Somnath Ghosh

Bio: Somnath Ghosh is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topic(s): Microstructured optical fiber & Optical fiber. The author has an hindex of 28, co-authored 287 publication(s) receiving 3318 citation(s). Previous affiliations of Somnath Ghosh include University of Calcutta & Indian Institute of Science.

Tunable Nanowrinkles on Shape Memory Polymer Sheets

Abstract: (Figure Presented) Controllable biaxial and uniaxial nanowrinkles (see figure) are fabricated by a simple two-step approach - metal deposition and subsequent heating - based on shape memory polymer (prestressed polystyrene) sheets. The wavelengths of the wrinkles can be tuned by controlling the thickness of deposited metal. The ready integration of the nanowrinkles into microchannels and their effectiveness in surface enhanced sensing is demonstrated. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

ZnO/Ag nanohybrid: synthesis, characterization, synergistic antibacterial activity and its mechanism

Abstract: A highly homogeneous ZnO/Ag nanohybrid has been synthesized by a novel route, employing chitosan as mediator by purely electrostatic interaction. By employing various techniques such as powder XRD, UV-visible, IR spectroscopy and electron (SEM, TEM) microscopy, the formation of the nanohybrid has been established. The synergistic antibacterial effect of ZnO/Ag nanohybrid on Gram-positive and Gram-negative bacteria is found to be more effective, compared to the individual components (ZnO and Ag). Cytotoxicity experiments are carried out and the results are correlated to the solubility of the nanohybrid. A possible mechanism has been proposed for the antibacterial activity of ZnO/Ag nanohybrid, based on TEM studies on bacteria, carried out by employing the microtome technique and by EPR measurements on the hybrid.

Trapping of drops by wetting defects

Abstract: Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable tracks—with potential applications in microfluidics

Antimicrobial activity of highly stable silver nanoparticles embedded in agar-agar matrix as a thin film.

Abstract: Highly stable silver nanoparticles (Ag NPs) in agar-agar (Ag/agar) as inorganic-organic hybrid were obtained as free-standing film by in situ reduction of silver nitrate by ethanol. The antimicrobial activity of Ag/agar film on Escherichia coli (E. coil), Staphylococcus aureus (S. aureus), and Candida albicans (C albicans) was evaluated in a nutrient broth and also in saline solution. In particular, films were repeatedly tested for antimicrobial activity after recycling. UV-vis absorption and TEM studies were carried out on films at different stages and morphological studies on microbes were carried out by SEM. Results showed spherical Ag NPs of size 15-25 nm, having sharp surface plasmon resonance (SPR) band. The antimicrobial activity of Ag/agar film was found to be in the order, C. albicans > E. coil > S. aureus, and antimicrobial activity against C. albicans was almost maintained even after the third cycle. Whereas, in case of E. coil and S. aureus there was a sharp decline in antimicrobial activity after the second cycle. Agglomeration of Ag NPs in Ag/agar film on exposure to microbes was observed by TEM studies. Cytotoxic experiments carried out on HeLa cells showed a threshold Ag NPs concentration of 60 mu g/mL, much higher than the minimum inhibition concentration of Ag NPs (25.8 mu g/mL) for E. coli. The mechanical strength of the film determined by nanoindentation technique showed almost retention of the strength even after repeated cycle. (C) 2010 Elsevier Ltd. All rights reserved.

Exceptional points and asymmetric mode conversion in quasi-guided dual-mode optical waveguides.

Abstract: Non-Hermitian systems host unconventional physical effects that be used to design new optical devices. We study a non-Hermitian system consisting of 1D planar optical waveguides with suitable amount of simultaneous gain and loss. The parameter space contains an exceptional point, which can be accessed by varying the transverse gain and loss profile. When light propagates through the waveguide structure, the output mode is independent of the choice of input mode. This “asymmetric mode conversion” phenomenon can be explained by the swapping of mode identities in the vicinity of the exceptional point, together with the failure of adiabatic evolution in non-Hermitian systems.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Recent advances in shape–memory polymers: Structure, mechanism, functionality, modeling and applications

Abstract: Research on shape–memory polymers (SMPs) has been actively conducted for more than three decades. Recently, interest in this area has intensified. Even though there have been a number of related review papers published in the past 3 years, a generalized view on the important aspects of SMPs that would give a holistic picture of this promising area of research is still lacking. This paper will provide a comprehensive review that integrates the achievements in studying SMPs and their derivatives, such as composites and compound structures, as well as their current applications. Concepts, principles/modelings, structures and related synthesis methods, applications and future trends will be examined.

Phytochemistry of the genus Piper

Abstract: The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references. © 1997 Elsevier Science Ltd