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Ramesh K.V.,IITB Monash Research Academy | Thaokar R.,Indian Institute of Technology Bombay | Prakash J.R.,Monash University | Prabhakar R.,Monash University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

The dynamics of adhesion of a spherical microparticle to a ligand-coated wall, in shear flow, is studied using a Langevin equation that accounts for thermal fluctuations, hydrodynamic interactions, and adhesive interactions. Contrary to the conventional assumption that thermal fluctuations play a negligible role at high Péclet numbers, we find that for particles with low surface densities of receptors, rotational diffusion caused by fluctuations about the flow and gradient directions aids in bond formation, leading to significantly greater adhesion on average, compared to simulations where thermal fluctuations are completely ignored. The role of wall hydrodynamic interactions on the steady-state motion of a particle, when the particle is close to the wall, has also been explored. At high Péclet numbers, the shear induced force that arises due to the stresslet part of the Stokes dipole plays a dominant role, reducing the particle velocity significantly and affecting the states of motion of the particle. The coupling between the translational and rotational degrees of freedom of the particle, brought about by the presence of hydrodynamic interactions, is found to have no influence on the binding dynamics. On the other hand, the drag coefficient, which depends on the distance of the particle from the wall, plays a crucial role at low rates of bond formation. A significant difference in the effect of both the shear force and the position-dependent drag force on the states of motion of the particle is observed when the Péclet number is small. © 2015 American Physical Society.

Nigam S.,Indian Institute of Technology Bombay | Bahadur D.,IITB Monash Research Academy
IEEE Transactions on Magnetics | Year: 2016

Green tea polyphenols have attracted significant interest due to their promising therapeutic potential as antitumor agents. These include catechins that have been explored for various tumors with minimal side effects. This paper demonstrates the fabrication and characterization of dendrimerized magnetic nanoparticles, as delivery vectors for epigallocatechin gallate (EGCG). Glutamic acid-functionalized iron oxide nanoparticles (Glu-Fe3O4) were synthesized and modified with the polyethylene glycol polyamidoamine dendrimers of generations 3, 5, and 6. Nanoparticles were characterized by X-ray diffraction, electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. In aqueous colloidal suspensions, they showed a rapid temperature increase under varying magnetic fields, suggesting their potential in chemothermal therapeutic applications. The loading efficiency of the dendrimerized nanoparticles was calculated to be 32.7%, 51.1%, and 56.4% for generations 3, 5, and 6, respectively. In acidic environments, a sustained drug release profile with an increasing but incomplete release was observed. Importantly, EGCG-loaded nanoparticles induced controlled cell death in human cervical cancer cells, demonstrating a 40% reduction in cell population over 24 h at the highest concentration used, with a linear dose-response. © 1965-2012 IEEE.

Wankhede R.G.,IITB Monash Research Academy | Wankhede R.G.,Indian Institute of Technology Bombay | Morey S.,Dow Chemical Company | Khanna A.S.,Indian Institute of Technology Bombay | Birbilis N.,Monash University
Applied Surface Science | Year: 2013

The development of an organic-inorganic sol-gel coating system (thickness ∼ 2 μm) on aluminum is reported. The coating uses glycidoxytrimethoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) as silane precursors, crosslinked with hexamethylmethoxymelamine (HMMM) and followed by hydrophobic modification using a water base short chain per-fluoro emulsion (FE). Such coating resulted in enhanced hydrophobicity with a contact angle of about 120 and sliding angle of 25 for a 20 μL water droplet. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed reduced corrosion upon coated substrates than the bare; correlated with both a higher degree of water repellency and formation of low permeable crosslinked sol-gel network. The structure of the coatings deposited was analyzed using Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy, revealing replacement of hydrophillic surface hydroxyls groups with low energy per-fluoro groups. © 2013 Elsevier B.V. All rights reserved.

Singh R.,Indian Institute of Technology Bombay | Vishal V.,Indian Institute of Technology Bombay | Vishal V.,IITB Monash Research Academy | Vishal V.,Monash University | Singh T.N.,Indian Institute of Technology Bombay
Scientia Iranica | Year: 2012

The physico-mechanical properties of rocks and rockmass are decisive for the planning of mining and civil engineering projects. The Schmidt hammer Rebound Number (RN), Slake Durability Index (SDI), Uniaxial Compressive Strength (UCS), Impact Strength Index (ISI) and compressive wave velocity (P-wave velocity) are important and pertinent properties to characterize rock mass, and are widely used in geological, geotechnical, geophysical and petroleum engineering. The Schmidt hammer rebound can be easily obtained on site and is a non-destructive test. The P-wave velocity and isotropic properties of rocks characterize rock responses under varying stress conditions. Many statistics based empirical equations have been proposed for the correlation between RN, SDI, UCS, ISI and P-wave velocity. The Artificial Neural Network (ANN), Fuzzy Inference System (FIS) and neuro-fuzzy system are emerging techniques that have been employed in recent years. So, in the present study, soft computing is applied to predict the P-wave velocity. 85 data sets were used for training the network and 17 data sets for the testing and validation of network rules. The network performance indices correlation coefficient, Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and Variance Account For (VAF) are 0.9996, 0.744, 25.06 and 99.97, respectively, which demonstrates the high performance of the predictive capability of the neuro-fuzzy system. © 2012 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.

Tripathi S.,IITB Monash Research Academy | Tabor R.F.,Monash University
Journal of Colloid and Interface Science | Year: 2016

The adsorption kinetics of many systems show apparent two-rate processes, where there appears to be resolved fast and slow adsorption steps. Such non-standard adsorption processes cannot be accounted for by conventional modeling methods, motivating new approaches. In this work, we present four different models that can account for two-rate adsorption and are based upon physically realistic processes - two adsorbing species, two surface sites having different energies, bilayer formation and molecular rearrangement modes. Each model is tested using a range of conditions, and the characteristic behavior is explored and compared. In these models, the effects of mass transport and bulk concentration are also accounted for, making them applicable in systems which are transport-limited or attachment-limited, or intermediate between the two. The applicability of these models is demonstrated by fitting exemplar experimental data for each of the four models, selecting the model on the basis of the known physical behavior of the adsorption kinetics. These models can be applied in a wide range of systems, from stagnant adsorption in large volume water treatment to highly dynamic flow conditions relevant to printing, coating and processing applications. © 2016 Elsevier Inc.

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