Towards an Integrative Formative Approach of Data-Driven Decision Making, Assessment for Learning, and Diagnostic Testing

This study concerns the comparison of three approaches to assessment: Data-Driven Decision Making, Assessment for Learning, and Diagnostic Testing. Although the three approaches claim to be beneficial with regard to student learning, no clear study into the relationships and distinctions between these approaches exists to date. The goal of this study was to investigate the extent to which the three approaches can be shaped into an integrative formative approach towards assessment. The three approaches were compared on nine characteristics of assessment. The results suggest that although the approaches seem to be contradictory with respect to some characteristics, it is argued that they could complement each other despite these differences. The researchers discuss how the three approaches can be shaped into an integrative formative approach towards assessmen

Variability and Velocity of Superluminal Sources

We investigate the relation between the Doppler factor determined from variations in total flux at 22 and 37 GHz, and the apparent transverse velocity determined from VLBA observations at 2 cm. The data are consistent with the relativistic beaming theory for compact radio sources, in that the distribution of beta_{app}/delta_{var}, for 30 quasars, is roughly consistent with a Monte Carlo simulation. The intrinsic temperature appears to be ~2x10^{10} K, close to the "equipartition value" calculated by Readhead (1994). We deduce the distribution of Lorentz factors for a group of 48 sources; the values range up to about gamma=40.Comment: To be published in "Radio Astronomy at the Fringe", ASP Conf. Ser. Vol. 300, J. A. Zensus, M. H. Cohen, & E. Ros (eds.), 8 pages, 3 figures, needs rafringe.st

The inner radio jet region and the complex environment of SS433

We present multi-frequency VLBA+VLA observations of SS433 at 1.6, 5 and 15 GHz. These observations provide the highest angular resolution radio spectral index maps ever made for this object. Motion of the components of SS433 during the observation is detected. In addition to the usual VLBI jet structure, we detect two radio components in the system at an anomalous position angle. These newly discovered radio emitting regions might be related to a wind-like equatorial outflow or to an extension of the accretion disk. We show that the radio core component is bifurcated with a clear gap between the eastern and western wings of emission. Modelfitting of the precessing jets and the moving knots of SS433 shows that the kinematic centre -- i.e. the binary -- is in the gap between the western and eastern radio core components. Spectral properties and observed core position shifts suggest that we see a combined effect of synchrotron self-absorption and external free-free absorption in the innermost AU-scale region of the source. The spatial distribution of the ionized matter is probably not spherically symmetric around the binary, but could be disk-like.Comment: Accepted for publication by Astronomy and Astrophysic

Molecular footprint of drug-selective pressure in a human immunodeficiency virus transmission chain

Known human immunodeficiency virus (HIV) transmission histories are invaluable models for investigating the evolutionary and transmission dynamics of the virus and to assess the accuracy of phylogenetic reconstructions. Here we have characterized an HIV-1 transmission chain consisting of nine infected patients, almost all of whom were treated with antiviral drugs at later stages of infection. Partial pol and env gp41 regions of the HIV genome were directly sequenced from plasma viral RNA for at least one sample from each patient. Phylogenetic analyses in pol using likelihood methods inferred an evolutionary history not fully compatible with the known transmission history. This could be attributed to parallel evolution of drug resistance mutations resulting in the incorrect clustering of multidrug-resistant virus. On the other hand, a fully compatible phylogenetic tree was reconstructed from the env sequences. We were able to identify and quantify the molecular footprint of drug-selective pressure in pol using maximum likelihood inference under different codon substitution models. An increased fixation rate of mutations in the HIV population of the multidrug-resistant patient was demonstrated using molecular clock modeling. We show that molecular evolutionary analyses, guided by a known transmission history, can reveal the presence of confounding factors like natural selection and caution should be taken when accurate descriptions of HIV evolution are required.status: publishe

Object identification and characterization with hyperspectral imagery to identify structure and function of Natura 2000 habitats

