A phenomenological cluster-based model of Ca2+ waves and oscillations for Inositol 1,4,5-trisphosphate receptor (IP3R) channels

Clusters of IP3 receptor channels in the membranes of the endoplasmic reticulum (ER) of many non-excitable cells release calcium ions in a cooperative manner giving rise to dynamical patterns such as Ca2+ puffs, waves, and oscillations that occur on multiple spatial and temporal scales. We introduce a minimal yet descriptive reaction-diffusion model of IP3 receptors for a saturating concentration of IP3 using a principled reduction of a detailed Markov chain description of individual channels. A dynamical systems analysis reveals the possibility of excitable, bistable and oscillatory dynamics of this model that correspond to three types of observed patterns of calcium release -- puffs, waves, and oscillations respectively. We explain the emergence of these patterns via a bifurcation analysis of a coupled two-cluster model, compute the phase diagram and quantify the speed of the waves and period of oscillations in terms of system parameters. We connect the termination of large-scale Ca2+ release events to IP3 unbinding or stochasticity.Comment: 18 pages, 10 figure

Elastic stabilisation of wrinkles in thin films by auxetic microstructure

Thin elastic sheets and membranes are known to wrinkle when they are stretched -- the associated physics is highly non-linear. The mechanics of thin films that exhibit unusual behavior upon stretching, when they possess auxetic structure, i.e. when their apparent Poisson's ratio is negative, is presented here. Wrinkling is now suppressed within the bulk of auxetic films when tensioned, whereas localized creases confined to the clamps, that decay away exponentially, appear. These edge wrinkles are characterized for their amplitude and wavelength experimentally, theoretically, and computationally, which show excellent agreement with expected trends. The scaling for amplitude, wavelength and decay rate upon film properties and tension is obtained using simple analyses based on kinematic mismatch resulting from lateral Poisson's expansion

Geometrical analysis of vibrations of functionally graded shell panels using the R-functions theory

An approach for investigation of geometrically nonlinear vibrations of functionally graded shallow shells and plates with complex planform is proposed. It combines the application of the R-functions theory (RFM), variational Ritz’s method, the procedure by Bubnov-Galerkin and Runge-Kutta method. The presented method is developed in the framework of the first–order shear deformation shallow shell theory (FSDT). Shell panels under consideration are made from a mixture of ceramics and metal. Power law of volume fraction distribution of materials through thickness is chosen. Investigation of nonlinear vibrations of functionally graded shallow shells and plates with arbitrary planform and different types of boundary conditions is carried out. Test problems and numerical results have been presented for one-mode approximation in time. Effect of volume fraction exponent, geometry of a shape and boundary conditions on the natural frequencies is brought out

Geometrical analysis of vibrations of functionally graded shell panels using the R-functions theory

An approach for investigation of geometrically nonlinear vibrations of functionally graded shallow shells and plates with complex planform is proposed. It combines the application of the R-functions theory (RFM), variational Ritz’s method, the procedure by Bubnov-Galerkin and Runge-Kutta method. The presented method is developed in the framework of the first–order shear deformation shallow shell theory (FSDT). Shell panels under consideration are made from a mixture of ceramics and metal. Power law of volume fraction distribution of materials through thickness is chosen. Investigation of nonlinear vibrations of functionally graded shallow shells and plates with arbitrary planform and different types of boundary conditions is carried out. Test problems and numerical results have been presented for one-mode approximation in time. Effect of volume fraction exponent, geometry of a shape and boundary conditions on the natural frequencies is brought out

Branched flows of flexural elastic waves in non-uniform cylindrical shells

Propagation of elastic waves along the axis of cylindrical shells is of great current interest due to their ubiquitous presence and technological importance. Geometric imperfections and spatial variations of properties are inevitable in such structures. Here we report the existence of branched flows of flexural waves in such waveguides. The location of high amplitude motion, away from the launch location, scales as a power law with respect to the variance and linearly with respect to the correlation length of the spatial variation in the bending stiffness. These scaling laws are then theoretically derived from the ray equations. Numerical integration of the ray equations also exhibit this behaviour-consistent with finite element numerical simulations as well as the theoretically derived scaling. There appears to be a universality for the exponents in the scaling with respect to similar observations in the past for other types of waves, as well as flexural and hence dispersive waves in elastic plates.Comment: 9 pages, 10 figures, supplementary information attached as separate fil

