ZAP -- Enhanced PCA Sky Subtraction for Integral Field Spectroscopy

We introduce Zurich Atmosphere Purge (ZAP), an approach to sky subtraction based on principal component analysis (PCA) that we have developed for the Multi Unit Spectrographic Explorer (MUSE) integral field spectrograph. ZAP employs filtering and data segmentation to enhance the inherent capabilities of PCA for sky subtraction. Extensive testing shows that ZAP reduces sky emission residuals while robustly preserving the flux and line shapes of astronomical sources. The method works in a variety of observational situations from sparse fields with a low density of sources to filled fields in which the target source fills the field of view. With the inclusion of both of these situations the method is generally applicable to many different science cases and should also be useful for other instrumentation. ZAP is available for download at http://muse-vlt.eu/science/tools.Comment: 12 pages, 7 figures, 1 table. Accepted to MNRA

Coupling different levels of resolution in molecular simulations

Simulation schemes that allow to change molecular representation in a subvolume of the simulation box while preserving the equilibrium with the surrounding introduce conceptual problems of thermodynamic consistency. In this work we present a general scheme based on thermodynamic arguments which ensures thermodynamic equilibrium among the molecules of different representation. The robustness of the algorithm is tested for two examples, namely an adaptive resolution simulation, atomistic/coarse-grained, for a liquid of tetrahedral molecules and an adaptive resolution simulation of a binary mixture of tetrahedral molecules and spherical solutes

Smooth Initial Conditions from Weak Gravity

CMB measurements reveal an unnaturally smooth early universe. We propose a mechanism to make this smoothness natural by weakening the strength of gravity at early times, and therefore altering which initial conditions have low entropy.Comment: 14 pages, 5 figures. Minor changes, version appearing in PL

Polarization-independent broadband bidirectional optical cloaking using a new type of inverse scattering approach

(c) 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Since the advent of transformation optics a decade ago [1], the ability to achieve optical cloaking has become a matter of practical realization. However, so far extreme material requirements and large device areas have significantly posed an obstacle to realize compact cloaking schemes that are fully functional. Here, by taking a different approach and by following our recently developed general theorem to control the scattering behaviour of an arbitrary object on a specific demand [2], we show that nearly perfect bidirectional optical cloaking effect can be generated for any type of object with a given shape and size. Contrary to previous approaches, we reveal that such a method is always able to produce local refractive indices larger than one and that neither gain nor lossy materials are required. Furthermore, by means of numerical calculations, we demonstrate a highly tunable broad operational bandwidth of 550 nm (covering 650-1200 nm interval) and an angular aperture of 36° for both directions and polarizations. With these unprecedented features, we expect that the present work will hold a great potential to enable a new class of optical cloaking structures that will find applications particularly in communication systems, defence industry and in other related fields.Peer ReviewedPostprint (author's final draft

Adaptive resolution molecular dynamics simulation through coupling to an internal particle reservoir

For simulation studies of (macro) molecular liquids it would be of significant interest to be able to adjust or increase the level of resolution within one region of space, while allowing for the free exchange of molecules between open regions of different resolution or representation. We generalize the adaptive resolution idea and suggest an interpretation in terms of an effective generalized grand canonical approach. The method is applied to liquid water at ambient conditions

Impacts of Fed’s decisions on emerging countries: an empirical analysis & investment solution

On July 13th, 2019, the Fed decided to reduce its interest rates by 25 basis points. Its first since October 2008. A decision that could be thought of as a good thing for the emerging countries’ economies. Indeed, according to economic theories and history, they would benefit from a significant breath of fresh air. Legend has it that the Fed's will have a significant impact on emerging countries, whether positive or negative. One could, therefore, question why did Argentina’s stock exchange – just a few weeks after the so-called beneficial decision of the US central bank – lose 48% in one trading session. The second-largest stock market sell-off in history after Sri Lanka’s civil war outbreak in 1989 (-61.7%). Obviously, the reasons for this Argentine air gap have endogenous roots, mostly political, but it is then interesting to investigate if the Fed’s decisions impact the emerging regions of the world. Do this relation still exists today? Have emerging countries emancipated themselves from the American game? And finally, depending on the answers, what would be the most efficient ways to invest in these regions, rationally and professionally. This paper, therefore, tries to demonstrate whether the impact on emerging markets of the Fed's decisions on rates still exists. More precisely, the approach here is to investigate the reactions of emerging currencies against the US dollar when interest rates vary. Through a statistical analysis over two periods (1997- 2008 and 2008-2019), using tools such as linear regression and correlation observation, and adding the time-lag component, interesting results emerge. Indeed, depending on the period chosen, they are diametrically opposed. As things stand, the study shows a causal relationship and a correlation between interest rate decisions and emerging currencies. However, the change in US rates does not explain all the variation in the analysed currencies. The economic cycle in which the analysis was made must also be considered, it is likely that the latter is a significant component. The addition of variables would improve the performed statistical model, thus allowing a better understanding of their behaviour and so facilitate the investment process. On this basis, adjusted with informed insights and experience of professionals, but also with the attempt to reduce cognitive biases to a minimum, this paper concludes with an investment solution. More specifically, a quantitative stock selection tool based on the mixed implementation of fundamental and technical analysis, which now shows encouraging results

Using GIS to identify clusters of potential donors to colleges and universities

As tuition at colleges and universities continues to rise, many development offices face increased pressure to raise additional funds from alumni and friends. This pressure has intensified, in part due to costs associated with the investment in the latest computer technology. But these costly computer tools also can be used by schools to increase philanthropic giving. This paper explores ways in which development offices can use one computer-based research tool, Geographic Information Systems, to better identify potential donors. GIS allows a researcher to overlay data on a map and then search for patterns that might not be otherwise apparent. The paper offers a brief history of GIS and explores its diverse uses. The paper focuses on several current uses of GIS at colleges and universities and explores initial efforts by schools to use the technology in philanthropic giving. Finally, the paper demonstrates how GIS can work in a university capital campaign. Using data from one school, the paper shows how geocoding can help a development office focus on such questions as 1) whether alumni and friends who currently contribute are geographically “clustered” in identifiable neighborhoods; 2) what the wealth of these neighborhoods is and whether the wealth correlates with the level of giving; and 3) for alumni and potential donors who are not contributors, what their giving potential is

Slow light enabled wavelength demultiplexing

Photonic crystal waveguides supporting band gap guided modes hold great potential to tailor the group velocity of propagating light. We propose and explore different wavelength demultiplexer design approaches that utilize slow light concept. By altering the dielectric filling factors of each waveguide segment, one can show that different frequencies can be separated and extracted at different locations along the cascaded waveguide. Furthermore, to eliminate the inherent reflection loss of such a design, a composite structure involving a tapered waveguide with a side-coupled resonator is also presented. Such a structure features not only a forward propagating wave but also a backward propagating wave acting as a feedback mechanism for the drop channels. We show that by careful design of the waveguide and the resonator, the destructive and instructive interference of these waves can effectively eliminate the reflection loss and increase the coupling efficiency, respectively. Numerical and experimental verification of the proposed structures show that the targeted frequencies can be coupled out with low cross-talks and moderate quality factors, while maintaining a compact size. © 2016 IEEE.Peer ReviewedPostprint (published version