We derive a sufficient condition by means of which one can recover a scale-limited signal from the knowledge of a truncated version of it in a stable manner following the canvas introduced by Donoho and Stark (1989) [4]. The proof follows from simple computations involving the Zak transform, well-known in solid-state physics. Geometric harmonics (in the terminology of Coifman and Lafon (2006) [22]) for scale-limited subspaces of L2(R) are also displayed for several test-cases. Finally, some algorithms are studied for the treatment of zero-angle problems.

An original well-balanced (WB) Godunov scheme relying on an exact Riemann solver involving a non-conservative (NC) product is developed. It is meant to solve accurately the time-dependent one-dimensional radiative transfer equation in the discrete ordinates approximation with an arbitrary even number of velocities. The collision term is thus concentrated onto a discrete lattice by means of Dirac masses; this induces steady contact discontinuities which are integral curves of the stationary problem. One solves it by taking advantage of the method of elementary solutions mainly developed by Case, Zweifel and Cercignani. This approach produces a rather simple scheme that compares advantageously to standard existing upwind schemes, especially for the decay in time toward a Maxwellian distribution. It is possible to reformulate this scheme in order to handle properly the parabolic scaling in order to generate a so-called asymptotic-preserving (AP) discretization. Consistency with the diffusive approximation holds independently of the computational grid. Several numerical results are displayed to show the realizability and the efficiency of the method.

We present a mesoscopic lattice model for non-ideal fluid flows with directional interactions, mimicking the effects of hydrogen bonds in water. The model supports a rich and complex structural dynamics of the orientational order parameter, and exhibits the formation of disordered domains whose size and shape depend on the relative strength of directional order and thermal diffusivity. By letting the directional forces carry an inverse density dependence, the model is able to display a correlation between ordered domains and low density regions, reflecting the idea of water as a denser liquid in the disordered state than in the ordered one.

Knowledge of the exact spatial distribution of brain tissues in images acquired by magnetic resonance imaging (MRI) is necessary to measure and compare the performance of segmentation algorithms. Currently available physical phantoms do not satisfy this requirement. State-of-the-art digital brain phantoms also fall short because they do not handle separately anatomical structures (e.g. basal ganglia) and provide relatively rough simulations of tissue fine structure and inhomogeneity. We present a software procedure for the construction of a realistic MRI digital brain phantom. The phantom consists of hydrogen nuclear magnetic resonance spin-lattice relaxation rate (R1), spin-spin relaxation rate (R2), and proton density (PD) values for a 24 x 19 x 15.5 cm volume of a ''normal'' head. The phantom includes 17 normal tissues, each characterized by both mean value and variations in R1, R2, and PD. In addition, an optional tissue class for multiple sclerosis (MS) lesions is simulated. The phantom was used to create realistic magnetic resonance (MR) images of the brain using simulated conventional spin-echo (CSE) and fast field-echo (FFE) sequences. Results of mono-parametric segmentation of simulations of sequences with different noise and slice thickness are presented as an example of possible applications of the phantom. The phantom data and simulated images are available online at http://lab.ibb.cnr.it/.

Soil N2O emissions were monitored throughout a 3-year crop rotation including maize, fennel and a ryegrass-clover. sward, at Borgo Cioffi NitroEurope site. N2O emission rates were highly variable in time and space and controlled by soil nitrogen and soil water content. The N2O effluxes were low for most of the monitored period. The highest N2O emissions were recorded throughout the 2007 maize cropping season, ranged from 15.2 to 196.2 mug m-2 h-1 whereas the lowest ones ranged from -5 to 10 mug m-2 h-1 during the 2007 2008 ryegrass-clover winter crop. For the maize crops, N2O peaks were detected after fertilization but with a delay of some weeks from applications, probably due to the presence of DMPP nitrification inhibitor in the applied fertilizer. A properly designed ANOVA model was developed to explain the influence of the main chemical-physical factors. This model also allowed the quantification of the delay time in peak emissions following fertilization, which resulted variable over the years and ranged between 2 and 21 days. A dependence of emissions from soil temperature and moisture was found, with significant interactions in some instances. Calculated Emission Factors (maize 2007: 0.48%; ryegrass-clover sward 2007 2008: 0.05%; maize 2008: 0.14%; fennel: 0.28% 2008 2009; maize 2009: .015%) resulted well below the values reported in the literature and the 1% reference value indicated by IPCC, probably due to a suboptimal water regime inducing low Water Filled Pore Space (WFPS) values.

