The effect of the Basset history force on particle clustering in Homogeneous and Isotropic Turbulence

We study the effect of the Basset history force on the dynamics of small particles transported in homogeneous and isotropic turbulence and show that this term, often neglected in previous numerical studies, reduces the small-scale clustering typical of inertial particles. The contribution of this force to the total particle acceleration is, on average, responsible for about 10% of the total acceleration and particularly relevant during rare strong events. At moderate density ratios, i.e. sand or metal powder in water, its presence alters the balance of forces determining the particle acceleration

On the time scales and structure of Lagrangian intermittency in homogeneous isotropic turbulence

We present a study of Lagrangian intermittency and its characteristic time scales. Using the concepts of flying and diving residence times above and below a given threshold in the magnitude of turbulence quantities, we infer the time spectra of the Lagrangian temporal fluctuations of dissipation, acceleration and enstrophy by means of a direct numerical simulation in homogeneous and isotropic turbulence. We then relate these time scales, first, to the presence of extreme events in turbulence and, second, to the local flow characteristics. Analyses confirm the existence in turbulent quantities of holes mirroring bursts, both of which are at the core of what constitutes Lagrangian intermittency. It is shown that holes are associated with quiescent laminar regions of the flow. Moreover, Lagrangian holes occur over few Kolmogorov time scales while Lagrangian bursts happen over longer periods scaling with the global decorrelation time scale, hence showing that loss of the history of the turbulence quantities along particle trajectories in turbulence is not continuous. Such a characteristic partially explains why current Lagrangian stochastic models fail at reproducing our results. More generally, the Lagrangian dataset of residence times shown here represents another manner for qualifying the accuracy of models. We also deliver a theoretical approximation of mean residence times, which highlights the importance of the correlation between turbulence quantities and their time derivatives in setting temporal statistics. Finally, whether in a hole or a burst, the straining structure along particle trajectories always evolves self-similarly (in a statistical sense) from shearless two-dimensional to shear bi-axial configurations. We speculate that this latter configuration represents the optimum manner to dissipate locally the available energy

A first overview on genome-wide diversity of Italian donkey populations

Donkeys are widely reared animals, with more than 150 breeds worldwide. In spite of their vital economic importance, especially in developing countries, donkeys have received less attention than other livestock species. Analysis of genomic data is increas- ingly becoming part of the livestock sector and is an invaluable tool for the effective management of breeding programs in small populations, providing background information concerning genome structure in domestic animals. A scientific working group has recently been established to join efforts and resources for the genomic characterization of local Italian donkey populations. The main objective is to investigate the genomic structure of these important animal genetic resources, in order to provide information on their current conservation status which in turn will foster the management of the genetic variability. Biological samples from about 200 animals (20–30 per population) belong- ing to nine Italian donkey populations (Amiata, Asinara, Grigio Siciliano, Martina Franca, Pantesco, Ragusano, Romagnolo, Sardo and Viterbese) were collected for the analyses. Considered the absence of a specific beadchip array, we used double-digest restriction site associated DNA (ddRAD) sequencing to obtain approximately 50,000 single nucleotide polymorphisms (SNPs), and to overcome the limitations of previous studies based on microsatellite markers. The dataset will be analyzed to study sev- eral aspects of genetic diversity, such as relationships and gene flow, admixture and level of genomic inbreeding. In addition, a comparative analysis of conserved haplotypes will be conducted to identify selection signatures related to physiological processes of adaptation, resistance and milk production. The analysis of the data will pinpoint the genetic distinctiveness among Italian donkey populations. Moreover, the obtained results will contrib- ute to a better characterization of their history and genetic structure

Hadrontherapy: a Geant4-Based Tool for Proton/Ion-Therapy Studies

Hadrontherapy is a C++, free and open source application developed using the Geant4 Monte Carlo libraries The basic version of Hadrontherapy is contained in the official Geant4 distribution (wwwcernch/Geant4/download), inside the category of the advanced examples This version permits the simulation of a typical proton/ion transport beam line and the calculation of dose and fluence distributions inside a test phantom A more complete version of the program is separately maintained and released by the authors and it offers a wider set of tools useful for Users interested in proton/ion-therapy studies It gives the possibility to retrieve ion stopping powers in arbitrary geometrical configuration, to calculate 3D distributions of fluences, dose deposited and LET of primary and of the generated secondary beams, to simulate typical nuclear physics experiments, to interactively switch between different implemented geometries, etc In this work the main characteristics of the actual full version of Hadrontherapy will be reported and results discussed and compared with the available experimental data For more information the reader can refer to the Hadrontherapy website (author

Analysis of ddRAD-seq data provides new insights into the genomic structure and patterns of diversity in Italian donkey populations

Abstract With more than 150 recognized breeds, donkeys assume relevant economic importance, especially in developing countries. Even if the estimated number of heads worldwide is 53M, this species received less attention than other livestock species. Italy has traditionally been considered one of the cradles of European donkey breeding, and despite a considerable loss of biodiversity, today still counts nine autochthonous populations. A total of 220 animals belonging to nine different populations were genotyped using the double-digest restriction site associated DNA (ddRAD) sequencing to investigate the pattern of diversity using a multi-technique approach. A total of 418,602,730 reads were generated and successfully demultiplexed to obtain a medium-density SNP genotypes panel with about 27K markers. The diversity indices showed moderate levels of variability. The genetic distances and relationships, largely agree with the breeding history of the donkey populations under investigation. The results highlighted the separation of populations based on their genetic origin or geographical proximity between breeding areas, showed low to moderate levels of admixture, and indicated a clear genetic difference in some cases. For some breeds, the results also validate the success of proper management conservation plans. Identified runs of homozygosity islands, mapped within genomic regions related to immune response and local adaptation, are consistent with the characteristics of the species known for its rusticity and adaptability. This study is the first exhaustive genome-wide analysis of the diversity of Italian donkey populations. The results emphasized the high informativeness of genome-wide markers retrieved through the ddRAD approach. The findings take on great significance in designing and implementing conservation strategies. Standardized genotype arrays for donkey species would make it possible to combine worldwide datasets to provide further insights into the evolution of the genomic structure and origin of this important genetic resource