3,037 research outputs found

    Skycorr: A general tool for spectroscopic sky subtraction

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    Airglow emission lines, which dominate the optical-to-near-IR sky radiation, show strong, line-dependent variability on various time scales. Therefore, the subtraction of the sky background in the affected wavelength regime becomes a problem if plain sky spectra have to be taken at a different time as the astronomical data. A solution of this issue is the physically motivated scaling of the airglow lines in the plain sky data to fit the sky lines in the object spectrum. We have developed a corresponding instrument-independent approach based on one-dimensional spectra. Our code skycorr separates sky lines and sky/object continuum by an iterative approach involving a line finder and airglow line data. The sky lines are grouped according to their expected variability. The line groups in the sky data are then scaled to fit the sky in the science data. Required pixel-specific weights for overlapping groups are taken from a comprehensive airglow model. Deviations in the wavelength calibration are corrected by fitting Chebyshev polynomials and rebinning via asymmetric damped sinc kernels. The scaled sky lines and the sky continuum are subtracted separately. VLT X-Shooter data covering time intervals from two minutes to about one year were selected to illustrate the performance. Except for short time intervals of a few minutes, the sky line residuals were several times weaker than for sky subtraction without fitting. Further tests show that skycorr performs consistently better than the method of Davies (2007) developed for VLT SINFONI data.Comment: 17 pages, 18 figures, accepted for publication in A&

    Making SPIFFI SPIFFIER: Upgrade of the SPIFFI instrument for use in ERIS and performance analysis from re-commissioning

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    SPIFFI is an AO-fed integral field spectrograph operating as part of SINFONI on the VLT, which will be upgraded and reused as SPIFFIER in the new VLT instrument ERIS. In January 2016, we used new technology developments to perform an early upgrade to optical subsystems in the SPIFFI instrument so ongoing scientific programs can make use of enhanced performance before ERIS arrives in 2020. We report on the upgraded components and the performance of SPIFFI after the upgrade, including gains in throughput and spatial and spectral resolution. We show results from re-commissioning, highlighting the potential for scientific programs to use the capabilities of the upgraded SPIFFI. Finally, we discuss the additional upgrades for SPIFFIER which will be implemented before it is integrated into ERIS.Comment: 20 pages, 12 figures. Proceedings from SPIE Astronomical Telescopes and Instrumentation 201

    An economists' manifesto on unemployment in the European Union.

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    This manifesto challenges a pernicious orthodoxy that has gripped Europe's policy makers. It is that demand- and supply-side policies must have different aims, that a limited number of supply-side policies are to be devoted to fighting unemployment, and that demand management (and particularly monetary policy) is are to be devoted solely to fighting inflation. The prevailing orthodoxy also claims that the choice of policy instruments for combating unemployment is a political decision, in which each instrument is evaluated on a case-by-case basis. In what follows, we outline various practical proposals aimed at a prompt reduction of unemployment. We are confident that if the advice is given proper attention by governments and monetary authorities, unemployment can be reduced significantly in a matter of a few years. We will divide the proposed actions into those bearing on the revival of aggregate demand (demand policies) and those addressed to the reform of the labour and product markets and the system of benefits for the unemployed (supply policies). But we stress from the very beginning that we regard our proposals as strictly complementary with one another. Each proposal, applied in isolation, may produce little or even perverse effects, while the simultaneous application can be counted upon to yield the desired outcome. This holds in particular with respect to the relation between demand and supply policies. The underlying idea is that it is much easier to encourage people to look for jobs if there are jobs to be found and it is much easier to encourage firms to offer more jobs if there are people looking for jobs.Beschäftigungspolitik; Arbeitslosigkeit; EU-Staaten;

    Corporate financing decisions: UK survey evidence

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    Despite theoretical developments in recent years, our understanding of corporate capital structure remains incomplete. Prior empirical research has been dominated by archival regression studies which are limited in their ability to fully reflect the diversity found in practice. The present paper reports on a comprehensive survey of corporate financing decision-making in UK listed companies. A key finding is that firms are heterogeneous in their capital structure policies. About half of the firms seek to maintain a target debt level, consistent with trade-off theory, but 60 per cent claim to follow a financing hierarchy, consistent with pecking order theory. These two theories are not viewed by respondents as either mutually exclusive or exhaustive. Many of the theoretical determinants of debt levels are widely accepted by respondents, in particular the importance of interest tax shield, financial distress, agency costs and also, at least implicitly, information asymmetry. Results also indicate that cross-country institutional differences have a significant impact on financial decisions

    Comparative interactomics analysis of different ALS-associated proteins identifies converging molecular pathways

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    Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease with no effective treatment available. An increasing number of genetic causes of ALS are being identified, but how these genetic defects lead to motor neuron degeneration and to which extent they affect common cellular pathways remains incompletely understood. To address these questions, we performed an interactomic analysis to identify binding partners of wild-type (WT) and ALS-associated mutant versions of ATXN2, C9orf72, FUS, OPTN, TDP-43 and UBQLN2 in neuronal cells. This analysis identified several known but also many novel binding partners of these proteins

