ORCID Profile
0000-0002-5788-6696
Current Organisation
Indian Institute of Technology Madras
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Publisher: Springer Singapore
Date: 31-12-2018
Publisher: Frontiers Media SA
Date: 09-02-2022
Abstract: There is mounting evidence for the therapeutic use of faecal microbiota transplant (FMT) in numerous chronic inflammatory diseases. Germ free mice are not always accessible for FMT research and hence alternative approaches using antibiotic depletion prior to FMT in animal studies are often used. Hence, there is a need for standardising gut microbiota depletion and FMT methodologies in animal studies. The aim of this study was to refine gut decontamination protocols prior to FMT engraftment and determine efficiency and stability of FMT engraftment over time. Male C57BL/6J mice received an antibiotic cocktail consisting of icillin, vancomycin, neomycin, and metronidazole in drinking water for 21 days ad libitum . After antibiotic treatment, animals received either FMT or saline by weekly oral gavage for 3 weeks (FMT group or Sham group, respectively), and followed up for a further 5 weeks. At multiple timepoints throughout the model, stool s les were collected and subjected to bacterial culture, qPCR of bacterial DNA, and fluorescent in-situ hybridisation (FISH) to determine bacterial presence and load. Additionally, 16S rRNA sequencing of stool was used to confirm gut decontamination and subsequent FMT engraftment. Antibiotic treatment for 7 days was most effective in gut decontamination, as evidenced by absence of bacteria observed in culture, and reduced bacterial concentration, as determined by FISH as well as qPCR. Continued antibiotic administration had no further efficacy on gut decontamination from days 7 to 21. Following gut decontamination, 3 weekly doses of FMT was sufficient for the successful engraftment of donor microbiota in animals. The recolonised animal gut microbiota was similar in composition to the donor s le, and significantly different from the Sham controls as assessed by 16S rRNA sequencing. Importantly, this similarity in composition to the donor s le persisted for 5 weeks following the final FMT dose. Our results showed that 7 days of broad-spectrum antibiotics in drinking water followed by 3 weekly doses of FMT provides a simple, reliable, and cost-effective methodology for FMT in animal research.
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2018
Publisher: AIP Publishing
Date: 07-2022
DOI: 10.1063/5.0096749
Abstract: The complex flow-field associated with a spherical structure oscillating adjacent to a solid boundary is significant in ocean engineering. The dynamic interaction between the flow induced by an oscillating sphere and the boundary is evident not only in terms of flow-field deformation around the structures but also on the boundary in the form of shear stress modifications. The present study aims to understand the influence of a plane boundary on the shear stress distributions and particle motion near the boundary induced by the flow due to a submerged sphere oscillating in a viscous fluid. Experiments are conducted using a non-intrusive flow visualization technique, and three-dimensional direct numerical simulations are used to link the time-mean results of the experiments to the simulated Lagrangian particle drift on the plane boundary. The dye tracer in the experiments and the Lagrangian particles in the simulation congregate at the same location. This stagnation location coincides with a ring of zero mean shear stress centered on the point on the plane boundary through which the axis of oscillation of the sphere passes. This ring of zero mean stress is termed the congregation zone. The radius of the particle congregation zone is investigated as a function of the sphere oscillating litude, Reynolds number, and the distance between the center of the sphere and the plane boundary. Furthermore, a systematic power scaling law is established for the radius of the congregation zone from the control parameters.
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 07-2004
Publisher: Elsevier BV
Date: 10-2004
Publisher: AIP Publishing
Date: 09-2021
DOI: 10.1063/5.0065651
Abstract: The dynamic interaction of submerged spherical structures with ocean waves alters the local flow field and is responsible for the movement of sediments over the seabed, which would have detrimental effects on the ecosystems. The present research aims to gain insight into the effect of a plane boundary on the vorticity dynamics and shear modifications on the plane boundary induced by the flow due to an oscillating sphere. The flow field around an oscillating sphere close to a plane boundary is investigated numerically by three-dimensional direct numerical simulation of the Navier–Stokes equations. The sphere oscillates perpendicular to the plane boundary modeling the seabed. The flow structure, resulting mean and fluctuating shear stress distribution on the plane boundary, and the Lagrangian particle transport are investigated as a function of the sphere oscillation litude, Reynolds number, and the distance of the sphere from the plane boundary. The systematic correlations for the variation of maximum shear stress on the plane boundary are estimated from scaling parameters. The time-mean results are then linked to the Lagrangian particle transport where it is observed that the Lagrangian path lines track the mean streamlines closely. Further, the particles at the stagnation zone cease drifting and oscillate about a constant mean position. The practical significance of this result is that a ring of zero mean shear on the seabed is found toward where particles congregate. This provides a guide for the optimum location for the mooring anchors, minimizing the risk of anchor scour or undermining.
No related grants have been discovered for Sannasiraj Sannasi Annamalaisamy.