New graphical method for the iteration of one-dimensional maps

We present the “inverse-curve method” which (1) simplifies a graphical iteration of the logistic map by avoiding the use of the diagonal; (2) naturally demonstrates the first period-doubling bifurcation; and (3) allows one to read immediately the stable pair of the two-point cycle off from the graph of the recursive function. Cycles of order m 2 are reduced to graphs of k- and l-iterate functions with k + l = m. The method can easily be applied to other one-dimensional maps with more complicated recursion relations.     

Debye-temperatures and Mössbauer-shift in high-Tc superconductor: Ba2EuCu3O7±δ

The high T_C superconductor Ba₂EuCu_307±δ with measured T_c=94±2 K was investigated by Mössbauer spectroscopy. It is shown that the material at low temperatures has either a very high Debye temperature θ_D > 800 K, or it is crystallographically not single phased with one component (87%) with θ_D = 378±30 K and the other (13%) with θ_D = 136±13 K.     

Photo-induced tunneling spectroscopy of ReS2: Dramatic increase of the quantum efficiency by chemical treatment

In this work we present a systematic study of the local photovoltaic properties of ReS₂, using a scanning tunneling microscope (STM). The tunneling junction of the STM was optically illuminated during the tunneling process. The phase sensitive detected photo-induced tunneling current (PITC) was studied as a function of wavelength and surface topography. In order to improve the performance of ReS₂ solar cells, the samples were treated with NaI/I₂ and EDTA solutions. Relative to the untreated sample, the EDTA-treated samples show an increase in the photo-induced tunneling current by a factor of 8–10 in the whole spectral range, the NaI/I-treated samples by 2–3. Two dimensional mapping of the PITC was performed on an atomic scale and compared to the surface topography.     

Pulsed electrodeposition and magnetism of two-dimensional assembly of controlled-size Co particles on Si substrates

We present an extremely simple and inexpensive way to obtain controlled-size and density Co metallic particles on Si(1 1 1) using electrodeposition. When unpatterned substrates are used, the particle density and size can be controlled by adjusting the pulse frequency and the total deposition time. Randomly arranged cobalt particles with diameters of few tens of nanometres are obtained for short deposition times. Continuing the deposition, the particle size and density can be increased until coalescence. Magnetic force microscopy images show magnetically coupled/uncoupled particles depending on the size and distance between them. For small decoupled particles, no in-plane uniaxial anisotropy is found, in agreement with transmission electron microscopy observations which show randomly oriented single crystal particles. As the particle coalescence increases, the in-plane anisotropy evaluated from magnetization loops increases as well. When deposited on focused ion beam patterned substrates, well organized nanoparticles with adjustable magnetic anisotropy are obtained. Ferromagnetic resonance measurements performed on these samples reveal that the magnetic anisotropy originates mainly from the particle shape.     

Bose-einstein correlations of soft pions in ultrarelativistic nucleus-nucleus collisions

A detailed analysis of pair correlations of positive pions in the target fragmentation region is presented. Data on nuclear collisions at 200 GeV per nucleon were measured with the Plastic Ball in the WA80 experiment at the CERN SPS. The correlation functions are compared with analytical functions and with simulations incorporating Bose-Einstein symmetrization, final-state interactions and detector resolution. Source radii are shown to increase with increasing target size and with centrality. For central collisions the radii are larger than the geometrical sizes of the involved nuclei.     

Colloids for Catalysts: A Concept for the Preparation of Superior Catalysts of Industrial Relevance

Compared to conventional preparation methods for supported heterogeneous catalysts, the use of colloidal nanoparticles (NPs) allows for a precise control over size, size distribution, and distribution/location of the NPs on the support. However, common colloidal syntheses have restrictions that limit their applicability for industrial catalyst preparation. We present a simple, surfactant‐free, and scalable preparation method for colloidal NPs to overcome these restrictions. We demonstrate how precious‐metal NPs are prepared in alkaline methanol, how the particle size can be tuned, and how supported catalysts are obtained. The potential of these colloids in the preparation of improved catalysts is demonstrated by two examples from heterogeneous catalysis and electrocatalysis.