X‐ray absorption study of the local structure at the NiO/oxide interfaces

This work reports an X‐ray absorption near‐edge structure (XANES) spectroscopy study at the Ni K‐edge in the early stages of growth of NiO on non‐ordered SiO₂, Al₂O₃ and MgO thin films substrates. Two different coverages of NiO on the substrates have been studied. The analysis of the XANES region shows that for high coverages (80 Eq‐ML) the spectra are similar to that of bulk NiO, being identical for all substrates. In contrast, for low coverages (1 Eq‐ML) the spectra differ from that of large coverages indicating that the local order around Ni is limited to the first two coordination shells. In addition, the results also suggest the formation of cross‐linking bonds Ni—O—M (M = Si, Al, Mg) at the interface.     

An isothermal titration calorimetry study of the interactions between an oxyphenylethylene/oxyethylene diblock copolymer and sodium dodecyl sulfate

Interactions between the diblock copolymer S₁₅E₆₃ and the surfactant sodium dodecyl sulfate (SDS) have been investigated by isothermal titration calorimetry (ITC) in the temperature range 10–40°C. At 20°C, the block copolymer is associated into micelles with a hydrodynamic radius of 11.6?nm, which is composed of a hydrophobic styrene oxide (S) core and a water-swollen oxypolyethylene (PEO) corona. The copolymer/surfactant system has been studied at a constant copolymer concentration of 0.25?wt% and over a wide range of surfactant concentration, from 7.5?×?10^?6 up to 0.3?M. The titration calorimetric data for SDS in the temperature range 10–20°C presents a first endothermic increase indicating the formation of mixed copolymer rich-surfactant micelles. From that point, important differences in the ITC plots for surfactant titrations in the presence and in the absence of the copolymer are present. A shallow second endothermic peak is assigned to the interaction between SDS molecules and copolymer molecules resulting from the beginning of micelle disruption. An exothermic peak indicates the end of this disruption where only SDS micelles attached to single copolymer monomers are present, as shown by DLS in a previous paper. At higher temperatures in the range 25–40°C, the first endothermic maximum is not totally shown because interactions between surfactant and block copolymer start at very low SDS concentrations. Moreover, the second endothermic peak is absent and the exothermic minimum is less pronounced as a consequence of the increased micellization of the block copolymer.     

Measurement of charged-particle multiplicities in gluon and quark jets in pp collisions at square root of s = 1.8 TeV

We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, Nq and Ng, produced at the Fermilab Tevatron in pp collisions with a center-of-mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies of 41 and 53 GeV by counting charged particle tracks in cones with opening angles of theta(c) = 0.28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q = Ejet theta c varies in the range from 12 to 25 GeV. At Q = 19.2 GeV, the ratio of multiplicities r = Ng/Nq is found to be 1.64+/-0.17, where statistical and systematic uncertainties are added in quadrature. The results are in agreement with resummed perturbative QCD calculations.     

Defect identification in rods subject to forced vibrations using the spatial wavelet transform

Use of the wavelet transform (WT) to study the forced vibrations in a rod in order to detect the presence of a defect is proposed. The axial vibrations in an inhomogeneous rod, produced by the application of different forces, are simulated by the Network Simulation Method and the obtained response is analyzed with the WT. An analysis of the detection and location of defects for several applied forces and defects generated by locally changing density or stiffness of the rod is presented. A noise test was carried out to check the robustness of the technique in real situations.     

Interaction effects in single layer and multi-layer graphene

We discuss the excitation spectrum, electronic susceptibilities, and possible electronic instabilities in graphene and graphene stacks. The corrections due interactions of Landau levels in graphene are analyzed. At low dopings, and for sufficiently low couplings, single layer graphene is stable against ferromagnetism. On the other hand, a graphene bilayer, and infinite graphite, are unstable towards ferromagnetism and antiferromagnetism.     

Neural stem cells express melatonin receptors and neurotrophic factors: colocalization of the MT<Subscript>1</Subscript>receptor with neuronal and glial markers

Background  

In order to optimize the potential benefits of neural stem cell (NSC) transplantation for the treatment of neurodegenerative disorders, it is necessary to understand their biological characteristics. Although neurotrophin transduction strategies are promising, alternative approaches such as the modulation of intrinsic neurotrophin expression by NSCs, could also be beneficial. Therefore, utilizing the C17.2 neural stem cell line, we have examined the expression of selected neurotrophic factors under different in vitro conditions. In view of recent evidence suggesting a role for the pineal hormone melatonin in vertebrate development, it was also of interest to determine whether its G protein-coupled MT₁ and MT₂ receptors are expressed in NSCs.     

Cross sections and transverse single-spin asymmetries in forward neutral-pion production from proton collisions at sqrt[s]=200 GeV

Measurements of the production of forward high-energy pi(0) mesons from transversely polarized proton collisions at sqrt[s]=200 GeV are reported. The cross section is generally consistent with next-to-leading order perturbative QCD calculations. The analyzing power is small at x(F) below about 0.3, and becomes positive and large at higher x(F), similar to the trend in data at sqrt[s]< or =20 GeV. The analyzing power is in qualitative agreement with perturbative QCD model expectations. This is the first significant spin result seen for particles produced with p(T)>1 GeV/c at a polarized proton collider.     

Application of trilinear SLICING to analyse a single relaxation curve

Determining the time constants and amplitudes of exponential decays from relaxation data is a common task in LF-NMR. In this communication, we present an application of the SLICING algorithm to evaluate its possibilities for solving this problem. The method, originally introduced to compare different samples, is applied here to analyse a single relaxation curve, using the embedding technique. To test this procedure, we acquired data sets from samples of liquids properly separated, and characterized by different relaxation times. The results show a good estimation of parameters, comparable with those obtained applying Marquardt's algorithm, when the components have sufficiently different relaxation times.