UV index experimental values during the years 2000 and 2001 from the Spanish broadband UV-B radiometric network

An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were exceptions that could be explained by cloudiness. The maximum experimental values of the UVI were around 9 during the summer, though frequently passing this value at the inland measurement stations. The annual accumulated dose of irradiation on a horizontal plane has also been studied, as well as the evolution through the year in units of energy, standard erythemal doses and minimum erythemal doses, according to different phototypes.     

The scope of catalytic enantioselective tandem carbonyl ylide formation-intramolecular [3 + 2] cycloadditions

Catalytic enantioselective tandem carbonyl ylide formation-intramolecular 1,3-dipolar cycloaddition reactions of 2-diazo-3,6-diketoesters show promising scope in terms of asymmetric induction as the tethered alkene/alkyne dipolarophile component is varied. Cycloadditions were found to occur in moderate to very good yields, with a difference in ee exhibited by the electronically different 2-diazo-3,6-diketoesters 1, 25 and 33, 34. Values for ee of up to 90% for alkene dipolarophiles and up to 86% for alkyne dipolarophiles were obtained.     

氢化—ICP光谱法测定罐头食品中痕量锡

本文将锡的氢化反应机理研究的结论应用于分析罐头食品中痕量锡。试样消解后,用纯化过的NaOH或KOH中和,然后酸化至0.10～0.12mol/L盐酸酸度,使之与KBH_4(0.25mol/L)中的KOH浓度(0.10mol/L)相匹配。实验参数与文献所报道的相似。     

A three-phase microstructural model to explain the mechanical relaxations of branched polyethylene: a DSC,WAXD and DMTA combined study

The thermal transitions of well-characterised single-site catalysed polyethylenes having various degrees of short chain branching have been studied by differential scanning calorimetry, X-ray diffraction and dynamic mechanical thermal analysis. A critical discussion based on the results obtained by means of the different techniques is presented. The results suggest that the γ transition is independent of the branching content and degree of crystallinity, pointing towards a sub-glass local relaxation mechanism related to both amorphous and crystalline fractions. The temperature of the β transition, T _β from dynamic mechanical measurements, is in agreement with the glass transition temperature obtained by calorimetry, T _g. Moreover, T _γ, and also T _β are directly related to a change in the thermal expansion coefficient of the amorphous phase observed by X-ray scattering. It is found that the corresponding scattering distance of the amorphous halo depends on crystallinity. In addition, the calorimetric heat capacity values at T _β do not account for the total amorphous fraction determined for each material. The relaxation motions assigned to the amorphous phase glass transition seems to parallel the subsequent melting of the crystalline structure, suggesting a hierarchical motion of different structures as temperature increases. Dynamic mechanical thermal analysis supports these observations, showing a broad transition in the phase angle involving first the relaxation of amorphous phase, then the (presumable) more rigid intermediate phase, and finally the crystalline phase, as the temperature increases.     

Kinetic methods for the determination of cadmium(II) based on a flow-through bulk optode

Three kinetic methods based on flow injection, flow, and stopped-flow injection were applied for the determination of Cd(II) using a flow-through bulk optode membrane that incorporates 1-(2-pyridylazo)-2-naphtol (PAN) in a plasticized poly(vinyl) chloride membrane entrapped in a cellulose support. The calibration graphs plotting the reflectance at 560 nm versus [Cd(II)](1/2) for the first two methods and versus [Cd(II)] for the third were linear up to 56.2 mg l(-1). The detection limits of the methods were 0.01, 0.06 and 0.8 mg l(-1), respectively. The FI method was selected for application purposes. The variation coefficient of the sensor response for 11.2 mg l(-1) of Cd(II) was +/-0.31 and +/-0.65% between different membranes. The sensor can be readily regenerated with a carrier (acetic-acetate) buffer of pH 4. The FI method was applied to the determination of cadmium in an alloy and in water.     

