Robustness of Fractional Quantum Hall States with Dipolar Atoms in Artificial Gauge Fields

The robustness of fractional quantum Hall states is measured as the energy gap separating the Laughlin ground-state from excitations. Using thermodynamic approximations for the correlation functions of the Laughlin state and the quasihole state, we evaluate the gap in a two-dimensional system of dipolar atoms exposed to an artificial gauge field. For Abelian fields, our results agree well with the results of exact diagonalization for small systems, but indicate that the large value of the gap predicted in [Phys. Rev. Lett. 94, 070404 (2005)] was overestimated. However, we are able to show that the small gap found in the Abelian scenario is dramatically increased if we turn to non-Abelian fields squeezing the Landau levels

Energiepflanzenanbau für die Biogaserzeugung im Ökologischen Landbau

The interest in the cultivation of energy plants for the biogas production is increasing in organic agriculture. But this cropping has to be designed according to the principles of organic farming and sustainable agriculture. Therefore in the research project ÖKOVERS different energy crops as a part of a standard crop rotation are compared in two different cropping systems. Cropping system 1 is a double cropping system with a mixture of grass/clover harvested in spring as first crop and a following second crop like sunflowers, maize, sorghum, amaranth, buckwheat and others. The second system is a mixture of grass/clover with several cuts during one year. The highest yield was obtained with the mixture of grass/clover in the second system with 18,5 t ha-1. Also the highest methane yield with 5100 Nm3 ha -1 was achieved with the grass/clover mixture. The different summer crops after grass/clover mixture were affected by drought during the summer and early frost in autumn. Hence the mixture of grass/clover was a good alternative to maize. These results will be checked in further researches

Non-Abelian spin singlet states of two-component Bose gases in artificial gauge fields

We study strongly correlated phases of a pseudo-spin-1/2 Bose gas in an artificial gauge field using the exact diagonalization method. The atoms are confined in two dimensions and interact via a two-body contact potential. In Abelian gauge fields, pseudo-spin singlets are favored by pseudo-spin independent interactions. We find a series of incompressible phases at fillings \nu=2k/3. By comparison with the non-Abelian spin singlet (NASS) states, constructed as zero-energy eigenstates of a (k+1)-body contact interaction, we classify the non-trivial topology of the states. An additional spin-orbit coupling is shown to switch between NASS-like states and spin-polarized phases from the Read-Rezayi series.Comment: 4 pages, 3 figure

Bestimmung der N-Fixierung unterschiedlicher Wintererbsengenotypen im Vergleich zu einer Sommererbse in Rein- und Gemengesaat

In organic farming the cultivation of leguminous crops is one of the most important sources of nitrogen (N). However, regarding the amount of N fixed, there are hardly any published data for winter peas. Therefore, the N fixation of five regular leafed winter peas types and one semi-leafless spring pea cultivar in single and mixed cropping (with winter rye spring cereals respectively) was measured in four successive growing seasons (2003/04 – 2006/07) at the experimental farm of the University of Kassel and in two consecutive vegetation periods (2005/06 - 2006/07) at the experimental farm of the University of Applied Science in Osnabrueck. The amount of N fixed was calculated according to the extended difference method at the beginning of flowering and at grain harvest. N fixation was usually higher for winter peas than for spring pea. At the beginning of flowering the amount of N fixed in pure stands was with a mean value of 92 kg ha-1 for winter peas and 29 kg ha-1 for the spring pea higher than in mixture with a mean value of 42 and 15 kg ha-1 respectively. At grain harvest the amount of N fixed for the spring pea in pure stands was higher than in mixtures with a mean of 65 and 33 kg ha-1 respectively. On the other hand the N fixation for winter peas was usually comparable in pure and mixed stands with a mean of 100 and 86 kg ha-1 respectively. This was a consequence of the higher pea grain yield in mixture than in pure stands and of a reduced biomass (leaves) loss in mixtures. Therefore, regular leaf winter peas can contribute to the N supply of the crop rotation better than spring peas

Bias-voltage dependence of the magneto-resistance in ballistic vacuum tunneling: Theory and application to planar Co(0001) junctions

Motivated by first-principles results for jellium and by surface-barrier shapes that are typically used in electron spectroscopies, the bias voltage in ballistic vacuum tunneling is treated in a heuristic manner. The presented approach leads in particular to a parameterization of the tunnel-barrier shape, while retaining a first-principles description of the electrodes. The proposed tunnel barriers are applied to Co(0001) planar tunnel junctions. Besides discussing main aspects of the present scheme, we focus in particular on the absence of the zero-bias anomaly in vacuum tunneling.Comment: 19 pages with 8 figure

