90 research outputs found
Konsequenzen einer groĂflĂ€chigen Umstellung auf ökologischen Landbau
Die aktuellen Schwierigkeiten im Agrarsektor haben ein bisher nicht dagewesenes Interesse an einer verstĂ€rkten Förderung des ökologischen Landbaus durch gezielte agrarpolitische MaĂnahmen geweckt. Es werden Zielvorstellungen von bis zu 20% biologisch wirtschaftender Betriebe geĂ€uĂert. Eine deutliche Zunahme dieser Betriebe ist aufgrund der weitgehend anerkannten und vielfach nachgewiesenen ökologischen VorzĂŒglichkeit der biologischen Landwirtschaft wĂŒnschenswert. Gleichzeitig stellt sich aber auch die Frage nach den ökonomischen und sozialen Konsequenzen einer weitgehenden Umstellung auf ökologischen Landbau.
In einer Reihe von Studien wurde versucht, die Wirkungen einer flĂ€chendeckenden Umstellung ganzer LĂ€nder (Olson et al., 19821), Langley et al., 1983, fĂŒr die USA; Bechmann et al., 1992, Zerger & Bossel, 1994, SeemĂŒller, 2000, fĂŒr Deutschland; Lampkin, 1994, fĂŒr GroĂbritannien; Alroe & Kristensen, 2001, fĂŒr DĂ€nemark) oder Regionen (Rist et al., 1989, fĂŒr den Kanton Zug; Braun, 1995, fĂŒr Baden-WĂŒrttemberg; Pommer & Rintelen, 1997, fĂŒr Bayern) bzw. einer teilweisen Umstellung (Lampkin, 1994: 10 % ökologischer Landbau in GroĂbritannien; Wynen, 1998: 10 bis 80 %in DĂ€nemark; Zander et al., 1999: in Brandenburg) abzuschĂ€tzen.
Die Ergebnisse der zitierten Untersuchungen sollen hier vergleichend dargestellt und daraus Handlungsbedarf hinsichtlich einer groĂflĂ€chigen Umstellung abgeleitet werden
Versuch der monetĂ€ren Bewertung ökologischer Leistungen des Biologischen Landbaus im Bereich Grund- und Trinkwasser am Beispiel des Einzugsgebietes der Fernwasserversorgung MĂŒhlviertel/OĂ
Die tatsĂ€chlichen oder potentiellen volkswirtschaftlichen (externen) Kosten durch Umweltbelastung der intensiven Landbewirtschaftung werden der Allgemeinheit aufgebĂŒrdet, anstatt als Preis- bzw. Kostenfaktor in das betriebliche Rechnungswesen einzugehen. U.a. in Hinblick auf eine Verringerung externer Kosten der Landwirtschaft infolge Grund- und Trinkwasserbelastung wird der Ăkologische Landbau als wirksame Alternative diskutiert. Eine Vielzahl wissenschaftlicher Untersuchungen belegt denn auch das hohe MaĂ an GrundwasservertrĂ€glichkeit des Biologischen Landbaus: So wiesen u. a. VEREIJKEN und WIJNANDS (1990),BRANDHUBER und HEGE (1992), MATTHEY (1992), SCHULTE (1996), BERG et al. (1997) sowie SCHLĂTER et al. (1997) deutlich niedrigere Nitratgehalte des Sickerwassers unter biologisch bewirtschafteten FlĂ€chen als unter konventionell oder integriert bewirtschafteten VergleichsflĂ€chen nach. Aufgrund der Verringerung der Nitrat- und Vermeidung der Pestizidbelastung von Grund- und Trinkwasser durch Biologischen Landbau ist daher zu prĂŒfen, in welchem AusmaĂ durch diese Bewirtschaftungsform externe Kosten eingespart werden können
Distributing entanglement and single photons through an intra-city, free-space quantum channel
We have distributed entangled photons directly through the atmosphere to a
receiver station 7.8 km away over the city of Vienna, Austria at night.
