Pressure drop in alternating curved tubes

Pressure drop measurements in the laminar and turbulent regions for water flowing through an alternating curved circular tube (x=h sin 2πz/λ) are presented. Using the minimum radius of curvature of this curved tube in place of that of the toroidally curved one in calculating the Dean number (ND=Re(D/2R _c )², it is found that the resulting Dean number can help in characterizing this flow. Also, the ratio between the height and length of the tube waves which represents the degree of waveness affects significantly the pressure drop and the transition Dean number. The following correlations have been found:

1. For laminar flow: $$F_w \left( {\frac{{2R_c }}{D}} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} = F_s \left( {\frac{{2R_c }}{D}} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} + 0.03,\operatorname{Re}< 2000.$$
2. For turbulent flow: $$F_w \left( {\frac{{2R_c }}{D}} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} = F_s \left( {\frac{{2R_c }}{D}} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} + 0.005,2000< \operatorname{Re}< 15000.$$
3. The transition Dean number: $$ND_{crit} = 5.012 \times 10^3 \left( {\frac{D}{{2R}}} \right)^{2.1} ,0.0111< {D \mathord{\left/ {\vphantom {D {2R_c }}} \right. \kern-\nulldelimiterspace} {2R_c }}< 0.71.$$

     

Radiative and Thermal Dispersion Effects on Non-Darcy Natural Convection with Lateral Mass Flux for Non-Newtonian Fluid from a Vertical Flat Plate in a Saturated Porous Medium

The problem of natural convective heat transfer for a non-Newtonian fluid from an impermeable vertical plate embedded in a fluid-saturated porous medium has been analyzed. Non-Darcian, radiative and thermal dispersion effects have been considered in the present analysis. The governing boundary layer equations and boundary conditions are cast into a dimensionless form and simplified by using a similarity transformation. The resulting system of equations is solved by using a double shooting Runge–Kutta method. The effect of viscosity index n, the conduction–radiation parameter R, the non-Darcy parameter Gr*, the thermal dispersion parameter Ds and the suction/injection parameter f_w on the fluid velocities, temperatures and the local Nusselt number are discussed.     

Synthesis of Ag nanoparticles for the electrochemical detection of anticancer drug flutamide

Ag nanoparticles were synthesized on the surface of a glassy carbon electrode modified with p‐tert‐butylcalix[4]arene and p‐tert‐butylcalix[6]arene by the deposition of Ag+at an open circuit potential ...     

Shear-opposed mixed-convection flow and heat transfer in a narrow, vertical cavity

A combined experimental and theoretical study has been carried out to investigate mixed-convection heat transfer in a narrow, vertical cavity. The shear force is produced at the left side of a cavity by a belt moving upward that constitutes the sixth wall of the cavity. The left wall of the cavity was cooled and the opposite (right wall) was heated. Hence, the buoyancy force tries to bring the fluid down, and the shear force tends to induce upward fluid flow. The test cell was equipped with two heat exchangers and three thermocouple racks for measuring the temperature distributions at 12 different positions. The temperature field was scanned in the cavity for various flow and temperature boundary conditions. Three-and-two-dimensional laminar models were used to analyze the problem theoretically. The experimental measurements were found to be in good agreement with the numerical predictions.     

Strength of interactions between immobilized dye molecules and sol-gel matrices

In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel.     

Theoretical investigation into competing unimolecular reactions encountered in the pyrolysis of acetamide

Motivated by the necessity to understand the pyrolysis of alkylated amines, unimolecular decomposition of acetamide is investigated herein as a model compound. Standard heats of formation, entropies, and heat capacities, are calculated for all products and transition structures using several accurate theoretical levels. The potential energy surface is mapped out for all possible channels encountered in the pyrolysis of acetamide. The formation of acetamedic acid and 1-aminoethenol and their subsequent decomposition pathways are found to afford the two most energetically favored pathways. However, RRKM analysis shows that the fate of acetamedic acid and 1-aminoethenol at all temperatures and pressures is to reisomerize to the parent acetamide. 1-Aminoethenol, in particular, is predicted to be a long-lived species enabling its participation in bimolecular reactions that lead to the formation of the major experimental products. Results presented herein reflect the importance of bimolecular reactions involving acetamide and 1-aminoethenol in building a robust model for the pyrolysis of N-alkylated amides.     

Asymptotic formulae for eigenvalues and eigenfunctions of q‐Sturm‐Liouville problems

We investigate the asymptotic behavior of the eigenvalues and the eigenfunctions of q‐Sturm‐Liouville eigenvalue problems. For this aim we study the asymptotic behavior of q‐trigonometric functions as well as fundamental sets of solutions of the associated second order q‐difference equation. As in classical Sturm‐Liouville theory, the eigenvalues behave like zeros of q‐trigonometric functions and the eigenfunctions behave like q‐trigonometric functions. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

The kernel method and systems of functional equations with several conditions

We generalize the kernel method to equation systems in which the number of unknowns is allowed to exceed the number of equations. With this generalization, we derive the generating functions for several kinds of sequences and generating trees whose recursions are dependent on the parity of the indices.     

Multilinear gradient elution optimization in reversed-phase liquid chromatography based on logarithmic retention models: application to separation of a set of purines, pyrimidines and nucleosides

The analytical solutions of the fundamental equation of the multilinear gradient elution are derived in two cases, when the dependence of the logarithm of the solute retention (lnk) upon the volume fraction of organic modifier (φ) is a three-parameter logarithmic expression, and when a simple linear relationship between lnk and lnφ is adopted. The derived theoretical expressions for retention times under multilinear gradient conditions are embodied to simple algorithms for fitting gradient data and especially for resolution optimization. Their performance was examined by using a mixture of 16 model compounds chosen among purines, pyrimidine and nucleosides in eluting systems modified by acetonitrile. It was found that the accuracy of the predicted gradient retention times is very satisfactory even if the simple logarithmic expression for the retention behavior of solutes, i.e. the linear dependence of lnk upon lnφ, is used.     

In vitro cytotoxic evaluation of some new heterocyclic sulfonamide derivatives

Sulfonamide‐bearing compounds posses many types of biological activities and have been recently reported to show substantial antitumor activity in vitro and/or in vivo. There are a variety of mechanisms for the anticancer activity, and the most prominent mechanism is the inhibition of carbonic anhydrase isozymes. This work reports the synthesis of some new quinoline, pyrimido[4,5‐b]quinoline and 3,1‐oxazinoquinoline derivatives bearing a sulfonamide moiety. All the newly synthesized compounds were evaluated for their in vitro anticancer activity against Ehrlich ascites carcinoma cells. Compounds 10 , 13 , and 26 were the most active compounds with IC₅₀ values of 6.1 μM, 6.8 μM, and 6.4 μM, respectively, and exhibited better activities than the reference drug doxorubicin (IC₅₀ = 68.1 μM). J. Heterocyclic Chem., 2011.