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In the present work, we apply the asymptotic homogenization technique to the equations describing the dynamics of a heterogeneous material with evolving micro-structure, thereby obtaining a set of upscaled, effective equations. We consider the case in which the heterogeneous body comprises two hyperelastic materials and we assume that the evolution of their micro-structure occurs through the development of plastic-like distortions, the latter ones being accounted for by means of the Bilby–Kröner–Lee (BKL) decomposition. The asymptotic homogenization approach is applied simultaneously to the linear momentum balance law of the body and to the evolution law for the plastic-like distortions. Such evolution law models a stress-driven production of inelastic distortions, and stems from phenomenological observations done on cellular aggregates. The whole study is also framed within the limit of small elastic distortions, and provides a robust framework that can be readily generalized to growth and remodeling of nonlinear composites. Finally, we complete our theoretical model by performing numerical simulations

Effective properties of hierarchical fiber-reinforced composites via a three-scale asymptotic homogenization approach

The study of the properties of multiscale composites is of great interest in engineering and biology. Particularly, hierarchical composite structures can be found in nature and in engineering. During the past decades, the multiscale asymptotic homogenization technique has shown its potential in the description of such composites by taking advantage of their characteristics at the smaller scales, ciphered in the so-called effective coefficients. Here, we extend previous works by studying the in-plane and out-of-plane effective properties of hierarchical linear elastic solid composites via a three-scale asymptotic homogenization technique. In particular, the approach is adjusted for a multiscale composite with a square-symmetric arrangement of uniaxially aligned cylindrical fibers, and the formulae for computing its effective properties are provided. Finally, we show the potential of the proposed asymptotic homogenization procedure by modeling the effective properties of musculoskeletal mineralized tissues, and we compare the results with theoretical and experimental data for bone and tendon tissues

Effective governing equations for heterogenous porous media subject to inhomogeneous body forces

We derive a new homogenized model for heterogeneous porous media driven by inhomogeneous body forces. We assume that the fine scale, characterizing the heterogeneities in the medium, is larger than the pore scale, but nonetheless much smaller than the size of the material (the coarse scale). We decouple spatial variations and assume periodicity on the fine scale. Fine scale variations are formally reflected in a locally unbounded source for the arising system of partial differential equations. We apply the asymptotic homogenization technique to obtain a well-defined coarse scale Darcy-type model. The resulting problem is driven by an effective source which comprises both the coarse scale divergence of the average body force, and additional contributions which are to be computed solving a well-defined diffusion-type cell problem which is driven solely by fine scale variations of the given force. The present model can be used to predict the effect of externally applied magnetic (or electric) fields on ferrofluids (or electrolytes) flowing in porous media. This work can, in perspective, pave the way for investigations of the effect of applied forces on complex and heterogeneous hierarchical materials, such as systems of fractures or cancerous biological tissues

Homogenized out-of-plane shear response three-scale fiber-reinforced composites

In the present work we embrace a three scales asymptotic homogenization approach to investigate the effective behavior of hierarchical linear elastic composites reinforced by cylindrical, uniaxially aligned fibers and possessing a periodic structure at each hierarchical level of organization. We present our novel results assuming isotropy of the constituents and focusing on the effective out-of-plane shear modulus, which is computed exploiting the solution of the arising anti-plane problems. The latter are solved semi-analytically by means of complex variables and successfully benchmarked against the results obtained by finite elements. Our findings can pave the way for multiscale modeling of complex hierarchical materials (such as bone and tendons) at a negligible computational cost

Vigilancia y lucha antivectorial contra arbovirosis en una institución del nivel primario de atención

