Facile post-synthesis and photocatalytic activity of N-doped ZnO–SBA-15

N-doped ZnO–SBA-15 materials (denoted as nN–xZnO–SBA-15, where n is number of urea treatments and x is the weight ratio of ZnO/(ZnO+SBA-15)) were successfully synthesized by a two-step procedure. First, xZnO–SBA-15 was prepared by impregnating SBA-15 with Zn(NO₃)₂, followed by calcinating at 550 °C. In the second step, xZnO–SBA-15 was modified n times by doping nitrogen with the assistance of urea. The resulting nN–xZnO–SBA-15 materials prepared with various numbers of urea treatments were characterized by XRD, TEM, SEM, EDS, N₂ adsorption/desorption at 77 K, diffuse reflectance UV–vis, and XPS. The results show that the nN–xZnO–SBA-15 maintains its ordered hexagonal mesostructure and exhibits light absorbance in the visible region. The nN–xZnO–SBA-15 samples were investigated with the photodegradation of methylene blue under visible light, and exhibited significant photocatalytic activity. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.     

Au@SiO2 core/shell nanoparticle assemblage used for highly sensitive SERS‐based determination of glucose and uric acid

The use of Au@SiO₂ core/shell nanoparticle (NP) assemblage with highly sensitive surface‐enhanced Raman scattering (SERS) was investigated for the determination of glucose and uric acid in this study. Rhodamine 6G dye molecules were used to evaluate the SERS enhancement factor for the synthesized Au@SiO₂ core/shell NPs with various silica shell thicknesses. The enhancement of SERS signal from Rhodamine 6G was found to increase with a decrease in the shell thickness. The core/shell assemblage with silica layer of 1–2 nm over a Au NP of ~36 nm showed the highest SERS signal. Our results show that the SERS technique is able to detect glucose and uric acid within wide concentration ranges, i.e. 20 ng/dL to 20 mg/dL (10⁻¹²–10⁻³ M) and 16.8 ng/dL to 2.9 mg/dL (10⁻¹¹–1.72 × 10⁻⁴ M), respectively, with associated lower detection limits of ~20 ng/dL (~1.0 × 10⁻¹² M) and ~16.8 ng/dL (~1.0 × 10⁻¹¹ M). Our work offers a low‐cost route to the fabrication of agile sensing devices applicable to the monitoring of disease progression. Copyright © 2013 John Wiley & Sons, Ltd.     

Theoretical study of electronic structure, chemical bonding, and X-ray absorption near edge spectroscopy in niobium and niobium monoxide

In this work, we calculate band structures, the density of state and chemical bonding of the metallic niobium (Nb) and its mono-oxide (NbO) crystals in their solid states using the Density Functional Theory and X-ray Absorption Near Edge Spectroscopy. The electronic properties of Nb and NbO are investigated using the Finite Difference Method. These theoretical results are found in good agreement with the most recent experimental data. Our calculations reveal that the NbO crystal behaves like a superconductor.     

𝒟-Stability Radius of Linear Discrete Time Systems

We study robustness of 𝒟-stability of linear difference equations under multiperturbation and affine perturbation of coefficient matrices via the concept of 𝒟-stability radius. Some explicit formulae are derived for these 𝒟-stability radii. The obtained results include the corresponding ones established earlier in Hinrichsen and Son and Ngoc and Son as particular cases.     

Regulation of expression of matrix metalloproteinase-9 by JNK in Raw 264.7 cells: presence of inhibitory factor(s) suppressing MMP-9 induction in serum and conditioned media

Matrix metalloproteinase-9 (MMP-9) secreted from macrophages plays an important role in tissue destruction and inflammation through degradation of matrix proteins and proteolytic activation of cytokines/chemokines. Whereas the MEK-ERK and PI3K-Akt pathways up-regulate MMP-9 expression, regulation of MMP-9 by JNK remains controversial. Presently, we aimed to determine the role of JNK in MMP-9 regulation in Raw 264.7 cells. Inhibition of JNK by the JNK inhibitor SP600125 induced MMP-9 in the absence of serum and suppressed the expression of TNF-α, IL-6 and cyclooxygenase-2 in LPS-treated Raw 264.7 cells. In a knockdown experiment with small interfering RNA, suppression of JNK1 induced MMP-9 expression. Interestingly, mouse serum suppressed SP600125-mediated MMP-9 induction, similar to IFN-γ. However, the inhibitory activity of mouse serum was not affected by pyridone 6, which inhibits Janus kinase downstream to IFN-γ. In addition to mouse serum, conditioned media of Raw 264.7 cells contained the inhibitory factor(s) larger than 10 kDa, which suppressed SP600125- or LPS-induced MMP-9 expression. Taken together, these data suggest that JNK1 suppresses MMP-9 expression in the absence of serum. In addition, the inhibitory factor(s) present in serum or secreted from macrophages may negatively control MMP-9 expression.     

