Visual attention model based dual watermarking for simultaneous image copyright protection and authentication

Multimedia Tools and Applications - In this paper, a visual attention model based dual watermarking scheme has been proposed for simultaneous image copyright protection and authentication. The...     

Effect of silica doping on the densification and grain growth in zinc oxide

The ability of silica (SiO₂) in controlling the densification and grain growth behavior of nano crystalline zinc oxide (ZnO) has been systematically studied. It has been observed that SiO₂ acts as a sintering inhibitor in the ZnO–SiO₂ system up to 4 wt.% limiting value beyond which densification behavior of the system remains almost unchanged, especially above 1100 °C. The addition of SiO₂ to ZnO retards grain growth which in turn results a finer ultimate grain size as compared to the undoped ZnO. However, stabilization in grain size occurs at ≥4 wt.% SiO₂ addition. It has been observed that SiO₂ incorporation changes the grain growth mechanism up to 4 wt.% addition, beyond which no remarkable changes was noticed. The grain growth (n) shows distinctly different slopes as a function of sintering time for the SiO₂ doped ZnO systems than undoped ZnO. The different slopes tend to indicate that different diffusion mechanisms and probably the formation of a secondary phase (Zn–Si–O) at the grain boundary control the densification and grain growth. The thermal expansion coefficient of the system has been found to decrease substantially beyond 4 wt.% SiO₂ addition to ZnO.     

Nanostructures from Single Amino Acid‐Based Molecules: Stability,Fibrillation, Encapsulation,and Fabrication of Silver Nanoparticles

The small‐sized molecules that have been developed from single hydrophobic amino acids (Phe, Trp, Tyr and Leu) by suitably protecting the –NH₂ and –CO₂H groups generate diverse nanoscopic structures – such as nanorods, nanofibrils, nanotubes, and nanovesicles – depending upon the protection parameters and solvent polarity. The vesicular structures get disrupted in the presence of various salts, such as KCl, CaCl₂, (NH₄)₂SO₄ and N(n‐Bu)₄Br. Insertion of unnatural (o/m/p)‐aminobenzoic acids as a protecting group and the lack of conventional peptide bonds in the molecules give the nanostructures proteolytic stability. The nanostructures also show significant thermal stability along with a morphological transformation upon heat treatment. Our in vitro studies reveal that the addition of micromolar concentration “curcumin” significantly reduces the formation of amyloid‐like fibrils. These diverse nanostructures are used as a template for fabricating silver nanoparticles on their outer surfaces as well as in the inner part, followed by calcination in air which helps to obtain a 1D silver nanostructure. Furthermore, the nanovesicles are observed to encapsulate a potent drug (curcumin) and other biologically important molecules, which could be released through salt‐triggered disruption of vesicles.     

Mobile sink based data collection for energy efficient coordination in wireless sensor network using cooperative game model

Telecommunication Systems - Multi-hop communication in a wireless sensor network leads to unbalanced energy consumption, creating “hot spots” around the sensor nodes. Selection of paths...     

Recent Advances in Transition Metal-Catalyzed Functionalization of gem-Difluoroalkenes

gem-Difluorinated alkenes are readily accessible building blocks that can undergo functionalization to provide a broad spectrum of fluorinated and non-fluorinated products. Herein, we review recent (since 2017) transition metal-catalyzed transformations of these specialized alkenes and summarize general reactivity patterns of these reactions. Many transition metal-catalyzed reactions undergo net C−F bond functionalization reactions to deliver monofluorinated products. These reactions typically proceed through β-fluoroalkylmetal intermediates that readily eliminate a β-fluoride to deliver monofluoroalkene products. A second series of reactions exploit coinage metal fluorides to add F⁻ to the gem-difluorinated alkene, and further functionalization delivers trifluoromethyl-containing products. In stark contrast, few transition metal-catalyzed reactions proceed in net “fluorine-retentive processes” to deliver difluoromethylene-based products.     

Tunable morphology from 2D to 3D in the formation of hierarchical architectures from a self-assembling dipeptide: thermal-induced morphological transition to 1D nanostructures

Construction of complex three-dimensional (3D) architectures through hierarchical self-assembly of peptide molecules has become an attractive approach of fabricating multifunctional advanced materials due to their various potential applications in bionanotechnology. This paper describes the tunable formation of flower-like 3D hierarchical architectures of intricate morphology from a simple self-assembling dipeptide phenylalanine–tyrosine with a facile preparative method by applying a range of voltages through a drop of peptide solution. The fine-tuning of voltages and their application time enable to produce morphological changes of the microstructures from 2D to 3D and also control their formation. The morphology has been characterized by the gradual change in the height-to-diameter ratio of the microstructures with change in the applied voltages. Moreover, these microstructures show significant thermal stability over a wide range of temperatures, whereas adequately high temperature promotes the morphological transformation of the microstructures into different types of ultrathin 1D nanostructures such as nanowires, nanofibrils, etc. Furthermore, we have suggested a possible growth model for the fabrication of unique hierarchical architectures through diffusion-limited aggregation mechanism.