Design and manufacturing of anti-intrusion bars made of aluminium foam filled tubes

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH₂ blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed.     

Dysfunctional cGMP Signaling Leads to Age-Related Retinal Vascular Alterations and Astrocyte Remodeling in Mice

The nitric oxide–guanylyl cyclase-1–cyclic guanylate monophosphate (NO–GC-1–cGMP) pathway is integral to the control of vascular tone and morphology. Mice lacking the alpha catalytic domain of guanylate cyclase (GC1^−/−) develop retinal ganglion cell (RGC) degeneration with age, with only modest fluctuations in intraocular pressure (IOP). Increasing the bioavailability of cGMP in GC1^−/− mice prevents neurodegeneration independently of IOP, suggesting alternative mechanisms of retinal neurodegeneration. In continuation to these studies, we explored the hypothesis that dysfunctional cGMP signaling leads to changes in the neurovascular unit that may contribute to RGC degeneration. We assessed retinal vasculature and astrocyte morphology in young and aged GC1^−/− and wild type mice. GC1^−/− mice exhibit increased peripheral retinal vessel dilation and shorter retinal vessel branching with increasing age compared to Wt mice. Astrocyte cell morphology is aberrant, and glial fibrillary acidic protein (GFAP) density is increased in young and aged GC1^−/− mice, with areas of dense astrocyte matting around blood vessels. Our results suggest that proper cGMP signaling is essential to retinal vessel morphology with increasing age. Vascular changed are preceded by alterations in astrocyte morphology which may together contribute to retinal neurodegeneration and loss of visual acuity observed in GC1^−/− mice.     

Surface roughness analysis,modelling and prediction in selective laser melting

Selective Laser Melting (SLM) is an increasingly employed additive manufacturing process for the production of medical, aerospace, and automotive parts. Despite progresses in material flexibility and mechanical performances, relatively poor surface finish still presents a major limitation in the SLM process.In this study an investigation of surface roughness and morphology is presented for Steel 316L alloy parts made by SLM. In order to characterise the actual surfaces at different sloping angles, truncheon samples have been produced and an analysis has been conducted at different scales, by surface profilometer and scanning electron microscope (SEM). The surface analysis has showed an increasing density of spare particles positioned along the step edges, as the surface sloping angle increases. When layer thickness is comparable to particle diameter, the particles stuck along step edges can fill the gaps between consecutive layers, thus affecting the actual surface roughness.Classic models for roughness prediction, based on purely geometrical consideration of the stair step profile, fail to describe the observed trend of the experimental data. A new mathematical model is developed to include the presence of particles on top surfaces, in addition to the stair step effect, for the accurate prediction of surface roughness. Results show that surface roughness predicted by this model has a good agreement with the experimentally observed roughness. The paper investigates the key contributing factors influencing surface morphology, and a theoretical model for roughness prediction that provides valuable information to improve the surface quality of SLM parts, thus minimising the need of surface finishing.     

The influence of shared mental models on team process and performance.

The influence of teammates' shared mental models on team processes and performance was tested using 56 undergraduate dyads who "flew" a series of missions on a personal-computer-based flight-combat simulation. The authors both conceptually and empirically distinguished between teammates' task- and team-based mental models and indexed their convergence or "sharedness" using individually completed paired-comparisons matrices analyzed using a network-based algorithm. The results illustrated that both shared-team- and task-based mental models related positively to subsequent team process and performance. Furthermore, team processes fully mediated the relationship between mental model convergence and team effectiveness. Results are discussed in terms of the role of shared cognitions in team effectiveness and the applicability of different interventions designed to achieve such convergence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nutritional status in active juvenile chronic arthritis not treated with steroids

Nutritional status and nutrient intake were assessed in 17 children with active juvenile chronic arthritis (JCA) who never received steroids and in 17 controls matched for age and sex. Five patients had systemic, seven polyarticular and five oligoarticular JCA. Values significantly below those of the controls were found in systemic patients for height (p<0.05), upper arm circumference (p<0.05) and arm muscle area (p<0.01), and in polyarticular subjects for arm muscle area (p<0.01). All patients had unremarkable anthropometric fat measurements. All anthropometric measurements were normal in oligoarticular patients. Twelve JCA patients had reduced serum iron (Fe), 6 reduced serum zinc (SZn), 14 reduced intra-erythrocytic zinc (EZn) and 2 reduced serum copper (SCu). SZn was inversely correlated with erythrocyte sedimentation rate (ESR) (p=0.023). EZn was inversely related to lymphocyte count (p=0.022). SCu was related to ESR (p=0.037) and to lymphocyte count (p=0.016). No significant difference in nutrient intake was found between patients and controls. Active JCA was associated with reduced muscular mass, Fe, SZn, EZn. These alterations did not depend on reduced nutrient intake.     

The relation between methods of coping during adulthood with a history of childhood sexual abuse and current psychological adjustment.

With a community sample of 192 women who had been sexually abused during childhood, the investigators determined if methods of coping in adulthood with the aftermath of child sexual abuse were associated with current symptoms of psychological distress. Multiple regression analyses indicated that disengagement methods of coping with the sexual abuse accounted for unique variance in general psychological distress even after controlling for characteristics of the abuse and methods of coping with other stressors. Disengagement methods of coping were also used more often to deal with the stressful aspects of having been sexually abused than to deal with other stressful events. In contrast, engagement methods of coping were used more often to deal with the other stressors than with sexual abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modelling the increase in anisotropic reaction rates in metal nanoparticle oxidation using carbon nanotubes as thermal conduits

Nanostructured energetic materials are attracting attention for their faster reaction rates compared to materials with micron-scale particles. We numerically solve the coupled energy balances for a carbon nanotube with an annular coating of reactive metal, such that coupling to thermal transport in the nanotube accelerates reaction in the annulus. For the case of Zr metal, the nanotube increases the velocity of the reaction front in the direction of the nanotube length from 530 to 5100?mm?s(-1). This offers a proof-of-concept for one-dimensional anisotropic energetic materials, which could find new applications in inorganic synthesis and novel propellants. Nanotube conductivity as well as the relative sizes of the Zr annulus and the nanotube limit enhancement of the reaction velocity to a maximum of a factor of ～10. Interestingly, the interfacial heat conductance is not the most significant factor affecting the coupling, due to the large temperature differences (more than 1000?K) between the nanotube and the annulus at the reaction front and directional heat conduction in the nanotube. Although the enhancement is insufficient to change a Zr/nanotube composite from a deflagrating to a detonating material, using faster-reacting materials may enable nanotubes to effect this transition.     

High-resolution electrohydrodynamic jet printing

Efforts to adapt and extend graphic arts printing techniques for demanding device applications in electronics, biotechnology and microelectromechanical systems have grown rapidly in recent years. Here, we describe the use of electrohydrodynamically induced fluid flows through fine microcapillary nozzles for jet printing of patterns and functional devices with submicrometre resolution. Key aspects of the physics of this approach, which has some features in common with related but comparatively low-resolution techniques for graphic arts, are revealed through direct high-speed imaging of the droplet formation processes. Printing of complex patterns of inks, ranging from insulating and conducting polymers, to solution suspensions of silicon nanoparticles and rods, to single-walled carbon nanotubes, using integrated computer-controlled printer systems illustrates some of the capabilities. High-resolution printed metal interconnects, electrodes and probing pads for representative circuit patterns and functional transistors with critical dimensions as small as 1 mum demonstrate potential applications in printed electronics.