Refine
Year of publication
- 2015 (2651) (remove)
Document Type
- Article (911)
- Part of Periodical (357)
- Book (333)
- Doctoral Thesis (188)
- Working Paper (180)
- Contribution to a Periodical (174)
- Report (161)
- Review (142)
- Part of a Book (100)
- Preprint (55)
Language
- German (1282)
- English (1262)
- Portuguese (26)
- French (18)
- Spanish (17)
- Croatian (14)
- Italian (12)
- Multiple languages (12)
- Turkish (5)
- Hebrew (1)
Is part of the Bibliography
- no (2651) (remove)
Keywords
- Literatur (44)
- Deutsch (37)
- Islamischer Staat (34)
- Rezension (30)
- taxonomy (29)
- IS (25)
- Rezeption (23)
- Terrorismus (23)
- new species (22)
- Deutschland (20)
Institute
- Präsidium (336)
- Medizin (253)
- Gesellschaftswissenschaften (239)
- Physik (185)
- Wirtschaftswissenschaften (149)
- Exzellenzcluster Die Herausbildung normativer Ordnungen (118)
- Center for Financial Studies (CFS) (115)
- Biowissenschaften (102)
- Frankfurt Institute for Advanced Studies (FIAS) (97)
- Informatik (96)
The method of relative self absorption is based on the technique of nuclear resonance fluorescence measurements. It allows for a model-independent determination of ground-state transition widths, natural level widths, and, consequently, of branching ratios to the ground state for individual excitations. Relative self–absorption experiments have been performed on the nuclei 6Li and 140Ce. In order to investigate the total level width for the 0+1, T = 1 level at 3563 keV in 6Li, a high-precision self-absorption measurement has been performed. In the case of 140Ce, self absorption has been applied for the first time to study decay widths of dipole-excited states in the energy regime of the pygmy dipole resonance.
We analysed our experimental recent findings of the dipole response of the odd-mass stable nucleus 205Tl within the quasi-particle phonon model. Using the phonon basis constructed for the neighbouring 204Hg and wave function configurations for 205Tl consisting of a mixture of quasiparticle ⊗ N-phonon configurations (N=0,1,2), only one group of fragmented dipole excited states has been reproduced at 5.5 MeV in comparison to the experimental distribution which shows a second group at about 5 MeV. The computed dipole transition strengths are mainly of E1 character which could be associated to the pygmy dipole resonance.
We present a nucleosynthesis sensitivity study for the γ-process in a Supernova type II model within the NuGrid research platform. The simulations aimed at identifying the relevant local production and destruction rates for the p-nuclei of molybdenum and at determining the sensitivity of the final abundances to these rates. We show that local destruction rates strongly determine the abundance of 92Mo and 94Mo, and quantify the impact.
The p nucleus 92Mo is believed to be mainly produced through photodisintegration reactions in type II supernovae. However, this production scenario cannot solely account for the observed solar relative isotopic abundance of 92Mo. Additional production scenarios have been suggested to explain this discrepancy. One of these scenarios could be the production of 92Mo in type Ia supernovae via a chain of proton-capture reactions. To verify this scenario, an accurate knowledge of the involved reaction rates is important. We measured the cross section of 90Zr(p,γ) reaction using an enriched 90Zr target by means of in-beam γ-ray spectroscopy in the energy range between 3.6MeV and 5.1MeV. Since the reactions 90Zr(p,γ) and 91Zr(p,n) produce the same nucleus, the contributions of both reactions have to be disentangled. This procedure is explained in this contribution in detail.
Two types of particles exist in the atmosphere, primary and secondary particles. While primary particles such as soot, mineral dust, sea salt particles or pollen are introduced directly as particles into the atmosphere, secondary particles are formed in the atmosphere by condensation of gases. The formation of such new aerosol particles takes place frequently and at a broad variety of atmospheric conditions and geographic locations. A considerable fraction of the atmospheric particles is formed by such nucleation processes. The newly formed particles may grow by condensation to sizes where they are large enough to act as cloud condensation nuclei and therefore may affect cloud properties. The fundamental processes of aerosol nucleation are described and typical atmospheric observations are discussed. Two recent studies are introduced that potentially change our current understanding of atmospheric nucleation substantially.
Due to their penetrating nature, electromagnetic probes, i.e., lepton-antilepton pairs (dileptons) and photons are unique tools to gain insight into the nature of the hot and dense medium of strongly-interacting particles created in relativistic heavy-ion collisions, including hints to the nature of the restoration of chiral symmetry of QCD. Of particular interest are the spectral properties of the electromagnetic current-correlation function of these particles within the dense and/or hot medium. The related theoretical investigations of the in-medium properties of the involved particles in both the partonic and hadronic part of the QCD phase diagram underline the importance of a proper understanding of the properties of various hadron resonances in the medium.
