Laminated Beam Analysis by Polynomial, rigonometric, Exponential and Zig-Zag Theories

A number of refined beam theories are discussed in this paper. These theories were obtained by expanding the unknown displacement variables over the beam section axes by adopting Taylor's polynomials, trigonometric series, exponential, hyperbolic and zig-zag functions. The Finite Element method is used to derive governing equations in weak form. By using the Unified Formulation introduced by the first author, these equations are written in terms of a small number of fundamental nuclei, whose forms do not depend on the expansions used. The results from the different models considered are compared in terms of displacements, stress and degrees of freedom (DOFs). Mechanical tests for thick laminated beams are presented in order to evaluate the capability of the finite elements. They show that the use of various different functions can improve the performance of the higher-order theories by yielding satisfactory results with a low computational cost

Reduction of the mesh size influence on the results of a lagrangian finite element machining mode

Mesh dependence of the results of a finite element model are well known in many fields such as in structural design. This problem is however not much addressed in the literature for machining modelling although it is crucial for the quality of the results and the predictive aspect of the model. In this work, an orthogonal cutting model of the titanium alloy Ti6Al4V is exploited. The model formulation is Lagrangian and a damage criterion with eroding elements is used. A strong sensitivity of the results to the size of the elements is observed and the results do not converge when the size of the mesh decreases. To address this issue, a non-local damage criterion that reduces the mesh dependence of the results is introduced. The results show a strong decrease of their dependence to the size of the mesh. The recommendation is to use elements length that is not too far from the size of the grains of the material to avoid a dramatic increase of the computing time for very small elements and the absence of converged results for too large elements

Turbulent Diffusion of the Geomagnetic Field and Dynamo Theories

The thesis deals with the Dynamo Theories of the Earth’s Magnetic Field and mainly deepens the turbulence phenomena in the fluid Earth’s core. Indeed, we think that these phenomena are very important to understand the recent decay of the geomagnetic field. The thesis concerns also the dynamics of the outer core and some very rapid changes of the geomagnetic field observed in the Earth’s surface and some aspects regarding the (likely) isotropic turbulence in the Magnetohydrodynamics. These topics are related to the Dynamo Theories and could be useful to investigate the geomagnetic field trends

Structural and functional properties of plant mitochondrial F-ATP synthase

The mitochondrial F-ATP synthase is responsible for coupling the transmembrane proton gradient, generated through the inner membrane by the electron transport chain, to the synthesis of ATP. This enzyme shares a basic architecture with the prokaryotic and chloroplast ones, since it is composed of a catalytic head (F1), located in the mitochondrial matrix, a membrane-bound part (FO), together with a central and a peripheral stalk. In this review we compare the structural and functional properties of F-ATP synthase in plant mitochondria with those of yeast and mammals. We also present the physiological impact of the alteration of F-ATP synthase in plants, with a special regard to its involvement in cytoplasmic male sterility. Furthermore, we show the involvement of this enzyme in plant stress responses. Finally, we discuss the role of F-ATP synthase in shaping the curvature of the mitochondrial inner membrane and in permeability transition pore formation

