Fast Response Oxygen Micro-Optodes Based on Novel Soluble Ormosil Glasses

 A new type of phenyl substituted ormosils as a matrix for oxygen-sensitive micro-optodes is described. The new ormosils combine features of classical polymers such as solubility in organic solvents and those of sol–gel glasses such as mechanical stability and a porous structure. They make possible a simple and fast fabrication of microsensors with reproducible properties. The influence of the conditions during the polymerisation process (precursor composition and thermal treatment) on the sensing properties has been studied in detail. Oxygen-sensitive films with ruthenium(II)–tris-(4,7-diphenyl-1,10-phenanthroline) and platinum(II)–octaethylporphyrin as indicators were characterised with respect to their mechanical and photophysical properties. Photostability, oxygen sensitivity, response behaviour and signal intensities of the sensing films and the micro-optodes were examined. Micro-optodes based on the new sensing materials are fast responding, photostable and can be produced with a sufficient batch to batch reproducibility. Compared to previously described oxygen micro-optodes, where polystyrene was used as immobilisation matrix, the new sensors can be autoclaved and show favourable properties such as a faster response and a higher sensitivity. They possess many potential applications in medical and biological research. Received June 12, 1998. Revision December 10, 1998.     

Learning from dependent observations

In most papers establishing consistency for learning algorithms it is assumed that the observations used for training are realizations of an i.i.d. process. In this paper we go far beyond this classical framework by showing that support vector machines (SVMs) only require that the data-generating process satisfies a certain law of large numbers. We then consider the learnability of SVMs for α-mixing (not necessarily stationary) processes for both classification and regression, where for the latter we explicitly allow unbounded noise.     

Nanosecond and femtosecond Laser Induced Breakdown Spectroscopic analysis of bronze alloys

In the present work we are studying the influence of pulse duration (nanosecond (ns) and femtosecond (fs)) at λ = 248 nm on the laser-induced plasma parameters and the quantitative analysis results for elements such as Sn, Zn and Pb, in different types of bronze alloys adopting LIBS in ambient atmosphere. Binary (Sn–Cu), ternary (Sn–Zn–Cu or Sn–Pb–Cu) and quaternary (Sn–Zn–Pb–Cu) reference alloys characterized by a chemical composition and metallurgical features similar to those used in Roman times, were employed in the study. Calibration curves, featuring linear regression coefficients over 98%, were obtained for tin, lead and zinc, the minor elements in the bronze alloys (using the internal standardization method) as well as for copper, the major element. The effects of laser pulse duration and energy on laser-induced plasma parameters, namely the excitation temperature and the electron density have been studied in our effort to optimize the analysis. Finally, LIBS analysis was carried on three real metal objects and the spectra obtained have been used to estimate the type and elemental composition of the alloys based on the calibration curves produced with the reference alloys. The results obtained are very useful in the future use of portable LIBS systems for in situ qualitative and quantitative elemental analysis of bronze artifacts in museums and archaeological sites.     

Analytical pyrolysis of proteins

Summary Gelatine and silk have been thermally degraded at 330° C in a melt of nylon 6.10 and by addition of small amounts of sodium and potassium hexanoate.Both proteins yield cyclic dimers (diketopiperazines) and smaller amounts of cyclic tetramers and higher oligomers. The mixture of degradation products were investigated by temperature resolved field ionization mass spectrometry and provide informations about neighbouring amino acids (diade sequences). Integral mass spectra give the relative intensities of diades.In accordance with data reported in literature glycine, proline, hydroxyproline, glutamic acid and alanine could be proved as most frequently incorporated amino acids in gelatine and glycine, alanine and tyrosine in silk.

---

Analytische Pyrolyse von Proteinen

Zusammenfassung Gelatine und Seide wurden in einer Schmelze von Nylon 6,10 und unter Zusatz von kleinen Mengen an Natrium- und Kaliumhexanoat bei 330° C thermisch abgebaut.Beide Proteine liefern cyclische Diniere (Diketopiperazine) und kleine Mengen an cyclischen Tetrameren und höheren Oligomeren. Die jeweiligen Mischungen der Abbauprodukte wurden durch temperaturaufgelöste Feldionisationsmassenspektrometrie untersucht und liefern Informationen über benachbarte Aminosäuren (Diadensequenzen). Integrale Massenspektren liefern die relativen Intensitäten dieser Diaden.In Übereinstimmung mit in der Literatur beschriebenen Angaben wurden auf diese Weise in der Gelatine Glycin, Prolin, Hydroxyprolin, Glutaminsäure und Alanin, sowie in der Seide Glycin, Alanin und Tyrosin als häufigste Aminosäuren nachgewiesen.

     

Preprocessing of ion mobility spectra by lognormal detailing and wavelet transform

This study has developed an efficient preprocessing strategy for ion mobility spectrometry (IMS) data allowing for improved peak clarity and comparability of different measurements. Using the discrete wavelet transform for data compression and denoising, and fitting a lognormal function to the strong tailing of the reactant ion peak (RIP), enables a data reduction to 25% or less, a significant increase of the signal-to-noise ratio, and the successful elimination of the RIP tailing. The preprocessing of breath measurements obtained by coupling an IMS to a gaschromatographic column, has resulted in the desired outcome of smooth peaks lying on a common base level. These results are transferable to other applications of one- and two-dimensional separations with IMS or instrumentations generating a similar data structure.     

Quantum simulations of toroidal electric ring currents and magnetic fields in linear molecules induced by circularly polarized laser pulses

Circularly polarized laser pulses may excite state selective unidirectional toroidal electric ring currents around the axis of oriented linear molecules. These in turn induce state selective magnetic fields. Quantum simulations for AlCl show that these effects are about one or even more than three orders of magnitudes larger than those which may be prepared in oriented planar molecules such as Mg-porphyrin, by means of either circularly polarized laser pulses, or by traditional magnetic fields, respectively.