Capturing the elasticity and morphology of live fibroblast cell cultures during degradation with atomic force microscopy

Atomic force microscopy, in a liquid environment, was used to capture in vitro the morphological and mechanical changes that cultured fibroblasts undergo as time elapses from the completion of the cell culture. Topography images illustrated that initially, the nucleus had a height of 1.18 ± 0.2 μm, and after 48 h it had decreased to 550 ± 60 nm; similarly, the cell membrane exhibited significant shrinkage from 34 ± 4 to 23 ± 2 μm. After each image scan, atomic force microscopy indentation was performed on the centre of the nucleus, to measure the changes in the cell elasticity. Examination of the force‐distance curves indicated that the membrane elastic modulus at the nucleus remained the same within the time frame of 48 h, even though the cell morphology had significantly changed.     

Comparison of reliability characteristics of two (double component) systems with bivariate exponential lifetimes

The analysis of two systems each having a single unit with two components arranged in parallel is considered. System 2 differs from system I due to the additional feature of preventive maintenance. A bivariate extension of the exponential distribution is taken for the lifetimes of two components. This distribution is specifically applicable to those parallel systems which can function until one of the components is operative, but the failure of one component affects the lifetime parameter of the other. Important reliability characteristics have been investigated and the two systems have been compared theoretically and graphically to observe the effect of preventive maintenance on system performance.     

On the method of calibration of the energy dispersive EXAFS beamline at Indus-2 and fitting theoretical model to the EXAFS spectrum

A procedure for calibration of the recently developed energy dispersive EXAFS beamline at the Indus-2 synchrotron source at RRCAT, Indore, India has been described. The procedure involves recording of absorption spectra of two standard samples, whose absorption edge energies are well-established. Two methods have been considered for calibration. In the first method, the position of the first maximum of the derivative of absorption curve is taken as the position of the edge energy. In the second method, the position of the point at half edge step in the absorption curve is taken as the position of the edge energy. It has been shown that only the first method gives same values of dispersion even when the beam current is varied and should be used for calibrating the experimental spectra. Further, it is recommended that the performance of the beamline for a particular setting should be checked by recording and analysing EXAFS of a standard. Hence, the procedure for analysis and extracting information about the various parameters that can be determined by fitting the EXAFS data with a theoretical model has also been described, by taking the example of K-absorption spectra of copper metal foil recorded on this beamline.     

Gyrotron and peniotron modes in rotating-beam devices

Several authors have assumed the existence of the (s + 1), s and (s ? 1) harmonic interactions in the electron beam immersed in an axial magnetic field (Dohler et al. 1982, Ono et al. 1983). This paper examines the interaction between a relativistically rotating electron layer and electromagnetic fields with exp (jωt ? Γz ? jsθ) variation. The linearized relativistic Lorentz force equation is used to evaluate the RF displacement due to harmonic fields. It can be shown from this analysis that in the non-relativistic case, the beam waves are one at the (s + 1), one at the (s ? 1) and two at the s harmonic of the cyclotron frequency. These modes may be identified as the fast (s + 1) and slow (s ? 1) peniotron modes. This result is consistent with existing theories. The gyrotron interaction is observed as a result of energy exchange between the forward circuit wave and two beam waves at the s harmonic; it is a three-wave interaction. Whereas the fast (slow) peniotron interaction is observed as a result of energy exchange between the forward circuit wave and the fast (slow) peniotron wave at s + 1 (s ? 1) harmonics; it is a two-wave interaction. The polarization-variable approach is used to relate the RF displacement to the RF current density and the RF charge density. The dispersion relations are then derived by solving for the electromagnetic fields in cylindrical waveguide, consistent with the current and charge densities in the electron layer for each instability. The results are compared with existing theories.     

Impact of interfacial interactions on optical and ammonia sensing in zinc oxide/polyaniline structures

Zinc oxide/polyaniline (ZnO/PANI) hybrid structures have been investigated for their optical and gas sensing properties. ZnO nanoparticles, prepared by the sol–gel method, pressed in the form of pellets were used for gas sensing. The hybrid ZnO/PANI structure was obtained by the addition of PANI on the surface of ZnO. The UV–Vis absorption of the modified pellets show band edge at 363 nm corresponding to ZnO, while a change in the absorption peaks for PANI was observed. The possible interaction between Zn^2?+? of ZnO and NH-group of PANI was confirmed using Raman spectroscopy studies. The results reveal that the hybrid structures exhibit much higher sensitivity to NH $_{{3}}$ gas at room temperature than blank ZnO, which is sensitive to NH₃ gas at higher temperature. This enhancement has been attributed to the creation of active sites on the ZnO surface due to the presence of PANI.