Hybride process,microfiltration-electroperoxidation,for water treatment

Cross-flow microfiltration through a 0.8 μm inorganic tubular membrane was enhanced by coupling with a two electrode electrolysis cell producing hydrogen peroxide at high rate, without adding any chemical, by use of carbon felt cathode and dimensional stabilised anode (titanium coated with RuO₂). Anodic oxygen and transfer from atmosphere supplied the required oxygen. The current should be maintained under a maximum value to avoid peroxide reduction. This electrochemical process, called electroperoxidation, upgraded the water quality by removing contaminants that limit mass transport through the membrane, i.e. turbidity, dissolved organic carbon (DOC) and microorganisms. Transient filtration was adjusted to an internal clogging model whose coefficient decreased at the same rate as DOC. The microfiltration steady state flux was multiplied by a factor proportional to the peroxide concentration introduced in the filtration loop. The induced resistance decreased simultaneously with chemical oxygen demand and 254 nm absorbance. Steady state fluxes 2.5 times higher than without treatment were experimentally obtained.     

Landau theory for isotropic,nematic, smectic-A,and smectic-C phases

ABSTRACT

We use the Landau theory of phase transitions to describe the phase diagram of a liquid crystal displaying the isotropic (i), nematic (N), smectic-A and smectic-C phases. The order parameter of the smectic-C phase is defined as the projection of the director on the plane of the smectic layers, vanishing in the smectic-A phase. We present a detailed phase diagram that shows transition between any two of these phases, containing a triple point INA, a Lifshitz point NAC, a tricritical at the NA line, and a critical end point IAC. As one approaches the NC line from the smectic-C phase, the tilt angle approaches a nonzero value, but if the AC line is approached, the tilt angle vanishes according to the distance to the AC line to the power 1/2.     

Anisometric,non-mesogenic,tailor-made monomer for reverse-mode shutters

Reverse-mode operation films can be achieved with polymer dispersed liquid crystals by many methods. One method consists in the use of either rough or polyimide treated supports in order to induce homeotropic alignment of the initial mixture that will separate in liquid crystal and polymer rich phases. The major disadvantage is the need for mesogenic monomers to keep a good alignment of the liquid crystal after the polymerization process. In this paper we present results concerning the use of an anisometric, non-mesogenic, tailor-made monomer for the preparation of excellent reverse-mode polymer dispersed liquid crystal shutters cast on rough surfaces. The combined use of rough surfaces and non-mesogenic monomers allows us to exceed earlier limits in physical and chemical properties, cost, and device dimensions by the use of a wider class of monomer molecules.     

Call for Nominations for 2002 NATAS Awards,Mettler-Toledo Award,Perkin Elmer Award

Journal of Thermal Analysis and Calorimetry -     

A single-step, mild, neutral, catalyst-free method for cyanohydrin synthesis

Abstract  

A wide variety of carbonyl compounds can be transformed to their corresponding cyanohydrins in a single step using a dimethyl sulfoxide (DMSO)–water system in excellent yields (75–94%). The major advantages of this system are that the reaction conditions are mild and neutral; the reaction proceeds without catalyst and gives the corresponding cyanohydrins in short time (15–120 min).     

MAMT,a new chromogenic reagent for Ru,Rh, Pd,Pt and Au in TLC,and for their evaluation by ring colorimetry

Summary Micro-analytical separations of some platinum metals [Ru(III), Rh(III), Pd(II), Pt(IV), and Au(III)] in mixed solutions of their salts have been carried out by ascending thin layer chromatography on Silica Gel G. 3-Mercapto-4-amino-5-methyl-1,2,4-triazole (MAMT) has been successfully used for the visualisation of the above ions on TLC plates and also for colorimetric evaluation of the chromatographed species by ring colorimetry.MAMT=3-Mercapto-4-amino-5-methyl-1,2,4-triazole     

Transferable potentials for phase equilibria. 8. United-atom description for thiols, sulfides, disulfides, and thiophene

