The Lamb shift in muonic hydrogen

The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the 2S1/2F=1–2P3/2F=2 energy splitting (Pohl et al., Nature, 466, 213 (2010)) in μp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of rp = 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S–2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R∞ = 10 973 731.568 160 (16) m⁻¹ and the rms charge radius of the deuteron rd = 2.128 09 (31) fm

Dynamic deformation of metastable austenitic stainless steels at the nanometric length scale

Cyclic indentation was used to evaluate the dynamic deformation on metastable steels, particularly in an austenitic stainless steel, AISI 301LN. In this work, cyclic nanoindentation experiments were carried out and the obtained loading-unloading (or P-h) curves were analyzed in order to get a deeper knowledge on the time-dependent behavior, as well as the main deformation mechanisms. It was found that the cyclic P-h curves present a softening effect due to several repeatable features (pop-in events, ratcheting effect, etc.) mainly related to dynamic deformation. Also, observation by transmission electron microscopy highlighted that dislocation pile-up is the main responsible of the secondary pop-ins produced after certain cycles.Peer ReviewedPostprint (author's final draft

Enhancing studies of the connectome in autism using the autism brain imaging data exchange II

The second iteration of the Autism Brain Imaging Data Exchange (ABIDE II) aims to enhance the scope of brain connectomics research in Autism Spectrum Disorder (ASD). Consistent with the initial ABIDE effort (ABIDE I), that released 1112 datasets in 2012, this new multisite open-data resource is an aggregate of resting state functional magnetic resonance imaging (MRI) and corresponding structural MRI and phenotypic datasets. ABIDE II includes datasets from an additional 487 individuals with ASD and 557 controls previously collected across 16 international institutions. The combination of ABIDE I and ABIDE II provides investigators with 2156 unique cross-sectional datasets allowing selection of samples for discovery and/or replication. This sample size can also facilitate the identification of neurobiological subgroups, as well as preliminary examinations of sex differences in ASD. Additionally, ABIDE II includes a range of psychiatric variables to inform our understanding of the neural correlates of co-occurring psychopathology; 284 diffusion imaging datasets are also included. It is anticipated that these enhancements will contribute to unraveling key sources of ASD heterogeneity

A Prospective Evaluation of Infant Cerebellar-Cerebral Functional Connectivity in Relation to Behavioral Development in Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder diagnosed based on social impairment, restricted interests, and repetitive behaviors. Contemporary theories posit that cerebellar pathology contributes causally to ASD by disrupting error-based learning (EBL) during infancy. The present study represents the first test of this theory in a prospective infant sample, with potential implications for ASD detection. Methods: Data from the Infant Brain Imaging Study (n = 94, 68 male) were used to examine 6-month cerebellar functional connectivity magnetic resonance imaging in relation to later (12/24-month) ASD-associated behaviors and outcomes. Hypothesis-driven univariate analyses and machine learning–based predictive tests examined cerebellar–frontoparietal network (FPN; subserves error signaling in support of EBL) and cerebellar–default mode network (DMN; broadly implicated in ASD) connections. Cerebellar-FPN functional connectivity was used as a proxy for EBL, and cerebellar-DMN functional connectivity provided a comparative foil. Data-driven functional connectivity magnetic resonance imaging enrichment examined brain-wide behavioral associations, with post hoc tests of cerebellar connections. Results: Cerebellar-FPN and cerebellar-DMN connections did not demonstrate associations with ASD. Functional connectivity magnetic resonance imaging enrichment identified 6-month correlates of later ASD-associated behaviors in networks of a priori interest (FPN, DMN), as well as in cingulo-opercular (also implicated in error signaling) and medial visual networks. Post hoc tests did not suggest a role for cerebellar connections. Conclusions: We failed to identify cerebellar functional connectivity–based contributions to ASD. However, we observed prospective correlates of ASD-associated behaviors in networks that support EBL. Future studies may replicate and extend network-level positive results, and tests of the cerebellum may investigate brain-behavior associations at different developmental stages and/or using different neuroimaging modalities

Amorphe Mischhalbleiter auf der Basis von Silizium fuer Tandemsolarzellen Zwischenbericht

SIGLETIB Hannover: FR2241+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Duennschichtsolarzellen auf der Basis von amorphem Silizium Schlussbericht

The conversion efficiency, and predominantly the stability with respect to light-induced degradation of amorphous silicon (a-Si:H) based solar cells can considerably be improved by the use of a tandem or triple junction structure. The variation of the optical band-gap of a-Si:H can easily be accomplished by the additional incorporation of germanium or carbon into the amporphous network. However, the density of defect states of such alloys, both at mid-gap and in the band-tails, is strongly enhanced, and thus their optoelectronic properties correspondingly deteriorate with respect to pure a-Si:H. a-Si:H, a-Ge:H and amorphous alloy semiconductors (a-SiGe:H, a-SiC:H) with band-gaps of 1.1...2.1 eV were deposited by various methods, and optimized for the application in pin solar cells. Beyond these accomplishments, pin solar cells were fabricated on a laboratory scale, interface phenomena which substantially influence the device performance were investigated, a description of metastability on thermodynamic grounds was given, and a novel macroscopic grooving of the substrate was tested within first attempts to enhance the stabilized conversion efficiency of amorphous solar cellsDer Wirkungsgrad und vor allem die Stabilitaet gegenueber lichtinduzierter Degradation von Solarzellen auf der Basis amorphen Siliziums (a-Si:H) laesst sich mit Mehrbarrierensystemen, die Absorber mit abgestuften Bandabstaenden verwenden, erheblich verbessern. Die Variation des optischen Bandabstandes von a-Si:H gelingt sehr einfach durch zusAetzlich Einbau von Germanium oder Kohlenstoff, allerdings weisen solche Legierungen erhoehte Zustandsdichten in der Mitte der Quasibandluecke sowie den Bandauslaeufern auf und zeigen entsprechend schlechtere optoelektronische Eigenschaften als amorphes Silizium selbst. a-Si:H, a-Ge:H und amorphe Mischhalbleiter (a-SiGe:H, a-SiC:H) mit Bandabstaenden von (1,1-2,1) eV wurden mit verschiedenen Verfahren hergestellt und fuer die Anwendung in pin-Solarzellen optimiert. Darueber hinaus wurden pin-Solarzellen hergestellt, Grenzflaechenphaenomene untersucht, die deren Wirkungsgrad massgeblich beeinflussen, eine thermodynamisch begruendete Beschreibung der Metastabilitaet der untersuchten Halbleiter gegeben und eine neuartige makroskopische Strukturierung zur Erhhung der stabilisierten Wirkungsgrade amorpher Solarzellen erprobtSIGLEAvailable from TIB Hannover: F94B1214+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Duennschichtsolarzellen: Einsatz des CVD-Verfahrens zur Herstellung von a-Si:H-Solarzellen Schlussbericht

SIGLETIB Hannover: FR 2242+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Laser spectroscopy of muonic deuterium

International audienceThe deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important benchmarks for understanding the nuclear forces and structure. Muonic deuterium μd is the exotic atom formed by a deuteron and a negative muon μ–. We measured three 2S-2P transitions in μd and obtain rd = Embedded Image fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value rd = Embedded Image fm. The μd value is also 3.5σ smaller than the rd value from electronic deuterium spectroscopy. The smaller rd, when combined with the electronic isotope shift, yields a “small” proton radius rp, similar to the one from muonic hydrogen, amplifying the proton radius puzzle