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Search Results: 1 - 10 of 44856 matches for " Giesler Michael "
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Midterm results after arterial switch operation for transposition of the great arteries: a single centre experience
Popov Aron Frederik,Tirilomis Theodor,Giesler Michael,Oguz Coskun Kasim
Journal of Cardiothoracic Surgery , 2012, DOI: 10.1186/1749-8090-7-83
Abstract: Background The arterial switch operation (ASO) has become the surgical approach of choice for d-transposition of the great arteries (d-TGA). There is, however an increased incidence of midterm and longterm adverse sequelae in some survivors. In order to evaluate operative risk and midterm outcome in this population, we reviewed patients who underwent ASO for TGA at our centre. Methods In this retrospective study 52 consecutive patients with TGA who underwent ASO between 04/1991 and 12/1999 were included. To analyze the predictors for mortality and adverse events (coronary stenoses, distortion of the pulmonary arteries, dilatation of the neoaortic root, and aortic regurgitation), a multivariate analysis was performed. The follow-up time was ranged from 1–10 years (mean 5 years, cumulative 260 patient-years). Results All over mortality rate was 15.4% and was only observed in the early postoperative period till 1994. The predictors for poor operative survival were low APGAR-score, older age at surgery, and necessity of associated surgical procedures. Late re-operations were necessary in 6 patients (13.6%) and included a pulmonary artery patch enlargement due to supravalvular stenosis (n = 3), coronary revascularisation due to coronary stenosis in a coronary anatomy type E, aortic valve replacement due to neoaortic valve regurgitation (n = 2), and patch-plasty of a pulmonary vein due to obstruction (n = 1). The dilatation of neoaortic root was not observed in the follow up. Conclusions ASO remains the procedure of choice for TGA with acceptable early and late outcome in terms of overall survival and freedom of reoperation. Although ASO is often complex and may be associated with morbidity, most patients survived without major complications even in a small centre.
Novice medical students: Individual patterns in the use of learning strategies and how they change during the first academic year [Medizinstudierende im ersten Studienjahr: Individuelle Muster der Lernstrategienutzung und ihre Ver nderung]
Fabry, G?tz,Giesler, Marianne
GMS Zeitschrift für Medizinische Ausbildung , 2012, DOI: 10.3205/zma000826
Abstract: [english] Background: Adequate use of different learning strategies is one of the most important prerequisites of academic success. The actual use of learning strategies is the result of an interaction between individual and situational variables. Against this background we conducted a longitudinal study with first year medical students to investigate whether individuals show different patterns in their use of learning strategies and whether these patterns change during the first academic year.Methods: Medical students (N=175, 58% female) were surveyed three times in their first academic year regarding their use of learning strategies. A hierarchical cluster analysis (Ward) was conducted in order to identify groups of students with different patterns of learning strategies. Results: We identified four different patterns in approaches to learning among novice medical students (“easy-going”, “flexible”, “problematic” and “hardworking” learners). Compared to their peers, the problematic learners had the worst final school grades. In addition changes in the use of learning strategies were identified, most of them occurred during the first term.Conclusion: Students start their academic studies with different patterns of learning strategies; the characteristics of these patterns change during the first academic year. Further research is necessary to better understand how individual and situational variables determine students’ learning. [german] Hintergrund: Verschiedene Lernstrategien zweckm ig zu nutzen, ist eine der wichtigsten Voraussetzungen für Lernerfolg. Welche Lernstrategien tats chlich genutzt werden, ist abh ngig von der Interaktion individueller und situativer Variablen. Vor diesem Hintergrund haben wir eine l ngsschnittlich angelegte Studie durchgeführt, um herauszufinden, ob individuelle Muster der Lernstrategienutzung identifiziert werden k nnen und wie sich diese Muster im Verlauf des ersten Studienjahres ver ndern.Methoden: Studierende der Medizin (N=175; 58% weiblich) wurden innerhalb des ersten Studienjahrs dreimal zu ihren Lernstrategien befragt. Um Gruppen von Studierenden mit unterschiedlichen Lernstrategiemustern zu identifizieren, wurden hierarchische Clusteranalysen (Ward) durchgeführt.Ergebnisse: Es konnten vier verschiedene Lernstrategiemuster bei den Studierenden des ersten Semesters der Humanmedizin identifiziert werden (die unbekümmerten“, die flexiblen“, die problematischen“ und die flei igen“ Lerner). Im Vergleich zu ihren Mitstudierenden hatten die problematischen Lerner die schlechtesten Abiturnoten. Weiterhin konnten vo
Application of a Beamforming Technique to the Measurement of Airfoil Leading Edge Noise
Thomas Geyer,Ennes Sarradj,Jens Giesler
Advances in Acoustics and Vibration , 2012, DOI: 10.1155/2012/905461
