86,866 research outputs found
The polarity of entry and release of Canine Coronavirus from epithelial cells
No full textCanine coronavirus (CCoV) is an enveloped, single-strand RNA virus belonging to the Alphacoronavirus genus in the Coronaviridae family Pratelli [1,2] Despite their labile nature, RNA viruses are able to rapidly adjust to negative pressures of immune system, generating novel strains that might have selective advantages over parental genomes.
Epithelial cells in the gastrointestinal tracts are the target of CCoVs infection. The apical face, exposed towards the intestinal lumen, and the basolateral face have different composition and the tight junctions with neighbouring cells separate the two faces preventing mixing of membrane components. The epithelial cell surface from which viruses are released conditions the development of virus pathogenesis. Entry and release of viruses from epithelial cells can occur through either domains as a result of the distribution of viral receptors. Polarized virus release influence viral spread: basolateral release allows the infection of underlying tissues leading to a systemic infection, and apical release can limit viral spread by preventing the infection of cells other than epithelial ones.
Recent study has highlighted a new pathogenetic characteristic of CCoV in vitro, which is able to infect epithelial cells from both apical and basolateral compartments, and even if with different titres, CCoV was released both in the apical and in the basolateral medium after infection. Consequently, the current view that CCoV infection is restricted to the intestine should be modified, arguing that the direction of release may be toward the blood stream inducing systemic infection
Elastic plastic analysis iterative solution
No full textThe step-by-step analysis of finite element elastic plastic structures subjected to an assigned (quasistatic) loading history, is considered; it identifies with the well-known sequence of linear complementarity problems. An iterative technique devoted to solve the relevant linear complementarity problem is presented. It is based on the recursive solution of a suitable linear complementarity problem, deduced from the relevant one and easier than it The procedure convergency is proved. Some noticing particular cases are examined. The physical meaning of the procedure is shown to be a plastic relaxation. The suitable numerical ranges for some check parameter values, to be utilized in the application stage, is provided
An optimal design of FE structures with limited ductility
No full textThe minimum volume design of elastic perfectly plastic FE structures subjected to quasi-static fixed and cyclic loads is searched in such a way that the structure remains into the elastic field in serviceability conditions, while it is subjected to alternating plasticity under very strong cyclic actions, incremental and instantaneous collapse being prevented.
In order to take into account the limited ductility of the material, suitable chosen limits on the plastic deformations related to the initial transient phase and/or to the subsequent steady-state phase are considered for the structure subjected to very strong cyclic actions.
A numerical application confirm the theoretical expectations: optimal designs turn out to be quite light, with stiffness and resistance suitable to completely preserve the structure integrity in serviceability conditions, and well as to avoid collapse and to allow a great amount of plastic dissipation production under the action of very strong cyclic loads, plastic deformations being always sufficiently small and remaining null in the entire cycle
An optimal design of elastic plastic structures with bounds on transient and steady-state plastic deformations
No full textA multicriterion design of steel frames with shakedown constraints
No full textThe minimum volume design of elastic perfectly plastic steel frames subjected to fixed and cyclic loads is searched in such a way that
the structure remains in elastic field in serviceability conditions, while it is subjected to alternating plasticity under very strong cyclic actions, incremental and instantaneous collapse being prevented.
The problem is faced on the grounds of a statical and a kinematical approach.
The Kuhn–Tucker conditions of the two problems prove that they are each one the dual of the other and provide useful pieces of information about the structural behaviour.
Numerical applications confirm the theoretical expectations: optimal designs turn out to be quite light, with stiffness and resistance
suitable to completely preserve the structure integrity in serviceability conditions, and suitable to avoid collapse and to allow a great
amount of plastic dissipation production under the action of very strong cyclic loads, plastic deformations being null in the cycle
Bounds on transient phase plastic deformations in optimal design of steel frames subjected to cyclic loads
No full textA minimum volume multicriterion design of
elastic perfectly plastic steel frames subjected to a combination of quasi-static fixed and cyclic loads, bounding the transient phase plastic deformations, is proposed. The
problem is formulated according to a plastic shakedown criterion, so that incremental and instantaneous collapse are certainly prevented when the frame is subjected to very strongly
amplified cyclic loads. The further condition that the structure must also behave elastically in serviceability conditions is imposed. Since the steady-state loading history is known it is possible to directly bound the steady-state plastic deformations.
By applying a suitable own bounding theorem, it is also possible to indirectly bound the transient plastic deformations, whichever the unknown transient real loading history is. A numerical application confirms the fundamental
role played by the transient phase plastic deformations both on the design as well as on the structural behaviour and the great performance of the proposed formulation
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