Critical properties of mixed spin-1 and spin-5/2 with equal and unequal crystal fields

The effects of assuming equal or unequal crystal fields (CF) on the phase diagrams of a mixed spin-1 and spin-5/2 system are investigated in terms of the recursion relations on the Bethe lattice (BL). The equal CF case was considered for the coordination numbers q=3, 4, and 6, while for q=3 the unequal CF case was also studied. It was found that for the equal CF case, the model exhibits second-order phase transitions and two compensation temperatures for all q, the reentrant behavior for q=4 and first-order phase transitions and tricritical point (TCP) for q=6. In the unequal CF case for q=3, the system yields first- and second-order phase transitions, TCP's, and three compensation temperatures. In addition, the TCP's in a very short range are classified as the stable and unstable ones depending on their free energies.     

Synthesis of 1-aryl-substituted-4-chloroimidazo[1,2-a]quinoxalines catalyzed by PdCl2 in water

The reaction of 2-chloro-3-propargylaminoquinoxaline with various aryl iodides and bromides catalyzed by Pd–Cu in the presence of potassium carbonate as the base in water leads to the one-pot formation of 1-aryl-substituted-4-chloroimidazo[1,2-a]quinoxalines in moderate-to-high yields.     

Theoretical study of molecular interactions of phosphorus ylide with HF, HCN, and HN3

The molecular interactions between phosphorous ylide (PY) and HX molecules (X?=?F, CN, and N₃) were investigated using the MP2 method at 6-311++G(2d,2p) basis set. Three different patterns including non-classical hydrogen bond H···C, X···P interaction and classical hydrogen bond H···X were found for complex formation between PY and HX molecules. From the predicted models, stability of the H···C type complexes are greater than other types. Quantum theories of atoms in molecules and natural bond orbitals methods have been applied to analyze the intermolecular interactions. Good correlations have been found between the interaction energies (SE), the second-order perturbation energy E ⁽²⁾, and the charge transfer qCT in the studied systems.     

X-ray CT in the detection of palm weevils

Early detection of the red palm weevils (RPW) is a major challenge in agriculture among all kinds of palm trees due to the nature of the insect and the difficulty to trace them through their life stages associated with the tree life. Many methods have been applied for the weevil detection such as X-ray diffraction techniques, fluoroscopy and ultrasound. On the other hand, the idea of tomography has been used for other purposes such as the determination of the age of the tree and for applied environmental studies. Such technology can also reveal the weevil in principle. In this study, we explore the use of X-ray CT for weevil detection with the Monte Carlo method. A model of the stem of a palm tree is developed for simulations. MCNPX is chosen to carry out the simulations for the radiography tally in the code. The tally records the 2D data of the X-ray beams irradiating the tree model. An iterative reconstruction method for cone beam CT is applied to obtain the 3D slices of the tree model. We are exploring the minimum number of projection angles and the detectability of the weevil. We shall also report the sensitivity of weevil detection using X-ray CT with a large set of simulations with different weevil sizes and tree diameters.     

Convenient synthesis of alkyl thioacetate from alkyl halide using a polymer-supported sodium thioacetate

Alkyl halides are efficiently converted to their corresponding S-alkyl thioacetates under mild and nonaqueous conditions, using polymer-supported sodium thioacetate as a new polymeric reagent at room temperature in high yields and purity. The spent polymeric reagent can be removed quantitatively by filtration and pure products can be obtained by evaporation of the solvent. The spent polymeric reagent can be regenerated and reused several times without its activity changing appreciably.     

Assessment of the derivative-moment transformation method for unsteady-load estimation

It is often difficult, if not impossible, to measure the aerodynamic or hydrodynamic forces on a moving body. For this reason, a classical control-volume technique is typically applied to extract the unsteady forces. However, measuring the acceleration term within the volume of interest using particle image velocimetry (PIV) can be limited by optical access, reflections, as well as shadows. Therefore, in this study, an alternative approach, termed the derivative-moment transformation (DMT) method, is introduced and tested on a synthetic data set produced using numerical simulations. The test case involves the unsteady loading of a flat plate in a two-dimensional, laminar periodic gust. The results suggest that the DMT method can accurately predict the acceleration term so long as appropriate spatial and temporal resolutions are maintained. The major deficiency, which is more dominant for the direction of drag, was found to be the determination of pressure and unsteady terms in the wake. The effect of control-volume size was investigated, suggesting that larger domains work best by minimizing the associated error in the determination of the pressure field. When decreasing the control-volume size, wake vortices, which produce high gradients across the control surfaces, are found to substantially increase the level of error. On the other hand, it was shown that for large control volumes, and with realistic spatial resolution, the accuracy of the DMT method would also suffer. Therefore, a delicate compromise is required when selecting control-volume size in future experiments.     

On exact solutions for thin film flows of a micropolar fluid

The present paper contains the exact solutions for thin film flows of a micropolar fluid. Thin films are considered for three different geometries namely: (i) flow down an inclined plane, (ii) flow on a moving belt and (iii) flow down a vertical cylinder. The exact solution is obtained for the velocity and micro-rotation in first two cases for both weak and strong concentrations of the microelements. However, the exact expression for the micro-rotation is obtained for the third case and a numerical solution is presented for the velocity. The micro-rotation and velocity fields are sketched and discussed for different values of the material parameters. It is observed that the rotation of the microelements at the boundary increases the velocity when compared with the case when there is no rotation at the boundary.