When Darwin Met Einstein: Gravitational Lens Inversion with Genetic Algorithms

Gravitational lensing can magnify a distant source, revealing structural detail which is normally unresolvable. Recovering this detail through an inversion of the influence of gravitational lensing, however, requires optimisation of not only lens parameters, but also of the surface brightness distribution of the source. This paper outlines a new approach to this inversion, utilising genetic algorithms to reconstruct the source profile. In this initial study, the effects of image degradation due to instrumental and atmospheric effects are neglected and it is assumed that the lens model is accurately known, but the genetic algorithm approach can be incorporated into more general optimisation techniques, allowing the optimisation of both the parameters for a lensing model and the surface brightness of the source.Comment: 9 pages, to appear in PAS

Toward Eclipse Mapping of Hot Jupiters

Recent Spitzer infrared measurements of hot Jupiter eclipses suggest that eclipse mapping techniques could be used to spatially resolve the day-side photospheric emission of these planets using partial occultations. As a first step in this direction, we simulate ingress/egress lightcurves for the three brightest known eclipsing hot Jupiters and evaluate the degree to which parameterized photospheric emission models can be distinguished from each other with repeated, noisy eclipse measurements. We find that the photometric accuracy of Spitzer is insufficient to use this tool effectively. On the other hand, the level of photospheric details that could be probed with a few JWST eclipse measurements could greatly inform hot Jupiter atmospheric modeling efforts. A JWST program focused on non-parametric eclipse map inversions for hot Jupiters should be actively considered.Comment: 32 pages, 6 figures, 3 tables, accepted for publication in Ap

HST/FOS Time-resolved spectral mapping of IP Pegasi at the end of an outburst

We report an eclipse mapping analysis of time-resolved ultraviolet spectroscopy covering three eclipses of the dwarf nova IP Pegasi on the late decline of the 1993 May outburst. The eclipse maps of the first run show evidence of one spiral arm, suggesting that spiral structures may still be present in the accretion disc 9 days after the onset of the outburst. In the spatially resolved spectra the most prominent lines appear in emission at any radius, being stronger in the inner disc regions. The spectrum of the gas stream is clearly distinct from the disc spectrum in the intermediate and outer disc regions, suggesting the occurrence of gas stream overflow. The full width half maximum of C IV is approximately constant with radius, in contrast to the expected $v\propto{R^{-1/2}}$ law for a gas in Keplerian orbits. This line probably originates in a vertically extended region (chromosphere + disc wind). The uneclipsed component contributes $\sim{4}$ % of the flux in C IV in the first run, and becomes negligible in the remaining runs. We fit stellar atmosphere models to the spatially resolved spectra. The radial run of the disc color temperature for the three runs is flatter than the expected $T\propto{R^{-3/4}}$ law for steady-state optically thick discs models, with $T\simeq{20000}$ K in the inner regions and $T\simeq{9000}$ K in the outer disc regions. The solid angles that result from the fits are smaller than expected from the parameters of the system. The radial run of the solid angle suggests that the disc is flared in outburst, and decreases in thickness toward the end of the outburst.Comment: 14 pages, 14 figures, in press in Astronomy & Astrophysic

Energy efficient engine: Flight propulsion system preliminary analysis and design

The characteristics of an advanced flight propulsion system (FPS), suitable for introduction in the late 1980's to early 1990's, was more fully defined. It was determined that all goals for efficiency, environmental considerations, and economics could be met or exceeded with the possible exception of NOx emission. In evaluating the FPS, all aspects were considered including component design, performance, weight, initial cost, maintenance cost, engine system integration (including nacelle), and aircraft integration considerations. The current FPS installed specific fuel consumption was reduced 14.2% from that of the CF6-50C reference engine. When integrated into an advanced, subsonic, study transport, the FPS produced a fuel burn savings of 15 to 23% and a direct operating cost reduction of 5 to 12% depending on the mission and study aircraft characteristics relative to the reference engine

