Models of bright nickel-free supernovae from stripped massive stars with circumstellar shells

The nature of an emerging class of rapidly fading supernovae (RFSNe)--characterized by their short-lived light curve duration, but varying widely in peak brightness--remains puzzling. Whether the RFSNe arise from low-mass thermonuclear eruptions on white dwarfs or from the core collapse of massive stars is still a matter of dispute. We explore the possibility that the explosion of hydrogen-free massive stars could produce bright but rapidly fading transients if the effective pre-supernova radii are large and if little or no radioactive nickel is ejected. The source of radiation is then purely due to shock cooling. We study this model of RFSNe using spherically symmetric hydrodynamics and radiation transport calculations of the explosion of stripped stars embedded in helium-dominated winds or shells of various masses and extent. We present a parameter study showing how the properties of the circumstellar envelopes affect the dynamics of the explosion and can lead to a diversity of light curves. We also explore the dynamics of the fallback of the innermost stellar layers, which might be able to remove radioactive nickel from the ejecta, making the rapid decline in the late time light curve possible. We provide scaling relations that describe how the duration and luminosity of these events depend on the supernova kinetic energy and the mass and radius of the circumstellar material.Comment: 16 pages, 17 figures, accepted to MNRA

Popularity and Gender Prototypicality: An Experimental Approach

These studies investigate links between conformity to gender norms and adolescents’ peer popularity. Previous research has established that popularity is associated with physical attractiveness in both boys and girls, as well as with gender-specific behaviors and activities (e.g., physical aggression and athletic involvement for boys, relational aggression and having stylish clothes for girls; (Vaillancourt & Hymel, 2005)) that often reflect gender-based expectations. However, research linking gender conformity with popularity is largely correlational in nature. Thus, the goal of the current studies was to examine the link between popularity and gender conformity experimentally. After being exposed to either a popularity priming condition or a neutral control, participants rated photographs (Study 1) and vignettes (Study 2) depicting gender-conforming and gender-nonconforming adolescents’ appearance and behavior on a number of popularity-related characteristics. Results indicate that gender typicality in appearance, but not behavior, is associated with popularity. Gender typicality may be a key predictor of adolescent popularity, but only as it pertains to physical appearance

Carbon Footprint in the Commercial Aviation Industry: Current Situation and Measures to Reduce Emissions Using the Example of Lufthansa

The goal of this thesis is to give an overview of the carbon footprint of the commercial aviation industry and to introduce measures to mitigate emissions. This will be done by taking the German Lufthansa Group as an example. In the first part, relevant theoretical background information will be given. It will be shown that the commercial aviation industry is subject to steady and relatively strong growth. Even though the global share of GHG emissions caused by air traffic is currently relatively low, it is projected to increase in accordance with overall industry growth. In the second part, measures taken by the aviation industry to reduce its emissions are presented using the example of Lufthansa. The measures that are taken are various, reaching from fleet renewal over infrastructural improvements such as airspace management to alternative fuels. It is also shown that the efficiency of an airline depends on different things and hence leads to different performances in the industry. Even though the reduction of emissions is typically related with a reduction of costs for the aviation industry, the progress in some areas is still relatively slow

Determinants and health risks of overweight and obesity among children and adolescents in Germany

