A computational study of silicon-doped aluminum phosphide nanotubes

We performed density functional theory (DFT) calculations to investigate the properties of silicon-doped (Si-doped) models of representative (4,4) armchair and (6,0) zigzag aluminum phosphide nanotubes (AlPNTs). The structures were allowed to relax and the chemical shielding (CS) parameters were calculated for the atoms of optimized structures. The results indicated that the band gap energies and dipole moments detect the effects of dopant. The CS parameters also indicated that the Al and P atoms close to the Si-doped region are such reactive atoms, which make the Si-doped AlPNTs more reactive than the pristine AlPNTs. Moreover, replacement of P atom by the Si atom makes AlPNT more reactive than the replacement of Al atom by the Si atom.     

Activated Anilide in Heterocyclic Synthesis: Synthesis of New Dihydropyridines,Dihydropyridazines and Thiourea Derivatives

A series of new dihydropyridines, butanamide, dihydropyridazines and thiourea derivatives have been prepared through the reactions of 3‐aminopyridine ( 1 ) and N‐(pyridin‐3‐yl)‐3‐(pyridin‐3‐ylimino)butanamide 3 with some electrophilic reagents, aryl diazonium salts and isothiocyanates. Elementary analysis, MS, IR, and ¹H NMR spectra confirmed the identity of the products.     

Synthesis and optical properties of poly (vinyl acetate)/bismuth oxide nanorods

Poly (vinyl acetate) (PVAc) loaded bismuth oxide (Bi₂O₃) nanorods were successfully prepared at ambient pressure. X‐ray diffraction (XRD) and transmission electron microscopy were used to characterize the final product. It was found that Bi₂O₃ nanorods were formed and the diameter of the rods was confined to about 8 nm. The diameter and length of formed rods were found to increase by increasing the bismuth oxide concentration in the PVAc matrix. The optical properties of the nanocomposite films were characterized from the analysis of the experimentally recorded transmittance and reflectance data in the spectral wavelength range of 300–800 nm. The values of some important parameters of the studied films are determined such as refractive index (n), extinction coefficient (k), optical absorption coefficient (α), and band energy gap (E_g). According to the analysis of dispersion curves, it has been found that the dispersion data obeyed the single oscillator of the Wemple–DiDomenico model, from which the dispersion parameters and high‐frequency dielectric constant were determined. In such work, from the transmission spectra, the dielectric constant (ε_∞) and the third‐order optical nonlinear susceptibility χ⁽³⁾ were determined. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous spectrophotometric determination of metformin hydrochloride and glibenclamide in binary mixtures using combined discrete and continuous wavelet transforms

In this work, a combined discrete and continuous wavelet transform analysis was developed for simultaneous spectrophotometric determinations of metformin hydrochloride and glibenclamide, two antidiabetic drugs, in binary mixtures without any chemical pretreatment. Absorption spectra were subjected to the 4-level db4 discrete wavelet transform (DWT) for signal de-noising. Selected continuous wavelet transform (CWT) families (rbio3.1 with scaling factor, a = 80, and gaus2, a = 60) were applied on these de-noised signals. Finally, a zero-crossing technique was used for the construction of calibration curves for both drugs. The proposed method was validated by analyzing synthetic mixtures of the investigated drugs with various concentrations. The amount of metformin hydrochloride and glibenclamide were determined by using CWT amplitudes in zero-crossing points. The mean recovery values of metformin hydrochloride and glibenclamide were found between 98.6-102.0 and 97.9-102.4% for rbio3 and 98.3-101.2 and 97.1-101.4% for gaus2 families, respectively. The obtained results showed that the developed method is a simple, rapid and precise procedure for the simultaneous determination of metformin hydrochloride and glibenclamide in binary mixtures.     

Spectrofluorimetric Assessment of Doxycycline Hydrochloride in Pharmaceutical Tablets and Serum Sample Based on the Enhancement of the Luminescence Intensity of the Optical Sensor Sm<Superscript>3+</Superscript> Ion

A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably enhance the luminescence intensity of the Sm³⁺ ion in Sm³⁺- DC complex at λ_ex = 400 nm. The produced luminescence intensity of Sm³⁺- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic range for the determination of DC is 1 × 10⁻⁸ – 5 × 10⁻⁶ mol L⁻¹ and in case of quantum yield calculations is 7 × 10⁻⁹ – 5 × 10⁻⁶ mol L⁻¹ with detection limit of 6.5 × 10⁻¹⁰ mol L⁻¹. The enhancement mechanism of the luminescence intensity in the Sm³⁺- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which Eu³⁺ ion is used instead of Sm³⁺ ion is also studied.     

On Some Finitary Conditions Arising from the Axiomatisability of Certain Classes of Monoid Acts

This article considers those monoids S satisfying one or both of the finitary properties (R) and (r), focussing for the most part on inverse monoids. These properties arise from questions of axiomatisability of classes of S-acts, and appear to be of interest in their own right. If S is weakly right noetherian (WRN), that is, S has the ascending chain condition on right ideals, then certainly (r) holds. Other than this, we show that (R), (r), and (WRN) are independent. Our most detailed results are for Clifford monoids, in which case we completely characterise those S with trivial structure homomorphisms satisfying (R) or (r).     

Analysis of a generalized Friedman’s urn with multiple drawings

We study a generalized Friedman’s urn model with multiple drawings of white and blue balls. After a drawing, the replacement follows a policy of opposite reinforcement. We give the exact expected value and variance of the number of white balls after a number of draws, and determine the structure of the moments. Moreover, we obtain a strong law of large numbers, and a central limit theorem for the number of white balls. Interestingly, the central limit theorem is obtained combinatorially via the method of moments and probabilistically via martingales. We briefly discuss the merits of each approach. The connection to a few other related urn models is briefly sketched.     

Characterization of Gafchromic EBT3 films for ultraviolet radiation dosimetry

A newly released processless Gafchromic EBT3 film was investigated for its response to ultraviolet radiation (UVR) at three different wavelengths: 365 (UVA), 302 (UVB) and 254 nm (UVC). The change in the film's optical density was dependent on the radiance exposure and UV wavelength and was found to correlate with the UV intensity. The dynamic range of the EBT3 films is ～5 to ～60 J/cm² for UVA and UVB and ～5 to ～300 J/cm² for UVC. The dose sensitivity of EBT3 films for UVA and UVB radiation was approximately 10 times higher than that for UVC radiation. The results indicate the suitability of EBT3 films for quantitative and qualitative measurements of UVR exposure.     

Aptamer‐Assisted Assembly of Gold Nanoframe Dimers

The assembly of nanoframe dimers assisted by aptamer‐functionalized smaller spherical gold nanoparticles as prospective surface‐enhanced Raman scattering (SERS) biotraps for riboflavin, an important molecule for biological electron transfer reactions, is reported. In this approach, the aptamer‐coated gold nanoparticles designed for selective binding of riboflavin also serve as the electrostatic driver for nanoframe dimerization in dilute solutions. The gold nanoframe dimers provide unique conditions for plasmonic coupling in a hot spot with sufficient space for the binding of bulky biomolecules. The use of an aptamer allows for highly selective binding of the targeted analyte as compared with conventional organic ligands with excellent low detection limit of one micromole of riboflavin.