Ephemeral and/or coloured nuonic hydrogen atoms

The unexpected and, in conventional terms, yet unexplained experimental results, obtained in systematic measurements of muon transfer from muonic hydrogen to sulphur and oxygen of sulphur dioxide, seem to violate the principle of reproducibility of muon transfer data. With the hypothesis of ephemeral muonic hydrogen atoms, the number of different hydrogen atoms can be reduced from four to two. This hypothesis does, however, not help to interpret the transfer data to helium, neon and argon, where the muonic hydrogen atoms seem to wear colours.     

Speciation of metal complexes with biomolecules by reversed-phase HPLC with ion-spray and inductively coupled plasma mass spectrometric detection

Complementarity of ion-spray MS and ICP-MS as detection techniques in reversed-phase HPLC for the characterization of metals complexed by biomacromolecules is discussed by the example of the speciation of metallothionein-bound cadmium. The commercially purified rabbit liver MT-2 isoform is eluted from a microbore C₈ column with a gradient of up to 50% methanol in acetate buffer (pH 6.0) to give one major and three minor peaks detected at 254 nm. The preparation is further characterized by using an ICP mass spectrometer interfaced with HPLC via a direct injection nebulizer which allows for the specific detection of cadmium down to the 10 ng mL^–1 level. On-line detection by mass spectrometry with an ion-spray (pneumatically-assisted electrospray) ion source further allows the determination of the molecular masses of the eluted compounds. Received: 30 July 1997 / Revised: 7 November 1997 /Accepted: 11 November 1997     

The solvent extraction of Cu(II), Ni(II), and Co(II) with diacetyl-mono-(2-quinolylhydrazone)

Summary A semi-automatic microliter sample injector with an 8-way motor-driven rotary valve was constructed for a conventional pneumatic nebulizer. After a 40-l sample was injected into an injection tee with a micro-syringe, nebulization and flushing the sample pathway with water followed by argon were automatically executed. An automatic peak detector/integrator was employed in each channel of a three-channel spectrometer for simultaneous multielement analysis. The relative standard deviation of the peak height for 1g Zr/ml was 1.7% and measuring time of one sample was about 1 min. Detection limits were 2 to 6 times higher than those in continuous feeding.

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Halbautomatische Injektion von Mikroliter-Proben in ein induktiv gekoppeltes Plasma zwecks simultaner Multielementanalyse

Zusammenfassung Ein halbautomatischer Injektor für Mikroliterproben mit einem motorgetriebenen 8-Weg-Ventil für ein konventionelles Vernebelungsgerät wurde konstruiert. Nachdem eine 40-l-Probe mit einer Mikroinjektionsspritze in ein Injektions-T-Stück eingeführt ist, erfolgt automatisch Vernebelung, dann Spülung des Probenweges zunächst mit Wasser, dann mit Argon. Ein automatischer Spitzen-Detektor/Integrator in jedem der drei Kanäle des Spektrometers ermöglicht die gleichzeitige Multielementanalyse. Die rel. Standardabweichung der Spitzenhöhe für 1g Zr/ml betrug 1,7%, die Zeit für die Messung einer Probe ungefähr eine Minute. Die Nachweisgrenzen sind 2- bis 6mal höher als bei kontinuierlicher Zugabe.

     

Polarographie schwefelhaltiger Proteine

Zusammenfassung An kristallisierten Enzymen des biologischen Stoffwechsel wird gezeigt, daß bei der Polarographie nur die schwefelhaltigen Proteine katalytische Wasserstoffwellen geben. Von den in der Literatur beschriebenen Doppelstufen der Proteine besitzt nur die im negativeren Potentialbereich liegende Welle die eigentliche katalytische Funktion. Die erste Vorwelle von Proteinen verschwindet, wenn die polarographische Messung bei 0° C durchgeführt wird.In Proteinen sind nur Disulfidgruppen katalytisch wirksam. Sogenannte reine Sulfhydryl-Enzyme haben keinen katalytischen Effekt. Typische SH-Enzyme können jedoch polarographisch als p-Chloromercuribenzoatkomplexe gemessen werden.Durch Harnstoffzusatz bei der polarographischen Messung von Proteinen gelingt es, zwischen maskierten und freien Sulfhydryl- oder Disulfidgruppen an Enzymen zu definieren.Auszug aus der Dissertationsschrift H. Katzlmeier, Technische Hochschule München (1959).     

