Dust dynamics and distribution in protoplanetary disks

Feinkörniger Staub ist der grundlegende Baustein von terrestrischen Planeten wie der Erde, die um junge Sterne entstehen. Gleichzeitig beeinflusst der Staub astronomische Beobachtungen, da er den Hauptbeitrag zur Opazität in den Gasscheiben leistet, die entstehende Sterne umgeben (sog. protoplanetare Scheiben). Daher sind genaue Modelle der Verteilung und Bewegung von Staub in protoplanetaren Scheiben von entscheidender Bedeutung für das Verständnis der Anfangsbedingungen der Planetenentstehung und für die Interpretation astronomischer Beobachtungen von jungen Planeten- und Sternensystemen. Dieses Thema ist besonders relevant, da neueste astronomischen Beobachtungen protoplanetarer Scheiben neue Maßstäbe in Bezug auf Auflösung und Empfindlichkeit setzen und dadurch unser derzeitiges Verständnis und unsere Modelle infrage stellen. In dieser Arbeit präsentiere ich ein neuartiges und in sich konsistentes Modell der turbulenten Durchmischung von Staub. Das Modell bestätigt detaillierte Vorhersagen, wobei Nachteile früherer Modelle hinsichtlich der Drehimpulserhaltung, der uneindeutigen Definition der durchmischten Größe und Auswirkungen der Bahndynamik wegfallen. Somit verbessern wir die Beschreibung der Bewegung von Staub in turbulenten protoplanetaren Scheiben maßgeblich. Anschließend zeige ich auf, wie turbulente Durchmischung von Staub und andere Transportphänomene im frühen Sonnensystem, den Mangel an beständigen Kohlenstoffverbindungen, im inneren Bereich des heutigen Sonnensystems erklären kann. Im Folgenden konzentriert sich die Arbeit auf die dreidimensionale Verteilung des Staubs in protoplanetaren Scheiben in Gegenwart eines Riesenplaneten. Mithilfe von hydrodynamischen Zwei-Fluid-Simulationen (Gas + Staub) finden wir, dass ein Planet die Staubverteilung in protoplanetaren Scheiben stark beeinflusst. Wir beschreiben beobachtbare Merkmale in synthetischen Radiowellenbeobachtungen, die es erlauben, auf die Anwesenheit eines unentdeckten Riesenplaneten in einer protoplanetaren Scheibe zu schließen. Schließlich untersuchen wir die Verwirbelung von Staub durch einen Riesenplaneten, zusätzlich zur Durchmischung durch turbulentes Gas. Wir konzentrieren uns dabei auf deren kombinierte Wirkung auf die dreidimensionale Verteilung des Staubs und untersuchen Merkmale, die mit Radiowellenbeobachtungen einer protoplanetarer Scheibe beobachtbar sind und Rückschlüsse auf die Anwesenheit eines noch unentdeckten Planeten erlauben. Diese Arbeit bietet neue Einblicke in die Dynamik von Staub in turbulenten protoplanetaren Scheiben und liefert eine Erklärung für den Mangel an beständigen Kohlenstoffverbindungen im inneren Sonnensystem. Außerdem beschreiben wir mögliche beobachtbare Merkmale von noch unentdeckten Riesenplaneten in Radiowellenbeobachtungen von protoplanetaren Scheiben.Fine-grained dust is the fundamental building block of terrestrial planets, like Earth, that form around young stars. At the same time, the dust distribution in the gaseous disks around forming stars, so-called protoplanetary disks, influences astronomical observations, because dust is the main contributor to the opacity in protoplanetary disks. Therefore, accurate models of the distribution and dynamics of dust are critical to understanding the initial stages of planet formation and interpreting astronomical observations of forming planetary and stellar systems. This is particularly relevant because recent astronomical observations of protoplanetary disks have reached new heights in terms of resolution and sensitivity, challenging our current understanding and models. In this thesis, I introduce a novel and self-consistent turbulent dust transport model based on a density-weighted mean-field theory that also captures non-local transport effects. The model improves upon the limitations of earlier models related to the conservation of angular momentum, the ambiguous nature of the transported quantity, and the transport effects of orbital dynamics. We therefore provide an improved description of dust dynamics in turbulent protoplanetary disks. Subsequently, I present how turbulent dust dynamics and transport in the early Solar System can explain the lack of refractory carbon in the inner Solar System today. The thesis then focuses on the three-dimensional dust distribution in protoplanetary disks in the presence of an embedded giant planet. With the help of radiative two-fluid (gas+dust) hydrodynamic simulations, we find that a planet significantly influences the dust distribution in protoplanetary disks. We identify observational signatures in synthetic radio continuum observations that hint at the potential presence of a yet undetected giant planet in a protoplanetary disk. Finally, we investigate dust stirring by a giant planet in addition to dust mixing caused by turbulent gas. We focus on the combined effects on the three-dimensional dust morphology and study observable effects of turbulent and planetary dust stirring in radio continuum observations of protoplanetary disks with an embedded planet. Our work provides novel insights into turbulent dust dynamics in protoplanetary disks and offers an explanation for the lack of refractory carbon in the inner Solar System. We also describe observational signatures of giant planets in protoplanetary disks that help with the interpretation of continuum observations. These results help guide astronomers toward the detection of forming and yet unobserved planets in protoplanetary disks

