Wind climatology between 950 and 500 hPa over the Mediterranean area above Italy

Summary In order to improve the simulation of wind probability distributions at ground level, eight years of wind data of the multivariate analyses at 850, 700, 500 hPa levels over Italy, and eleven years of wind radiosoundings performed at 5 Italian Air Force stations at 950, 900, 800, 700, 600, and 500 hPa have been processed. The vertical profiles of the distribution parameters of wind speed present predictable behaviour, with the exception of Brindisi. The frequency distribution profiles of the wind directions are more complex. Temporarily seconded to the RISOE National Laboratory (DK) as part of the EEC-DGXII Programme ?Stimulation Action?.     

Unsteady axisymmetric stagnation flow on a circular cylinder

Unsteady, axisymmetric stagnation flow about a circular cylinderis examined when the far-field flow is a periodic function oftime with a fixed time average and an oscillatory part of prescribedamplitude and frequency. Solutions are computed for arbitraryvalues of the Reynolds number, quantifying the effects of surfacecurvature, and a frequency parameter based on the period ofthe far-field flow. It is found that solutions remain regularand periodic provided that the far-field amplitude lies belowa critical value. Above this value, solutions terminate in afinite-time singularity. The blow-up time is delayed by increasingthe curvature of the surface. These results are corroboratedby asymptotic predictions valid in the limits of small and largeamplitude and frequency. For large Reynolds number, the problemreduces to the two-dimensional stagnation-point flow againsta plane wall studied by previous authors.     

Digital simulation of cyclic voltammetric experiments for non-first-order electrode reactions

Application of the explicit finite-difference simulation method to linear-sweep cyclic voltammetry in the case of non-first-order electrode reactions is described. Reversible, quasi-reversible and totally irreversible electrode reactions with reaction orders > 1 or < 1 are discussed. Simple criteria for evaluating the kinetic parameters are proposed. The accuracy of the proposed method is checked by comparing the results obtained with literature data.     

Ion chromatographic determination of N-nitrosoglyphosate in a glyphosate matrix

The use of high-performance ion chromatography (HPIC) for the determination of N-nitrosoglyphosate [N-nitroso-N-(phosphonomethyl)glycine] is reported. NMR, spectrophotometric and electroanalytical measurements showed that two conformers of N-nitrosoglyphosate in slow equilibrium are always present. Separation of these conformers is achieved by using appropriate chromatographic conditions. The conductimetric detection of N-nitrosoglyphosate and glyphosate and application to the determination of traces of N-nitrosoglyphosate in complex matrices are also reported.     

Infrared and Raman investigation of the charge–density-wave state in rare-earth tri-telluride compounds

We summarize our recent efforts in investigating the charge–density-wave (CDW) state of the rare-earth tri-tellurides RTe₃ by means of infrared and Raman techniques. We identify the CDW gap, as order parameter of the broken-symmetry ground state, as well as the collective mode of the CDW condensate.     

Polyethylene glycol matrix reduces the rates of photochemical and thermal release of nitric oxide from S-nitroso-N-acetylcysteine

S -nitrosothiols have many biological activities and may act as nitric oxide (NO) carriers and donors, prolonging NO half-life in vivo. In spite of their great potential as therapeutic agents, most S -nitrosothiols are too unstable to isolate. We have shown that the S -nitroso adduct of N -acetylcysteine (SNAC) can be synthesized directly in aqueous and polyethylene glycol (PEG) 400 matrix by using a reactive gaseous (NO/O₂) mixture. Spectral monitoring of the S–N bond cleavage showed that SNAC, synthesized by this method, is relatively stable in nonbuf-fered aqueous solution at 25°C in the dark and that its stability is greatly increased in PEG matrix, resulting in a 28-fold decrease in its initial rate of thermal decomposition. Irradiation with UV light (λ= 333 nm) accelerated the rate of decomposition of SNAC to NO in both matrices, indicating that SNAC may find use for the photogeneration of NO. The quantum yield for SNAC decomposition decreased from 0.65 ± 0.15 in aqueous solution to 0.047 ± 0.005 in PEG 400 matrix. This increased stability in PEG matrix was assigned to a cage effect promoted by the PEG microenvironment that increases the rate of geminated radical pair recombination in the homolytic S–N bond cleavage process. This effect allowed for the storage of SNAC in PEG at −20°C in the dark for more than 10 weeks with negligible decomposition. Such stabilization may represent a viable option for the synthesis, storage and handling of S -nitrosothiol solutions for biomedical applications.     

Analysis of 11 carefully selected Italian stations. Choice of an interpolation method for probability papers

Summary Eleven wind stations, evenly distributed over Italy, were selected and the data from them carefully checked. Asymptotic analysis (first-type distribution) was applied to the largest wind values. Three different methods of probability papers were used in order to estimate the distribution parameters from which the return periods are computed. Comparing the ordinary least squares, Lieblein's and Tukey's methods, the latter appears to be the most suitable for mapping extreme winds in Italy.     

Monthly maps of daily global incident solar radiation in Italy

Summary Measurements of daily sunshine hours and of global solar radiation for most of the existing stations in Italy, covering a period of (5⋎30)y, were analysed. Linear correlation coefficients were calculated between the above-cited measurement for 36 stations and for every month of the year. Italy has been divided in areas in which such coefficients are not much different among them. The mean values of these coefficients relative to each area were used to estimate the global radiation for the sunshine stations located in the same area. Using so radiation obtained values for about 140 stations, 12 month global radiation maps were realized for the Italian territory. Possible errors and limitations of the maps were discussed.     

Gas chromatography-mass spectrometry determination of 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate in wine: a comparison of headspace solid phase microextraction and solid phase extraction methods

A gas chromatography-mass spectrometry method was established using headspace solid phase microextraction (HS-SPME) as the sampling procedure to analyse 3-mercaptohexan-1-ol (3-MH) and 3-mercaptohexyl acetate (3-MHA), two molecules with a tropical fruit aroma, in wine at trace level. This method offers important advantages, as it neither requires time-consuming sample preparation nor uses dangerous organic compounds, thus making control of wine aroma easier and suitable for routine analysis. As a comparison, a solid phase extraction (SPE) method, already described elsewhere for aroma analysis, was applied to quantify these analytes, extending this exhaustive enrichment to two important thiols. Detection limits for both the approaches were close to the sensory threshold value, resulting lower for the HS-SPME procedure and suitable for requirements in the oenological field. The application of the two proposed methods to 52 wines of different varieties gave similar results.