We investigate the influence of gold nanoparticle addition on the stability, dewetting, and pattern formation in ultrathin polymer-nanoparticle (NP) composite films by examining the length and time scales of instability, morphology, and dynamics of dewetting. For these 10-50 nm thick (h) polystyrene (PS) thin films containing uncapped gold nanoparticles (diameter approximately 3-4 nm), transitions from complete dewetting to arrested dewetting to absolute stability were observed depending on the concentration of the particles. Experiments show the existence of three distinct stability regimes: regime 1, complete dewetting leading to droplet formation for nanoparticle concentration of 2% (w/w) or below; regime 2, partial dewetting leading to formation of arrested holes for NP concentrations in the range of 3-6%; and regime 3, complete inhibition of dewetting for NP concentrations of 7% and above. Major results are (a) length scale of instability, where lambdaH approximately hn remains unchanged with NP concentration in regime 1 (n approximately 2) but increases in regime 2 with a change in the scaling relation (n approximately 3-3.5); (b) dynamics of instability and dewetting becomes progressively sluggish with an increase in the NP concentration; (c) there are distinct regimes of dewetting velocity at low NP concentrations; (d) force modulation AFM, as well as micro-Raman analysis, shows phase separation and aggregation of the gold nanoparticles within each dewetted polymer droplet leading to the formation of a metal core-polymer shell morphology. The polymer shell could be removed by washing in a selective solvent, thus exposing an array of bare gold nanoparticle aggregates.

We find that the 'jump-into-contact' of the cantilever in the atomic force microscope (AFM) is caused by an inherent instability in the motion of the AFM cantilever. The analysis is based on a simple model of the cantilever moving in a nonlinear force field. We show that the 'jump-into-contact' distance can be used to find the interaction of the cantilever tip with the surface. In the specific context of the attractive van der Waals interaction, this method can be realized as a new method of measuring the Hamaker constant for materials. The Hamaker constant is determined from the deflection of the cantilever at the 'jump-into-contact' using the force constant of the cantilever and the tip radius of curvature, all of which can be obtained by measurements. The results have been verified experimentally on a sample of cleaved mica, a sample of Si wafer with natural oxide and a silver film, using a number of cantilevers with different spring constants. We emphasize that the method described here is applicable only to surfaces that have van der Waals interaction as the tip-sample interaction. We also find that the tip to sample separation at the 'jump-into-contact' is simply related to the cantilever deflection at this point, and this provides a method to exactly locate the surface.

A nonenzymatic cholesterol biosensor was fabricated at the surface of carbon nanotube electrode (CCNT), obtained from coconut oil. The voltammetric behavior of cholesterol at CCNT electrode was investigated by cyclic voltammetry and differential pulse voltammetry in the presence of 0.001 M H 2 SO 4 as electrolyte . The influence of the experimental parameters on the peak currents of cholesterol like pH, accumulation time, and scan rates were optimized. Under optimum conditions, the peak current was found to be linear in the cholesterol concentration range from 1 to 50 lM with a sensitivity of *15.31 ± 0.01 lA lM -1 cm -2 and response time of about 6 s. Some characteristic studies of the nonenzymatic biosensor, such as reproducibility, substrate specificity, and storage stability have also been studied.

Voice Recognition is a fascinating field spanning several areas of computer science and mathematics. Reliable speech recognition is a hard problem, requiring a combination of many complex techniques; however modern methods have been able to achieve an impressive degree of accuracy. On the other hand, today, most of the companies or institutes are conducting their examinations online to be a part of this best ever growing world. In this system user can give any available examination at any accessible center as per his/her choice and authority also can condense manpower and process delay overhead. This paper offers one way to conduct online examination for physically challenged people who can use their voice only to register and attend the examination. In addition, in the course of this paper it has been tried to authenticate one registered user and to make the authentication process persistent throughout the examination interlude.

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