Aromatic products of 340 °C supercritical-toluene extraction of two Turkish lignites: an n.m.r. study

Fractions of Elbistan and Seyitomer (Turkish) lignites, extracted with supercritical toluene at 340 °C and 8 MPa, have been separated by solvent extraction and silica-gel chromatography. Analyses by n.m.r. and i.r. spectroscopies and other methods have been combined in structural-analysis schemes to yield information about the average molecule in aromatic extracts. Carbon aromaticities, f_a, derived from 22.63 MHz ¹H-decoupled pulse Fourier-transform (PFT) ¹³C-n.m.r. are more widely spread for Elbistan (0.34–0.56) than for Seyitomer (0.40–0.43), and are lower than for supercritical-gas (SCG) products from bituminous coals. ¹³C-n.m.r. also reveals the presence of aromatic ether-O in polar fractions. Narrow aromatic signals in 100 MHz ¹H-n.m.r. spectra suggest the presence of single-aromatic-ring average structures. In the hexane-soluble aromatics, 27% (Elbistan) and 29% (Seyitomer) of the available sites are substituted by alkyI groups, some of which are at least eight carbon atoms long; the hexane-soluble polar and asphaltene/asphaltol fractions contain fewer such groups.     

Dis-Bond Detection and the Possibility of Interfacial Stiffness Measurement with Real-Time Impulsive Stimulated Thermal Scattering

We describe a new, real-time, noninvasive method for dis-bond (delamination) detection which is based on a technique known as impulsive stimulated thermal scattering (ISTS). We first explain the ISTS technique and compare data from polyimide films tightly bound to silicon substrates with data from unsupported polyimide films. The observed differences in the data from these two cases are readily understandable and offer an unmistakable signature for delaminations. We demonstrate ISTS dis-bond detection by locating and mapping out randomly-distributed and spatially-fine regions of delamination in a polyimide film-silicon substrate system. Finally, we present two simple physical models of the interfacial region which comprehensively describe acoustic data from the tightly-bound and the unsupported samples. With insight from simulations using these models, we suggest how ISTS might be used to determine interfacial adhesion quality and we show how ISTS sensitivity to interfacial effects can be adjusted.     

Quantitative determination of glycerin in soap by capillary gas chromatography

A simple and rapid procedure is described for the isolation, silylation and capillary gas chromatographic quantitation of the free glycerin content in soap. Free glycerin is determined by mixing the sample with dimethylformamide (DMF), filtering the mixture, silylating an aliquot withbis-trimethylsilyltrifluoroacetamide (BSTFA), and quantitating by capillary GC using flame ionization detection. Silyl derivatization and capillary gas chromatography provide for a quick and easy analysis which allows straightforward automated gas chromatographic analysis instead of the more tedious traditional periodate methods. This procedure also provides reliable quantitation for glycerin levels in soap lower than those measurable with the standard methods.     

On the preparation and properties of CuZSM-5 catalysts for NO decomposition

Equilibrium exchange isotherms were determined for the exchange of Cu²⁺ with NaZSM-5 at varying Cu(Ac)₂ concentrations in solutions of constant volume and zeolite weight. At low Cu²⁺ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary.     

Attrition mill operating characteristics

The attrition mill is a device for mechanically reducing solid particle size by intense agitation of a slurry of material being milled and coarse milling media. For example, in 10 hours of milling, specific surfaces of 40 and 25 m²/g were obtained for alumina and barite, corresponding to 38 and 56 nm equivalent spherical diameter, respectively. Size reduction rates for relatively coarse particles were first-order and increased linearly with power input to the mill. Optimum milling medium concentration corresponded to medium particles moving a distance of approximately 0.7 of their diameter before collision with another such particle. Power characteristics of the attrition mill were essentially the same as those of a radial flow turbine mixer. Laminar flow became disrupted at N_Re ≈ 200, while turbulent flow was established at N_Re > 8000. Slurries of fine powders exhibited the same linear power-average density dependence as single-phase liquids. However, a different dependence was observed with large particles.     