Quantitative Assessment of Nanoparticle Single Crystallinity: Palladium‐Catalyzed Splitting of Polycrystalline Metal Oxide Nanoparticles

Crystal gazing : A simple Pd‐catalyzed site‐specific nanoetching method was developed to visualize the polycrystalline nature of Fe₃O₄ (see picture), Fe₂O₃, MnFe₂O₄, CoFe₂O₄, and MnO nanoparticle systems. The technique relies on the very fast etching speed of the grain interface within bi‐ or polycrystalline nanocrystals.

     

Potential antioxidant compounds in Mallotus species fingerprints. Part I: Indication, using linear multivariate calibration techniques

Some Mallotus species are used in traditional medicine in Vietnam and China. Some also show interesting activities, such as antioxidant and cytotoxic ones. Combining fingerprint technology with data-handling techniques allows indicating the peaks potentially responsible for given activities. In this study it is aspired to indicate from chromatographic fingerprints the peaks potentially responsible for the antioxidant activity of several Mallotus species. Relevant information was extracted using linear multivariate calibration techniques, both before and after alignment of the fingerprints with correlation optimized warping (COW). From the studied techniques, Stepwise Multiple Linear Regression is least recommended as it made an inadequate variable selection. Principal Component Regression theoretically can take largely varying variables uncorrelated to the antioxidant activity into account. However, in practice in the actual case study this problem was limited. These problems in principle do not occur using Partial Least Squares (PLS) models. Of the tested PLS methods, Orthogonal Projections to Latent Structures was preferred because of its simplicity, reproducibility, reduced model complexity and improved interpretability of the regression coefficients, yielding a clearer view on the individual contribution of the compounds. Furthermore, reducing analysis times from 60 min to 35 and 22.5 min resulted in the same main compounds, indicated responsible for the antioxidant activity. Models built after alignment by COW did not result in additional information.     

Novel water based cerium acetate precursor solution for the deposition of epitaxial cerium oxide films as HTSC buffers

A novel water based precursor solution using ethylenediaminetetraacetic acid (H₄EDTA) as a complexant and acetic acid and ethylenediamine (EDA) as additional components to obtain CeO₂ buffer layers on Ni (5%W) tapes is described in detail. The influence of complexation behavior in the formation of transparent and homogenous sols and gels by the combination of cerium acetate, acetic acid and H₄EDTA has been studied. The optimal growth conditions for cerium oxide were Ar-5% H₂ gas processing atmosphere, solution concentration levels of 0.2–0.4 M, a dwell time of 60 min at 900 °C and 5–30 min at 1,050 °C. X-ray diffraction, SEM, spectroscopic ellipsometry and pole figures were used to characterize the CeO₂ films. Highly textured CeO₂ layers were obtained.     

Portfolio selection under downside risk measures and cardinality constraints based on DC programming and DCA

In this paper, we consider the case of downside risk measures with cardinality and bounding constraints in portfolio selection. These constraints limit the amount of capital to be invested in each asset as well as the number of assets composing the portfolio. While the standard Markowitz’s model is a convex quadratic program, this new model is a NP-hard mixed integer quadratic program. Realizing the computational intractability for this class of problems, especially large-scale problems, we first reformulate it as a DC program with the help of exact penalty techniques in Difference of Convex functions (DC) programming and then solve it by DC Algorithms (DCA). To check globality of computed solutions, a global method combining the local algorithm DCA with a Branch-and-Bound algorithm is investigated. Numerical simulations show that DCA is an efficient and promising approach for the considered problem.      

DC programming and DCA for globally solving the value-at-risk

The value-at-risk is an important risk measure that has been used extensively in recent years in portfolio selection and in risk analysis. This problem, with its known bilevel linear program, is reformulated as a polyhedral DC program with the help of exact penalty techniques in DC programming and solved by DCA. To check globality of computed solutions, a global method combining the local algorithm DCA with a well adapted branch-and-bound algorithm is investigated. An illustrative example and numerical simulations are reported, which show the robustness, the globality and the efficiency of DCA.