Diacetyl-bis-(2-pyridyl)hydrazone as an extracting agent for Cu(II), Co(II), and Ni(II)

Summary DbPH, a quadridentate chelating agent, was studied as a solvent extraction reagent for Cu(II), Co(II), and Ni(II). In all cases 11 complexes were extracted; however for Cu(II) and Co(II) ion-paired species exist, while for Ni(II) only neutral complexes were extracted. In all cases an extraction efficiency of 35–60% was observed unlike the greater than 90% observed for similar mono-hydrazone derivatives. The steric hindrance probably present in the bis adduct prevented a more efficient extraction.

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Diacetyl-bis-(2-pyridyl)hydrazon (DbPH) als Extraktionsmittel für Cu(ll), Co(II) und Ni(II)

Zusammenfassung DbPH bildet mit Cu(II), Co(II) und Ni(II) Komplexverbindungen im Verhältnis 11; diese sind für Cu und Co ionisierbar, im Falle des Ni läßt sich ein neutraler Komplex extrahieren. Die Extraktion erreicht jedenfalls nur 35–60% im Gegensatz zu mehr als 90% bei ähnlich gebauten Monohydrazon-Derivaten. Sterische Hinderung dürfte hierfür die Ursache sein.

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Presented at the 18th Middle Atlantic Regional Meeting of the American Chemical Society, Newark, New Jersey, May 21, 1984.     

Matrix-isolation-FTIR spectroscopy with an integrating sphere

The use of an integrating sphere for the measurement of absorption spectra of thin films is described. The thin film (for example a rare gas matrix) is grown directly on the inside surface of the sphere. Multiple reflections inside the integrating sphere lead to significant enhancement of weak absorptions of the film, increasing the sensitivity of such measurements.     

Photoinduced electron transfer at liquid|liquid interfaces. Part VII. Correlation between self-organisation and structure of water-soluble photoactive species

The self-organisation of a variety of dyes at the water|1,2-dichloroethane interface was studied by admittance measurements, photocurrent–potential curves and light polarisation anisotropy of the photocurrent. The heterogeneous photo-oxidation of ferrocene was studied at interfaces sensitised by Sn(IV) meso-tetra-(4-carboxyphenyl) porphyrin dichloride (SnTPPC), chlorin e-6, protoporphyrin IX (protoIX) and Fe(III) protoporphyrin IX chloride (Fe-protoIX). Cyclic voltammograms and capacitance voltage curves exhibit different features associated with the self-assembly of the dye species at the liquid|liquid boundary. In the case of SnTPPC, the capacitance curves displayed the characteristic responses commonly associated with the specific adsorption of ionic species. On the other hand, chlorin e-6, protoIX and Fe-protoIX show rather complex behaviour suggesting not only changes in the excess charge but also in the dielectric permittivity of the interface. Differences in the photocurrent efficiency were also observed under the same experimental conditions. The relative magnitude of the photocurrent responses were rationalised in terms of the phenomenological electron transfer rate constant, the photon capture cross-sections and the lifetime of the triplet state as obtained from nanosecond flash photolysis. Finally, the average molecular orientation of the adsorbed photoactive species was estimated from the photocurrent dependence on the angle of light polarisation in total internal reflection. The results show a clear correlation between the orientation of the transition dipole and the distribution of the peripheral carboxyl groups responsible for the hydrophilic nature of the dyes.     

Nonlinear desingularization in certain free-boundary problems

We consider a nonlinear, elliptic, free-boundary problem involving an initially unknown setA that represents, for example, the cross-section of a steady vortex ring or of a confined plasma in equilibrium. The solutions are characterized by a variational principle which allows us to describe their behaviour under a limiting process such that the diameter ofA tends to zero, while the solutions degenerate to the solution of a related linear problem. This limiting solution is the sum of the Green function of the linear operator and of a smooth function satisfying the boundary conditions. Mathematically speaking, this limiting process, that we call nonlinear desingularization, is a novel kind of bifurcation phenomenon since the nonlinear effect here involves smoothing the singularity of the associated linear problem.Research partially supported by A FOSR and NSF grants     

Exploiting C3-symmetry in the dynamic coordination of a chiral trisoxazoline to copper(II): improved enantioselectivity, and catalyst stability in asymmetric lewis acid catalysis

Chiral C3-symmetric trisoxazolines are highly efficient stereodirecting ligands in enantioselective Cu(II) Lewis acid catalysis which is based on the concept of a stereoelectronic hemilability of the divalent copper; in direct comparison with the analogous bisoxazoline systems they are more efficient in the enantioselective alpha-amination as well as the enantioselective Mannich reaction of prochiral beta-ketoesters.