Size-based separations of proteins by capillary electrophoresis using linear polyacrylamide as a sieving medium: model studies and analysis of cider proteins

Electrophoretic conditions to separate sodium dodecyl sulfate (SDS)-protein complexes according to their relative molecular mass by capillary electrophoresis (CE) using linear polyacrylamide as a sieving matrix were examined. Five purified proteins with relative molecular masses between 14 400 and 66 200 Da were separated on a coated fused-silica capillary with an internal diameter of 100 microm and an effective length of 24 cm (total length, 32.5 cm). Benzoic acid was added to the solution of purified proteins as internal standard; beta-mercaptoethanol was also added as reducing agent. The running buffer composition was 0.05 M tris(hydroxymethyl)aminomethane (Tris), 0.035 M aspartic acid, 0.1% m/v SDS, 4% m/v acrylamide, the resulting pH being 8.0. The applied voltage was 7 kV (reversed voltage polarity) in order to avoid high current intensities. Under optimized conditions, the five proteins were separated in less than 15 min, with a % relative standard deviation (RSD) between 0.2 and 0.4 for migration times in the same day. Good efficiency (values between 150 000 and 40 000 N/m) and resolution (values between 2 and 2.8) were obtained. The inverse of relative migration times was found to correlate with the logarithm of their relative molecular mass. Finally, cider proteins were analyzed and their relative molecular masses were determined. These results were compared with those obtained by SDS-polyacrylamide gel electrophoresis (SDS-PAGE).     

Total synthesis and absolute configuration of minalemine A, a guanidine peptide from the marine tunicate Didemnum rodriguesi

The total synthesis of the 3S,2S and 3R,2S diastereomers (1a and 1b) of minalemine A and the identification of the natural compound as the 3R,2S isomer is described. The key step in the synthesis is the preparation of the two enantiomers of the beta-amino diacid 3-(N-carboxymethyl)-aminodecanoic acid (Ncma), which were obtained by stereoselective alkylation with allyl bromide of two nonanoic acid imides bearing chiral oxazolidinones as chiral auxiliaries. Natural minalemine A shows identical 1H NMR and very similar 13C NMR spectra compared to the two synthetic diastereomers. Sufficient differences in their chromatographic behavior to allow conclusive identification were not found. However, the corresponding N-2-naphthoyl amides presented quite distinct circular dichroism spectra (CD), and these confirmed the 3R,2S configuration for the natural minalemines and the R configuration for the constituent beta-amino diacid, Ncma.     

Flow-Through Bulk Optode for the Spectrophotometric Determination of Perchlorate

A flow-through spectrophotometric bulk optode for the flow-injection determination of perchlorate is described. As active constituents, the optode incorporates the lipophilic pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo) phenol and methyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl chloride) membrane which is entrapped in a cellulose support. The optode is applied in conjunction with the flow injection technique at pH 8.2 (TRIS buffer). The sensor is readily regenerated with a 10^–2M NaOH carrier solution. The analytical characteristics of this optode with respect to response time, dynamic measurement range, reproducibility and selectivity are discussed. The proposed FI method is applied to the determination of perchlorate in waters from different sources.Received December 16, 2002; accepted May 16, 2003 Published online August 8, 2003     

ICP—AES法测定出口镁砂

应用ICP-AES法对出口镁砂中硅、钙、铁、铝、钛等氧化物含量进行测定。文中对其测试方法、条件进行探讨;辅以灼烧减量的测定,从中可以求出高含量的氧化镁。方法准确,快速,优于化学法。     

Flow-through bulk optode for the fluorimetric determination of perchlorate

A flow-through fluorescence bulk optode for the flow-injection determination of perchlorate is described. As the active constituents the optode incorporates the lipophilized pH indicator fluorescein octadecyl ester and methyl tridodecyl ammonium chloride, dissolved in a plasticized poly (vinyl) chloride membrane entrapped in a cellulose support. The optode is applied in conjunction with the flow injection technique for perchlorate determination at pH 4.5 (acetic-acetate). The sensor is readily regenerated with the pH 10.4 (TRIS) carrier solution. The analytical characteristics of this optode with respect to perchlorate response time, dynamic measurement range, reproducibility and selectivity are discussed. The proposed FI method is applied to the determination of perchlorate in waters from different sources.