The Effect of pH and Temperature on the Sorption of Zinc(II), Cadmium(II), and Aluminum(III) onto New Metal-Ligand Complexes of Sporopollenin

Sorption of metal ions from aqueous solution onto metal-ligand complexes of sporopollenin derivatives has been measured as a function of pH at several temperatures between 20 and 50°C. Novel metal-ligand exchange resins possessing oxime and carboxylic acid sidearm functionality were prepared through the reaction of diaminosporopollenin with dichloro-antiglyoxime and bromoacetic acid. The pH dependencies and sorption isotherms of various metal ions such as Zn(II), Cd(II), and Al(III) on the resin were investigated from aqueous solution. The sorption behavior of these metal-ligand complexes of sporopollenin derivatives and the possibilities of selectively removing and recovering heavy metals are explained on the basis of their chemical nature and complex properties and the results are interpreted in terms of the variations of pH.     

Formation and characterization of polymersomes made by a solvent injection method

In this article a solvent injection method is described for vesicle formation using poly(butadiene)‐ b‐poly(acrylic acid) diblock copolymers as the amphiphilic molecules. Vesicles composed of polymer bilayers are commonly referred to as polymersomes. Solvent injection is shown to be a rapid method for polymersome formation suitable to make large volumes of polymersome solution. The method can be manipulated to obtain a wide range of vesicle sizes depending on the polymer concentration and preparation conditions. Polymersome solutions in this study are characterized using dynamic light scattering (DLS), fluorescent microscopy, and electron microscopy. Polymersome sizes range from tens of nanometers to several microns. The membrane thickness of smaller polymersomes is found to lie between 14–20 nm. Larger polymersomes are found to have somewhat thicker membranes. The procedure involves the addition of polymers dissolved in an organic solvent to a stirred aqueous solution. The formation of polymersomes by this method is proposed to be governed by the limited mutual solubility of the two solvents and the simultaneous diffusion of solvent and water out of and in to initially formed organic solvent droplets. Copyright © 2007 John Wiley & Sons, Ltd.     

On generalized recurrent Riemannian manifolds

The object of the present paper is to study a type of Riemannian manifolds called generalized recurrent manifolds. We have constructed two concrete examples of such a manifold whose scalar curvature is non-zero non-constant. Some other properties have been considered. Among others it is shown that on a generalized recurrent manifold with constant scalar curvature, Weyl-semisymmetry and semisymmetry are equivalent. Sufficient condition for a generalized recurrent manifold to be a special quasi Einstein manifold is obtained.     

Scattering of sound waves by a turbulent wake

In this investigation, the Doppler shifted power spectrum of the scattering cross-section is obtained for plane acoustic waves scattered by fluid flow fluctuations appropriate to a turbulent wake. The wake considered in this paper is assumed almost homogeneous and isotropic and of low Reynolds number.It is shown that the evaluation of the Doppler scattering cross-section essentially reduces to the calculation of the wave number converted and frequency shifted energy spectrum function of the turbulent flow fluctuations. In prescribing the low Reynolds number turbulence spectrum, inertial forces are assumed negligible. Convective effects of the macro-eddies, which cause a Doppler shift in the scattered waves, are considered using a Lagrangian-type of space-time velocity correlation.After finding the spectrum of turbulent fluctuations, the Doppler shifted power spectrum of the scattering cross-section, which characterizes the scattered waves, is obtained explicitly for the far field approximation.     

Nonlocal surface plasmon spectrum in quantizing magnetic field: Surface Bernstein mode branch (n=2)

The nonlocal surface plasmon spectrum in a quantizing magnetic field perpendicular to the surface has been found to have branches analogous to ‘Bernstein’ modes near multiples of the cyclotron frequency. The n=2 nonlocal surface ‘Bernstein’ mode is evaluated for low wavenumber, incorporating Landau quantization effects for degenerate and nondegenerate cases.     

Enantioselective Dearomatization of Indoles by an Azoalkene-Enabled (3+2) Reaction: Access to Pyrroloindolines

The enantioselective dearomatization of indoles by an organocatalytic (3+2) reaction has been established. The reaction makes use of simple indole derivatives as substrates, and employs azoalkenes reaction partners. A wide range of pyrroloindolines containing an all-carbon quaternary stereogenic center were readily prepared in high yields and with excellent enantioselectivities.     

Oxidation parameters determination of Cu–Al–Ni–Fe shape-memory alloy at high temperatures

In this study, isothermal oxidation behavior of a Cu–Al–Ni–Fe shape-memory alloy between 500 and 900 °C was investigated. Alloy samples were exposed to oxygen by TG/DTA for 1 h at a constant temperature, allowing for calculation of the oxidation constant and activation energy values of the oxidation process. The oxidation constant value increased with temperature, reaching saturation at 800 °C. The effect of oxidation on crystal structure, surface morphology and chemical composition of the Cu–Al–Ni–Fe alloy was determined by X-ray diffractometer (XRD) and scanning electron microscope (SEM)–energy-dispersive X-ray (EDX) analyses. With increasing oxidation temperature, number and intensity of the characteristic 18R martensite phase peaks were reduced while Al₂O₃ phase peaks were increased. In parallel to the XRD results, the same variations were also detected by SEM–EDX measurements.     

New Amperometric Cholesterol Biosensors Using Poly(ethyleneoxide) Conducting Polymers

Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.