Fabrication and Determination of Refractive Index Profile of the Planar Waveguides by Wedge Technique

Several planar waveguides have been fabricated. The waveguides have been polished for determination of their refractiveindex profiles (RIP) by wedge method. The RIP determined by inserting the sample in a Mach-Zehnder interferometer andapplying fringe analysis methods.     

Modal vibrations of a cylindrical radiator over an impedance plane

The problem of acoustic radiation from an infinite cylinder undergoing harmonic modal surface vibrations near a locally reacting planar boundary is considered. The formulation utilizes the appropriate wave field expansions, the classical method of images, and the translational addition theorem for cylindrical wave functions, along with a simple local surface reaction model involving a complex amplitude wave reflection coefficient applied to simulate the relevant boundary conditions for the given configuration. The analytical results are illustrated with a numerical example in which the cylindrical surface is immersed near a layer of fibrous material set on an impervious rigid wall. The numerical results reveal the important effects of interface local surface reaction and source position on the computed modal impedance component values and the radiated on-axis far-field pressure. The benchmark solution presented can lead to a better understanding of acoustic radiation from near-interface two-dimensional sources, which are commonly encountered problems in outdoor acoustics and noise control engineering. Eventually, it could be used to validate those found by numerical approximation techniques.     

A brief review on structural concepts of novel supramolecular proton transfer compounds and their metal complexes

Our research group has been interested in synthesis of proton transfer compounds as new supramolecular synthons for the onepot preparation of self-assembled transition metal complex-organo-networks since 2000. We have focused on the proton delivery from acids, which are considered as suitable proton donors, to amines as proton acceptors. The results were production of several proton transfer ion pairs possessing some remaining donor sites applied for coordination to metallic centers in preparation of metal-organic structures. Some of the complexes showed contributions of both cationic and anionic fragments of the starting ion pair, while some others contained only one of these species as ligand. Much of the investigations on reviewed compounds focused on the concept of supramolecular systems, co-crystallization, stereochemically active lone pairs, coordination polyhedron and mainly on various interactions involve including van der Waals, ion pairing, hydrogen bondings, face to face π-π stackings and edge to face C-H...π, C-O...π, N-H...π, S-O...π, Ti...π and Hg-Cl...π interactions. The mentioned interactions are the most commonly used strategies in the extension of supramolecular structures.     

Headspace SPME–GC Method for Acetone Analysis and its Biomedical Application

A new method for extraction and analysis of acetone in human urine based on headspace solid phase microextraction using a mixture of activated carbon and zeolite as sorbents in a PVC matrix coated on a silver wire and its application to the determination of ketone bodies is described. Unlike commercial fibers, which are coated on fused silica, the coating adheres strongly to the silver wire and is thermally stable up to 250 °C. After optimization of coating composition and microextraction conditions the fiber was used for the analysis of acetone in human urine.     

An efficient and facile one-step synthesis of highly substituted thiophenes

An efficient one-step method for the synthesis of fully substituted thiophenes, from thiomorpholides and α-halo ketones, was developed. A mechanism has also been proposed for the course of reaction.     

Solid-liquid extraction and preconcentration of trace nickel using 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and TDBA onto benzophenone and determination by atomic absorption spectrometry.

Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples.     

Microwave Assisted Conversion of Oximes and Semicarbazones to Carbonyl Compounds Using Benzyltriphenylphosphonium Peroxymonosulfate

Summary.  Benzyltriphenylphosphonium peroxymonosulfate in the presence of catalytic amounts of bismuth chloride was found to be an efficient and mild reagent for the oxidative cleavage of oximes and semicarbazones to the corresponding carbonyl compounds under microwave irradiation. Corresponding author. E-mail: haji@cc.iut.ac.ir Received March 4, 2002; accepted (revised) April 8, 2002     

Conversion of acids to benzimidazoles with transition metal/zeolites

Transition metal/Y zeolites were prepared using microwave solid state and aqueous solution ion exchange methods. The activity of these zeolites was investigated in a conversion of acids to benzimidazoles reaction between 4-methyl-1, 2-phenylenediamine and 3-nitrobenzoic acid. The yield of these reactions increased in order of CuY < Fe²⁺Y < NiY < CoY < NaY < CrY < MnY < ZnY for both methods. The solid state ion-exchanged zeolites showed higher activity in comparison to the aqueous solution exchange. Yields of products in the presence of the ZnY zeolite were of the order of 69–83%. It seems that the Lewis sites are better sites compared to the Bronsted sites for this reaction.     

Multi-nozzle electrospray system for gas cleaning processes

A multi-nozzle electrospray system was developed as a charged droplet source for cleaning a gas contaminated with fine particles. The efficiency of removal of fine particles from the gas can be significantly increased, as compared to uncharged sprays, when the droplets are electrically charged. In the presented experiments, the spray of the droplets of size lower than 100 μm was charged either positively or negatively. Cigarette smoke was used as a source of submicrometer particles. The suppression of the particle concentration was determined after different time intervals of spraying of water. Further improvement in gas cleaning was obtained after charging the smoke particles using a specially designed corona charger. The efficiency of the cleaning process was similar to that obtained for droplets generated by mechanical atomisers with induction charging, but the electrospraying allowed decreasing the water consumption up to about three times.