1,721,066 research outputs found
Axial and flexional behaviour of elastic nano-beams by stress-driven two-phase elasticity
No full textSize-dependent structural behaviour of axially functionally graded nanobeams with non-uniform cross-section under axial and transversal loads is investigated by two-phase integral stress-driven elasticity. An effective nonlocal model is used by introducing a convex combination of the purely nonlocal integral stress-driven relation with a local phase. The stress-driven nonlocal model does not show ill-posedness behaviours such as the Eringen strain-driven model and leads to well-posed elastostatic nonlocal problems in all cases of technical interest. In particular, the integral convolution of the two-phase mixture is obtained by considering the bi-exponential kernel. A nanocantilever subject to an axial or a transversal force at the tip is considered. The nonlocal integral stress-driven model is solved and transversal and axial displacements are evaluated
Buckling loads of nano-beams in stress-driven nonlocal elasticity
No full textSize-dependent buckling of compressed Bernoulli-Euler nano-beams is investigated by stress-driven nonlocal continuum mechanics. The nonlocal elastic strain is obtained by convoluting the stress field with a suitable smoothing kernel. Incremental equilibrium equations are established by a standard perturbation technique. Higher-order constitutive boundary conditions are naturally inferred by the stress-driven nonlocal integral convolution, equipped with the special bi-exponential kernel. Buckling loads of compressed nano-beams, with kinematic boundary constraints of applicative interest, are numerically calculated and compared with those obtained by the theory of strain gradient elasticity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Environmental Impact on Immune System
No full textEnvironmental influences, either social or physical, can affect any aspect of human health, from disease onset (accumulating in their effects throughout life span) to disease progression and survival. There is evidence suggesting that behavior, nutrients, and pollutants are environmental factors altering the immune-metabolism response and affecting the relationship between the commensal microbiota and its human host, contributing to the increasing incidence of allergic and autoimmune diseases. This chapter focuses on presenting the key research findings describing the regulation of immune response and the crosstalk between the environment and the immune and the metabolic systems. We highlight human epidemiological data and animal studies that suggest that endocrine-disrupting chemicals’ (EDCs’) exposure can affect immune cells by acting on development, cellular, and humoral response. Finally, we examine the impact of nutritional status and microbiota on innate and adaptive immune response
On the regularity of curvature fields in stress-driven nonlocal elastic beams
No full textElastostatic problems of Bernoulli–Euler nanobeams, involving internal kinematic constraints and discontinuous and/or concentrated force systems, are investigated by the stress-driven nonlocal elasticity model. The field of elastic curvature is output by the convolution integral with a special averaging kernel and a piecewise smooth source field of elastic curvature, pointwise generated by the bending interaction. The total curvature is got by adding nonelastic curvatures due to thermal and/or electromagnetic effects and similar ones. It is shown that fields of elastic curvature, associated with piecewise smooth source fields and bi-exponential kernel, are continuously differentiable in the whole domain. The nonlocal elastic stress-driven integral law is then equivalent to a constitutive differential problem equipped with boundary and interface constitutive conditions expressing continuity of elastic curvature and its derivative. Effectiveness of the interface conditions is evidenced by the solution of an exemplar assemblage of beams subjected to discontinuous and concentrated loadings and to thermal curvatures, nonlocally associated with discontinuous thermal gradients. Analytical solutions of structural problems and their nonlocal-to-local limits are evaluated and commented upon
How food choices impact on male fertility
No full textPurpose of ReviewIncreasing evidence on the significance of nutrition in reproduction is emerging from both animal and human studies, suggesting an association between nutrition and male fertility. Here, we have highlighted the impact of the various food groups on reproductive hormones and on spermatogenesis, and the effects of classical and latest dietary patterns such as Mediterranean diet, Western diet, intermittent fasting, ketogenic diet, and vegan/vegetarian diet on male fertility.Recent FindingsNutrients are the precursors of molecules involved in various body's reactions; therefore, their balance is essential to ensure the correct regulation of different systems including the endocrine system. Hormones are strongly influenced by the nutritional status of the individual, and their alteration can lead to dysfunctions or diseases like infertility. In addition, nutrients affect sperm production and spermatogenesis, controlling sexual development, and maintaining secondary sexual characteristics and behaviors.SummaryThe consumption of fruit, vegetables, fish, processed meats, dairy products, sugars, alcohol, and caffeine importantly impact on male fertility. Among dietary patterns, the Mediterranean diet and the Western diet are most strongly associated with the quality of semen. Nutrients, dietary patterns, and hormonal levels have an impact on male infertility. Therefore, understanding how these factors interact with each other is important for strategies to improve male fertility
A consistent variational formulation of Bishop nonlocal rods
No full textThick rods are employed in nanotechnology to build modern electromechanical systems. Design and optimization of such structures can be carried out by nonlocal continuum mechanics which is computationally convenient when compared to atomistic strategies. Bishop’s kinematics is able to describe small-scale thick rods if a proper mathematical model of nonlocal elasticity is formulated to capture size effects. In all papers on the matter, nonlocal contributions are evaluated by replacing Eringen’s integral convolution with the consequent (but not equivalent) differential equation governed by Helmholtz’s differential operator. As notorious in integral equation theory, this replacement is possible for convolutions, defined in unbounded domains, governed by averaging kernels which are Green’s functions of differential operators. Indeed, Eringen himself, in order to study nonlocal problems defined in unbounded domains, such as screw dislocations and wave propagation, suggested to replace integro-differential equations with differential conditions. A different scenario appears in Bishop rod mechanics where nonlocal integral convolutions are defined in bounded structural domains, so that Eringen’s nonlocal differential equation has to be supplemented with additional boundary conditions. The objective is achieved by formulating the governing nonlocal equations by a proper variational statement. The new methodology provides an amendment of previous contributions in the literature and is illustrated by investigating the elastostatic behavior of simple structural schemes. Exact solutions of Bishop rods are evaluated in terms of nonlocal parameter and cross section gyration radius. Both hardening and softening structural responses are predictable with a suitable tuning of the parameters
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