An extension of the transferable potentials for phase equilibria united-atom (TraPPE-UA) force field to thiol, sulfide, and disulfide functionalities and thiophene is presented. In the TraPPE-UA force field, nonbonded interactions are governed by a Lennard-Jones plus fixed point charge functional form. Partial charges are determined through a CHELPG analysis of electrostatic potential energy surfaces derived from ab initio calculations at the HF/6-31g+(d,p) level. The Lennard-Jones well depth and size parameters for four new interaction sites, S (thiols), S(sulfides), S(disulfides), and S(thiophene), were determined by fitting simulation data to pure-component vapor-equilibrium data for methanethiol, dimethyl sulfide, dimethyl disulfide, and thiophene, respectively. Configurational-bias Monte Carlo simulations in the grand canonical ensemble combined with histogram-reweighting methods were used to calculate the vapor-liquid coexistence curves for methanethiol, ethanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, 2-butanethiol, pentanethiol, octanethiol, dimethyl sulfide, diethyl sulfide, ethylmethyl sulfide, dimethyl disulfide, diethyl disulfide, and thiophene. Excellent agreement with experiment is achieved, with unsigned errors of less than 1% for saturated liquid densities and less than 3% for critical temperatures. The normal boiling points were predicted to within 1% of experiment in most cases, although for certain molecules (pentanethiol) deviations as large as 5% were found. Additional calculations were performed to determine the pressure-composition behavior of ethanethiol+n-butane at 373.15 K and the temperature-composition behavior of 1-propanethiol+n-hexane at 1.01 bar. In each case, a good reproduction of experimental vapor-liquid equilibrium separation factors is achieved; both of the coexistence curves are somewhat shifted because of overprediction of the pure-component vapor pressures.     

Thermodynamic, dynamic, structural, and excess entropy anomalies for core-softened potentials

Using molecular dynamic simulations, we study three families of continuous core-softened potentials consisting of two length scales: a shoulder scale and an attractive scale. All the families have the same slope between the two length scales but exhibit different potential energy gap between them. For each family three shoulder depths are analyzed. We show that all these systems exhibit a liquid-liquid phase transition between a high density liquid phase and a low density liquid phase ending at a critical point. The critical temperature is the same for all cases suggesting that the critical temperature is only dependent on the slope between the two scales. The critical pressure decreases with the decrease of the potential energy gap between the two scales suggesting that the pressure is responsible for forming the high density liquid. We also show, using the radial distribution function and the excess entropy analysis, that the density, the diffusion, and the structural anomalies are present if particles move from the attractive scale to the shoulder scale with the increase of the temperature indicating that the anomalous behavior depends only in what happens up to the second coordination shell.     

Solvate Ionic Liquids for Li,Na, K,and Mg Batteries

From the viewpoint of element strategy, non‐Li batteries with promising negative and positive electrodes have been widely studied to support a sustainable society. To develop non‐Li batteries having high energy density, research on electrolyte materials is pivotal. Solvate ionic liquids (SILs) are an emerging class of electrolytes possessing somewhat superior properties for battery applications compared to conventional ionic liquid electrolytes. In this account, we describe our recent efforts regarding SIL‐based electrolytes for Li, Na, K, and Mg batteries with respect to structural, physicochemical, and electrochemical characteristics. Systematic studies based on crystallography and Raman spectroscopy combined with thermal/electrochemical stability analysis showed that the balance of competitive cation?anion and cation?solvent interactions predominates the stability of the solvate cations. We also demonstrated battery applications of SILs as electrolytes for non‐Li batteries, particularly for Na batteries.     

Scattering lengths for Li-Cs, Na-Cs, K-Cs, and Rb-Cs ultracold collisions

We present triplet and singlet scattering lengths for X--133Cs collisions (X=6,7Li, 23Na, 39,40,41K, and 85,87Rb). We consider the short-range potential-energy curves based on high-quality ab initio calculations and the long-range potential described by accurate dispersion coefficients available in the literature. Using a Fermi function to smoothly connect the short- and long-range terms we construct the potential for all R and evaluate the scattering length for each mixed species X--Cs. In particular, we predict that the cross section for inelastic processes between 23Na and 133Cs and between 40K and 133Cs will be small as compared with the respective elastic cross sections.     

New,Efficient, Selective,and One-Pot Method for Acylation of Amines

Hydrazine hydrate with acetic and propionic acids was an efficient reagent for acylation of primary and secondary amines at reflux temperatures. The reported one-pot method is high-yielding, simple, mild, and inexpensive.