Beyond Diffusion: A Generalized Mean-Field Theory of Turbulent Dust Transport in Protoplanetary Disks

Turbulence in protoplanetary disks, when present, plays a critical role in transporting dust particles embedded in the gaseous disk component. When using a field description of dust dynamics, a diffusion approach is traditionally used to model this turbulent dust transport. However, it has been shown that classical turbulent diffusion models are not fully self-consistent. Several shortcomings exist, including the ambiguous nature of the diffused quantity and the nonconservation of angular momentum. Orbital effects are also neglected without an explicit prescription. In response to these inconsistencies, we present a novel Eulerian turbulent dust transport model for isotropic and homogeneous turbulence on the basis of a mean-field theory. Our model is based on density-weighted averaging applied to the pressureless fluid equations and uses appropriate turbulence closures. Our model yields novel dynamic equations for the turbulent dust mass flux and recovers existing turbulent transport models in special limiting cases, thus providing a more general and self-consistent description of turbulent particle transport. Importantly, our model ensures the conservation of global angular and linear momentum unconditionally and implicitly accounts for the effects of orbital dynamics in protoplanetary disks. Furthermore, our model correctly describes the vertical settling-diffusion equilibrium solutions for both small and large particles. Hence, this work presents a generalized Eulerian turbulent dust transport model, establishing a comprehensive framework for more detailed studies of turbulent dust transport in protoplanetary disks.Comment: Submitted to MNRA

Fine-grained timing using genetic programming

In previous work, we have demonstrated that it is possible to use Genetic Programming to minimise the resource consumption of software, such as its power consumption or execution time. In this paper, we investigate the extent to which Genetic Programming can be used to gain fine-grained control over software timing. We introduce the ideas behind our work, and carry out experimentation to find that Genetic Programming is indeed able to produce software with unusual and desirable timing properties, where it is not obvious how a manual approach could replicate such results. In general, we discover that Genetic Programming is most effective in controlling statistical properties of software rather than precise control over its timing for individual inputs. This control may find useful application in cryptography and embedded systems

Pflegerische Interventionen zur Schmerzreduktion während Venenpunktionen bei Kindern

