Experimental Meningococcal Sepsis in Congenic Transgenic Mice Expressing Human Transferrin

Severe meningococcal sepsis is still of high morbidity and mortality. Its management may be improved by an experimental model allowing better understanding of its pathophysiology. We developed an animal model of meningococcal sepsis in transgenic BALB/c mice expressing human transferrin. We studied experimental meningococcal sepsis in congenic transgenic BALB/c mice expressing human transferrin by transcriptional profiling using microarray analysis of blood and brain samples. Genes encoding acute phase proteins, chemokines and cytokines constituted the largest strongly regulated groups. Dynamic bioluminescence imaging further showed high blood bacterial loads that were further enhanced after a primary viral infection by influenza A virus. Moreover, IL-1 receptor–associated kinase–3 (IRAK-3) was induced in infected mice. IRAK-3 is a negative regulator of Toll-dependant signaling and its induction may impair innate immunity and hence result in an immunocompromised state allowing bacterial survival and systemic spread during sepsis. This new approach should enable detailed analysis of the pathophysiology of meningococcal sepsis and its relationships with flu infection

Finite Element Analysis of Tunable Composite Tubes Reinforced with Auxetic Structures

A tubular composite structure that is built of two materials, characterized by different Young moduli, is analysed in this paper. The Young’s modulus of one of these materials can be controlled by external conditions e.g., magnetic or electric field, temperature etc. The geometry of the reinforcement is based on typical auxetic re-entrant honeycomb cellular structure. The influence of this external factor on the behaviour of the stretched tube is analysed in this paper. Also, the possibility of creating a tubular composite structure whose cross-section is either shrinking or expanding, while stretching the tube is presented

Thermoauxetic Behavior of Composite Structures

This paper presents a study of new two-dimensional composite structures with respect to their thermomechanical properties. The investigated structures are based on very well-known auxetic geometries—i.e., the anti-tetrachiral and re-entrant honeycomb—modified by additional linking elements, material which is highly sensitive to changes of temperature. The study shows that temperature can be used as a control parameter to tune the value of the effective Poisson’s ratio, which allows, in turn, changing its value from positive to negative, according to the temperature applied. The study shows that such thermoauxetic behavior applies both to composites with voids and those completely filled with material

Numerical analysis of the lower limb prosthesis subjected to various load conditions

This article presents the simulation of a prosthetic socket with an auxetic structure under typical loading cases. The designed model of prosthetic socket is dedicated to patients who have undergone transfemoral amputation and consists of four elements, among which can be distinguished an inner lining, a shock absorbing element, component with a honeycomb re-entrant structure, which has a negative Poisson's ratio an outer shell. The prosthetic socket was analysed by means of the finite element method. The simulations were used to evaluate the strength of the design and to check whether it is possible to avoid a problem of changing the circumference of the patient's stump, thanks to the use of an auxetic structure in the socket

An analysis of the auxetic cranioplasty implant

The following paper is a reflection on the advisability of using auxetic structures in medical devices. For this purpose, a model of a skull implant was designed. This implant could be used for cranioplasty of bone defects after neurosurgical procedures. The implant is made of a titanium alloy and has an auxetic "double arrow" structure. The behavior of the implant was investigated in two cases, under the influence of increased intracranial pressure and impact of an external force. The calculations were made with the finite element method implemented in the SolidWorks 2020 program. Moreover, the natural frequency of the structure was examined in the Comsol Multiphysics program

Computational Modelling of Structures with Non-Intuitive Behaviour

This paper presents a finite-element analysis of honeycomb and re-entrant honeycomb structures made of a two-phase composite material which is optimized with respect to selected parameters. It is shown that some distributions of each phase in the composite material result in the counter-intuitive mechanical behaviour of the structures. In particular, negative values of effective Poisson’s ratio, i.e., effective auxeticity, can be obtained for a hexagonal honeycomb, whereas re-entrant geometry can be characterized by positive values. Topology optimization by means of the method of moving asymptotes (MMA) and solid isotropic material with penalization (SIMP) was used to determine the materials’ distributions