Assessing the equation of state and comparing it with other relationships used for determining the surface tension of solids

Some facts regarding the equation of state (EQS) in calculating the surface tension of solids by means of contact angle measurements were manifested. In the present investigation, it was mathematically proved that the surface tension of a solid as estimated by the EQS is in fact equivalent to the Zisman critical surface tension for that same solid. Additionally, the applicability of the EQS's approach in attaining the surface tension of powdered solids by the aid of the capillary rise procedure is also discussed and its limitations are clarified. Furthermore, a methodology was devised so that the surface tension of solids as determined by the EQS could be compared with those calculated by approaches using components of surface tension. This methodology revealed that the applications of approaches based on the geometric mean (i.e. Owens/Wendt and van Oss et al. relationships) are restricted to achieving only high surface tensions of solids.     

Efficient Synthesis and Antibacterial Activities of Some Novel 1,2,3‐Triazoles Prepared from Propargylic Alcohols and Benzyl Azides

A simple and effective procedure for regioselective preparation of 1,2,3‐triazoles from benzyl azides and propargylic alcohols is described using CuSO₄.5H₂O and sodium ascorbate. To screen the antibacterial activity of some newly synthesized triazole derivatives, minimum inhibitory concentration of 3d and 3k was evaluated against gram positive Staphylococcus aureus and Bacillus subtilis and gram negative Escherichia coli and Pseudomonas aeruginosa.     

Fabrication of Micron Level Particles of Amoxicillin by Rapid Expansion of Supercritical Solution

In this study, the rapid expansion of supercritical solution (RESS) process was used to precipitate fine solid particles of amoxiccilin where supercritical carbon dioxide was used as a solvent. The process has been done by changing the RESS parameters, including extraction pressure (150–210 bar), extraction temperature (313–333 K), nozzle length (2–15 mm), effective nozzle diameter (450–1700 µm), and spraying distance (1–10 cm), to investigate the effect of these parameters on the size and morphology of the precipitated amoxicillin particles. The characterization (size and morphology) of the particles was examined using scanning electron microscopy (SEM). Based on the different experimental conditions, the mean particle size of the fabricated particles were between 1.08 and 5.72 µm, while the intact particles of amoxicillin were about 41.46 µm. Also, no regular changes in the morphology of the processed particles were observed.     

Experimental investigation of electrohydrodynamic conduction pumping of various liquids film using flush electrodes

Electrohydrodynamic conduction pumping of free surface liquid film, using flush electrodes has been investigated experimentally for various working fluids. The effective factors in determination of flow direction have been classified and investigated comprehensively. Furthermore, saliency of these factors on hydrodynamic behavior using various electrodes configurations and different fluids has been studied. Results show that the mobility difference and asymmetry of electrodes are main factors in pumping direction and performance, wherein various conditions, each of these factors becomes dominant. Also, efficiency of free surface liquid film conduction pumping has been defined and used to determine the best operating conditions.     

Radial breathing mode frequencies of carbon nanotubes for determination of their diameters

In this paper, exact formulas are obtained for the radial breathing mode (RBM) frequencies of triple-walled carbon nanotubes (TWCNTs) using symbolic package in MAPLE software. For this purpose, TWCNT is considered as triple concentric elastic thin cylindrical shells, which are coupled through van der Waals (vdW) forces between two adjacent tubes. Lennard–Jones potential is used to calculate the vdW forces between adjacent tubes. Then, explicit formulas for RBM frequencies of single-walled (SW), and double-walled (DW) CNTs have been deduced from TWCNT formulas that show an excellent agreement with the available experimental results and the other theoretical model results. The advantage of this analytical approach is that the elastic shell model considers all degrees of freedom in the vibrational analysis of CNTs. To demonstrate the accuracy of this work, the RBM frequencies of different multi-walled carbon nanotubes (MWCNTs) are compared with the available experimental or atomistic results with relative errors of less than 1.5%. To illustrate the application of this approach, the diameters of DWCNTs are obtained from their RBM frequencies which show an excellent agreement with the available experimental results. Also, this approach can be used to determine the diameters of the TWCNTs and MWCNTs. The influence of changing the geometrical and mechanical parameters of a TWCNT on its RBM frequencies has been investigated, too.     

