that the periodic dry and wet conditions in the area (the later influenced by strong northerly winds) drive the major changes in resource availability and the connectivity of aquatic food webs. Results suggest that the role as feeding areas of coastal vegetated habitats varies across spatial and temporal scales. While the variation at the spatial scale has to do with factors like geomorphology, distance to the sea and availability of resources, the temporal variation (at the seasonal scale) relates with flood pulses (river-influenced areas) and the effect of winds (marine-influenced area). Finally, emphasis is given to the importance of habitat heterogeneity and seasonal environmental forces, particularly rain, in enhancing the connectivity of fish assemblages through freshwater runoff in river-influenced areas, making these sites attractive feeding areas for an array of marine species migrating into these productive systems. However, the role that wind exerts on this connectivity merits further consideration. This work contributes to the body of research addressing the different basal resources to aquatic consumers and food web connectivity in tropical coastal regions, as well as the specific importance of riparian-derived carbon in different ecosystems and under contrasting seasonal influences. This knowledge can be useful for management and conservation, particularly in face of the vulnerability and degradation of spatially and temporally complex ecosystems like Centla Wetlands and Terminos Lagoon
Entwicklung von Instrumenten zur Erfassung eines Patientennutzens bei hellem Hautkrebs, Rheumatoider Arthritis und Multipler Sklerose sowie die Validierung des Instrumentes für die Multiple Sklerose
Get PDFBackground: In the context of treatment benefit evaluation as well as driven by health service research requirements patient-centeredness gets increasingly important. The objective was to develop assessment instruments of patient-relevant benefits in the disorders rheumatoid arthritis (RA), multiple sclerosis (MS) and non-melanoma skin cancer (NMSC) based on the established Patient Benefit Index (PBI) methodology and the validation of the instrument for MS. Methods: Based on a multi-step development approach comprising an open item collection and multidisciplinary expert panel with clinicians, methodologists and patients, the pilot-versions were investigated for applicability and comprehensibility in cognitive pretests. Subsequently the PBI-MS was evaluated regarding its convergent validity, reliability and feasibility in a non-controlled prospective validation study with n=100 patients. Results: Three standardized and disease-specific PBI versions were developed (PBI-NMSC-S S (sirurgical): 9 items; PBI-RA: 20 items and PBI-MS: 27 items). They capture patient-relevant benefits of treatment and collect physical, mental and treatment-specific aspects, but also treatment-goals regarding leisure, social and working life. In a longitudinal cohort study the convergent validity of the PBI-MS was shown. The highest correlation was found cross-sectional with patients global impression of change (PaGIC) on treatment benefit with most content match to the construct (r=0.60, p 0.001). Comparably high correlations were found with generic EQ-5D-3L and EQ-VAS (r=0.55, p 0.001; r=0.61, p 0.001), while the PBI-MS correlation to the disease-specific HRQoL instruments HALEMS and MS-QOL were unexpectedly found to be lower (r=-0.36, p 0.05, r=-0.49, p 0.001). The correlation with physicians global impression of change (PhGIC) was on moderate effect size (r=0,44, p 0,001). Reliability was high (Cronbachs A A /-=0,90) and multidimensionality of the PBI-MS was given. A low level of missing values and the results of the feasibility survey indicated comprehensiveness, acceptance and applicability. Conclusion: The PBI-MS is a valid instrument to capture patient-relevant benefits for relapse treatment suitable especially for use in clinical routine, but potentially also contributing in clinical or quality of care studies and patient-centeredness health care research. Due to their relevance and potential the PBI-NMSC-S and PBI-RA should also be tested concerning psychometric criteria in follow-up studies
Humanistic Elements in the Educational Practice at a United States Sub-Baccalaureate Technical College
Get PDFHumanism has never been able to establish a firm place in technical education, which remains predominantly pragmatist in response to industry needs, certification requirements and educational standardisation. However, after a period of decline, humanism has made somewhat of a comeback as part of the movement toward studentcentred education. Research conducted at a technical college showed that although humanistic elements are largely absent from educational practice in post-secondary technical education, they are not detrimental to the achievement of stated educational objectives. This research indicated that including humanistic elements in educational practice will enable instructors to be more effective in helping students to develop skills in relation to team work, problem-solving, systems improvement, lifelong learning and other areas that are becoming increasingly necessary for success in the workplace. The specific recommendations from this research include a constructivist approach with a focus on contextual teaching and learning using situated cognition, cognitive apprenticeships, anchored instruction and authentic assessment. At the same time, some suggestions for improving professional development for teachers by using a Gestalt approach along with self-study in the context of learning communities have been discussed
