Diffusive MIMO Molecular Communications: Channel Estimation, Equalization and Detection

In diffusion-based communication, as for molecular systems, the achievable data rate is low due to the stochastic nature of diffusion which exhibits a severe inter-symbol-interference (ISI). Multiple-Input Multiple-Output (MIMO) multiplexing improves the data rate at the expense of an inter-link interference (ILI). This paper investigates training-based channel estimation schemes for diffusive MIMO (D-MIMO) systems and corresponding equalization methods. Maximum likelihood and least-squares estimators of mean channel are derived, and the training sequence is designed to minimize the mean square error (MSE). Numerical validations in terms of MSE are compared with Cramer-Rao bound derived herein. Equalization is based on decision feedback equalizer (DFE) structure as this is effective in mitigating diffusive ISI/ILI. Zero-forcing, minimum MSE and least-squares criteria have been paired to DFE, and their performances are evaluated in terms of bit error probability. Since D-MIMO systems are severely affected by the ILI because of short transmitters inter-distance, D-MIMO time interleaving is exploited as countermeasure to mitigate the ILI with remarkable performance improvements. The feasibility of a block-type communication including training and data equalization is explored for D-MIMO, and system-level performances are numerically derived.Comment: Accepted paper at IEEE transaction on Communicatio

Field observations about the behaviour of codling-moth in Trentino (North-Eastern Italy)

Codling-moth and applescab are the most important pathogens in both conventional and organic apple productions. In order to control any phytopathological problem, it is important to improve the knowledge of the behaviour of each specific pest. Since several years (starting from 1986) we are improving in Trentino (North-Eastern Italy) the observations of the population dynamics of codling-moth in order to find the best way to control and treat this pest insect. Constant monitoring and the knowledge of the characteristics of the different compounds and possible methods to control the codling-moth (mating disruption, granulose virus and specific nematodes) represent the most important basis to organize an effective controlstrategy

Influence of Rough and Smooth Walls on Macroscale Flows in Tumblers

Walls in discrete element method simulations of granular flows are sometimes modeled as a closely packed monolayer of fixed particles, resulting in a rough wall rather than a geometrically smooth wall. An implicit assumption is that the resulting rough wall differs from a smooth wall only locally at the particle scale. Here we test this assumption by considering the impact of the wall roughness at the periphery of the flowing layer on the flow of monodisperse particles in a rotating spherical tumbler. We find that varying the wall roughness significantly alters average particle trajectories even far from the wall. Rough walls induce greater poleward axial drift of particles near the flowing layer surface, but decrease the curvature of the trajectories. Increasing the volume fill level in the tumbler has little effect on the axial drift for rough walls, but increases the drift while reducing curvature of the particle trajectories for smooth walls. The mechanism for these effects is related to the degree of local slip at the bounding wall, which alters the flowing layer thickness near the walls, affecting the particle trajectories even far from the walls near the equator of the tumbler. Thus, the proper choice of wall conditions is important in the accurate simulation of granular flows, even far from the bounding wall.Comment: 32 pages, 19 figures, regular article, accepted for publication in Physical Review E 200

Hypergraph-Based Analysis of Clustered Cooperative Beamforming with Application to Edge Caching

The evaluation of the performance of clustered cooperative beamforming in cellular networks generally requires the solution of complex non-convex optimization problems. In this letter, a framework based on a hypergraph formalism is proposed that enables the derivation of a performance characterization of clustered cooperative beamforming in terms of per-user degrees of freedom (DoF) via the efficient solution of a coloring problem. An emerging scenario in which clusters of cooperative base stations (BSs) arise is given by cellular networks with edge caching. In fact, clusters of BSs that share the same requested files can jointly beamform the corresponding encoded signals. Based on this observation, the proposed framework is applied to obtain quantitative insights into the optimal use of cache and backhaul resources in cellular systems with edge caching. Numerical examples are provided to illustrate the merits of the proposed framework.Comment: 10 pages, 5 figures, Submitte

Intersegmental Coordination in the Kinematics of Prehension Movements of Macaques

