A PCA-based approach for subtracting thermal background emission in high-contrast imaging data

Ground-based observations at thermal infrared wavelengths suffer from large background radiation due to the sky, telescope and warm surfaces in the instrument. This significantly limits the sensitivity of ground-based observations at wavelengths longer than 3 microns. We analyzed this background emission in infrared high contrast imaging data, show how it can be modelled and subtracted and demonstrate that it can improve the detection of faint sources, such as exoplanets. We applied principal component analysis to model and subtract the thermal background emission in three archival high contrast angular differential imaging datasets in the M and L filter. We describe how the algorithm works and explain how it can be applied. The results of the background subtraction are compared to the results from a conventional mean background subtraction scheme. Finally, both methods for background subtraction are also compared by performing complete data reductions. We analyze the results from the M dataset of HD100546 qualitatively. For the M band dataset of beta Pic and the L band dataset of HD169142, which was obtained with an annular groove phase mask vortex vector coronagraph, we also calculate and analyze the achieved signal to noise (S/N). We show that applying PCA is an effective way to remove spatially and temporarily varying thermal background emission down to close to the background limit. The procedure also proves to be very successful at reconstructing the background that is hidden behind the PSF. In the complete data reductions, we find at least qualitative improvements for HD100546 and HD169142, however, we fail to find a significant increase in S/N of beta Pic b. We discuss these findings and argue that in particular datasets with strongly varying observing conditions or infrequently sampled sky background will benefit from the new approach.Comment: 12 pages, 17 figures, 1 table, Accepted for publication in A&

Limiting absorption principle and perfectly matched layer method for Dirichlet Laplacians in quasi-cylindrical domains

We establish a limiting absorption principle for Dirichlet Laplacians in quasi-cylindrical domains. Outside a bounded set these domains can be transformed onto a semi-cylinder by suitable diffeomorphisms. Dirichlet Laplacians model quantum or acoustically-soft waveguides associated with quasi-cylindrical domains. We construct a uniquely solvable problem with perfectly matched layers of finite length. We prove that solutions of the latter problem approximate outgoing or incoming solutions with an error that exponentially tends to zero as the length of layers tends to infinity. Outgoing and incoming solutions are characterized by means of the limiting absorption principle.Comment: to appear in SIAM Journal on Mathematical Analysi

Perspectives on organic light-emitting diodes for display applications

Herein, we describe a number of key issues that concern the commercialization of organic light-emitting diodes for display applications. We will firstly outline the historical and market contexts that show the potential for organic electronics as a viable display technology. Next, we will discuss the chemical structures for a range of both small-molecular and polymer organic semiconducting compounds, and how the electronic properties are governed thereof. Also we will briefly discuss various common film deposition and device fabrication strategies. Then, we will describe two factors that are highly relevant for commercially viable organic light-emitting diodes, namely charge balance, and device degradation. Finally, we will outline some methods for achieving the high-volume throughput of organic electronics via well-established technologies that are used in the printing industr

Assumptions that imply quantum dynamics is linear

A basic linearity of quantum dynamics, that density matrices are mapped linearly to density matrices, is proved very simply for a system that does not interact with anything else. It is assumed that at each time the physical quantities and states are described by the usual linear structures of quantum mechanics. Beyond that, the proof assumes only that the dynamics does not depend on anything outside the system but must allow the system to be described as part of a larger system. The basic linearity is linked with previously established results to complete a simple derivation of the linear Schrodinger equation. For this it is assumed that density matrices are mapped one-to-one onto density matrices. An alternative is to assume that pure states are mapped one-to-one onto pure states and that entropy does not decrease.Comment: 10 pages. Added references. Improved discussion of equations of motion for mean values. Expanded Introductio

Wavelength conversion at 10 Gb/s by four-wave mixing over a 30-nm interval

We show that the use of a long semiconductor optical amplifier increases the error-free conversion interval of a four-wave mixing (FWM)-based wavelength converter. 30-nm wavelength down-conversion and 15-nm up-conversion have been obtained at 10 Gb/s. This result is a significant improvement over the previous best performance of a FWM-based wavelength converter and suggests that the full erbium-doped fiber amplifier bandwidth can be covered with FWM wavelength converters