Space-time patterns of wall shear stress (WSS) resulting from the numerical simulation of pulsating hemodynamic flows in semicoronal domains are analyzed, in the case of both regular semicoronal domains and semicoronal domains with bumpy insertions, mimicking aneurysm-like geometries. A new family of cardiovascular risk indicators, which we name three-band diagrams (TBDs), are introduced, as a sensible generalization of the two standard indicators, i.e., the time-averaged WSS and the oscillatory shear index. TBDs provide a handy access to additional information contained in the dynamic structure of the WSS signal as a function of the physiological risk threshold, thereby allowing a quick visual assessment of the risk sensitivity to individual fluctuations of the physiological risk thresholds. Due to its generality, TBD analysis is expected to prove useful for a wide host of applications in science, engineering, and medicine, where risk assessment plays a central role. © 2011 American Physical Society.

The interest in polynucleotide translocation through nanopores has moved from purely biological to the need of realizing nanobiotechnological applications related to personalized genome sequencing. Polynucleotide translocation is a process in which biomolecules, like DNA or RNA, are electrophoretically driven through a narrow pore and their passage can be monitored by the change in the ionic current through the pore. Such a translocation process, which will be described here offers a very promising technology aiming at ultra-fast low-cost sequencing of DNA, though its realization is still confronted with challenges and drawbacks. In this review, we present the main aspects involved in the polynucleotide translocation through solid-state nanopores by discussing the most relevant experimental, theoretical, and computational approaches and the way these can supplement each other. The discussion will expose the goals that have been reached so far, the open questions, and contains an outlook to the future of nanopore sequencing.

The turning circle manoeuvre of a self-propelled tanker like ship model is numerically simulated through the integration of the unsteady Reynolds Averaged Navier-Stokes (URANS) equations coupled with the equations of the motion of a rigid body. The solution is achieved by means of the unsteady RANS solver developed at CNR-INSEAN. The model is considered with two different stern appendages configurations (each one providing a different dynamic behaviour): twin screw with a single rudder and twin screw, twin rudder with a central skeg. Each propeller is taken into account by a model based on the actuator disk concept; anyhow, in order to correctly capture the turning manoeuvring behaviour of the model, a suitable description of the propeller performance in oblique flow operation has be considered. Comparison with experimental data from free running tests will demonstrate the feasibility of the CFD computations. The main features of the flow field, with particular attention to the vortical structures detached from the hull is presented as well.

The problem of ship manoeuvrability has reached nowadays a significant consideration, both for merchant ships, with the adoption of IMO standards, and naval ships, with the production of various documents by NATO Specialist Teams. In literature many works regarding manoeuvrability of single screw slow/medium speed ships are present, while a lack of information about twin screw ships (cruise ships, RoRo ferries, megayachts, naval vessels) exists. These ships are usually characterised by different hull forms and more complex stern configuration due to the presence of appendages like skegs, shaft lines and brackets, which can strongly affect manoeuvrability behaviour. In this work various prediction methods, namely statistical regressions, system identification and RANSE, have been investigated in order to evaluate twin screw naval vessels manoeuvrability behaviour. From this analysis stern appendages influence (including also non linear effects resulting from hull-appendages interactions) resulted one of the peculiar characteristics of this type of ships, clearly affecting their manoeuvring capabilities