Results 1 - 10 of 130
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[en] Tape casting of BaFBr:Eu2+, an important storage phosphor material for X-ray detection was investigated. Rheological measurement, thickness evaluation and scanning electron microscopy were used to monitor the processes. Measurements of the physical imaging performance in terms of modulation transfer function, noise power spectrum and noise equivalent quanta were used to characterize the storage phosphor plates (SPPs). It was found that careful control of the processes, especially the optimization of the dispersants, resulted in superior SPPs with excellent packing structure and lowest structure noise. Measurements with a commercial Guinier Camera were also presented
[en] The relations of line peak intensity and width in IETS with the modulation parameter W = eVsub(s)/KT is presented to a great extent of W. The line quality factor Q (the ratio of line peak intensity to width) is introduced, as a paramenter for appraising line shape quality. In accordance with the relation of quality factor Q with W, the optimum measurement condition in IETS have been obtained. (orig.)
[en] We consider wetting phenomena in the vicinity of rough substrates. The quenched random geometry of the substrate is assumed to be a self-affine fractal with a roughness exponent of ζS. Asymptotic critical properties on approaching complete and critical wetting transitions are studied by combining the replica method with scaling and renormalization-group arguments. We find new critical behavior, controlled by a zero-temperature fixed point, when ζS exceeds the thermal roughness exponent of the emerging wetting layer. The possibility of an effective dimensional reduction due to randomness is considered. In two dimensions a number of exact results are obtained by using a many-body transfer-matrix technique
[en] The first-principles Hartree-Fock cluster method is applied to investigate the possible positions and associated hyperfine properties of the muonium centers in the II-VI semiconductor ZnO. Two clusters are used to simulate the local environments around the anti-bonding (AB)parallel and bond-center (BC)arallel muonium with axial symmetry along the c-axis, to try to understand the natures of the two centers whose axially symmetric hyperfine tensors have been observed experimentally. Our results show that the muonium center at the anti-bonding site close to oxygen (ABO)prallel is more stable and its charge state is +0.44, which indicates a donor state in the semiconductor, but the associated hyperfine parameters are only in reasonable order of magnitude agreement with the experiments. The results for the (BC)parallel center show a smaller binding energy than for the (ABO)parallel center, and hyperfine parameters three orders of magnitude larger than the experiment but still an order of magnitude smaller than for free muonium
[en] The defect formation energies and atomic geometries of interstitial hydrogen in its different charge states in a number of wide band gap oxides are calculated by the Heyd, Scuseria, Ernzerhof hybrid functional. As in semiconductors, two behaviours are found, it acts either as an amphoteric defect or as a shallow donor. There are large scale lattice relaxations between the different charge states for the case of the amphoteric defect. Interestingly, we find that the +/− transition level does have a good alignment below the vacuum level, as was found previously for tetrahedral semiconductors.
[en] External boundaries change the fluctuations of a correlated fluid, such as a liquid crystal, thereby causing long-range interactions. We compute how the interaction between two parallel plates is modified by the deformations of one plate. Corrections to the leading interaction decay with the average separation of the plates through an exponent related to the roughness of the boundary. These interactions may also modify the surface fluctuations of thin liquid films
[en] An immunodipstick assay with a lateral flow strip was developed for fast screening of food for aflatoxin B1 (AFB1) using the respective monoclonal antibody immobilized on nanoparticles with a silver core and a gold shell (AgAu) as detection reagent. The membrane-based immunodipstick consisted of a test line containing AFB1 conjugated to bovine serum albumin, and a control line with goat anti-mouse IgG. One to two colored lines are formed on the membrane by using the red AgAu nanoparticles coated with anti-AFB1 as signaling reagents. Under optimal conditions, the dipstick exhibits a lower visual detection limit of 0. 1 ng mL-1 of AFB1. Compared to the use of pure gold nanoparticles, the AgAu nanoparticles strongly enhance the sensitivity of the assay, and the reproducibility and stability are comparable. The assay was evaluated with naturally contaminated samples including rice, wheat, sunflower, cotton, chillies, and almonds, and a good correlation was found with data obtained with a commercially available enzyme-linked immunosorbent assay. The simple and non-instrumental dipstick method may further be extended to the screening of other mycotoxins in food. (author)
[en] Highlights: • A new method of synthesizing Co-N films containing Co_4N phase. • Tunable magnetic properties achieved in ECR plasma CVD. • The change of magnetic properties is related to atoms mobility on substrate and the concentration of active species in plasma vapor. - Abstract: By introducing DC negative-biased Co target in the Electron Cyclotron Resonance (ECR) nitrogen/argon plasma, the Co-N films containing Co_4N phase were synthesized on Si(100) substrate. Effects of processing parameters on magnetic properties of the films are investigated. It is found that magnetic properties of Co-N films vary with N_2/Ar flow ratio, substrate temperature, and target biasing voltage. The saturation magnetization M_s decreased by increasing the N_2/Ar gas flow ratio or decreasing target biasing voltage, while the coercive field H_c increased, which is ascribed to the variation of relative concentration for N or Co active species in plasma vapor. The magnetic properties present complex dependency with growth temperature, which is related to the atom mobility on the substrate affected by the growth temperature. This study exhibits a potential of ECR plasma chemical vapor deposition to synthesize the interstitial compounds and tune magnetic properties of films.
[en] Two oxidation peaks at 0.99, 1.48 V versus Fc/Fc"+ appear in the cyclic voltammograms of a series of defect-site functionalized SWNTs in methylene chloride solution in the presence of ferrocenes. These two peaks are demonstrated to be the electrochemical responses to the independent oxidation of v_1 and v_2 valence bands of þ-doped semiconducting SWNTs.