Gq-Mediated Ca** Signals in Human Airway Smooth Muscle Cells

Current asthma therapies include corticosteroids, long acting β2-adrenergic receptor (β2-AR) agonists paired with corticosteroids, or short-acting β2-AR agonists used in rescue inhalers. Chronic use of β-agonists results in diminished effectiveness, and use of long-acting β-agonists can even exacerbate asthma symptoms; this is partly because anti-inflammatory therapy does not directly address the exaggerated airway narrowing due to excessive shortening of airway smooth muscle (ASM), which is the hallmark of asthma. These observations led our collaborators to investigate other potential asthma therapies – bitter taste agonists. 2 Bitter taste agonists, such as chloroquine, activate a subset of Gq-coupled receptors known as bitter taste 2 receptors (TAS2Rs) in airway smooth muscle cells. Activation of these receptors triggers relaxation of human airway smooth muscle cells (HASMCs). This response is markedly different than the response to activation of other Gq-coupled receptors, such as muscarinic receptors, which when activated trigger contraction of HASMCs. The goal of this thesis project is to understand how different Gq-coupled receptor agonists trigger distinct responses in HASMCs. The working hypothesis is that differences in the spatial distributions and/or kinetics (duration) of intracellular calcium (Ca++) signals are responsible for the distinct responses. To test this hypothesis, xv HASMCs were treated with different concentrations of carbachol (1 – 50 µM), a m3 muscarinic acetylcholine receptor (m3 mAChR) agonist; chloroquine (10 – 200 µM), a TAS2R agonist; or histamine (0.5 – 5 µM), a histamine 1 receptor (H1R) agonist, to target different subsets of Gq-mediated receptors. HASMCs were loaded with Cal-520® AM, a green-fluorescent dye that, upon binding to intracellular Ca++, increases its fluorescence intensity. Change in intracellular Ca++ following agonist addition were visualized and measured over time using an Andor WD spinning disk confocal microscope. Distinct spatial differences in Ca++ signals in response the agonist addition were quantified by measuring two parameters – Ca++ signal maximum intensity in the identified signal areas over time and Ca++ signal area changes over time. Distinct kinetic differences in Ca++ signals were quantified by measuring two more parameters: Ca++ signal duration and the number of identified Ca++ responses induced by each agonist per experiment. Furthermore, the distinct changes in peak intensity, signal area, duration, and number of induced Ca++ signals were analyzed for possible concentration dependencies, which could provide future insight into the unique airway responses induced by each agonist

Roche tomography of cataclysmic variables - II. Images of the secondary stars in AM Her, QQ Vul, IP Peg and HU Aqr

We present a set of Roche tomography reconstructions of the secondary stars in the cataclysmic variables AM Her, QQ Vul, IP Peg and HU Aqr. The image reconstructions show distinct asymmetries in the irradiation pattern for all four systems that can be attributed to shielding of the secondary star by the accretion stream/column in AM Her, QQ Vul and HU Aqr, and increased irradiation by the bright-spot in IP Peg. We use the entropy landscape technique to derive accurate system parameters (M1, M2, i and γ) for the four binaries. In principle, this technique should provide the most reliable mass determinations available, since the intensity distribution across the secondary star is known. We also find that the intensity distribution can systematically affect the value of γ derived from circular orbit fits to radial velocity variations

A Facile and Efficient Protocol for Preparing Residual-Free Single-Walled Carbon Nanotube Films for Stable Sensing Applications

In this article, we report on an efficient post-treatment protocol for the manufacturing of pristine single-walled carbon nanotube (SWCNT) films. To produce an ink for the deposition, the SWCNTs are dispersed in an aqueous solution with the aid of a carboxymethyl cellulose (CMC) derivative as the dispersing agent. On the basis of this SWCNT-ink, ultra-thin and uniform films are then fabricated by spray-deposition using a commercial and fully automated robot. By means of X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), we show that the CMC matrix covering the CNTs can be fully removed by an immersion treatment in HNO3 followed by thermal annealing at a moderate temperature of 100 ºC, in the ambient air. We propose that the presented protocols for the ink preparation and the post-deposition treatments can in future serve as a facile and efficient platform for the fabrication of high-quality and residual-free SWCNT films. The purity of SWCNT films is of particular importance for sensing applications, where residual-induced doping and dedoping processes distort the contributions from the sensing specimen. To study the usability of the presented films for practical applications, gas sensors are fabricated and characterized with the CNT-films as the sensing material, screen printed silver-based films for the interdigitated electrode (IDE) structure, and polyimide as a flexible and robust substrate. The sensors show a high and stable response of 11% to an ammonia (NH3) test gas, at a concentration of 10 ppm.The authors thank the Deutsche Forschungsgemeinschaft (DFG) and the Natural Sciences and Engineering Research Council (NSERC) for financial support of the Alberta/Technische Universität München Graduate School for Functional Hybrid Materials ATUMS (IRTG2022, NSERC CREATE), as well as the TUM Graduate School, the Nanosystems Initiative Munich (NIM), and the TUM International Graduate School of Science and Engineering (IGSSE)