Quantitative chemical analysis of perovskite deposition using spin coating

Lead and halide ion compositions of spin coated organo-lead halide perovskite films have been quantified using ion chromatography (IC) and atomic absorption spectroscopy (AAS) using perovskite films manufactured by 5 different researchers (3 replicates per treatment) to monitor variability between researchers and individual researcher reproducibility. Planar and mesoporous TiO2-coated glass substrates have been studied along with tribromide (CH3NH3PbBr3), triiodide (CH3NH3PbI3) and mixed halide (CH3NH3PbI3�xClx) perovskite films. The data show low yields of spin coated perovskite material (ca. 1%) and preferential deposition of I� over Cl� in mixed halide films

The spectrum of HM Sagittae: A planetary nebula excited by a Wolf-Rayet star

A total of image tube spectrograms of HM Sagittae were obtained. More than 70 emission lines, including several broad emission features, were identified. An analysis of the spectra indicates that HM Sagittae is a planetary nebula excited by a Wolf-Rayet star. The most conspicuous Wolf-Rayet feature is that attributed to a blend of C III at 4650 A and He II at 4686 A

Interferometric Studies of Interstellar Calcium Lines

Interferometric, photoelectric scans of the interstellar calcium K-lines in the spectra of 65 stars are presented. The scans were obtained with a PEPSIOS spectrometer having a passband with a full half-intensity width of 1.0 kms(-1) or 0.013A. The fivefold improvement in resolution over that used by Adams reveals numerous line components which correspond very well to those of the interstellar sodium lines, apart from frequent differences in relative intensities

A conjugate gradient algorithm for the astrometric core solution of Gaia

The ESA space astrometry mission Gaia, planned to be launched in 2013, has been designed to make angular measurements on a global scale with micro-arcsecond accuracy. A key component of the data processing for Gaia is the astrometric core solution, which must implement an efficient and accurate numerical algorithm to solve the resulting, extremely large least-squares problem. The Astrometric Global Iterative Solution (AGIS) is a framework that allows to implement a range of different iterative solution schemes suitable for a scanning astrometric satellite. In order to find a computationally efficient and numerically accurate iteration scheme for the astrometric solution, compatible with the AGIS framework, we study an adaptation of the classical conjugate gradient (CG) algorithm, and compare it to the so-called simple iteration (SI) scheme that was previously known to converge for this problem, although very slowly. The different schemes are implemented within a software test bed for AGIS known as AGISLab, which allows to define, simulate and study scaled astrometric core solutions. After successful testing in AGISLab, the CG scheme has been implemented also in AGIS. The two algorithms CG and SI eventually converge to identical solutions, to within the numerical noise (of the order of 0.00001 micro-arcsec). These solutions are independent of the starting values (initial star catalogue), and we conclude that they are equivalent to a rigorous least-squares estimation of the astrometric parameters. The CG scheme converges up to a factor four faster than SI in the tested cases, and in particular spatially correlated truncation errors are much more efficiently damped out with the CG scheme.Comment: 24 pages, 16 figures. Accepted for publication in Astronomy & Astrophysic

Constraining the coalescence rate of supermassive black-hole binaries using pulsar timing

Pulsar timing observations are used to place constraints on the rate of coalescence of supermassive black-hole (SMBH) binaries as a function of mass and redshift. In contrast to the indirect constraints obtained from other techniques, pulsar timing observations provide a direct constraint on the black-hole merger rate. This is possible since pulsar timing is sensitive to the gravitational waves (GWs) emitted by these sources in the final stages of their evolution. We find that upper bounds calculated from the recently published Parkes Pulsar Timing Array data are just above theoretical predictions for redshifts below 10. In the future, with improved timing precision and longer data spans, we show that a non-detection of GWs will rule out some of the available parameter space in a particular class of SMBH binary merger models. We also show that if we can time a set of pulsars to 10ns timing accuracy, for example, using the proposed Square Kilometre Array, it should be possible to detect one or more individual SMBH binary systems

Optimal discrete stopping times for reliability growth tests

Often, the duration of a reliability growth development test is specified in advance and the decision to terminate or continue testing is conducted at discrete time intervals. These features are normally not captured by reliability growth models. This paper adapts a standard reliability growth model to determine the optimal time for which to plan to terminate testing. The underlying stochastic process is developed from an Order Statistic argument with Bayesian inference used to estimate the number of faults within the design and classical inference procedures used to assess the rate of fault detection. Inference procedures within this framework are explored where it is shown the Maximum Likelihood Estimators possess a small bias and converges to the Minimum Variance Unbiased Estimator after few tests for designs with moderate number of faults. It is shown that the Likelihood function can be bimodal when there is conflict between the observed rate of fault detection and the prior distribution describing the number of faults in the design. An illustrative example is provided