Syntheses and characterization of different zinc(II) oxide nano-structures from direct thermal decomposition of 1D coordination polymers

Three zinc(II) nitrite coordination polymers, [Zn(4-bpdb)(NO₂)₂]_n (1), {[Zn(3-bpdb)(NO₂)]·0.5H₂O}_n (2) and [Zn(3-bpdh)(NO₂)₂]_n (3), 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene and 3-bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene} were prepared and characterized by elemental analyses and IR spectroscopy. Compound 3 was structurally characterized by single-crystal X-ray diffraction and is one-dimensional polymer with coordination environments of distorted octahedral, ZnN₂O₄. The thermal stabilities of compounds 1–3 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Direct calcination of the compounds 1–3 at 600 °C under air atmospheres yields different morphologies of nano-sized ZnO.     

Variability in the Formation and Framework Polymorphism of Metal-organic Frameworks based on Yttrium(III) and the Bifunctional Organic Linker 2,5-Dihydroxyterephthalic Acid

Depending on the solvothermal reaction conditions, we obtained three different metal-organic frameworks with yttrium(III) as metal component and 2,5-dihdyroxyterepthalic acid (H₄dhtp) as bifunctional organic linker: Y₂(H₂dhtp)₃(dmf)₄ · (dmf)₂ (CPO-29) contains dinuclear, paddle-wheel like inorganic secondary building units (SBUs) connected by the organic linker to a network with α-Po topology, while Y₂(H₂dhtp)(dhtp)(dmf)₂ (CPO-30) and Y₂(H₂dhtp)(dhtp)(dmf)₂(H₂O)₂ · (H₂O)₄ (CPO-31) contain one-dimensional inorganic SBUs that differ in how the half- and fully deprotonated ligands are connected to and arranged around them. Only the carboxylic acid groups of the organic linker are deprotonated in CPO-29, while CPO-30 and CPO-31 contain both 2,5-dihydroxyterephthalate (H₂dhtp^2–) linkers and fully deprotonated 2,5-dioxidoterephthalate (dhtp^4–) linkers. All three compounds contain large volumes filled with solvent, but we were able to demonstrate permanence of porosity only for CPO-30. Variable temperature powder X-ray diffraction reveals that CPO-29 and CPO-31 undergo discontinuous phase transitions upon heating, and the flexibility of the framework structure indicated by these might be the reason for the inability to access the pore volume. Desolvated CPO-30 and CPO-31 are polymorphs, whose network structures differ in whether the H₂dhtp^2– and dhtp^4– linkers are located in cis or trans arrangement around the inorganic SBU.     

Development of superconducting power devices in Europe

Europe celebrated last year (2008) the 100-year anniversary of the first liquefaction of helium by H. Kammerling Onnes in Leiden. It led to the discovery of superconductivity in 1911. Europe is still active in the development of superconducting (SC) devices. The discovery of high critical temperature materials in 1986, again in Europe, has opened a lot of opportunities for SC devices by broking the 4 K cryogenic bottleneck.     

Shallow Water equations for Non-Newtonian fluids

The purpose of this paper is to provide a consistent thin layer theory for some Non-Newtonian fluids that are incompressible and flowing down an inclined plane under the effect of gravity. We shall provide a better understanding of the derivation of Shallow Water models in the case of power-law fluids and Bingham fluids. The method is based on asymptotic expansions of solutions of the Cauchy Momentum equations in the Shallow Water scaling and in the neighbourhood of steady solutions so that we can close the average equations on the fluid height h and the total discharge rate q. Such a method has been first introduced in the case of Newtonian fluids where the computations are proved to be rigorous (Vila, in preparation [20]; Bresch and Noble, 2007 [9]) whereas the more complex case of arbitrary topography has been treated formally (Boutounet et al., 2008 [5]). The well posedness of the free surface Cauchy Momentum equations for these Non-Newtonian fluids is still an open problem: the computations carried out here are only formal.     

A random telegraph signal of Mittag-Leffler type

A general method is presented to explicitly compute autocovariance functions for non-Poisson dichotomous noise based on renewal theory. The method is specialized to a random telegraph signal of Mittag-Leffler type. Analytical predictions are compared to Monte Carlo simulations. Non-Poisson dichotomous noise is non-stationary and standard spectral methods fail to describe it properly as they assume stationarity.     

High yielding microwave-assisted synthesis of tri-substituted 1,3,5-triazines using Pd-catalyzed aryl and heteroarylamination

A rapid and efficient Pd-catalyzed aryl and heteroarylamination under microwave irradiation has been developed for various tri-substituted triazines that can serve as versatile building blocks for both supramolecular and medicinal chemistry research. Particularly valuable features of this method included the short reaction time, good yield, and convenient operation.     

Sulfide determination in hydrothermal seawater samples using a vibrating gold micro-wire electrode in conjunction with stripping chronopotentiometry

A rapid electrochemical stripping chronopotentiometric procedure to determined sulfide in unaltered hydrothermal seawater samples is presented. Sulfide is deposited at −0.25 V (vs Ag/AgCl, KCl 3 M) at a vibrating gold microwire and then stripped through the application of a reductive constant current (typically −2 μA). The hydrodynamic conditions are modulated by vibration allowing a short deposition step, which is shown here to be necessary to minimize H₂S volatilization. The limit of detection (LOD) is 30 nM after a deposition step of 7 s. This LOD is in the same range as the most sensitive cathodic voltammetric technique using a mercury drop electrode and is well below those reported previously for other electrodes capable of being implemented in situ.     

The challenge in managing new financial risks: adopting an heuristic or theoretical approach

The financial crisis began with the collapse of Lehman Brothers and the subprime asset backed securities debacle. Credit risk was turned into liquidity risk, resulting in a lack of confidence among financial institutions. In this article, we will propose a way to model liquidity risk and the credit risk in best practices. We will show that liquidity risk is a new type of risk and the current way to deal with it is based solely on observed variables without any theoretical link. We propose an heuristic approach to combine the numerous liquidity risk indicators with a logistic regression for the first time. In regards to credit risk, several articles prove that the best practice is to use an option model to appreciate this risk. We will present our methodology using stochastic diffusion for the interest rate because currently the yield curves aren’t liquid. This approach is more relevant because the basis model in prior publications has a constant interest rate or a forward rate. Both models allow a better understanding of liquidity and credit risks and the further development of research deals with the link between these two financial risks.