University of Marburg

About: University of Marburg is a education organization based out in Marburg, Germany. It is known for research contribution in the topics: Population & Virus. The organization has 23195 authors who have published 42907 publications receiving 1506069 citations. The organization is also known as: Philipps University of Marburg & Philipps-Universität.

Structural and oxidation state changes of the photosystem II manganese complex in four transitions of the water oxidation cycle (S0 --> S1, S1 --> S2, S2 --> S3, and S3,4 --> S0) characterized by X-ray absorption spectroscopy at 20 K and room temperature.

Abstract: Structural and electronic changes (oxidation states) of the Mn4Ca complex of photosystem II (PSII) in the water oxidation cycle are of prime interest. For all four transitions between semistable S-states (S0 → S1, S1 → S2, S2 → S3, and S3,4 → S0), oxidation state and structural changes of the Mn complex were investigated by X-ray absorption spectroscopy (XAS) not only at 20 K but also at room temperature (RT) where water oxidation is functional. Three distinct experimental approaches were used: (1) illumination-freeze approach (XAS at 20 K), (2) flash-and-rapid-scan approach (RT), and (3) a novel time scan/sampling-XAS method (RT) facilitating particularly direct monitoring of the spectral changes in the S-state cycle. The rate of X-ray photoreduction was quantitatively assessed, and it was thus verified that the Mn ions remained in their initial oxidation state throughout the data collection period (>90%, at 20 K and at RT, for all S-states). Analysis of the complete XANES and EXAFS data sets (20 K and ...

Ultrafast field-induced dissociation of excitons in conjugated polymers

Abstract: We present a time-resolved study of the field-induced luminescence quenching in poly(phenylphenylenevinylene) using femtosecond luminescence spectroscopy. The dynamic quenching of the luminescence reveals a delay between the generation of excitons and their breakup into geminate electron-hole pairs. We explain the data by the interplay of the dissociation and the spectral relaxation of the excitons within an inhomogeneously broadened density of states. Our experimental results suggest that the photocarriers in conjugated polymers are not formed directly but result from dissociation of excitons.

The HERMES Spectrometer

Abstract: The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and 3 He. These data give information on the spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers (micro-strip gas chambers, drift and proportional chambers) in front of and behind a 1.3 T.m magnetic field, as well as an extensive set of detectors for particle identification (a lead-glass calorimeter, a pre-shower detector, a transition radiation detector, and a threshold Cherenkov detector). Two of the main features of the spectrometer are its good acceptance and identification of both positrons and hadrons, in particular pions. These characteristics, together with the purity of the targets, are allowing HERMES to make unique contributions to the understanding of how the spins of the quarks contribute to the spin of the nucleon.

Can we really reduce ethnic prejudice outside the lab? A meta-analysis of direct and indirect contact interventions

Abstract: The present meta-analysis tested the effectiveness of contact-based interventions for the reduction of ethnic prejudice. Up to now, a meta-analysis summarizing the results of real-world interventions that rest on the intergroup contact theory has been missing. We included evaluations of programs realizing direct (i.e., face-to-face) and/or indirect (i.e., extended or virtual) contact in real-world settings outside the lab. The interventions' effectiveness was tested shortly after their end (k = 123 comparisons, N = 11 371 participants) and with a delay of at least 1 month (k = 25, N = 1650). Our data show that contact interventions improve ethnic attitudes. Importantly, changes persist over time. Furthermore, not only direct but also indirect contact interventions are successful. In addition, contact programs are effective even in the context of a serious societal conflict (e.g., in the Middle East). Although changes are typically larger for ethnic majorities, there is an impact on minorities, too. Finally, contact interventions not only improve attitudes toward individuals involved in the program, their effects also generalize to outgroups as a whole. In sum, social psychology provides an intervention for prejudice reduction that can be successfully implemented in the practical field. Copyright © 2015 John Wiley & Sons, Ltd.

Ebola virus: from discovery to vaccine

Abstract: Ebola virus, being highly pathogenic for humans and non-human primates and the subject of former weapons programmes, is now one of the most feared pathogens worldwide. In addition, the lack of pre- and post-exposure interventions makes the development of rapid diagnostics, new antiviral agents and protective vaccines a priority for many nations. Further insight into the ecology, immunology and pathogenesis of Ebola virus will promote the delivery of these urgently required tools.