Conductance Study of the Binding of K+ by Dibenzo-pyridino-18-crown-6 and 1,10-N,N′-didecyl-diaza-18-crown-6 in Acetonitrile

The binding of K+ by dibenzo-pyridino-18-crown-6 (B2-py-18-C-6) and1,10-N,N-didecyl-diaza-18-crown-6 (22-DD) has been studiedconductometrically at 10, 15, 20 and 25 °C in acetonitrile. Thecomplexes formed were assumed to have 1 : 1 stoichiometry. The complexes ofK+ with 18-crown-6 (18-C-6) and dibenzo-18-crown-6 (B2-18-C-6) were alsostudied for comparison purposes. The stability constant, K, of a givencomplex and its molar conductance, c, were obtained by subjectingthe conductance data to a non-linear least-squares curve fitting procedure.The values of the enthalpy change, H, the entropy change, Sand the Gibbs free energy, G, associated with the formation of the 1: 1 complexes were derived and compared with relevant literature data. Thevalues of G at 25 °C indicate that the binding capacity of thefour macrocycles follows the order 18-C-6 > 22-DD > B2-18-C-6 >B2-py-18-C-6. The difference between the molar ionic conductance of the freeK+ cation and that of the bound cation, KL+, was estimated and the trend insuch differences correlates with the molecular size of the macrocycle, L.     

Levels of mercury,cadmium, lead and other selected elements in canned tuna fish commercialised in Jordan

During 2010, the concentrations of mercury and eight other trace elements in 90 canned tuna samples commercialised in Jordan were determined using mercury analyser (Hydra C®) and the inductively coupled plasma-optical emission spectrometer (ICP-OES). The mean concentrations and ranges for elements analysed in mg?kg ^{? 1} (wet base) were as follows: total Hg (0.21; 0.06–0.57), Cd (0.06;?<?0.01–0.63), Pb (0.09; <0.04–0.24), total As (0.74; 0.11–1.56), Ni (0.51; 0.03–2.85), V (0.04; <0.03–0.1), Al (0.26; 0.08–1.63), Ba (0.13; 0.05–0.42) and Ag was not detected in any of the analysed samples (<0.02?mg?kg^?1). The data obtained in the present study compared well with data obtained from similar studies carried out in different parts of the world. Few samples had the mercury and cadmium levels slightly exceeding the Codex Committee on Food Additives and Contaminants draft guidelines. However, the estimated weekly intakes of these metals showed that there was no health risk associated with the consumption of the analysed canned tuna samples.     

In vivo lipid diffusion coefficient measurements in rat bone marrow

The diffusion coefficient of lipids, D_l, within bone marrow, fat deposits and metabolically active intracellular lipids in vivo will depend on several factors including the precise chemical composition of the lipid distribution (chain lengths, degree of unsaturation, etc.) as well as the temperature. As such, D_l may ultimately prove of value in assessing abnormal fatty acid distributions linked to diseases such as cystic fibrosis, diabetes and coronary heart disease. A sensitive temperature dependence of D_l may also prove of value for MR-guided thermal therapies for bone tumors or disease within other fatty tissues like the breast. Measuring diffusion coefficients of high molecular weight lipids in vivo is, however, technically difficult for a number of reasons. For instance, due to the much lower diffusion coefficients compared to water, much higher b factors than those used for central nervous system applications are needed. In addition, the pulse sequence design must incorporate, as much as possible, immunity to motion, susceptibility and chemical shift effects present whenever body imaging is performed. In this work, high b-factor line scan diffusion imaging sequences were designed, implemented and tested for D_l measurement using a 4.7-T horizontal bore animal scanner. The gradient set available allowed for b factors as high as 0.03 μs/nm² (30,000 s/mm²) at echo times as short as 42 ms. The methods were used to measure lipid diffusion coefficients within the marrow of rat paws in vivo, yielding lipid diffusion coefficients approximately two orders of magnitude smaller than typical tissue water diffusion coefficients. Phantom experiments that demonstrate the sensitivity of lipid diffusion coefficients to chain length and temperature were also performed.     

Construction of Third-Order Diagonal Implicit Runge-Kutta Methods for Stiff Problems

We presents a new third-order diagonally implicit Runge~Kutta integration formula for stiff initial value problems, designed to be A-stable methods. The stability of the methods is analyzed and numerical results are shown to verify the conclusions.     

