BONNSAI: a Bayesian tool for comparing stars with stellar evolution models

Powerful telescopes equipped with multi-fibre or integral field spectrographs combined with detailed models of stellar atmospheres and automated fitting techniques allow for the analysis of large number of stars. These datasets contain a wealth of information that require new analysis techniques to bridge the gap between observations and stellar evolution models. To that end, we develop BONNSAI (BONN Stellar Astrophysics Interface), a Bayesian statistical method, that is capable of comparing all available observables simultaneously to stellar models while taking observed uncertainties and prior knowledge such as initial mass functions and distributions of stellar rotational velocities into account. BONNSAI can be used to (1) determine probability distributions of fundamental stellar parameters such as initial masses and stellar ages from complex datasets, (2) predict stellar parameters that were not yet observationally determined and (3) test stellar models to further advance our understanding of stellar evolution. An important aspect of BONNSAI is that it singles out stars that cannot be reproduced by stellar models through $\chi^{2}$ hypothesis tests and posterior predictive checks. BONNSAI can be used with any set of stellar models and currently supports massive main-sequence single star models of Milky Way and Large and Small Magellanic Cloud composition. We apply our new method to mock stars to demonstrate its functionality and capabilities. In a first application, we use BONNSAI to test the stellar models of Brott et al. (2011a) by comparing the stellar ages inferred for the primary and secondary stars of eclipsing Milky Way binaries. Ages are determined from dynamical masses and radii that are known to better than 3%. We find that the stellar models reproduce the Milky Way binaries well. BONNSAI is available through a web-interface at http://www.astro.uni-bonn.de/stars/bonnsai.Comment: Accepted for publication in A&A; 15 pages, 10 figures, 4 tables; BONNSAI is available through a web-interface at http://www.astro.uni-bonn.de/stars/bonnsa

Ефективність симбіотичної азотфіксації в агроценозах України

Проведено порівняльну оцінку ефективності виробничих і перспективних штамів бульбочкових бактерій колекції Південної дослідної станції ІСГМ УААН у симбіозі з сучасними сортами бобових культур. Визначені високоефективні комбінації “сорти – штами”. Показано доцільність передпосівної інокуляції насіння бобових культур на фоні ґрунтової популяції ризобій.Проведена сравнительная оценка эффективности производственных и перспективных штаммов клубеньковых бактерий коллекции Южной опытной станции ИСХМ УААН в симбиозе с современными сортами бобовых культур. Определены высокоэффективные комбинации “сорта – штаммы”. Показана целесообразность предпосевной инокуляции семян бобовых культур на фоне почвенной популяции ризобий.The comparative estimation of rhisobia strains (from the collection of the Southern Experimental Station of Institute of Agricultural Microbiology UAAS) efficiency in symbiosis with modern legume cultivars was done. Highly effective complemented „cultivars – strains” combinations have been determined. It was shown the expediency of legume seeds pre-sowing treatment on background of soil rhisobia population

Implication of the overlap representation for modelling generalized parton distributions

Based on a field theoretically inspired model of light-cone wave functions, we derive valence-like generalized parton distributions and their double distributions from the wave function overlap in the parton number conserved s-channel. The parton number changing contributions in the t-channel are restored from duality. In our construction constraints of positivity and polynomiality are simultaneously satisfied and it also implies a model dependent relation between generalized parton distributions and transverse momentum dependent parton distribution functions. The model predicts that the t-behavior of resulting hadronic amplitudes depends on the Bjorken variable x_Bj. We also propose an improved ansatz for double distributions that embeds this property.Comment: 15 pages, 8 eps figure

Surface Phase Transitions Induced by Electron Mediated Adatom-Adatom Interaction

We propose that the indirect adatom-adatom interaction mediated by the conduction electrons of a metallic surface is responsible for the $\sqrt{3}\times \sqrt{3}\Leftrightarrow 3\times 3$ structural phase transitions observed in Sn/Ge (111) and Pb/Ge (111). When the indirect interaction overwhelms the local stress field imposed by the substrate registry, the system suffers a phonon instability, resulting in a structural phase transition in the adlayer. Our theory is capable of explaining all the salient features of the $\sqrt{3}\times \sqrt{3}\Leftrightarrow 3\times 3$ transitions observed in Sn/Ge (111) and Pb/Ge (111), and is in principle applicable to a wide class of systems whose surfaces are metallic before the transition.Comment: 4 pages, 5 figure

Monitoring bridge degradation using dynamic strain, acoustic emission and environmental data

This paper studies the long term structural behaviour of a Victorian railway viaduct under train loading and temperature variation. A multi-sensing, self-sustaining and remotely controlled data acquisition system combines fibre Bragg grating strain sensors with acoustic emission sensors for the study of both global dynamic deformation and local masonry deterioration. A statistical analysis of fibre Bragg grating signals reveals regions with permanent change in the dynamic deformation of the bridge over the last two years, whereas in other locations the deformation follows a seasonal cyclic pattern. In order to decouple changes in structural behaviour due to real mechanical damage from normal seasonal effect, the paper studies the ambient temperature effect on the dynamic deformation of the bridge, showing a clear linear dependence. In particular, when temperature increases, the dynamic strain due to train loading decreases uniformly in the longitudinal direction. In the transverse direction, where the thermal expansion is not constrained, the decrease is smaller. Decoupling damage from normal seasonal effect is of critical importance for the development of reliable early warning structural alert systems for infrastructure networks. The paper further studies local masonry deterioration at four critical location by combining data from the two sensing technologies: fibre optic and acoustic emission sensors.This work is being funded by the Lloyd’s Register Foundation, EPSRC and Innovate UK through the Data-Centric Engineering programme of the Alan Turing Institute and through the Cambridge Centre for Smart Infrastructure and Construction. Funding for the monitoring installation was provided by EPSRC under the Ref. EP/N021614/1 grant and by Innovate UK under the Ref. 920035 grant

Neuropsychological consequences for survivors of childhood brain tumor in Malaysia

FSW - Self-regulation models for health behavior and psychopathology - ou