6,605 research outputs found
Microscopic Model versus Systematic Low-Energy Effective Field Theory for a Doped Quantum Ferromagnet
We consider a microscopic model for a doped quantum ferromagnet as a test
case for the systematic low-energy effective field theory for magnons and
holes, which is constructed in complete analogy to the case of quantum
antiferromagnets. In contrast to antiferromagnets, for which the effective
field theory approach can be tested only numerically, in the ferromagnetic case
both the microscopic and the effective theory can be solved analytically. In
this way the low-energy parameters of the effective theory are determined
exactly by matching to the underlying microscopic model. The low-energy
behavior at half-filling as well as in the single- and two-hole sectors is
described exactly by the systematic low-energy effective field theory. In
particular, for weakly bound two-hole states the effective field theory even
works beyond perturbation theory. This lends strong support to the quantitative
success of the systematic low-energy effective field theory method not only in
the ferromagnetic but also in the physically most interesting antiferromagnetic
case.Comment: 34 pages, 1 figur
PraxisĂŒberprĂŒfung und Optimierung von Peronospora- und OidiumbekĂ€mpfungsmaĂnahmen im ökologischen Weinbau - Alternativen zum Einsatz von Kupfer und Schwefel
Aus langjĂ€hrigen Erfahrungen und der kontinuierlichen Zusammenarbeit zwischen den Herstellerfirmen, den beteiligten Betrieben und den Lehr- und Versuchsanstalten sowie ECO-CONSULT als wissenschaftlicher Koordinator der VersuchsdurchfĂŒhrung, wurden in den Untersuchungsjahren 2002/2003 auf drei Standorten (Trier, Landau und Korb) Versuche zur PeronosporabekĂ€mpfung sowie auf einem Standort (Korb) Versuche zur BekĂ€mpfung von Oidium angelegt.
Die Auswahl der eingesetzten Mittel ergab sich aus dem aktuellen Stand der Zulassung von PflanzenstĂ€rkungs- Schutzmittel sowie Neu- und Weiterentwicklungen der Firmen., so dass immer die aktuellsten PrĂ€parate fĂŒr die Praxis getestet werden. Durch diese enge Zusammenarbeit ist es möglich die Ergebnisse unmittelbar sowohl in der Beratung (Field days, Beraterinformation) wie auch in der Weiterentwicklung und Kommerzialisierung durch die Firmen einzusetzen.
Ergebnisse
Die Witterungs- und Infektionsbedingungen fĂŒr Peronospora waren im Versuchsjahr 2002 extrem gĂŒnstig fĂŒr das Auftreten der Peronospora. Schon sehr frĂŒh traten erste Befallssymptome an den BlĂ€ttern als Ălflecke auf. Die Hauptinfektionszeit lag um die BlĂŒte sowie im Zeitraum Fruchtansatz bis ErbsengröĂe der Beeren. In der unbehandelten Kontrolle waren schon frĂŒh annĂ€hernd alle Trauben befallen. Es zeigt sich, dass unter den unterschiedlichen Bedingungen die eingesetzten VersuchsprĂ€parate sowohl gute als auch unzureichende Wirkung hatten. Ein direkter Vergleich ist daher sehr schwierig. Dennoch zeigt sich, dass je nach Befallssituation die Varianten 9 x Kupfer in einer Gesamtkupferaufwandmenge von 3 kg die gleiche Wirkung zeigte wie die PrĂ€parate MYCO-SIN VIN, Ulmasud und Ulmasud VP.
Im Versuchsjahr 2003 trat nur zu Beginn der BlĂŒtezeit vereinzelt Peronospora auf. Infolge der Witterungsbedingungen kam es zu keinem stĂ€rkeren Befall. In der Versuchsanlage Trier trat, wie auch insgesamt im Anbaugebiet, verstĂ€rkt SchwarzfĂ€ule auf.
Bei der Bonitur zeigten sich positive Ergebnisse bei den PrĂ€paraten: Frutogard, Phyto-Algin Super sowie MYCO-SIN VIN. Der Wirkungsgrad lag gegenĂŒber der reinen Schwefelbehandlung bei ĂŒber 60%.
