Electronic and vibrational spectra of some rare earth trifluoromethanesulfonates crystals

Nanocrystalline ZnO powders have been synthesized by a low temperature solution combustion method. The photoluminescence (PL) spectrum of as-formed and heat treated ZnO shows strong violet (402, 421, 437, 485 nm) and weak green (520 nm) emission peaks respectively. The PL intensities of defect related emission bands decrease with calcinations temperature indicating the decrease of Zn(i) and V(o)(+) caused by the chemisorptions of oxygen. The results are correlated with the electron paramagnetic resonance (EPR) studies. Thermoluminescence (TL) glow curves of gamma irradiated ZnO nanoparticles exhibit a single broad glow peak at ～343°C. This can be attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centers. The trapping parameters of ZnO irradiated with various γ-doses are calculated using peak shape method. It is observed that the glow peak intensity increases with increase of gamma dose without changing glow curve shape. These two characteristic properties such as TL intensity increases with gamma dose and simple glow curve structure is an indication that the synthesized ZnO nanoparticles might be used as good TL dosimeter for high temperature application.     

Effects of the Low Frequencies of Noise on On–Off Intermittency

A bifurcating system subject to multiplicative noise can exhibit on–off intermittency close to the instability threshold. For a canonical system, we discuss the dependence of this intermittency on the Power Spectrum Density (PSD) of the noise. Our study is based on the calculation of the Probability Density Function (PDF) of the unstable variable. We derive analytical results for some particular types of noises and interpret them in the framework of on-off intermittency. Besides, we perform a cumulant expansion (N. G. van Kampen, 24, 171 (1976).) for a random noise with arbitrary power spectrum density and we show that the intermittent regime is controlled by the ratio between the departure from the threshold and the value of the PSD of the noise at zero frequency. Our results are in agreement with numerical simulations performed with two types of random perturbations: colored Gaussian noise and deterministic fluctuations of a chaotic variable. Extensions of this study to another, more complex, system are presented and the underlying mechanisms are discussed. PACS Number: 05.40.-a, 05.45.-a, 91.25.-r     

Electronic absorption spectra of 1,2,3-trimethyl benzene

The electronic absorption spectra of 1,2,3-trimethyl benzene in the vapour and solid phases and in an isobutyl alcohol rigid glass at 90°K are described in this paper. Some characteristic features of the vibrational structure of the spectra are discussed.     

Intensification of the reaction between Udaipur rock phosphate and sulphuric acid by means of ultrasound

The solid-liquid reaction between Udaipur rock phosphate and different concentrations of sulphuric acid is found to be greatly enhanced when the reaction is carried out in the presence of high intensity ultrasound (800 kHz and 80 W cm^?2). Even coarser rock particles up to 50 mesh (BSS) can be effectively decomposed in the presence of ultrasound to such an extent that is suitable for utilization in a commercial phosphatic fertilizer plant, which is not otherwise possible. The ultrasound helps the diffusion of reactants on to the solid rock particles and also inhibits the coating of calcium sulphate, formed during the reaction, on the unreacted solid rock particles. The decomposition curve of Udaipur rock phosphate at 80°C with different concentrations of sulphuric acid contains two maxima and two minima which are controlled by the concentration of H₃O⁺, HSO₄^? and SO₄^2? ions in the medium as the reaction proceeds. It is found that the presence of ultrasound reduces the difference between these maxima and minima and the decomposition is increased in all cases.     

Influence of high intensity ultrasound on wet process phosphoric acid

High intensity ultrasound (800 kHz and 80 Wcm^-2) is passed through phosphoric acid of different origins and concentrations. Its influence on fluorine content, viscosity, density, colour and tendency to form sludge on ageing is observed. The quantity of fluorine in all samples of acid goes on decreasing with the time of exposure to ultrasound. Due to removal of fluorine by the ultrasound, the tendency of the acids to form sludge also decreases. The evolution of fluorine from the wet process phosphoric acid may be due to the decomposition of H₂SiF₆ present in the acid to HF and SiF₄ by the enormous amount of energy released due to cavitation. The exposed acid thus becomes purer, and can be concentrated and transported easily without sludge formation.     

Fabrication of a metal nanoparticles and polymer nanofibers composite material by an in situ chemical synthetic route

This work demonstrated a facile route for the synthesis of poly(3,5-dimethyl aniline) nanofibers by polymerization of 3,5-dimethyl aniline using Pd-acetate as the oxidant. The reduction of Pd ion is accompanied by oxidative polymerization of 3,5-dimethyl aniline, leading to a metal-polymer composite material. Palladium nanoparticles (approximately 2 nm) are uniformly distributed throughout the polymer that makes the composite material a unique morphology. The resultant composite material was characterized by means of different techniques. IR and Raman spectra provide the information on the chemical structure of the polymer. TEM images show the morphology of the polymer and size of the metal particles.     

Observation of a phase object using carrier-frequency photography

A Ronch ruling is photographed through a phase object which produces deformations in the grating lines. The superposition of the straight rulings and the deformed ones on the photographic plate gives rise to a moiré pattern which characterises the phase variations of the object.     

Characterization of collagen fibers in Bruch’s membrane using chemical force microscopy

Bruch’s membrane is a layer composed of collagen fibers located just beneath the retina. This study validates a strategy used to map the morphological and adhesion characteristics of collagen fibers in Bruch’s membrane. Atomic force microscopy tips were functionalized with different chemical groups and used to map the hydrophilic and hydrophobic regions on the surface of the eye tissue. The largest adhesion forces were observed when tips functionalized with NH₂ groups were used. The trend in the adhesion forces was rationalized based on the distribution of different functional groups in the triple-helical structure of the collagen fibers. The results of this study can be used to design more effective strategies to treat eye diseases such as age-related macular degeneration.     

The impact of information technology on the banking industry

This paper analyses the effects of investment in information technologies (IT) in the banking sector using bank-level data from a panel of 68 US banks over the period 1986–2005. Although IT can improve bank's performance by reducing operational cost (supply side), it can bring in competition among banks in order to embrace new technology (demand side). Since most empirical studies have adopted the production function approach, it is difficult to identify which effect has dominated. In a differentiated model with network effects, this paper characterizes the conditions to identify these two effects. The results suggest that (at individual firm levels) the bank profits can decline due to adoption and diffusion of IT investment, reflecting negative network competition effects in this industry. Using panel cointegration tests, we confirm that the estimated profit equation is indeed a long-run equilibrium relation.     

Alkyne Versus Ynamide Reactivity: Regioselective Radical Cyclization of Yne‐Ynamides

Ynamides are typically more reactive than simple alkynes and olefins. However, a serendipitous observation revealed a rare case where the reactivity of simple alkynes exceeds that of ynamides. This led to the development of a unique sulfur‐radical‐triggered cyclization of yne‐tethered ynamides, which involves attack of the alkyne by a thiyl radical followed by cyclization with the ynamide. A wide range of novel 4‐thioaryl pyrroles that could tolerate common functional moieties and N‐protecting groups were expediently constructed by this strategy. The current method contrasts with the typical cyclization of yne‐ynamides, which involves the attack of the alkyne moiety by the ynamide core. Control experiments and DFT calculations supported the participation of the sulfur radical in the reaction and the regioselective cyclization. The synthetic potential of the substituted pyrroles is also discussed.