The first measurement is reported of the double-polarization observable G in photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid ...angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand {\gamma}p -> p{\pi} 0 as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N (1535) with spin-parity J^P = 1/2^- and N (1520) with J^P = 3/2^- . In the third resonance region, where N (1680) with J^P = 5/2^+ production dominates, the new data are reasonably close to the predictions.
The first measurements of the beam-target-helicity-asymmetries \(E\) and \(G\) in the photoproduction of \(\omega\)-mesons off protons at the CBELSA/TAPS experiment are reported. \(E\) (\(G\)) was ...measured using circularly (linearly) polarised photons and a longitudinally polarised target. \(E\) was measured over the photon energy range from close to threshold (\(E_\gamma = 1108\)~MeV) to \(E_\gamma = 2300\)~MeV and \(G\) at a single energy interval of \(1108 < E_\gamma <1300\)~MeV. Both measurements cover the full solid angle. The observables \(E\) and \(G\) are highly sensitive to the contribution of baryon resonances, with \(E\) acting as a helicity filter in the \(s\)-channel. The new results indicate significant \(s\)-channel resonance contributions together with contributions from \(t\)-channel exchange processes. A partial wave analysis reveals strong contributions from the partial waves with spin-parity \(J^P=3/2^+, 5/2^+\), and \(3/2^-\).
Data on the polarization observables T, P, and H for the reaction \(\gamma p\to p\pi^0\) are reported. Compared to earlier data from other experiments, our data are more precise and extend the ...covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.
We report on the development of a GEM-based TPC prototype for the PANDA experiment. The design and requirements of this device will be illustrated, with particular emphasis on the properties of the ...recently tested GEM-detector, the characterization of the read-out electronics and the development of the tracking software that allows to evaluate the GEM-TPC data.
In a search for \(\omega\) mesic states, the production of \(\omega\)-mesons in coincidence with forward going protons has been studied in photon induced reactions on \(^{12}\)C for incident photon ...energies of 1250 - 3100 MeV. The \(\pi^0 \gamma\) pairs from decays of bound or quasi-free \(\omega\)-mesons have been measured with the CBELSA/TAPS detector system in coincidence with protons registered in the MiniTAPS forward array. Structures in the total energy distribution of the \(\pi^0 \gamma\) pairs, which would indicate the population and decay of bound \(\omega~^{11}\)B states, are not observed. The \(\pi^0 \gamma\) cross section of 0.3 nb/MeV/sr observed in the bound state energy regime between -100 and 0 MeV may be accounted for by yield leaking into the bound state regime because of the large in-medium width of the \(\omega\)-meson. A comparison of the measured total energy distribution with calculations suggests the real part \(V_0\) of the \(\omega~^{11}\)B potential to be small and only weakly attractive with \(V_0(\rho=\rho_0) = -15\pm\) 35(stat) \(\pm\)20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100 - 150 MeV.
The Munich ChronoType Questionnaire (MCTQ) has now been available for more than 15 years and its original publication has been cited 1240 times (Google Scholar, May 2019). Additionally, its online ...version, which was available until July 2017, produced almost 300,000 entries from all over the world (MCTQ database). The MCTQ has gone through several versions, has been translated into 13 languages, and has been validated against other more objective measures of daily timing in several independent studies. Besides being used as a method to correlate circadian features of human biology with other factors-ranging from health issues to geographical factors-the MCTQ gave rise to the quantification of old wisdoms, like "teenagers are late", and has produced new concepts, like social jetlag. Some like the MCTQ's simplicity and some view it critically. Therefore, it is time to present a self-critical view on the MCTQ, to address some misunderstandings, and give some definitions of the MCTQ-derived chronotype and the concept of social jetlag.
Internal clocks driving rhythms of about a day (circadian) are ubiquitous in animals, allowing them to anticipate environmental changes. Genetic or environmental disturbances to circadian clocks or ...the rhythms they produce are commonly associated with illness, compromised performance or reduced survival. Nevertheless, some animals including Arctic mammals, open sea fish and social insects such as honeybees are active around-the-clock with no apparent ill effects. The mechanisms allowing this remarkable natural plasticity are unknown. We generated and validated a new and specific antibody against the clock protein PERIOD of the honeybee Apis mellifera (amPER) and used it to characterize the circadian network in the honeybee brain. We found many similarities to Drosophila melanogaster and other insects, suggesting common anatomical organization principles in the insect clock that have not been appreciated before. Time course analyses revealed strong daily oscillations in amPER levels in foragers, which show circadian rhythms, and also in nurses that do not, although the latter have attenuated oscillations in brain mRNA clock gene levels. The oscillations in nurses show that activity can be uncoupled from the circadian network and support the hypothesis that a ticking circadian clock is essential even in around-the-clock active animals in a constant physical environment.
Earlier human activity relative to sunrise and sunset, the very essence of daylight saving time, is linked with health and safety detriments in humans. A new study predicts that deer, at least, may ...benefit from earlier human activity through reduced deer-vehicle collisions.
In humans, the most important zeitgeber for entrainment is light. Laboratory studies have shown that meaningful changes in light exposure lead to phase shifts in markers of the circadian clock. In ...natural settings, light is a complex signal varying with external conditions and individual behaviors; nonetheless, phase of entrainment is assumed to be fairly stable. Here, we investigated the influence of season and weekly schedule (as indicators of variation in light landscapes) on phase of entrainment. Using a within‐subjects design (N = 33), we assessed dim‐light melatonin onset (DLMO) as a circadian phase marker in humans, on workdays and work‐free days, in summer (under daylight saving time) and in winter, while also estimating sleep times from actimetry. Our mixed‐model regressions show that both season and weekly structure are linked with changes in phase of entrainment and sleep. In summer, both DLMO and sleep times were about 1 hour earlier compared to winter, and sleep duration was shorter. On work‐free days, DLMO and sleep times were later, and their phase relationship differed more relative to workdays. All these effects were stronger in later chronotypes (those who habitually sleep late). Our results confirm that phase of entrainment is earlier when stronger zeitgebers are present (summer) and show that it relates to midday or midnight rather than sunrise or sunset. Additionally, they suggest that late chronotypes are capable of rapid phase shifts each week as they move between workdays and work‐free days, stimulating interesting questions about the stability of circadian phase under natural conditions.
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