Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell

Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires’ layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm² under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%) . The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.     

Application of computer algebra-techniques to metabolic control analysis

For practical purposes the calculation of rate constants is not particularly valuable, since their physical significance is not clear. Of greater practical use are metabolic control coefficients and elasticities. Given the definition of the flux control coefficients C(E)(J), concentration control coefficient C(E)(X) and elasticity epsilon (X)(v(1)). We can calculate symbolic formulae for these using computer algebra-techniques. These are then functions of V(max), K(m), K(i) enzyme and concentrations. Having derived estimates of V(max), K(m), K(i) using the fitting method we can then calculate values of the control coefficients and elasticities. Furthermore we can calculate the metabolic control parameters using symbolic values for the conventional kinetic parameters. Using these we have verified the summation and connectivity theorems. This is a useful cross check on the reliability of the calculations.     

Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model

The nature (time variation) of response magnetization m(wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h(wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m(wt) and h(wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical (•), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results.     

Analysis of the effects of the global financial crisis on the Turkish economy, using hierarchical methods

We have analyzed the topology of 50 important Turkish companies for the period 2006-2010 using the concept of hierarchical methods (the minimal spanning tree (MST) and hierarchical tree (HT)). We investigated the statistical reliability of links between companies in the MST by using the bootstrap technique. We also used the average linkage cluster analysis (ALCA) technique to observe the cluster structures much better. The MST and HT are known as useful tools to perceive and detect global structure, taxonomy, and hierarchy in financial data. We obtained four clusters of companies according to their proximity. We also observed that the Banks and Holdings cluster always forms in the centre of the MSTs for the periods 2006-2007, 2008, and 2009-2010. The clusters match nicely with their common production activities or their strong interrelationship. The effects of the Automobile sector increased after the global financial crisis due to the temporary incentives provided by the Turkish government. We find that Turkish companies were not very affected by the global financial crisis.     

Radial orthogonality and Lebesgue constants on the disk

In polynomial interpolation, the choice of the polynomial basis and the location of the interpolation points play an important role numerically, even more so in the multivariate case. We explore the concept of spherical orthogonality for multivariate polynomials in more detail on the disk. We focus on two items: on the one hand the construction of a fully orthogonal cartesian basis for the space of multivariate polynomials starting from this sequence of spherical orthogonal polynomials, and on the other hand the connection between these orthogonal polynomials and the Lebesgue constant in multivariate polynomial interpolation on the disk. We point out the many links of the two topics under discussion with the existing literature. The new results are illustrated with an example of polynomial interpolation and approximation on the unit disk. The numerical example is also compared with the popular radial basis function interpolation.     

An experimental study on optimization of $${\mathbf{SiO}}_{2}$$ SiO 2 /water nanofluid flows in circular minichannels

Journal of Thermal Analysis and Calorimetry - An experimental research was performed to examine the effect of hydrodynamically and thermally developing distilled water-based SiO $$_2$$ nanofluid...     

Substitution kinetics of W(CO)5(η-bis(trimethylsilyl)ethyne) with triphenylbismuthine

The labile complex W(CO)₅(η²-btmse) undergoes replacement of bis(trimethylsilyl)ethyne, btmse, by triphenylbismuthine in cyclohexane solution at an observable rate in the temperature range of 35-50 °C yielding almost solely W(CO)₅(BiPh₃) as the final product. The kinetics of this substitution reaction was studied in cyclohexane solution by quantitative FT-IR spectroscopy. The substitution reaction obeys a pseudo-first-order kinetics with respect to the concentration of the starting complex. The observed rate constant, k_obs, was determined at four different temperatures and three different concentrations of the entering ligand BiPh₃ in the range 16.8-65.4 mM. From the evaluation of kinetic data a possible reaction mechanism was proposed in which the rate determining step is the cleavage of metal-alkyne bond in the complex W(CO)₅(η²-btmse). A rate law was derived from the proposed mechanism. From the dependence of k_obs on the entering ligand concentration, the rate constant k₁ for the rate determining step was estimated at all temperatures. The activation enthalpy (106 ± 2 kJ mol⁻¹) and the activation entropy (111 ± 6 J K⁻¹ mol⁻¹) were determined for this rate determining step from the evaluation of k₁ values at different temperatures. The large positive value of the activation entropy is consistent with the dissociative nature of reaction. The large value of the activation enthalpy, close to the calculated tungsten-alkyne bond dissociation energy, also supports this dissociative rate-determining step of the substitution reaction.     

N-methylpyrrolidine as an effective organocatalyst for the regioselective synthesis of 3-hydroxy-3,5/6-di-aryl-1H-imidazo[1,2-a]imidazol-2(3H)-ones

N-Methylpyrrolidine catalyzed, concise and attractive synthesis of a new class of 3-hydroxy-3,5/6-di-aryl-1H-imidazo[1,2-a]imidazol-2(3H)-ones was attained with impressive yields, in the presence of EtOH as a solvent, by means of a convenient and elegant condensation reaction between different aryl glyoxal monohydrates and guanidine hydrochloride under reflux conditions. Some specific merits of the current procedure, including encompasses low operating cost, availability of the starting substrates, reasonable reaction times, high reaction yield, operational simplicity, cleaner reaction profile, no harmful by-products, and the isolated product is in pure form. Structures of all the freshly synthesized products have been deduced by their FT-IR, ¹H-NMR, ¹³C-NMR, Mass spectrometry data and microanalysis.

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