Nanoparticle transport in saturated porous medium using magnetic resonance imaging

Transport study of nanoparticle (NP) through matrix flow dominated aquifer sand and soils have significant influence in natural systems. To quantify the transport behaviour, magnetic resonance imaging (MRI) was used to image the iron oxide based nanoparticle, Molday ION (carboxyl terminated) through saturated sandstone rock core. T2-weighted images were acquired and the changes in image intensity were calibrated to get a quantitative concentration profiles at various time intervals. These profiles were evaluated through CXTFIT transport model to estimate the transport parameters. These parameters are estimated at various points along the length of the column while classical breakthrough curve analysis cannot provide these details. NP–surface interactions were investigated using DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. The dispersion coefficients (2.55–1.21 × 10−7 m2/s) were found to be decrease with distance, deposition rate constant k (6.70–9.13 × 10−4 (1/s)) and fast deposition rate constant kfast (4.32–8.79 × 10−2 (1/s)) were found to be increase with distance. These parameter variations over length will have a scaling up impact in developing transport models for environmental remediation and risk assessment schemes

Nonlinear Dynamics of Moving Curves and Surfaces: Applications to Physical Systems

The subject of moving curves (and surfaces) in three dimensional space (3-D) is a fascinating topic not only because it represents typical nonlinear dynamical systems in classical mechanics, but also finds important applications in a variety of physical problems in different disciplines. Making use of the underlying geometry, one can very often relate the associated evolution equations to many interesting nonlinear evolution equations, including soliton possessing nonlinear dynamical systems. Typical examples include dynamics of filament vortices in ordinary and superfluids, spin systems, phases in classical optics, various systems encountered in physics of soft matter, etc. Such interrelations between geometric evolution and physical systems have yielded considerable insight into the underlying dynamics. We present a succinct tutorial analysis of these developments in this article, and indicate further directions. We also point out how evolution equations for moving surfaces are often intimately related to soliton equations in higher dimensions.Comment: Review article, 38 pages, 7 figs. To appear in Int. Jour. of Bif. and Chao

Shape-changing Collisions of Coupled Bright Solitons in Birefringent Optical Fibers

Wecritically review the recent progress in understanding soliton propagation in birefringent optical fibers.By constructing the most general bright two-soliton solution of the integrable coupled nonlinear Schroedinger equation (Manakov model) we point out that solitons in birefringent fibers can in general change their shape after interaction due to a change in the intensity distribution among the modes even though the total energy is conserved. However, the standard shape-preserving collision (elastic collision) property of the (1+1)-dimensional solitons is recovered when restrictions are imposed on some of the soliton parameters. As a consequence the following further properties can be deduced using this shape-changing collision. (i) The exciting possibility of switching of solitons between orthogonally polarized modes of the birefringent fiber exists. (ii) When additional effects due to periodic rotation of birefringence axes are considered, the shape changing collision can be used as a switch to suppress or to enhance the periodic intensity exchange between the orthogonally polarized modes. (iii) For ultra short optical soliton pulse propagation in non-Kerr media, from the governing equation an integrable system of coupled nonlinear Schroedinger equation with cubic-quintic terms is identified. It admits a nonlocal Poisson bracket structure. (iv) If we take the higher-order terms in the coupled nonlinear Schroedinger equation into account then their effect on the shape-changing collision of solitons, during optical pulse propagation, can be studied by using a direct perturbational approach.Comment: 14 pages, ROMP31, 4 EPS figure

Influence of zeolite on heavy metal immobilization in municipal solid waste compost contaminated soil

The application of Municipal solid waste as compost (MSWC) in agricultural fields has become one of the most common practices. Besides its benefits, it poses some harmful effects on soil, as it increases the heavy metal content in MSWC of the soil. It is necessary to find a way to reduce the bioavailability of heavy metals in MSWC  before its application into the soil. This study aimed at exploring the efficiency of zeolite as an immobilizer to dwindle heavy metal bioavailability. An incubation experiment was conducted wherein the soil samples were artificially spiked with different rates of MSWC (0, 5, and 10 t ha-1). The zeolite was added to the spiked soil at 5 different levels, namely 0, 5, 10, 15, and 20 %, and their effect on bioavailable heavy metal status was observed during different incubation intervals (0, 15. 30, 60, 90, and 120 days). Results unveiled that applying 10% zeolite significantly (P<0.05) reduced the bioavailability of lead (Pb) and nickel (Ni)  to Below the detectable limit (Bdl) in all soil samples. Furthermore, the organic carbon status of soil was also enriched by MSWC and 10% zeolite application. The soil pH slightly increased (7.39) with applying 10% zeolite resulting in the immobilization of heavy metals. Hence, 10% zeolite application was one of the most effective immobilizers in eliminating the bioavailability of heavy metals. Therefore, it can be concluded that mixing zeolite with MSWC before applying it to crop fields can reduce the heavy metal overload in soil. Hence, this study highlights the potential of zeolite as an effective choice in dwindling the soil's bioavailability of heavy metal content

Exact soliton solutions of coupled nonlinear Schr\"odinger equations: Shape changing collisions, logic gates and partially coherent solitons