Fractional quantum Hall states of few bosonic atoms in geometric gauge fields

We employ the exact diagonalization method to analyze the possibility of generating strongly correlated states in two-dimensional clouds of ultracold bosonic atoms which are subjected to a geometric gauge field created by coupling two internal atomic states to a laser beam. Tuning the gauge field strength, the system undergoes stepwise transitions between different ground states, which we describe by analytical trial wave functions, amongst them the Pfaffian, the Laughlin, and a Laughlin quasiparticle many-body state. The adiabatic following of the center of mass movement by the lowest energy dressed internal state, is lost by the mixing of the second internal state. This mixture can be controlled by the intensity of the laser field. The non-adiabaticity is inherent to the considered setup, and is shown to play the role of circular asymmetry. We study its influence on the properties of the ground state of the system. Its main effect is to reduce the overlap of the numerical solutions with the analytical trial expressions by occupying states with higher angular momentum. Thus, we propose generalized wave functions arising from the Laughlin and Pfaffian wave function by including components, where extra Jastrow factors appear, while preserving important features of these states. We analyze quasihole excitations over the Laughlin and generalized Laughlin states, and show that they possess effective fractional charge and obey anyonic statistics. Finally, we study the energy gap over the Laughlin state as the number of particles is increased keeping the chemical potential fixed. The gap is found to decrease as the number of particles is increased, indicating that the observability of the Laughlin state is restricted to a small number of particles.Comment: 28 pages, 16 figure

Motion style acupuncture treatment (MSAT) for acute low back pain with severe disability: a multicenter, randomized, controlled trial protocol

<p>Abstract</p> <p>Background</p> <p>Acupuncture is widely-used to treat patients with low back pain, despite insufficient evidence of the technique's efficacy for acute back pain. Motion style acupuncture treatment (MSAT) is a non-traditional acupuncture treatment requiring a patient to exercise while receiving acupuncture. In Korea, MSAT is used to reduce musculoskeletal pain and improve functional status. The study aims to evaluate the effect of MSAT on acute low back pain with severe disability.</p> <p>Methods/Design</p> <p>This study is a multicenter, randomized, active-controlled trial with two parallel arms. Participants with acute low back pain and severe functional disability, defined as an Oswestry Disability Index (ODI) value > 60%, will be randomly allocated to the acupuncture group and the nonsteroidal anti-inflammatory drug (NSAID) injection group. The acupuncture group will receive MSAT and the NSAID injection group will receive an intramuscular injection of diclofenac. All procedures will be limited to one session and the symptoms before and after treatment will be measured by assessors blinded to treatment allocation. The primary outcome will be measured at 30 minutes after treatment using the numerical rating scale (NRS) of low back pain while the patient is moving. Secondary outcomes will be measured at 30 minutes after treatment using the NRS of leg pain, ODI, patient global impression of change, range of motion (ROM) of the lumbar spine, and degrees of straight leg raising (SLR). Post-treatment follow-up will be performed to measure primary and secondary outcomes with the exception of ROM and SLR at 2, 4, and 24 weeks after treatment.</p> <p>Discussion</p> <p>The results of this trial will be discussed.</p> <p>Trial Registration</p> <p>ClinicalTrial.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT01315561">NCT01315561</a></p

Determinants of Functional Coupling between Astrocytes and Respiratory Neurons in the Pre-Bötzinger Complex

Respiratory neuronal network activity is thought to require efficient functioning of astrocytes. Here, we analyzed neuron-astrocyte communication in the pre-Bötzinger Complex (preBötC) of rhythmic slice preparations from neonatal mice. In astrocytes that exhibited rhythmic potassium fluxes and glutamate transporter currents, we did not find a translation of respiratory neuronal activity into phase-locked astroglial calcium signals. In up to 20% of astrocytes, 2-photon calcium imaging revealed spontaneous calcium fluctuations, although with no correlation to neuronal activity. Calcium signals could be elicited in preBötC astrocytes by metabotropic glutamate receptor activation or after inhibition of glial glutamate uptake. In the latter case, astrocyte calcium elevation preceded a surge of respiratory neuron discharge activity followed by network failure. We conclude that astrocytes do not exhibit respiratory-rhythmic calcium fluctuations when they are able to prevent synaptic glutamate accumulation. Calcium signaling is, however, observed when glutamate transport processes in astrocytes are suppressed or neuronal discharge activity is excessive