Oidium trat in den beiden Versuchsjahren nur zum Ende der Vegetation an den BlÀttern auf.
Neben Botrytis wurde in der Versuchsanlage Landau Nussdorf Weingut Rummel zusĂ€tzlich noch auf SauerfĂ€ule sowie Penicillium bonitiert. Penicillium ist ein tertiĂ€rer SchwĂ€che â FĂ€ulnisparasit, der sich zusammen mit Botrytis auf den Trauben ansiedelt. Penicillium stellte in den letzten Jahren zusammen mit SauerfĂ€ule eine nicht unerhebliche BeeintrĂ€chtigung des Lesegutes und somit auch der WeinqualitĂ€t dar. Bei der Bonitur ergaben sch vergleichsweise geringe Befallswerte, die sich aber nach den anschlieĂenden NiederschlĂ€gen deutlich verstĂ€rkten. Die Befallswerte lagen zwischen 12 und 26%. Ebenso ist das Auftreten von SauerfĂ€ule zwischen den Boniturergebnissen deutlich angestiegen. Der Befall lag bei 40%. Die Variante Ulmasud VP zeigte sowohl im Befall durch Botrytis, Penicillium wie auch EssigsĂ€ure die geringsten Befallswerte. Gerade im Befall mit Penicillium und EssigsĂ€ure waren die Unterschiede zwar statistisch nicht ab zu sichern aber doch um 50% geringer als in der Variante OekoFluid
Constraint Effective Potential of the Staggered Magnetization in an Antiferromagnet
We employ an improved estimator to calculate the constraint effective
potential of the staggered magnetization in the spin quantum
Heisenberg model using a loop-cluster algorithm. The first and second moment of
the probability distribution of the staggered magnetization are in excellent
agreement with the predictions of the systematic low-energy magnon effective
field theory. We also compare the Monte Carlo data with the universal shape of
the constraint effective potential of the staggered magnetization and study its
approach to the convex effective potential in the infinite volume limit. In
this way the higher-order low-energy parameter is determined from a fit
to the numerical data
Optimisation of downy mildew (Plasmopara viticola) control in organic viticulture with low copper doses, new copper formulations and plant strengtheners, results of four years of on farm research
In three different wine growing regions in Germany, due to weather and infection conditions several fungicide (copper formulations) and plant strengtheners (Myco-Sin VINÂź, KendalÂź, Frutogard Âź) applications against downy mildew are required in order to obtain satisfactory disease control. Results of the four years of on farm trials confirmed good efficacy of the copper based substances like copper hydroxide, partly in combination with two or three applications of potassium phosphonate, new copper-hydroxide formulation or copper oxychloride used in a low doses of copper and alternative products like Myco-Sin-VINÂź (clay with high aluminium content) in combination with KendalÂź ( plant extract)
Systematic Effective Field Theory Investigation of Spiral Phases in Hole-Doped Antiferromagnets on the Honeycomb Lattice
Motivated by possible applications to the antiferromagnetic precursor of the
high-temperature superconductor NaCoOyHO, we use a systematic
low-energy effective field theory for magnons and holes to study different
phases of doped antiferromagnets on the honeycomb lattice. The effective action
contains a leading single-derivative term, similar to the Shraiman-Siggia term
in the square lattice case, which gives rise to spirals in the staggered
magnetization. Depending on the values of the low-energy parameters, either a
homogeneous phase with four or a spiral phase with two filled hole pockets is
energetically favored. Unlike in the square lattice case, at leading order the
effective action has an accidental continuous spatial rotation symmetry.
