Optical characteristics of Tb-doped InBO3 nanocrystals

InBO₃ nanocrystals doped with Tb³⁺ ions are prepared via the sol–gel method. The structure, morphology, and optical properties of the nanocrystals are characterized by X-ray diffraction, high-resolution transmission electron microscopy, field-emission scanning electron microscopy, and photoluminescence analysis. The results show that a hexagonal InBO₃ phase forms at above 650 °C. A second phase of In₂O₃ begins to appear with Tb doping of over 3 mol%. The ⁵D₄→⁷F₅ (553 nm) transitions of Tb³⁺ ions in the InBO₃ host are observed at 2 mol%. The decay time of Tb-doped InBO₃ nanocrystals is about 2.1 ms. For Tb-doped InBO₃ nanocrystals excited at 237 nm and 553 nm wavelengths, the 2 mol% doping level yields the highest saturation of green emission. The emission shifts from green to yellow when the doping concentration is increased from 1 to6 mol%, due to the ⁵D₄→⁷F₅ transition.     

Preparation and luminescent characteristic of Li3NbO4 nanophosphor

Synthesis and luminescence properties of Li₃NbO₄ oxides by the sol-gel process were investigated. The products were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and absorption spectra. The PL spectra excited at 247 nm have a broad and strong blue emission band maximum at 376 nm, corresponding to the self-activated luminescence of the niobate octahedra group [NbO₆]⁷⁻. The optical absorption spectra of the samples sintered at temperatures of 600 and 700 °C exhibited the band-gap energies of 4.0 and 4.08 eV.     

The Linearized Calderón Problem on Complex Manifolds

In this note we show that on any compact subdomain of a Kähler manifold that admits sufficiently many global holomorphic functions, the products of harmonic functions form a complete set. This gives a positive answer to the linearized anisotropic Calderón problem on a class of complex manifolds that includes compact subdomains of Stein manifolds and sufficiently small subdomains of Kähler manifolds. Some of these manifolds do not admit limiting Carleman weights, and thus cannot be treated by standard methods for the Calderón problem in higher dimensions. The argument is based on constructing Morse holomorphic functions with approximately prescribed critical points. This extends earlier results from the case of Riemann surfaces to higher dimensional complex manifolds.     

Some existence results for solutions of generalized vector quasi-equilibrium problems

In this paper, we consider more general forms of generalized vector quasi-equilibrium problems for multivalued maps which include many known vector quasi-equilibrium problems and generalized vector quasi-variational inequality problems as special cases. We establish some existence results for solutions of these problems under pseudomonotonicity and u-hemicontinuity/ℓ-hemicontinuity assumptions.      

Biochemical Characterization of Two Truncated Forms of Amylopullulanase from Thermoanaerobacterium saccharolyticum NTOU1 to Identify Its Enzymatically Active Region

The enzymatically active region of amylopullulanase from Thermoanaerobacterium saccharolyticum NTOU1 (TsaNTOU1Apu) was identified by truncation mutagenesis. Two truncated TsaNTOU1Apu enzymes, TsaNTOU1ApuM957 and TsaNTOU1ApuK885, were selected and characterized. Both TsaNTOU1ApuM957 and TsaNTOU1ApuK885 showed similar specific activities toward various substrates. The overall catalytic efficiency (k (cat)/apparent K (m)) for the soluble starch or pullulan substrate, however, was 20-25% lower in TsaNTOU1ApuK885 than in TsaNTOU1ApuM957. Both truncated enzymes exhibited similar thermostability and substrate-binding ability against the raw starch. The fluorescence and circular dichroism spectrometry studies indicated that TsaNTOU1ApuK885 retained an active folding conformation similar to that of TsaNTOU1ApuM957. These results indicate that a large part of the TsaNTOU1Apu, such as the C-terminal carbohydrate-binding module family 20, the second fibronectin type III, and a portion of the first FnIII motifs, could be removed without causing a serious aberrant structural change or a dramatic decrease in hydrolysis of soluble starch and pullulan.     

