Generic variations and NTP$$_$$

We prove a preservation theorem for NTP\(_1\) in the context of the generic variations construction. We also prove that NTP\(_1\) is preserved under adding to a geometric theory a generic predicate.     

Silica gel analysis by slurry-sampling graphite-furnace atomic absorption spectrometry

Analytical conditions for the determination of cadmium, lead, copper, iron, aluminium and titanium in commercial silica gel samples by slurry-sampling graphite-furnace atomic absorption spectrometry are established. The influence of the silica matrix on the background absorption is described. Stability tests for slurries have been carried out. Results are calculated by the method of standard additions. Statistical evaluations of the results indicate that the slurry method is reproducible and its precision is comparable to other methods used. Advantages of this method are simplicity and short time of analysis.Presented at the 5th International Colloquium on Solid Sampling with Atomic Spectroscopy, May 18–20, 1992; Geel, Belgium. Papers edited by R.F.M. Herber, Amsterdam     

New enantioselective method for hydration of alkenes using cyclodextrins as phase transfer catalyst

A new enantioselective/inverse phase transfer catalysis (IPTC) reaction for the Markovnikov hydration of double bounds by an oxymercuration-demercuration reaction with cyclodextrins as catalysts was disclosed. Moderate ee (up to 32%) and yields (14-60%) were obtained for allylic amines and protected allylic alcohols as starting materials.     

Intermolecular cycloaddition of nonstabilized azomethine ylides generated from 1,3-thiazolidine-4-carboxylic acids: synthesis of 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazoles

The 1,3-dipolar cycloaddition of dimethyl acetylenedicarboxylate with nonstabilized azomethine ylides, generated via the decarboxylative condensation of 1,3-thiazolidine-4-carboxylic acids with aldehydes, afforded 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazole derivatives. 2-Substituted-1,3-thiazolidine-4-carboxylic acids led to the stereoselective formation of 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazoles. Quantum-chemistry calculations were carried out allowing the rationalization of the observed stereoselective formation of the anti-dipole.     

On the belt and moebius isomers of the coronene molecule

The structure and stability of ca. 100 nonplanar constitutional isomers of the coronene molecule of general formula C(24)H(12) have been estimated by semiempirical and by ab initio calculations. The isomers studied are unbranched cyclic catacondensed structures and fall into two classes, viz., the belt (B) and the Moebius (M) type. The calculations have shown some of the M-isomers to be more stable than the corresponding B-isomers and thus to form a platform for the future synthesis of or search for such isomers in Nature.     

Influence of gas flow patterns on NOx removal efficiency

Dose distribution in flue gas irradiation vessel is not uniform due to limited electron penetration range. This phenomena influence overall NO_x removal efficiency is observed in the process. The remarkable increase in the efficiency can be achieved by multistage gas irradiation and gas mixing between stages. The results of modelling for longitudinal beam scanning as applied at EPS Kawêczyn pilot plant are presented in the paper. These are the basis for process vessel upscaling.     

Structure-function relationships in glutathione and its analogues

The results are presented of measurements of protonation constants (potentiometry and NMR), UV spectroscopic properties and redox potentials of GSH and its five analogues, which are modified at the C-terminal glycine residue (gammaGlu-Cys-X, X = Gly, Gly-NH2, Gly-OEt, Ala, Glu, Ser). Strong linear correlations were found between various properties of the thiol and other functions of these peptides. These results allow discussion of the relationships between the structures and properties in glutathione and its analogues, and provide a novel chemical background for the issue of control of GSH reactivity.     

Fibre optic coupler as a detector for microfluidic applications

A new construction of a fibre optic coupler is presented in the paper. Two polymer optical fibres were used to build a coupler in which coupling efficiency of optical power depends on the refractive index of liquid delivered to a microchannel formed by the fibres. The coupler was tested as a detector in saccharose concentration measurements, and was used in absorbance measurements. A red light emitting diode and a spectrometer were used as a light source and a photodetector, respectively. Experiments confirmed that the coupler can be used for the real time monitoring of the changes in the refractive index of a saccharose solution exhibiting repeatable changes in the signal, with no hysteresis. Absorbance tests were performed with a solution of bromothymol blue at different pH.     

Cycloreversion and other gas-phase reactions of neutral and cationic pyrrolidine-fused chlorins and isobacteriochlorins under ion bombardment and electrospray

Neutral and cationic pyrrolidine-fused chlorins and isobacteriochlorins derived from meso-tetrakis(pentafluorophenyl)porphyrin undergo cycloreversion reactions in the gas phase, either when desorbed from a liquid matrix by ion bombardment or when electrosprayed. Cycloreversion occurs through loss of either neutral or charged moieties, with and without hydrogen and methyl radical migration, and both as high- and low-energy collision processes. For the doubly charged isobacteriochlorin, one-electron reduction with methyl loss occurs under ion bombardment and electrospray, through hypervalent pyrrolidinium radical formation.     

Controlled release of 2‐heptanone using starch gel and polycaprolactone matrices and polymeric films

Varroa jacobsoni is a parasitic mite that is threatening the honeybee industry in many parts of the world. 2‐Heptanone, a natural product made by honeybees at low concentrations, is effective at elevated concentrations in controlling mite populations in honeybee colonies, especially when released over a 42 day period. An extrusion process was used to encapsulate 14, 18, and 25% 2‐heptanone in a polycaprolactone (PCL) matrix. Less than 18% of the 2‐heptanone was encapsulated in the PCL matrix. The high vapor permeability of PCL to 2‐heptanone resulted in a high flux rate and limited the usefulness of PCL as an encapsulation matrix for controlled‐release devices. A starch gel containing three times its weight in 2‐heptanone was prepared from starch‐based microcellular foam (MCF). The gel had compressive, tensile, and flexural strength values in the range of 0.56 to 1.9 MPa. 2‐Heptanone quickly evaporated from non‐laminated gels. However, when the gel was laminated with different polymeric films, a wide range of flux rates was obtained. The T₅₀ for gels laminated or coated with poly(vinyl alcohol) (PVAL, 99% hydrolyzed) and ethylene‐vinyl alcohol copolymer (EVAL) was 72 and 1030 days, respectively. The most promising film was a starch/glycerol film that released 50% of the 2‐heptanone (T₅₀) in approximately 13 days. Copyright © 2007 John Wiley & Sons, Ltd.