Ramarathnam Krishna Kumar

Bio: Ramarathnam Krishna Kumar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Aortic valve & Randomized controlled trial. The author has an hindex of 5, co-authored 10 publications receiving 243 citations.

Transient Finite Element Analysis of Tire Dynamic Behavior

Abstract: Dynamic behavior of a pneumatic tire is simulated by use of an explicit finite element (FE) code. Different parts of the tire and their corresponding material properties are taken into account in the FE model because they play a significant role in tire dynamics. The work presented in this study discusses simulation of cornering behavior, braking behavior, and combined cornering‐cum‐braking behavior. The effects of camber angle and grooved tread on tire cornering behavior are discussed. ABAQUS/Explicit, a general non‐linear FE code, was used for these simulations. To predict the Magic Formula characteristics over a complete range, various simulations are performed at different normal loads and operating conditions. Predicted Magic Formula curves from the simulation results for various dynamic conditions closely follow the experimental data curves. Even though these simulations demand huge computational resources, the predicted Magic Formula curves can be directly used as input in the complete stu...

An open label randomized clinical trial of Indomethacin for mild and moderate hospitalised Covid-19 patients

Abstract: Indomethacin, a non-steroidal anti-inflammatory drug (NSAID), has been presented as a broad-spectrum antiviral agent. This randomised clinical trial in a hospital setting evaluated the efficacy and safety of this drug in RT-PCR-positive coronavirus disease 2019 (COVID-19) patients. A total of 210 RT-PCR-positive COVID-19 patients who provided consent were allotted to the control or case arm, based on block randomisation. The control arm received standard of care comprising paracetamol, ivermectin, and other adjuvant therapies. The patients in the case arm received indomethacin instead of paracetamol, with other medications retained. The primary endpoint was the development of hypoxia/desaturation with SpO2 ≤ 93, while time to become afebrile and time for cough and myalgia resolution were the secondary endpoints. The results of 210 patients were available, with 103 and 107 patients in the indomethacin and paracetamol arms, respectively. We monitored patient profiles along with everyday clinical parameters. In addition, blood chemistry at the time of admission and discharge was assessed. As no one in either of the arms required high-flow oxygen, desaturation with a SpO2 level of 93 and below was the vital goal. In the indomethacin group, none of the 103 patients developed desaturation. On the other hand, 20 of the 107 patients in the paracetamol arm developed desaturation. Patients who received indomethacin also experienced more rapid symptomatic relief than those in the paracetamol arm, with most symptoms disappearing in half the time. In addition, 56 out of 107 in the paracetamol arm had fever on the seventh day, while no patient in the indomethacin group had fever. Neither arm reported any adverse event. The fourteenth-day follow-up revealed that the paracetamol arm patients had faced several discomforts; indomethacin arm patients mostly complained only of tiredness. Indomethacin is a safe and effective drug for treating patients with mild and moderate covid-19.

The cardiovascular system: Mathematical modelling, numerical algorithms and clinical applications *

Abstract: Mathematical and numerical modelling of the cardiovascular system is a research topic that has attracted remarkable interest from the mathematical community because of its intrinsic mathematical difficulty and the increasing impact of cardiovascular diseases worldwide. In this review article we will address the two principal components of the cardiovascular system: arterial circulation and heart function. We will systematically describe all aspects of the problem, ranging from data imaging acquisition, stating the basic physical principles, analysing the associated mathematical models that comprise PDE and ODE systems, proposing sound and efficient numerical methods for their approximation, and simulating both benchmark problems and clinically inspired problems. Mathematical modelling itself imposes tremendous challenges, due to the amazing complexity of the cardiocirculatory system, the multiscale nature of the physiological processes involved, and the need to devise computational methods that are stable, reliable and efficient. Critical issues involve filtering the data, identifying the parameters of mathematical models, devising optimal treatments and accounting for uncertainties. For this reason, we will devote the last part of the paper to control and inverse problems, including parameter estimation, uncertainty quantification and the development of reduced-order models that are of paramount importance when solving problems with high complexity, which would otherwise be out of reach.

Dynamic Simulation of Bioprosthetic Heart Valves Using a Stress Resultant Shell Model

Abstract: It is a widely accepted axiom that localized concentration of mechanical stress and large flexural deformation is closely related to the calcification and tissue degeneration in bioprosthetic heart valves (BHV). In order to investigate the complex BHV deformations and stress distributions throughout the cardiac cycle, it is necessary to perform an accurate dynamic analysis with a morphologically and physiologically realistic material specification for the leaflets. We have developed a stress resultant shell model for BHV leaflets incorporating a Fung-elastic constitutive model for in-plane and bending responses separately. Validation studies were performed by comparing the finite element predicted displacement and strain measures with the experimentally measured data under physiological pressure loads. Computed regions of stress concentration and large flexural deformation during the opening and closing phases of the cardiac cycle correlated with previously reported regions of calcification and/or mechanical damage on BHV leaflets. It is expected that the developed experimental and computational methodology will aid in the understanding of the complex dynamic behavior of native and bioprosthetic valves and in the development of tissue engineered valve substitutes.

Significant differences in the material properties between aged human and porcine aortic tissues

Abstract: Objective:Currently,percutaneousaorticvalve(PAV)replacementdevicesarebeinginvestigatedtotreataorticstenosisinpatientsdeemedto be of too high a risk for conventional open-chest surgery. Successful PAV deployment and function are heavily reliant on the tissue—stent interaction. Many PAV feasibility trials have been conducted with porcine models under the assumption that these tissues are similar to human; however, this assumption may not be valid. The goal of this study was to characterize and compare the biomechanical properties of aged human and porcine aortic tissues. Methods: The biaxial mechanical properties of the left coronary sinus, right coronary sinus, non-coronary sinus, and ascending aorta of eight aged human (90.1 � 6.8 years) and 10 porcine (6—9 months) hearts were quantified. Tissue structure was analyzed via histological techniques. Results: Aged human aortic tissues were significantly stiffer than the corresponding porcine tissues in both the circumferential and longitudinal directions (p < 0.001). In addition, the nearly linear stress—strain behavior of the porcine tissues, compared with the highly nonlinear response of the human tissues at a low strain range, suggested structural differences between the aortic tissues from these two species. Histological analysis revealed that porcine samples were composed of more elastin and less collagen fibers than the respective human samples. Conclusions: Significant material and structural differences were observed between the human and porcine tissues, which raise questions on the validity of using porcine models to investigate the biomechanics involved in PAV intervention. # 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.