Weed Control with Straw Residues in Occasional Direct Seeding of Faba Bean (Vicia faba sp.) in Organic Agriculture

In order to gain momentum in the consolidation process of no-tillage systems in Europe’s Organic Agriculture, occasional direct seeding (DS) of faba bean (FAB) into a mulch layer of residues from precrop oats should be scrutinized. In contrast to non-legumes, grain legumes do not depend on soil-borne nitrogen due to their ability to fix nitrogen symbiotically. Concerning weed infestation, straw residues left by precrops may at least physically suppress weeds. In order to prove this hypothesis, two field experiments were carried out in 2009 at two sites in the lower Rhineland region, Germany. DS treatments were combined with 0, 4, and 6 t ha-1 of straw residues. Mouldboard ploughing (MP) combined with conventional seedbed preparation was used as control. Compared to the DS treatment without straw residue (0 t ha-1), DS treatments with straw residues (4 and 6 t ha-1, resp.) resulted in significantly lower weed density (70 and 84 % resp.). Neither differences were observed in both shoot dry matter of FAB and weeds for DS with straw residues compared with MP, nor for the grain yields of FAB. We conclude that occasional DS of FAB in OA is successful to reduce annual weeds sufficiently and may not lead to reduced FAB yields

Open Space – a collaborative process for facilitating Tourism IT partnerships

The success of IT projects depends on the success of the partnerships on which they are based. However past research by the author has identified a significant rate of failure in these partnerships, predominantly due to an overly technical mindset, leading to the question: “how do we ensure that, as technological solutions are implemented within tourism, due consideration is given to human-centred issues?” The tourism partnership literature is explored for additional insights revealing that issues connected with power, participation and normative positions play a major role. The method, Open Space, is investigated for its ability to engage stakeholders in free and open debate. This paper reports on a one-day Open Space event sponsored by two major intermediaries in the UK travel industry who wanted to consult their business partners. Both the running of the event and its results reveal how Open Space has the potential to address some of the weaknesses associated with tourism partnerships

Magnetic Resonant excitations in High-{Tc\rm T_c} superconductors

The observation of an unusual spin resonant excitation in the superconducting state of various High-Tc ~copper oxides by inelastic neutron scattering measurements is reviewed. This magnetic mode % (that does not exist in conventional superconductors) is discussed in light of a few theoretical models and likely corresponds to a spin-1 collective mode.Comment: 4 figures, Proceedings conference MSM'03 (september 2003) in Monastir (Tunisia) to be published in Phys. Stat. Solid

Quasiparticles in the Kondo lattice model at partial fillings of the conduction band

We study the spectral properties of the one-dimensional Kondo lattice model as function of the exchange coupling, the band filling, and the quasimomentum in the ferromagnetic and paramagnetic phase. Using the density-matrix renormalization group method, we compute the dispersion relation of the quasiparticles, their lifetimes, and the Z-factor. As a main result, we provide evidence for the existence of the spinpolaron at partial band fillings. We find that the quasiparticle lifetime differs by orders of magnitude between the ferromagnetic and paramagnetic phase and depends strongly on the quasimomentum.Comment: 9 pages, 9 figure

Is there a universality of the helix-coil transition in protein models?

The similarity in the thermodynamic properties of two completely different theoretical models for the helix-coil transition is examined critically. The first model is an all-atomic representation for a poly-alanine chain, while the second model is a minimal helix-forming model that contains no system specifics. Key characteristics of the helix-coil transition, in particular, the effective critical exponents of these two models agree with each other, within a finite-size scaling analysis.Comment: Latex, to appear in Eur. Phys. J.

Spin waves cause non-linear friction

Energy dissipation is studied for a hard magnetic tip that scans a soft magnetic substrate. The dynamics of the atomic moments are simulated by solving the Landau-Lifshitz-Gilbert (LLG) equation numerically. The local energy currents are analysed for the case of a Heisenberg spin chain taken as substrate. This leads to an explanation for the velocity dependence of the friction force: The non-linear contribution for high velocities can be attributed to a spin wave front pushed by the tip along the substrate.Comment: 5 pages, 9 figure

Spin waves cause non-linear friction

Energy dissipation is studied for a hard magnetic tip that scans a soft magnetic substrate. The dynamics of the atomic moments are simulated by solving the Landau-Lifshitz-Gilbert (LLG) equation numerically. The local energy currents are analysed for the case of a Heisenberg spin chain taken as substrate. This leads to an explanation for the velocity dependence of the friction force: The non-linear contribution for high velocities can be attributed to a spin wave front pushed by the tip along the substrate.Comment: 5 pages, 9 figure

A Strictly Single-Site DMRG Algorithm with Subspace Expansion

We introduce a strictly single-site DMRG algorithm based on the subspace expansion of the Alternating Minimal Energy (AMEn) method. The proposed new MPS basis enrichment method is sufficient to avoid local minima during the optimisation, similarly to the density matrix perturbation method, but computationally cheaper. Each application of $\hat H$ to $|\Psi\rangle$ in the central eigensolver is reduced in cost for a speed-up of $\approx (d + 1)/2$, with $d$ the physical site dimension. Further speed-ups result from cheaper auxiliary calculations and an often greatly improved convergence behaviour. Runtime to convergence improves by up to a factor of 2.5 on the Fermi-Hubbard model compared to the previous single-site method and by up to a factor of 3.9 compared to two-site DMRG. The method is compatible with real-space parallelisation and non-abelian symmetries.Comment: 9 pages, 6 figures; added comparison with two-site DMR