Elastic Recoil Detection Analysis

International audienceAmong the family of Ion Beam Analysis techniques for material characterization, Elastic Recoil Detection Analysis (ERDA) exploits the spectroscopy of recoil nuclei moving under the impact of the ions of the beam. This technique is well suited to light elements profiling, especially for hydrogen measurements which can be performed with usual helium-4 beams available in most facilities. This chapter presents an overview of ERDA main features and focuses on a selection of recent papers dealing with hydrogen measurements in materials for miscellaneous applications, divided into four sections: metals, ceramics, minerals, and thin films

Wie beeinflusst Basel II die Kreditkonditionen von öffentlich-rechtlichen Körperschaften? Empirische Befunde aus der Schweiz

Wir untersuchen die Effekte von Basel II auf Kredite, die in den Jahren 2006 und 2007 (also vor und nach Inkrafttreten der neuen Regulierungen) an schweizer Städte und Gemeinden vergeben wurden. In einer empirischen Analyse bewerteten wir deren jeweilige Bonität, sowie die Margen ihrer Kredite. Es zeigte sich, dass durch Basel II die Margen bei Banken als Kreditgeber generell sanken, nicht jedoch bei anderen Kreditgebern. Auch nahm bei Banken die Abhängigkeit der Margen von der Bonität des Kreditnehmers zu. Desweiteren gab es signifikante Unterschiede zwischen den Kreditkonditionen je nach Kreditgeber und Modalitäten der Kreditvergabe, wie zum Beispiel eine Verlängerung eines bestehenden Kredites. Diese Erkenntnisse könnten für Städte und Gemeinden ein erhebliches Einsparungspotential bieten.We study effects of Basel II on credits for Swiss towns and cities in the years 2006 (before Basel II) and 2007 (after Basel II). We collected data of these loans and computed their margins. Moreover we collected data on the financial situation of the towns and cities and used this to compute a credit ranking for each town and city. We show that Basel II decreased the margins when banks were the creditor, but not when other institutions (e.g. pension funds) provided the loan. With banks also the impact of the credit ranking increased after Basel II. We also find significant effects of the type of the creditor and of the circumstances of the loan acquisition on the margins. In particular, we find that new loans are generally cheaper than extensions of existing loans. Our results shed some light on the effects of Basel II, but can also have potential to decrease the costs for towns and cities when acquiring loans

Paradigmen der Pandemiebekämpfung und ihre Öffentlichkeit

Der im März 2020 in der Bundesrepublik wie in anderen Staaten erlassene Lockdown stellt eine bis heute eher selten thematisierte Abweichung von den bis dahin vorliegenden Pandemieplanungen dar. Mit den Lockdowns setzte sich eine sogenannte Suppressions-Strategie durch, die in niedrigen Inzidenzen die einzig vertretbare Möglichkeit des Infektionsschutzes sah. Der vorliegende Beitrag widmet sich der erklärenden Darstellung dieser Zäsur. Im Zentrum der Erklärung stehen zwei Faktoren: Erstens die verhältnismäßig größere medial-öffentliche Aufmerksamkeit für wissenschaftliche Positionspapiere, die sich für Suppression statt der – eher klassischen – Mitigationsstrategie einsetzten; zweitens schließlich treten zu strukturellen kulturelle Faktoren, die eine Präferenz für Schutz, Prävention und generell einem ‚Mehr‘ an Maßnahmen aufweisen

Social memory and the knowledge politics of school closures during the COVID-19 pandemic

This paper examines a specific form of mass media memory of the 1918 influenza pandemic during the COVID-19 pandemic. The mass media memory of political interventions during the 1918 influenza pandemic functioned as an interpretive framework at the beginning of the pandemic: state measures in the present are justified by proven measures in the past. The selectivity of memory reduces the complexity of a political decision-making process under conditions of epistemic uncertainty. The hypothesis is elaborated using the example of school closures across Germany in March 2020

Zwei Wochen im März: zum Zusammenspiel von Medien, Wissenschaft und Politik während der SARS-CoV-2 Pandemie

Weltweit reagierten Staaten mit sogenannten nicht-pharmazeutischen Interventionsmaßnahmen auf die Ausbreitung von SARS-CoV-2. Dabei sticht nicht nur die Homogenität vieler Maßnahmen hervor, sondern auch deren Strenge, die zuvor kein Gegenstand von Pandemieplanung gewesen ist, sich seit März 2020 jedoch im Instrumentenkasten politischer Steuerung wiederfindet. Warum das so ist, zu dieser Frage nimmt der folgende Aufsatz eine differenzierungstheoretische Perspektive ein und legt den Schwerpunkt auf die Inter-Systembeziehungen von Medien, Politik und Wissenschaft. Unter Rückgriff auf die Medialisierungshypothese erklärt er Tempo, Form und Intensität des Geschehens im März 2020