Abstract: The present paper describes the use of microphone array technology and beamforming algorithms for the measurement and analysis of noise generated by the interaction of a turbulent flow with the leading edge of an airfoil. Experiments were performed using a setup in an aeroacoustic wind tunnel, where the turbulent inflow is provided by different grids. In order to exactly localize the aeroacoustic noise sources and, moreover, to separate airfoil leading edge noise from grid-generated noise, the selected deconvolution beamforming algorithm is extended to be used on a fully three-dimensional source region. The result of this extended beamforming are three-dimensional mappings of noise source locations. Besides acoustic measurements, the investigation of airfoil leading edge noise requires the measurement of parameters describing the incident turbulence, such as the intensity and a characteristic length scale or time scale. The method used for the determination of these parameters in the present study is explained in detail. To demonstrate the applicability of the extended beamforming algorithm and the experimental setup as a whole, the noise generated at the leading edge of airfoils made of porous materials was measured and compared to that generated at the leading edge of a common nonporous airfoil. 1. Introduction When an airfoil is subject to a turbulent flow, noise is basically generated at both the airfoil leading edge and the trailing edge. If the turbulence intensity in the inflow is higher than that of the turbulence generated within the boundary layer (which subsequently interacts with the trailing edge and generates trailing edge noise), the radiated aeroacoustic noise is dominated by sound generated at the leading edge of the airfoil. As early experiments on a flat plate showed, the existence of turbulence in the incoming flow can increase the noise radiation significantly [1]. Additionally, the frequency spectrum may be different for both noise source locations. For example, it was found that the noise from wind turbines is dominated at low frequencies by broadband inflow turbulence noise, while at higher frequencies noise due to the interaction of the turbulent boundary layer with the trailing edge of the blades becomes more important [2]. Airfoil leading edge noise, also referred to as incident turbulence interaction noise, is a result of turbulent structures which generate fluctuating forces that act on the airfoil. Consequently, the investigation of airfoil leading edge noise not only requires acoustic measurements, but also requires some
Within- and Across-Species Responses of Plant Traits and Litter Decomposition to Elevation across Contrasting Vegetation Types in Subarctic Tundra
Maja K. Sundqvist, Reiner Giesler, David A. Wardle
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0027056
Abstract: Elevational gradients are increasingly recognized as a valuable tool for understanding how community and ecosystem properties respond to climatic factors, but little is known about how plant traits and their effects on ecosystem processes respond to elevation. We studied the response of plant leaf and litter traits, and litter decomposability across a gradient of elevation, and thus temperature, in subarctic tundra in northern Sweden for each of two contrasting vegetation types, heath and meadow, dominated by dwarf shrubs and herbaceous plants respectively. This was done at each of three levels; across species, within individual species, and the plant community using a community weighted average approach. Several leaf and litter traits shifted with increasing elevation in a manner consistent with greater conservation of nutrients at all three levels, and the most consistent response was an increase in tissue N to P ratio. However, litter decomposition was less directly responsive to elevation because the leaf and litter traits which were most responsive to elevation were not necessarily those responsible for driving decomposition. At the community level, the response to elevation of foliar and litter traits, and decomposability, varied greatly among the two vegetation types, highlighting the importance of vegetation type in determining ecological responses to climatic factors such as temperature. Finally our results highlight how understanding the responses of leaf and litter characteristics of functionally distinct vegetation types, and the processes that they drive, to temperature helps provide insights about how future climate change could affect tundra ecosystems.
Stable carbon isotopes as indicators for environmental change in palsa peats
C. Alewell, R. Giesler, J. Klaminder, J. Leifeld,M. Rollog
Biogeosciences (BG) & Discussions (BGD) , 2011,
Abstract: Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by a high biodiversity and sensitive ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and induce a degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Soils dominated by aerobic degradation can be expected to have a clear increase of carbon isotopes (δ13C) with depth, due to preferential release of 12C during aerobic mineralization. In soils with suppressed degradation due to anoxic conditions, stable carbon isotope depth profiles are either more or less uniform indicating no or very low degradation or depth profiles turn to lighter values due to an enrichment of recalcitrant organic substances during anaerobic mineralisation which are depleted in 13C. The isotope depth profile of the peat in the water saturated depressions (hollows) at the yet undisturbed mire Storflaket indicated very low to no degradation but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent breaking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 and 25 cm. The age of these turning points was 14C dated between 150 and 670 yr and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.