    An economists' manifesto on unemployment in the European Union

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    This manifesto challenges a pernicious orthodoxy that has gripped Europe's policy makers. It is that demand- and supply-side policies must have different aims, that a limited number of supply-side policies are to be devoted to fighting unemployment, and that demand management (and particularly monetary policy) is are to be devoted solely to fighting inflation. The prevailing orthodoxy also claims that the choice of policy instruments for combating unemployment is a political decision, in which each instrument is evaluated on a case-by-case basis. In what follows, we outline various practical proposals aimed at a prompt reduction of unemployment. We are confident that if the advice is given proper attention by governments and monetary authorities, unemployment can be reduced significantly in a matter of a few years. We will divide the proposed actions into those bearing on the revival of aggregate demand (demand policies) and those addressed to the reform of the labour and product markets and the system of benefits for the unemployed (supply policies). But we stress from the very beginning that we regard our proposals as strictly complementary with one another. Each proposal, applied in isolation, may produce little or even perverse effects, while the simultaneous application can be counted upon to yield the desired outcome. This holds in particular with respect to the relation between demand and supply policies. The underlying idea is that it is much easier to encourage people to look for jobs if there are jobs to be found and it is much easier to encourage firms to offer more jobs if there are people looking for jobs

    Understanding the Recent Growth in Consumer Loans and Credit Cards in Emerging Markets:Evidence from Turkey

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    In recent years, the surge in household indebtedness to historical heights has become a significant concern for developed economies. A similar trend has been witnessed in emerging market countries including Turkey. Our objective is to help further understand the dynamics of the recent growth in consumer loans and credit cards (CLCC) in Turkey. For this purpose, we investigate the long-term equilibrating relationships and short-term deviations from the equilibrium, and explore the determinants, directions, and strengths of causality relationships between CLCC and the selected macroeconomic variables, and analyze the dynamic interactions among the variables in the post-sample period by analyzing how CLCC responds to the shocks given to other macroeconomic variables and the contribution of each variable on the forecast variability of CLCC. We use monthly data for the period of January 2004—December 2013 of seven macroeconomic variables of money supply, interest rate, income, consumer confidence, inflation, stock market, and consumer goods imports. On empirical findings, we make suggestions about which policy tools should be used to influence, and if necessary to manage, the growth in CLCC. Copyright © Taylor & Francis Group, LLC

    The short term debt vs. long term debt puzzle: a model for the optimal mix

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    This paper argues that the existing finance literature is inadequate with respect to its coverage of capital structure of small and medium sized enterprises (SMEs). In particular it is argued that the cost of equity (being both conceptually ill defined and empirically non quantifiable) is not applicable to the capital structure decisions for a large proportion of SMEs and the optimal capital structure depends only on the mix of short and long term debt. The paper then presents a model, developed by practitioners for optimising the debt mix and demonstrates its practical application using an Italian firm's debt structure as a case study

    Nebular and global properties of the gravitationally lensed galaxy "the 8 o'clock arc"

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    We present the analysis of new NIR, intermediate-resolution spectra of the gravitationally lensed galaxy "the 8 o'clock arc" at z_sys = 2.7350 obtained with VLT/X-shooter. These rest-frame optical data, combined with HST and Spitzer images, provide very valuable information, which nicely complement our previous detailed rest-frame UV spectral analysis. From high-resolution HST images, we reconstruct the morphology of the arc in the source plane, and identify that the source is formed of two majors parts, the main galaxy component and a smaller blob separated by 1.2 kpc in projected distance. The blob, with a twice larger magnification factor, is resolved in the spectra. The multi-Gaussian fitting of detected nebular emission lines and the spectral energy distribution modeling of the available multi-wavelength photometry provide the census of gaseous and stellar dust extinctions, gas-phase metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical masses for both the main galaxy and the blob. As a result, the 8 o'clock arc shows a marginal trend for a more attenuated ionized gas than stars, and supports a dependence of the dust properties on the SFR. With a high specific star-formation rate, SSFR = 33+/-19 Gyr^{-1}, this lensed Lyman-break galaxy deviates from the mass-SFR relation, and is characterized by a young age of 40^{+25}_{-20} Myr and a high gas fraction of about 72%. The 8 o'clock arc satisfies the fundamental mass, SFR, and metallicity relation, and favors that it holds up beyond z~2.5. We believe that the blob, with a gas mass M_gas = (2.2+/-0.9)x10^{9} Msun (one order of magnitude lower than the mass of the galaxy), a half-light radius r1/2 = 0.53+/-0.05 kpc, a star-formation rate SFR_Halpha = 33+/-19 Msun yr^{-1}, and in rotation around the main core of the galaxy, is one of these star-forming clumps commonly observed in z>1 star-forming galaxies. (Abridged)Comment: 15 pages, 5 figures, published in Astronomy and Astrophysic
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