On-board Trajectory Computation for Mars Atmospheric Entry Based on Parametric Sensitivity Analysis of Optimal Control Problems
Get PDFThis thesis develops a precision guidance algorithm for the entry of a small capsule into the atmosphere of Mars. The entry problem is treated as nonlinear optimal control problem and the thesis focuses on developing a suboptimal feedback law. Therefore parametric sensitivity analysis of optimal control problems is combined with dynamic programming. This approach enables a real-time capable, locally suboptimal feedback scheme. The optimal control problem is initially considered in open loop fashion. To synthesize the feedback law, the optimal control problem is embedded into a family of neighboring problems, which are described by a parameter vector. The optimal solution for a nominal set of parameters is determined using direct optimization methods. In addition the directional derivatives (sensitivities) of the optimal solution with respect to the parameters are computed. Knowledge of the nominal solution and the sensitivities allows, under certain conditions, to apply Taylor series expansion to approximate the optimal solution for disturbed parameters almost instantly. Additional correction steps can be applied to improve the optimality of the solution and to eliminate errors in the constraints. To transfer this strategy to the closed loop system, the computation of the sensitivities is performed with respect to different initial conditions. Determining the perturbation direction and interpolating between sensitivities of neighboring initial conditions allows the approximation of the extremal field in a neighborhood of the nominal trajectory. This constitutes a locally suboptimal feedback law. The proposed strategy is applied to the atmospheric entry problem. The developed algorithm is part of the main control loop, i.e. optimal controls and trajectories are computed at a fixed rate, taking into account the current state and parameters. This approach is combined with a trajectory tracking controller based on the aerodynamic drag. The performance and the strengthsa and weaknesses of this two degree of freedom guidance system are analyzed using Monte Carlo simulation. Finally the real-time capability of the proposed algorithm is demonstrated in a flight representative processor-in-the-loop environment
Co-Construction Kits : the Transformative Potential of Interpersonal Connections for After-School Centres
No full textThe following thesis makes contributions to the design and educational use of tangible construction kits. It is shown that their transformative effect for young people in economically-disadvantaged communities is closely tied to kits, and their design, being embedded in a concept which places the communal nature of use at the centre. The approach enables young people to use the tools to strengthen social engagement and make investments their social environment
Coral bleaching and recovery in the Thai Andaman Sea
Get PDFSevere coral bleaching in response to increasing sea temperatures threatens coral reefs in many regions of the world, including the Andaman Sea, Thailand. Coral bleaching involves the breakdown of the coral-algae symbiosis, resulting in the loss of the intracellular microalgal dinoflagellates of the diverse genus Symbiodinium, also called a zooxanthellaea . Elevated temperatures and high solar irradiation are considered to be the primary factors causing widespread coral bleaching. In the Andaman Sea, bleaching events have occurred in the years 1991, 1995, 1998, 2003, 2010, and 2016 following abnormally high sea-surface temperatures (SST). The 2010 SST anomaly was the hottest on record with unprecedented bleaching and mortality of corals. However, corals showed different responses to thermal stress and important spatial differences, both between and within reefs. This thesis explores the causes and consequences of coral bleaching events in the Andaman Sea of Thailand on the coral community, organismal and sub-organismal (symbiont) scale. Physico-chemical factors as well as species-specific responses of corals to thermal stress contribute to complex patterns of bleaching and mortality, revealing large differences in acclimatization and adaptation in space and time. Understanding the species-specific bleaching responses in their particular environment provides a promising tool for management, as the identification of bleaching-tolerant corals and the factors enhancing coral tolerance may help improve the design of appropriate rehabilitation techniques. This study highlights potential refuge areas for corals which are necessary to protect and facilitate quick post-bleaching recovery. The protection of reef areas harbouring coral communities tolerant to thermal stress, along with the rehabilitation of degraded coral reef ecosystems with bleaching tolerant species, is a promising approach to improve the success of reef conservation management in a warming ocean
Temperature and Freshwater Fluxes by Individual Eddies in the North Atlantic Ocean
