Potential Energy Surface for H_2 Dissociation over Pd(100)

The potential energy surface (PES) of dissociative adsorption of H_2 on Pd(100) is investigated using density functional theory and the full-potential linear augmented plane wave (FP-LAPW) method. Several dissociation pathways are identified which have a vanishing energy barrier. A pronounced dependence of the potential energy on ``cartwheel'' rotations of the molecular axis is found. The calculated PES shows no indication of the presence of a precursor state in front of the surface. Both results indicate that steering effects determine the observed decrease of the sticking coefficient at low energies of the H_2 molecules. We show that the topology of the PES is related to the dependence of the covalent H(s)-Pd(d) interactions on the orientation of the H_2 molecule.Comment: RevTeX, 8 pages, 5 figures in uufiles forma

High-Flux Femtosecond X-Ray Emission from Controlled Generation of Annular Electron Beams in a Laser Wakefield Accelerator

Annular quasimonoenergetic electron beams with a mean energy in the range 200-400 MeV and charge on the order of several picocoulombs were generated in a laser wakefield accelerator and subsequently accelerated using a plasma afterburner in a two-stage gas cell. Generation of these beams is associated with injection occurring on the density down ramp between the stages. This well-localized injection produces a bunch of electrons performing coherent betatron oscillations in the wakefield, resulting in a significant increase in the x-ray yield. Annular electron distributions are detected in 40% of shots under optimal conditions. Simultaneous control of the pulse duration and frequency chirp enables optimization of both the energy and the energy spread of the annular beam and boosts the radiant energy per unit charge by almost an order of magnitude. These well-defined annular distributions of electrons are a promising source of high-brightness laser plasma-based x rays

Safe Design Suggestions for Vegetated Roofs

Rooftop vegetation is becoming increasingly popular because of its environmental benefits and its ability to earn green-building certification credits. With the exception of one international guideline, there is little mention of worker safety and health in vegetated-roof codes and literature. Observations and field investigations of 19 vegetated roofs in the United States revealed unsafe access for workers and equipment, a lack of fall-protection measures, and other site-specific hazards. Design for safety strategies and the integration of life-cycle safety thinking with green-building credits systems are the preferred methods to reduce risk to workers on vegetated roofs. Design suggestions have been developed to add to the body of knowledge. The findings complement several National Institute for Occupational Safety and Health (NIOSH) construction and prevention through design (PtD) goals and are congruent with NIOSH’s Safe Green Jobs initiative. Organizations that install and maintain vegetated roofs can utilize the findings to understand hazards, take precautions, and incorporate safety into their bids The published version of this article is available here: 10.1061/(ASCE)CO.1943-7862.0000500Support from the the Virginia Tech Occupational Safety and Health Research Center through the Kevin P. Granata Pilot Program funded by the Institute for Critical Technology and Applied Sciences

A novel class of microRNA-recognition elements that function only within open reading frames.

MicroRNAs (miRNAs) are well known to target 3' untranslated regions (3' UTRs) in mRNAs, thereby silencing gene expression at the post-transcriptional level. Multiple reports have also indicated the ability of miRNAs to target protein-coding sequences (CDS); however, miRNAs have been generally believed to function through similar mechanisms regardless of the locations of their sites of action. Here, we report a class of miRNA-recognition elements (MREs) that function exclusively in CDS regions. Through functional and mechanistic characterization of these 'unusual' MREs, we demonstrate that CDS-targeted miRNAs require extensive base-pairing at the 3' side rather than the 5' seed; cause gene silencing in an Argonaute-dependent but GW182-independent manner; and repress translation by inducing transient ribosome stalling instead of mRNA destabilization. These findings reveal distinct mechanisms and functional consequences of miRNAs that target CDS versus the 3' UTR and suggest that CDS-targeted miRNAs may use a translational quality-control-related mechanism to regulate translation in mammalian cells

Das Institut für Bildungsforschung in der Ära Hellmut Becker, 1958 – 1981: Zur Genese und Transformation einer interdisziplinären Sozialwissenschaft im Kontext der Max-Planck-Gesellschaft

