Use of Reaction between Melamine and Bioxalate Ions for Monitoring Melamine Content of Petrochemical Wastewater

This study describes a turbidimetric technique for determination of melamine in wastewater of petrochemical companies. A single reagent (bioxalate ions) is used and an insoluble ion‐pair (melamine:bioxalate 1:3) produced. The reproducibility of the method is excellent and relative standard deviation for six repeated experiments is 1.5%. An interferences study was carried out, and it was found that the common species occurring in wastewater has no interference effect on the determination of melamine. The interference effect of Al³⁺ was eliminated by its precipitation as Al(OH)₃ at pH 7. Finally this method was successfully used in the determination of melamine content of Urmia Petrochemical Company, a local melamine producer.     

BOOK REVIEWS

Book reviewed in this article: The Geometric Supposer: What Is It A Case Of? , Edited by Judah L. Schwartz, Michal Yerushalmy, and Beth Wilson. Profiles of Ecologists: Results of a Survey of the Membership of the Ecological Society of America , Marjorie M. Holland, David M. Lawrence, Deborah J. Morrin, Carol Hunsaker, David Ianoye, Anthony Janetos, H. Ronald Pulliam, William Robertson, and John Wilson. Garbage , Maria Fleming.     

BOOK REVIEWS

Book reviewed in this article: Talking Points in Mathematics : Author. Anita Straker and Sheryl A. Maxwell Eyewitness Science: Time & Space : Author. John and Mary Gribbin and Donna M. Plummer Look Inside Cross-sections Space See Inside 12 Fascinating Spacecraft : Author. Moira Butterfield and Donna M. Plummer The Big Book of Things That Go: Project Editor . Caroline Bingham and Donna M. Plummer Proceedings of the 7th International Congress on Mathematical Education: Editors . Claude Gaulin, Bernard R. Hodgson, David H. Wheeler, and John C. Egsgard Selected Lectures from the 7th International Congress on Mathematical Education: Editors . David F. Robitaille, David H. Wheeler, and Carolyn Kieran     

Highly Efficient,Four Component,One-pot Synthesis of Tetrasubstituted Imidazoles Using a Catalytic Amount of FeCl<Subscript>3</Subscript> · 6H<Subscript>2</Subscript>O

Summary. An efficient and improved procedure for the synthesis of tetrasubstituted imidazoles by FeCl₃ · 6H₂O catalyzed four-component one-pot synthesis in refluxing ethanol is described.     

BOOK REVIEWS

Book reviewed in this article: Investigating Mathematics with Young Children . Author, Rosemary Althouse. Implementing the Mathematics Standards in Grades K-4, Monographs 1, 2, and 3 . Editor and Purchase Contact, Robert Underbill.     

Preparation of Co3O4 nanoparticles by nonhydrolytic thermolysis of [Co(Pht)(H2O)]n polymers

Benzenedicarboxylate complexes, especially phthalate ones, can be significant precursors for the preparation of nano-sized metal and metal oxides. The injection of organic surfactants such as oleic acid (OA) and triphenylphosphine into molecular precursors has yielded samples with size control, narrow size distributions and crystallinity of individual nanocrystals. Fourier transform infrared and X-ray photoelectron spectroscopy revealed that the OA molecules were adsorbed on the ferromagnetic nanoparticles by chemisorption. The temperature-dependent magnetization curve in zero-field-cooled and field-cooled exhibit weak ferromagnetism of the Co₃O₄ nanoparticles. At 300 K the remanent magnetization is 0.02 emu/g, the coercive field is 441 Oe and the magnetization at saturation is 1.05 emu/g.     

Tunable optical filter based on Sagnac phase-shift using single optical ring resonator

In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate theoretically a novel narrow band optical filter response that is based on Sagnac phase-shift Δφ. The given filter structure permits the Sagnac rotation to control the filter response. It is shown that by changing the Sagnac rotation rate, we can tune the filter response for desired bandwidths. To increase the wavelength selectivity of the filter, the Sagnac phase-shift should be as small as possible that is limited by the loop length. For Δφ=0.1 rad, the obtained FWHM is 2.63 MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.     

Consistency of a nonparametric conditional quantile estimator for random fields

Given a stationary multidimensional spatial process (Z _i = (X _i , Y _i ) ∈ ℝ ^d × ℝ, i ∈ ℤ ^N ), we investigate a kernel estimate of the spatial conditional quantile function of the response variable Y _i given the explicative variable X _i . Almost complete convergence and consistency in L ^2r norm (r ∈ ℕ*) of the kernel estimate are obtained when the sample considered is an α-mixing sequence.     

Some generalizations of torsion-free Crawley groups

In this paper we investigate two new classes of torsion-free Abelian groups which arise in a natural way from the notion of a torsion-free Crawley group. A group G is said to be an Erd?s group if for any pair of isomorphic pure subgroups H,K with G/H ? G/K, there is an automorphism of G mapping H onto K; it is said to be a weak Crawley group if for any pair H,K of isomorphic dense maximal pure subgroups, there is an automorphism mapping H onto K. We show that these classes are extensive and pay attention to the relationship of the Baer-Specker group to these classes. In particular, we show that the class of Crawley groups is strictly contained in the class of weak Crawley groups and that the class of Erd?s groups is strictly contained in the class of weak Crawley groups.