A novel fully implicit finite volume method applied to the lid‐driven cavity problem—Part I: High Reynolds number flow calculations

A novel implicit cell‐vertex finite volume method is described for the solution of the Navier–Stokes equations at high Reynolds numbers. The key idea is the elimination of the pressure term from the momentum equation by multiplying the momentum equation with the unit normal vector to a control volume boundary and integrating thereafter around this boundary. The resulting equations are expressed solely in terms of the velocity components. Thus any difficulties with pressure or vorticity boundary conditions are circumvented and the number of primary variables that need to be determined equals the number of space dimensions. The method is applied to both the steady and unsteady two‐dimensional lid‐driven cavity problem at Reynolds numbers up to 10000. Results are compared with those in the literature and show excellent agreement. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and characterization of Ni(II), Zn(II), and Cd(II) complexes with dithiophosphonate derivatives

Ammonium salts of p-methoxyphenyldithiophosphonic acid O-alkyl esters (H₃CO-C₆H₄-(RO)P(S)S⁻NH ₄ ⁺ ; R = C₂H₅,-CH₂CH₂CH₂CH₂-, and cyclopentyl) and their complexes with Ni²⁺, Cd²⁺, and Zn²⁺ were prepared. 2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide, the so-called Lawesson reagent, was treated with the corresponding alcohol to give the O-alkyl ester of the acid. Dry NH₃ was then purged through the solution of this ester to form the ammonium salt of the O-alkyl dithiophosphonic acids. Nickel complexes of these ligands were formed in acetic acid, while zinc and cadmium complexes were formed in water and an ethanol medium, respectively. The geometry of the coordinated atoms was square planar with Ni²⁺ and tetrahedral with Zn²⁺ and Cd²⁺. Using an alkanediol, two dithiophosphonic acids were bridged, thus forming a ligand with four S atoms for coordination. The zinc and cadmium complexes of these tetradentate ligands were also synthesized. The text was submitted by the authors in English.     

Synthesis of pyrimidine Schiff base transition metal complexes: characterization,spectral and electrochemical analyses,and photoluminescence properties

Research on Chemical Intermediates - This study includes the synthesis, characterization, electrochemical analysis and photoluminescence properties of a Schiff base ligand bearing a pyrimidine ring...     

Effect of flow and surface conditions on human lymphocyte isolation using microfluidic chambers

Phenotypically pure subpopulations of lymphocytes can provide valuable insights into the immune response to injury and disease. The isolation of these subpopulations presents unique challenges, particularly when preprocessing incubation to attach fluorescent or antibody tags is to be minimized. This paper examines the separation of T and B lymphocytes from mixtures using microfluidic chambers coated with antibodies, focusing on flow conditions and surface chemistry. The adhesion of both cell types decreases as shear stress increases irrespective of the surface chemistry. The incorporation of poly(ethylene glycol) chains along with the antibodies on the chamber surface is shown to significantly improve the reproducibility of cell adhesion and is thus an important part of the overall system design. Furthermore, this technique is shown to be an effective way of isolating highly pure subpopulations of lymphocytes from model mixtures, even when the target cell concentration is low.     

Pretreatment of corn fiber by pressure cooking in water

The pretreatment of corn fiber using liquid water at temperatures between 220 and 260°C enhances enzymatic hydrolysis. This paper describes the laboratory reactor system currently in use for cooking of corn fiber at temperatures ranging from 200 to 260°C. The corn fiber at approx 4.4% solid/liquid slurry was treated in a 2-L, 304 SS, Parr reactor with three turbine propeller agitators and a Proportional-Integral-Derivative (PID), controller that controlled temperature within ±1°C. Heat-up times to the final temperatures of 220, 240, or 260°C were achieved in 50 to 60 min. Hold time at the final temperature was less than 10 s. A serpentine cooling coil, through which tap water was circulated at the completion of the run, cooled the reactor’s contents to 180°C within 2 min after the maximum temperature was attained. Ports in the reactor’s head plate facilitated sampling of the slurry and monitoring the pH. A continuous pH monitoring system was developed to help observe trends in pH during pretreatment and to assist in the development of a base (2.0M KOH) addition profile to help keep the pH within the range of 5.0 to 7.0. Enzymatic hydrolysis gave 33 to 84% conversion of cellulose in the pretreated fiber to glucose compared to 17% for untreated fiber.     

Pretreatment of yellow poplar sawdust by pressure cooking in water

The pretreatment of yellow poplar wood sawdust using liquid water at temperatures above 220°C enhances enzyme hydrolysis. This paper reviews our prior research and describes the laboratory reactor system currently in use for cooking wood sawdust at temperatures ranging from 220 to 260°C. The wood sawdust at a 6–6.6% solid/liquid slurry was treated in a 2 L, 304 SS, Parr reactor with three turbine propeller agitators and a proportional integral derivative (PID) controller, which controlled temperature within ±1°C. Heat-up times to the final temperatures of 220, 240, or 260°C were achieved in 60–70 min. Hold time at the final temperature was less than 1 min. A serpentine cooling coil, through which tap water was circulated at the completion of the run, cooled the reactor’s contents within 3 min after the maximum temperature was attained. A bottoms port, as well as ports in the reactor’s head plate, facilitated sampling of the slurry and measuring the pH, which changes from an initial value of 5 before cooking to a value of approx 3 after cooking. Enzyme hydrolysis gave 80–90% conversion of cellulose in the pretreated wood to glucose. Simultaneous saccharification and fermentation of washed, pretreated lignocellulose gave an ethanol yield that was 55% of theoretical. Untreated wood sawdust gave less than 5% hydrolysis under the same conditions.     

The changes in transformation temperatures under stress of Cu-12.7Al-5Ni-2Mn alloy

The effects of the stress on shape memory properties of Cu-12.7Al-5Ni-2Mn shape memory alloy have been investigated. Applied stress increases transformation temperatures and the relationship between T₀, temperature at which Gibbs free energy of austenite equals that of martensite, and plastic deformation is linear.     

New and clean synthesis of N-substituted pyrroles under microwave irradiation

N-Substituted homochiral pyrrole derivatives were synthesized by the ring-closure reaction of cis-1,4-dichloro-2-butene with various amine compounds on a silica surface under microwave irradiation.     

Synthesis,Spectroscopic Characterization and Properties of New Metal Complexes

A new series of the polydentate Schiff base Cu^II, Co^II, Ni^II, Pd^II and Zn^II complexes derived from ethylenediamine (eda), diethylenetriamine (dea) and tris(2-aminoethyl)amine (taa) have been prepared by template condensation in MeOH solution, and characterized by i.r., electronic spectral data, elemental analyses, conductivity and magnetic measurements. The ¹H- and ¹³C-n.m.r. and mass spectral data of the Ni^II, Pd^II and Zn^II complexes have been recorded. In all complexes, some of the chloride ions coordinate to the metal ions. From conductivity measurements, it is shown that the complexes are electrolytes. The Ni^II, Pd^II and Zn^II complexes have diamagnetic character. In this study, the Schiff base Cu^II and Co^II complexes have sub-normal magnetic moments commensurate with their binuclear or tetranuclear nature. Some show antimicrobial activity against bacteria and yeast.