Introduction: arboviruses are viral diseases transmitted by mosquitoes with a high hygienic and sanitary impact, requiring adequate surveillance and vector control.Objective: to characterize the surveillance and anti-vector control of arboviruses in a primary health care institution.Methods: an observational, descriptive and cross-sectional study was carried out at Pedro Borras Astorga University Polyclinic in the city of Pinar del Río during the period April-August 2019. The variables included: vector infestation index, suspicion of arboviruses, human resources involved, results of surveillance and vector control, as well as educational activities on arboviruses. The results were presented in statistical tables and graphs, and comparisons were made with other studies reviewed in relation to this topic.Results: the highest rate of infestation was found in August (0,7), 98,9 % of the patients were suspected of having dengue fever and 56,8 % of the human resources were students involved in the anti vector control activity. A total of 33 288 patients were treated and 1 378 patients with symptoms of arboviruses were identified. The face-to-face technique prevailed (23 590) as an educational activity on arboviruses.Conclusions: low infestation indicators, efficient human resources in its control, satisfactory results in terms of the actions performed, as well as the development of educational activities on arboviruses were found. These characteristics showed the sustainability and entomological efficacy achieved in the institution, with repercussions on greater quality of life and protection of social and community health.Introducción: las arbovirosis son enfermedades virales transmitidas por mosquitos de elevado impacto higiénico-sanitario, requiriéndose de una adecuada vigilancia y lucha antivectorial.Objetivo: caracterizar la vigilancia y lucha antivectorial contra arbovirosis en una institución del nivel primario de atención.Método: se realizó un estudio observacional, descriptivo y transversal en el Policlínico Universitario "Pedro Borrás Astorga" de la ciudad Pinar del Río, durante el período abril- agosto del 2019. Las variables empleadas fueron: índice de infestación vectorial, sospecha de arbovirosis, recursos humanos participantes, resultados de vigilancia y lucha antivectorial, así como actividades educativas sobre arbovirosis. Los resultados fueron presentados en gráficos y tablas estadísticas realizándose comparaciones con otros estudios consultados al respecto.Resultados: el índice de infestación más alto se encontró en el mes de agosto (0,7), en el 98,9 % de los pacientes se sospechó presencia de dengue. Predominó la presencia de recursos humanos estudiantes (56,8 %) en la actividad de lucha antivectorial. Fueron tratados 33 288 pacientes y se identificó 1378 enfermos con sintomatología para arbovirosis. Predominó la técnica cara a cara (23 590) como actividad educativa sobre arbovirosis.Conclusiones: se encontraron indicadores de infestación bajos, recursos humanos eficientes en su control, resultados satisfactorios ante acciones desempeñadas, así como desarrollo de actividades educativas frente a las arbovirosis. Dichas características evidenciaron la sostenibilidad y eficacia entomológica alcanzadas en la institución, repercutiendo en mayor calidad de vida y protección a la salud socio comunitaria

Propuesta de intervención educativa sobre VIH/Sida para adolescentes de un consultorio médico

Introduction: although there has been progress in knowledge about HIV/AIDS, promoting adequate practices for its prevention in adolescents is a necessity.Objective: design a proposal for an educational intervention on HIV/AIDS for adolescents in a medical office.Method: a pedagogical study was carried out using the materialistic-dialectical method, in the medical office No-2 at Pedro Borrás Astorga University Polyclinic in the period from August to September 2019. The target group included 120 adolescents, 60 of them were chosen through simple random sampling¸ using different methods for the search and processing of information: theoretical, empirical and statistical (descriptive). An informed consent was obtained from the parents and tutors of the adolescents participating in the study.Results: 60% of the adolescents had insufficient knowledge concerning the general characteristics related to HIV/AIDS. A proposal for an educational intervention on HIV/AIDS was designed to enhance comprehensive training in adolescents through six topics through methodological guidelines.Conclusions: the proposal of an educational intervention on HIV/AIDS for adolescents from a medical office constitutes a way for comprehensive training and risk perception in adolescence. Its implementation favors the reduction of morbidity and mortality associated to this pandemic, as well as a solid aim related to knowledge for its adequate management, control and prevention.Introducción: si bien se ha adelantado en conocimientos sobre el VIH/Sida, promover prácticas adecuadas para su prevención en adolescentes constituye una necesidad.Objetivo: diseñar una propuesta de intervención educativa sobre VIH/Sida para adolescentes de un consultorio médico.Método: se realizó estudio de corte pedagógico rectorado por el método materialista- dialéctico en el consultorio médico 2 del Policlínico universitario “Pedro Borrás Astorga” en el período de agosto a septiembre del 2019. El universo fue de 120 adolescentes, siendo seleccionados 60 mediante muestreo aleatorio simple¸ empleándose diferentes métodos para la búsqueda y procesamiento de la información: teóricos, empíricos y estadístico (descriptiva). Se obtuvo el consentimiento de los tutores de aquellos adolescentes participantes en el estudio.Resultados: el 60 % de los adolescentes mostró insuficientes conocimientos sobre características generales relacionadas con el VIH/Sida. Se diseñó una propuesta de intervención educativa sobre VIH/Sida para potenciar la formación integral en adolescentes a través de seis temas con orientaciones metodológicas.Conclusiones: la propuesta de intervención educativa sobre VIH/Sida para adolescentes de un consultorio médico constituye una vía para la formación integral y percepción de riesgo en la adolescencia. Su implementación favorece la reducción de la morbimortalidad asociada a dicha pandemia, así como un sólido argumento en los conocimientos para su adecuado manejo, control y prevención

