Vapor‐Phase Carbonylation of Dimethoxymethane over H‐Faujasite

Carbonylation gets a phase lift : The usual liquid‐phase, high‐pressure processes for carbonylating formaldehydes are avoided in a novel vapor‐phase reaction. Using an acid zeolite (Faujasite) at near‐atmospheric pressure dimethoxymethane (DMM; the dimethyl acetal of formaldehyde; see scheme) is carbonylated to produce methyl methoxyacetate (MMAc). This approach provides a new route to ethylene glycol under mild conditions.

     

An approach for analysing transportation costs and a case study

One of the important parameters in the determination of optimal transportation system is economy. Therefore, a realistic method based on the technical, economical and operational parameters of various transportation modes, namely, road, railway, and sea routes is required in the analysis of costs. This method will take into consideration the probable price escalations during the lifetime of a certain transportation system. The cost of a unit of cargo or passenger per route length should be considered since it is an indicator of economics. In this paper, an approach for transportation cost analysis based on the economic analysis of the alternative modes of cargo or passenger transportation, is presented.     

High resolution electronic absorption spectra of aniline, anilino and silicon dioxide

High resolution electronic absorption spectra of aniline and anilino free radical have been recorded in the vapor phase at room temperature by flash photolysis technique, and subsequent reactions have been investigated by kinetic spectroscopy. It was possible to follow the kinetics of the anilino radical's decay which occurred predominantly by bimolecular recombination. Decay parameters of anilino free radical were measured from the absorption bands.     

Experimental and numerical investigation of pressure drop coefficient and static pressure difference in a tangential inlet cyclone separator

The aim of this study was to investigate the pressure drop coefficient and the static pressure difference related to the natural vortex length and to evaluate the results for gas-particle applications. CFD simulations were carried out using a numerical technique which had been verified previously. Results obtained from the numerical simulations were compared with the experimental data. Analysis of the results showed that the pressure drop coefficient decreases with the increasing inlet velocity, becoming almost constant above a certain value of the inlet velocity. The reason is that the effect of viscous forces decreases at high Reynolds numbers. The pressure drop coefficient also decreases with the increasing exit pipe diameter and decreasing exit pipe length.     

Some characteristic behavior of mixed spin-1/2 and spin-1 Ising nano-tube

The magnetization of a cylindrical Ising nano-tube is investigated by the use of the effective field theory with correlations. The effects of the crystal field couplings at the surface shell to the order parameters, susceptibility, internal energy, specific heat and free energy are investigated. Some characteristic phenomena are examined in the thermal variations, depending on crystal field term. Moreover, tricritical and critical points are found on the (D/J,kT/J) plane, where D/J and kT/J are reduced crystal-field and temperature, respectively.     

Selective solid phase extraction and preconcentration of ultra-trace inorganic mercury in water samples using 2,6-dimethyl-morpholine dithiocarbamate

A sensitive and selective solid-phase spectrophotometric method for the determination of trace amounts of Hg(II) cation in water is described. A complex was created with Hg(II) using 2,6-dimethyl-morpholine dithiocarbamate (DMMDTC) to form Hg(II)–(DMMDTC) and this complex was adsorbed onto microcrystalline naphthalene (MN) and then eluted with 5% acetic acid (in ethanol) solution. A preconcentration factor of 187 and a recovery of 95% were observed at pH of 5.0 and for 10 min. of extraction. The separated Hg(II) ions were quantified by using ultraviolet-visible spectrophotometer at 490.0 nm by creating a colored complex with dithizone in Triton X-100 surfactant media. Molar absorptivity and sandell’s sensitivity for the Hg(II)-dithizone were determined as 4.96 × 10⁵ Lmol^?1cm^?1 and 0.4032 µg cm^?2, respectively. The detection limit (LOD) was 1.7 μg L^?1 under the optimized conditions of the analytical method.     

Kinetics and thermodynamics of the adsorption of some dyestuffs and p-nitrophenol by chitosan and MCM-chitosan from aqueous solution

The effect of initial concentration, temperature, and shaking rate on the adsorption of three dyestuffs [orange II (O-II), crystal violet (CV), and reactive blue 5 (RB5)] and an ideal adsorbate, p-nitrophenol (PNP), by chitosan (Sigma C-3646) and the effect of temperature on the adsorption of O-II and CV by monocarboxymethylated chitosan (MCM-chitosan) were investigated. Kinetic data obtained for the adsorption of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan at different temperatures were applied to the Lagergren equation, and adsorption rate constants (k(ads)) at these temperatures were determined. These rate constants related to the adsorption of O-II and RB5 by chitosan and of O-II by MCM-chitosan were applied to the Arrhenius equation, and activation energies (E(a)) were determined. In addition, the isotherms for adsorption, at different temperatures, of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit, and isotherm constants were calculated. Because the isotherm curves obtained for the adsorption of O-II and CV by chitosan and of CV by MCM-chitosan fit the Langmuir adsorption isotherm, b constants were applied to thermodynamic equations, and thermodynamic parameters (delta G, delta H, and delta S) were calculated. Lastly, chitosan and MCM-chitosan were compared with respect to the ability to take up the dyestuffs and PNP.     

p-Hertz excitation spectroscopy of an optical antenna, optical transmitter-receiver mechanism

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.     

Singlet-singlet intermolecular optical energy transfer from naphthalene to benzophenone in the vapor phase

By using the exothermic energy transfer as a function of pressure, the rate constant for diffusion was evaluated for benzophenone/naphthalene and naphthalene/benzophenone systems. In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited naphthalene "S1" state emits photons in the fluorescence band of naphthalene and these emitted photons, as a stream of particles, are absorbed by the acceptor molecule benzophenone, then excited benzophenone fluoresces. In this investigation, sensitized fluorescence decay times in different conditions were measured for naphthalene-benzophenone system in the vapor phase, and found to be 12+/-1 ns. The ultraviolet-visible spectra of the system in the vapor phase at room temperature conditions were broad and structureless.     

DNA Nanogels To Snare Carcinogens: A Bioinspired Generic Approach with High Efficiency

Polycyclic aromatic hydrocarbons (PAHs) are combustion‐related pollutants and are ubiquitous in the environment, including in sources of drinking water. Upon contact with DNA, stable PAH–DNA adducts form rapidly as the first step towards their toxic effects. In this work, we prepared hydrophilic DNA nanogels to exploit this generic complexation process as a biomimetic scavenging method. This approach relies on interaction between PAHs and the complete network that constitutes the water‐swollen nanogels, and is not restricted to interfacial adsorption. Up to 720 μg of PAH per gram of DNA nanogel are taken up, meaning that 1 mg of DNA nanogel is sufficient to purify a liter of water containing the critical PAH concentration for cancer risk (600 ng L^?1). As a result of short diffusion pathways, PAH uptake is rapid, reaching 50 % loading after 15 minutes. Beyond PAHs, DNA nanogels may be useful for the generic detoxification of water containing genotoxins, since most known molecules that strongly associate with DNA are mutagenic.