40 research outputs found
Ermittlung der Futterqualität verschiedener Wintererbsengenotypen in Rein- und Gemengesaat zur Nutzung als nachwachsender Rohstoff, als Grünfutter und als Druschfrucht
Normalblättrige Wintererbsen sind in Reinsaat eine rohproteinreiche Winterzwischenfrucht für die Nutzung als Grünfutter oder als nachwachsender Rohstoff zur Energiegewinnung im Rahmen von Zweikulturnutzungssystemen. Zum Korndrusch im Gemengeanbau stellen sie bei mindestens vergleichbaren Kornerträgen und Qualitäten eine Alternative zu Sommererbsen dar. Dabei können Anbauprobleme von Sommererbsen besonders hinsichtlich der Unkrautregulierung reduziert werden
Order by Disorder in Spin-Orbit Coupled Bose-Einstein Condensates
Motivated by recent experiments, we investigate the system of
isotropically-interacting bosons with Rashba spin-orbit coupling. At the
non-interacting level, there is a macroscopic ground-state degeneracy due to
the many ways bosons can occupy the Rashba spectrum. Interactions treated at
the mean-field level restrict the possible ground-state configurations, but
there remains an accidental degeneracy not corresponding to any symmetry of the
Hamiltonian, indicating the importance of fluctuations. By finding analytical
expressions for the collective excitations in the long-wavelength limit and
through numerical solution of the full Bogoliubov- de Gennes equations, we show
that the system condenses into a single momentum state of the Rashba spectrum
via the mechanism of order by disorder. We show that in 3D the quantum
depletion for this system is small, while the thermal depletion has an infrared
logarithmic divergence, which is removed for finite-size systems. In 2D, on the
other hand, thermal fluctuations destabilize the system.Comment: 5 page
Polymeric Surfactant P84/Polyoxometalate α-PW12O403- A Model System to Investigate the Interplay between Chaotropic and Hydrophobic Effects
Low charge density nanometric ions were recently shown to bind strongly to neutral hydrated matter in aqueous solution. This phenomenon, called the (super-)chaotropic effect, arises from the partial dehydration of both the nano-ion and the solute, leading to a significant gain in enthalpy. Here, we investigate the chaotropic effect of the polyoxometalate α-PW12O403− on the triblock copolymer P84: (EO)19(PO)43(EO)19 with (EO)19 the polyethoxylated and (PO)43 the polypropoxylated chains. The combination of phase diagrams, spectroscopic (nuclear magnetic resonance) and scattering (small angle neutron/X-ray scattering) techniques revealed that: (i) below the micellization temperature of P84, PW12O403− exclusively binds to the propylene oxide moiety of P84 unimers; and (ii) above the micellization temperature, PW12O403− mostly adsorbs on the ethylene oxide micellar corona. The preferential binding of the PW12O403− to the PPO chain over the PEO chains suggests that the binding is driven by the chaotropic effect and is reinforced by the hydrophobic effect. At higher temperatures, copolymer micellization leads to the displacement of PW12O403− from the PPO chain to the PEO chains. This study deepens our understanding of the subtle interplay between the chaotropic and hydrophobic effects in complex salt-organic matter solutions
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
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
Zerspanarbeit und Schnitttemperatur beim Bohren faserverstärkter Kunststoffe: HGF-Kurzberichte 87/50.
Die Kenntnis des Temperaturverhaltens von Werkzeug und Werkstueck ist bei der spanenden Bearbeitung faserverstaerkter Kunststoffe von grosser Bedeutung, um thermische Werkstoffschaeden des Verbundes zu vermeiden. Mit Hilfe thermographischer Temperatur- und Temperaturverteilungsmessungen werden Werkzeugtemperaturen und Zerspanwaerme beim Bohren von Glas- und Kohlenstoffaserwerkstoffen bestimmt. (IPT