Intermittency and non-Gaussian fluctuations of the global energy transfer in fully developed turbulence

We address the experimentally observed non-Gaussian fluctuations for the energy injected into a closed turbulent flow at fixed Reynolds number. We propose that the power fluctuations mirror the internal kinetic energy fluctuations. Using a stochastic cascade model, we construct the excess kinetic energy as the sum over the energy transfers at different levels of the cascade. We find an asymmetric distribution that strongly resembles the experimental data. The asymmetry is an explicit consequence of intermittency and the global measure is dominated by small scale events correlated over the entire system. Our calculation is consistent with the statistical analogy recently made between a confined turbulent flow and a critical system of finite size.Comment: To appear in Physical Review Letter

Numerical study of dynamo action at low magnetic Prandtl numbers

We present a three--pronged numerical approach to the dynamo problem at low magnetic Prandtl numbers $P_M$. The difficulty of resolving a large range of scales is circumvented by combining Direct Numerical Simulations, a Lagrangian-averaged model, and Large-Eddy Simulations (LES). The flow is generated by the Taylor-Green forcing; it combines a well defined structure at large scales and turbulent fluctuations at small scales. Our main findings are: (i) dynamos are observed from $P_M=1$ down to $P_M=10^{-2}$; (ii) the critical magnetic Reynolds number increases sharply with $P_M^{-1}$ as turbulence sets in and then saturates; (iii) in the linear growth phase, the most unstable magnetic modes move to small scales as $P_M$ is decreased and a Kazantsev $k^{3/2}$ spectrum develops; then the dynamo grows at large scales and modifies the turbulent velocity fluctuations.Comment: 4 pages, 4 figure

Intravital imaging reveals p53-dependent cancer cell death induced by phototherapy via calcium signaling.

One challenge in biology is signal transduction monitoring in a physiological context. Intravital imaging techniques are revolutionizing our understanding of tumor and host cell behaviors in the tumor environment. However, these deep tissue imaging techniques have not yet been adopted to investigate the second messenger calcium (Ca2+). In the present study, we established conditions that allow the in vivo detection of Ca2+ signaling in three-dimensional tumor masses in mouse models. By combining intravital imaging and a skinfold chamber technique, we determined the ability of photodynamic cancer therapy to induce an increase in intracellular Ca2+ concentrations and, consequently, an increase in cell death in a p53-dependent pathway

Characterizing flows with an instrumented particle measuring Lagrangian accelerations

We present in this article a novel Lagrangian measurement technique: an instrumented particle which continuously transmits the force/acceleration acting on it as it is advected in a flow. We develop signal processing methods to extract information on the flow from the acceleration signal transmitted by the particle. Notably, we are able to characterize the force acting on the particle and to identify the presence of a permanent large-scale vortex structure. Our technique provides a fast, robust and efficient tool to characterize flows, and it is particularly suited to obtain Lagrangian statistics along long trajectories or in cases where optical measurement techniques are not or hardly applicable.Comment: submitted to New Journal of Physic

Editorial - A tailored approach in geriatric oncology: turning a problem into an opportunity for the elderly

No abstract availabl

Comparative mapping of human chromosome 13 genes in the pig shows a similar gene arrangement

Previous comparative mapping between the human and pig genomes suggested complete conservation of human chromosome 13 (HSA13) to pig chromosome 11 (SSC11). The objectives of this study were comparative gene mapping of pig homologs of HSA13 genes and an examination of gene order within this conserved synteny group by physical assignment of each locus. A detailed HSA13 to SSC11 comparison was chosen since the comparative gene map is not well developed for these chromosomes and a rearranged gene order within conserved synteny groups was observed from the comparison between human chromosome 13 and bovine chromosome 12. Pig sequence tagged sites (STSs) for six HSA13 genes were developed and physically mapped using a somatic cell hybrid panel (SCHP) to SSC11 with 85–100% concordance. Fluorescent in situ hybridization (FISH) mapping also was applied to determine the gene order within each subchromosomal region. Results from this study increase the comparative information available on SSC11 and suggest the same gene order among examined loci on SSC11 and HSA13

Comparative mapping of human chromosome 3 genes in the pig shows different gene order

A comparative map of human chromosome 3 (HSA3) and pig chromosome 13 (SSC13) was constructed using physically assigned pig sequence tagged sites (STSs). Pig STS representing 11 HSA3 genes were developed and 10 pig STS were regionally mapped using a somatic cell hybrid panel (SCHP) to SSC13 with 80–100% concordance. Large-insert probes were obtained by screening a YAC library with primers for each STS. YACs were identified for DRD3, GAP43, PIT1, SI, and SST for fluorescent in situ hybridization (FISH) mapping. Single gene and bicolor FISH with each pairwise combination was used to further define gene order on SSC13. These data confrim chromosome painting results that showed HSA3 probes hybridize to a major portion of pig chromosome 13 and demonstrate extensive gene rearrangements within this conserved synteny group

Relevance of soft modes for order parameter fluctuations in the Two-Dimensional XY model

We analyse the spin wave approximation for the 2D-XY model, directly in reciprocal space. In this limit the model is diagonal and the normal modes are statistically independent. Despite this simplicity non-trivial critical properties are observed and exploited. We confirm that the observed asymmetry for the probability density function for order parameter fluctuations comes from the divergence of the mode amplitudes across the Brillouin zone. We show that the asymmetry is a many body effect despite the importance played by the zone centre. The precise form of the function is dependent on the details of the Gibbs measure, giving weight to the idea that an effective Gibbs measure should exist in non-equilibrium systems, if a similar distribution is observed.Comment: 12 pages, 9 figure

Reply to Comment on " Universal Fluctuations in Correlated Systems"

Reply to the comment, cond-mat/0209398 by by N.W. Watkins, S.C. Chapman, and G. RowlandsComment: To appear In Physical Review Letter