Detection of one photon from our entangled pairs constitutes a triggered single
photon source from the sender. With no direct time-stable connection, the two
stations found coincidence counts in the detection events by calculating the
cross-correlation of locally-recorded time stamps shared over a public internet
channel. For this experiment, our quantum channel was maintained for a total of
40 minutes during which time a coincidence lock found approximately 60000
coincident detection events. The polarization correlations in those events
yielded a Bell parameter, S=2.27/pm0.019, which violates the CHSH-Bell
inequality by 14 standard deviations. This result is promising for
entanglement-based free-space quantum communication in high-density urban
areas. It is also encouraging for optical quantum communication between ground
stations and satellites since the length of our free-space link exceeds the
atmospheric equivalent.Comment: 8 pages including 1 figure and 2 tables. The first two authors
contributed equally to this wor
Visible foliar injury and infrared imaging show that daylength affects short-term recovery after ozone stress in Trifolium subterraneum
Tropospheric ozone is a major air pollutant affecting plants worldwide. Plants in northern regions can display more ozone injury than plants at lower latitudes despite lower ozone levels. Larger ozone influx and shorter nights have been suggested as possible causes. However, the effects of the dim light present during northern summer nights have not been investigated. Young Trifolium subterraneum plants kept in environmentally controlled growth rooms under long day (10âh bright light, 14âh dim light) or short day (10âh bright light, 14âh darkness) conditions were exposed to 6âh of 70âppb ozone during daytime for three consecutive days. Leaves were visually inspected and imaged in vivo using thermal imaging before and after the daily exposure. In long-day-treated plants, visible foliar injury within 1 week after exposure was more severe. Multivariate statistical analyses showed that the leaves of ozone-exposed long-day-treated plants were also warmer with more homogeneous temperature distributions than exposed short day and control plants, suggesting reduced transpiration. Temperature disruptions were not restricted to areas displaying visible damage and occurred even in leaves with only slight visible injury. Ozone did not affect the leaf temperature of short-day-treated plants. As all factors influencing ozone influx were the same for long- and short-day-treated plants, only the dim nocturnal light could account for the different ozone sensitivities. Thus, the twilight summer nights at high latitudes may have a negative effect on repair and defence processes activated after ozone exposure, thereby enhancing sensitivity
Free-Space distribution of entanglement and single photons over 144 km
Quantum Entanglement is the essence of quantum physics and inspires
fundamental questions about the principles of nature. Moreover it is also the
basis for emerging technologies of quantum information processing such as
quantum cryptography, quantum teleportation and quantum computation. Bell's
discovery, that correlations measured on entangled quantum systems are at
variance with a local realistic picture led to a flurry of experiments
confirming the quantum predictions. However, it is still experimentally
undecided whether quantum entanglement can survive global distances, as
predicted by quantum theory. Here we report the violation of the
Clauser-Horne-Shimony-Holt (CHSH) inequality measured by two observers
separated by 144 km between the Canary Islands of La Palma and Tenerife via an
optical free-space link using the Optical Ground Station (OGS) of the European
Space Agency (ESA). Furthermore we used the entangled pairs to generate a
quantum cryptographic key under experimental conditions and constraints
characteristic for a Space-to-ground experiment. The distance in our experiment
exceeds all previous free-space experiments by more than one order of magnitude
and exploits the limit for ground-based free-space communication; significantly
longer distances can only be reached using air- or space-based platforms. The
range achieved thereby demonstrates the feasibility of quantum communication in
space, involving satellites or the International Space Station (ISS).Comment: 10 pages including 2 figures and 1 table, Corrected typo
Normalisation to Blood Activity Is Required for the Accurate Quantification of Na/I Symporter Ectopic Expression by SPECT/CT in Individual Subjects
The utilisation of the Na/I symporter (NIS) and associated radiotracers as a reporter system for imaging gene expression is now reaching the clinical setting in cancer gene therapy applications. However, a formal assessment of the methodology in terms of normalisation of the data still remains to be performed, particularly in the context of the assessment of activities in individual subjects in longitudinal studies. In this context, we administered to mice a recombinant, replication-incompetent adenovirus encoding rat NIS, or a human colorectal carcinoma cell line (HT29) encoding mouse NIS. We used 99mTc pertechnetate as a radiotracer for SPECT/CT imaging to determine the pattern of ectopic NIS expression in longitudinal kinetic studies. Some animals of the cohort were culled and NIS expression was measured by quantitative RT-PCR and immunohistochemistry. The radioactive content of some liver biopsies was also measured ex vivo. Our results show that in longitudinal studies involving datasets taken from individual mice, the presentation of non-normalised data (activity expressed as %ID/g or %ID/cc) leads to ânoisyâ, and sometimes incoherent, results. This variability is due to the fact that the blood pertechnetate concentration can vary up to three-fold from day to day. Normalisation of these data with blood activities corrects for these inconsistencies. We advocate that, blood pertechnetate activity should be determined and used to normalise the activity measured in the organ/region of interest that expresses NIS ectopically. Considering that NIS imaging has already reached the clinical setting in the context of cancer gene therapy, this normalisation may be essential in order to obtain accurate and predictive information in future longitudinal clinical studies in biotherapy
Are Standards and Regulations of Organic Farming Moving Away from Small Farmers' Knowledge?
Tradition, Dynamics and Sustainability of Plant Species Composition and Management in Homegardens on Organic and Non-Organic Small Scale Farms in Alpine Eastern Tyrol, Austria
Technische Zusammenfassung
Die Technische Zusammenfassung des APCC-Sonderberichts âłLandnutzung und Klimawandel in Ăsterreichâł umfasst die Kernbotschaften der Kapitel 1â9. In ihr sind die Hauptaussagen zu den sozioökonomischen und klimatischen Treibern der LandnutzungsĂ€nderungen, zu den Auswirkungen von Landnutzung und -bewirtschaftung auf den Klimawandel, zu Minderungs- und Anpassungsoptionen im Kontext nachhaltiger Entwicklungsziele sowie zu Synergien, Zielkonflikten und Umsetzungsbarrieren von KlimamaĂnahmen enthalten
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