Entwicklung eines Fragebogens zur Erfassung von Kompetenzen in der Medizin: Ergebnisse zur Reliabilit t und Validit t [Development of a questionnaire to assess medical competencies: Reliability and validity of the Questionnaire]
Giesler, Marianne,Forster, Johannes,Biller, Silke,Fabry, G?tz
GMS Zeitschrift für Medizinische Ausbildung , 2011, DOI: 10.3205/zma000743
Abstract: [english] Introduction: While preparing a graduate survey for medical education in 2008 we realized that no instrument existed that would be suitable to evaluate whether the learning outcomes outlined in the Medical Licensure Act ( AppO) would be met. Therefore we developed the (Freiburger Fragebogen zur Erfassung von Kompetenzen in der Medizin, FKM) which has been revised and extended several times since then.Currently the FKM includes 45 items which are assigned to nine domains that correspond to the CanMEDS roles: medical expertise, communication, team-work, health and prevention, management, professionalism, learning, scholarship, and personal competencies.Methods: In order to test the reliability and validity of the questionnaire we have repeatedly surveyed medical students and residents since May 2008. In this article we report on the results of a cross-sectional study with 698 medical students from the preclinical and clinical years. In addition, we report the results of a survey of 514 residents who were up to two years into their residency.Results and conclusions: In summary, results show that the scales of the FKM are reliable (Cronbach’s α between .68 and .97). Significant differences in means between selected groups of students support the measure’s construct validity. Furthermore, there is evidence that the FKM might be used as a screening tool e.g. in graduate surveys to identify weaknesses in the medical education curriculum. [german] Einführung: Bei der Vorbereitung einer Absolventenbefragung im Fach Humanmedizin wurde deutlich, dass ein Verfahren fehlte, mit dem erfasst werden kann, ob die in der AppO aufgeführten Lehr- und Lernziele erreicht werden. Aus diesem Grund wurde der von einer Arbeitsgruppe an der Medizinischen Fakult t der Universit t Freiburg entwickelt. Der FKM wurde seitdem mehrmals überarbeitet und erweitert. Er umfasst derzeit 45 Items, die neun Kompetenzbereichen zugeordnet werden. Diese Kompetenzbereiche stimmen im Wesentlichen mit den CanMEDS-Rollen überein. Methode: Um die Reliabilit t und Validit t des Fragebogens zu überprüfen, wurden seit Mai 2008 mehrfach Studierende und Assistenz rzte befragt. In dem vorliegenden Beitrag werden die Ergebnisse einer Querschnittsstudie berichtet, in der 698 Studierende des ersten und zweiten Studienabschnitts den FKM beantwortet haben. Des Weiteren werden die Ergebnisse von 514 Assistenz rzten mit bis zu zwei Jahren Berufserfahrung beschrieben, die den FKM im Rahmen einer Absolventenbefragung ausgefüllt haben.Ergebnisse und Schlussfolgerungen: Die bisherigen Ergebnisse zeigen, da
Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats
C. Alewell,R. Giesler,J. Klaminder,J. Leifeld
Biogeosciences Discussions , 2011, DOI: 10.5194/bgd-8-527-2011
Abstract: Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by an unique biodiversity and ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and results in degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Carbon isotope (δ13C) depth profile of the yet undisturbed mire Storflaket indicated very low to no degradation of the peat in the water saturated depressions (hollows) but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent braking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 to 25 cm. The age of these turning point was 14C dated between 150 and 670 years and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.