Mit der Gründung des Instituts für Bildungsforschung begann 1963 in West-Berlin die Geschichte der Sozialwissenschaften in der Max-Planck-Gesellschaft (MPG). 1958 hatte Hellmut Becker der MPG die Einrichtung des später so genannten Max-Planck-Instituts für Bildungsforschung (MPIB) informell vorgeschlagen, 1981 wurde er als Direktor des MPIB emeritiert. Rekonstruiert wird im vorliegenden Preprint die Institutsgeschichte der Ära Becker und des damals entworfenen Typus‘ einer interdisziplinären Sozialwissenschaft im Kontext der Geschichte der MPG: der Debatten um die Gründung und Entwicklung des Instituts, der Führungszirkel und der Governancestruktur der Forschungsgesellschaft. Kontur gewinnt die Institutsgeschichte unter Becker besonders über ihren engen Zusammenhang mit dem 1970 unter Leitung Carl Friedrich von Weizsäckers in Starnberg eröffneten Max-Planck-Institut zur Erforschung der Lebensbedingungen der wissenschaftlich-technischen Welt. Leitend ist die These eines an beiden Instituten strukturähnlich verfolgten ‚Doppelansatzes‘, gerichtet auf die komplementäre Bearbeitung der Herausforderungen einer wissenschaftlich-technisch bestimmten Welt, der in der MPG temporär einen Ort erhielt. Näher untersucht wird im Preprint die Genese der Konzeption der Bildungsforschung und wie es zwischen 1958 und 1963 überhaupt gelang, den interdisziplinären, explizit politikorientierten Ansatz in der Gesellschaft der Grundlagenforschung zu etablieren. Wie gezeigt wird, war dabei die Protektion von Führungspersonen in der MPG, Wirtschaftsvertretern im Verwaltungsrat und besonders Präsident Adolf Butenandt, maßgeblich. Verfolgt wird, wie sich die Bildungsforschung in engster Verflechtung mit zeitgenössischen bildungs-/politischen Entwicklungen, wie der Arbeit des Deutschen Bildungsrats und der „Studentenbewegung“, praktisch entfaltete und zunehmend in ein links-liberales politisches Spektrum schob. Schließlich wird die in den 70er Jahren beobachtbare Transformation der am Institut betriebenen Bildungsforschung in Richtung auf eine redisziplinierte empirische Sozialforschung rekonstruiert, die als entpolitisiert/nicht-ideologisch und leistungsstark ausgeflaggt war. Treiber dieser Transformation war eine massive Kritik am MPIB und der dortigen Bildungsforschung (wie an Starnberger Ansätzen) durch Vertreter*innen aus Politik, Wirtschaft und Wissenschaft und ebenso durch den seit 1972 amtierenden Präsidenten der MPG, Reimar Lüst, unter dem die Transformation über ein stärker zentralisiertes, neues Management-Regime der MPG umgesetzt und forciert wurde. Als Becker 1981 emeritiert wurde und im gleichen Jahr der Beschluss zur Schließung des Starnberger Instituts erfolgte, gelangte die erste Phase eines spezifischen, politisch orientierten Typus‘ von Sozialforschung in der MPG an ihr Ende. Auch da die Kritik an der Bildungsforschung und an Starnberger Ansätzen im Preprint in weiten Teilen als Aspekt einer konservativen „Tendenzwende“ gedeutet wird, die sich in Westdeutschland seit Ende der 1960er Jahre vielschichtig zu formieren begann, wird die hier vorgestellte Wissenschaftsgeschichte als integraler Bestandteil der bildungs-/politischen, sozialen und wirtschaftlichen Entwicklungen der Bundesrepublik entworfen

Interaction of the ionic liquid [BMP][TFSA] with rutile TiO2(110) and coadsorbed lithium

Aiming at a fundamental understanding of the processes at the electrode|ionic liquid interface in Li ion batteries, we investigated the interaction of the ionic liquid n-butyl-n-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSA] and of Li with a reduced rutile TiO2(110) (1 × 1) surface as well as the interaction between [BMP][TFSA] and Li on the TiO2(110) surface under ultrahigh vacuum (UHV) conditions by X-ray photoelectron spectroscopy and scanning tunnelling microscopy. Between 80 K and 340 K [BMP][TFSA] adsorbs molecularly on the surface and at higher temperatures decomposition is observed, resulting in products such as Sad, Fad and TiNx. The decomposition pattern is compared to proposals based on theory. Small amounts of Li intercalate even at 80 K into TiO2(110), forming Li+ and Ti3+ species. The stoichiometry in the near surface region corresponds to Li7Ti5O12. For higher coverages in the range of several monolayers part of the Li remains on the surface, forming a Li2O cover layer. At 300 K, Ti3+ species become sufficiently mobile to diffuse into the bulk. Li post-deposition on a [BMP][TFSA] covered TiO2(110) surface at 80 K results in two competing reactions, Li intercalation and reaction with the IL, resulting in the decomposition of the IL. Upon warming up, the Ti3+ formed at low T is consumed by reaction with the IL adlayer and intermediate decomposition products. Post-deposition of [BMP][TFSA] (300 K) on a surface pre-covered with a Li2O/Li7Ti5O12 layer results in the partial reaction of [BMP][TFSA] with the Li+ and Ti3+ species, which gets completed at higher temperatures

Echinacea purpurea Significantly Induces Cytochrome P450 3A Activity but Does Not Alter Lopinavir‐Ritonavir Exposure in Healthy Subjects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90291/1/phco.30.8.797.pd

Mammalian microRNAs predominantly act to decrease target mRNA levels

MicroRNAs (miRNAs) are endogenous ~22-nucleotide RNAs that mediate important gene-regulatory events by pairing to the mRNAs of protein-coding genes to direct their repression. Repression of these regulatory targets leads to decreased translational efficiency and/or decreased mRNA levels, but the relative contributions of these two outcomes have been largely unknown, particularly for endogenous targets expressed at low-to-moderate levels. Here, we use ribosome profiling to measure the overall effects on protein production and compare these to simultaneously measured effects on mRNA levels. For both ectopic and endogenous miRNA regulatory interactions, lowered mRNA levels account for most (≥84%) of the decreased protein production. These results show that changes in mRNA levels closely reflect the impact of miRNAs on gene expression and indicate that destabilization of target mRNAs is the predominant reason for reduced protein output.National Institutes of Health (U.S.