ZrCl4-Catalyzed C-O Bond to C-N Bond Formation: Synthesis of 1,2,3-Triazoles and Their Biological Evaluation

A simple and efficient protocol was developed for the synthesis of aryl azides directly from aryl carbinols using ZrCl₄ as a Lewis acid catalyst. The azides were converted to novel triazoles under click reaction conditions, which were evaluated for their antimicrobial activity against various strains.     

A Parallel Projection for the Multicommodity Network Model

We present an application of parallel computing techniques to the solution of a quadratic programme that arises in the resource-directive decomposition method for multicommodity problems. A sequential algorithm for the quadratic programme is discussed, and its extension to a parallel implementation is given. Computational testing of the sequential and parallel algorithms was done on the Sequent Symmetry S81 parallel computer located in the Parallel Processing Laboratory at Southern Methodist University. On several large test problems the parallel version achieved a speed-up of 10 with 12 processors.     

Determination of critical micelle concentration with the rotating sample system

A novel experimental approach using the rotating sample system (RSS) is proposed here for the determination of the critical micelle concentration (CMC) of surfactants. The RSS has been conceived in our laboratory as a convection platform for physicochemical studies and analyses in microliter-sized sample drops. The scheme allows for vigorous rotation of the drop despite its small size through efficient air-liquid mechanical coupling. Thus, changes in surface properties of aqueous samples result in corresponding modulation of the hydrodynamic performance of the RSS, which can be utilized to investigate interfacial phenomena. In this work, we demonstrate that the RSS can be used to study the effects of surfactants on the surface and in the bulk of very small samples with hydrodynamic electrochemistry. Potassium ferrocyanide is employed here with cyclic voltammetry to probe the air-water interface of solutions containing Triton X-100. The CMC of this surfactant determined using this approach is 140 ppm, which agrees well with reported values obtained with conventional methods in much larger samples. The results also demonstrate that besides the CMC, variations in bulk rheological properties can also be investigated in very small specimens using the RSS with a simple method.     

Highly Selective and Sensitive Aggregation-Induced Emission of Fluorescein-Coated Metal Oxide Nanoparticles

We report the synthesis, characterization, and photophysical properties of novel metal oxide nanoparticles (NPs) coated with specially designed fluorescein substituents which are capped with electron-withdrawing groups. The fluorescein-coated nanoparticles were synthesized in excellent yields, and their structures were confirmed using various advanced spectroscopic, instrumental, and surface analysis techniques, revealing the formation of the target functionalized nanoparticles (FNPs) which show superior chemical and thermal stabilities. In addition, the photophysical properties of the FNPs were examined using UV-visible absorption and fluorescence spectroscopy. These latter techniques disclosed aggregation-induced emission (AIE) properties for most of the target FNPs, namely those which are soluble in common organic solvents at selective concentration ranges of water fractions in the solvent mixture.     

Identification and Quantitation of Malonic Acid Biomarkers of In-Born Error Metabolism by Targeted Metabolomics

Malonic acid (MA), methylmalonic acid (MMA), and ethylmalonic acid (EMA) metabolites are implicated in various non-cancer disorders that are associated with inborn-error metabolism. In this study, we have slightly modified the published 3-nitrophenylhydrazine (3NPH) derivatization method and applied it to derivatize MA, MMA, and EMA to their hydrazone derivatives, which were amenable for liquid chromatography- mass spectrometry (LC-MS) quantitation. 3NPH was used to derivatize MA, MMA, and EMA, and multiple reaction monitoring (MRM) transitions of the corresponding derivatives were determined by product-ion experiments. Data normalization and absolute quantitation were achieved by using 3NPH derivatized isotopic labeled compounds ¹³C₂-MA, MMA-D₃, and EMA-D₃. The detection limits were found to be at nanomolar concentrations and a good linearity was achieved from nanomolar to millimolar concentrations. As a proof of concept study, we have investigated the levels of malonic acids in mouse plasma with malonyl-CoA decarboxylase deficiency (MCD-D), and we have successfully applied 3NPH method to identify and quantitate all three malonic acids in wild type (WT) and MCD-D plasma with high accuracy. The results of this method were compared with that of underivatized malonic acid standards experiments that were performed using hydrophilic interaction liquid chromatography (HILIC)-MRM. Compared with HILIC method, 3NPH derivatization strategy was found to be very efficient to identify these molecules as it greatly improved the sensitivity, quantitation accuracy, as well as peak shape and resolution. Furthermore, there was no matrix effect in LC-MS analysis and the derivatized metabolites were found to be very stable for longer time.