Effects of fiber physical and chemical characteristics on the interaction between endoglucanase and eucalypt fibers

Roles played by fiber physical and chemical characteristics in enzymatic hydrolysis of cellulosic materials were investigated by analyzing the interaction between an endoglucanase complex and eucalypt kraft fibers. PFI refining was employed to create the difference of fiber size distribution and morphology. Oxygen delignification and bleaching were employed to prepare fibers with different lignin and pentosan contents. The enzyme accessibility was monitored by adsorption at 4 °C and during hydrolysis at 40 °C. Molecular weight changes and reducing sugar released were monitored for digestibility of the samples. Greater maximum adsorption capacities of the enzymes were shown for the pulps with shorter and wider fibers and more fine fractions after refining. Highest amount of enzyme was adsorbed onto fibers with the least lignin contents at 4 °C. Fewer desorbed from fibers with higher lignin contents during hydrolysis at 40 °C. For unrefined fibers, less molecular weight reductions were observed for fibers with higher lignin contents. However, extensive fibrillation by refining negated the effects of lignin on the action of endoglucanase, similar molecular weight reductions were observed for fibers with three different lignin contents. Refining could be able to expose more reaction sites on the fiber surface, hence the impacts of lignin and pentosan diminished during hydrolysis for refined fibers.     

A fourth‐order compact finite difference scheme for solving an N‐carrier system with Neumann boundary conditions

In this study, we develop a fourth‐order compact finite difference scheme for solving a model of energy exchanges in a generalized N‐carrier system with heat sources and Neumann boundary conditions, which extends the concept of the well‐known parabolic two‐step model for microheat transfer. By using the matrix analysis, the compact finite difference numerical scheme is shown to be unconditionally stable. The accuracy of the solution obtained by the scheme is tested by a numerical example. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010     

The crack resistance of a dilatation-sensitive material

The entire history of crack propagation in high-strength steel with dilatation-sensitivity is investigated in this work. Based on the experimentally determined stress-strain curves varying in the strain history according to the mean stress level, a central cracked panel made of unaged maraging steel subject to a remote tension is considered in the analysis. Due to tremendous amount of hydrostatic stress established in the vicinity of the crack tip, the effect of mean stress is accounted for in the onset for plastic flow. The J₂−I₁ non-associate flow rule is incorporated in the incremental analysis employing the isoparametric finite element method with displacement formulation. When the stage of global instability is approached, the possible formation of a secondary crack in front of the primary crack is demonstrated by the use of strain energy density criterion. Also, the size effect on the crack resistance curve is established at the end for the unaged maraging steel.     

A Study of Degradation of a Jet Fuel

Degradation of a jet fuel (JP-5) derived from petroleum and manufactured by the Chinese Petroleum Corporation in Taiwan was determined using various methods. Fuel degradation was monitored in the presence of the following compounds: phenol, 2,6-dimethylphenol, thiophenol, 2-methylpyridine, copper powder and mixtures of some of these compounds both at room temperature and at 80°C. The extent of light scattering and the amount of copper drawn into JP-5 from added copper powder are correlated with the extent of deposit formation due to degradation of the fuel. Copper promotes deterioration of JP-5 because of Cu(II) complex formation. Electron spin resonance and cyclic voltammetric measurements confirm the presence of Cu(II).     

Crack-extension resistance of polycarbonate material

Crack-extension resistance for the polycarbonate material is examined by application of the strain energy density criterion and the incremental theory of plasticity. The energy state ahead of a slow moving crack in a three-point bend specimen is obtained for each load increment and used to determine the crack growth characteristics. The analytical results are displayed by plotting the strain energy density factor S as a function of crack length and compared with available experimental data on the polycarbonate material. Standard deviations and mean errors are computed for the experimentally measured and analytically determined values of S and are shown to be much lower than those based on the J-integral parameter. Modeling of the polycarbonate material by the theory of plasticity still remains much to be desired. Crack growth calculations are performed for a strain hardening parameter α = 0.85 that controls the proportion of isotropic and kinematic hardening. Nevertheless, the criterion dS/da = const. is shown to collate well with the experimental crack growth data.