Synthesis and optical spectroscopy of ZnO nanowires

Single crystal ZnO nanowires with lengths and diameters ranging from 2 to 30 μm and 100 to 300 nm, respectively, have been grown by the vapor transport method on SiO₂/Si substrates using Au as catalyst. Their Raman and emission properties under different excitation wavelengths have been studied at the nanoscale. Whereas Raman measurements on nanowires corroborate the well-known ZnO phonon characteristics, their photoluminescence spectra exhibit a very broad emission band, mainly in the visible region from 450 to 800 nm, which corresponds to different defect-related recombination processes. Spectrally resolved scanning near-field optical microscopy, SNOM, of single ZnO nanowires have also been performed for a direct imaging of the photoluminescence emission with high spatial resolution below 100 nm, establishing a relationship with the simultaneously acquired topography.     

Comparison of various statistical methods for detecting disease outbreaks

In this article, we compared seven statistical methods for detecting outbreaks of infectious disease; Historical limits, English model, SPOTv2, CuSums, Bayesian predictive model, RKI method and Serfling model. We used simulated data and real data to compare those seven methods. Simulated data have parameters such as trend, seasonality, mean and standard deviation. Among these methods, SPOTv2 shows the best performance with a balance between sensitivity and positive predictive value and short time lag. But in datasets having strong trends, Bayesian predictive model, English model and Serfling model perform better than SPOTv2. These methods are also compared through real numerical example.     

Fabrication, assembly and tests of a MEMS-based safe, arm and fire device

We propose a safe, arm and fire (SAF) device that could constitute a real breakthrough for safe miniature fuzing device. It integrates all the functions of a conventional mechanical arm and fire system and integrates them within 1 cm³. For the first time, it combines a mechanical arming unit with electrical safety functionalities on the same silicon initiator's chip. It requires only 635 mW for ignition.     

Selective Oxidation of Cyclic Hydrocarbons with H2O2 over Ti- and V-Containing Zeolites and Mesoporous Catalysts

Ti- and V-containing MFI, MEL and MCM-41 catalysts were studied in the oxidation of cyclohexane, cyclohexene, naphthalene, tetralin, decalin and phenol with H₂O₂. Although TS-1 and TS-2 exhibited the highest activity and selectivity in the oxidation of _n -hexane and 1-hexene, cyclohexene could only be oxidized effectively on the MCM-41 silicates. Since the oxidation of condensed aromatic systems over Ti- and V-containing MFI and MEL zeolites runs to difficulties, MCM-41 type catalysts may be offered for these reactions.     

Palladium-catalyzed regioselective introduction of chalcogen moieties into porphyrin bearing an ethynyl group

In the field of materials science, π-conjugated molecules bearing a group 16 heteroatom are of great importance. Sulfur or selenium containing porphyrins were successfully synthesized using the transition-metal-catalyzed reaction with diphenyl dichalcogenides. NMR studies indicated the preferential formation of the (Z)-isomer.     

Novel polymerizable bent-shaped monomeric molecules

Novel bent-shaped mesogens based on substituted naphthalene-2,7-diol, possessing a double bond at the end of terminal branches, have been synthesized and characterized. A variety of banana-mesophases has been found, depending on the type of lateral substitution. Increasing the length of the alkyl chain leads to the appearance of the SmC_AP_A phase for two of the compounds synthesized. Under an electric field a transition into the SmC_SP_F phase takes place and a tilt angle close to 45° has been found. These materials are appropriate for the preparation of polymeric materials.     

A globally convergent inexact Newton method with a new choice for the forcing term

In inexact Newton methods for solving nonlinear systems of equations, an approximation to the step s _k of the Newton’s system J(x _k )s=−F(x _k ) is found. This means that s _k must satisfy a condition like ‖F(x _k )+J(x _k )s _k ‖≤η _k ‖F(x _k )‖ for a forcing term η _k ∈[0,1). Possible choices for η _k have already been presented. In this work, a new choice for η _k is proposed. The method is globalized using a robust backtracking strategy proposed by Birgin et al. (Numerical Algorithms 32:249–260, 2003), and its convergence properties are proved. Several numerical experiments with boundary value problems are presented. The numerical performance of the proposed algorithm is analyzed by the performance profile tool proposed by Dolan and Moré (Mathematical Programming Series A 91:201–213, 2002). The results obtained show a competitive inexact Newton method for solving academic and applied problems in several areas. Supported by FAPESP, CNPq, PRONEX-Optimization.     

Chronopotentiometric method for the assessment of ionophore diffusion coefficients in solvent polymeric membranes

A chronopotentiometric method is proposed for the determination of the diffusion coefficients of free ionophores in solvent polymeric membranes. For the pH sensitive chromoionophore ETH 5294, the method was shown to give diffusion coefficients that correlate well with those assessed by both optical and chronoamperometric methods. The limit of applicability of the chronoamperometric and chronopotentiometric methods in terms of membrane composition and experimental parameters has been identified. The chronopotentiometric method was successfully used to determine the diffusion coefficients of eight ionophores and proved to be more robust and more widely applicable than the previously reported chronoamperometric and optical methods. An erratum to this article can be found at     

Dislocation of the <Superscript>137</Superscript>Cs and <Superscript>40</Superscript>K radionuclides in the podsol profiles of the Tatra Mountain soils (South Poland)

Summary The amount and dislocation of the gamma-radionuclides (artificial cesium and natural potassium) in the Haplic podsol profiles of the Tatra Mountains have been described. These soils belong to the group of penetrable formations what is a result of their texture. They provide a good example of percolation and sorption possibilities of the radionuclides within the soil profile. The highest concentration of radionuclides has been detected in raw humus and spodic (illuvial humus-iron) layers, at the surface.