262 research outputs found
Sortenversuche 2002 im ökologischen Landbau in Deutschland: Sommerweizen - Bundesweite Auswertung der Ergebnisse der Arbeitsgruppe Ăkologischer Versuchsansteller
Deutschlandweite Auswertung der Sortenversuche Sommerweizen
Tabellen:
Standortdaten
ErtrÀge [relativ]
hl-Gewicht [relativ
Sortenversuche 2002 im ökologischen Landbau in Deutschland: Hafer - Bundesweite Auswertung der Ergebnisse der Arbeitsgruppe Ăkologischer Versuchsansteller
Die vorliegende deutschlandweite Auswertung der Sortenversuche "Hafer" beruht auf den Versuchen der in der Arbeitsgruppe Ăkologischer Versuchsansteller des Verbands der Landwirtschaftskammern e.V. (VLK) vertretenen Einrichtungen (Landwirtschaftskammern und Versuchsanstalten der BundeslĂ€nder).
Tabellen:
Standortdaten
ErtrÀge [relativ]
hl-Gewicht [relativ
The rationale for a spine registry
In the discussion about the rationale for spine registries, two basic questions have to be answered. The first one deals with the value of orthopaedic registries per se, considering them as observational studies and comparing the evidence they generate with that of randomised controlled trials. The second question asks if the need for registries in spine surgery is similar to that in the arthroplasty sector. The widely held view that randomised controlled trials are the âgold standard' for evaluation and that observational methods have little or no value ignores the limitations of randomised trials. They may prove unnecessary, inappropriate, impossible, or inadequate. In addition, the external validity and hence the ability to make generalisations about the results of randomised trials is often low. Therefore, the false conflict between those who advocate randomised trials in all situations and those who believe observational data provide sufficient evidence needs to be replaced with mutual recognition of their complementary roles. The fact that many surgical techniques or technologies were introduced into the field of spine surgery without randomised trials or prospective cohort comparisons makes obvious an even increased need for spine registries compared to joint arthroplasty. An essential methodological prerequisite for a registry is a common terminology for reporting results and a sophisticated technology that networks all participants so that one central data pool is created and accessed. Recognising this need, the Spine Society of Europe has researched and developed Spine Tango, the first European spine registry, which can be accessed under www.eurospine.or
The rationale for a spine registry
In the discussion about the rationale for spine registries, two basic questions have to be answered. The first one deals with the value of orthopaedic registries per se, considering them as observational studies and comparing the evidence they generate with that of randomised controlled trials. The second question asks if the need for registries in spine surgery is similar to that in the arthroplasty sector. The widely held view that randomised controlled trials are the 'gold standard' for evaluation and that observational methods have little or no value ignores the limitations of randomised trials. They may prove unnecessary, inappropriate, impossible, or inadequate. In addition, the external validity and hence the ability to make generalisations about the results of randomised trials is often low. Therefore, the false conflict between those who advocate randomised trials in all situations and those who believe observational data provide sufficient evidence needs to be replaced with mutual recognition of their complementary roles. The fact that many surgical techniques or technologies were introduced into the field of spine surgery without randomised trials or prospective cohort comparisons makes obvious an even increased need for spine registries compared to joint arthroplasty. An essential methodological prerequisite for a registry is a common terminology for reporting results and a sophisticated technology that networks all participants so that one central data pool is created and accessed. Recognising this need, the Spine Society of Europe has researched and developed Spine Tango, the first European spine registry, which can be accessed under www.eurospine.org
Unveiling the interaction of reactions and phase transition during thermal abuse of Li-ion batteries
Safety considerations have always accompanied the development of new battery chemistries; this holds especially for the Li-ion battery with its highly reactive components. An overall assessment and decrease of risks of catastrophic failures such as during thermal runaway, requires an in-depth and quantitative understanding of the ongoing processes and their interaction. This can be provided by predictive mathematical models. Thus, we developed a thermal runaway model that focuses on rigorous modelling of thermodynamic properties and reactions of each component within a Li-ion battery. Moreover, the presented model considers vapourâliquid equilibria of a binary solvent mixture for the first time. Simulations show a fragile equilibrium between endothermic and exothermic reactions, such as LiPF and LEDC decomposition, in the early phases of self-heating. Further, an autocatalytic cycle involving the production of HF and the SEI component LiCO could be revealed. Additionally, the unpredictability of the thermal runaway could be directly correlated to availability of LEDC or contaminants such as water. Also, solvent boiling can have a significant influence on the self-heating phase of a Li-ion battery, due to its endothermic nature. Further analysis revealed that the rising pressure, stemming from gassing reactions, can suppress solvent boiling until the thermal runaway occurs
Phonons from neutron powder diffraction
The spherically averaged structure function \soq obtained from pulsed
neutron powder diffraction contains both elastic and inelastic scattering via
an integral over energy. The Fourier transformation of \soq to real space, as
is done in the pair density function (PDF) analysis, regularizes the data, i.e.
