Identifying the mechanisms of polymer friction through molecular dynamics simulation

Mechanisms governing the tribological behavior of polymer-on-polymer sliding were investigated by molecular dynamics simulations. Three main mechanisms governing frictional behavior were identified. Interfacial "brushing" of molecular chain ends over one another was observed as the key contribution to frictional forces. With an increase of the sliding speed, fluctuations in frictional forces reduced in both magnitude and periodicity, leading to dynamic frictional behavior. While "brushing" remained prevalent, two additional irreversible mechanisms, "combing" and "chain scission", of molecular chains were observed when the interfaces were significantly diffused.     

Redox-switchable superhydrophobic silver composite

Unique packaging of Ag(2)O on the surface of polycrystalline AgCl allows fabrication of a new useful, superhydrophobic composite material. This pure inorganic material with surface porosity of submicrometer aperture size fabricates air pockets, which make the composite material superhydrophobic. The new material behaves like lotus leaves, butterfly wings, or water strider's leg in relation to superhydrophobicity. Visible light induces photoreduction of solid Ag(2)O surface layer and generates Ag(0), making the composite surface superhydrophilic. Reoxidation of Ag(0) on the composite surface gives back the hydrophobicity that represents the redox-switchable wetting property of the material.     

On the Convergence of Finite Element Method for Second Order Elliptic Interface Problems

The purpose of this paper is to study the convergence of finite element approximation to the exact solution of general self-adjoint elliptic equations with discontinuous coefficients. Due to low global regularity of the solution, it is difficult to achieve optimal order of convergence with classical finite element methods [Numer. Math. 1998; 79:175–202]. In this paper, an isoparametric type of discretization is used to prove optimal order error estimates in L ² and H ¹ norms when the global regularity of the solution is low. The interface is assumed to be of arbitrary shape and is smooth for our purpose. Further, for the purpose of numerical computations, we discuss the effect of numerical quadrature on finite element solution, and the related optimal order estimates are also established.     

Effect of Al doping on structural,optical and electrical properties of SnO2 thin films synthesized by pulsed laser deposition

Aluminium-doped (Al = 0–5?wt.%) SnO₂ thin films with low-electrical resistivity and high optical transparency have been successfully synthesized by pulsed laser deposition technique at 500 °C. Structural, optical and electrical properties of the as-deposited and post-annealed thin films were investigated. X-ray diffraction patterns suggest that the films transform from crystalline to amorphous state with increasing aluminium content. The root mean square (R_q) surface roughness parameter, determined by atomic force microscopy decreases upon annealing of the as-deposited film. While resistivity of the film is the lowest (9.49 × 10^?4 Ω-cm) at a critical doping level of 1?wt.% Al, optical transparency is the highest (nearly 90%) in the as-deposited condition. Temperature dependence of the electrical resistivity suggests that the Mott’s variable range hopping process is the dominant carrier transport mechanism in the lower temperature range (40–135 K) for all the films whereas, thermally activated band conduction mechanism seems to account for conduction in the higher temperature region (200–300 K).     

Laser assisted bound-free transition of a polaron bound to an impurity center

The scattering of a bound Frohlich large polaron in the presence of a coulomb impurity center as well as a linearly polarized laser field is studied. The differential (DCS) as well as the momentum transfer cross sections (MTCS) and the conductivity depend remarkably on the electron–phonon coupling (_αP${\alpha }_P$) and the strength of the coulomb impurity (β$\beta$). The strongly bound polaron is found to be reluctant to contribute to the conductivity which is justified physically. The curves for MTCS and conductivity verses _αP${\alpha }_P$ and β$\beta$ appear to be complementary, indicating the possibility of controlling the mobility and thereby conductivity by varying one of the parameters. This behavior indicates the possibility of optimizing the composition of optoelectronic materials where laser is the dominant source of excitation.     

Spectral intensities of lanthanide complexes

The effects of solvents and complex formation with nitrogen donor ligands on the spectral intensities of the f→f transitions in Nd(III) ion have been reported. The intensity parameters T_λ have been calculated for 14 systems and are compared with oxygen donor ligands.     

Design of a Hybrid Fiber-Optic Network Using 3-D Optical Code Sequences

We present the design of a 3-dimensional (3-D) noncoherent optical hybrid network. We also report the design of a new family of 3-D codes for fiber optic hybrid networks. We show that the hybrid network allows for shorter bit times and a higher number of users, given a set chip rate, compared to previously conceived networks. These newly designed hybrid single-pulse-per-row (HSPR) codes have very low autocorrelation side-lobes and very small cross-correlation peaks. We compare the performance of our hybrid model using our codes with the Optical Orthogonal Codes (OOCs) and Temporal/Spatial (T/S) codes and show that the new network can support a greater number of users and higher data rates than those using OOCs and T/S codes.     

Vibrational Spectrum of Para-Fluoro Phenetole

Abstract

The 400–4000 Cm^?1infrared absorption apectrum of p-fluoro phenetole molacule in liquid phase is reported. The observed spectrum is interpreted on the assumption that the melecule has C₂ symmetry together with the assignments of the fundamental vibrations to various probable modes of vibrations.