Studies on modeling and control of spouted bed reactors—II: Control

Control and operability characteristics of an adiabatic spouted bed reactor with a first order reaction are investigated. The reactor transient response to changing operating conditions is analyzed and the generic control problems are formulated. Reduced-order state space models suitable for process control studies are constructed by utilizing the methods of orthogonal collocation and singular perturbation.Based on modern control and estimation techniques a hierarchy of different control systems is systematically generated. The assessment of alternative d     

Chemical nature of a supercritical-gas extract of coal at 350 °C

A novel supercritical-gas (toluene) extract, comprising 17.0% of a low-rank coal, was separated by a combination of solvent fractionation and both silica-gel and gel-permeation chromatography. The average structure of the soluble fractions, together amounting to 85% of the extract, was investigated by a variety of spectroscopic methods, including high-resolution ¹H nuclear magnetic resonance, proton-decoupled pulse Fourier transform ¹³C magnetic resonance, infrared and low-ionizing-voltage mass spectrometry. Analyses were also made by gas chromatography. The results for the low-oxygen fractions are consistent with a generally open-chain polynuclear aromatic average structure with about 33% of the available sites carrying alkyl substituents. The most common of these is methyl, but there are also substantial numbers of longer-chain alkyls, some branched, and naphthenic groups. The fractions rich in oxygen also have similar structure but for the presence of phenolic hydroxyl groups, and, as is demonstrated for the first time by ¹³C n.m.r., ether oxygen links. Aliphatic constituents are mainly straight-chain alkanes with some branched-chain and isoprenoid hydrocarbons. These conclusions are discussed in terms of the thermal history of the extract and are compared with other contemporary views on the low-molecular-weight constituents of coal.     

The Linguistic Annotation Framework: a standard for annotation interchange and merging

This paper overviews the International Standards Organization–Linguistic Annotation Framework (ISO–LAF) developed in ISO TC37 SC4. We describe the XML serialization of ISO–LAF, the Graph Annotation Format (GrAF) and discuss the rationale behind the various decisions that were made in determining the standard. We describe the structure of the GrAF headers in detail and provide multiple examples of GrAF representation for text and multi-media. Finally, we discuss the next steps for standardization of interchange formats for linguistic annotations.     

Properties of the glycerol acylating enzymes in microsomal preparations from the developing seeds of safflower (Carthamus tinctorius) and turnip rape (Brassica campestris) and their ability to assemble cocoa-butter type fats

Microsomal membrane preparations from the developing seeds of safflower (Carthamus tinctorius, var. Gila) and turnip-rape (Brassica campestris, var. Bele) catalyzed the assembly of triacylglycerols (triglycerides) from sn-glycerol 3-phosphate and acyl-CoA. The membrane preparations were used to assess the acyl specificity properties of the initial acylating enzymes—glycerol 3-phosphate acyltransferase (GPAT) and 1-acylglycerol 3-phosphate acyltransferase (lysophosphatidic acid acyltransferase, LPAAT)—that are responsible for the fatty acids at positions sn-1 and sn-2 of the sn-triacylglycerol, respectively. In spectrophotometric assays it was possible to evaluate, to some extent, how these enzymes will utilize unusual and foreign fatty acids that are not normally found in these particular plant species. The acylating enzymes from both plants used, to varying extents, a comprehensive range of acyl-CoA donor species and some kinetic properties of the substrates involved are presented. The enzymes from safflower, however, were generally the more selective, whereas the turnip-rape was less particular and could utilize a range of acyl substrates. The enzymes from both plants hardly utilized erucate (C22∶1), and the significance of this is discussed in terms of mechanisms which have evolved in order to exclude certain, perhaps detrimental, fatty acids from structural membrane lipids and dedicate them to storage lipid assembly. The ability of the microsomal preparations, from the developing seeds of both plants, to synthesize cocoabutter type fats was investigated. Microsomal membranes were incubated with glycerol 3-phosphate and equimolar amounts of palmitate, oleate and stearate. Safflower preparations catalyzed the construction of sn-triacylglycerol with largely palmitate, oleate and stearate in positions sn-1, 2 and 3, respectively. The selectivity for acyl species in rape was less pronounced, however, substantial saturated-unsaturated-saturated oils were still produced. The results are discussed in terms of the acyl selectivity properties of the glycerol acylating enzymes. It is evident that given the correct composition of fatty acids, the plant can produce cocoabutter or other exotic fats.     

Factors influencing the photofading of commercial anthraquinone dyes in solution

The photofading of two anthraquinone dyes has been studied in aqueous solution using ultraviolet-visible absorption spectroscopy and flash photolysis. The influence of alcohol concentration, pH, atmosphere, photosensitisers and stabilisers have been examined and these lead to some important conclusions on the mechanism of dye fading. Essentially, the results indicate the photoexcited triplet state of the dye undergoes a process of either electron or hydrogen-atom abstraction depending on the nature of the environment. Other factors such as aggregation and singlet oxygen also appear to play an important role in solution photofading. The relevance of these results to photofading in a polymeric phase is discussed.