Nematic DNA Thermotropic Liquid Crystals with Photoresponsive Mechanical Properties

Over the last decades, water‐based lyotropic liquid crystals of nucleic acids have been extensively investigated because of their important role in biology. Alongside, solvent‐free thermotropic liquid crystals (TLCs) from DNA are gaining great interest, owing to their relevance to DNA‐inspired optoelectronic applications. Up to now, however, only the smectic phase of DNA TLCs has been reported. The development of new mesophases including nematic, hexagonal, and cubic structures for DNA TLCs remains a significant challenge, which thus limits their technological applications considerably. In this work, a new type of DNA TLC that is formed by electrostatic complexation of anionic oligonucleotides and cationic surfactants containing an azobenzene (AZO) moiety is demonstrated. DNA–AZO complexes form a stable nematic mesophase over a temperature range from ?7 to 110 °C and retain double‐stranded DNA structure at ambient temperature. Photoisomerization of the AZO moieties from the E‐ to the Z‐ form alters the stiffness of the DNA–AZO hybrid materials opening a pathway toward the development of DNA TLCs as stimuli‐responsive biomaterials.     

Spread spectrum image watermark detection on degraded compressed sensing measurements with distortion minimization

Multimedia Tools and Applications - In the age of digital world, the wide dissemination of images need bandwidth (BW) efficient transmission as well as ownership protection during transmission over...     

Special issue on computing,communication and sensor network: CCSN,Puri, Odisha,India, 2014

Microsystem Technologies -     

An image-in-image communication scheme using secret sharing and M-ary spread spectrum watermarking

Microsystem Technologies - Secret image sharing is a means of secure transmission of images on an open network through meaningful share generation that reduces suspiciousness of conventional image...     

A new mechanistic model for liquid-liquid phase transfer catalysis: Reaction of benzyl chloride with aqueous ammonium sulfide

A new mechanistic model for reactions involving two liquid phases and a homogeneous phase transfer catalyst (PTC) has been developed based on extraction mechanism considering the equilibrium of catalyst and active catalysts at the interface. The proposed kinetic model considers thermodynamic framework based aqueous phase ionic equilibrium and the separate contributions of non-PTC and PTC-enhanced reactions towards the overall reactions. The developed model was then applied to an industrially important reaction of benzyl chloride with aqueous ammonium sulfide for synthesis of dibenzyl sulfide and benzyl mercaptan. The kinetic parameters of the developed model were estimated at different temperatures using an indigenously developed non-linear regression technique based on modified Levenberg-Marquardt algorithm. Sensitivity analysis was then performed under various experimental conditions using the estimated parameters and the results were compared with experimental observations. A good agreement was observed between experimental and calculated values with proper trends of the results.     

Modeling cyclic ratcheting based fatigue life of HSLA steels using crystal plasticity FEM simulations and experiments

This paper develops a plastic ratcheting based fatigue failure model for HSLA steels from a combination of results from experiments and finite element simulations using crystal plasticity constitutive relations. It predicts the nucleation of major cracks in the microstructure in ratcheting. Subsequently, the total life is limited by the growth of ductile fracture in the microstructure, which is factored in by comparing the simulated results with experiments. A crystal plasticity based FEM (CPFEM) model is used in this paper to predict the local plastic strain in the microstructure which plays a role in the ratcheting life. Orientation imaging based microstructural information (orientation and misorientation distributions) is incorporated in CPFEM. The model proposed has the ability to represent a range of behavior from low and high cycle behavior in the life models. The predictions from it are found to be in excellent agreement with experimental data.     

Toughening of epoxy resin with amine functional aniline acetaldehyde condensate

The diglycidyl ether of bisphenol-A (DGEBA) resin was modified with amine functional aniline acetaldehyde condensate (AFAAC) and cured with an ambient temperature curing agent triethylene tetramine. The resulting networks displayed significantly improved fracture toughness. The AFAAC was synthesized by the condensation reaction of aniline and acetaldehyde in the acid medium (pH 4) and characterized by FTIR and NMR spectroscopy, elemental analysis, viscosity measurements, and mole of primary and secondary amine analysis. The DGEBA and AFAAC were molecularly miscible but developed a two-phase microstructure upon network formation. Epoxy/AFAAC compositions were systematically varied to study the effect of AFAAC concentration on the impact, adhesive, tensile, and flexural properties of modified networks. The dynamic mechanical analysis and scanning electron microscopy studies showed two phase morphology in the cured networks, where AFAAC particles were dispersed. The AFAAC modified epoxy network was thermally stable up to around 280°C. POLYM. ENG. SCI., 47:1695–1702, 2007. © 2007 Society of Plastics Engineers