MACRO- AND MICRO ELEMENT LEVELS IN CEREALS GROWN IN LOWER AUSTRIA

In order to study the effects of soil type and site conditions upon essential element levels in cereals, a pilot study of field and pot experiments were carried out on a Dystric cambisol, a Gleyic luvisol, a Calcareous phaeozem, and a Calcareous chernozem in 3 subsequent years. Based on the results of multiemelent analyses, it was evident that P and Zn were found mainly in the grains, and Ca, Fe, and Mn preferably in the straw. Concentrations in the grains were kept rather constant for Fe, Mn, S, and P, whereas the straw acted as a buffer to store excess mobile amounts. Apart from some differences due to cereal species and cultivars, additional supply of nutrient element fertilizer solution and shorter root length led to higher Cu, Fe, Mn, and Zn in cereals grown in pots, and a shift in the grain/straw ratios for Ca. Thus, the results obtained in pot experiments cannot be directly transferred to fi eld conditions. From at least 5 replicates of each setup, on the average, precision of analytical data obtained for whole grain samples was better than for straw samples, and precision obtained in pot experiments was less than those in fi eld experiments. In pot experiments, increase of the number of replicates from 5 to 10 or 20 did not improve analytical precision

Anharmonicity due to Electron-Phonon Coupling in Magnetite

We present the results of inelastic x-ray scattering for magnetite and analyze the energies and spectral widths of the phonon modes with different symmetries in a broad range of temperature 125<T<293 K. The phonon modes with X_4 and Delta_5 symmetries broaden in a nonlinear way with decreasing temperature when the Verwey transition is approached. It is found that the maxima of phonon widths occur away from high-symmetry points which indicates the incommensurate character of critical fluctuations. Strong phonon anharmonicity induced by electron-phonon coupling is discovered within ab initio calculations which take into account local Coulomb interactions at Fe ions. It (i) explains observed anomalous phonon broadening, and (ii) demonstrates that the Verwey transition is a cooperative phenomenon which involves a wide spectrum of phonons coupled to charge fluctuations condensing in the low-symmetry phase.Comment: 5 pages, 5 figures, accepted in Physical Review Letter

Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1TT-TiSe2_2

Using time- and angle-resolved photoemission spectroscopy with selective near- and mid-infrared photon excitations, we investigate the femtosecond dynamics of the charge density wave (CDW) phase in 1$T$-TiSe$_2$, as well as the dynamics of CDW fluctuations at 240 K. In the CDW phase, we observe the coherent oscillation of the CDW amplitude mode. At 240 K, we single out an ultrafast component in the recovery of the CDW correlations, which we explain as the manifestation of electron-hole correlations. Our momentum-resolved study of femtosecond electron dynamics supports a mechanism for the CDW phase resulting from the cooperation between the interband Coulomb interaction, the mechanism of excitonic insulator phase formation, and electron-phonon coupling.Comment: 9 pages, 6 figure

Short-Range Correlations in Magnetite above the Verwey Temperature

Magnetite, Fe$_3$O$_4$, is the first magnetic material discovered and utilized by mankind in Ancient Greece, yet it still attracts attention due to its puzzling properties. This is largely due to the quest for a full and coherent understanding of the Verwey transition that occurs at $T_V=124$ K and is associated with a drop of electric conductivity and a complex structural phase transition. A recent detailed analysis of the structure, based on single crystal diffraction, suggests that the electron localization pattern contains linear three-Fe-site units, the so-called trimerons. Here we show that whatever the electron localization pattern is, it partially survives up to room temperature as short-range correlations in the high-temperature cubic phase, easily discernible by diffuse scattering. Additionally, {\it ab initio} electronic structure calculations reveal that characteristic features in these diffuse scattering patterns can be correlated with the Fermi surface topology.Comment: 7 pages, 6 figure