30-nm wavelength conversion at 10 Gbit/s by four-wave mixing in a semiconductor optical amplifier

Four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is currently the only available strictly transparent wavelength-conversion technique, which is not penalized by phase matching. The span of the conversion is limited primarily by conversion efficiency and signal-to-noise (SNR) issues, both of which are expected to improve with the use of longer SOAs. In this paper, we demonstrate significantly enhanced performance of long converters in a system experiment at 10 Gbit/s. The experiment shows for the first time, to our knowledge, that FWM wavelength down-conversions can span the full gain bandwidth of erbium-doped fiber amplifiers

Canonical Expansion of PT-Symmetric Operators and Perturbation Theory

Let $H$ be any \PT symmetric Schr\"odinger operator of the type $-\hbar^2\Delta+(x_1^2+...+x_d^2)+igW(x_1,...,x_d)$ on $L^2(\R^d)$, where $W$ is any odd homogeneous polynomial and $g\in\R$. It is proved that $\P H$ is self-adjoint and that its eigenvalues coincide (up to a sign) with the singular values of $H$, i.e. the eigenvalues of $\sqrt{H^\ast H}$. Moreover we explicitly construct the canonical expansion of $H$ and determine the singular values $\mu_j$ of $H$ through the Borel summability of their divergent perturbation theory. The singular values yield estimates of the location of the eigenvalues \l_j of $H$ by Weyl's inequalities.Comment: 20 page

Extrakorporale Stoßwellentherapie eines komplizierten chronischen Ulcus cruris venosum

Zusammenfassung: Extrakorporale Stoßwellen werden definiert als eine Sequenz von akustischen Schallimpulsen, die einen charakteristisch schnellen Druckanstieg auf über 100MPa mit Abfall auf Normaldruck in wenigen Mikrosekunden aufweisen. In den 1980er-Jahren wurde die extrakorporale Stoßwellenlithotripsie (ESWL) erstmals zur Behandlung der Urolithiasis angewandt. Orthopäden setzten anschließend die extrakorporale Stoßwellentherapie (ESWT) zur Behandlung von nicht heilenden Frakturen, Tendinopathien und Osteonekrose ein. Die erste Anwendung von ESWT in der Dermatologie erfolgte zur Behandlung des chronischen Ulcus cruris. Verschiedene Studien der letzten 10Jahre zeigten, dass die ESWT die Angiogenese stimuliert und die Perfusion im ischämischen Gewebe verbessert, die Entzündungsreaktion mindert, die Zelldifferenzierung unterstützt und hiermit die Wundheilung deutlich verbessern kann. Wir setzten die ESWT erfolgreich zur Behandlung eines komplizierten chronischen venösen Ulcus cruris ein. Weiter konnten wir eine Verbesserung des lymphatischen Abflusses nach Applikation von ESWT beobachten. Die ESWT stellt somit eine nebenwirkungsarme und effiziente physikalische Therapiemodalität zur Behandlung von therapieresistenten chronischen Wunden da

Der internistische Check-up

Zusammenfassung: Viele präventive Maßnahmen bei gesunden Erwachsenen werden in zunehmendem Maße durch Evidenz gestützt oder verworfen. Dabei sind v.a. die Beratung bezüglich Tabakabstinenz, indizierte Impfungen und das Screening in Bezug auf Übergewicht, hohen Blutdruck, Hyperlipidämie, Zervixkarzinom, kolorektales Karzinom und Mammakarzinom bewiesenermaßen wichtig und sinnvoll. Nicht empfohlen wird ein Screening für Bronchial-, Pankreas- und Ovarialkarzinom. Ein Screening für Diabetes mellitus beim jüngeren Erwachsenen, Schilddrüsenerkrankungen und Prostatakarzinom wird nicht routinemäßig empfohlen, sollte aber je nach persönlichem Risikoprofil im Sinne eines sog. "Case findings" erwogen werden. Aus ärztlicher Sicht ist es auch wichtig, auf mögliche nicht deklarierte Beweggründe für eine Check-up-Untersuchung einzugehen, um so mögliche "Hidden Agendas" der Konsultationen aufzudecke