Density Functional approach to Nonlinear Rheology

We present a density functional based closure of the pair Smoluchowski equation for Brownian particles under shear flow. Given an equilibrium free energy functional as input the theory provides first-principles predictions for the flow-distorted pair correlation function and associated rheological quantities over a wide range of volume fractions and flow rates. Taking two-dimensional hard-disks under shear flow as an illustrative model we calculate the pair correlation function, viscosity and normal stress difference under both steady and start-up shear

Simultaneous dynamic characterization of charge and structural motion during ferroelectric switching

Monitoring structural changes in ferroelectric thin films during electric field-induced polarization switching is important for a full microscopic understanding of the coupled motion of charges, atoms and domain walls. We combine standard ferroelectric test-cycles with time-resolved x-ray diffraction to investigate the response of a nanoscale ferroelectric oxide capacitor upon charging, discharging and switching. Piezoelectric strain develops during the electronic RC time constant and additionally during structural domain-wall creep. The complex atomic motion during ferroelectric polarization reversal starts with a negative piezoelectric response to the charge flow triggered by voltage pulses. Incomplete screening limits the compressive strain. The piezoelectric modulation of the unit cell tweaks the energy barrier between the two polarization states. Domain wall motion is evidenced by a broadening of the in-plane components of Bragg reflections. Such simultaneous measurements on a working device elucidate and visualize the complex interplay of charge flow and structural motion and challenges theoretical modelling

The Path Integral for 1+1-dimensional QCD

We derive a path integral expression for the transition amplitude in 1+1-dimensional QCD starting from canonically quantized QCD. Gauge fixing after quantization leads to a formulation in terms of gauge invariant but curvilinear variables. Remainders of the curved space are Jacobians, an effective potential, and sign factors just as for the problem of a particle in a box. Based on this result we derive a Faddeev-Popov like expression for the transition amplitude avoiding standard infinities that are caused by integrations over gauge equivalent configurations.Comment: 16 pages, LaTeX, 3 PostScript figures, uses epsf.st

How to include milkability in dairy cattle breeding

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Analyses of the vrl gene cluster in Desulfococcus multivorans: Homologous to the virulence-associated locus of the ovine footrot pathogen Dichelobacter nodosus strain A198

Major parts of the virulence-associated vrl locus known from the gammaproteobacterium Dichelobacter nodosus, the causative agent of ovine footrot, were analyzed in the genome of the sulfate-reducing deltaproteobacterium Desulfococcus multivorans. In the genome of D. multivorans 13 of the 19 vrl genes described for D. nodosus are present and highly conserved with respect to gene sequence and order. The vrl locus and its flanking regions suggest a bacteriophage-mediated transfer into the genome of D. multivorans. Comparative analysis of the deduced Vrl proteins reveals a wide distribution of parts of the virulence-associated vrl locus in distantly related bacteria. Horizontal transfer is suggested as driving mechanism for the circulation of the vrl genes in bacteria. Except for the vrlBMN genes D. multivorans and Desulfovibrio desulfuricans G20 together contain all vrl genes displaying a high degree of similarity. For D. multivorans it could be shown that guanine plus cytosine (GC) content, GC skew, di-, tri- or tetranucleotide distribution did not differ between the vrl locus and its flanking sequences. This could be a hint that the vrl locus originated from a related organism or at least a genome with similar characteristics. The conspicuous high degree of conservation of the analyzed vrl genes may result from a recent transfer event or reflect a function of the vrl genes, which is still unknown and not necessarily disease associated. The latter is supported by the evidence for expression of the vrl genes in D. multivorans, which has not been described as pathogen or to be associated to any disease pattern before

Formation of fundamental structures in Bose-Einstein Condensates

The meanfield interaction in a Bose condensate provides a nonlinearity which can allow stable structures to exist in the meanfield wavefunction. We discuss a number of examples where condensates, modelled by the one dimensional Gross Pitaevskii equation, can produce gray solitons and we consider in detail the case of two identical condensates colliding in a harmonic trap. Solitons are shown to form from dark interference fringes when the soliton structure, constrained in a defined manner, has lower energy than the interference fringe and an analytic expression is given for this condition.Comment: 7 pages, 3 figures, requires ioplppt.st

Stationary solutions of the one-dimensional nonlinear Schroedinger equation: I. Case of repulsive nonlinearity

All stationary solutions to the one-dimensional nonlinear Schroedinger equation under box and periodic boundary conditions are presented in analytic form. We consider the case of repulsive nonlinearity; in a companion paper we treat the attractive case. Our solutions take the form of stationary trains of dark or grey density-notch solitons. Real stationary states are in one-to-one correspondence with those of the linear Schr\"odinger equation. Complex stationary states are uniquely nonlinear, nodeless, and symmetry-breaking. Our solutions apply to many physical contexts, including the Bose-Einstein condensate and optical pulses in fibers.Comment: 11 pages, 7 figures -- revised versio

Adiabatic Compression of Soliton Matter Waves

The evolution of atomic solitary waves in Bose-Einstein condensate (BEC) under adiabatic changes of the atomic scattering length is investigated. The variations of amplitude, width, and velocity of soliton are found for both spatial and time adiabatic variations. The possibility to use these variations to compress solitons up to very high local matter densities is shown both in absence and in presence of a parabolic confining potential.Comment: to appear in J.Phys.