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New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241Am(n,γ) cross section at the n_TOF facility between 0.2 eV and 10 keV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241Am(n,γ) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.
The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combining different neutron beams and techniques. The thermal point was determined at the Budapest Research Reactor by means of Neutron Activation Analysis and Prompt Gamma Analysis, and the resolved (1 eV - 4 keV) and unresolved (1 - 500 keV) resonance regions were measured using a set of four Total Energy detectors at the CERN n_TOF-EAR1.
The accuracy on neutron capture cross section of fissile isotopes must be improved for the design of future nuclear systems such as Gen-IV reactors and Accelerator Driven Systems. The High Priority Request List of the Nuclear Energy Agency, which lists the most important nuclear data requirements, includes also the neutron capture cross sections of fissile isotopes such as 233,235U and 239,241Pu. A specific experimental setup has been used at the CERN n_TOF facility for the measurement of the neutron capture cross section of 235U by a set of micromegas fission detectors placed inside a segmented BaF2 Total Absorption Calorimeter.
The experimental area 2 (EAR-2) at CERNs neutron time-of-flight facility (n_TOF), which is operational since 2014, is designed and built as a short-distance complement to the experimental area 1 (EAR-1). The Parallel Plate Avalanche Counter (PPAC) monitor experiment was performed to characterize the beam pro↓le and the shape of the neutron 'ux at EAR-2. The prompt γ-flash which is used for calibrating the time-of-flight at EAR-1 is not seen by PPAC at EAR-2, shedding light on the physical origin of this γ-flash.
Anorexia nervosa (AN) is a complex neuropsychiatric disorder presenting with dangerously low body weight, and a deep and persistent fear of gaining weight. To date, only one genome-wide significant locus associated with AN has been identified. We performed an exome-chip based genome-wide association studies (GWAS) in 2158 cases from nine populations of European origin and 15 485 ancestrally matched controls. Unlike previous studies, this GWAS also probed association in low-frequency and rare variants. Sixteen independent variants were taken forward for in silico and de novo replication (11 common and 5 rare). No findings reached genome-wide significance. Two notable common variants were identified: rs10791286, an intronic variant in OPCML (P=9.89 × 10−6), and rs7700147, an intergenic variant (P=2.93 × 10−5). No low-frequency variant associations were identified at genome-wide significance, although the study was well-powered to detect low-frequency variants with large effect sizes, suggesting that there may be no AN loci in this genomic search space with large effect sizes.
The CRISPR/Cas9 prokaryotic adaptive immune system and its swift repurposing for genome editing enables modification of any prespecified genomic sequence with unprecedented accuracy and efficiency, including targeted gene repair. We used the CRISPR/Cas9 system for targeted repair of patient-specific point mutations in the Cytochrome b-245 heavy chain gene (CYBB), whose inactivation causes chronic granulomatous disease (XCGD)—a life-threatening immunodeficiency disorder characterized by the inability of neutrophils and macrophages to produce microbicidal reactive oxygen species (ROS). We show that frameshift mutations can be effectively repaired in hematopoietic cells by non-integrating lentiviral vectors carrying RNA-guided Cas9 endonucleases (RGNs). Because about 25% of most inherited blood disorders are caused by frameshift mutations, our results suggest that up to a quarter of all patients suffering from monogenic blood disorders could benefit from gene therapy employing personalized, donor template-free RGNs.
The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity and demands the redirection of scientific efforts and criteria to organized research projects. The international COVID19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in COVID19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalog of a holistic SARS-CoV-2 protein preparation approach based on the consortium’s collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope-labeled form.