Global Reactivity of Heterostructure Armchair BC2N‐(4,4) Nanotubes: A Density Functional Theory Investigation

Electronic structures of three types of heterostructure armchair BC₂N nanotube besides armchair (4,4)CNT and (4,4)BNNT were calculated by the B3LYP method of density functional theory. The reactivities of nanotubes were discussed by means of obtained vertical ionization potentials and electron affinity potentials. The corresponding electrophilicity values are well correlated with those obtained from the HOMO and LUMO energies of the nanotubes. The good linear correlation found between ω(I,A) and ω(H,L) allows to confirm the use of the easily available B3LYP/6‐31G(d) HOMO and LUMO energies to obtain reasonable values of the global electrophilicity index of nanotubes at a lower computational cost. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:168–173, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21078     

Hopf bifurcation analysis of asymmetrical rotating shafts

The Hopf and double Hopf bifurcations analysis of asymmetrical rotating shafts with stretching nonlinearity are investigated. The shaft is simply supported and is composed of viscoelastic material. The rotary inertia and gyroscopic effect are considered, but, shear deformation is neglected. To consider the viscoelastic behavior of the shaft, the Kelvin–Voigt model is used. Hopf bifurcations occur due to instability caused by internal damping. To analyze the dynamics of the system in the vicinity of Hopf bifurcations, the center manifold theory is utilized. The standard normal forms of Hopf bifurcations for symmetrical and asymmetrical shafts are obtained. It is shown that the symmetrical shafts have double zero eigenvalues in the absence of external damping, but asymmetrical shafts do not have. The asymmetrical shaft in the absence of external damping has a saddle point, therefore the system is unstable. Also, for symmetrical and asymmetrical shafts, in the presence of external damping at the critical speeds, supercritical Hopf bifurcations occur. The amplitude of periodic solution due to supercritical Hopf bifurcations for symmetrical and asymmetrical shafts for the higher modes would be different, due to shaft asymmetry. Consequently, the effect of shaft asymmetry in the higher modes is considerable. Also, the amplitude of periodic solutions for symmetrical shafts with rotary inertia effect is higher than those of without one. In addition, the dynamic behavior of the system in the vicinity of double Hopf bifurcation is investigated. It is seen that in this case depending on the damping and rotational speed, the sink, source, or saddle equilibrium points occur in the system.     

Relative Tor Functors with Respect to a Semidualizing Module

Let C be a semidualizing module over a commutative noetherian ring R. We exhibit an isomorphism $\operatorname{Tor}^{{\mathcal{F}_C}\mathcal{M}}_{i}(-,-) \cong \operatorname{Tor}^{{\mathcal{P}_C}\mathcal{M}}_{i}(-,-)$ between the bifunctors defined via C-flat and C-projective resolutions. We show how the vanishing of these functors characterizes the finiteness of ${{\mathcal{F}_C}\text{-}\operatorname{pd}}$ , and use this to give a relation between the ${{\mathcal{F}_C}\text{-}\operatorname{pd}}$ of a module and of a pure submodule. On the other hand, we show that other isomorphisms force C to be trivial.     

Numerical Solution of Partial Differential Equations in Arbitrary Shaped Domains Using Cartesian Cut-Stencil Finite Difference Method. Part I: Concepts and Fundamentals

A new finite difference (FD) method, referred to as "Cartesian cut-stencil FD", is introduced to obtain the numerical solution of partial differential equations on any arbitrary irregular shaped domain. The 2^nd-order accurate two-dimensional Cartesian cut-stencil FD method utilizes a 5-point stencil and relies on the construction of a unique mapping of each physical stencil, rather than a cell, in any arbitrary domain to a generic uniform computational stencil. The treatment of boundary conditions and quantification of the solution accuracy using the local truncation error are discussed. Numerical solutions of the steady convection-diffusion equation on sample complex domains have been obtained and the results have been compared to exact solutions for manufactured partial differential equations (PDEs) and other numerical solutions.