Experimentelle Untersuchungen der Strömung an einem Rotorblattmodell

In dieser Arbeit wurde die Entwicklung der Strömungsablösung an einem Rotorblattmodell mit freier Blattspitze mit linearer Verwindung von 3,3°/m experimentell untersucht. Sowohl die Betrachtung des statischen Strömungsabrisses in einer Anstellwinkelreihe von -5° bis 18° Wurzelanstellwinkel als auch der dynamische Strömungsabriss bei verschiedenen zyklischen Anstellwinkelschwingungen von 11°±6° mit drei unterschiedlichen Frequenzen wurden im Rahmen der Ausarbeitung behandelt. Insbesondere die spannweitigen Differenzen sowie der Einfluss der Nickfrequenz auf die Entwicklung der Strömungsablösung waren dabei von Interesse. Die Betrachtung erfolgte anhand von Stereo-PIV-Messungen an drei Profilschnitten des Rotorblattmodells konstanter Spannweite und Druckmessungen auf der Modelloberfläche

Spanwise Differences in Static and Dynamic Stall on a Pitching Rotor Blade Tip Model

An experimental investigation of static and dynamic stall on a rotor blade tip model with an aspect ratio of 6.2 at a chord Reynolcls number of900 ,000 and a Mach numbcr of0.16 is presented. The spatiotemporal behavior of the flow separation was analyzed using unstcady surface pressurc measurements ancl high-speecl particle image velocimetry. The maximum effective angle of attack prior to stall is shiftecl to approximately two-thirds of the span outboard because of an increasing geometric angle of attack of the model towarcl the tip. Different stages of flow separation for static angles of attack were identified, inclucling the occurrence of two stall cells. Du ring dynamic stall, the leacling edge vortcx formation starts near the spanwise position of thc static stall onset. The subsequent spanwise evolution of the vortex formation results in two vorticcs for deep stall conclitions, covering the samc spanwisc arcas as thc two static stall cclls

Spanwise Differences in Static and Dynamic Stall on a Pitching Rotor Blade Tip Model

An experimental investigation of static and dynamic stall on a rotor blade tip model with a parabolic tip geometry and aspect ratio 6.2 at a chord Reynolds number of 900,000 and a Mach number of 0.16 is presented. The resulting flow is analyzed based on unsteady surface pressure measurements and quantitative flow visualizations by high-speed particle image velocimetry. The flow separation is found to be delayed near the parabolic blade tip for static angles of attack as well as for sinusoidal angle of attack motions. The maximum effective angle of attack prior to stall is shifted to approximately two-thirds of the span outboard from the root because of a positive twist of the model with an increasing geometric angle of attack towards the tip. The stall onset is observed near the section with the maximum effective angle of attack, with a subsequent spanwise spreading of the flow separation. Different stages of flow separation for static angles of attack are identified one of them with the occurrence of two stall cells. During dynamic stall, the leading edge vortex formation starts near the maximum effective angle of attack and the pitching moment peak resulting from the passage of the dynamic stall vortex is higher at this section. Further inboard the maximum aerodynamic loads are of comparable magnitude whereas the outboard section shows reduced peaks due to the influence of the wing tip vortex

T-REX17 is a transiently expressed non-coding RNA essential for human endoderm formation

Long non-coding RNAs (lncRNAs) have emerged as fundamental regulators in various biological processes, including embryonic development and cellular differentiation. Despite much progress over the past decade, the genome-wide annotation of lncRNAs remains incomplete and many known non-coding loci are still poorly characterized. Here, we report the discovery of a previously unannotated lncRNA that is transcribed 230 kb upstream of the SOX17 gene and located within the same topologically associating domain. We termed it T-REX17 (Transcript Regulating Endoderm and activated by soX17) and show that it is induced following SOX17 activation but its expression is more tightly restricted to early definitive endoderm. Loss of T-REX17 affects crucial functions independent of SOX17 and leads to an aberrant endodermal transcriptome, signaling pathway deregulation and epithelial to mesenchymal transition defects. Consequently, cells lacking the lncRNA cannot further differentiate into more mature endodermal cell types. Taken together, our study identified and characterized T-REX17 as a transiently expressed and essential non-coding regulator in early human endoderm differentiation

Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe

Background Little is known about the incidence of severe critical events in children undergoing general anaesthesia in Europe. We aimed to identify the incidence, nature, and outcome of severe critical events in children undergoing anaesthesia, and the associated potential risk factors. Methods The APRICOT study was a prospective observational multicentre cohort study of children from birth to 15 years of age undergoing elective or urgent anaesthesia for diagnostic or surgical procedures. Children were eligible for inclusion during a 2-week period determined prospectively by each centre. There were 261 participating centres across 33 European countries. The primary endpoint was the occurence of perioperative severe critical events requiring immediate intervention. A severe critical event was defined as the occurrence of respiratory, cardiac, allergic, or neurological complications requiring immediate intervention and that led (or could have led) to major disability or death. This study is registered with ClinicalTrials.gov, number NCT01878760. Findings Between April 1, 2014, and Jan 31, 2015, 31â127 anaesthetic procedures in 30â874 children with a mean age of 6·35 years (SD 4·50) were included. The incidence of perioperative severe critical events was 5·2% (95% CI 5·0â5·5) with an incidence of respiratory critical events of 3·1% (2·9â3·3). Cardiovascular instability occurred in 1·9% (1·7â2·1), with an immediate poor outcome in 5·4% (3·7â7·5) of these cases. The all-cause 30-day in-hospital mortality rate was 10 in 10â000. This was independent of type of anaesthesia. Age (relative risk 0·88, 95% CI 0·86â0·90; p<0·0001), medical history, and physical condition (1·60, 1·40â1·82; p<0·0001) were the major risk factors for a serious critical event. Multivariate analysis revealed evidence for the beneficial effect of years of experience of the most senior anaesthesia team member (0·99, 0·981â0·997; p<0·0048 for respiratory critical events, and 0·98, 0·97â0·99; p=0·0039 for cardiovascular critical events), rather than the type of health institution or providers. Interpretation This study highlights a relatively high rate of severe critical events during the anaesthesia management of children for surgical or diagnostic procedures in Europe, and a large variability in the practice of paediatric anaesthesia. These findings are substantial enough to warrant attention from national, regional, and specialist societies to target education of anaesthesiologists and their teams and implement strategies for quality improvement in paediatric anaesthesia. Funding European Society of Anaesthesiology

Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe

Background Little is known about the incidence of severe critical events in children undergoing general anaesthesia in Europe. We aimed to identify the incidence, nature, and outcome of severe critical events in children undergoing anaesthesia, and the associated potential risk factors. Methods The APRICOT study was a prospective observational multicentre cohort study of children from birth to 15 years of age undergoing elective or urgent anaesthesia for diagnostic or surgical procedures. Children were eligible for inclusion during a 2-week period determined prospectively by each centre. There were 261 participating centres across 33 European countries. The primary endpoint was the occurence of perioperative severe critical events requiring immediate intervention. A severe critical event was defined as the occurrence of respiratory, cardiac, allergic, or neurological complications requiring immediate intervention and that led (or could have led) to major disability or death. This study is registered with ClinicalTrials.gov, number NCT01878760. Findings Between April 1, 2014, and Jan 31, 2015, 31 127 anaesthetic procedures in 30 874 children with a mean age of 6.35 years (SD 4.50) were included. The incidence of perioperative severe critical events was 5.2% (95% CI 5.0-5.5) with an incidence of respiratory critical events of 3.1% (2.9-3.3). Cardiovascular instability occurred in 1.9% (1.7-2.1), with an immediate poor outcome in 5.4% (3.7-7.5) of these cases. The all-cause 30-day in-hospital mortality rate was 10 in 10 000. This was independent of type of anaesthesia. Age (relative risk 0.88, 95% CI 0.86-0.90; p<0.0001), medical history, and physical condition (1.60, 1.40-1.82; p<0.0001) were the major risk factors for a serious critical event. Multivariate analysis revealed evidence for the beneficial effect of years of experience of the most senior anaesthesia team member (0.99, 0.981-0.997; p<0.0048 for respiratory critical events, and 0.98, 0.97-0.99; p=0.0039 for cardiovascular critical events), rather than the type of health institution or providers. Interpretation This study highlights a relatively high rate of severe critical events during the anaesthesia management of children for surgical or diagnostic procedures in Europe, and a large variability in the practice of paediatric anaesthesia. These findings are substantial enough to warrant attention from national, regional, and specialist societies to target education of anaesthesiologists and their teams and implement strategies for quality improvement in paediatric anaesthesia