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In this work, TWBs with open cross sections are considered. At first they are viewed as an assembly of plates each one of them being a wall of the TWB. Each plate is then modeled as a Koiter shell, initially flat. This allows for using the two fundamental forms of the middle surface of the shell as strain measures. On the middle surface of each plate two local coordinates are introduced: we will call them longitudinal and transversal, respectively. It is assumed that the components of the displacement field which characterize the middle surface kinematics can be expressed as a product of two functions: one defined along the longitudinal coordinate and one defined along the transversal coordinate. Given an explicit expression of the latter functions the 2D plate fields are reduced to 1D ones. The functions of the transversal coordinate are chosen so that the stretch along it together with the membrane shear, vanish. It is worth noting that the linearization of these constraints leads to the well known Vlasov’s assumptions. The walls are assembled by imposing suitable boundary conditions on their longitudinal edges. This procedure gives rise to an hyperelastic 1D beam model in which at least the warping is taken into account. The main features of the model are shown by means of some simple applications

We present and discuss a method to infer non invasively information on the fiber architecture in real LV walls. The method post–processes the echocardiographic data acquired by three–dimensional Speckle Tracking Echocardiography (3DSTE) through a MatLab–based protocol, already presented, discussed and val- idated in [5]. Our results reveals the difference between the role of endocardial and epicardial principal strain lines, at the systolic peak, and set the bases for possible future investigations aimed to analyze the onset of specific cardiac diseases through noninvasive analysis of LV fiber architecture

The aim of the present work is to evaluate the acute toxic response of the crustacean Daphnia magna exposed to individual pharmaceuticals and mixtures. We tested fluoxetine, a selective serotonin reuptake inhibitor widely prescribed as antidepressant, and propranolol, a non selective β-adrenergic receptor-blocking agent used to treat hypertension. Acute immobilization tests were performed according to OECD 202 and ISO 6341 guidelines. Less than 24 h old daphnids were exposed for 48 h. Six replicate vessels with five individuals per vessel were tested at each treatment level. Single chemicals were first tested separately; estimated EC50 were 7.0 mg/L for propranolol and 7.8 mg/L for fluoexetine. Toxicity of binary mixtures was then assessed using a fixed ratio experimental design. Five concentrations (from 0.5 to 2 total toxic units) and 5 percentages of each substance in the mixture (0, 25, 50, 75 and 100%) were tested. The MixTox model was applied to analyze the experimental results. This tool evaluates if and how observed data deviates from the CA (Concentration Addition) or IA (independent Action) models, and tests if significantly better descriptions of the observed data can be achieved using a set of deviation functions. These functions allow a differentiation between synergism and antagonism, along with deviations based on the dose-level and chemical ratio dependency. The conceptual model of Concentration Addition was adopted in this study, as we assumed that the mixture effect mirrors the sum of the single substances for compounds having similar mode of action. This analysis showed a significant deviation from the CA model that indicated antagonism. Concentrations tested were much higher than those detected in the environment; however these results are to be considered as a first step in an ongoing project aimed at assessing chronic ecological effects of mixtures of pharmaceuticals.

The aim of the paper is to solve and discuss the representation problem of a special class of integrable distortion fields in fibred cylindrical bodies and to analyze the correspond- ing induced shape changes. We find and discuss the compatibility conditions, i.e. the conditions to be satisfied to get a pair compatible distortion/shape change, when different fields of fibers are assigned on the cylindrical body, through the specification of the fields of fiber angles.

Stone-masonry constructions never disappeared from the horizons of architecture, even if the relationship between stone and architecture has been definitely loosened by Modern Movement. For the most part, it is survived in minor architectures, local or vernacular; however, some international architects have expressed their creativity within the classical stone language, also in very recent times. Moreover, the more recent technological innovation of the reinforced stone by post-tensioned steel cables has produced structures and structural elements of unusual slenderness, proving that stone can be fruitfully used in large architectures. Scientific research has never stopped within the field of masonry mechanics, for it has been deeply involved in conservation and restoration of the cultural heritage and so it is ready to help the renaissance of stone architecture.

A non-simple continuum model is adopted to grossly describe the behaviour of elastic microcracked bodies. The constitutive relations, obtained using a multiscale modelling based on the hypotheses of the classical molecular theory of elasticity, allow taking into account the microscopic features of the material. Referring to a one-dimensional microcracked bar, the possibility of the continuum to reveal the presence of internal heterogeneities is investigated. © (2010) Trans Tech Publications.

We present two applications of a direct one-dimensional beam model suitable for describing the buckling of thin-walled structures. The first application considers the buckling of a compressed beam with an intermediate stiffener under various warping constraints. The second describes the buckling of a two-bar frame, known as a Roorda frame, loaded by a dead force at the joint. Various warping constraints at the bar ends are considered and the relevant buckling modes and loads are numerically evaluated. Numerical results are presented for both cases; some of these appear to be new.

We present a reduced–order heart model aimed to introduce a novel point of view in the interpretation of the pressure–volume loops. The novelty of the approach is based on the definition of active contraction as opposed to that of active stress. The consequences of such assumption are discussed with reference to a specific pressure-volume loop characteristic of a normal human patient.

A beam model aimed at describing the flexural-torsional buckling of thin-walled members with non-symmetric cross-sections is presented. Two beam axes are introduced, and strain is defined with respect to both. The shearing strain between the cross-section and one of the two axes is assumed to vanish; the warping is supposed to be linear in the twist. Non-linear hyperelastic constitutive relations are introduced; by means of standard localization and static perturbation techniques, the field equations describing the flexural-torsional buckling are obtained. One benchmark example is given and some numerical values of the critical load for various warping constraints at the beam ends are provided. (c) 2008 Elsevier Ltd. All rights reserved.

Si consideri un sistema costituito da blocchi collegati da giunti di spessore sottile, disposti in modo da costituire un ‘arco’ o una ‘piattabanda’ di altezza e larghezza costanti. I solidi ‘arco’ e ‘piattabanda’ abbiano un asse costituto da una curva regolare piana, e da un segmento di retta, rispettivamente. I giunti siano disposti con regolarità in modo da determinare una variazione regolare della forma dei blocchi. In una prima fase di modellazione si assume che i blocchi siano corpi rigidi e i giunti interfacce elastiche.Successivamente si introduce un modello di trave monodimensionale con sezioni rigide per descrivere sommariamente il comportamento meccanico dei sistemi a blocchi. Si considera innanzitutto una configurazione iniziale in cui l’asse della trave coincide con l’asse del solido ‘arco’ o ‘piattabanda’ e le sezioni sono disposte lungo questo seguendo l’assetto dei giunti. Nel caso dell’arco, le sezioni sono ortogonali alla linea d’asse mentre nel caso della piattabanda formano un angolo variabile con continuità. Il caso più generale è quello in cui l’asse è una linea curva e le sezioni non sono ad esso ortogonali. Postulando una relazione di equivalenza in potenza tra i processi dinamici del modello discreto e quelli della trave, per atti di moto test corrispondenti, si esprimono le azioni di contatto della trave in funzione di quelle nel discreto ( vedi Masiani et al. 1995 ). Assegnata quindi una relazione costitutiva per le azioni di contatto del modello discreto, si ricava la relazione corrispondente per la azioni interne della trave.Tramite la relazione costitutiva il modello continuo, pur se sommario, si rivela capace di tenere in conto aspetti legati alla disomogeneità del materiale e alla geometria dei blocchi.