Hydrodynamic limit for attractive particle systems on 417-1417-1417-1

We study the hydrodynamic behavior of asymmetric simple exclusions and zero range processes in several dimensions. Under Euler scaling, a nonlinear conservation law is derived for the time evolution of the macroscopic particle density.Research supported by NSF Grant No. DMS-8806731. Present address: Department of Mathematics, University of California at Berkeley, Berkeley, CA 94720, USA     

Application of manganese(IV) dioxide microcolumn for determination and speciation of nitrite and nitrate using a flow injection analysis-flame atomic absorption spectrometry system

A flow injection (FI) method with flame atomic absorption spectrometry (FAAS) detection was developed for the determination and speciation of nitrite and nitrate in foodstuffs and wastewaters. The method is based on the oxidation of nitrite to nitrate using a manganese(IV) dioxide oxidant microcolumn where the flow of the sample through the microcolumn reduces the MnO₂ solid phase reagent to Mn(II), which is measured by FAAS. The absorbance of Mn(II) are proportional to the concentration of nitrite in the samples. The injected sample volume was 400 μL with a sampling rate of analyses was 90 h⁻¹ with a relative standard deviation better than 1.0% in a repeatability study. Nitrate is reduced to nitrite in proposed FI-FAAS system using a copperized cadmium microcolumn and analyzed as nitrite. The calibration curves were linear up to 20 mg L⁻¹ and 30 mg L⁻¹ with a detection limit of 0.07 mg L⁻¹ and 0.14 mg L⁻¹ for nitrite and nitrate, respectively. The results exhibit no interference from the presence of large amounts of ions. The method was successfully applied to the speciation of nitrite and nitrate in spiked natural water, wastewater and foodstuff samples. The precision and accuracy of the proposed method were comparable to those of the reference spectrophotometric method.     

HEXAMETHYLDISILAZANE IN THE PRESENCE OF N,N′,N″,N‴-TETRAMETHYLTETRA-2,3-PYRIDINOPORPHYRAZINATO COPPER (II) IS A NEW,MILD AND HIGHLY EFFICIENT REAGENT FOR SILYLATION OF ALCOHOLS AND PHENOLS

Alcohols and phenols are protected with hexamethyldisilazane in the presence of N,N′,N′,N?-tetramethyletra-2,3-pyridinoporphyrazinato copper (II) in good-to-excellent yields at room temperature.     

In situ crystallization of ZnAl2O4/ZnO nanocomposite on alumina granule for photocatalytic purification of wastewater

Research on Chemical Intermediates - ZnAl2O4/ZnO nanocomposites with different ZnO (20, 30, and 40 mol%) concentrations and coated samples on supports were successfully prepared through...     

Sono-chemical synthesis and characterization of Fe3O4@mTiO2-GO nanocarriers for dual-targeted colon drug delivery

Research on Chemical Intermediates - In this study, a kind of magnetic Fe3O4@mTiO2-GO (where m was shorted mesoporous) hybrids with core–shell nano-structure for controlled dual targeted drug...     

Influence of non-metallic atoms on the absorption of amphetamines on B12N12 nano-cages

Structural Chemistry - Density functional theory (DFT) calculations at B3LYP/6-31+G(d) level were employed to investigate the influence of the non-metal encapsulation of the second row of the...     

Silica Chromate as a Novel Oxidizing Agent for the Oxidation of 1,4‐Dihydropyridines

Silica chromate easily converts 1,4‐dihydropyridines to their corresponding pyridines in the presence of NaHSO₄ · H₂O and wet SiO₂ in dichloromethane at room temperature in good to excellent yields.     

Preparation and characterization of cellulose-ZnO nanocomposite based on ionic liquid ([C4mim]Cl)

Cellulose-ZnO composite was achieved by microwave assisted dissolution of cellulose in ionic liquid 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) followed by addition of premixed ground of Zn(CH₃COO)₂·2H₂O and NaOH. Surface characterization, optical property and thermal stability of nanocomposite were determined by X-ray diffraction, scanning electron microscopy (SEM), UV–Vis spectroscopy and thermo gravimetric analysis. XRD patterns showed the ZnO in polymer matrix has the wurtzite structure. Presence of zinc oxide nanoparticles and cellulose fibers in the composites were observed by SEM. Band-edge transition of zinc oxide in the nanocomposite occurs in lower wavelength than bulk zinc oxide. Thermal stability of nanocomposite was lower than regenerated cellulose due to catalyst behavior of zinc oxide nanoparticles in cellulose matrix.     

A Stochastic Model Associated with Enskog Equation and Its Kinetic Limit

 We examine a system of particles in which the particles travel deterministically in between stochastic collisions. The collisions are elastic and occur with probability ɛ ^d when two particles are at a distance σ. When the number of particles N goes to infinity and Nɛ ^d goes to a nonzero constant, we show that the particle density converges to a solution of the Enskog Equation. Received: 29 January 2002 / Accepted: 30 July 2002 Published online: 14 November 2002 RID="*" ID="*" Research supported in part by NSF Grant DMS-0072666     

Crystal Structure of the Second Polymorph of Octaethylporphyrin Iron(III) with Monoanion 1,4-Phenyldicyanamide, [Fe(OEP)(DicydH)]

Abstract  

Molecular structure of the second polymorph of [Fe(OEP)(DicydH)], where OEP is the dianion of octaethylporphyrin and DicydH = monoanion of 1,4-phenyldicyanamide, was determined by single-crystal X-ray diffraction. Fe(III) atom is five-coordinate to four N atoms of the porphyrin ring and to one nitrogen atom of DicydH. The compound is characterized by an average Fe–N_p bond length of 2.057 ?. The Fe–N_ax bond distance is 1.969(6) ?. Crystal data: crystal system, orthorhombic, a = 15.048(2), b = 17.515(3), c = 29.440(4) ?, space group, Pcab, V = 7759(2) ?³, Z = 8.