Experimental and theoretical aspects of the formation of radical cations from tripyrrolidinobenzenes and their follow-up reactions

Tripyrrolidinobenzene radical cations(1*+), obtained from the corresponding arenes by oxidation with silver nitrate, are specially stabilized and thus allow specific reaction pathways of arene radical cations to be investigated separately and individually. Radical cations 1*+ ,for instance, generated under exclusion of oxygen, undergo dimerization to 2, or they abstract hydrogen from the solvent to form 3. In a pure oxygen atmosphere, the O2 reaction products 6 and 7 are formed, respectively, either exclusively or together with 2 and 3. Kinetic measurements give the following order of reactivity for these individual processes: reaction with O2 > dimerization. > H-abstraction from solvent. The changes in the product spectrum upon modification of the reaction conditions are in accord with the kinetic results. The dimeric u complexes 2 show surprisingly facile dissociation into two radical cations, two (1*+)with a much higher dissociation rate for the alkyl derivatives 2b-d than for 2a. Dissociation is enhanced substantially by light or in the presence of π donors. Individual product formation, rate of reactions of the radical cations 1*+, and photochemical cleavage of the dimeric σ complexes 2 can be rationalized, by qualitative and quantitative MO considerations, in terms of their relative frontier orbital energies

Catching Element Formation In The Act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.Comment: 14 pages including 3 figure

Welche Macht darf es denn Sein? Tracing ‘Power’ in German Foreign Policy Discourse

The relationship between ‘Germany’ and ‘power’ remains a sensitive issue. While observers tend to agree that Germany has regained the status of the most powerful country in Europe, there is debate whether that is to be welcomed or whether that is a problem. Underpinning this debate are views, both within Germany and amongst its neighbours, regarding the kind of power Germany has, or should (not) have. Against this backdrop, the article reviews the dominant role conceptions used in the expert discourse on German foreign policy since the Cold War that depict Germany as a particular type of ‘power’. Specifically, we sketch the evolution of three prominent conceptions (constrained power, civilian power, hegemonic power) and the recent emergence of a new one (shaping power). The article discusses how these labels have emerged to give meaning to Germany’s position in international relations, points to their normative and political function, and to the limited ability of such role images to tell us much about how Germany actually exercises power

First international descriptive and interventional survey for cholesterol and non-cholesterol sterol determination by gas- and liquid- chromatography–Urgent need for harmonisation of analytical methods

Serum concentrations of lathosterol, the plant sterols campesterol and sitosterol and the cholesterol metabolite 5α-cholestanol are widely used as surrogate markers of cholesterol synthesis and absorption, respectively. Increasing numbers of laboratories utilize a broad spectrum of well-established and recently developed methods for the determination of cholesterol and non-cholesterol sterols (NCS). In order to evaluate the quality of these measurements and to identify possible sources of analytical errors our group initiated the first international survey for cholesterol and NCS. The cholesterol and NCS survey was structured as a two-part survey which took place in the years 2013 and 2014. The first survey part was designed as descriptive, providing information about the variation of reported results from different laboratories. A set of two lyophilized pooled sera (A and B) was sent to twenty laboratories specialized in chromatographic lipid analysis. The different sterols were quantified either by gas chromatography-flame ionization detection, gas chromatography- or liquid chromatography-mass selective detection. The participants were requested to determine cholesterol and NCS concentrations in the provided samples as part of their normal laboratory routine. The second part was designed as interventional survey. Twenty-two laboratories agreed to participate and received again two different lyophilized pooled sera (C and D). In contrast to the first international survey, each participant received standard stock solutions with defined concentrations of cholesterol and NCS. The participants were requested to use diluted calibration solutions from the provided standard stock solutions for quantification of cholesterol and NCS. In both surveys, each laboratory used its own internal standard (5α-cholestane, epicoprostanol or deuterium labelled sterols). Main outcome of the survey was, that unacceptably high interlaboratory variations for cholesterol and NCS concentrations are reported, even when the individual laboratories used the same calibration material. We discuss different sources of errors and recommend all laboratories analysing cholesterol and NCS to participate in regular quality control programs

Zwischen Trinklied und Echoraum

Dieser Artikel beschäftigt sich mit dem chorischen Theater. Er rückt dabei die Frage nach der klanglichen Qualität der Aufführung ins Zentrum. Dabei werden zwei Beispiele vorgestellt, die zugleich zwei Richtungen des chorischen Theaters vorgeben. Das erste ist ein spontanes Trinklied, welches Studenten in einer Mensa einer Universität anstimmen. Der Klang ist hier polarisierend, wird verstörend und zugleich ansteckend. Dieser spontanen Aufführung im öffentlichen Raum wird ein Echoraum zur Seite gestellt, den der Regisseur Ulrich Rasche zum Jahrestag der Ausschreitungen im Stuttgarter Schlossgarten im Herbst 2010 inszenierte. Der Klang regt hier zur Reflexion und Erinnerung an, er distanziert vom Geschehen. Es geht also jeweils um eine ästhetische und zugleich soziale Frage: Inwiefern zieht der Sound des chorischen Sprechens und Singens den Zuschauer und Zuhörer ins Geschehen hinein? Vor dem Hintergrund der Ästhetik des Performativen und der neuen Phänomenologie wird die soziale Dimension der klanglichen Kommunikation entwickelt