Einleitung: In der Kindheit werden die ersten Schmerzerfahrungen gemacht. Zu den schmerzhaftesten dabei zählt die Venenpunktion. Um zukünftige Schmerzerfahrungen positiv zu beeinflussen, muss eine altersgerechte, der Entwicklung angepasste, schmerzlindernde Methode gewählt werden. Zur Optimierung des Schmerzmanagements bei Kindern sollen nicht-pharmakologische Interventionen gefördert werden. Fragestellung: Welche schmerzlindernden nicht-pharmakologischen Interventionen bei Kindern zwischen 2 und 12 Jahren können während Venenpunktionen im akuten Setting von Pflegefachpersonen angewendet werden? Methoden: Es wurde eine Literaturrecherche in den Datenbanken CINAHL, Cochrane Library und PubMed durchgeführt. Neun ausgewählte Studien waren geeignet und wurden analysiert und miteinander verglichen. Ergebnisse: Sechs Studien zu kognitiven Verhaltenstechniken und drei Studien zu physikalischen Interventionen wurden gefunden. All diese Studien zeigen Ansätze zur erfolgreichen Anwendung nicht-pharmakologischer Interventionen im Pflegealltag, die zu einer Schmerzreduktion beitragen. Schlussfolgerung: Obwohl wirksame schmerzlindernde nicht-pharmakologische Interventionen gefunden wurden, wird weitere Forschung empfohlen. Wichtig ist, dass sich die Interventionen einfach und schnell in der Pflegepraxis umsetzen lassen. Die meisten Interventionen sind mit wenig Adaption gut auf das schweizerische Gesundheitssystem übertragbar

Perception of Sunflecks by the UV-B Photoreceptor UV RESISTANCE LOCUS8

Sunflecks, transient patches of light that penetrate through gaps in the canopy and transiently interrupt shade, are eco-physiologically and agriculturally important sources of energy for carbon gain, but our molecular understanding of how plant organs perceive and respond to sunflecks through photoreceptors remains limited. The UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8) is a recent addition to the list of plant photosensory receptors, and we have made considerable advances in our understanding of the physiology and molecular mechanisms of action of UVR8 and its signaling pathway. However, the function of UVR8 in the natural environment is poorly understood. Here, we show that the UVR8 dimer/monomer ratio responds quantitatively and reversibly to the intensity of sunflecks that interrupt shade in the field. Sunflecks reduced hypocotyl growth and increased CHALCONE SYNTHASE (CHS) and ELONGATED HYPOCOTYL5 gene expression and CHS protein abundance in wild-type Arabidopsis (Arabidopsis thaliana) seedlings, but the uvr8 mutant was impaired in these responses. UVR8 was also required for normal nuclear dynamics of CONSTITUTIVELY PHOTOMORPHOGENIC1. We propose that UVR8 plays an important role in the plant perception of and response to sunflecks.Fil: Moriconi, Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Binkert, Melanie. Universidad de Ginebra; SuizaFil: Costigliolo Rojas, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ulm, Roman. Universidad de Ginebra. Facultad de Ciencias; SuizaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Meridional Circulation of Dust and Gas in the Circumstellar Disk: Delivery of Solids onto the Circumplanetary Region

We carried out 3D dust+gas radiative hydrodynamic simulations of forming planets. We investigated a parameter grid of Neptune-, Saturn-, Jupiter-, and 5 Jupiter-mass planets at 5.2, 30, 50 AU distance from their star. We found that the meridional circulation \citep{Szulagyi14,FC16} drives a strong vertical flow for the dust as well, hence the dust is not settled in the midplane, even for mm-sized grains. The meridional circulation will deliver dust and gas vertically onto the circumplanetary region, efficiently bridging over the gap. The Hill-sphere accretion rates for the dust are $\sim10^{-8}$ to $10^{-10}$ $\rm{M_{Jup}/yr}$, increasing with planet-mass. For the gas component, the gain is $10^{-6}$ to $10^{-8}$ $\rm{M_{Jup}/yr}$. The difference between the dust and gas accretion rates is smaller with decreasing planetary mass. In the vicinity of the planet, the mm-grains can get trapped easier than the gas, which means the circumplanetary disk might be enriched with solids in comparison to the circumstellar disk. We calculated the local dust-to-gas ratio (DTG) everywhere in the circumstellar disk and identified the altitude above the midplane where the DTG is 1, 0.1, 0.01, 0.001. The larger the planetary mass, the higher the mm-sized dust is delivered and a larger fraction of the dust disk is lifted by the planet. The stirring of mm-dust is negligible for Neptune-mass planets or below, but significant above Saturn-mass.Comment: ApJ accepte

