Tunable delay line with interacting whispering-gallery-mode resonators

We theoretically study a parallel configuration of two interacting whispering-gallery-mode optical resonators and show a narrowband modal structure as a basis for a widely tunable delay line. For the optimum coupling configuration the system can possess an unusually narrow spectral feature with a much narrower bandwidth than the loaded bandwidth of each individual resonator. The effect has a direct analogy with the phenomenon of electromagnetically induced transparency in quantum systems for which the interference of spontaneous emission results in ultranarrow resonances.     

Whispering gallery resonators for studying orbital angular momentum of a photon

We propose a simple method for generation and detection of photons with nonzero angular momentum. The method utilizes high-quality factor ring resonators that transform a plane electromagnetic wave into a wave with nonzero angular momentum, and vice versa. We show that the method is especially promising for studying high-order Bessel beams, unreachable by other techniques.     

Direct determination of free energies of colloidal dispersions

Helmholtz free energies of electrostatically-stabilized colloidal dispersions of monodispersed spherical particles have been obtained using computer experiments. Boltzmann sampling has been shown to be sufficient for determining free energy differences between two dispersions whose pair-potentials are close to each other. Non-Boltzmann sampling has been used when the pair-potentials differ substantially. These results have been compared with the results based on perturbation theory. The techniques used, thus, offer a direct method to test the latter.     

Ringdown spectroscopy of stimulated Raman scattering in a whispering gallery mode resonator

We report experimental observations of power-dependent, nonexponential decay of light stored in whispering gallery modes caused by stimulated Raman scattering in the resonator host material. Specifically, we show that the instantaneous decay rate of whispering gallery modes of a calcium fluoride resonator increases as the amount of light stored in the resonator decreases.     

Applying different types of artificial neural network for modeling thermal conductivity of nanofluids containing silica particles

Journal of Thermal Analysis and Calorimetry - Nanofluids are widely applicable in thermal devices with porous structures. Silica nanoparticles have been dispersed in different heat transfer fluids...     

Highly stable electrochemical oxidation of phenolic compounds at carbon ionic liquid electrode

A carbon ionic liquid electrode (CILE) was used for the investigation of the electrochemical oxidation of phenolic compounds in acidic media using cyclic voltammetry, chronoamperometry and square wave voltammetry techniques. The results indicate that, contrary to many other electrodes, the oxidation of phenolic compounds on CILE is highly stable and does not result in electrode fouling. Cyclic voltammetry showed that phenolic compounds such as phenol, 2,4-dichlorophenol and catechol were oxidized at CILE and remained electroactive after multiple cycles and at high concentrations of phenol. The cyclic voltammetric response of the CILE is very stable with more than 99% of the initial activity remaining after 20 s of stirring of a 0.5 mM solution of phenol.     

Ultra trace adsorptive stripping voltammetric determination of atrazine in soil and water using mercury film electrode

In situ mercury film electrode produced in the presence of thiocyanate has been shown extremely useful for highly sensitive adsorptive stripping voltammetric measurements of atrazine down to sub-μg L⁻¹ level. Operational parameters have been optimized and the stripping voltammetric performance has been investigated using square wave scans. The adsorptive stripping response is linear over the range of 0.5-60 μg L⁻¹ atrazine, with a detection limit of 0.024 μg L⁻¹. The method has been applied to the determination of atrazine in soil and water samples.     

Cellulose sulfuric acid catalyzed one-pot three-component synthesis of imidazoazines

Imidazoazines have been synthesized by a one-pot three-component condensation reaction of an aldehyde, a 2-aminoazine and an isocyanide in the presence of the cellulose sulfuric acid, as an effective bio-supported catalyst in excellent yields. The reaction work-up is simple and the catalyst can be easily separated from the product and reused in several times.     

A novel one-pot synthesis of 2-alkylthio-1,3,4-oxadiazoles in water

A facile and one-pot protocol for the synthesis of 2-alkylthio-1,3,4-oxadiazoles is reported. This green method relies on the reaction of acid hydrazides with CS₂ and an alkyl halide. The reaction is carried out under mild and environmentally friendly procedure in water with high to excellent yields. Thirteen different valuable alkylthio-1,3,4-oxadiazoles are synthesized from cheap and easily available CS₂ with this method. This is the first report for the synthesis of 1,3,4-oxadiazoles in water.     

Electrochemical synthesis and mechanestic study of quinone imines exploiting the dual character of N,N-dialkyl-p-phenylenediamines

Two one-pot electrochemical approaches for the synthesis of similar quinone imines via either the nucleophilic character of N,N-dialkyl-p-phenylenediamines or electrophilic reactivity of their oxidized forms through Michael-type addition reactions are reported.