Transparenz und Evaluierbarkeit des erziehungswissenschaftlichen Publikationsaufkommens. Eine anwendungsorientierte Studie

Der Beitrag stellt Ziele und erste Ergebnisse des DFG-Projekts "Innovative bibliometrische Verfahren zur kontinuierlichen Beobachtung der sozialwissenschaftlichen Forschungsproduktion" vor. Eine Analyse des Publikationsverhaltens von Erziehungswissenschaftlern zeigt die große Bedeutung des Publikationstyps Sammelwerksbeitrag und der Publikationssprache Deutsch, aber auch eine ausgeprägte Heterogenität in der Publikationspraxis von erziehungswissenschaftlichen Institutionen. Skizziert wird schließlich der Vorschlag für einen neuen, dieser Publikationspraxis angemessenen, bibliometrischen Indikator. (DIPF/Autor

EPR Dating of Hydroxyapatite from Fossil Bones. Transient Effects after γ and UV Irradiation

ESR measurements at room temperature have been performed on fossil bones of cave bear (from Magurska Cave of the Tatra Mountains) and mammoth (from Dniestr River). Various paramagnetic centres related to defects in hydroxyapatite were identified. The ESR spectrum is dominated by Mn$\text{}^{2+}$ lines and free radical centres CO$\text{}_{2}^{-}$ and CO$\text{}_{3}^{-}$. Suitability of various EPR lines for the dating was evaluated. The spectra are affected by γ-ray and UV irradiation which produce new relatively unstable (transient) radical centres. From their decay curves we determined the delay period (waiting time) between irradiation and ESR dating measurements. For γ-rays the period is about 15 days and depends on the chosen ESR line. UV generates mainly surface O$\text{}^{-}$ centres which decay practically after a few days. The ESR dating of the bear bones using an additive dose method given the age t = 21.7 kiloyears (ky), whereas from radionuclide Th/U method t= 34 ky and from radiocarbon $\text{}^{14}$C method t > 33.1 ky

Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals

Cadmium pyroniobiate (CNO) is the ferroic material with unusual diffuse phase diagram which includes both relaxor and nanocluster domains. We present the data for CNO crystals with several admixtures of paramagnetic ions studied on X and S microwave bands at zero-external magnetic field and classical EPR conditions. Our results lead to an assertion of a ferroelectric resonance effect due to "electronic ferroelectricity". The data fit well to the Falicov-Kimball theoretical model applicable to strongly-correlated-electron or mixed-valence systems

Temperature Effects in ESR Spectra of Radical Centres in Dripstone Calcite Samples Used for ESR Dating

Natural calcite samples were collected from the dripstone layers of the Black Cave of the Tatra Mountains. ESR spectra, thermal analysis, and thermoluminescence data were analysed to obtain a consistent picture of the calcite properties. The ESR spectra were analysed using computer enhanced resolution spectra and an influence of the thermal annealing on intensity of individual ESR lines was measured. These results together with the effects of γ-irradiation in ESR spectra allowed one to discriminate between ESR lines from various paramagnetic centres. A general conclusion of the paper is that in the ESR dating the outer ESR lines of CO$\text{}_{3}^{-}$ (g=2.0125) and CO$\text{}_{2}^{-}$ (g=1.9980) radicals should be used instead of the commonly used multicomponent central line

Temperature Effects in ESR Spectra of Radical Centres in Dripstone Calcite Samples Used for ESR Dating

Natural calcite samples were collected from the dripstone layers of the Black Cave of the Tatra Mountains. ESR spectra, thermal analysis, and thermoluminescence data were analysed to obtain a consistent picture of the calcite properties. The ESR spectra were analysed using computer enhanced resolution spectra and an influence of the thermal annealing on intensity of individual ESR lines was measured. These results together with the effects of γ-irradiation in ESR spectra allowed one to discriminate between ESR lines from various paramagnetic centres. A general conclusion of the paper is that in the ESR dating the outer ESR lines of CO$\text{}_{3}^{-}$ (g=2.0125) and CO$\text{}_{2}^{-}$ (g=1.9980) radicals should be used instead of the commonly used multicomponent central line

Electrical resistivity of the u-Al4Mn giant-unit-cell complex metallic alloy

The mu-Al4Mn complex intermetallic phase with 563 atoms in its giant unit cell exhibits a complicated temperature dependence of electrical resistivity that has a broad maximum at about 175 K and a minimum at 13 K. The temperature dependence of the resistivity was reproduced by employing the theory of quantum transport of slow charge carriers, which predicts a crossover from the metallic (Boltzmann-type) positive-temperature-coefficient electrical resistivity at low temperatures to the insulator-like (non-Boltzmann) negative-temperature-coefficient resistivity at elevated temperatures. The low-temperature resistivity minimum was reproduced by considering it as a magnetic effect due to increased scattering of the conduction electrons by the Mn spins on approaching the spin glass phase that develops below the spin freezing temperature T-f = 2.7 K

Geometric origin of magnetic frustration in the µ-Al4Mn giant-unit-cell complex intermetallic

The structurally ordered μ-Al(4)Mn complex intermetallic phase with 563 atoms in the giant unit cell shows the typical broken-ergodicity phenomena of a magnetically frustrated spin system. The low-field zero-field-cooled and field-cooled magnetic susceptibilities show splitting below the spin freezing temperature T(f) = 2.7 K. The ac susceptibility exhibits a frequency-dependent cusp, associated with a frequency-dependent freezing temperature T(f)(ν). The decay of the thermoremnant magnetization is logarithmically slow in time and shows a dependence on the aging time t(w) and the cooling field H(fc) typical of an ultraslow out-of-equilibrium dynamics of a nonergodic spin system that approaches thermal equilibrium, but can never reach it on the experimentally accessible time scale. The above features classify the μ-Al(4)Mn complex intermettalic among spin glasses. The origin of frustration of magnetic interactions was found to be geometrical due to the distribution of a significant fraction of Mn spins on triangles with antiferromagnetic coupling. The μ-Al(4)Mn phase is a geometrically frustrated spin glass

The perfect soft mode:giant phonon instability in a ferroelectric

Previous studies of unstable ('soft') optical modes in ferroelectrics have reported minimum frequencies of 1 cm(-1) (30 GHz) for underdamped phonons. In this work we fabricate a cylindrical coaxial specimen and rectangular plate waveguide specimens of tris-sarcosine calcium chloride (TSCC) and follow its soft mode several orders of magnitude lower to 1 GHz. Below 30 GHz the relaxation time is probably characteristic of domain wall motion; the new theory of Pakhomov et al (2013 Ferroelectrics at press) predicts 0.5 THz far from T-C and a (T - T-C)/T-C dependence, in agreement with our experimental values. This discovery has implications for GHz electronics such as phased array radar or other voltage-tunable low-loss components. The mean-field frequency description of the soft mode response f(T) is supported via precision calorimetry on TSCC with and without Br-doping. The ferroelectric-antiferroelectric phase transition, previously suggested from high-pressure data, is confirmed at 45 K at 1 atm.</p