Nuclear and GP-Nuclear Groups

We define GP-nuclear groups as topological Abelian groups for which the groups of summable and absolutely summable sequences are the same algebraically and topologically. It is shown that in the metrizable case only the algebraic coincidence of the mentioned groups is needed for GP-nuclearity. Some permanence properties of the class of GP-nuclear groups are obtained. Our final result asserts that nuclear groups in the sense of Banaszczyk are GP-nuclear. The validity of the converse assertion remains open.     

Identification by GC-FID and GC-MS of amino acids, fatty and bile acids in binding media used in works of art

GC-FID was used as single methodology for the identification and differentiation of proteins, lipids and ox bile from binders used in artistic paintings. The samples were hydrolyzed by HCl. Subsequently, the simultaneous formation of volatile derivatives of the amino, fatty and bile acids with ethyl chloroformate was performed quickly and safely in an aqueous medium. The derivatives were separated by capillary GC and characterized by GC-MS. The ageing of drying oils was studied, identifying pelargonic acid among other degradation products. Proteinaceous and lipoid binding media were characterized by means of the quotients between the areas of the peaks for each amino or fatty acid with respect to the area of the peak for alanine or palmitic acid. Fatty acids from ox bile were easily identified by their retention times characteristic for eicosanoic, docosanoic and pentadecanoic acids. The suggested method was applied to the analysis of binders in baroque paintings by Palomino in Valencia (Spain). Animal gelatine and linseed oil were found. Received: 27 September 2000 / Revised: 16 January 2001 / Accepted: 17 January 2001     

Synthesis of isoindoloisoquinoline alkaloids. A revision of the structure of (±)-nuevamine

An easy and efficient method for the synthesis of isoindoloisoquinolines, and the assignment of a new structure for the alkaloid (±)-nuevamine are reported.     

(+)-4-Hydroxysarcocapnine: Structure and stereochemical considerations

(+)-4-Hydroxysarcocapnine obtained from Sarcocapnos enneaphylla (L.) DC. has been shown by spectral studies and synthesis to possess the new 4-hydroxyisocularine structure (1a). Straightforward assignment of the configuration of a 4-hydroxycularine by NMR is also-discussed.     

NH4OH-Based pretreatment for improving the nutritional quality of single-cell protein (SCP)

The potentiality of treatments with NH₄OH solutions for improving the quality of protein concentrates fromCandida utilis biomass was studied. The effects of NH₄OH concentration, reaction time, and temperature on both biomass recovery and composition of processed samples (including nucleic acid and protein contents) were studied. The results obtained were used to develop empirical models providing a quantitative interpretation of the interrelationships among the variables involved. Additional discussion of the reaction selectivity is provided. Under selected conditions, 96% of nucleic acid removal was achieved with 88% protein recovery. The treated cells were high in vitro digestibility and showed an amino acid profile similar to that of untreated biomass.     

Classes caractéristiques non triviales des feuilles de sous-feuilletages localement homogènes

We discuss the computation of the secondary characteristic classes and of the holonomy classes for the leaves of locally homogeneous subfoliations. Furthermore, we shall construct some examples of locally homogeneous subfoliations (F ₁, F ₂) so that a leaf (L ₁, L ₂) of (F ₁, F ₂) admits non-trivial secondary characteristic classes and non-trivial holonomy classes which cannot be obtained if we consider each leaf separately.     

Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples

Summary A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25 μg L⁻¹ of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations.     

Lowering the detection limit of calcium selective ISFETs with polymeric membranes

Detection limits of Ca sensitive ISFETs with photocured polyurethane membranes with a neutral carrier and an ion-exchanger as ionophores are studied. It is shown that conditioning of ISFETs in solutions containing only interfering ions results in reduction of the detection limit. Zero-current ion fluxes approach elaborated for polymeric membrane ion-selective electrodes (ISEs) is used to explain the obtained results.     

Simultaneous determination of antimony(III) and antimony(V) by UV-vis spectroscopy and partial least squares method (PLS)

This paper describes a procedure for the speciation of antimony by UV-vis spectroscopy using pyrogallol as complexing agent. A partial least squares (PLS) regression was performed to resolve highly overlapping spectrophotometric signals obtained from mixtures of Sb(III) and Sb(V). The relative error in absolute value was less than 5% when concentrations of several mixtures were calculated. The minimum concentration determined was 3.96 × 10⁻⁵ mol dm⁻³ and 3.98 × 10⁻⁵ mol dm⁻³ for Sb(V) and Sb(III), respectively. The analysis of the possible effect of the presence of foreign ions in the solution was performed and the procedure was successfully applied to the speciation of antimony in pharmaceutical preparations and aqueous samples.     

Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes

The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.