Investigating the relationship between subsurface hydrology and dissolved carbon fluxes for a sub-arctic catchment
S. W. Lyon,M. M?rth,C. Humborg,R. Giesler
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-1677-2010
Abstract: In recent years, there has been increased interest in carbon cycling in natural systems due to its role in a changing climate. Northern latitude systems are especially important as they may serve as a potentially large source or sink of terrestrial carbon. There are, however, a limited number of investigations reporting on actual flux rates of carbon moving from the subsurface landscape to surface water systems in northern latitudes. This study estimates dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes from the subsurface landscape for a sub-arctic catchment located in northern Sweden. Estimates are based on observed annual in-stream flux-averaged concentrations of DOC and DIC at the outlet of the 566 km2 Abiskojokken catchment and from catchment-scale transport modeling based on advective solute travel times and their spatial distributions. We also demonstrate the importance of correctly representing the spatial distribution of the advective solute travel times along the various flow and transport pathways. For the sub-arctic catchment considered in this study, there is a relative balance between the flux of DOC and DIC from the subsurface landscape to the surface water system. This balance between DOC and DIC fluxes could shift under future climatic changes that influence the hydrological and biogeochemical system.
Estimation of permafrost thawing rates in a sub-arctic catchment using recession flow analysis
S. W. Lyon,G. Destouni,R. Giesler,C. Humborg
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: Permafrost thawing is likely to change the flow pathways taken by water as it moves through arctic and sub-arctic landscapes. The location and distribution of these pathways directly influence the carbon and other biogeochemical cycling in northern latitude catchments. Direct observations of permafrost depth are difficult to perform at scales larger than a local scale. Using recession flow analysis, it may be possible to detect and estimate the rate of permafrost thawing based on a long-term streamflow record. We demonstrate the application of this approach to the sub-arctic Abiskojokken catchment in northern Sweden. Based on recession flow analysis, we estimate that permafrost in this catchment may be thawing at an average rate of about 0.9 cm/yr during the past 90 years. This estimated thawing rate is consistent with direct observations of permafrost thawing rates, ranging from 0.7 to 1.3 cm/yr over the past 30 years in the region.
Stellenwert des transmitralen Str mungsprofils zur Quantifizierung der Mitralklappeninsuffizienz
Grossmann G,Giesler M,Hombach V,H?her M
Journal für Kardiologie , 2002,
Abstract: Echokardiographische Parameter sollten eine Mitralklappeninsuffizienz zuverl ssig quantifizieren k nnen und einfach zu bestimmen sein. In der vorliegenden Studie wurde untersucht, ob die Parameter des transmitralen Str mungsprofils diese Anforderungen erfüllen. Patienten und Methoden: Bei 41 Patienten (27 M nner) im Alter von 61 ± 12 Jahren mit Mitralklappeninsuffizienz wurde die maximale frühdiastolische und die mittlere Geschwindigkeit des transmitralen Str mungsprofils mit dem gepulsten Doppler gemessen. Daraus wurden nach Messung der maximalen und mittleren systolischen Str mungsgeschwindigkeit im linksventrikul ren Ausflu trakt und des Durchmessers des Mitralklappenrings weitere Parameter abgeleitet. Zus tzlich wurde im Farbdoppler der Radius der proximalen isokinetischen Schalen für eine Str mungsgeschwindigkeit von 28 cm/s bestimmt. Bei 34 der 41 Patienten wurde der angiographische Schweregrad der Mitralklappeninsuffizienz ermittelt. Ergebnisse: Die Rangkorrelationskoeffizienten zum Schweregrad der Mitralklappeninsuffizienz betrugen für die Parameter des transmitralen Str mungsprofils 0,39 bis 0,73 (p 0,05 - p 0,001), für den Radius der proximalen isokinetischen Schalen 0,87 (p 0,001). Eine hochgradige Mitralklappeninsuffizienz wurde durch die Parameter des transmitralen Str mungsprofils mit einer Sensitivit t/Spezifit t von 47-79 %/71?100 % erkannt; die Berücksichtigung der Str mungsgeschwindigkeit im linksventrikul ren Ausflu trakt oder des Mitralklappenringdurchmessers ergab keine Vorteile. Die Sensitivit t/Spezifit t des Radius der proximalen, isokinetischen Schalen war 94 %/93 %. Die Parameter des transmitralen Str mungsprofils und der Radius der proximalen isokinetischen Schale korrelierten mit Koeffizienten von 0,22-0,71. Diskussion: Die Vermessung des transmitralen Str mungsprofils ist einfach und eine spezifische Methode zur Erkennung einer hochgradigen Mitralklappeninsuffizienz. Letztere lie sich sicher identifizieren, wenn die Messungen oberhalb definierter Grenzwerte lagen. Die Bestimmung des Radius der proximalen isokinetischen Schalen war jedoch für die Diagnose einer hochgradigen Mitralklappeninsuffizienz sensitiver.
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