Get PDFThis study investigates the temperature and freshwater fluxes by individual eddies in the North Atlantic between 40 degrees-55 degrees N and 60 degrees-10 degrees W for the period January 1993 to April 2014. Focus is on a zonal section along 47 degrees N, roughly at the boundary between the subpolar and the subtropical gyres. The main question is to what extent eddies are responsible for the variability and mixing in the region and how the anomalies of temperature and freshwater carried by eddies contribute to the overall fluxes across 47 degrees N. Almost 37000 eddies with a lifetime longer than one week are detected from surface geostrophic velocity fields derived from satellite-altimetry. First, only surface temperature fluxes based on collocating detected eddies with sea surface temperature observations from satellites are analyzed. The results are compared to two model simulations spanning the period from 2002 to 2013 with different horizontal resolution (1/4 degree and 1/12 degree), allowing to assess the impact of different resolution on the results. The analysis is then extended to three dimensional temperature and freshwater fluxes. The temperature and salinity fields used for the calculation of the fluxes stem from a new product that was derived from dynamic height using the Gravest Empirical Mode (GEM) technique. Using this new product allows for the first time to relate every detected eddy to profiles of temperature and freshwater and to analyze the respective fluxes across 47 degrees N. Since the 1/12 degree model configuration shows the more realistic results for the surface temperature fluxes, the comparison of the observed temperature and freshwater fluxes is confined to this configuration. The highest number of eddies is found along the pathway of the North Atlantic Current (NAC), roughly following the 4000 m isobath, and on the Grand Banks of Newfoundland. The typical vertical extent is around 1400 m, with anti-cyclonic eddies on average 200 m deeper than cyclonic eddies. Relating the observed eddies to the top-to-bottom velocity distribution from ship observations shows that the highest fluxes are linked to the fastest and most pronounced current branches in the western Newfoundland Basin. The time series of surface temperature fluxes by eddies crossing 47 degrees N reveal that single isolated eddies with large SST signatures contribute about 25% to the surface temperature flux. Similarly, about 15-35% of the three dimensional temperature and freshwater fluxes across 47 degrees N stem from eddies with large temperature and freshwater anomalies. The largest contribution to the flux by individual eddies stems from cold and fresh eddies originating from the Western Boundary Current moving northward with the NAC. While the fluxes by individual eddies are very small compared to the basin-wide integrated total fluxes, eddies induce a large part of the variability of the total flux. The effect of fluxes by individual eddies is regionally confined, but eddies contribute to the cooling of the NAC in the region around the Grand Banks of Newfoundland, to the local recirculation in the Newfoundland Basin, and in part to the interior southward pathway of subpolar water
Cluster Renewal : complex Processes in Two Agricultural Engineering Clusters of North-Western Germany
Get PDFThis cumulative thesis contributes to the recent discussion in evolutionary economic geography research (EEG) on how regional industrial clusters evolve over time. It identifies a research gap in the understanding of socio-technical cluster renewal processes in the recent EEG literature. To face this gap, it introduces two concepts that did not play a prominent role in the EEG literature so far, but that allow a better understanding of the role of industry-specific as well as cluster-external factors for cluster renewal: the modes of innovation concept as well as the literature on geographies of sustainability transitions. The developed theoretical expectations are investigated in two qualitative case studies on two agricultural engineering clusters of North-Western Germany that experienced socio-technical re-orientation in the early 21st century: the Osnabrück-based farm trailer and the Vechta-based stable technology industries
Ausmaß und Risiken des off-label Gebrauchs von Antidepressiva und Antipsychotika bei Kindern und Jugendlichen in Deutschland
Get PDFUsing claims data of about two million young persons per year, we examined extent and risks of antidepressant and antipsychotic off-label use in Germany. During the study period from 2004-2011, the prevalence of antidepressant prescriptions varied between 1.7 and 2.1 per 1,000 minors. The share of off-label prescriptions, decreased from 64.2 to 36.3%. The prevalence of antipsychotic prescriptions ranged from 2.0 to 2.6 per 1,000 minors and between 61.0 and 69.5% of all prescriptions were off-label. The studied adverse drug reactions occurred rarely and there were no significant differences between on- and off-label use. Antidepressant and antipsychotic drugs are commonly prescribed off-label to young patients. This, however, does not necessarily indicate inappropriate drug treatment but rather a lack of approved drugs for pediatric patients. Further and more detailed studies on the safety and efficacy of antidepressant and antipsychotic agents in the treatment of young people are needed