Unbiased flux calibration methods for spectral-line radio observations

Position and frequency switching techniques used for the removal of the bandpass dependence of radio astronomical spectra are presented and discussed in detail. Both methods are widely used, although the frequency dependence of the system temperature and/or noise diode is often neglected. This leads to systematic errors in the calibration that potentially have a significant impact on scientific results, especially when using large-bandwidth receivers or performing statistical analyses. We present methods to derive an unbiased calibration using a noise diode, which is part of many heterodyne receivers. We compare the proposed methods and describe the advantages and bottlenecks of the various approaches. Monte Carlo simulations are used to qualitatively investigate both systematics and the error distribution of the reconstructed flux estimates about the correct flux values for the new methods but also the 'classical' case. Finally, the determination of the frequency-dependent noise temperature of the calibration diode using hot-cold measurements or observations of well-known continuum sources is also briefly discussed.Comment: 25 pages, 30 figures. Accepted for publication in A&

The Robustness of Least-Squares Frequency Switching (LSFS)

Least-squares frequency switching (LSFS) is a new method to reconstruct signal and gain function (known as bandpass or baseline) from spectral line observations using the frequency switching method. LSFS utilizes not only two but a set of three or more local oscillator (LO) frequencies. The reconstruction is based on a least squares fitting scheme. Here we present a detailed investigation on the stability of the LSFS method in a statistical sense and test the robustness against radio frequency interference (RFI), receiver gain instabilities and continuum sources. It turns out, that the LSFS method is indeed a very powerful method and is robust against most of these problems. Nevertheless, LSFS fails in presence of RFI signals or strong line emission. We present solutions to overcome these limitations using a flagging mechanism or remapping of measured signals, respectively.Comment: 17 pages, 21 figures, 1 table, accepted for publication in ApJS (November 2007, v173n1

Efficient least-squares basket-weaving

We report on a novel method to solve the basket-weaving problem. Basket-weaving is a technique that is used to remove scan-line patterns from single-dish radio maps. The new approach applies linear least-squares and works on gridded maps from arbitrarily sampled data, which greatly improves computational efficiency and robustness. It also allows masking of bad data, which is useful for cases where radio frequency interference is present in the data. We evaluate the algorithms using simulations and real data obtained with the Effelsberg 100-m telescope.Comment: 11 pages, 11 figures, accepted by A&

Spectrum management and compatibility studies with Python

We developed the pycraf Python package, which provides functions and procedures for various tasks related to spectrum-management compatibility studies. This includes an implementation of ITU-R Rec. P.452, which allows to calculate the path attenuation arising from the distance and terrain properties between an interferer and the victim service. A typical example would be the calculation of interference levels at a radio telescope produced from a radio broadcasting tower. Furthermore, pycraf provides functionality to calculate atmospheric attenuation as proposed in ITU-R Rec. P.676. Using the rich ecosystem of scientific Python libraries and our pycraf package, we performed a large number of compatibility studies. Here, we will highlight a recent case study, where we analysed the potential harm that the next-generation cell-phone standard 5G could bring to observations at a radio observatory. For this we implemented a Monte-Carlo simulation to deal with the quasi-statistical spatial distribution of base stations and user devices around the radio astronomy station.Comment: 17 pages, 21 figures, to appear in Advances in Radio Science, in pres

The Effelsberg-Bonn HI Survey (EBHIS)

The new L-band 7-feed-array at the 100-m telescope in Effelsberg will be used to perform an unbiased fully sampled HI survey of the entire northern hemisphere observing the galactic and extragalactic sky using simultaneously two different backends. The survey will be extremely valuable for a broad range of research topics: study of the low-mass end of the HI mass function (HIMF) in the local volume, environmental and evolutionary effects (as seen in the HIMF), the search for galaxies near low-redshift Lyman-alpha absorbers, and analysis of multiphase and extraplanar gas, HI shells, and ultra-compact high-velocity-clouds.Comment: 2 pages, 1 figure, to appear in proceeding of "Galaxies in the Local Volume" Sydney 8-13 July 200

Nurses Addressing the Knowledge Gap in Advance Care Planning

Background: Advance care planning allows people autonomy about values and preferences related to care at the EOL. Engaging in advance care planning enables one to consider decisions about medical treatment at the EOL and informing significant others, including health care providers, about preferences (National Institute on Aging [NIA], 2018). Methods: In this QI project, the intervention will be a one-time ZOOM® meeting between nurse leaders and participating church members. The nurse leader will present the 5 Wishes curriculum and lead a question-and-answer portion at the end of the ZOOM® meeting. Participants will be asked to complete a short survey before and after the ZOOM® meeting. A comprehensive explanation for completion of the living will and health care proxy is explained during the 5 Wishes presentation. Nurse leaders will be available after the video presentation to respond to follow-up questions and provide further information about advance care planning to participating community members. Outcomes: This project had 38 participants (n = 38) and two nurse leaders. 60% of the participants were female, predominantly white, between the ages 60 to 69 with a college education. The intervention did increase participants’ knowledge of how to create a living will and the purpose of a living will. Conclusions: The findings of this project demonstrate the feasibility and efficacy of a church based educational program promoting advanced directive awareness and completion. 66% of the projects participants already had completed advanced directives prior to participating in this project. However, the participants generally had a poor level of understanding of their documents and how they were to be used. At the conclusion of the Zoom® meeting, statistical analysis demonstrated that participants had a better understanding of the purpose of their advanced directives and how to make changes to their advanced directive documents if needed

Identifying spatial patterns of Mediterranean landscapes from geostatistic analysis of remotely-sensed data

The basic tool of geostatistics, the semi-variograms, has been used for quantifying spatial structures of soil and vegetation, as depicted by multi-resolution remotely-sensed images. Experimental semi-variograms of two contrasting Mediterranean landscapes were analysed by reference to simple theoretical models (spherical, exponential, allometric). A more general approach based on the superposition of spherical models of similar sills and varying ranges of influences is proposed for the interpretation of complex spatial patterns of natural vegetated landscapes. (Résumé d'auteur