Measurement of γp→K + Λ and γp→K + Σ 0 at photon energies up to 1.47 GeV

The reactions pK ⁺ and pK ^{+ 0} have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the polarization and, for the first time, the ⁰ polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both and ⁰ is substantial at all energies and varies strongly with the production angle.This work is supported by the Bundesminister für Forschung und Technologie (BMFT), FK 06 BN 621 I     

Photoproduction of neutral pions in the region of the fourth nucleon resonance

We report the measurement of the differential cross section of the reaction γ +p→π⁰ +p at a photon energy of 1.4 GeV and pion c.m. angles between 60 and 175 degrees. The angular distribution confirms the simple quark model prediction of a pure magnetic excitation of theF ₃₇ (1950) resonance.     

Four-color fluorescence correlation spectroscopy realized in a grating-based detection platform

We have developed a filterless multicolor detection unit for fluorescence correlation spectroscopy (FCS). This grating-based setup is continuously tunable for multicolor separation and is thus a powerful alternative to the classical cascade of dichroic mirrors and filters. Our tailored platform allows for accommodation of up to 15 detection channels covering the entire visible spectral range. As a proof of principle, we successfully demonstrate simultaneous FCS of four distinct fluorescent quantum dot species being mixed in aqueous solution. Grating-based detection allows for spectral high-resolution FCS in a stable and compact setup and is a feasible tool for quantitative investigation of complexbiomolecular dynamics on a single molecule level.     

Future teachers’ competence to plan a lesson: first results of a six-country study on the efficiency of teacher education

The study "Mathematics Teaching in the 21st Century (MT21)" focuses beyond others on the measurement of teachers’ general pedagogical knowledge (GPK). GPK is regarded as a latent construct embedded in a larger theory of teachers’ professional competence. It is laid out how GPK was defined and operationalized. As part of an international comparison GPK was measured with several complex vignettes. In the present paper, the results of future mathematics teachers’ knowledge from four countries (Germany, South Korea, Taiwan, and the US) with very different teacher-education systems are presented. Significant and relevant differences between the four countries as well as between future teachers at the beginning and at the end of teacher education were found. The results are discussed with reference to cultural discourses about teacher education.     

Photoproduction of π+ mesons on polarized protons at photon energies between 0.5 and 2.2 GeV

The target asymmetry T = (σ↑ ? σ↓)/(σ↑ + σ↓) for the reaction γp → π⁺n has been measured at the Bonn 2.5 GeV electron synchrotron for a pion c.m. angle of 40° and γ energies between 0.5 and 2.2 GeV. Butanol was used as the target material. About 35% of the protons could be polarized using the dynamic-polarization method in a continuous-flow cryostat operating at 1°K and 25 kG. The π⁺ mesons were detected in a magnetic-spectrometer system. Considerable structure in the asymmetry was observed.