The decay behavior of low-lying dipole states in 140Ce was investigated exploiting the γ3-setup at the HIγS facility using quasi-monochromatic photon beams. Branching ratios of individual excited states as well as average branching ratios to low-lying states have been extracted using γ – γ coincidence measurements. The comparison of the average branching ratios to QPM calculations shows a remarkable agreement between experiment and theory in the energy range from 5.0 to 8.5 MeV.
A series of photon scattering experiments has been performed on the double-beta decay partners 76Ge and 76Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis.
Intrinsic covariation of brain activity has been studied across many levels of brain organization. Between visual areas, neuronal activity covaries primarily among portions with similar retinotopic selectivity. We hypothesized that spontaneous inter-areal co-activation is subserved by neuronal synchronization. We performed simultaneous high-density electrocorticographic recordings across several visual areas in awake monkeys to investigate spatial patterns of local and inter-areal synchronization. We show that stimulation-induced patterns of inter-areal co-activation were reactivated in the absence of stimulation. Reactivation occurred through both, inter-areal co-fluctuation of local activity and inter-areal phase synchronization. Furthermore, the trial-by-trial covariance of the induced responses recapitulated the pattern of inter-areal coupling observed during stimulation, i.e. the signal correlation. Reactivation-related synchronization showed distinct peaks in the theta, alpha and gamma frequency bands. During passive states, this rhythmic reactivation was augmented by specific patterns of arrhythmic correspondence. These results suggest that networks of intrinsic covariation observed at multiple levels and with several recording techniques are related to synchronization and that behavioral state may affect the structure of intrinsic dynamics.
We discuss the behavior of dynamically-generated charmed baryonic resonances in matter within a unitarized coupled-channel model consistent with heavy-quark spin symmetry. We analyze the implications for the formation of D-meson bound states in nuclei and the propagation of D mesons in heavy-ion collisions from RHIC to FAIR energies.
In addition to the well-established quadrupole mixed-symmetry states, octupole and hexadecapole excitations with mixed-symmetry character have been recently proposed for the N = 52 isotones 92Zr and 94Mo. We performed two inelastic proton-scattering experiments to study this kind of excitations in the heaviest stable N = 52 isotone 96Ru. From the combined experimental data of both experiments absolute transition strengths were extracted.
Plant communities provide floral resource-landscapes for pollinators. Yet, it is insufficiently understood how these landscapes shape pollinator-mediated interactions among multiple plant species. Here, we study how pollinators and the seed set of plants respond to the distribution of a floral resource (nectar sugar) in space and across plant species, inflorescences and flowering phenologies. In a global biodiversity hotspot, we quantified floral resource-landscapes on 27 sites of 4 ha comprising 127,993 shrubs of 19 species. Visitation rates of key bird pollinators strongly depended on the phenology of site-scale resource amounts. Seed set of focal plants increased with resources of conspecific neighbours and with site-scale resources, notably with heterospecific resources of lower quality (less sugar per inflorescence). Floral resources are thus a common currency determining how multiple plant species interact via pollinators. These interactions may alter conditions for species coexistence in plant communities and cause community-level Allee effects that promote extinction cascades.
