Scaling and Dissipation in the GOY Shell Model

This is a paper about multi-fractal scaling and dissipation in a shell model of turbulence, called the GOY model. This set of equations describes a one dimensional cascade of energy towards higher wave vectors. When the model is chaotic, the high-wave-vector velocity is a product of roughly independent multipliers, one for each logarithmic momentum shell. The appropriate tool for studying the multifractal properties of this model is shown to be the energy current on each shell rather than the velocity on each shell. Using this quantity, one can obtain better measurements of the deviations from Kolmogorov scaling (in the GOY dynamics) than were available up to now. These deviations are seen to depend upon the details of inertial-range structure of the model and hence are {\em not} universal. However, once the conserved quantities of the model are fixed to have the same scaling structure as energy and helicity, these deviations seem to depend only weakly upon the scale parameter of the model. We analyze the connection between multifractality in the velocity distribution and multifractality in the dissipation. Our arguments suggest that the connection is universal for models of this character, but the model has a different behavior from that of real turbulence. We also predict the scaling behavior of time correlations of shell-velocities, of the dissipation,Comment: Revised Versio

Solidification of liquid metal drops during impact

Hot liquid metal drops impacting onto a cold substrate solidify during their subsequent spreading. Here we experimentally study the influence of solidification on the outcome of an impact event. Liquid tin drops are impacted onto sapphire substrates of varying temperature. The impact is visualised both from the side and from below, which provides a unique view on the solidification process. During spreading an intriguing pattern of radial ligaments rapidly solidifies from the centre of the drop. This pattern determines the late-time morphology of the splat. A quantitative analysis of the drop spreading and ligament formation is supported by scaling arguments. Finally, a phase diagram for drop bouncing, deposition and splashing as a function of substrate temperature and impact velocity is provided

Wake-Driven Dynamics of Finite-Sized Buoyant Spheres in Turbulence

Particles suspended in turbulent flows are affected by the turbulence and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation of finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multi-physics based models that account for particle wake effects for a faithful representation of buoyant-sphere dynamics in turbulence.Comment: 5 pages, 4 figures, http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.12450

Transport properties of dense dissipitive hard-sphere fluids for arbitrary energy loss models

The revised Enskog approximation for a fluid of hard spheres which lose energy upon collision is discussed for the case that the energy is lost from the normal component of the velocity at collision but is otherwise arbitrary. Granular fluids with a velocity-dependent coefficient of restitution are an important special case covered by this model. A normal solution to the Enskog equation is developed using the Chapman-Enskog expansion. The lowest order solution describes the general homogeneous cooling state and a generating function formalism is introduced for the determination of the distribution function. The first order solution, evaluated in the lowest Sonine approximation, provides estimates for the transport coefficients for the Navier-Stokes hydrodynamic description. All calculations are performed in an arbitrary number of dimensions.Comment: 27 pages + 1 figur

The Kappa in J/Psi -> Kpplus-piminus-Kminus-piplus

BES II data for J/Psi->K*(890)Kpi reveal a strong kappa peak in the Kpi S-wave near threshold. Both magnitude and phase are determined in slices of Kpi mass by interferences with strong Ko(1430), K1(1270) and K1(1400) signals. The phase variation with mass agrees within errors with LASS data for Kpi elastic scattering. A combined fit is presented to both BES and LASS data. The fit uses a Breit-Wigner amplitude with an s-dependent width containing an Adler zero. The kappa pole is at 760+-20(stat)+-40(syst) - i(420+-45+-60syst) MeV. The S-wave I=0 scattering length a_0 = 0.23+-0.04 (in units of m(pi)) is close to the prediction 0.19+-0.02 of Chiral Perturbation Theory.Comment: 20 pages, 5 figure

Alternative strategies to by-pass the plant-based Azadirachtin-A production

All parts of Neem (Azadirachta indica A. Juss) show a broad spectrum efficacy against insect pests including insecticidal, anti-feedant or insect repellent activities. Several studies have shown that plant cell cultures can produce azadirachtins. We induced more than 40 novel Neem cell lines in modified Murashige and Skoog (MS) media containing different concentrations of auxins and cytokinins. To enhance the Azadirachtin production from 1 mg/l, it was necessary to optimize the media composition separately for biomass and secondary metabolite production. In light of this complex challenge we used our novel fully automated high-throughput microbioreactor system that allows us a fast and controlled batch and fedbatch screening in 48-well microtiter plates. There is increasing evidence that plants like Azadirachta indica contain endophytes which are able to colonize internal plant tissue without causing visible disease symptoms. The estimated high species diversity of endophytes suggests a rich and almost untapped source of new secondary metabolites. We isolated more than 340 endophytes from various plant tissues and tested if they were able to produce Azadirachtin-A. Here, we present data on isolation of endophytes and induction of callus as well as first results of our microbioreactor system