3,227 research outputs found
Commentary on Court of Justice of the European Union judgments C-434/15 Of 20 December 2017 (Asociacion Profesional Elite Taxi v Uber Systems Spain SL) and C-320/16 of 10 April 2018 (Uber France SAS)
Facile and Sustainable Synthesis of Erythritol bis(carbonate), a Valuable Monomer for Non-Isocyanate Polyurethanes (NIPUs)
Defect healing at room temperature in pentacene thin films and improved transistor performance
We report on a healing of defects at room temperature in the organic
semiconductor pentacene. This peculiar effect is a direct consequence of the
weak intermolecular interaction which is characteristic of organic
semiconductors. Pentacene thin-film transistors were fabricated and
characterized by in situ gated four-terminal measurements. Under high vacuum
conditions (base pressure of order 10E-8 mbar), the device performance is found
to improve with time. The effective field-effect mobility increases by as much
as a factor of two and mobilities up to 0.45 cm2/Vs were achieved. In addition,
the contact resistance decreases by more than an order of magnitude and there
is a significant reduction in current hysteresis. Oxygen/nitrogen exposure and
annealing experiments show the improvement of the electronic parameters to be
driven by a thermally promoted process and not by chemical doping. In order to
extract the spectral density of trap states from the transistor
characteristics, we have implemented a powerful scheme which allows for a
calculation of the trap densities with high accuracy in a straightforward
fashion. We show the performance improvement to be due to a reduction in the
density of shallow traps <0.15 eV from the valence band edge, while the
energetically deeper traps are essentially unaffected. This work contributes to
an understanding of the shallow traps in organic semiconductors and identifies
structural point defects within the grains of the polycrystalline thin films as
a major cause.Comment: 13 pages, 13 figures, to be published in Phys. Rev.
Commentaire des arrêts de la Cour de justice de l'Union européenne c-434/15 du 20 décembre 2017 (Asociacion Profesional Elite Taxi contre Uber Systems Spain sl) et c 320/16 du 10 avril 2018 (Uber France sas)
Dans ses deux arrêts sur l'activité de l'entreprise Uber en Espagne et en France, la CJUE a qualifié l'activité de l'entreprise de service de transport, soumis au régime général de la Directive relative aux services dans le marché intérieur et faisant l'objet d'une compétence partagée entre les Etats membres et l'Union. Les Etats membres sont donc autorisés à réglementer cette activité en la soumettant à autorisation, voire en l'interdisant. L'analyse fonctionnelle de l'activité d'Uber effectuée par la CJUE devrait à notre avis nourrir le raisonnement des tribunaux nationaux qui seront appelés à se pencher sur la question, cruciale en droit social, de la nature des rapports juridiques entre Uber et ses chauffeurs (contrat de travail ou partenariat avec des indépendants)
Observation and uses of position-space Bloch oscillations in an ultracold gas
We report the direct observation and characterization of position-space Bloch
oscillations using an ultracold gas in a tilted optical lattice. While Bloch
oscillations in momentum space are a common feature of optical lattice
experiments, the real-space center-of-mass dynamics are typically too small to
resolve. Tuning into the regime of rapid tunneling and weak force, we observe
real-space Bloch oscillation amplitudes of hundreds of lattice sites, in both
ground and excited bands. We demonstrate two unique capabilities enabled by
tracking of Bloch dynamics in position space: measurement of the full
position-momentum phase-space evolution during a Bloch cycle, and direct
imaging of the lattice band structure. These techniques, along with the ability
to exert long-distance coherent control of quantum gases without modulation,
may open up new possibilities for quantum control and metrology.Comment: 5 pages, 6 figure
Herpes Simplex Virus 1 Coinfection Modifies Adeno-associated Virus Genome End Recombination
Wild-type adeno-associated virus (AAV) can only replicate in the presence of helper factors, which can be provided by coinfecting helper viruses such as adenoviruses and herpesviruses. The AAV genome consists of a linear, single-stranded DNA (ssDNA), which is converted into different molecular structures within the host cell. Using high-throughput sequencing, we found that herpes simplex virus 1 (HSV-1) coinfection leads to a shift in the type of AAV genome end recombination. In particular, open-end inverted terminal repeat (ITR) recombination was enhanced, whereas open-closed ITR recombination was reduced in the presence of HSV-1. We demonstrate that the HSV-1 protein ICP8 plays an essential role in HSV-1-mediated interference with AAV genome end recombination, indicating that the previously described ICP8-driven mechanism of HSV-1 genome recombination may be underlying the observed changes. We also provide evidence that additional factors, such as products of true late genes, are involved. Although HSV-1 coinfection significantly changed the type of AAV genome end recombination, no significant change in the amount of circular AAV genomes was identified
Direct Catalytic Route to Biomass-Derived 2,5-Furandicarboxylic Acid and Its Use as Monomer in a Multicomponent Polymerization
Efficient synthesis of valuable platform chemicals from renewable feedstock is a challenging, yet essential strategy for developing technologies that are both economical and sustainable. In the present study, we investigated the synthesis of 2,5-furandicarboxylic acid (FDCA) in a two-step catalytic process starting from sucrose as largely available biomass feedstock. In the first step, 5-(hydroxymethyl)furfural (HMF) was synthesized by hydrolysis and dehydration of sucrose using sulfuric acid in a continuous reactor in 34% yield. In a second step, the resulting reaction solution was directly oxidized to FDCA without further purification over a Au/ZrO catalyst with 84% yield (87% selectivity, batch process), corresponding to 29% overall yield with respect to sucrose. This two-step process could afford the production of pure FDCA after the respective extraction/crystallization despite the impure intermediate HMF solution. To demonstrate the direct application of the biomass-derived FDCA as monomer, the isolated product was used for Ugi-multicomponent polymerizations, establishing a new application possibility for FDCA. In the future, this efficient two-step process strategy toward FDCA should be extended to further renewable feedstock
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