Habitat monitoring of designated areas under the EU Habitats Directive requires every 6 years information on area, range, structure and function for the protected (Annex I) habitat types. First results from studies on heathland areas in Belgium and the Netherlands show that hyperspectral imagery can be an important source of information to assist the evaluation of the habitat conservation status. Hyperspectral imagery can provide continuous maps of habitat quality indicators (e.g., life forms or structure types, management activities, grass, shrub and tree encroachment) at the pixel level. At the same time, terrain managers, nature conservation agencies and national authorities responsible for the reporting to the EU are not directly interested in pixels, but rather in information at the level of vegetation patches, groups of patches or the protected site as a whole. Such local level information is needed for management purposes, e.g., exact location of patches of habitat types and the sizes and quality of these patches within a protected site. Site complexity determines not only the classification success of remote sensing imagery, but influences also the results of aggregation of information from the pixel to the site level. For all these reasons, it is important to identify and characterize the vegetation patches. This paper focuses on the use of segmentation techniques to identify relevant vegetation patches in combination with spectral mixture analysis of hyperspectral imagery from the Airborne Hyperspectral Scanner (AHS). Comparison with traditional vegetation maps shows that the habitat or vegetation patches can be identified by segmentation of hyperspectral imagery. This paper shows that spectral mixture analysis in combination with segmentation techniques on hyperspectral imagery can provide useful information on processes such as grass encroachment that determine the conservation status of Natura 2000 heathland areas to a large extent. A limitation is that both advanced remote sensing approaches and traditional field based vegetation surveys seem to cause over and underestimations of grass encroachment for specific categories, but the first provides a better basis for monitoring if specific species are not directly considered

Kinematics of parsec-scale structures in AGN: the 2cm VLBA Survey

We are investigating the kinematics of jets in active galactic nuclei on parsec scales by studying a representative population of sources. This study is being carried out using the Very Long Baseline Array at 15 GHz, with more than 800 images taken since 1994. In this contribution we present an overview of the diversity of kinematics for a complete sample of sources.Comment: Proceedings of the 6th European VLBI Network Symposium, Ros E., Porcas R.W., Lobanov, A.P., & Zensus, J.A. (eds), MPIfR, Bonn, Germany. 2 pages, 3 figures, needs evn2002.cls style fil

Intrinsic Brightness Temperatures of AGN Jets

We present a new method for studying the intrinsic brightness temperatures of the parsec-scale jet cores of Active Galactic Nuclei (AGN). Our method uses observed superluminal motions and observed brightness temperatures for a large sample of AGN to constrain the characteristic intrinsic brightness temperature of the sample as a whole. To study changes in intrinsic brightness temperature, we assume that the Doppler factors of individual jets are constant in time as justified by their relatively small changes in observed flux density. We find that in their median-low brightness temperature state, the sources in our sample have a narrow range of intrinsic brightness temperatures centered on a characteristic temperature, T_int = 3 x 10^10 K, which is close to the value expected for equipartition, when the energy in the radiating particles equals the energy stored in the magnetic fields. However, in their maximum brightness state, we find that sources in our sample have a characteristic intrinsic brightness temperature greater than 2 x 10^11 K, which is well in excess of the equipartition temperature. In this state, we estimate the energy in radiating particles exceeds the energy in the magnetic field by a factor of ~ 10^5. We suggest that the excess of particle energy when sources are in their maximum brightness state is due to injection or acceleration of particles at the base of the jet. Our results suggest that the common method of estimating jet Doppler factors by using a single measurement of observed brightness temperature and/or the assumption of equipartition may lead to large scatter or systematic errors in the derived values.Comment: 4 pages, 2 figures, Accepted to Appear in ApJ Letter

Lack of knowledge and experience highlights the need for a clear paediatric organ and tissue donation protocol in the Netherlands

Aim This study explored the attitudes of medical professionals to organ and tissue donation in paediatric intensive care units (PICUs) and neonatal intensive care units (NICUs) in the Netherlands. It also examined their compliance with the existing Dutch donation protocol and assessed whether a paediatric donation protocol was needed. Methods We invited 966 professionals working in all eight PICUs and the two largest NICUs to complete an online survey from December 2016 until April 2017. Results A quarter (25%) took part and they included PICU intensivists, neonatologists, nurses and other health and allied professionals. Most were female and nurses. More than half (54%) of the PICU respondents considered paediatric organ donation to be very important and 53% supported tissue donation. In contrast, only 22% of the NICU respondents believed that both neonatal organ and tissue donation were very important. Familiarity and compliance with the existing national donation protocol were low. PICU nurses had significantly less experience than PICU intensivists and felt less comfortable with the donation process. None of the NICU respondents had prior donation experience. Conclusion Paediatric intensive care units and NICU professionals lack specialised knowledge and experience on organ and tissue donation. A comprehensive and clear paediatric donation protocol is clearly needed