Modeling of Compressible Cake Filtration

The transport of suspended solid particles in a liquid through porous media has importance from the viewpoint of engineering practice and industrial applications. Deposition of solid particles on a filter cloth or on a pervious porous medium forms the filter cakes. Following a literature survey, a governing equation for the cake thickness is obtained by considering an instantaneous material balance. In addition to the conservation of mass equations for the liquid, and for suspended and captured solid particles, functional relations among porosity, permeability, and pressure are obtained from literature and solved simultaneously. Later, numerical solutions for cake porosity, pore pressure, cake permeability, velocity of solid particles, concentration of suspended solid particles, and net rate of deposition are obtained. At each instant of time, the porosity decreases throughout the cake from the surface to the filter septum where it has the smallest value. As the cake thickness increases, the trends in pressure variation are similar to data obtained by other researchers. This comparison shows the validity of the theory and the associated solution presented. A sensitivity analysis shows higher pressure values at the filter septum for a less pervious membrane. Finally, a reduction in compressibility parameter provides a thicker cake, causes more particles to be captured inside the cake, and reduces the volumetric filtrate rate. The increase of solid velocity with the reduction in compressibility parameter shows that more rigid cakes compress less.     

Electrochemical synthesis of conducting polymers from oligomers containing thiophene and furan rings

Oligomers containing 2,5-thienylene and 2,5-furanylene units were synthesized by NiCl₂ (dppp) (dppp = Ph₂PCH₂CH₂CH₂PPh₂) coupling of Grignard compounds with the appropriate bromothiophene or bromofuran; UV and electrochemical data are given and discussed in terms of number and kind of heterolene units in the oligomeric species.     

Simultaneous determination of cadmium and zinc using a fiber optic device and fluorescence spectrometry

A reservoir type of optode is described for simultaneous and remote determination of Cd and Zn using [9-(1',4',7',10',13'-pentaazacyclopentadecyl)methylanthracene] as the fluorophore. Simultaneous analysis was achieved by the significant perturbation in the fluorescence spectrum of the Cd-ligand complex while the Zn complex only results in enhancement in the fluorescence intensity as compared to ligand alone. The ion permeability of several membranes were examined; Nafion and cellophane were used for the construction of the optode. Using the optode constructed with cellophane, for 20 min immersion time, the 3-s detection limits were found to be 4.5 mug l(-1) for Cd and 0.6 mug l(-1) for Zn.     

Ureasulfonamide Polymeric Sorbent for Selective Mercury Extraction

A new polymeric resin with sulfonamide pendant functions has been prepared for the selective extraction of mercuric ions. This polystyrene sulfonamide urea resin with a 3.5 mmol/g total nitrogen content is able to selectively sorb mercury from aqueous solutions. The mercury sorption capacity of the resin is around 1.60 mmol/g under non-buffered conditions. The experiments performed under identical conditions with some metal ions reveal that Cd(II), Pb(II), Zn(II), and Fe(III) ions are also extractable in low quantity (0.05–0.1 mmol/g). The sorbed mercury can be eluted by repeated treatment with hot acetic acid without hydrolysis of the amide groups.     

A new synthetic route to the synthesis of nordasycarpidone derivatives

A new synthetic route for the synthesis of the nordasycarpidone derivative 11 which has hexahydro‐1,5‐methanoazocino[4,3‐b]indol skeleton, is described. Construction of the tetracyclic structure was achieved by catalytic reduction and cyclization reaction of the nitrile derivative. Also many new tetrahydrocarbazole derivatives ( 4, 5, 6, 7, 8, 9 ) and a dasycarpidol derivative ( 10 ) were synthesized.     

6‐(2‐Fluorobenzylidene)‐2‐[1‐(2‐fluoro‐4‐biphenyl)ethyl]thiazolo[3,2‐b][1,2,4]triazol‐5(6H)‐one

The title compound, C₂₅H₁₇F₂N₃OS, was synthesized from 6‐(benzyl­idene)­thia­zolo­[3,2‐b][1,2,4]triazol‐5(6H)‐one. The fused thia­zolo­[3,2‐b][1,2,4]triazole system is essentially planar, and bifurcated C—H⋯O, C—H⋯N and C—H⋯F interactions are present between mol­ecules.     

Preparation of a New Polymeric Surfactant for Emulsion Polymerization

The stability of polymeric dispersions is a property of practical importance and hence, the search for an optimized strategy to equip polymer dispersions with sufficient stability is a matter of continuous research during the last years. The kernel is to reach a sufficient stability, as it is required during polymerization, conditioning, or storage and to allow coagulation or coalescence of particles when it is needed, such as during separation of polymer from latex or during film formation. In this study, the emulsion homopolymerization system containing vinyl acetate, potassium persulfate, new polymeric surfactant, NaHCO₃ and water was studied in the classical glass emulsion polymerization reactor. The effects of new polymeric emulsifier on the physicochemical properties of obtained vinyl acetate latex properties were investigated depending on vinyl acetate percentage in homopolymerization.     

Ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst

The ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst (WCl₆? e^?? Al? CH₂Cl₂) is described. In addition, the influence of reaction conditions on the polymerization yield was determined. The resulting polymer has been characterized by NMR, IR, gel permeation chromatography and differential scanning calorimetry. The glass transition temperature and melting point of the polydodecenamer are 19.6°C and 70.0°C respectively. Furthermore, cyclododecene has been polymerized into a low‐molecular‐weight polymer (12.0 × 10³) with a polydispersity of 2.06 in high yields (94%). IR and NMR analysis indicate that the polydodecenamer has a high trans content (60%). Copyright © 2004 John Wiley & Sons, Ltd.     

Searching threshold effects in the interest rate: An application to Turkey case

This paper investigates the behaviour of interest rates in Turkey using a two-regime TAR model with an autoregressive unit root. This method recently developed by Caner and Hansen [Threshold autoregression with a unit roots, Econometrica 69 (6) (2001) 1555–1596] allows to simultaneously consider non-stationarity and non-linearity. Our finding indicates that the interest rate is a non-linear series and is characterized by a unit root process over the period 1990:1–2006:5.