Infrared and Raman spectroscopies of InP/II–VI core-shell nanoparticles

We use infrared (IR) and Raman spectroscopies to investigate the optically active phonon modes in InP nanoparticles and InP/II–VI core-shell nanoparticles fabricated by similar colloidal chemistry methods. The IR transmission spectra of several InP nanoparticle samples exhibit a common absorption feature, which we assign to the Fröhlich mode. The Raman results for the same samples show transverse and longitudinal optical phonon peaks, and scattering strength in between due to surface optical (SO) modes. Infrared spectra of the InP/ZnSe core-shell nanoparticles () exhibit three absorption features, one due to the InP core, and the others associated with the ZnSe shell layer. Raman measurements (12–292 K) also show three phonon-related peaks, whose intensities vary sharply with temperature. The frequencies of the IR and Raman lines are in approximate accord with dielectric continuum theory.     

Study of precipitation in NaCl:Pb2+ by light scattering and ultramicroscopy

The formation and dissolution behaviour of precipitates in NaCl : Pb²⁺ single crystals is studied by light scattering and ultramicroscopy. Measurements of Rayleigh ratio together with ultramicroscopic observations during isochronal annealing indicate the presence of two types of precipitates in as-grown crystals. Isochronal annealing after suitable thermal and thermomechanical treatments shows that precipitates of first type (I) which form and dissolve at lower temperatures, are due to homogeneous nucleation. Precipitates of the second category (II) which form and dissolve at higher temperatures are aligned along crystallographic directions and have their origin in stress-assisted processes. Isothermal annealing has been used to study the dissolution kinetics of the precipitated fraction, and it is found that the kinetics is of first order. The enthalpy of solution is determined from a study of the temperature dependence of the kinetic rate constant, in conjunction with available information on the migration energy of Pb²⁺ in NaCl. The enthalpy so deduced is in good agreement with the value as usually obtained from the concentration dependence of the dissolution temperature.     

Solution of singular integral equations with logarithmic and Cauchy kernels

A direct method of solution is presented for singular integral equations of the first kind, involving the combination of a logarithmic and a Cauchy type singularity. Two typical cases are considered, in one of which the range of integration is a single finite interval and, in the other, the range of integration is a union of disjoint finite intervals. More such general equations associated with a finite number (greater than two) of finite, disjoint, intervals can also be handled by the technique employed here.     

Simple modification of a protein database for mass spectral identification of N-linked glycopeptides

We describe an algorithm which modifies a protein database such that during a database search deamidation is limited to asparagines strictly contained within the N-glycosylation consensus sequence. The modified database was evaluated using a dataset created from the shotgun proteomic analysis of N-linked glycopeptides from human blood serum. We demonstrate that the application of the modified database eliminates incorrect glycopeptide assignments, reduces the peptide false-discovery rate, and eliminates the need for manual validation of glycopeptide identifications.     

Effects of partial slip on axisymmetric flow of an electrically conducting viscoelastic fluid past a stretching sheet

The entrained flow of an electrically conducting non-Newtonian, viscoelastic second grade fluid due to an axisymmetric stretching surface with partial slip is considered. The partial slip is controlled by a dimensionless slip factor, which varies between zero (total adhesion) and infinity (full slip). Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equation into an ordinary differential equation. The issue of paucity of boundary conditions is addressed, and an effective numerical scheme has been adopted to solve the obtained differential equation even without augmenting the boundary conditions. The important findings in this communication are the combined effects of the partial slip, magnetic interaction parameter and the second grade fluid parameter on the velocity and skin friction coefficient. It is observed that in presence of slip, the velocity decreases with an increase in the magnetic parameter. That is, the Lorentz force which opposes the flow leads to enhanced deceleration of the flow. Moreover, it is interesting to find that as slip increases in magnitude, permitting more fluid to slip past the sheet, the skin friction coefficient decreases in magnitude and approaches zero for higher values of the slip parameter, i.e., the fluid behaves as though it were inviscid.     

Photoionization of the excited He atom in Debye plasmas

We present theoretical photoionization cross sections for He 1s2s ¹S and He 1s2p ¹P states in a Debye plasma environment by the complex coordinate rotation method, using a finite L² basis set constructed from one electron Laguerre orbitals. The plasma environment is found to appreciably influence the photoionization cross sections near the ionization threshold. In this regard, the photoionization cross sections of isolated He are compared with other theoretical and experimental results. Our results are in good agreement with the previous results. A new minimum appears in the photoionization cross section curve for the metastable 1s2s ¹S state. Results are given for the S- and D-wave partial photoionization for the excited 1s2p ¹P state.     

Numerical Investigation of Sound Generation due to Laminar Flow Past Elliptic Cylinders

Numerical investigation of sound generation due to unsteady laminar flow past elliptic cylinders has been carried out using direct numerical simulation $(DNS)$ approach at a free-stream Mach number of $0.2$. Effects of aspect ratio $(0.6\le AR\le 1.0)$ and Reynolds number $(100\le Re \le 160)$ on the characteristics of radiated sound fields are analyzed. Two-dimensional compressible fluid flow equations are solved on a refined grid using high resolution dispersion relation preserving $(DRP)$ schemes. Using present $DNS$ data, equivalent noise sources as given by various acoustic analogies are evaluated. Amplitudes and frequencies associated with these noise sources are further related to characteristics of disturbance pressure fields. Disturbance pressure fields are intensified with increase in Reynolds number and aspect ratio. Thus, radiated sound power increases with increase in Reynolds number and aspect ratio. Among various cases studied here, minimum and maximum values of radiated sound power are found at $Re=120$ & $AR=0.6$ and $Re=160$ & $AR=1.0$, respectively. Directivity patterns show that the generated sound fields are dominated by the lift dipole for all cases. Next, proper orthogonal decomposition $(POD)$ technique has been implemented for decomposing disturbance pressure fields. The $POD$ modes associated with the lift and the drag dipoles have been identified. $POD$ analyses also clearly display that the radiated sound fields are dominated by the lift dipole only. Further, acoustic and hydrodynamic modes obtained using Doak's decomposition method have confirmed the patterns of radiated sound field intensities.     

Stability of the generalized quadratic and quartic type functional equation in non-Archimedean fuzzy normed spaces

In this paper, we prove some stability results concerning the generalized quadratic and quartic type functional equation in the context of non-Archimedean fuzzy normed spaces in the spirit of Hyers-Ulam-Rassias. As applications, we establish some results of approximately generalized quadratic and quartic type mapping in non-Archimedean normed spaces. Also, we show that the assumption of the non-Archimedean absolute value of $2$ is less than $1$ cannot be omitted in our corollaries. The results improve and extend some recent results.