Primary pulse transmission in coupled steel granular chains embedded in PDMS matrix: Experiment and modeling

We present an experimental study of primary pulse transmission in coupled ordered steel granular chains embedded in poly-di-methyl-siloxane (PDMS) elastic matrix. Two granular one-dimensional chains are considered (an ‘excited’ and an ‘absorbing’ one), each composed of 11 identical steel beads of 9.5 mm diameter with the centerline of the chain spaced at fixed distances of 0.5, 1.5 or 2.5 mm apart. We directly force one of the chains (the excited one) by a transient pulse and measure, by means of laser vibrometry, the primary transmitted pulses at the end beads of both chains and at the first bead of the absorbing chain. It is well known that the dynamics of this type of ordered granular media is strongly nonlinear due, (i) to Hertzian interactions between adjacent beads, and (ii) to possible bead separations in the absence of compressive forces and ensuing collisions between neighboring beads. Accordingly, we develop a strongly nonlinear theoretical model that takes into account the coupling of the granular chains due to the PDMS matrix, with the aim to model primary pulse transmission in this system. After validating the model with experimental measurements, we employ it in a predictive fashion to estimate energy transfer between chains as a function of the interspatial distance between chains. Furthermore, based on this model we perform predictive matrix design to achieve maximum energy transfer from the excited to the absorbing chain, and provide a theoretical explanation of the nonlinear dynamics governing energy transfer (including energy equi-partition) in this system.     

Electrochemical synthesis of a thiophene-containing cyclo[9]pyrrole

A new member of the cyclo[n]pyrrole class of expanded porphyrins could be prepared from the corresponding thiophene-containing terpyrrole precursor through use of a mild electrochemical oxidative procedure. The isolated macrocycle, featuring nine heterocyclic subunits directly connected through their α,α'-positions, is the largest cyclo[n]pyrrole derivative reported to date (see figure).     

Local immune cell contributions to fracture healing in aged individuals – A novel role for interleukin 22

With increasing age, the risk of bone fractures increases while regenerative capacity decreases. This variation in healing potential appears to be linked to adaptive immunity, but the underlying mechanism is still unknown. This study sheds light on immunoaging/inflammaging, which impacts regenerative processes in aging individuals. In an aged preclinical model system, different levels of immunoaging were analyzed to identify key factors that connect immunoaged/inflammaged conditions with bone formation after long bone fracture. Immunological facets, progenitor cells, the microbiome, and confounders were monitored locally at the injury site and systemically in relation to healing outcomes in 12-month-old mice with distinct individual levels of immunoaging. Bone tissue formation during healing was delayed in the immunoaged group and could be associated with significant changes in cytokine levels. A prolonged and amplified pro-inflammatory reaction was caused by upregulated immune cell activation markers, increased chemokine receptor availability and a lack of inhibitory signaling. In immunoaged mice, interleukin-22 was identified as a core cell signaling protein that played a central role in delayed healing. Therapeutic neutralization of IL-22 reversed this specific immunoaging-related disturbed healing. Immunoaging was found to be an influencing factor of decreased regenerative capacity in aged individuals. Furthermore, a novel therapeutic strategy of neutralizing IL-22 may successfully rejuvenate healing in individuals with advanced immune experiences.Subject terms: Trauma, Mechanisms of disease, Interleukins, Osteoimmunology     

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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.