Assessment of coupled bilayer-cytoskeleton modelling strategy for red blood cell dynamics in flow

The red blood cell (RBC) membrane is composed of a lipid bilayer and a cytoskeleton interconnected by protein junction complexes, allowing for potential sliding between the lipid bilayer and the cytoskeleton. Despite this biological reality, it is most often modelled as a single-layer model, a hyperelastic capsule or a fluid vesicle. Another approach involves incorporating the membrane's composite structure using double layers, where one layer represents the lipid bilayer and the other represents the cytoskeleton. In this paper, we computationally assess the various modelling strategies by analysing RBC behaviour in extensional flow and four distinct regimes that simulate RBC dynamics in shear flow. The proposed double-layer strategies, such as the vesicle-capsule and capsule-capsule models, account for the fluidity and surface incompressibility of the lipid bilayer in different ways. Our findings demonstrate that introducing sliding between the layers offers the cytoskeleton a considerable degree of freedom to alleviate its elastic stresses, resulting in a significant increase in RBC elongation. Surprisingly, our study reveals that the membrane modelling strategy for RBCs holds greater importance than the choice of the cytoskeleton's reference shape. These results highlight the inadequacy of considering mechanical properties alone and emphasise the need for careful integration of these properties. Furthermore, our findings fortuitously uncover a novel indicator for determining the appropriate stress-free shape of the cytoskeleton.Comment: accepted for publication in Journal of Fluid Mechanic

Micro-EDM process modeling and machining approaches for minimum tool electrode wear for fabrication of biocompatible micro-components

Micro-electrical discharge machining (micro-EDM) is a potential non-contact method for fabrication of biocompatible micro devices. This paper presents an attempt to model the tool electrode wear in micro-EDM process using multiple linear regression analysis (MLRA) and artificial neural networks (ANN).The governing micro-EDM factors chosen for this investigation were: voltage (V), current (I), pulse on time (Ton) and pulse frequency (f). The proposed predictive models generate a functional correlation between the tool electrode wear rate (TWR) and the governing micro-EDM factors. A multiple linear regression model was developed for prediction of TWR in ten steps at a significance level of 90%. The optimum architecture of the ANN was obtained with 7 hidden layers at an R-sq value of 0.98. The predicted values of TWR using ANN matched well with the practically measured and calculated values of TWR. Based on the proposed soft computing-based approach towards biocompatible micro device fabrication, a condition for the minimum tool electrode wear rate (TWR) was achieved

Cultural Identity and Aesthetics in Indian Folk Dance Thidambu Nritham: A Performance Outlook

Thidambu Nritham is an ancient Indian folk dance performed in villages of North Malabar in Kerala state. The performance follows several rules of Natya shastra, and at the same time, has influenced the cultural and social life of Malabar due to the ritualistic nature. According to the background and history, Kolathiri dynasty has introduced Thidambu Nritham as a part of temple rituals, the art form being seven-century old. Thidambu Nritham is deep-rooted in the civilization of north Kerala, as it has close links with agrarian culture and harvests in the region. The elements used for rituals and ceremonies in Thidambu Nritham connect with soil fertility and prayers for an enhanced crop yield. The aesthetics of Thidambu Nritham is related to the colourful decorations of thidambu using flowers and drumming in four rhythms. The culture of temple procession and worshippers joining the celebration could be traced from the prehistoric Indian tradition and heritage

Investigations into Performance of Dry EDM Using Slotted Electrodes

Dry EDM is an emerging EDM technology, which uses gas as dielectric fluid. Due to low density of gaseous dielectric, the process experiences i) unconstrained plasma expansion thereby reducing the effective material removal rate (MRR) and ii) inefficient disposal of debris. This work proposes use of electrodes with peripheral slots to provide more space for the flow of dielectric for effective debris disposal and consequently improve MRR. In this regard, a comprehensive experimentation using Taguchi L(16) orthogonal array has been planned initially to optimize the number of peripheral slots on the electrodes, and then to understand the effect of the slots on material removal, tool wear, oversize and depth achieved as a function of processing conditions. It is observed that the optimum number of peripheral slots on electrode for effective debris evacuation is four for the electrode configuration used in this work. The statistical analysis shows that in dry EDM, discharge current (I), gap voltage (V), rotational speed (N) and pulse off-time (T(off)) control MRR. Also, use of slotted electrodes significantly reduces the electrode wear rate, and attachment of debris particles on the electrodes

Quantitative assessment of lipid bilayer-cytoskeleton coupling in red blood cell membrane

International audienc

Is red blood cell a simple capsule?