Mechanical characterisation of additively manufactured material having lattice microstructure

Many natural and engineered structures possess cellular and porous architecture. This paper is focused on the mechanical characterisation of additively manufactured lattice structures. The lattice consists of a stack of polylactic acid (PLA) filaments in a woodpile arrangement fabricated using a fused deposition modelling 3D printer. Some of the most promising applications of this 3D lattice material of this type include scaffolds for tissue engineering and the core for sandwich panels. While there is a significant body of work concerning the manufacture of such lattice materials, attempts to understand their mechanical properties are very limited. This paper brings together manufacturing with the need to understand the structure-property relationship for this class of materials. In order to understand the elastic response of the PLA-based lattice structures obtained from the fused deposition modelling process, single filaments manufactured using the same process were experimentally characterised first. The single PLA filaments were manufactured under different temperatures. These filaments were then characterised by using tensile testing. The stress-strain curves are presented. The variability of the measured results is discussed. The measured properties are then taken as input to a finite element model of the lattice material. This model uses simple one-dimensional elements in conjunction with a novel method achieving computational economy which precludes the use of fine meshes. Using this novel model, the apparent elastic modulus of lattice along the filaments has been obtained and is presented in this paper

Capsaicinoids Content of Some Indigenous Capsicum Varieties of Assam, India

Seven indigenous varieties of capsicum belonging to five different species available locally in Assam were collected and evaluated for capsaicinoids content with a view to assess their relative potency and/or hotness in order to ensure the functional as well as the nutritional quality of capsicum. These include Capsicum annum (Jati Jolokia), Capsicum baccatum (Ohm Jolokia), Capsicum chinense (Bhut Jolokia), Capsicum frutescens (Dhan Jolokia, Maam Jolokia, Totta Bias) and Capsicum pubescens (Bhikue Jolokia). The word Jolokia usually refers to the vernacular (Assamese) name of capsicum or chilli that is often used just after the particular local name of the capsicum variety as mentioned above by the local people of Assam. Results indicate that Bhut Jolokia (Capsicum chinense) and Dhan Jolokia (Capsicum frutescens) possess comparatively higher amount of capsaicinoids (>2%) than other varieties of capsicum. The capsaicinoids content of Bhut Jolokia (2.45%) was still higher than that of Dhan Jolokia (2.14%). Different varieties of capsicum with decreasing order of their capsaicinoids content are as follows: Bhut Jolokia (2.45%) > Dhan Jolokia (2.14%) > Maam Jolokia (1.38%) > Bhikue Jolokia (0.92) > Ohm Jolokia (0.67%) > Jati Jolokia (0.51%) > Totta bias (0.25%). It is very interesting that in addition to Bhut Jolokia, the hottest capsicum of the world, another potential and hot capsicum variety i.e., Dhan Jolokia has been evolved. However, our present study was an attempt to identify such potential and hot capsicum varieties available locally in Assam for the production of capsaicinoids at large in order to meet the increasing demand of capsicum or capsaicinoids in the global market. Furthermore, large scale cultivation and proper utilization of these indigenous capsicum varieties will help improve the agricultural economy of the state and the country as a whole. Keywords: indigenous, Bhut Jolokia, Dhan Jolokia, capsaicioids, climatic condition, capsaici

Development of an Open Source Framework to position and personalize Human Body Models

International audienceThe current manuscript reports on the development status of a software framework to scale (personalize) and position Human Body Models used in safety applications, i.e. the PIPER framework. The framework is both model and code agnostic and it was successfully used with Thums, GHBMC and the new PIPER scalable child model. Various transformation methods to scale or positioning were implemented in an interactive application. The software was released under the Open Source General Public License (GPL) version 2

Carta de una amiga á Maria Victoria Enriqueta, duquesa de Aota, reina electa de España

International audienceSpecifications of a Software Framework to Position and Personalise Human Body Model