Die Sammlung von Aufsätzen des Frankfurter Lehrers, Erziehungswissenschaftlers und Soziologen besteht aus drei Teilen: In dem ersten Teil wird der Frage nachgegangen, aus welcher Perspektive heraus Unterricht hermeneutisch erschlossen werden und in welche Theorietradition sich eine hermeneutische Unterrichtsforschung stellen kann bzw. sollte. In dem zweiten Teil sind sodann Aufsätze versammelt, in denen grundlegende Fragen des Unterrichts neu aufgegriffen werden: Welche Probleme stellen sich zu Beginn einer jeden Unterrichtsstunde und welche Möglichkeiten gibt es, diese zu lösen? Worauf beruht die Autorität einer Lehrperson und wie wird diese im Unterricht durch die beteiligten Akteure kommunikativ erzeugt oder auch vermindert? Wie sind Unterrichtsstörungen zu deuten und wie ist mit ihnen umzugehen, wenn davon ausgegangen wird, dass diese Momente eines Interaktionsprozesses sind, die jeweils situativ emergieren? Was bedeutet es für Schüler, sich am Unterricht zu beteiligen? Und welche Situationen können sich ergeben, wenn die Schülerschaft einer Klasse in kultureller Hinsicht äußerst heterogen ist? Die Art und Weise, wie diese Fragen behandelt werden, ist nicht nur durch das besondere methodische Vergehen gekennzeichnet, sondern auch durch einen kasuistischen Zugang: Auf der Basis theoretischer Vorüberlegungen wird stets ein empirisches Beispiel herangezogen, um an diesem diese theoretischen Überlegungen nicht nur zu überprüfen, sondern schließlich auch weiterzuentwickeln. Dabei ist die Stoßrichtung stets dieselbe: Die Vielzahl möglicher Deutungen von Unterricht wird nicht bestritten, doch die Fruchtbarkeit einer dezidiert pädagogischen Deutung dieses Geschehens wird immer wieder hervorgehoben. Abgeschlossen wird der Band mit Aufsätzen zu Fragen der Professionalisierung von Lehrerinnen und Lehrern. So wird das Verhältnis zwischen der Didaktik, vor allem didaktischer Theorien und der Theorie der Professionalisierung ausgelotet. Und es wird der Frage nachgegangen, welche Konsequenzen sich aus der pädagogischen Kasuistik für die Professionalisierung von Lehrpersonen sowie für die Theorie der Professionalisierung ziehen lassen. Auch diese Fragen werden jeweils mit Bezug auf empirische Beispiele erörtert. (DIPF/Verlag)
n this paper we report on the investigation of baryonic resonance production in proton-proton collisions at the kinetic energies of 1.25 GeV and 3.5 GeV, based on data measured with HADES. Exclusive channels npπ+ and ppπ0 as well as ppe+e− were studied simultaneously in the framework of a one-boson exchange model. The resonance cross sections were determined from the one-pion channels for Δ(1232) and N(1440) (1.25 GeV) as well as further Δ and N* resonances up to 2 GeV/c2 for the 3.5 GeV data. The data at 1.25 GeV energy were also analysed within the framework of the partial wave analysis together with the set of several other measurements at lower energies. The obtained solutions provided the evolution of resonance production with the beam energy, showing a sizeable non-resonant contribution but with still dominating contribution of Δ(1232)P33. In the case of 3.5 GeV data, the study of the ppe+e− channel gave the insight on the Dalitz decays of the baryon resonances and, in particular, on the electromagnetic transition form-factors in the time-like region. We show that the assumption of a constant electromagnetic transition form-factors leads to underestimation of the yield in the dielectron invariant mass spectrum below the vector mesons pole. On the other hand, a comparison with various transport models shows the important role of intermediate ρ production, though with a large model dependency. The exclusive channels analysis done by the HADES collaboration provides new stringent restrictions on the parameterizations used in the models.
his contribution aims to give a basic overview of the latest results regarding the production of resonances in different collision systems. The results were extracted from experimental data collected with HADES that is a multipurpose detector located at the GSI Helmholtzzentrum, Darmstadt. The main points discussed here are: the properties of the strange resonances Λ(1405) and Σ(1385), the role of Δ’s as a source of pions in the final state, the production dynamics reflected in form of differential cross sections, and the role of the ϕ meson as a source for K− particles.
The neutron capture cross section of the s-process branch nucleus 63Ni affects the abundances of other nuclei in its region, especially 63Cu and 64Zn. In order to determine the energy-dependent neutron capture cross section in the astrophysical energy region, an experiment at the Los Alamos National Laboratory has been performed using the calorimetric 4πBaF2 array DANCE. The (n,γ) cross section of 63Ni has been determined relative to the well-known 197Au standard with uncertainties below 15%. Various 63Ni resonances have been identified based on the Q value. Furthermore, the s-process sensitivity of the new values was analyzed with the new network calculation tool NETZ.
The ALICE detector at the LHC is used to study the properties of the Quark-Gluon Plasma produced in heavy-ion collisions. As a reference measurement, also the analysis of proton-proton (pp) collisions is very important. In the study presented here, event-by-event fluctuations of the mean transverse momentum are analysed in pp collisions at √s = 0.9, 2.76 and 7 TeV, and Pb–Pb collisions at √sNN = 2.76 TeV as a function of the charged-particle multiplicity. In both systems, dynamical fluctuations beyond the statistical expectation are observed. In pp collisions, no significant dependence on collision energy is found, even in comparison to inclusive results at much lower collision energies. Likewise, central A–A collisions show only little dependence on collision energy. The multiplicity dependence observed in peripheral Pb–Pb data is in agreement with that in pp collisions. Going to more central Pb–Pb collisions, a clear deviation from this trend is found, reaching a significant reduction of the fluctuations in most central collisions. Comparisons toMonte Carlo event generators show good agreement in pp, but rather large differences in Pb–Pb collisions.