Consequently, the spiral may point in any direction and is not necessarily
aligned with a lattice direction.Comment: 10 pages, 6 figure
The effect of electron-electron correlation on the attoclock experiment
We investigate multi-electron effects in strong-field ionization of Helium
using a semi-classical model that, unlike other commonly used theoretical
approaches, takes into account electron-electron correlation. Our approach has
an additional advantage of allowing to selectively switch off different
contributions from the parent ion (such as the remaining electron or the
nuclear charge) and thereby investigate in detail how the final electron angle
in the attoclock experiment is influenced by these contributions. We find that
the bound electron exerts a significant effect on the final electron momenta
distribution that can, however, be accounted for by an appropriately selected
mean field. Our results show excellent agreement with other widely used
theoretical models done within a single active electron approximation
Assessment of Physical Activity Patterns in Adolescent Patients With Anorexia Nervosa and Their Effect on Weight Gain
(1) Background: Altered physical activity (PA) affects weight recovery in anorexia nervosa (AN) patients. The study aimed to objectively characterize PA patterns and their effect on weight trajectory in adolescent AN patients.
(2) Methods: PA was assessed in 47 patients on admission to inpatient treatment, in n = 25 of these patients again 4 weeks after discharge (follow-up, FU), as well as in 20 adolescent healthy controls using the Sense Wearâą armband. The following PA categories were defined by metabolic equivalent (MET) ranges: sedentary behavior (SB), light (LPA), moderate (MPA), vigorous (VPA), and high-level PA (HLPA= MPA + VPA).
(3) Results: LPA on admission was significantly higher in AN patients than in controls (103 vs. 55 min/d, p < 0.001), and LPA in AN decreased over time to 90 min/d (p = 0.006). Patients with higher admission LPA (n = 12) still had elevated LPA at FU (p = 0.003). High admission LPA was associated with a higher inpatient BMI percentage gain (ÎBMI%; 18.2% ± 10.0% vs. 12.0% ± 9.7%, p = 0.037) but with a loss of ÎBMI% at FU (-2.3% ± 3.6% vs. 0.8% ± 3.6%, p = 0.045). HLPA at baseline was associated with a lower inpatient ÎBMI% (p = 0.045).
(4) Conclusion: Elevated LPA in AN patients decreased after inpatient treatment, and PA patterns had an impact on weight trajectory
Exact Insulating and Conducting Ground States of a Periodic Anderson Model in Three Dimensions
We present a class of exact ground states of a three-dimensional periodic
Anderson model at 3/4 filling. Hopping and hybridization of d and f electrons
extend over the unit cell of a general Bravais lattice. Employing novel
composite operators combined with 55 matching conditions the Hamiltonian is
cast into positive semidefinite form. A product wave function in position space
allows one to identify stability regions of an insulating and a conducting
ground state. The metallic phase is a non-Fermi liquid with one dispersing and
one flat band.Comment: 4 pages, 3 figure
Spiral phases and two-particle bound states from a systematic low-energy effective theory for magnons, electrons, and holes in an antiferromagnet
We have constructed a systematic low-energy effective theory for hole- and
electron-doped antiferromagnets, where holes reside in momentum space pockets
centered at and where electrons live in
pockets centered at or . The effective
theory is used to investigate the magnon-mediated binding between two holes or
two electrons in an otherwise undoped system. We derive the one-magnon exchange
potential from the effective theory and then solve the corresponding
two-quasiparticle Schr\"odinger equation. As a result, we find bound state wave
functions that resemble -like or -like symmetry. We also
study possible ground states of lightly doped antiferromagnets.Comment: 2 Pages; Proc. of SCES'07, Housto
Radiative corrections to the pressure and the one-loop polarization tensor of massless modes in SU(2) Yang-Mills thermodynamics
We compute the one-loop polarization tensor for the on-shell, massless
mode in a thermalized SU(2) Yang-Mills theory being in its deconfining phase.
Postulating that SU(2), we discuss
's effect on the low-momentum part of the black-body spectrum at
temperatures where K.
A table-top experiment is proposed to test the above postulate. As an
application, we point out a possible connection with the stability of dilute,
cold, and old innergalactic atomic hydrogen clouds. We also compute the
two-loop correction to the pressure arising from the instantaneous massless
mode in unitary-Coulomb gauge, which formerly was neglected, and present
improved estimates for subdominant corrections.Comment: 25 pages, 17 figs, v4: consequences of a modification of the
evolution equation for the effectice coupling implemented, no qualitative
change of the physic
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