Analysis of Composite Space Structures Subjected to Loading Factor

Reinforced structures are mandatory in the space structures on which the lightweight is the main project parameter. The coupling between simple thin-walled plate and different systems of ribs or beams along one or more directions make it possible to meet the requirements of lightness and strength. During the project phase a structure is usually analysed via Finite Element Method (FEM), where different approaches can be used but the pointed out one common essential characteristic, a mesh discretization of a continuous domain into a set of discrete subdomains, usually called elements. Three main finite elements (FEs) are widely used in the commercial code, but only the Solid (3D) FE represents more faithfully the behaviour of a real structure. The solid FE models require a large number of degrees of freedoms (DOFs) and therefore the analyses are computational expensive [1]. For these reason that usually the reduced models are used as substitute of solid models. The reduced models are made using shell (2D) and beam (1D) FEs, and they are suitable to build a reinforced structure, in fact the shell are used for the skin and the beam for the stringers. The present work uses a refined 1D model based on the Carrera Unified Formulation (CUF) [2] to analyse space structures made coupling skin and stringers. Thanks to its refined cinematic the present model can be used to represent both skin and stringers. The whole structure is obtained connecting simple one-dimensional structures using a new approach called Component-Wise (CW) [3]. This is possible because the unknowns are only displacements. Free-vibration analysis of isotropic and composite space structures with non-structural masses and loading factor are considered. A space vehicle is inspired to Arian 5 with a central body, on which the cryogenic fuel and the payload are accommodated, and two lateral boosters, on which solid fuel is stored. The results show the quasi-3D capabilities of the present 1D CUF model and the coupling with the CW approach provide accurate results nearest to solid FE results than the classical refined FEs models. In conclusion the present 1D refined model appears suitable for the analysis of reinforced thin-walled structures, it provides accurate results with the benefit to reduce the computational costs with respect to the classical refined FE approaches. References [1] E. Carrera, E. Zappino and T. Cavallo. Accurate free vibration analysis of launcher structures using refined 1D models. International Journal of Aeronautical and Space Sciences,vol. 16(2) 206-222, 2015. [2] E. Carrera, G. Giunta and M. Petrolo. Beam Structures: Classical and Advanced Theories. Jhon Wiley & Sons Ltd, 2011. [3] E. Carrera, A. Pagani and M. Petrolo. Component-wise Method Applied to Vibration of Wing Structures. J Appl Mech, vol. 80(4), 041012-1-041012-15, 2013

Caspase-3-like activity and proteasome degradation in grapevine suspension cell cultures undergoing silver-induced programmed cell death

Toxic metal contamination is one of the major environmental concerns of the recent decade, due to the large application of metals in industrial, healthcare and commercial products, even in the form of nanostructures and nanomaterials. Nevertheless, the effects of silver (Ag+) on plants have not yet thoroughly elucidated. Therefore, suspension cell cultures of grapevine were used as a model for investigating silver toxicity. To do this, oxidative stress and programmed cell death (PCD), evaluated as reactive oxygen species production, caspase-3-like activity and ubiquitin-proteasome system, were investigated. As a result, the highest concentration (10 \u3bcM) of Ag+ caused a rapid (within 24 h) induction of PCD (approx. 80%), accompanied by generation of reactive oxygen species and activation of caspase-3-like activity. In the presence of specific inhibitor of this enzyme, a partial recovery of cell viability and a strong inhibition of caspase- 3-like activity was observed. In addition, silver-induced PCD was accompanied either by increase of poly-ubiquitin conjugated proteins and degradation of subunit PBA1 of the proteasome 20S core, similarly to what found for metal-induced neurotoxicity in animals. The present study shows that silver could induce PCD in grapevine suspension cell cultures, mediated by caspase-3-like activity and oxidative stress. These effects were associated to accumulation of poly-ubiquitin conjugated proteins, suggesting the impairment of ubiquitin-proteasome complex, confirmed by the decrease of the PBA1 subunit. These findings indicate that animal and plant cells could share a common pathway in response to toxic metal, which involves PCD and disassembling of proteasome complex

Building for a Zero Carbon future: Trade-off between carbon dioxide emissions and primary energy approaches

Growing urbanization is driving urban policy makers to adopt sustainable practices aimed to limit the environmental impact of buildings which are responsible for an estimated 36% of climate-changing gas emissions in European cities. In order to meet the ambitious emission reduction targets set by the EU it is essential to develop policy for CO2 emissions saving. This work investigates the regulations of European countries that introduce carbon compliance requirement as implementation of the EPBD such as UK, Ireland, Austria and some Eastern European countries. With reference to the typical consumption pattern of an Italian home, the paper analyses the current limits of primary energy, RES requirements and CO2 emissions, investigating the relations between EPnren and carbon dioxide emissions levels