Bright Coherent Ultrahigh Harmonics in the keV X-ray Regime from Mid-Infrared Femtosecond Lasers

High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo–electron volts, allowing, in principle, the generation of pulses as short as 2.5 attoseconds. The multiatmosphere gas pressures required for bright, phase-matched emission also support laser beam self-confinement, further enhancing the x-ray yield. Finally, the x-ray beam exhibits high spatial coherence, even though at high gas density the recolliding electrons responsible for HHG encounter other atoms during the emission process.The experimental work was funded by a National Security Science and Engineering Faculty Fellowship, and the NSF Center for EUV Science and Technology. A.G., A.J.-B., M.M.M., H.C.K. and A. Becker acknowledge support for theory from the U.S. Air Force Office of Scientific Research (grant no. FA9550-10-1-0561); A. Baltuška acknowledges support from Austrian Science Fund (FWF, grant no. U33-16) and the Austrian Research Promotion Agency (FFG, Project 820831 UPLIT); and C.H.-G. and L.P. acknowledge support from Junta de Castilla y León, Spanish MINECO (CSD2007-00013 and FIS2009-09522), and from Centro de Láseres Pulsados, CLPU. T.P., M.-C.C., A. Bahabad, M.M.M. and H.C.K. have filed for a patent on “Method for phase-matched generation of coherent soft and hard X-rays using IR lasers,” U.S. patent application 61171783 (2008)

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

An Evaluation among final-year-students in internal medicine

Main emphasis in terms of clinical practice is put on final year medical education at German universities. Portfolios or logbooks are often used to ensure standards and a structured training. However, only few studies are available that investigated the personal benefit of a logbook for the students. To validate the logbooks' acceptance, its integrative function and impact on quality of final year students' medical education, we designed and evaluated a task-based logbook for Internal Medicine at the Heidelberg University Hospital.By longitudinal analysis of two cohorts (before and after logbook introduction), we were able to show that after logbook introduction, students felt more integrated in ward routine and considered the dedicated training periods by ward doctors to be more sufficient. Furthermore, students stated to have performed more ward rounds and to have written more discharge letters. General satisfaction with their clerkship also increased significantly. However, an additional survey after this training period showed that many of the obligatory clinical tasks were not performed as documented in the logbooks.We conclude that a task-based logbook is an appropriate tool to enhance communication between students and doctors on ward, facilitating integration on ward by giving the students the chance to claim teaching actively. Although the documentation of clinical tasks in the logbook hasn't proved to be really effective, we consider this tool as an useful structuring element that enhances students' satisfaction in practical medical training.Das Praktische Jahr stellt einen Schwerpunkt der praxisbezogenen klinischen Ausbildung von Medizinstudenten dar. Häufig werden Logbücher oder Portfolios eingesetzt, um eine standardisierte und strukturierte Ausbildung zu gewährleisten. Es existieren jedoch nur wenige Untersuchungen, welche den persönlichen Nutzen eines Logbuchs für die Studenten untersucht haben. Um die Akzeptanz, die integrative Funktion und den Einfluss eines Logbuchs auf die Ausbildungsqualität zu prüfen, haben wir Nutzung und Effekt eines tätigkeitsbezogenen Logbuchs in der Inneren Medizin am Universitätsklinikum Heidelberg untersucht. Im longitudinalen Vergleich zweiter Kohorten (vor/nach Einführung des Logbuchs) konnte gezeigt werden, dass sich die Studenten nach Logbuch-Einführung besser in den Routinebetrieb integriert fühlten und die für sie aufgebrachte Zeit der ausbildenden Ärzte als ausreichender wahrnahmen. Außerdem gaben die Studenten nach Einführung des Logbuchs vermehrt an, eigenständig Visiten durchgeführt und Arztbriefe erstellt zu haben. Auch die Gesamtbewertung des Ausbildungsabschnitts verbesserte sich nach Einführung des Logbuchs signifikant. Allerdings ergab eine Nachbefragung der PJ-Studenten, dass geforderte klinische Tätigkeiten, obwohl in den Logbüchern so dokumentiert, in der Realität zu einem überwiegenden Teil nicht geleistet worden waren. Wir sehen in einem Logbuch ein geeignetes Mittel, um die Arzt-Studenten Kommunikation als auch die Integration der Studenten auf Station zu verbessern, da Lehrinhalte seitens der Studenten aktiv eingefordert werden können. Obwohl sich das Logbuch zur Dokumentation eines Tätigkeitskatalogs nur eingeschränkt bewährt hat, führt es als Strukturelement insgesamt zu einer höheren Zufriedenheit der PJ-Studenten