Oscillation results for fourth-order nonlinear dynamic equations

This work is concerned with the oscillation of a certain class of fourth-order nonlinear dynamic equations on time scales. A new oscillation result and an example are included.     

Nanosphere Templated Metallic Grating Assisted Enhanced Fluorescence

In this paper, enhanced fluorescence from a silver film coated nanosphere templated grating is presented. Initially, numerical simulation was performed to determine the plasmon resonance wavelength by varying the thickness of the silver film on top of a monolayer of 400 nm nanospheres. The simulation results are verified experimentally and tested for enhancing fluorescence from fluorescein isothiocyanate whose excitation wavelength closely matches with the plasmon resonance wavelength of the substrate with 100 nm silver film over nanosphere. The 12 times enhancement in the intensity is attributed to the local field enhancement in addition to the excitation of surface plasmon polaritons along the surface.     

Degradation of dichlorvos using hydrodynamic cavitation based treatment strategies

The degradation of an aqueous solution of dichlorvos, a commonly used pesticide in India, has been systematically investigated using hydrodynamic cavitation reactor. All the experiments have been carried out using a 20 ppm solution of commercially available dichlorvos. The effect of important operating parameters such as inlet pressure (over a range 3-6 bar), temperature (31 °C, 36 °C and 39 °C) and pH (natural pH = 5.7 and acidic pH = 3) on the extent of degradation has been investigated initially. It has been observed that an optimum value of pressure gives maximum degradation whereas low temperature and pH of 3 are favorable. Intensification studies have been carried out using different additives such as hydrogen peroxide, carbon tetrachloride, and Fenton’s reagent. Use of hydrogen peroxide and carbon tetrachloride resulted in the enhancement of the extent of degradation at optimized conditions but significant enhancement was obtained with the combined use of hydrodynamic cavitation and Fenton’s chemistry. The maximum extent of degradation as obtained by using a combination of hydrodynamic cavitation and Fenton’s chemistry was 91.5% in 1 h of treatment time. The present work has conclusively established that hydrodynamic cavitation in combination with Fenton’s chemistry can be effectively used for the degradation of dichlorvos.     

Photodissociation effects on pulsed laser deposited silver oxide thin films: surface‐enhanced resonance Raman scattering

Temporal Raman scattering measurements with 488, 532 and 632 nm excitation wavelengths and normal Raman studies by varying the power (from 30 W/cm² to 2 MW/cm²) at 488 nm were performed on silver oxide thin films prepared by pulsed‐laser deposition. Initially, silver oxide Raman spectra were observed with all three excitation wavelengths. With further increase in time and power, silver oxide photodissociated into silver nanostructures. High‐intensity spectral lines were observed at 1336 ± 25 and 1596 ± 10 cm⁻¹ with 488 nm excitation. No spectral features were observed with 633 nm excitation. Surface‐enhanced resonance Raman scattering theory is used to explain the complex behavior in the intensity of the 1336/1596 cm⁻¹ lines with varying power of 488 nm excitation. Copyright © 2011 John Wiley & Sons, Ltd.     

Monotone-iterative method for mixed boundary value problems for generalized difference equations with “maxima”

In this paper the authors investigate special type of difference equations which involve both delays and the maximum value of the unknown function over a past time interval. This type of equations is used to model a real process which present state depends significantly on its maximal value over a past time interval. An appropriate mixed boundary value problem for the given nonlinear difference equation is set up. An algorithm, namely, the monotone iterative technique is suggested to solve this problem approximately. An important feature of our algorithm is that each successive approximation of the unknown solution is equal to the unique solution of an appropriately constructed initial value problem for a linear difference equation with “maxima”, and a formula for its explicit form is given. Also, each approximation is a lower/upper solution of the given nonlinear boundary value problem. Several numerical examples are considered to illustrate the practical application of the suggested algorithm.     

Robust turn structures in α3β cyclic tetrapeptides induced and controlled by carbo-β3 amino acid

Designing cyclic tetrapeptides (CTPs), which fold into desired structures, is often a challenging task. While it is difficult to synthesize them, they are also prone to adopt multiple conformations. In this paper we report the synthesis and conformational studies of CTP mimics, having nonconstrained α(3)β motif, that exhibit stable β- and γ-turn structures. We also demonstrate the transformation of β-turn to γ-turn structure in similar CTPs by inverting the chirality of β(3) carbon in C-linked-carbo-β(3)-amino acid (Caa) from R to S.     

Spectrophotometric determination of plutonium III, IV, and VI concentrations in nitric acid solution

The determination of the concentration of various valency states of plutonium is desirable in various stages of the Plutonium/Uranium Recovery by EXtraction (PUREX) process for the effective separation and purification of plutonium. A method is optimized for the quantitative spectrophotometric determination of Pu(III), Pu(IV) and Pu(VI) existing separately or in mixed oxidation states in 1.5?M nitric acid medium. Molar absorption co-efficient (??) for the major absorption peaks with baseline correction are evaluated. With these ?? data a method is proposed for determining the molar concentration of each oxidation state.     

Electro-oxidative process for the mineralization of solvent and recovery of plutonium from organic wastes

Mediated electrochemical oxidation is a promising technique for the destruction of organic compounds. Destruction of tributyl phosphate (TBP) in normal paraffin hydrocarbon (NPH) in nitric acid medium containing electro-generated Ag(II) was studied. Initially, the effect of uranium, presence of DBP along with uranium in the organic phase and direct electrochemical oxidation without catalyst (Ag) on the destruction of 30% TBP/NPH system was evaluated. For a comparison, the rate of destruction of NPH alone was studied. Further, radioactive laboratory waste solution was tested for the destruction of organic waste under similar experimental conditions. The electrolyte used in the system was 0.5 M AgNO₃ in 8 M HNO₃ at 333 K. The uniqueness in all these experiments is the use of a double end open porcelain diaphragm for the isolation of electrodes. Though there would be a slight reduction in the efficiency, two major hurdles viz., reduction in the concentration of nitric acid and reduction in the volume of catholyte resulting in an increase in cell voltage were avoided. The problem of the migration of Ag⁺/Ag²⁺ and accumulating at the cathode site was overcome by using double end open diaphragm and thorough mixing. The results revealed that the rate of destruction of organics is favoured in the presence of uranium in organic phase and with increase in temperature.