Interaction of surface water waves with a vertical elastic plate: a hypersingular integral equation approach

In this paper, we present an alternative method to investigate scattering of water waves by a submerged thin vertical elastic plate in the context of linear theory. The plate is submerged either in deep water or in the water of uniform finite depth. Using the condition on the plate, together with the end conditions, the derivative of the velocity potential in the direction of normal to the plate is expressed in terms of a Green’s function. This expression is compared with that obtained by employing Green’s integral theorem to the scattered velocity potential and the Green’s function for the fluid region. This produces a hypersingular integral equation of the first kind in the difference in potential across the plate. The reflection coefficients are computed using the solution of the hypersingular integral equation. We find good agreement when the results for these quantities are compared with those for a vertical elastic plate and submerged and partially immersed rigid plates. New results for the hydrodynamic force on the plate, the shear stress and the shear strain of the vertical elastic plate are also evaluated and represented graphically.     

Zinc-Ion-Induced Aggregation of Gold Clusters for Visible-Light-Excitation-Based Fluorimetric Discrimination of Geometrical Isomers

Herein, we report discrimination of dicarboxylic acids – fumaric acid (FA) and maleic acid (MA) – exhibiting geometrical isomerism, using nanoclusters based luminescent probe having excitation under broad day light. The luminescent probe was designed via complexation reaction between zinc ions and ligands (mercaptopropioinc acid; MPA) stabilizing the gold nanoclusters. This resulted in formation of nanoaggregates exhibiting bright green luminescence upon excitation at 450 nm capable of discriminating between FA and MA upto nanomolar level. The basis of discrimination has been attributed to deprotonation of FA and MA following interaction with MPA moieties present on the surface of the nanoaggregates and being governed by the stability of the respective conjugate base of the geometrical isomers of the dicarboxylic acids. As a consequence of different extent of deprotonation of FA and MA upon interaction with the cluster aggregates, different effect on the luminescence of the aggregates was observed, thus enabling discernible fluorimetric discrimination between FA and MA under visible light excitation.     

High-average-power kilohertz-repetition-rate sub-100-fs Ti:sapphire amplifier system

We report on a femtosecond Ti:sapphire laser amplifier system that generates pulse energies >5 mJ at a 1-kHz repetition rate. The system consists of regenerative and multipass amplifiers and uses the technique of chirped-pulse amplification. When the system was seeded with 70-fs pulses at 800 nm from a self-mode-locked Ti:sapphire oscillator, amplified pulses of 94-fs duration at a repetition rate of 1 kHz and an average output power of 5.4 W were produced. The amplified pulse-repetition rate is variable from 250 Hz to 3 kHz. Pulse energies of >7.5 mJ were obtained at 500 and 250 Hz.     

Water wave scattering by two sharp discontinuities in the surface boundary conditions

^** Corresponding author. Email: biren{at}isical.ac.in The problem of water wave scattering by two sharp discontinuitiesin the surface boundary conditions involving infinitely deepwater is examined here by reducing it to two coupled Carleman-typesingular integral equations. The discontinuities arise due tothe presence of two types of non-interacting materials floatingon the surface, one type being in the form of an infinite stripof finite width sandwiched between another type. The non-interactingmaterials form an inertial surface which is a mass-loading modelof floating ice and is regarded as a material of uniform surfacedensity having no elastic property. The two integral equationsare solved approximately by assuming the two discontinuitiesto be widely separated, and approximate analytical expressionsfor the reflection and transmission coefficients are also obtained.This problem has applications in wave propagation through stripsof frazil or pancake ice modelled as floating inertial surfaces.Numerical results for the reflection coefficient are depictedgraphically against the wave number for different values ofthe surface densities of the two types of floating materials.The main feature of the graphs is the oscillatory nature ofthe reflection coefficient and occurrence of zero reflectionfor an increasing sequence of discrete values of the wave number.A direct analytical treatment to solve the integral equationsnumerically, when the separation length between the two discontinuitiesis arbitrary, is also indicated. For the case of more than twodiscontinuities the solution methodology of the correspondingscattering problem is described briefly.     

Ab initio study of K adsorption on a Ag(100) surface

Ab initio Hartree–Fock calculations are reported for the chemisorption of K on Ag using three different types of clusters to model the system. Geometry optimization is done in 4 degrees of freedom. It is found that since there is an absence of complete charge transfer between the adsorbate and substrate, the interaction can be interpreted as being predominately covalent in nature.     

Isolation of a new two-dimensional honeycomb carbonato-bridged copper(II) complex exhibiting long-range ferromagnetic ordering

Atmospheric CO2 fixation by an aqueous solution containing Cu(ClO4)2.6H2O and 4-aminopyridine (4-apy) yields a novel example of a two-dimensional mu3-CO3 bridged copper(II) complex {[Cu(4-apy)2]3(mu3-CO3)2(ClO4)2.(1/2)CH3OH}n that has been characterized by IR, UV and X-ray crystallography; preliminary magnetic measurements show that complex exhibits long-range ordered ferromagnetic coupling.     

Synthesis and structural characterization of [Ni(Me2NCH2CH2CH2N=CHC6H4O)2]

The synthesis, properties, and X-ray crystal structure of a Ni(II) complex of the tridentate Schiff base ligand Me₂NCH₂CH₂CH₂N=CHC₆H₄OH(LH) are described. The complex crystallizes in the monoclinic space group P2₁/c, with a = 10.180(2), b = 15.169(3), c = 15.293(4) Å, = 106.69(2)°, and Z = 4. The Ni atom shows a distorted fac-octahedral geometry, with the two Ni—N(Me₂) bonds being significantly longer than the two Ni—N(imino) bonds, 2.284(9), 2.310(9) vs. 2.051(2), 2.055(2) Å.     

ICP-AES analysis of impurities in PuO2 after separation of Pu by TOPO impregnated XAD-4

Nuclear fuels should meet some specified characteristics to achieve their better performance in the reactor. Hence controlling and monitoring of trace level elements in the fuel materials are essential. Atomic emission spectroscopic methods are most popular for the trace level analysis. An ICP-AES procedure is described here for the trace level impurity analysis of PuO₂ produced through PUREX process. To avoid the Pu interference in the impurity analysis, initially the Pu was separated by extraction chromatography using TOPO impregnated XAD-4 resin. Magnitude of Pu interference in the impurities spectra lines was investigated. Moreover the recovery of impurity elements using the resin was established.