Two- and three-dimensional comparative study of heat transfer and pressure drop characteristics of nanofluids flow through a ventilated cubic cavity (part I: Newtonian nanofluids)

Journal of Thermal Analysis and Calorimetry - Through this paper, three-dimensional fluid flow and heat transfer of Al2O3 nanofluid within ventilated enclosures was taken into consideration....     

Application of differential electrolytic potentiometry for detection in flow injection analysis

The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml⁻¹ chloride. For solutions below this concentration, the relation is linear.     

Equivalences of comodule categories for coalgebras over rings

In this article we defined and studied quasi-finite comodules, the cohom functors for coalgebras over rings. Linear functors between categories of comodules are also investigated and it is proved that good enough linear functors are nothing but a cotensor functor. Our main result of this work characterizes equivalences between comodule categories generalizing the Morita-Takeuchi theory to coalgebras over rings. Morita-Takeuchi contexts in our setting is defined and investigated, a correspondence between strict Morita-Takeuchi contexts and equivalences of comodule categories over the involved coalgebras is obtained. Finally, we proved that for coalgebras over QF-rings Takeuchi's representation of the cohom functor is also valid.     

Synthesis,dynamic light scattering,and luminescence properties of copolymers containing iridium(III) bisterpyridine in the side chain

Supramolecular block‐random copolymers containing [Ir(terpy)₂]³⁺ in the side chain were synthesized via postfunctionalization of a P(S‐b‐AC_terpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐AC_terpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007     

Eigenvalue Spectrum of a Dirac Particle in Static and Spherical Complex Potential

It has been observed that a quantum theory need not be Hermitian to have a real spectrum. We study the non-Hermitian relativistic quantum theories for many complex potentials, and obtain the real relativistic energy eigenvalues and corresponding eigenfunctions of a Dirac-charged particle in complex statically and spherically symmetric potentials. Complex Dirac–Eckart, complex Dirac–Rosen–Morse II, complex Dirac–Scarf and complex Dirac–Poschl–Teller potential are investigated.     

Heat transfer and flow induced by both natural convection and vibrations inside an open-end vertical channel

The effects of oscillatory motions that may present at a wall during vibrating conditions are studied on flow induced by natural convection and heat transfer inside an open-end vertical channel. The governing equations are non-dimensionalized and reduced to simpler forms. Analytical solutions are obtained for several limiting cases. The reduced governing equations are solved for various values of the controlling parameters. It is found that mean values of average Nusselt numbers are mainly affected by the Grashof number and the amplitude of the horizontal vibrations. Further, amplitudes of Nusselt numbers at the vibrated wall are decreased as the Grashof number increases for horizontal vibrations while they are increased as amplitudes of vibrations increase. It is also found that the squeezing/vibrational Reynolds number, Grashof number and amplitudes of vibrations have a great influence on the trends of stream lines and isotherms especially at low Grashof numbers. Finally, correlations that summarize the effects of the different controlling parameters are determined on the Nusselt numbers and their amplitudes at relatively low frequency of vibrations.     

Transient creep during transformation in Cd-Zn alloys

Transient creep of Cd-2 wt. % Zn and Cd-17·4 wt. % Zn alloys has been studied under different constant stresses ranging from 6·4 MPa to 12·7 MPa near the transformation temperature. The results of both compositions showed two transient deformation regions, the low temperature region (below 483 K) and the high temperature region (above 483 K). From the transient creep described by the equation _tr=Bt ⁿ, where _tr andt are the transient creep strain and time. The parametersB andn were calculated. The parameterB was found to change with the applied stress from 0·3×10^–4 to 3×10^–4 and from 0·6×10^–4 to 18×10^–4 for Cd-2 wt. % Zn and Cd-17·4 wt. % Zn, respectively. The exponentn was found to change from 0·8 to 0·95 for both alloys. The parameterB was related to the steady state creep rate through the equation , the exponent was found to be 0·5 for Cd-2 wt. % Zn and 0·6 for the eutectic composition. The activation energies of transient creep in the vicinity of the transformation regions (above 483 K) were found to be 50·2 kJ/mole for Cd-2 wt. % Zn and 104·7 kJ/mole for the eutectic composition characterizing the mechanisms of grain boundary diffusion and volume diffusion in Cd, respectively.     

Stability-indicating high-performance liquid chromatographic assay of buspirone HCl

The United States Pharmacopoeia high-performance liquid chromatographic (HPLC) assay method of buspirone is not able to discriminate buspirone from its degradation products. The purpose of this work is to develop a sensitive, selective, and validated stability-indicating HPLC assay for the analysis of a buspirone hydrochloride in a bulk drug. Buspirone HCI and its potential impurities and degradation products are analyzed on an Ultrasphere C18 column heated to 40 degrees C using a gradient program that contains monobasic potassium phosphate buffer solution (pH 6.9) and acetonitrile-methanol mixture (13:17) of 35% for 5 minutes, then increased to 54% in 5.5 minutes. The samples are monitored using a photo-diode array detector and integrated at 244 and 210 nm. The stress testing of buspirone HCI shows that buspirone acid hydrochloride is the major degradation product. The developed method shows a separation of buspirone degradation product and its potential impurities in one run. The stability of buspirone HCI is studied under accelerated conditions in order to provide a rapid indication of differences that might result from a change in the manufacturing process or source of the sample. The forced degradation conditions include the effect of heat, moisture, light, acid-base hydrolysis, sonication, and oxidation. The compatibility of buspirone HCI with some pharmaceutical excipients is studied under stress conditions. The linear range of buspirone HCI is between 5 and 200 ng/microL with a limit of quantitation of 2.5 ng/microL. The intraassay percentage deviation is not more than 0.38%, and the day-to-day variation was not more than 0.80%. The selectivity, repeatability, linearity, range, accuracy, sample solution stability, ruggedness, and robustness show acceptable values.     

Synthesis of functionalized analogs of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia

Using an improved synthesis of pyochelin, a siderophore common to several pathogenic Pseudomonas species, three functionalized pyochelin analogs were efficiently synthesized starting from appropriate 2-hydroxybenzonitriles.     

Electronic communication through the ureylene bridge: spectroscopy, structure and electrochemistry of dimethyl 1,1-ureylenedi(1-ferrocenecarboxylate)

Dimethyl 1^′,1^′-ureylenedi(1-ferrocenecarboxylate) (1) formed during the synthesis of 1-amino, 1^′-ferrocenecarboxylic acid shows virtual molecular centrosymmetry. Electronic coupling between the two Fc groups through the ureylene bridge results in both Fc groups being individually oxidizable (ΔE_1/2?0.14 V). The possible existence of intermolecular electronic communication has discussed. The oxidation was followed by spectroelectrochemistry. The separation between the two halfwave potentials ΔE_1/2=137±5 mV and the comproportionation constant K_c=207.