Impact of prenatal diganosis on the prevalence of live births with Down sysndrome in the eastern half of Switzerland 1980-1996

Objectives and methods: To investigate the impact of prenatal diagnosis on trisomy 21 live births, we collected all prenatal and postnatal trisomy 21 cases (n = 1096) in the eastern half of Switzerland for the years 1980-1996. Results: Despite increasing prenatal detection rates of trisomy 21 foetuses (an increase of 169% in the last 5 versus the first 5 years of the study period) and subsequent termination of pregnancies, the number of liveborn Down syndrome children remained constant. The reason is a shift towards a higher mean maternal age from 28 to 30 years between 1980 and 1996. If mean maternal age at delivery was considered, the observed increase of trisomy 21 conceptions matched well with the calculated figures. Conclusion: If the tendency to have pregnancies at a more advanced age continues and if the use of prenatal diagnosis does not increase, an increase in incidence of Down syndrome liveborns may be expected in the first decades of the 21st century

First 3-D grid-based gas-dust simulations of circumstellar disks with an embedded planet

Substructures are ubiquitous in high resolution (sub-)millimeter continuum observations of circumstellar disks. They are possibly caused by forming planets embedded in the disk. To investigate the relation between observed substructures and young planets, we perform novel three-dimensional two-fluid (gas+1-mm-dust) hydrodynamic simulations of circumstellar disks with embedded planets (Neptune-, Saturn-, Jupiter-, 5 Jupiter-mass) at different orbital distances from the star (5.2AU, 30AU, 50AU). We turn these simulations into synthetic (sub-)millimeter ALMA images. We find that all but the Neptune-mass planet open annular gaps in both the gas and the dust component of the disk. We find that the temporal evolution of the dust density distribution is distinctly different of the gas'. For example, the planets cause significant vertical stirring of the dust in the circumstellar disk which opposes the vertical settling. This creates a thicker dust disk than disks without a planet. We find that this effect greatly influences the dust masses derived from the synthetic ALMA images. Comparing the dust disk masses in the 3D simulations and the ones derived from the 2D ALMA synthetic images, we find the former to be a factor of a few (up to 10) larger, pointing to that real disks might be significantly more massive than previously thought based on ALMA continuum images using the optically thin assumption and equation. Finally, we analyze the synthetic ALMA images and provide an empirical relationship between the planet mass and the width of the gap in the ALMA images including the effects of the beam size.Comment: 21 pages, 11 figures, accepted for publication in MNRA

Zystische Adventitiadegeneration (CAD) als Ursache einer invalidisierenden Claudicatio intermittens

Zusammenfassung: Bei einem 45-jährigen Patienten mit wechselhaften Ischämiebeschwerden und initial limitierter Gehstrecke rechts von höchstens 50m führten die duplexsonographischen und angiographischen Abklärungen zur Verdachtsdiagnose einer zystischen Adventitiadegeneration. Intraoperativ zeigte sich ein zystisch aufgetriebenes Poplitealsegment mit Entleerung von gallertiger Flüssigkeit. Aufgrund der langstreckigen Veränderung erfolgte die Segmentresektion der A.poplitea und Rekonstruktion mittels eines autologen Veneninterponats. Die CAD ist ein seltenes Krankheitsbild, an das gerade bei jungen Patienten ohne systemische Arteriosklerose gedacht werden sollte. Die Therapie ist je nach Fall chirurgisch erhaltend durch Zystenresektion mittels "Exarterektomie" oder gefäßresezierend, insbesondere bei langstreckigen Veränderungen bzw. vollständiger Okklusion mittels Ersatz durch ein Veneninterpona