1,650 research outputs found
Forward pi^0-meson production at HERA
The production of high transverse momentum piz^0-mesons has been measured in
deep-inelastic e-p scattering events at low Bjorken- taken with the
H1 detector at HERA. The production of high p_T particles is strongly
correlated to the emission of hard partons in QCD and is therefore sensitive to
the dynamics of the strong interaction. For the first time the measurement of
single particles has been extended to the region of small angles w.r.t. the
proton remnant (forward region) and down to very low values of x ~ 5x10^-5.
This region is expected to be particularly sensitive to QCD evolution effects
in final states. Differential cross sections of inclusive pi^0-meson production
have been measured as a function of Bjorken-x and the four-momentum transfer
Q^2, and also as a function of the transverse momentum and the polar angle of
the pi^0-mesons. A recent BFKL calculation and QCD models based on the DGLAP
splitting functions are compared to the data. The best description of the data
is achieved by the BFKL calculation.Comment: 3 pages, 2 figures, talk given on behalf of the H1 collaboration at
DIS99, Zeuthe
Ackerwildkrautschutz in Luxemburg durch Schutzäcker, Feldflorareservate und Ökologische Landwirtschaft
Arable plants are becoming increasingly rare in today's cultural landscape and belong to the most endangered plant species in Luxemburg. Their main threat is the intensification of agriculture, where high usage of pesticides and fertilizer, better seed cleaning methods and the abandonment of marginal yield sites all negatively affect arable plant communities. Another factor is the loss of (potential) habitat due to the expansion of settlements and subsequent loss of agricultural lands. The dire situation calls for urgent action. Within the framework of the bachelor thesis of the first author, a concept for the protection of arable plants in Luxembourg was developed. The
following article describes and discusses the four most promising applied approaches to arable plant conservation identified in the course of this work, namely organic
farming, two types of “conservation fields” (“Schutzacker” and “Feldflorareservat”) and pesticide-free field margins
Report on comparative results of tested water saving techniques, with respect to mainly physical factors at local and regional level, including ranking of techniques for a range of environmental conditions
The effect of crop residues, cover crops, manures and nitrogen fertilization on soil organic carbon changes in agroecosystems: a synthesis of reviews
International initiatives are emphasizing the capture of atmospheric CO2 in soil organic C (SOC) to reduce the climatic footprint from agroecosystems. One approach to quantify the contribution of management practices towards that goal is through analysis of long-term experiments (LTEs). Our objectives were to analyze knowledge gained in literature reviews on SOC changes in LTEs, to evaluate the results regarding interactions with pedo-climatological factors, and to discuss disparities among reviews in data selection criteria. We summarized mean response ratios (RRs) and stock change rate (SCR) effect size indices from twenty reviews using paired comparisons (N). The highest RRs were found with manure applications (30%, N = 418), followed by aboveground crop residue retention and the use of cover crops (9–10%, N = 995 and 129), while the effect of nitrogen fertilization was lowest (6%, N = 846). SCR for nitrogen fertilization exceeded that for aboveground crop residue retention (233 versus 117 kg C ha−1 year−1, N = 183 and 279) and was highest for manure applications and cover crops (409 and 331 kg C ha−1 year−1, N = 217 and 176). When data allows, we recommend calculating both RR and SCR because it improves the interpretation. Our synthesis shows that results are not always consistent among reviews and that interaction with texture and climate remain inconclusive. Selection criteria for study durations are highly variable, resulting in irregular conclusions for the effect of time on changes in SOC. We also discuss the relationships of SOC changes with yield and cropping systems, as well as conceptual problems when scaling-up results obtained from field studies to regional levels
Karlstadter Positionspapier zum Schutz der Ackerwildkräuter. Erarbeitet von den Teilnehmerinnen und Teilnehmern der "Tagung zum Schutz der Ackerwildflora" am 25./26.6.2004 in Karlstadt am Main
Der Erhalt von Ackerwildkräutern, die historisch erst mit der Landbewirtschaftung in Mitteleuropa heimisch geworden sind, ist eine Kulturaufgabe, damit auch künftige Generationen die Arten- und Farbenvielfalt in der Kulturlandschaft erleben können
Carbenoxolone induced depression of rhythmogenesis in the pre-Bötzinger Complex
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Precondition Inference via Partitioning of Initial States
Precondition inference is a non-trivial task with several applications in
program analysis and verification. We present a novel iterative method for
automatically deriving sufficient preconditions for safety and unsafety of
programs which introduces a new dimension of modularity. Each iteration
maintains over-approximations of the set of \emph{safe} and \emph{unsafe}
\emph{initial} states. Then we repeatedly use the current abstractions to
partition the program's \emph{initial} states into those known to be safe,
known to be unsafe and unknown, and construct a revised program focusing on
those initial states that are not yet known to be safe or unsafe. An
experimental evaluation of the method on a set of software verification
benchmarks shows that it can solve problems which are not solvable using
previous methods.Comment: 19 pages, 8 figure
Review of Top Quark Physics Results
As the heaviest known fundamental particle, the top quark has taken a central
role in the study of fundamental interactions. Production of top quarks in
pairs provides an important probe of strong interactions. The top quark mass is
a key fundamental parameter which places a valuable constraint on the Higgs
boson mass and electroweak symmetry breaking. Observations of the relative
rates and kinematics of top quark final states constrain potential new physics.
In many cases, the tests available with study of the top quark are both
critical and unique. Large increases in data samples from the Fermilab Tevatron
have been coupled with major improvements in experimental techniques to produce
many new precision measurements of the top quark. The first direct evidence for
electroweak production of top quarks has been obtained, with a resulting direct
determination of . Several of the properties of the top quark have been
measured. Progress has also been made in obtaining improved limits on potential
anomalous production and decay mechanisms. This review presents an overview of
recent theoretical and experimental developments in this field. We also provide
a brief discussion of the implications for further efforts.Comment: 119 pages, 55 figure
Measurement of the forward-backward asymmetries for charm- and bottom-quark pair productions at =58GeV with electron tagging
We have measured, with electron tagging, the forward-backward asymmetries of
charm- and bottom-quark pair productions at =58.01GeV, based on
23,783 hadronic events selected from a data sample of 197pb taken with
the TOPAZ detector at TRISTAN. The measured forward-backward asymmetries are
and , which are consistent with the standard model
predictions.Comment: 19 pages, Latex format (article), 5 figures included. to be published
in Phys. Lett.
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