it accentuates the diffuse scattering. We present a technique which enables the
extraction of off-center phonon information from powder diffraction experiments
by comparing the experimental PDF with theoretical calculations based on
standard interatomic potentials and the crystal symmetry. This procedure
(dynamics from powder diffraction(DPD)) has been successfully implemented for
two systems, a simple metal, fcc Ni, and an ionic crystal, CaF. Although
computationally intensive, this data analysis allows for a phonon based
modeling of the PDF, and additionally provides off-center phonon information
from powder neutron diffraction
Exact diagonalization study of the two-dimensional t-J-Holstein model
We study by exact diagonalization the two-dimensional t-J-Holstein model near
quarter filling by retaining only few phonon modes in momentum space. This
truncation allows us to incorporate the full dynamics of the retained phonon
modes. The behavior of the kinetic energy, the charge structure factor and
other physical quantities, show the presence of a transition from a delocalized
phase to a localized phase at a finite value of the electron-phonon coupling.
We have also given some indications that the e-ph coupling leads in general to
a suppression of the pairing susceptibility at quarter filling.Comment: 11 pages, Revtex v. 2.0, 4 figures available from author
Auswirkungen der Landwirtschaft auf physikalische und chemische Funktionen EuropÀischer Torfböden
Torfböden bieten zahlreiche Funktionen: sie bilden den weltweit gröĂten terrestrischen Kohlenstoffspeicher, stellen wichtige NĂ€hrstofffilter dar und erhöhen hydrologische PufferkapazitĂ€ten. Torfböden sind in Mittel- und Nordeuropa zum ĂŒberwiegenden Teil landwirtschaftlich genutzt. Kultivierung fĂŒhrt zu extremen Mineralisierungsraten der organischen Substanz und hohen THG-Emissionen. Die AnfĂ€lligigkeit fĂŒr Bodensackung, Boden- und WasserqualitĂ€tsverschlechterung und folglich Ernteausfall steigt. Das Ziel dieser Studie ist es, Auswirkungen des Agrarmanagements auf Funktionen von Torfböden in Europa zu analysieren. In Deutschland, den Niederlanden, DĂ€nemark, Estland, Finnland und Schweden wurden standardisierte Bodenkartierungen, bodenphysikalische und -chemische Analysen, Grundwassermonitoring und Betriebsdatenerhebungen durchgefĂŒhrt. Die Ergebnisse belegen einen starken Einfluss der bisherigen Bewirtschaftung auf die Funktionen von Torfböden in Europa. Torfböden unter intensiver Ackernutzung bieten im Vergleich zu extensiver und intensiver GrĂŒnlandnutzung die niedrigste TragfĂ€higkeit in den oberen 10 cm, welche eine erfolgreiche landwirtschaftliche Praxis auf Torfböden stark einschrĂ€nkt. Der Unterschied lĂ€sst sich allein durch Wurzelstabilisierung erklĂ€ren, da die Bodenverdichtung in den oberen 25cm unter Ackernutzung am höchsten ist. Hieraus folgt eine starke Verringerung der nutzbaren FeldkapazitĂ€t und der gesĂ€ttigten hydraulischen LeitfĂ€higkeit, wodurch sich hydrologische Probleme wie StaunĂ€sse und Trockenstress, die hĂ€ufig auf kultivierten Torfböden vorkommen, weiter intensivieren. BodenkohlenstoffvorrĂ€te sinken deutlich mit steigender NutzungsintensitĂ€t und sind im Vergleich auf extensivem GrĂŒnland am höchsten. Dies wird bestĂ€tigt durch den Zersetzungsgrad, der hier am niedrigsten ist. Die Ergebnisse deuten auf eine starke Auswirkung des Managements auf Bodenkohlenstoffverluste und Torfkonservierung auf europĂ€ischer Ebene hin
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