Three scales asymptotic homogenization and its application to layered hierarchical hard tissues

In the present work a novel multiple scales asymptotic homogenization approach is proposed to study the effective properties of hierarchical composites with periodic structure at different length scales. The method is exemplified by solving a linear elastic problem for a composite material with layered hierarchical structure. We recover classical results of two-scale and reiterated homogenization as particular cases of our formulation. The analytical effective coefficients for two phase layered composites with two structural levels of hierarchy are also derived. The method is finally applied to investigate the effective mechanical properties of a single osteon, revealing its practical applicability in the context of biomechanical and engineering applications

The influence of anisotropic growth and geometry on the stress of solid tumors

Solid stresses can affect tumor patho-physiology in at least two ways: directly, by compressing cancer and stromal cells, and indirectly, by deforming blood and lymphatic vessels. In this work, we model the tumor mass as a growing hyperelastic material. We enforce a multiplicative decomposition of the deformation gradient to study the role of anisotropic tumor growth on the evolution and spatial distribution of stresses. Specifically, we exploit radial symmetry and analyze the response of circumferential and radial stresses to (a) degree of anisotropy, (b) geometry of the tumor mass (cylindrical versus spherical shape), and (c) different tumor types (in terms of mechanical properties). According to our results, both radial and circumferential stresses are compressive in the tumor inner regions, whereas circumferential stresses are tensile at the periphery. Furthermore, we show that the growth rate is inversely correlated with the stresses’ magnitudes. These qualitative trends are consistent with experimental results. Our findings therefore elucidate the role of anisotropic growth on the tumor stress state. The potential of stress-alleviation strategies working together with anticancer therapies can result in better treatments

The role of malignant tissue on the thermal distribution of cancerous breast

The present work focuses on the integration of analytical and numerical strategies to investigate the thermal distribution of cancerous breasts. Coupled stationary bioheat transfer equations are considered for the glandular and heterogeneous tumor regions, which are characterized by different thermophysical properties. The cross-section of the cancerous breast is identified by a homogeneous glandular tissue that surrounds the heterogeneous tumor tissue, which is assumed to be a two-phase periodic composite with non-overlapping circular inclusions and a square lattice distribution, wherein the constituents exhibit isotropic thermal conductivity behavior. Asymptotic periodic homogenization method is used to find the effective properties in the heterogeneous region. The tissue effective thermal conductivities are computed analytically and then used in the homogenized model, which is solved numerically. Results are compared with appropriate experimental data reported in the literature. In particular, the tissue scale temperature profile agrees with experimental observations. Moreover, as a novelty result we find that the tumor volume fraction in the heterogeneous zone influences the breast surface temperature

Delamination influence on elastic properties of laminated composites

International audienceThe present work aims to predict the behavior of effective elastic properties for laminated composites, considering localized damage in the interface between two layers. In practical terms, the damage in the adhesion, which influences the effective elastic properties of a laminate, is evaluated like a delamination between adjacent layers. Thus, the effective properties of laminated composites with different delamination extensions are calculated via finite element method and two-scale asymptotic homogenization method. It is investigated how the properties of the laminated composites are affected by the delamination extension and the thickness of the interface between layers. It is possible to conclude that the effective coefficient values decrease as the damage extension increases due to the fact that the delamination area increases. Besides, for all effective coefficients, except the effective coefficients C * 12 , C * 13 , and C * 23 , in the case without delamination, the coefficients decrease as the adhesive region thickness increases, and almost all coefficients decrease for complete separation of the interface. Numerical and analytical results are compared in order to show the potentialities and limitations of the proposed approaches. Finally, a numerical approach is used to simulate a specific case, where the interface is considered a functionally graded material