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Molecular structure and conformation study of p-[N,N-bis(2-Chloroethyl)amino] benzaldehyde-4-phenyl thiosemicarbazone

The crystal structure of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde-4-phenyl thiosemicarbazone(CEAB-4-PTSC) is described. The compound crystallizes in the monoclinic crystal system, P21/c space group, Z = 4, calculated density = 1.327 mg/cm³, V = 1978.2(6) ?³ with unit cell parameters a = 16.240(3) ?, b = 12.821(2) ?, c = 9.8543(16) ?, ?? = 105.382(6)°. The crystal structure reveals that the compound exists in the thione form and S1 and N2 are at trans-conformation to each other with respect to the N3-C12 bond. The packing of molecules in the crystal lattice is stabilized by intramolecular hydrogen bonds.     

Application of a He3Ne infrared laser source for detection of geometrical dimensions of cracks and scratches on finished surfaces of metals

In this study, the authors addressed a new method of measurement for microscratches and cracks on finished metallic surfaces. The technology proposed here can be used in aviation, automobile, machine-tools, bearings, electrical and thermal devices (detection of electrical and thermal contact resistance), and many other industrial fields where finished surfaces have to be inspected for quality before use. The technology is based on the application of He3Ne laser optics. This measurement method allows for the inspection of geometrical parameters such as depth and width of scratches and cracks and consists of a low-energy He3Ne red laser beam (wavelength 633 nm) with a cross-section of 0.48 mm, beam expander with special designed slit, multi-axis stage with sample holder and CCD (charge-coupled device) visual detection system. Using experimental data, a mathematical algorithm was created in order to calculate the depths and widths of the scratches and cracks where the method of center of gravity (centroid) of the imaged area was used. The results showed a good correlation between the experimental and calculated values of the dimensions of the scratches. Future work will deal with the determination of the geometrical dimensions of microcracks.     

New approach to the inspection of cooling holes in aero-engines

This paper explores a new design for inspecting turbine blade cooling holes. Cooling holes have been incorporated in the design of turbine blades to combat and avert blade failure caused by excessive operating temperatures. In the paper, we examine the inspection techniques currently in use and present a novel optical technique as an alternative. Our design consists of two stages of inspection, each optically based. In the first stage, a sample is mounted on an XY micro-positioning stage, a vision system captures an image of the sample and displays the size and shape of each entrance hole. To measure the presence of a bottom, a second XYZ inspection stage is used. Using a small collimating tube, a micro-beam illuminates a drilled hole in a pre-programmed fashion. Depending on the level of reflected intensity and where it occurs, the presence of a hole's bottom is determined. The optical inspection system consists of a laser, motorized micro-positioning stages, collimating tubes, vision system, data acquisition software and a customized fixture for manipulating the samples.     

Strongly indexable graphs and applications

In 1990, Acharya and Hegde introduced the concept of strongly k-indexable graphs: A (p,q)-graph G=(V,E) is said to be strongly k-indexable if its vertices can be assigned distinct numbers 0,1,2,…,p−1 so that the values of the edges, obtained as the sums of the numbers assigned to their end vertices form an arithmetic progression k,k+1,k+2,…,k+(q−1). When k=1, a strongly k-indexable graph is simply called a strongly indexable graph. In this paper, we report some results on strongly k-indexable graphs and give an application of strongly k-indexable graphs to plane geometry, viz; construction of polygons of same internal angles and sides of distinct lengths.