The novel dynamical features underlying soliton interactions in coupled nonlinear Schr{\"o}dinger equations, which model multimode wave propagation under varied physical situations in nonlinear optics, are studied. In this paper, by explicitly constructing multisoliton solutions (upto four-soliton solutions) for two coupled and arbitrary $N$-coupled nonlinear Schr{\"o}dinger equations using the Hirota bilinearization method, we bring out clearly the various features underlying the fascinating shape changing (intensity redistribution) collisions of solitons, including changes in amplitudes, phases and relative separation distances, and the very many possibilities of energy redistributions among the modes of solitons. However in this multisoliton collision process the pair-wise collision nature is shown to be preserved in spite of the changes in the amplitudes and phases of the solitons. Detailed asymptotic analysis also shows that when solitons undergo multiple collisions, there exists the exciting possibility of shape restoration of atleast one soliton during interactions of more than two solitons represented by three and higher order soliton solutions. From application point of view, we have shown from the asymptotic expressions how the amplitude (intensity) redistribution can be written as a generalized linear fractional transformation for the $N$-component case. Also we indicate how the multisolitons can be reinterpreted as various logic gates for suitable choices of the soliton parameters, leading to possible multistate logic. In addition, we point out that the various recently studied partially coherent solitons are just special cases of the bright soliton solutions exhibiting shape changing collisions, thereby explaining their variable profile and shape variation in collision process.Comment: 50 Pages, 13 .jpg figures. To appear in PR

Effect of Process Variables on Electrochemical Micromachining of Titanium Alloy (Ti-3Al-2.5V)

Electro-chemical Machining (ECM) is mainly used for shaping, deburring, milling and finishing operations in various precision industries and its use in micron level machining is called Electro-Chemical Micro Machining (EMM). EMM and ECM are receiving considerable attention from high-tech industries. It is because it allows to manufacture structures of complex shapes, it has high precision and accuracy, it is simpler and eco-friendly manufacturing technique and it can be used for different conducting materials. Different industry working with water which is saline, needs heat exchanger for the process. Titanium Alloy (Ti-3Al-2.5V) due to its high corrosion resistance under saline conditions is preferred by these industries. This present work is mainly concentrated on identifying the Material Removal rate (MRR) of Titanium Alloy (Ti-3Al-2.5V) workpiece by varying the process parameters like voltage, electrolyte concentration and duty cycle on electro-chemical micro machining

In situ synthesis of size-controlled, stable silver nanoparticles within ultrashort peptide hydrogels and their anti-bacterial properties

We have developed a silver-releasing biomaterial with promising potential for wound healing applications. The material is made of ultrashort peptides which can self-assemble in water to form hydrogels. Silver nanoparticles (Ag NPs) were synthesized in situ within the biomaterial, using only UV irradiation and no additional chemical reducing agents. The synthetic strategy allows precise control of the nanoparticle size, with the network of peptide fibers preventing aggregation of Ag NPs. The biomaterial shows increased mechanical strength compared to the hydrogel control. We observed a sustained release of Ag NPs over a period of 14 days. This is a crucial prerequisite for effective anti-bacterial therapy. The ability to inhibit bacterial growth was tested using different bacterial strains, namely gram-negative Escherichia coli and Pseudomonas aeruginosa and gram-positive Staphylococcus aureus. Inhibition of bacterial growth was observed for all strains. The best results were obtained for Pseudomonas aeruginosa which is known for exhibiting multidrug resistance. Biocompatibility studies on HDFa cells, using Ag NP-containing hydrogels, did not show any significant influence on cell viability. We propose this silver-releasing hydrogel as an excellent biomaterial with great potential for applications in wound healing due to its low silver content, sustained silver nanoparticle release and biocompatibility

Delay-enhanced coherent chaotic oscillations in networks with large disorders

We study the effect of coupling delay in a regular network with a ring topology and in a more complex network with an all-to-all (global) topology in the presence of impurities (disorder). We find that the coupling delay is capable of inducing phase-coherent chaotic oscillations in both types of networks, thereby enhancing the spatiotemporal complexity even in the presence of 50% of symmetric disorders of both fixed and random types. Furthermore, the coupling delay increases the robustness of the networks up to 70% of disorders, thereby preventing the network from acquiring periodic oscillations to foster disorder-induced spatiotemporal order. We also confirm the enhancement of coherent chaotic oscillations using snapshots of the phases and values of the associated Kuramoto order parameter. We also explain a possible mechanism for the phenomenon of delay-induced coherent chaotic oscillations despite the presence of large disorders and discuss its applications.Comment: 13 pages, 20 figure

Collision of Multimode Dromions and a Firewall in the Two Component Long Wave Short Wave Resonance Interaction Equation

In this paper, we investigate the two component long wave short wave resonance interaction (2CLSRI) equation and show that it admits the Painleve property. We then suitably exploit the recently developed truncated Painleve approach to generate exponentially localized solutions for the short wave components $S^{(1)}$ and $S^{(2)}$ while the long wave L admits line soliton only. The exponentially localized solutions driving the short waves $S^{(1)}$ and $S^{(2)}$ in the y direction are endowed with different energies (intensities) and are called "multimode dromions". We also observe that the multimode dromions suffer intramodal inelastic collision while the existence of a firewall across the modes prevents the switching of energy between the modes.Comment: published in J. Phys. A: Math. Theor. 42, 10200

Intermittency transitions to strange nonchaotic attractors in a quasiperiodically driven Duffing oscillator

Different mechanisms for the creation of strange nonchaotic attractors (SNAs) are studied in a two-frequency parametrically driven Duffing oscillator. We focus on intermittency transitions in particular, and show that SNAs in this system are created through quasiperiodic saddle-node bifurcations (Type-I intermittency) as well as through a quasiperiodic subharmonic bifurcation (Type-III intermittency). The intermittent attractors are characterized via a number of Lyapunov measures including the behavior of the largest nontrivial Lyapunov exponent and its variance as well as through distributions of finite-time Lyapunov exponents. These attractors are ubiquitous in quasiperiodically driven systems; the regions of occurrence of various SNAs are identified in a phase diagram of the Duffing system.Comment: 24 pages, RevTeX 4, 12 EPS figure