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A sample of NaCr(P2O7) was synthesized using the solid-state reaction method. X-ray diffraction and Rietveld refinement confirmed the formation of a monoclinic structure with the P21/a space group. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis identified the morphology and homogeneity of the chemical composition. The optical absorption spectrum revealed a direct optical band gap of 2.9 eV and an Urbach energy of 0.44 eV. Notably, the absorption spectrum showed an interference dip on the lowest energy band 4T2g(4F), attributed to spin--orbit coupling between states ²Eg(²G) and 4T2g(4F). This phenomenon was analyzed using the Neuhauser model based on coupled potential energy surfaces. From this analysis, the electronic structure of Cr3+ (3d3) ions in the NaCr(P2O7) sample was determined, enabling a reliable calculation of Racah and crystal-field parameters. The results showed good agreement between experimental and theoretical energy levels. The study demonstrates the impact of spin--orbit interactions using the coupled potential energy surface model. [ABSTRACT FROM AUTHOR]

The spinels ZnAl1.99−xHoxCr0.01O4 (with x = 0 and 0.001) were synthesized using a solid-state method, and various techniques were employed for their characterization. X-ray diffraction (XRD) analysis confirmed a cubic spinel structure with the Fd3¯m space group for both spinels. The morphology and homogeneity of the chemical composition were determined using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. Raman and infrared vibrational spectroscopy techniques were also employed for analysis. The optical band gap (Eg) was determined from UV/vis absorption spectra, and the direct transition behavior was confirmed by Tauc's law. The observed large disorder and defect concentration are attributed to the presence of Cr3+ and Ho3+ ions, explaining this behavior. The electron paramagnetic resonance (EPR) measurement presented different types of traps. Room temperature absorption spectra exhibited multiple peaks corresponding to the 3d–3d and 4f–4f transitions of Cr3+ and Ho3+ ions. The results obtained validate the significance of our compounds in optoelectronic device applications. [ABSTRACT FROM AUTHOR]

ZnO nanowires are grown by metal organic chemical vapor deposition using two different zinc precursors, i.e., dimethylzinc-triethylamine which contains nitrogen, and diethylzinc which does not. The growth conditions are varied using different oxygen/zinc pressure ratios (RO/Zn). Temperature dependent Raman spectroscopy shows that the additional Raman modes are related to B1 modes which are activated because of translational symmetry breaking resulting from the nitrogen substitution on oxygen sites and/or Zn-O bond breaking caused by complex defects. Simultaneously, the antiparallel atomic displacements which are at the origin of B1 phonon vibrations are no more compensated, allowing B1 modes to acquire a polar character. The resulting polar phonons, and especially B1² located at 580 cm-1 (i.e., 72meV), are therefore believed to strongly couple to photogenerated electrons through a Fröhlich mechanism and could lead or contribute to the phonon-assisted replicas observed in the photoluminescence (PL) spectrum. Finally, we also discuss the possible defects involved in the Raman and PL responses including native donor and acceptor defects and their interaction with the N-dopant, depending on the growth conditions. [ABSTRACT FROM AUTHOR]

We have studied the photoluminescence emission line at 3.31 eV in ZnO nanowires. In undoped ZnO, this band strongly depends on high oxygen concentration and could originate from recombination of bound-exciton complex related to structural defects. Conversely, in doped ones, the photoluminescence emission appears notably at a low VI/II ratio and with the emergence of donoracceptor pair emission due to the presence of a-No nitrogen complex, which acts as a shallow acceptor in ZnO. We found that this band corresponds to 3LO, the third phonon replica of resonant Raman scattering. Furthermore, a remarkable variation is detected in a number of resonant Raman scattering multiphonons. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare co-contraction index (CCI) computed from muscle moments to different co-activation indexes (Co-Act) derived from EMG data at the ankle and the knee joint during gait. An EMG-driven model was used to estimate muscle moments during over-ground walking gait at a self-selected velocity from twelve healthy subjects. The CCI calculated from muscle moments was compared with three Co-Acts estimated from the normalized EMG data. The co-activation methods produced lower values than the CCI during the first double-support and the swing phase at the ankle joint and during the stance phase at the knee joint. The co-activation methods trend is to underestimate the simultaneous action of agonist and antagonist contraction. Because the EMG-driven model included the muscle mechanical properties (e.g. force-length-velocity relationship) and muscle moment-arm, the co-contraction based on major agonist and antagonist muscle moment may provide a more confident description of muscle action compared to co-activation indexes. [ABSTRACT FROM AUTHOR]

Wurtzite ZnO thin films were prepared on sapphire substrate by metal organic chemical vapor deposition (MOCVD). Raman scattering studies on different crystallographic textures were performed in the backscattering geometry, and polarization effect is investigated in different configurations [ABSTRACT FROM AUTHOR]

Abstract: In spite of antibiotic treatment, of progress of resuscitation and surgery, acute posterior mediastinitis remains associated to a high mortality. We report a case of man with posterior mediastinitis by perforing of the cervical oesophagus. While his state remained still with the classic treatment, the contribution of the hyperbaric oxygen therapy quickly improved his state. This therapeutics in addition in the usual treatment could improve the survival in this affection. [Copyright &y& Elsevier]