Electrochemical Studies on Effects of Psychostimulants,Opioids and Alcohol Intake Towards Level of Hydrogen Peroxide in the Brain Striatum

Hydrogen peroxide (H₂O₂) was the main types of many peroxides produced in living mammalian cells that consumed oxygen. In the brain, the main source of H₂O₂ was the superoxide dismutase (SOD)‐catalyzed reaction in mitochondria. However, the level of H₂O₂ would be elevated through administration of control drugs and alcohol by dopamine metabolism of monoamine oxidase. In this study, a H₂O₂ microsensor was used to investigate the level of H₂O₂ in the brain striatum after administration of methamphetamine (MAP), morphine (MrP) or ethanol (Eth). The placement of microsensor in the brain was done at coordinates A/P 1.1 from bregma, M/L+2.6 and D/V‐1.5. A working potential of +0.05 V vs. Ag/AgCl was applied. The H₂O₂ concentration was measured direct from the current generated by its catalytic reaction at the electro active surface of the electrode. A significant increase of H₂O₂ level was observed after 7 successive injections of the controlled drugs or alcohol. The initial measurement of H₂O₂ is essential as excess dosage of H₂O₂ during treatment will contribute to the formation of neurotoxin oxygenated radicals. The H₂O₂ was the precursor of O_2? and OH radicals. Thus, this study provided a mean to monitor H₂O₂ level in the brain.     

High-absorbing gradient multilayer coatings with silver nanoparticles

We suggest an efficient way to enhance broadband visible light absorption in multilayer nanostructured systems formed by silver nanoparticle arrays. This approach is based on the explicit use of a gradient change in the parameters of the arrays (such as nanoparticle size or concentration). We analytically derive general conditions of the spectral characteristics of individual arrays which must be satisfied for the realization of highly-absorptive gradient multilayer nanostructured coatings. Two specific types of gradient coatings, (i) with the gradient of the size of the silver nanoparticles in the arrays and (ii) with the gradient of their surface concentration, are numerically studied in detail. The obvious advantages of the size-gradient coatings are revealed, in particular their total thickness of less than a wavelength. Multilayer coatings with a concurrent gradient of both concentration and mean particle size are fabricated from silver island films and their high and broadband absorption is demonstrated experimentally. PACS 78.67.Pt; 78.67.-n; 73.20.Mf; 42.25.Bs     

Multidimensional localized solitons

Recently it has been discovered that some nonlinear evolution equations in 2 + 1 dimensions, which are integrable by the use of the Spectral Transform, admit localized (in the space) soliton solutions. This article briefly reviews some of the main results obtained in the last 5 years thanks to the renewed interest in soliton theory due to this discovery. The theoretical tools needed to understand the unexpected richness of behaviour of multidimensional localized solitons during their mutual scattering are furnished. Analogies and especially discrepancies with the unidimensional case are stressed.     

An interpretation of the mean spherical approximation

The mean spherical approximation is shown to be derivable from a perturbation expansion where the reference system follows the Percur-Yevick approximation. Then the MSA may be interpreted as a first-order expansion in which the perturbation is averaged with respect to the low-density reference distribution function. This represents a generalization of an equivalent interpretation previously made with respect to the free energy of a polar fluid.     

Neue Eichmethode zur Nitrat- und Nitrit-Spurenbestimmung in Lebensmittelproben

Zusammenfassung Ein neues Verfahren zur Nitrat- und Nitritspurenbestimmung in verschiedenartigen Lebensmittelproben wird beschrieben. Dazu wird die massenspektrometrische Isotopenverdünnungsanalyse unter Verwendung eines ¹⁵NO ₃ ^– - und ¹⁵NO ₂ ^– -Indicators sowie die Messung negativer NO ₂ ^– -Thermionen im Massenspektrometer eingesetzt. Als definitive Methode liefert dieses Verfahren vergleichsweise richtige Analysenergebnisse, weshalb es sich vor allem auch als Eichverfahren eignet. Es werden Nitratgehalte in verschiedenen Milchpulver- und Schinkenproben im Bereich 3–170 ppm sowie getrocknete Proben von Pflanzenmaterialien im Bereich 0,1–2 Gew.-% analysiert. Dabei kann die Bestimmung letztgenannter Proben auch als Mikroanalyse erfolgen. Soweit es sich bei den Lebensmitteln um homogenisierte Proben handelt, liegen bei Konzentrationen >100 ppm die relativen Standardabweichungen des Verfahrens im Bereich 0,2–1%, bei Gehalten von 10–100 ppm im Bereich 1,5–3%. Die entsprechende Reproduzierbarkeit für parallel zum Nitrat bestimmtes Nitrit liegt bei 2–6% für Gehalte im Bereich 1–50 ppm. Die Nachweisgrenze für Nitrat und Nitrit ist etwa 0,2 ppm.

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New calibration method for the nitrate and nitrite trace determination in food samples

Summary A new analytical procedure for the determination of nitrate and nitrite traces in different food samples is described. Isotope dilution mass spectrometry is applied using a ¹⁵NO ₃ ^– and a ¹⁵NO ₂ ^– spike for the dilution technique and measuring negative NO ₂ ^– thermal ions in the mass spectrometer. This definitive method provides relatively accurate analysis results. Therefore, it is especially suitable as a calibration method. Nitrate contents in different milk powder samples and ham samples in the range of 3–170 ppm as well as dried samples of different plant materials in the range of 0.1–2% (by weight) are analysed. The determination of the plant material can also be carried out as micro analysis. So far as the food samples are homogeneous, the relative standard deviation of this method is in the range of 0.2–1% for nitrate contents of > 100 ppm and in the range of 1.5–3% for those of 10–100 ppm. The corresponding values for nitrite analysed in parallel to nitrate are 2–6% in the range of 1–50 ppm. The nitrate and nitrite detection limit is about 0.2 ppm.

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Vortrag anläßlich des Symposiums Anorganische Anionenanalytik, Regensburg, 19.–21. 9. 1984

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Der Deutsche Forschungsgemeinschaft und dem Fonds der Chemischen Industrie danken wir für die finanzielle Unterstützung.     

Aziridines. V. Etude par rmn de l'inversion de l'azote dans les aziridines symétriques à fonetion amine secondaire

This article describes the nitrogen inversion in two symétrie secondary aziridines. It was possible, by nmr, in avoiding the exchange of NH proton with water, to record spectra at different temperatures and to determine the temperature of coalescence. Persistance of coupling H? C? N? H after coalescence demonstrates the attribution of signals multiplicity to both invertomers.