Low-velocity impact behaviour of fibreglass-aluminium laminates

Low-velocity impact tests were performed on fibreglass–aluminium composites made of 2024 T3 sheets and S2-glass/epoxy prepreg layers, using an instrumented falling weight machine. For comparison purposes, similar tests were carried out on monolithic 2024 T3 sheets of equivalent thickness. In the tests, the impact speed, mass, and energy were varied, to ascertain the influence of these parameters on the material response. From the results obtained, the overall force–displacement curve only depends on the impact energy, rather than on the mass and speed separately. Further, the energy required for penetration is higher for monolithic aluminium than for the fibreglass– aluminium. However, the latter material seems to offer better performance than carbon fibre- and glass fibre-reinforced laminates in terms of penetration energy, damage resistance, and inspectability. The main failure modes of fibreglass – aluminium were assessed by both ultrasonic C-scan and chemical grinding of aluminium sheets. It was found that the energy required for first failure is very low, whereas the energy level resulting in first fibre failure is similar to that inducing first cracking in the 2024 T3 sheets. From the experimental data, simple empirical relationships were found for the calculation of maximum contact force, energy, and residual displacement as a function of the maximum displacement

The Cauchy problem for the 3-D Vlasov-Poisson system with point charges

In this paper we establish global existence and uniqueness of the solution to the three-dimensional Vlasov-Poisson system in presence of point charges in case of repulsive interaction. The present analysis extends an analogeous two-dimensional result by Caprino and Marchioro [On the plasma-charge model, to appear in Kinetic and Related Models (2010)].Comment: 28 page

Friction in a Model of Hamiltonian Dynamics

We study the motion of a heavy tracer particle weakly coupled to a dense ideal Bose gas exhibiting Bose-Einstein condensation. In the so-called mean-field limit, the dynamics of this system approaches one determined by nonlinear Hamiltonian evolution equations describing a process of emission of Cerenkov radiation of sound waves into the Bose-Einstein condensate along the particle's trajectory. The emission of Cerenkov radiation results in a friction force with memory acting on the tracer particle and causing it to decelerate until it comes to rest.Comment: 53 Page

The relative absorption of fatty acids in brown trout (Salmo trutta) fed a commercial extruded pellet coated with different lipid sources

The objective of the present study was to investigate the fatty acid absorption capabilities of brown trout (Salmo trut- ta) fed commercial extruded diets. Five commercial extruded pellets, different only in the lipid sources used for fat coat- ing, were tested on juvenile brown trout for 45 days. The trout were reared in fresh water at 14.6 ± 0.4° C and 7.7 ± 0.3 mg/l, temperature and dissolved oxygen, respectively. The tested lipid sources were fish oil, canola oil, oleine oil, swine fat and poultry fat. After the adaptation period faeces were collected by gently stripping from anaesthetized fish. Fatty acid analysis was performed on experimental diets and on collected faeces to evaluate the relative absorption capabilities of the trout digestive system with respect to each detected fatty acid. The use of the relative absorption efficiency (rAE) was opted to evaluate the intrinsic capability of each fatty acid to be absorbed. Brown trout showed a specific preferential order of absorption of the fatty acids, preferring shorter over longer chain fatty acids and prefer- ring the more unsaturated to the more saturated fatty acids. The fatty acid that showed the best relative absorbability was the C18:4n-3 (rAE = 5.14 ± 0.72), which has a fairly short carbon chain, but at the same time a high unsatura- tion level, followed by the C18:3n-3 (rAE = 3.38 ± 0.30). The fatty acid that showed the worst relative absorbability (rAE = 0.21 ± 0.02) was C24:1n-9

Use of compositional analysis to distinguish farmed and wild gilthead seabream (Sparus aurata)

Recent food scares have emphasized the need for traceability in the food chain. This is particularly true in the fish sector, where a large difference in the final price between wild and farmed fish and even between farmed fish reared in different countries exists. So for these commercial and hygienic reasons it is very important to find useful tools for the characterization of quality of fish and for the differentiation of fish from different production methods and from different countries, in accordance with EC Regulation No. 2065/2001 and Italian Ministry of Agriculture Decree No. 27.03.02, that allow retail trade of fishery and aquaculture products only against the indication of the official commercial name, the method of production and the geographical origin of fish (Moretti et al., 2003)

Billiards in a general domain with random reflections

We study stochastic billiards on general tables: a particle moves according to its constant velocity inside some domain ${\mathcal D} \subset {\mathbb R}^d$ until it hits the boundary and bounces randomly inside according to some reflection law. We assume that the boundary of the domain is locally Lipschitz and almost everywhere continuously differentiable. The angle of the outgoing velocity with the inner normal vector has a specified, absolutely continuous density. We construct the discrete time and the continuous time processes recording the sequence of hitting points on the boundary and the pair location/velocity. We mainly focus on the case of bounded domains. Then, we prove exponential ergodicity of these two Markov processes, we study their invariant distribution and their normal (Gaussian) fluctuations. Of particular interest is the case of the cosine reflection law: the stationary distributions for the two processes are uniform in this case, the discrete time chain is reversible though the continuous time process is quasi-reversible. Also in this case, we give a natural construction of a chord "picked at random" in ${\mathcal D}$, and we study the angle of intersection of the process with a $(d-1)$-dimensional manifold contained in ${\mathcal D}$.Comment: 50 pages, 10 figures; To appear in: Archive for Rational Mechanics and Analysis; corrected Theorem 2.8 (induced chords in nonconvex subdomains

NUTRITIONAL, HYGIENIC, HEALTH AND ORGANOLEPTIC CHARACTERIZATION OF MEAT OF BOVINE BREED PIEMONTESE

The autochthonous "Piemontese" bovine breed is primarily raised for meat due to the high quality of production. The aim of this study was to investigate the microbiological, nutritional and chemical aspects of samples meat from cattle breeding "Piemontese"

Psychosocial assessment of families caring for a child with acute lymphoblastic leukemia, epilepsy or asthma: Psychosocial risk as network of interacting symptoms

The purpose of this study is to assess psychosocial risk across several pediatric medical conditions and test the hypothesis that different severe or chronic pediatric illnesses are characterized by disease specific enhanced psychosocial risk and that risk is driven by disease specific connectivity and interdependencies among various domains of psychosocial function using the Psychosocial Assessment Tool (PAT). In a multicenter prospective cohort study of 195 patients, aged 5-12, 90 diagnosed with acute lymphoblastic leukemia (ALL), 42 with epilepsy and 63 with asthma, parents completed the PAT2.0 or the PAT2.0 generic version. Multivariate analysis was performed with disease as factor and age as covariate. Graph theory and network analysis was employed to study the connectivity and interdependencies among subscales of the PAT while data-driven cluster analysis was used to test whether common patterns of risk exist among the various diseases. Using a network modelling approach analysis, we observed unique patterns of interconnected domains of psychosocial factors. Each pathology was characterized by different interdependencies among the most central and most connected domains. Furthermore, data-driven cluster analysis resulted in two clusters: patients with ALL (89%) mostly belonged to cluster 1, while patients with epilepsy and asthma belonged primarily to cluster 2 (83% and 82% respectively). In sum, implementing a network approach improves our comprehension concerning the character of the problems central to the development of psychosocial difficulties. Therapy directed at problems related to the most central domain(s) constitutes the more rational one because such an approach will inevitably carry over to other domains that depend on the more central function