Like other cells, the red blood cell membrane is composed of a lipid bilayer and a cytoskeleton, connected by protein junction complexes, with possible sliding. Despite this biological reality, it is most often modelled as a one-layer capsule or as a vesicle. An alternative is to consider a two-layers membrane, each mimicking either the lipid bilayer or the cytoskeleton. The in-plane elastic part brought by the cytoskeleton is modelled by a continuous constitutive law (capsule) or a discrete spring network. Considering four regimes representing the dynamics in shear flow, we computationally asses all the strategies with couplings such as capsule-capsule or capsule-network and vesicle-capsule or vesicle-network. The anisotropy artificially introduced by a discrete spring network is a source of numerical instability, especially for the coupling with a vesicle. Though the capsule-capsule and vesicle-capsule models show similarity in behaviour, considering fluidity and surface incompressibility when using a vesicle to represent the bilayer is not without consequences. Rigorous area conservation provides noticeable additional stiffness and fluidity allows lipid recirculation. Overall, our results suggest that modelling the membrane closer to the biological reality is more impactful than the largely debated issue about the stress-free shape for the cytoskeleton. Now, our results when comparing the capsule and the capsule-capsule models in tank-treading regime providentially highlight a new indicator of the right stress-free shape motivating new experimental investigations

Is red blood cell a simple capsule?

Like other cells, the red blood cell membrane is composed of a lipid bilayer and a cytoskeleton, connected by protein junction complexes, with possible sliding. Despite this biological reality, it is most often modelled as a one-layer capsule or as a vesicle. An alternative is to consider a two-layers membrane, each mimicking either the lipid bilayer or the cytoskeleton. The in-plane elastic part brought by the cytoskeleton is modelled by a continuous constitutive law (capsule) or a discrete spring network. Considering four regimes representing the dynamics in shear flow, we computationally asses all the strategies with couplings such as capsule-capsule or capsule-network and vesicle-capsule or vesicle-network. The anisotropy artificially introduced by a discrete spring network is a source of numerical instability, especially for the coupling with a vesicle. Though the capsule-capsule and vesicle-capsule models show similarity in behaviour, considering fluidity and surface incompressibility when using a vesicle to represent the bilayer is not without consequences. Rigorous area conservation provides noticeable additional stiffness and fluidity allows lipid recirculation. Overall, our results suggest that modelling the membrane closer to the biological reality is more impactful than the largely debated issue about the stress-free shape for the cytoskeleton. Now, our results when comparing the capsule and the capsule-capsule models in tank-treading regime providentially highlight a new indicator of the right stress-free shape motivating new experimental investigations

Is red blood cell a simple capsule?

Like other cells, the red blood cell membrane is composed of a lipid bilayer and a cytoskeleton, connected by protein junction complexes, with possible sliding. Despite this biological reality, it is most often modelled as a one-layer capsule or as a vesicle. An alternative is to consider a two-layers membrane, each mimicking either the lipid bilayer or the cytoskeleton. The in-plane elastic part brought by the cytoskeleton is modelled by a continuous constitutive law (capsule) or a discrete spring network. Considering four regimes representing the dynamics in shear flow, we computationally asses all the strategies with couplings such as capsule-capsule or capsule-network and vesicle-capsule or vesicle-network. The anisotropy artificially introduced by a discrete spring network is a source of numerical instability, especially for the coupling with a vesicle. Though the capsule-capsule and vesicle-capsule models show similarity in behaviour, considering fluidity and surface incompressibility when using a vesicle to represent the bilayer is not without consequences. Rigorous area conservation provides noticeable additional stiffness and fluidity allows lipid recirculation. Overall, our results suggest that modelling the membrane closer to the biological reality is more impactful than the largely debated issue about the stress-free shape for the cytoskeleton. Now, our results when comparing the capsule and the capsule-capsule models in tank-treading regime providentially highlight a new indicator of the right stress-free shape motivating new experimental investigations