The most popular model to explain how prehensile movements are organized assumes that they comprise two "components", the reaching component encoding information regarding the object's spatial location and the grasping component encoding information on the object's intrinsic properties such as size and shape. Comparative kinematic studies on grasping behavior in the humans and in macaques have been carried out to investigate the similarities and differences existing across the two species. Although these studies seem to favor the hypothesis that macaques and humans share a number of kinematic features it remains unclear how the reaching and grasping components are coordinated during prehension movements in free-ranging macaque monkeys. Twelve hours of video footage was filmed of the monkeys as they snatched food items from one another (i.e., snatching) or collect them in the absence of competitors (i.e., unconstrained). The video samples were analyzed frame-by-frame using digitization techniques developed to perform two-dimensional post-hoc kinematic analyses of the two types of actions. The results indicate that only for the snatching condition when the reaching variability increased there was an increase in the amplitude of maximum grip aperture. Besides, the start of a break-point along the deceleration phase of the velocity profile correlated with the time at which maximum grip aperture occurred. These findings suggest that macaques can spatially and temporally couple the reaching and the grasping components when there is pressure to act quickly. They offer a substantial contribution to the debate about the nature of how prehensile actions are programmed

Slow axial drift in three-dimensional granular tumbler flow

Models of monodisperse particle flow in partially filled three-dimensional tumblers often assume that flow along the axis of rotation is negligible. We test this assumption, for spherical and double cone tumblers, using experiments and discrete element method simulations. Cross sections through the particle bed of a spherical tumbler show that, after a few rotations, a colored band of particles initially perpendicular to the axis of rotation deforms: particles near the surface drift toward the pole, while particles deeper in the flowing layer drift toward the equator. Tracking of mm-sized surface particles in tumblers with diameters of 8-14 cm shows particle axial displacements of one to two particle diameters, corresponding to axial drift that is 1-3% of the tumbler diameter, per pass through the flowing layer. The surface axial drift in both double cone and spherical tumblers is zero at the equator, increases moving away from the equator, and then decreases near the poles. Comparing results for the two tumbler geometries shows that wall slope causes axial drift, while drift speed increases with equatorial diameter. The dependence of axial drift on axial position for each tumbler geometry is similar when both are normalized by their respective maximum values

The inelastic Takahashi hard-rod gas

We study a one-dimensional fluid of hard-rods interacting each other via binary inelastic collisions and a short ranged square-well potential. Upon tuning the depth and the sign of the well, we investigate the interplay between dissipation and cohesive or repulsive forces. Molecular dynamics simulations of the cooling regime indicate that the presence of this simple interparticle interaction is sufficient to significantly modify the energy dissipation rates expected by the Haff's law for the free cooling. The simplicity of the model makes it amenable to an analytical approach based on the Boltzmann-Enskog transport equation which allows deriving the behaviour of the granular temperature. Furthermore, in the elastic limit, the model can be solved exactly to provide a full thermodynamic description. A meaningful theoretical approximation explaining the properties of the inelastic system in interaction with a thermal bath can be directly extrapolated from the properties of the corresponding elastic system, upon a proper re-definition of the relevant observables. Simulation results both in the cooling and driven regime can be fairly interpreted according to our theoretical approach and compare rather well to our predictions.Comment: 14 pages RevTex, 9 eps figure

Optical properties of refractory metal based thin films

There is a growing interest in refractory metal thin films for a range of emerging nanophotonic applications including high temperature plasmonic structures and infrared superconducting single photon detectors. We present a detailed comparison of optical properties for key representative materials in this class (NbN, NbTiN, TiN and MoSi) with texture varying from crystalline to amorphous. NbN, NbTiN and MoSi have been grown in an ultra-high vacuum sputter deposition system. Two different techniques (sputtering and atomic layer deposition) have been employed to deposit TiN. We have carried out variable angle ellipsometric measurements of optical properties from ultraviolet to mid infrared wavelengths. We compare with high resolution transmission electron microscopy analysis of microstructure. Sputter deposited TiN and MoSi have shown the highest optical absorption in the infrared wavelengths relative to NbN, NbTiN or ALD deposited TiN. We have also modelled the performance of a semi-infinite metal air interface as a plasmonic structure with the above mentioned refractory metal based thin films as the plasmonic components. This study has implications in the design of next generation superconducting nanowire single photon detector or plasmonic nanostructure based devices

Le piante vascolari del litorale trapanese: da Ronciglio a Capo San Vito

Vascular flora of the Trapani littoral between Ronciglio and Capo San Vito (NW Sicily). – The list of the vascular plants observed and collected in the Trapani littoral between Ronciglio and Capo San Vito (NW Sicily) during the last 20 years is presented here and commented. In total, 541 specific and infraspecific taxa were recorded. This flora has marked Mediterranean characteristics as shown by the absolute prevalence of therophytes as well as Mediterranean chorotypes. Among the most interesting taxa belonging to this flora are some halophytes and rare endemics such as Biscutella maritima, Calendula maritima, Cynomorium coccineum, Erica sicula, Galium litorale, Halocnemum strobilaceum, Limonium bocco- nei, L. ponzoi, Limoniastrum monopetalum e Pseudoscabiosa limonifolia