John Tyndall - zum 150. Jahrestag seiner Ehrenmitgliedschaft in der Naturforschenden Gesellschaft in Zürich

Die Naturforschende Gesellschaft in Zürich verlieh John Tyndall die Ehrenmitgliedschaft. Dies jährt sich 2008 zum 150. Mal. Der irische Physiker und Alpinist ist wohl am besten durch den so genannten «Tyndall-Effekt» bekannt, welcher die Streuung eines Lichtstrahls an feinen Schwebepartikeln in der Luft (oder in einer Lösung) beschreibt. Tyndalls Untersuchungen belegten ausserdem das Vorkommen und den Transport von Mikroorganismen in der Luft, welche sehr heterogen in der Atmosphäre verteilt sind. Als Alpinist beschäftigte er sich auch mit dem Fliessverhalten von Eis und Gletschern. Eine Arbeit dazu wurde 1858 in der Vierteljahrsschrift veröffentlicht

Modifizierung der Struktur und optoelektronischen Eigenschaften durch Mischungsbildung und Druck

An kolumnar-diskotischen Triphenylenderivaten wurde der Einfluß von hydrostatischem Druck und binärer Mischungsbildung auf Struktur und optoelektronischen Eigenschaften der flüssigkristallinen Phase untersucht. Dazu wurden Messungen mittels DSC, Polarisationsmikroskopie,Röntgenstrukturanalyse mit Synchrotronstrahlung, UV-VIS-Spektroskopie unter Druck und an orientierten Proben und DK-Messungen durchgeführt. Die Kompressibilitäten der flüssigkristallinen Phase wurden aus dem Experiment berechnet. Unter anderem hatte die binäre Mischungsbildung einen Einfluß auf die Morphologie und die Kristallisation der Triphenylene

NGC 3603 - a Local Template for Massive Young Clusters

We present a study of the star cluster associated with the massive Galactic HII region NGC3603 based on near-IR broad-- and narrowband observations taken with ISAAC/VLT under excellent seeing conditions (<0.4''). We discuss color-color diagrams and address the impact of the high UV flux on the disk evolution of the low-mass stars.Comment: 3 pages, 3 figures. To appear in the Proceedings of IAU Symposium 207 "Extragalactic Star Clusters", eds. E. Grebel, D. Geisler and D. Minitt

Green's Relations in Finite Transformation Semigroups

We consider the complexity of Green's relations when the semigroup is given by transformations on a finite set. Green's relations can be defined by reachability in the (right/left/two-sided) Cayley graph. The equivalence classes then correspond to the strongly connected components. It is not difficult to show that, in the worst case, the number of equivalence classes is in the same order of magnitude as the number of elements. Another important parameter is the maximal length of a chain of components. Our main contribution is an exponential lower bound for this parameter. There is a simple construction for an arbitrary set of generators. However, the proof for constant alphabet is rather involved. Our results also apply to automata and their syntactic semigroups.Comment: Full version of a paper submitted to CSR 2017 on 2016-12-1

Mid-Infrared Instrumentation for the European Extremely Large Telescope

MIDIR is the proposed thermal/mid-IR imager and spectrograph for the European Extremely Large Telescope (E-ELT). It will cover the wavelength range of 3 to at least 20 microns. Designed for diffraction-limited performance over the entire wavelength range, MIDIR will require an adaptive optics system; a cryogenically cooled system could offer optimal performance in the IR, and this is a critical aspect of the instrument design. We present here an overview of the project, including a discussion of MIDIR's science goals and a comparison with other infrared (IR) facilities planned in the next decade; top level requirements derived from these goals are outlined. We describe the optical and mechanical design work carried out in the context of a conceptual design study, and discuss some important issues to emerge from this work, related to the design, operation and calibration of the instrument. The impact of telescope optical design choices on the requirements for the MIDIR instrument is demonstrated.Comment: for publication in SPIE Proceedings vol. 6692, Cryogenic Optical Systems and Instrumentation XII, eds. J.B. Heaney and L.G. Burriesci, San Diego, Aug 200

