1,865 research outputs found

    Gr√ľne Gentechnik und √∂kologische Landwirtschaft

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    Weltweit findet sich als Rechtsnorm in allen entsprechenden Verbraucherschutzgesetzen die Vorgabe, in der √∂kologischen Landwirtschaft keine gentechnisch ver√§nderten Organismen einzusetzen. Auf europ√§ischer Ebene enthalten weder die EU-√Ėko-Verordnung noch die Saatgutverkehrsrichtlinien Regelungen, aufgrund derer Schutzma√ünahmen zur Verhinderung oder Vermeidung von GVO-Einkreuzungen in √∂kologische Kulturen vorgeschrieben werden k√∂nnen. Eine Pr√ľfung der neuen Freisetzungsrichtlinie ergibt aber, dass bei der Genehmigung zum Inverkehrbringen als ‚Äěbesondere Bedingungen f√ľr die Verwendung und Handhabung‚Äú eines GVO auch Ma√ünahmen zum Schutz vor Sachsch√§den durch GVO-Einkreuzung vorgeschrieben werden k√∂nnen. Als Ma√ünahmen zum Schutz vor Sachsch√§den werden haupts√§chlich Sicherheitsabst√§nde zwischen Feldern mit GVO-Pflanzen und √∂kologisch bewirtschafteten Kulturen sowie zus√§tzlich gentechnikfreie Gebiete diskutiert. Bei der Analyse der Datenlage zur Definition von Sicherheitsabst√§nden treten viele L√ľcken in der empirischen Datenbasis zu Tage, sodass sich hier dringender Forschungsbedarf abzeichnet. Es werden pragmatisch Hinweise zu Sicherheitsabst√§nden abgeleitet. Gentechnikfreie Gebiete resp. geschlossene Anbaugebiete werden in Zusammenhang mit der Saatgutproduktion vorgeschlagen. Bisher erm√∂glicht nur das Zivilrecht in Deutschland einen privaten Ausgleich der Rechts- und Interessensph√§ren der Bio-Bauern und der Nutzer transgener Sorten. ¬ß 906 BGB l√§sst sich hier als zentrale Steuerungsnorm des Umweltprivatrechts heranziehen. Dessen System von Unterlassungs- und Ausgleichsanspr√ľchen ist hochkomplex und wird nur schwer zu einer zufriedenstellenden Koexistenz beitragen k√∂nnen. Eine L√∂sung w√§re daher eine wirksame Selbstorganisation des Wirtschaftszweigs der Saatgutindustrie, die transgene Pflanzen z√ľchtet und das Saatgut in Verkehr bringt. Sollte diese nicht m√∂glich sein, bietet sich eine √∂ffentlich-rechtliche Regelung an. Dazu k√∂nnten geh√∂ren: Die Einrichtung eines Anbaukatasters, die Einf√ľhrung einer guten fachlichen Praxis des GVO-Anbaus (GfP), die Festlegung einer Instruktionspflicht auf der Saatgutverpackung sowie der Schutz der √∂kologischen Saatgutproduktion

    Zero bias anomalies in point-contact characteristics of αt-(BEDT-TTF)2I3

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    The zero-bias anomaly in point-contact characteristics of the organic superconductor α-(BEDT-TTF)2I3 is investigated as a function of temperature and magnetic field. It is found that the zero-bias anomaly is insensitive to magnetic fields up to 5 T. In contrast, a structure at 5 meV, conventionally designated as the superconducting gap - but which is 4 times larger than the expected BCS gap - is strongly affected by magnetic fields above 1 T

    Determination of the electron phonon coupling and the superconducting gap in β-(BEDT-TTF)2X crystals (X=I3, IAuI)

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    We performed point-contact and tunneling measurements on the organic superconductors beta-(BEDT-TTF)2I3 and beta-(BEDT-TTF)2IAuI, in the normal and superconducting states. The point-contact measurement in the normal state provides the Eliashberg function alpha2(omega)F (omega). This function has maxima at 4 and 15 mV, as well as a sharp peak at 1 mV which seems to indicate a very soft phonon strongly coupled to the electrons. The measurements in the superconducting state provide the superconducting gap, which for the tunneling measurements has a value 2Delta/kB Tc=4, just slightly above the BCS value

    Band structure calculation and tunneling measurements in (BEDT-TTF)2X (X=I3, IAuI)

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    At about the same time when little proposed room-temperature superconductivity in organic polymers, it was suggested that the high-Tc of the more conventional A-15's is associated with their one-dimensional electronic band structure. When TTF-TCNQ was discovered in 1973, it was suggested that the electron-phonon coupling in this 1-D organic molecular crystal is responsible for the metal-to-insulator (Peierls) transition at 52 K2, and reducing λ will cause a crossover to a superconducting state. Since then, the electronic structure, the conduction mechanism, and the superconducting mechanism were subject to controversy. Therefore, it is of some importance to establish whether the electronic band structure, and conduction mechanism, are similar to those in more conventional metals, and whether the superconductivity mechanism is the normal BCS phonon-mediated interaction

    Nanoscale spin rectifiers controlled by the Stark effect

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    The control of orbital and spin state of single electrons is a key ingredient for quantum information processing, novel detection schemes, and, more generally, is of much relevance for spintronics. Coulomb and spin blockade (SB) in double quantum dots (DQDs) enable advanced single-spin operations that would be available even for room-temperature applications for sufficiently small devices. To date, however, spin operations in DQDs were observed at sub-Kelvin temperatures, a key reason being that scaling a DQD system while retaining an independent field-effect control on the individual dots is very challenging. Here we show that quantum-confined Stark effect allows an independent addressing of two dots only 5 nm apart with no need for aligned nanometer-size local gating. We thus demonstrate a scalable method to fully control a DQD device, regardless of its physical size. In the present implementation we show InAs/InP nanowire (NW) DQDs that display an experimentally detectable SB up to 10 K. We also report and discuss an unexpected re-entrant SB lifting as a function magnetic-field intensity

    Search for supersymmetry in events with b-quark jets and missing transverse energy in pp collisions at 7 TeV

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    Results are presented from a search for physics beyond the standard model based on events with large missing transverse energy, at least three jets, and at least one, two, or three b-quark jets. The study is performed using a sample of proton-proton collision data collected at sqrt(s) = 7 TeV with the CMS detector at the LHC in 2011. The integrated luminosity of the sample is 4.98 inverse femtobarns. The observed number of events is found to be consistent with the standard model expectation, which is evaluated using control samples in the data. The results are used to constrain cross sections for the production of supersymmetric particles decaying to b-quark-enriched final states in the context of simplified model spectra.Comment: Submitted to Physical Review

    The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI

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    The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.Comment: Published in the ESO Messenge
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