Observations of Intrahour Variable Quasars: Scattering in our Galactic Neighbourhood

Interstellar scintillation (ISS) has been established as the cause of the random variations seen at centimetre wavelengths in many compact radio sources on timescales of a day or less. Observations of ISS can be used to probe structure both in the ionized insterstellar medium of the Galaxy, and in the extragalactic sources themselves, down to microarcsecond scales. A few quasars have been found to show large amplitude scintillations on unusually rapid, intrahour timescales. This has been shown to be due to weak scattering in very local Galactic ``screens'', within a few tens of parsec of the Sun. The short variability timescales allow detailed study of the scintillation properties in relatively short observing periods with compact interferometric arrays. The three best-studied ``intrahour variable'' quasars, PKS 0405-385, J1819+3845 and PKS 1257-326, have been instrumental in establishing ISS as the principal cause of intraday variability at centimetre wavelengths. Here we review the relevant results from observations of these three sources.Comment: 10 pages, 4 figures, to appear in Astronomical and Astrophysical Transaction

Planetary Radio Interferometry and Doppler Experiment (PRIDE) Technique: a Test Case of the Mars Express Phobos Fly-by. 2. Doppler tracking: Formulation of observed and computed values, and noise budget

Context. Closed-loop Doppler data obtained by deep space tracking networks (e.g., NASA's DSN and ESA's Estrack) are routinely used for navigation and science applications. By "shadow tracking" the spacecraft signal, Earth-based radio telescopes involved in Planetary Radio Interferometry and Doppler Experiment (PRIDE) can provide open-loop Doppler tracking data when the dedicated deep space tracking facilities are operating in closed-loop mode only. Aims. We explain in detail the data processing pipeline, discuss the capabilities of the technique and its potential applications in planetary science. Methods. We provide the formulation of the observed and computed values of the Doppler data in PRIDE tracking of spacecraft, and demonstrate the quality of the results using as a test case an experiment with ESA's Mars Express spacecraft. Results. We find that the Doppler residuals and the corresponding noise budget of the open-loop Doppler detections obtained with the PRIDE stations are comparable to the closed-loop Doppler detections obtained with the dedicated deep space tracking facilities

Intraday variability of AGNs in the southern hemisphere

Understanding of the spectral and polarimetric characteristics of rapidly scintillating blazars is fundamental in order to describe both the innermost (sub-pc) regions of these compact objects and the interstellar medium responsible for the scintillation. A multi frequency analysis of the intraday variability in PMN J1326-5256, based on the combination of Australia Telescope Compact Array observations with the data from the monitoring projects at the University of Tasmania, will be described. Some implications concerning the structure of compact radio cores and the properties of the interstellar medium will be discussed

Understanding Scintillation of Intraday Variables

Intraday Variability of compact extragalactic radio sources can be interpreted as quenched scintillation due to turbulent density fluctuations of the nearby ionized interstellar medium. We demonstrate that the statistical analysis of IDV time series contains both information about sub-structure of the source on the scale of several 10 micro-arcsec and about the turbulent state of the ISM. The source structure and ISM properties cannot be disentangled using IDV observations alone. A comparison with the known morphology of the `local bubble' and the turbulent ISM from pulsar observations constrains possible source models. We further argue that earth orbit synthesis fails for non-stationary relativistic sources and no reliable 2D-Fourier reconstruction is possible.Comment: 4 pages, 3 figures, Proceedings of the 6th European VLBI Network Symposium, Ros E., Porcas R.W., Lobanov, A.P., & Zensus, J.A. (eds), MPIfR, Bonn, German

Venus Express radio occultation observed by PRIDE

Context. Radio occultation is a technique used to study planetary atmospheres by means of the refraction and absorption of a spacecraft carrier signal through the atmosphere of the celestial body of interest, as detected from a ground station on Earth. This technique is usually employed by the deep space tracking and communication facilities (e.g., NASA's Deep Space Network (DSN), ESA's Estrack). Aims. We want to characterize the capabilities of the Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique for radio occultation experiments, using radio telescopes equipped with Very Long Baseline Interferometry (VLBI) instrumentation. Methods. We conducted a test with ESA's Venus Express (VEX), to evaluate the performance of the PRIDE technique for this particular application. We explain in detail the data processing pipeline of radio occultation experiments with PRIDE, based on the collection of so-called open-loop Doppler data with VLBI stations, and perform an error propagation analysis of the technique. Results. With the VEX test case and the corresponding error analysis, we have demonstrated that the PRIDE setup and processing pipeline is suited for radio occultation experiments of planetary bodies. The noise budget of the open-loop Doppler data collected with PRIDE indicated that the uncertainties in the derived density and temperature profiles remain within the range of uncertainties reported in previous Venus' studies. Open-loop Doppler data can probe deeper layers of thick atmospheres, such as that of Venus, when compared to closed-loop Doppler data. Furthermore, PRIDE through the VLBI networks around the world, provides a wide coverage and range of large antenna dishes, that can be used for this type of experiments

Effective lifestyle interventions to improve type II diabetes self-management for those with schizophrenia or schizoaffective disorder: a systematic review

<p>Abstract</p> <p>Background</p> <p>The prevalence of type II diabetes among individuals suffering from schizophrenia or schizoaffective disorders is more than double that of the general population. By 2005, North American professional medical associations of Psychiatry, Diabetes, and Endocrinology responded by recommending continuous metabolic monitoring for this population to control complications from obesity and diabetes. However, these recommendations do not identify the types of effective treatment for people with schizophrenia who have type II diabetes. To fill this gap, this systematic evidence review identifies effective lifestyle interventions that enhance quality care in individuals who are suffering from type II diabetes and schizophrenia or other schizoaffective disorders.</p> <p>Methods</p> <p>A systematic search from Medline, CINAHL, PsycINFO, and ISI Web of Science was conducted. Of the 1810 unique papers that were retrieved, four met the inclusion/exclusion criteria and were analyzed.</p> <p>Results</p> <p>The results indicate that diabetes education is effective when it incorporates diet and exercise components, while using a design that addresses challenges such as cognition, motivation, and weight gain that may result from antipsychotics.</p> <p>Conclusions</p> <p>This paper begins to point to effective interventions that will improve type II diabetes management for people with schizophrenia or other schizoaffective disorders.</p