Marginalising instrument systematics in HST WFC3 transit lightcurves

Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7$\mu$m probe primarily the H$_2$O absorption band at 1.4$\mu$m, and has provided low resolution transmission spectra for a wide range of exoplanets. We present the application of marginalisation based on Gibson (2014) to analyse exoplanet transit lightcurves obtained from HST WFC3, to better determine important transit parameters such as R$_p$/R$_*$, important for accurate detections of H$_2$O. We approximate the evidence, often referred to as the marginal likelihood, for a grid of systematic models using the Akaike Information Criterion (AIC). We then calculate the evidence-based weight assigned to each systematic model and use the information from all tested models to calculate the final marginalised transit parameters for both the band-integrated, and spectroscopic lightcurves to construct the transmission spectrum. We find that a majority of the highest weight models contain a correction for a linear trend in time, as well as corrections related to HST orbital phase. We additionally test the dependence on the shift in spectral wavelength position over the course of the observations and find that spectroscopic wavelength shifts $\delta_\lambda(\lambda)$, best describe the associated systematic in the spectroscopic lightcurves for most targets, while fast scan rate observations of bright targets require an additional level of processing to produce a robust transmission spectrum. The use of marginalisation allows for transparent interpretation and understanding of the instrument and the impact of each systematic evaluated statistically for each dataset, expanding the ability to make true and comprehensive comparisons between exoplanet atmospheres.Comment: 19 pages, 13 figures, 8 tables, Accepted to Ap

On the interaction between corrosion and fatigue which determines the remaining life of bridges

This paper studies the combined effect of corrosion and fatigue on the growth of cracks that arise from natural corrosion in steel bridges. It is shown that if these two effects need to be simultaneously analysed. If not then the resulting life is not conservative. Consequently, to enable a better understanding of the remaining life of steel bridges this paper presents a simple methodology for performing this coupled analysis

Photoemission of a doped Mott insulator: spectral weight transfer and qualitative Mott-Hubbard description

The spectral weight evolution of the low-dimensional Mott insulator TiOCl upon alkali-metal dosing has been studied by photoelectron spectroscopy. We observe a spectral weight transfer between the lower Hubbard band and an additional peak upon electron-doping, in line with quantitative expectations in the atomic limit for changing the number of singly and doubly occupied sites. This observation is an unconditional hallmark of correlated bands and has not been reported before. In contrast, the absence of a metallic quasiparticle peak can be traced back to a simple one-particle effect.Comment: 4 pages, 4 figures, related theoretical work can be found in arXiv:0905.1276; shortene

Corrigendum to "The upper atmosphere of the exoplanet HD209458b revealed by the sodium D lines: Temperature-pressure profile, ionization layer and thermosphere" [2011, A&A, 527, A110]

An error was detected in the code used for the analysis of the HD209458b sodium profile (Vidal-Madjar et al. 2011). Here we present an updated T-P profile and briefly discuss the consequences.Comment: Published in Astronomy & Astrophysics, 533, C

Influence of Anisotropy on Creep in a Whisker Reinforced MMC Rotating Disc

Whisker reinforced MMC may be employed in rotating disc , a common component in friction drives , turbines and a number of other machine components, often exposed to elevated temperatures . Creep characteristics of these composites have been studied analytically using von Mises flow rule and Norton 's steady state creep equations . The results for isotropic A16061 alloy and for isotropic composite containing 20 vol% SiCµ in a matrix of A16061 alloy have been compared with those obtained for anisotropic composites with characteristic parameters a = 0.7 and 1. 31, indicating respectively relative strengthening and weakening in the tangential direction presumably introduced by either processing or inhomogeneous distribution of reinforcement.The creep strain rates resulting in the isotropic rotating disc made of composite as well as the aluminum alloy, are tensile in the tangential direction but compressive in the axial and radial directions, also conforming to the condition of volume constancy.The creep rates in the composite are significantly reduced (by about three orders of magnitude) in all the directions compared to those observed in the base alloy. In case of anisotropy lowering the strength in the tangential direction (a> 1.0), the radial stresses in the region near inner periphery of the disc, increase while those near the outer periphery decrease in comparison to those for the isotropic composite . But the tangential stresses reduce in the middle region of the disc and enhances near the inner and the outer periphery, when compared to those for the isotropic composite . The magnitude of stress distribution , however, changes by a small extent due to ani sotropy in the disc introduced through processing or reinforcement distribution . The radial strain rate which always remained compressive for the isotropic composite and for a = 1.3,becomes tensile in the middle region of the disc when a = 0.7. If a is reduced from 1.3 to 0 . 7, the variation of tensile strain rate in the tangential direction remains similar but the magnitude reduces by five orders of magnitude . Anisotropy therefore, introduces significant change in the strain rates although its effect on the resulting stress distribution may be relatively small

A note on the realignment criterion

For a quantum state in a bipartite system represented as a density matrix, researchers used the realignment matrix and functions on its singular values to study the separability of the quantum state. We obtain bounds for elementary symmetric functions of singular values of realignment matrices. This answers some open problems proposed by Lupo, Aniello, and Scardicchio. As a consequence, we show that the proposed scheme by these authors for testing separability would not work if the two subsystems of the bipartite system have the same dimension.Comment: 11 pages, to appear in Journal of Physics A: Mathematical and Theoretica

Are the renormalized band widths in TTF-TCNQ of structural or electronic origin? - An angular dependent NEXAFS study

We have performed angle-dependent near-edge x-ray absorption fine structure measurements in the Auger electron yield mode on the correlated quasi-one-dimensional organic conductor TTF-TCNQ in order to determine the orientation of the molecules in the topmost surface layer. We find that the tilt angles of the molecules with respect to the one-dimensional axis are essentially the same as in the bulk. Thus we can rule out surface relaxation as the origin of the renormalized band widths which were inferred from the analysis of photoemission data within the one-dimensional Hubbard model. Thereby recent theoretical results are corroborated which invoke long-range Coulomb repulsion as alternative explanation to understand the spectral dispersions of TTF-TCNQ quantitatively within an extended Hubbard model.Comment: 6 pages, 5 figure