On the strong field dependence and nonlinear response to gadolinium contrast agent of proton transverse relaxation rates in dairy cream

Dairy cream, as a suspension of lipid droplets in water, is a potentially useful magnetic resonance imaging (MRI) phantom material and an interesting material for studying fundamental relaxation mechanisms. Here we report a strong increase in the transverse relaxation rates with field strength for both the water and lipid protons in dairy cream. Also, studies at 4.7 T reveal a nonlinear response of transverse relaxation rates with increasing concentration of a common gadolinium (Gd)-based contrast agent, including an initial decrease of water relaxation rates as measured with Hahn spin echoes at the lower Gd concentrations. The results are treated within the framework of a model in which the magnetic susceptibility difference between the lipid droplets and the aqueous phase plays the prominent role for transverse relaxation. Second-order polynomial fits of the water proton transverse relaxation rate dependence on field strength and on Gd concentration at 4.7 T provided experimental parameters from which model parameters are extracted and compared with expectations available from the literature.     

Knowledge management: a review of the field and of OR's contribution

This paper examines the field of knowledge management (KM) and identifies the role of operational research (OR) in key milestones and in KM's future. With the presence of the OR Society journal Knowledge Management Research and Practice and with the INFORMS journal Organization Science, OR may be assumed to have an explicit and a leading role in KM. Unfortunately, the origins and the evidence of recent research efforts do not fully support this assumption. We argue that while OR has been inside many of the milestones there is no explicit recognition of its role and while OR research on KM has considerably increased in the last 5 years, it still forms a rather modest explicit contribution to KM research. Nevertheless, the depth of OR's experience in decision-making models and decision support systems, soft systems with hard systems and in risk management suggests that OR is uniquely placed to lead future KM developments. We suggest that a limiting aspect of whether OR will be seen to have a significant profile will be the extent to which developments are recognized as being informed by OR.     

Crystallographic and computational study of the structure of copper(II) 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl

The reaction of M(OAc)₂ with 2,2′-bis(2-hydroxybenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl (H₂L1) allows the synthesis of 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl complexes of Cu(II) (CuL1), Co(II) (CoL1) and Ni(II) (NiL1) that were characterized by elemental analysis, FTIR spectroscopy and for CuL1 also by X-ray crystallography verifying a tetradentate binding mode of L1 via an (ONNO) motif of the two phenolic oxygen atoms and two azomethine nitrogen atoms. Recrystallization from a solvent mixture of dichloromethane and methanol promotes the formation of methanol adducts. Different binding modes of the methanol–complex were investigated using density functional theory calculations and binding energies, and thermodynamic data of the interaction are reported. The results show that the favored interaction occurs when the methanol molecule acts as a Lewis acid weakly binding via an O–H···O hydrogen bridge to a phenoxide moiety leading to an elongation of the respective M–O bond.

     

The effects of the secondary fluid temperature on the energy transfer in an unsteady ejector with a radial-flow diffuser

Unsteady ejectors are devices whereby energy is exchanged between directly interacting fluids. Unlike steady ejectors, the mechanism responsible for the energy transfer is reversible in nature and thus higher efficiencies are perceivable. A potential application for PEE is for enhancement in output power per weight as in turbochargers. The unsteady ejector when used as a turbocharger the device is expected to perform under wide range of ambient temperatures. Therefore, it is important to investigate the effects of the temperature of the induced ambient air on the energy transfer. The radial-flow ejector, which usually leads to higher-pressure ratios with fewer stages, was selected for the investigation. The flow field is investigated at two Mach numbers 2.5 and 3.0 utilizing rectangular short-length supersonic nozzles for accelerating the primary fluid. Fundamental to the enhancement of these devices performance relies on the management of the flow field in such a way to minimize entropy production. The numerical analyses were conducted utilizing a package of computational fluid dynamics.     

Hamilton-Jacobi fractional mechanics

As a continuation of Rabei et al. work [Eqab M. Rabei, Khaled I. Nawafleh, Raed S. Hijjawi, Sami I. Muslih, Dumitru Baleanu, The Hamilton formalism with fractional derivatives, J. Math. Anal. Appl. 327 (2007) 891-897], the Hamilton-Jacobi partial differential equation is generalized to be applicable for systems containing fractional derivatives. The Hamilton-Jacobi function in configuration space is obtained in a similar manner to the usual mechanics. Two problems are considered to demonstrate the application of the formalism. The result is found to be in exact agreement with Agrawal's formalism.