Adoption, Fostering, and Parental Absence in Vanuatu

Alloparenting, wherein people provide care to children who are not their biological offspring, is a key aspect of human child-rearing. In the Pacific, many children are adopted or fostered by custodial alloparents even when both biological parents are still alive. From a behavioral ecology perspective, such behaviors are puzzling: why parent someone else's child at your expense? Furthermore, little is known about how these arrangements are made in Pacific Islander societies today, who provides care, and what kinds of outcomes fostered children experience. A better understanding of these proximate factors may help reveal the ultimate drivers behind custodial alloparenting. Here, we report findings from a survey carried out with the caregivers of 282 children in rural areas of Vanuatu, an island nation in Melanesia. Most fostered and adopted children lived with relatives such as aunts, uncles, and grandparents (87.5%) rather than unrelated caregivers, with a strong preference for maternal kin. The most common reasons for these arrangements were that the parents had separated (16.7%), were engaging in labor migration (27.1%), or a combination of both (27.1%). Results for investment in children's education and their educational outcomes were mixed, although children removed from crisis situations did more poorly than children removed for aspirational reasons. Our findings suggest that custodial alloparenting helps families adapt to socioeconomic transitions and changing marriage practices. Outcomes may depend on a range of factors, such as the reason children were transferred out of the natal home to begin with

Development of teaching in ni-Vanuatu children

Teaching is an important mechanism of social learning. In industrialized societies, 3-year-olds tend to teach through demonstrations and short commands, while 5-year-olds use more verbal communication and abstract explanations. However, it remains unclear whether this generalizes to other cultures. This study presents results from a peer teaching game with 55 Melanesian children (4.7-11.4 years, 24 female) conducted in Vanuatu in 2019. Up to age 8, most participants taught through a participatory approach, emphasizing learning-by-doing, demonstrations, and short commands (57.1% of children aged 4-6 and 57.9% of children aged 7-8). Contrary to Western findings, abstract verbal communication only became common in children aged 9-11 (63.6%), suggesting that the ontogeny of teaching is shaped by the socio-cultural environment

Indomethacin decreases viscosity of gallbladder bile in patients with cholesterol gallstone disease

There is experimental evidence that inhibition of cyclooxygenase with nonsteroidal anti-inflammatory drugs may decrease cholesterol gall-stone formation and mitigate biliary pain in gall-stone patients. The mechanisms by which NSAIDs exert these effect are unclear. In a prospective, controlled clinical trial we examined the effects of oral indomethacin on the composition of human gall-bladder bile. The study included 28 patients with symptomatic cholesterol or mixed gallstones. Of these, 8 were treated with 3 × 25 mg indomethacin daily for 7 days prior to elective cholecystectomy while 20 received no treatment and served as controls. Bile and tissue samples from the gallbladder were obtained during cholecystectomy. Indomethacin tissue levels in the gallbladder mucosa, as assessed by HPLC, were 1.05±0.4 ng/mg wet weight, a concentration known to inhibit effectively cyclooxygenase activity. Nevertheless, no differences between the treated and untreated groups were found in the concentrations of biliary mucus glycoprotein (0.94±0.27 versus 0.93±0.32 mg/ml) or total protein (5.8±0.9 versus 6.4±1.3 mg/ml), cholesterol saturation (1.3±0.2 versus 1.5±0.2), or nucleation time (2.0±3.0 versus 1.5±2.0 days). However, biliary viscosity, measured using a low-shear rotation viscosimeter, was significantly lower in patients receiving indomethacin treatment (2.9±0.6 versus 5.6±1.2 mPa.s; P < 0.02). In conclusion, in man oral indomethacin decreases bile viscosity without alteration of bile lithogenicity or biliary mucus glycoprotein content. Since mucus glycoproteins are major determinants of bile viscosity, an alteration in mucin macromolecular composition may conceivably cause the indomethacin-induced decrease in biliary viscosity and explain the beneficial effects of nonsteroidal anti-inflammatory drugs in gallstone disease