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We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n_TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process.
Above 1 MeV of incident neutron energy the fission fragment angular distribution (FFAD) has generally a strong anisotropic behavior due to the combination of the incident orbital momentum and the intrinsic spin of the fissioning nucleus. This effect has to be taken into account for the efficiency estimation of devices used for fission cross section measurements. In addition it bears information on the spin deposition mechanism and on the structure of transitional states. We designed and constructed a detection device, based on Parallel Plate Avalanche Counters (PPAC), for measuring the fission fragment angular distributions of several isotopes, in particular 232Th. The measurement has been performed at n_TOF at CERN taking advantage of the very broad energy spectrum of the neutron beam. Fission events were recognized by back to back detection in coincidence in two position-sensitive detectors surrounding the targets. The detection efficiency, depending mostly on the stopping of fission fragments in backings and electrodes, has been computed with a Geant4 simulation and validated by the comparison to the measured case of 235U below 3 keV where the emission is isotropic. In the case of 232Th, the result is in good agreement with previous data below 10 MeV, with a good reproduction of the structures associated to vibrational states and the opening of second chance fission. In the 14 MeV region our data are much more accurate than previous ones which are broadly scattered.
Als Teil der kommunalen Daseinsvorsorge unterliegt die Siedlungswasserwirtschaft den Ansprüchen, nachhaltig und zukunftsfähig zu sein. Klimawandel, demographische Entwicklungen, veränderte politische Rahmensetzungen und rechtliche Vorgaben stellen die kommunalen Unternehmen der Siedlungswasserwirtschaft vor neue Herausforderungen. Ihre Zukunftsfähigkeit ist daher eng mit der Frage verknüpft, welche Entwicklungen – seien sie extern oder intern verursacht – die eigene Leistungsfähigkeit einschränken und die Nachhaltigkeit gefährden können.
Das vorliegende Diskussionspapier skizziert das Zielbündel für eine nachhaltige Wasserversorgung und Abwasserbeseitigung und bildet zugleich den Ausgangspunkt für die Betrachtung von Nachhaltigkeitsrisiken. Es stellt mithin einen aktuellen Arbeitsstand dar, der mit den Praxispartnern aus dem Projektverbund NaCoSi und der Fachöffentlichkeit diskutiert werden soll.
The neutron sensitivity of the C6D6 detector setup used at n_TOF facility for capture measurements has been studied by means of detailed GEANT4 simulations. A realistic software replica of the entire n_TOF experimental hall, including the neutron beam line, sample, detector supports and the walls of the experimental area has been implemented in the simulations. The simulations have been analyzed in the same manner as experimental data, in particular by applying the Pulse Height Weighting Technique. The simulations have been validated against a measurement of the neutron background performed with a natC sample, showing an excellent agreement above 1 keV. At lower energies, an additional component in the measured natC yield has been discovered, which prevents the use of natC data for neutron background estimates at neutron energies below a few hundred eV. The origin and time structure of the neutron background have been derived from the simulations. Examples of the neutron background for two different samples are demonstrating the important role of accurate simulations of the neutron background in capture cross-section measurements.
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 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 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.
Mexico’s role in the US-Central American migration regime is threefold: not only is it a country of origin, and a transit country, but also increasingly becoming a receiving country for migrants who flee from violence, insecurity and poverty. The Mexican state responds with detention enforcement. Clinical research usually puts emphasise on the negative impact of detention enforcement on the detainees‘ mental health. Yet, it often disregards the spatial configurations of detention centres and their socio-political context. This study aims to fill this gap by analysing how such factors create harmful environments that affect both the detainees‘ mental health and their social life in Mexico’s migration detention centres. The study’s mixed method approach builds on semi-structured interviews with a sample of N = 56 migrants of diverse nationalities and varying socioeconomic status of whom 22 were still detained while 34 had been released. The interviews include the Torturing Environment Scale (TES), a novel instrument for the analysis of detention environments, as well as clinical psychological measures of emotional distress. Additional n = 10 in-depth interviews with human rights advocates to explore the interconnections between the detention environments, their impact on mental health, and Mexican migration politics. Facultative counter-mappings of the detention centres complement the interviews. Without exception, all interviews of detainees underline that the manipulation of detention conditions creates torturing environments that cause harm to basic physiological and psychological needs. A comparison between detained vs. released interviewees revealed lasting feelings of fear and shame. The study emphasises that immigration detention immobilises migrants in a necropolitical limbo, which destroys hope as much as human integrity. It indicates that detention is part of deterrence politics, which perpetuates harm and inequality through detention and deportation. Highlighting structural human rights violations, the findings stress the need to review current migration policies.