Study of dispersion, absorption and permittivity of an synthetic insulation paper—with change in frequency and thermal aging

This paper deals with the calculation of various parameters such as dispersion, absorption and permittivity of synthetic insulation paper to see the effect of frequency and thermal aging to be used in various industrial applications. Firstly the calculations were made for a fresh sample and then for the samples, which were aged at three different times and temperatures. These calculations were done using the earlier reported data [1] of capacitance and loss factor. The studies showed that with the increase in frequency the dispersion, absorption and permittivity of the samples decrease, however, with aging (increasing time and decreasing temperature) the values of dispersion, absorption and permittivity increase at any fixed frequency.     

Numerical computation of the linear convective and absolute stability of free-shear flows

The linear stability of free-shear flows is governed by their dispersion characteristics. The dispersion relation can be obtained by integrating the Rayleigh equation. The integration process can be hampered by the presence of singularities within the domain of integration. A complex-domain contour integration procedure is presented that enables this integration to be performed in a modular and robust fashion. This is accomplished by deforming the original integration contour into piecewise-continuous line-segments in the complex domain to avoid all the singularities. This integration technique can then be used to find absolute and convective instabilities of the medium by a simple procedure. However when the velocity profile for a shear layer is obtained from experiments or numerical simulations, it is available only along the real-axis. Thus the complex-domain integration procedure cannot be applied unless a functional fit is obtained for the velocity profile. For convectively unstable systems, the integration can be carried out along the real-axis only for self-excited systems. However, for a certain class of free-shear flows, it is shown that an absolute instability can still be calculated by integrating the Rayleigh equation along the real-axis. This leads to the development of a fully automatic absolute-instability solver and a semi-automatic convective-instability solver.     

Pressure induced phase transformation and electronic properties of AlAs

We have performed the first-principle study to analyze the structural and electronic properties of aluminum arsenide under the application of pressure. The computations have been carried out using the ground state total energy calculation approach of the system. The first-principle approach has been used to compute the stability of various phases of AlAs, like original zinc blende (B3), intermediate NiAs (B8), NaCl (B1) and CsCl (B2) type as a function of pressure. The study observes a B3–B8, B3–B1 and B3–B2 transitions at 6.99 GPa, 8.18 GPa and 73.43 GPa. The computed phase transition pressures, lattice parameters, bulk modulus, and energy gaps are in good agreement with their experimental as well as theoretical counterparts. Band structure and density of states analysis have also been performed and results have been discussed in detail.     

Analysis of F-shape microstrip line fed dualband antenna for WLAN applications

An analysis of microstrip line fed antennas has been presented theoretically using circuit theory concept. The theoretical investigations of F-shape antenna parameters such as return loss, VSWR, gain and efficiency have been calculated. It is found that antenna resonate at 2.4 and 5.2 GHz for lower and upper resonance frequencies respectively. The bandwidth of the F-shape antenna at lower resonance frequency is 20.08 % (simulated) and 17.05 % (theoretical) whereas at upper resonance frequency, it is 5.93 % (simulated) and 5.78 % (theoretical). The characteristics of the F-shape antenna is compared with other microstrip line fed antennas. It is found that F-shape antenna is linearly polarised along the X direction. The theoretical results are compared with IE3D simulation results as well as reported experimental results and they are in close agreement.     

Allosteric Binding Sites of Aβ Peptides on the Acetylcholine Synthesizing Enzyme ChAT as Deduced by In Silico Molecular Modeling

The native function of amyloid-β (Aβ) peptides is still unexplored. However, several recent reports suggest a prominent role of Aβ peptides in acetylcholine homeostasis. To clarify this role of Aβ, we have reported that Aβ peptides at physiological concentrations can directly enhance the catalytic efficiency of the key cholinergic enzyme, choline acetyltransferase (ChAT), via an allosteric interaction. In the current study, we further aimed to elucidate the underlying ChAT-Aβ interaction mechanism using in silico molecular docking and dynamics analysis. Docking analysis suggested two most probable binding clusters on ChAT for Aβ₄₀ and three for Aβ₄₂. Most importantly, the docking results were challenged with molecular dynamic studies of 100 ns long simulation in triplicates (100 ns × 3 = 300 ns) and were analyzed for RMSD, RMSF, RoG, H-bond number and distance, SASA, and secondary structure assessment performed together with principal component analysis and the free-energy landscape diagram, which indicated that the ChAT-Aβ complex system was stable throughout the simulation time period with no abrupt motion during the evolution of the simulation across the triplicates, which also validated the robustness of the simulation study. Finally, the free-energy landscape analysis confirmed the docking results and demonstrated that the ChAT-Aβ complexes were energetically stable despite the unstructured nature of C- and N-terminals in Aβ peptides. Overall, this study supports the reported in vitro findings that Aβ peptides, particularly Aβ₄₂, act as endogenous ChAT-Potentiating-Ligand (CPL), and thereby supports the hypothesis that one of the native biological functions of Aβ peptides is the regulation of acetylcholine homeostasis.     

Crystal chemistry of Ruddlesden-Popper type structures in highT c ceramic superconductors

Similar structural patterns have been noticed in the systems La-Cu-O, La-Ni-O and Bi and Tl-containing superconducting oxides. The formation of Ruddlesden-Popper type layers (alternating slabs of rocksalt and perovskite structures) is seen in these oxides which is similar in many respects to what is seen in the system Sr-Ti-O. However, there are some significant differences, for example the rocksalt and perovskite blocks in new superconducting compounds are not necessarily electrically neutral, unlike in the Sr-Ti-O system. It, thus, becomes necessary to create oxygen vacancies in the basic perovskite (figure 1) structure of Bi-containing compounds, when the width of the perovskite slab changes on addition of extra Cu-O planes. Results of our atomistic simulations suggest that these missing oxygen ions allow the Cu-O planes to buckle in Bi-series of compounds. This is also supported by the absence of buckling in the Sr-Ti-O series of compounds and the first member of Bi-containing compounds in which there are no missing oxygen ions. We present additional results on the phase stability of polytypoid structures in La-Cu-O system and defect chemistry of compounds of La-Ni-O system.     

Ultra-low contact resistance of epitaxially interfaced bridged silicon nanowires

Laterally oriented single-crystal silicon nanowires are epitaxially grown between highly doped vertically oriented silicon electrodes in the form of nanobridges. Resistance values extracted from the current-voltage measurements for a large number of nanobridges with varying lengths and diameters are used to propose a model which highlights the relative contribution of the contact resistance to the total resistance for nanowire-based devices. It is shown that the contact resistance depends on the effective conducting cross-section area and hence is influenced by the presence of a surface depletion layer. On the basis of our measured data and constructed model, we estimated the specific contact resistance to be in the range 3.74 x 10(-6) to 5.02 x 10(-6) Omega cm2 for our epitaxial interfacing method. This value is at least an order of magnitude lower than that of any known contact made to nanowires with an evaporated metal film, a common method for integrating semiconductor nanowires in devices and circuits.