First tests of a 800 kJ HTS SMES

SMES using high critical temperature superconductors are interesting for high power pulsed sources. Operation at temperatures above 20 K makes cryogenics easier, enhances stability and improves operation as pulsed power source. In the context of a DGA (Delegation Generate pour l'Armement) project, we have designed and constructed a 800 kJ SMES. The coil is wound with Nexans conductors made of Bi-2212 PIT tapes soldered in parallel. The coil consists in 26 superposed simple pancakes wound and bonded on sliced copper plates coated with epoxy. The rated current is 315 A for an energy of 814 kJ. The external diameter of the coil is 814 mm and its height 222 mm. The cooling at 20 K is only performed by conduction from cryocoolers to make cryogenics very friendly and invisible for the SMES users. The cooling down has been successfully carried out and the thermal system works as designed. After a brief description of the SMES design and construction, some tests will be presented. From a current of 244 A, the SMES delivered 425 kJ to a resistance with a maximum power of 175 kW.Comment: 5 page

Electronic Band Dispersion of Graphene Nanoribbons via Fourier-Transformed Scanning Tunneling Spectroscopy

Atomically precise armchair graphene nanoribbons of width $N=7$ (7-AGNRs) are investigated by scanning tunneling spectroscopy (STS) on Au(111). The analysis of energy-dependent standing wave patterns of finite length ribbons allows, by Fourier transformation, the direct extraction of the dispersion relation of frontier electronic states. Aided by density functional theory calculations, we assign the states to the valence band, the conduction band and the next empty band of 7-AGNRs, determine effective masses of $0.42\pm 0.08\,m_e$, $0.40\pm 0.18\,m_e$ and $0.20\pm 0.03\,m_e$, respectively, and a band gap of $2.37\pm 0.06$ eV.Comment: 20 pages, 7 figure

Nuclear Microprobe using Elastic Recoil Detection (ERD) for Hydrogen Profiling in High Temperature Protonic Conductors

The interaction between hydrogen and various high temperature protonic conductors (HTPC) has not been clearly understood due to poor densification and unreacted secondary phases. the melt-processing technique is used in producing fully dense simple SrCe(0.9)Y (0.10) O(3-delta) and complex Sr3Ca(1+x)Nb(2+x)O(9-delta) perovskites that can not be achieved by solid-state sintering. the possibilities of ion beam analysis have been investigated to quantify hydrogen distribution in HTPC perovskites subjected to water heat treatment. Nuclear microprobe technique is based on the interactions of a focused ion beam of MeV light ions (H-1, H-2, He-3, He-4,.) with the sample to be analyzed to determine local elemental concentrations at the cubic micrometer scale, the elastic recoil detection analysis technique (ERDA) has been carried out using He-4(+) microbeams and detecting the resulting recoil protons. Mappings of longitudinal sections of water treated SrCeO3 and Sr(Ca(1/3)Nb(2/3))O3 perovskites have been achieved, the water treatment strongly alters the surface of simple SrCe(0.9)Y(0.10)O(3-delta) perovskite. From Rutherford Back Scattering measurements (RBS), both Ce depletion and surface re-deposition is evidenced. the ERDA investigations on water treated Sr3Ca(1+x)Nb(2+x)O(9-delta) perovskite did not exhibit any spatial difference for the hydrogen incorporation from the surface to the centre. the amount of hydrogen incorporation for Sr3Ca(1+x)Nb(2+x)O(9-delta) was low and required further development of two less conventional techniques, ERDA in forward geometry and forward elastic diffusion H-1(p,p) H-1 with coincidence detection

Luminescence from two-dimensional electron gases in InAlN/GaN heterostructures with different In content

The luminescence properties of InxAl1−xN/GaN heterostructures are investigated systematically as a function of the In content (x = 0.067 − 0.208). The recombination between electrons confined in the two-dimensional electron gas and free holes in the GaN template is identified and analyzed. We find a systematic shift of the recombination with increasing In content from about 80 meV to only few meV below the GaN exciton emission. These results are compared with model calculations and can be attributed to the changing band profile and originating from the polarization gradient between InAlN and GaN

Characterisation of human glioma resections by Fast Field-Cycling NMR

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