513 research outputs found

    Toward a script theory of guidance in computer-supported collaborative learning

    Get PDF
    This article presents an outline of a script theory of guidance for computer-supported collaborative learning (CSCL). With its four types of components of internal and external scripts (play, scene, role, and scriptlet) and seven principles, this theory addresses the question how CSCL practices are shaped by dynamically re-configured internal collaboration scripts of the participating learners. Furthermore, it explains how internal collaboration scripts develop through participation in CSCL practices. It emphasizes the importance of active application of subject matter knowledge in CSCL practices, and it prioritizes transactive over non-transactive forms of knowledge application in order to facilitate learning. Further, the theory explains how external collaboration scripts modify CSCL practices and how they influence the development of internal collaboration scripts. The principles specify an optimal scaffolding level for external collaboration scripts and allow for the formulation of hypotheses about the fading of external collaboration scripts. Finally, the article points towards conceptual challenges and future research questions

    37 GHz observations of narrow-line Seyfert 1 galaxies

    Get PDF
    Observations at 37 GHz, performed at Mets\"ahovi Radio Observatory, are presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1 (NLS1) galaxies, together with additional lower and higher frequency radio data from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most of the data have been gathered between February 2012 and April 2015 but for some sources even longer lightcurves exist. The detection rate at 37 GHz is around 19%, comparable to other populations of active galactic nuclei presumed to be faint at radio frequencies, such as BL Lac objects. Variability and spectral indices are determined for sources with enough detections. Based on the radio data, many NLS1 galaxies show a blazar-like radio spectra exhibiting significant variability. The spectra at a given time are often inverted or convex. The source of the high-frequency radio emission in NLS1 galaxies, detected at 37 GHz, is most probably a relativistic jet rather than star formation. Jets in NLS1 galaxies are therefore expected to be a much more common phenomenon than earlier assumed.Comment: Accepted for publication in A&A. Table of 37 GHz data will be available at the CDS soo

    Near-infrared morphologies of the host galaxies of narrow-line Seyfert 1 galaxies

    Get PDF
    We present J-band near-infrared (NIR) imaging of the host galaxies of nine narrow-line Seyfert 1 galaxies (NLS1). Based on highfrequency radio observations at 37 GHz, seven of them could host powerful jets that are most likely relativistic. Host galaxy morphology studies of NLS1 galaxies are scarce, but exceedingly important for understanding the seemingly heterogeneous nature of the NLS1 population as well as their evolution and place in the active galactic nuclei (AGN) scheme. Increasing the sample size is essential for achieving statistically significant results. We determine the morphological types of the host galaxies by performing photometric decomposition of NIR images using a 2D image decomposition algorithm GALFIT. We were able to sufficiently model five of the nine host galaxies. Based on the fitting parameters, mainly the Sersic index, all five are disk-like galaxies. Sources with clearly distinguishable bulge components all have pseudo-bulges, and four out of five sources show a component resembling a bar. A surprisingly large fraction, three out of five, show signs of interaction or disturbed morphology. Our results suggest that spiral galaxies with pseudo-bulges are able to launch and maintain powerful jets. They also imply that interaction - mainly minor mergers - may have a role in initially triggering higher levels of nuclear activity in NLS1 galaxies. Furthermore, our results support the heterogeneous nature of the NLS1 class and indicate that this diversity is caused by different evolutionary stages, possibly due to mergers

    Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

    Full text link
    We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections.Comment: 5 pages, 1 figure, 37 GHz data available in electronic form at the CDS. Accepted in A&

    ANALISIS DAMPAK INDUSTRI 4.0 TERHADAP SISTEM PENGAWASAN KETENAGANUKLIRAN DI INDONESIA

    Get PDF
    ANALISIS DAMPAK INDUSTRI 4.0 TERHADAP SISTEM PENGAWASAN KETENAGANUKLIRAN DI INDONESIA. Telah dilakukan suatu kajian mengenai pengaruh gelombang Industri 4.0 terhadap sistem pengawasan ketenaganukliran di Indonesia. Industri 4.0 adalah istilah yang diterapkan pada berbagai transformasi yang demikian cepat dalam desain, manufaktur, operasi, serta layanan produk dan sistem produksi. Penggunaan 4.0 menandakan bahwa ini adalah revolusi industri keempat di dunia, meneruskan tiga lompatan besar sebelumnya, yatu: Manufaktur mesin uap dan air, produksi massal bertenaga listrik berbasis pembagian kerja, dan zaman elektronika dan teknologi informasi dengan otomatisasi tugas-tugas rumit. Berbagai penelitian menyebutkan bahwa Industri 4.0 mengubah banyak hal, termasuk: meningkatnya fleksibilitas produksi, kustomisasi massal, produktivitas, mutu produk, keterlibatan pelanggan dalam proses desain, semakin mendekatnya lokasi produksi ke pelanggan, dan model bisnis. Semua perkembangan ini tentunya harus diantisipasi oleh Badan Pengawas. Dengan demikian, tujuan dari kajian ini adalah untuk mengevaluasi hal-hal yang sudah atau perlu dilakukan oleh BAPETEN dalam rangka menyongsong era Industri 4.0. Kajian dilakukan dengan metode deskriptif, analitik dan kualitatif yang dilengkapi dengan studi literatur dan pengamatan praktik-praktik yang ada di BAPETEN. Kajian ini menyimpulkan bahwa BAPETEN sebagian telah melakukan antisipasi akan datangnya era Industri 4.0, namun masih ada banyak peluang untuk peningkatan

    Preoperative and perioperative use of levosimendan in cardiac surgery: European expert opinion

    Get PDF
    In cardiac surgery, postoperative low cardiac output has been shown to correlate with increased rates of organ failure and mortality. Catecholamines have been the standard therapy for many years, although they carry substantial risk for adverse cardiac and systemic effects, and have been reported to be associated with increased mortality. On the other hand, the calcium sensitiser and potassium channel opener levosimendan has been shown to improve cardiac function with no imbalance in oxygen consumption, and to have protective effects in other organs. Numerous clinical trials have indicated favourable cardiac and non-cardiac effects of preoperative and perioperative administration of levosimendan. A panel of 27 experts from 18 countries has now reviewed the literature on the use of levosimendan in on-pump and off-pump coronary artery bypass grafting and in heart valve surgery. This panel discussed the published evidence in these various settings, and agreed to vote on a set of questions related to the cardioprotective effects of levosimendan when administered preoperatively, with the purpose of reaching a consensus on which patients could benefit from the preoperative use of levosimendan and in which kind of procedures, and at which doses and timing should levosimendan be administered. Here, we present a systematic review of the literature to report on the completed and ongoing studies on levosimendan, including the newly commenced LEVO-CTS phase III study (NCT02025621), and on the consensus reached on the recommendations proposed for the use of preoperative levosimendan
    • …
    corecore