Mit der Neuregelung der Studienplatzverteilung von 2005 haben die Universitäten in Deutschland die Möglichkeit, bis zu 60% der Studienplätze nach universitätseigenen Kriterien zu vergeben. Implizit wird vom Gesetzgeber und der öffentlichen Meinung gefordert, nicht-leistungsbezogene Kriterien und Persönlichkeitsmerkmale verstärkt zur Bewerberauswahl einzusetzen (Motivation, Identifikation, Vermeidung von Fehlvorstellungen). Da in Anbetracht der Bewerberzahlen mündliche Auswahlgespräche als ungeeignet erscheinen, wurde vom Fachbereich Medizin der Johann Wolfgang Goethe Universität ein Fragebogen entworfen, um nichtschulische Leistungen zu erfassen. Dieser Fragebogen wurde am Beginn des Wintersemesters 2005/2006 von allen Studienanfängern der JWG-Universität Frankfurt und der Medizinischen Universität Innsbruck ausgefüllt. Entgegen der initialen Erwartungen der Verfasser gaben nur etwa 15% Prozent Medizin-spezifische berufliche Vorerfahrungen an (Rettungsdienst, Ausbildung als Krankenschwester/pfleger oder ähnliches); dagegen wurden von etwa 60% angegeben, mindestens ein Musikinstrument zu spielen oder länger sportlich aktiv gewesen zu sein. Die Zusammenstellung der Selbstangaben zeigt, dass Medizin-relevante Vorkenntnisse nur bei einem kleinen Anteil der Studienbewerber in größerem Umfang vorhanden sind. Aufgrund der großen Streuung in der Art und Dauer der angegebenen Vorleistungen sollte die Erhebung von Parametern zur Beurteilung von soft skills, z.B. durch Online-Fragebogen, als (Vor)Selektionsinstrument nur sehr vorsichtig eingesetzt werden.
Multiple choice (MC)-Klausuren sind im deutschen Medizinstudium trotz weitgehend fehlender Daten zur Validität dieser Prüfungsform zur Regelprüfung geworden. Darüber hinaus ist unklar, in welchem Ausmaß die Studierenden - auch solche mit guten Prüfungsergebnissen - den geprüften Lernstoff tatsächlich beherrschen. Am Fachbereich Medizin der Johann-Wolfgang-Goethe-Universität Frankfurt wurde am Ende des SS 2003 im Fach Mikrobiologie für die Studierenden des 2. klinischen Semesters eine MC-basierte Abschlussprüfung geschrieben. Die Studierenden des 1. klinischen Semesters hatten - bedingt durch Umstellungen des Curriculums - eine identische Ausbildung. Diese wurde durch eine inhaltlich weitgehend identische, im Format aber andere Klausur abgeschlossen, in der sowohl offene Fragen enthalten waren als auch Fragen, bei denen die Studierenden jede Aussage einzeln auf Korrektheit bewerten mussten. Der Vergleich der Ergebnisse für inhaltlich gleiche Fragen zeigt, dass die Studierenden im MC-Format eine hohe Quote richtiger Antworten erzielen, diese jedoch durch ein geändertes Fragenformat stark reduziert wird. So erreichten nur 20 - 30% der Studierenden ein vollständig richtiges Ergebnis, wenn jede Aussage einzeln bewertet werden musste, während die inhaltlich gleiche Frage im MC-Format 80 - 90% richtige Ergebnisse erzielte. In freien Fragen konnten nur 30 - 40% der Studierenden die richtige Antwort aktiv niederschreiben, während 90 -99% der Studierenden die richtige Lösung passiv erkannten. Wir interpretieren diese Ergebnisse dahin, dass der Entscheidungszwang in MC-basierten Fragen einen starken Einfluss auf die Quote richtiger Antworten hat, und die Prüfungsergebnisse damit wesentlich durch das Format beeinflusst werden, das Wissen dagegen nicht beherrscht wird. Die Ergebnisse dieser Studie legen nahe, Sorgfalt bei der Auswahl des Prüfungsverfahrens walten zu lassen und der Steuerung des studentischen Lernverhaltens durch das Prüfungsformat wesentlich mehr Aufmerksamkeit zu widmen als bisher.
he study of the resonant structures in neutron-nucleus cross-sections, and therefore of the compound-nucleus reaction mechanism, requires spectroscopic measurements to determine with high accuracy the energy of the neutron interacting with the material under study.
To this purpose, the neutron time-of-flight facility n_TOF has been operating since 2001 at CERN. Its characteristics, such as the high intensity instantaneous neutron flux, the wide energy range from thermal to few GeV, and the very good energy resolution, are perfectly suited to perform high-quality measurements of neutron-induced reaction cross sections. The precise and accurate knowledge of these cross sections plays a fundamental role in nuclear technologies, nuclear astrophysics and nuclear physics.
Two different measuring stations are available at the n_TOF facility, called EAR1 and EAR2, with different characteristics of intensity of the neutron flux and energy resolution. These experimental areas, combined with advanced detection systems lead to a great flexibility in performing challenging measurement of high precision and accuracy, and allow the investigation isotopes with very low cross sections, or available only in small quantities, or with very high specific activity.
The characteristics and performances of the two experimental areas of the n_TOF facility will be presented, together with the most important measurements performed to date and their physics case. In addition, the significant upcoming measurements will be introduced.