The worldwide growing prevalence of overweight and obesity is becoming an important public health concern, also among children and adolescents. To establish effective prevention strategies, it is important to identify potential determinants and health related consequences in an early stage of life. In the present study, major determinants of overweight and obesity as well as the association between overweight and cardiovascular disease (CVD) risk factors were analysed using data from the large nationally representative German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Furthermore, the relevance of different anthropometric overweight measures for assessing health risk was evaluated. From the obtained information, parental overweight was identified as a major determinant of overweight and obesity among children and adolescents. A positive independent association with obesity was also seen for low socio-economic status (SES), migration background (only significant among 3-13 year olds), high weight gain during pregnancy (only significant for normal weight mothers), maternal smoking during pregnancy, high birth weight, short sleep duration (only significant among 3-10 year olds), and high media consumption. A low SES was also associated with a higher occurrence of unfavourable behaviour and conditions. All observed overweight measures, showed a consistent positive association with adverse CVD risk factors, even in children younger than 11 years of age. Depending on the overweight measure chosen, the highest differences in the adjusted mean values of CVD risk factors between overweight and non-overweight were 14 mg/dl for total cholesterol, 12 mg/dl for LDL cholesterol, -10 mg/dl for HDL cholesterol, 9 mm Hg for systolic blood pressure, 4 mm Hg for diastolic blood pressure, and 1.2 mg/l for C-reactive protein. Among adolescents, body mass index (BMI), waist circumference and waist-to-height ratio showed a stronger association with CVD risk factors than waist-to-hip ratio and skinfold thickness. Children and adolescents from families with overweight parents and low SES have a higher risk for overweight and obesity and are therefore important target groups for prevention. BMI, waist circumference and waist-to-height ratio are good predictors for adverse CVD risk factors. Combining BMI and waist circumference or BMI and waist-to-height ratio may be even more useful for risk assessment in large-scale epidemiologic studies.Determinanten und gesundheitliche Risiken von Übergewicht und Adipositas bei Kindern und Jugendlichen in Deutschland Die weltweit steigende Prävalenz von Übergewicht und Adipositas ist von zunehmender Public Health Relevanz, auch bei Kindern und Jugendlichen. Um effektive Präventionsstrategien auszuarbeiten, ist es wichtig Determinanten und gesundheitliche Konsequenzen frühzeitig zu identifizieren. In der vorliegenden Arbeit wurden die bedeutendsten Determinanten von Übergewicht und Adipositas sowie der Zusammenhang zwischen Übergewicht und kardiovaskulären Risikofaktoren analysiert. Hierzu wurden Daten des national repräsentativen Kinder- und Jugendgesundheitssurveys (KiGGS) herangezogen. Darüber hinaus wurden unterschiedliche anthropometrische Maße zur Bestimmung von Übergewicht hinsichtlich ihrer Relevanz für die Risikobewertung beurteilt. Elterliches Übergewicht wurde anhand der erhobenen Daten als wichtigste Determinante von Übergewicht und Adipositas bei Kindern und Jugendlichen identifiziert. Es zeigte sich zudem ein positiver unabhängiger Zusammenhang zwischen Adipositas und niedrigem Sozialstatus, Migrationshintergrund (nur bei 3- bis 13-Jährigen signifikant), hoher Gewichtszunahme in der Schwangerschaft (nur bei normalgewichtigen Müttern signifikant), mütterlichem Rauchen in der Schwangerschaft, hohem Geburtsgewicht, geringer Schlafdauer (nur bei 3- bis 10-Jährigen signifikant) sowie hohem Medienkonsum. Ein niedriger Sozialstatus war darüber hinaus mit einem höheren Auftreten ungünstiger Verhaltensweisen und Lebensbedingungen assoziiert. Bei allen erfassten Übergewichtsmaßen zeigte sich bereits bei Kindern unter 11 Jahren ein durchgehend positiver Zusammenhang mit ungünstigen kardiovaskulären Risikofaktoren. Abhängig vom gewählten Maß zur Bestimmung von Übergewicht zeigten sich die höchsten Unterschiede zwischen Übergewichtigen und nicht Übergewichtigen in den adjustierten Mittelwerten der kardiovaskulären Risikofaktoren mit 14 mg/dl für Gesamtcholesterin, 12 mg/dl für LDL-Cholesterin, -10 mg/dl für HDL-Cholesterin, 9 mm Hg für systolischen Blutdruck, 4 mm Hg für diastolischen Blutdruck und 1,2 mg/l für C-reaktives Protein. Bei Jugendlichen war der Zusammenhang von kardiovaskulären Risikofaktoren mit Body Mass Index (BMI), Taillenumfang und Taille-Größe-Quotient stärker ausgeprägt als der mit Taille-Hüft-Quotient und Hautfaltendicken. Kinder und Jugendliche aus Familien mit übergewichtigen Eltern und niedrigem Sozialstatus sind bedeutende Zielgruppen für die Prävention. BMI, Taillenumfang und Taille-Größe-Quotient sind gute Prädiktoren für ein ungünstiges kardiovaskuläres Risikoprofil. Eine Kombination von BMI und Taillenumfang oder BMI und Taille-Größe-Quotient kann für die Risikobewertung in großangelegten epidemiologischen Studien sinnvoll sein

Flow-field analysis of anti-kidney vortex film cooling

Film cooling is an important measure to enable an increase of the inlet temperature of a gas turbine and, thereby, to improve its overall efficiency. The coolant is ejected through spanwise rows of holes in the blades or endwalls to build up a film shielding the material. The holes often are inclined in the downstream direction and give rise to a kidney vortex. This is a counter-rotating vortex pair, with an upward flow direction between the two vortices, which tends to lift off the surface and to locally feed hot air towards the blade outside the pair. Reversing the rotational sense of the vortices reverses these two drawbacks into advantages. In the considered case, an anti-kidney vortex is generated using two subsequent rows of holes both inclined downstream and yawed spanwise with alternating angles. In a previous study, we performed large-eddy simulations (which focused on the fully turbulent boundary layer) of this anti-kidney vortex film-cooling and compared them to a corresponding physical experiment. The present work analyzes the simulated flow field in detail, beginning in the plenum (inside the blade or endwall) through the holes up to the mixture with the hot boundary layer. To identify the vortical structures found in the mean flow and in the instantaneous flow, we mostly use the λ 2 criterion and the line integral convolution (LIC) technique indicating sectional streamlines. The flow regions (coolant plenum, holes, and boundary layer) are studied subsequently and linked to each other. To track the anti-kidney vortex throughout the boundary layer, we propose two criteria which are based on vorticity and on LIC results. This enables us to associate the jet vortices with the cooling effectiveness at the wall, which is the key feature of film coolin

Vortical flow in the utricle and the ampulla: a computational study on the fluid dynamics of the vestibular system

We present a computational study of the fluid dynamics in healthy semicircular canals (SCCs) and the utricle. The SCCs are the primary sensors for angular velocity and are located in the vestibular part of the inner ear. The SCCs are connected to the utricle that hosts the utricular macula, a sensor for linear acceleration. The transduction of angular motion is triggered by the motion of a fluid called endolymph and by the interaction of this fluid with the sensory structures of the SCC. In our computations, we observe a vortical flow in the utricle and in the ampulla (the enlarged terminal part of the SCCs) which can lead to flow velocities in the utricle that are even higher than those in the SCCs. This is a fundamentally new result which is in contrast to the common belief that the fluid velocities in the utricle are negligible from a physiological point of view. Moreover, we show that the wall shear stresses in the utricle and the ampulla are maximized at the positions of the sensory epithelia. Possible physiological and clinical implications are discusse