Modified Glaser Reaction of Terminal Alkynes on KF/Alumina

Summary. A variety of 1,3-diyne compounds are prepared in a solvent-free reaction on KF/alumina in the presence of catalytic amounts of Cu(OAc)₂·H₂O with up to 96% yields at room temperature.     

Phase-Transfer-Catalyzed Michaelis-Becker Synthesis of Dialkyl Methyl Phosphonates

A liquid–liquid phase-transfer-catalyzed (PTC) Michaelis-Becker reaction was adopted in the preparation of dialkyl methyl phosphonate (R = Me, iPr, nBu, and iBu). This was performed by the reaction of an appropriate dialkyl hydrogen phosphonate with methyl iodide in the presence of benzyl triethyl ammonium chloride and sodium hydroxide as PTC and base, respectively. A liquid–liquid two-phase system (H₂O/CH₂Cl₂) introduced a suitable situation for the preparation of dialkyl methyl phosphonates with bulky alkyl groups (R = iPr, nBu, and iBu), but with R = Me, the hydrolysis of dimethyl hydrogen phosphonate (reagent) reduced the yield to 22%. In this case, a solid–liquid PTC-free system was successfully applied and yield of over 80% was obtained.     

Numerical study of convective heat transfer and fluid flow around two side by side square cylinders using k - \omega - \overline{{\upsilon^{2} }} - f turbulence model

The effect of spacing between two identical square cylinders placed side by side on the fluid flow and heat transfer is numerically investigated using $ k - \omega - \overline{{\upsilon^{2} }} - f $ turbulence model. The present study is performed at Pr = 0.7 and Re = 10,000, 21,000 for different scaled gap spacing between cylinders in the range of Gl = 0.5–6. It should be noted all geometrical lengths such as Gl are scaled with cylinders side. In order to show the accuracy of $ k - \omega - \overline{{\upsilon^{2} }} - f $ model, part of the results such as various flow patterns (flip-flop, in-phase and anti-phase) and global quantities are compared with the available numerical and experimental results and also a Large Eddy Simulation study of the present work. Based on this comparison, a close agreement is observed. The local and averaged flow and thermal quantities are also compared for two side by side square and circular cylinders and some significant similarities and differences are presented. Progressive increasing and decreasing of the distance between cylinders indicates that the hysteresis phenomenon appears for the gap spacing in the range of Gl = 1–2.5. In the hysteresis range, two different patterns are observed for each distance in the aforementioned range. Also in this range, two different values are found for different quantities such as lift and drag coefficients, Strouhal number and Nusselt number.     

Structural and particle size evolution of sol–gel-derived nanocrystalline hydroxyapatite

An easy alkoxide-based sol–gel method based on Ca(NO₃)₂·4H₂O and triethyl phosphate [PO(OC₂H₅)₃; TEP] as Ca and P precursors have been developed to synthesize nano-hydroxyapatite (HA). The structural evolution of the samples was studied using X-ray diffraction (XRD), thermal behavior, infrared analysis, and elemental analysis via scanning electron microscopy. It is noticeable that raising of the firing temperature resulted in increasing the HA content as the dominant phase at 600 and 700 °C. The phase transformation from amorphous to crystalline HA occurred at the low temperature of 400 °C, while at higher temperatures other Ca–P compounds as secondary phases transformed to HA. The crystallite size distributions and micro-strain of the HA samples produced were characterized by XRD methods with the aid of Scherrer and Williamson–Hall equations. The results of transmission electron microscopy as a complementary and reliable technique are in good agreement with those obtained from XRD. The results indicate that increasing the firing temperature caused permanent growth of mean crystallite size and a decrease in micro-strain.     

Calculation of chemical shielding in C-doped zigzag BN nanotubes

Abstract  

Chemical shielding tensors at the sites of various ¹¹B and ¹⁵N nuclei were calculated to study the electronic structure properties of carbon-doped boron nitride nanotubes. The chemical shielding tensors were converted to isotropic and anisotropic chemical shielding parameters. The results reveal the significant effect of C-doping on the chemical shielding tensors at the sites of those ¹¹B and ¹⁵N nuclei located in the nearest neighborhood of the C-doped ring. The isotropic and anisotropic chemical shielding tensors of those B atoms directly bonded to C atoms reach values observed for B atoms placed at the B-mouth of the nanotube.     

Flexural sensitivity and resonance of cantilever micro-sensors based on nonlocal elasticity theory

Sensors based on microcantilevers, especially ones with uniform structure, have ultrahigh sensitivities. The normalized natural frequencies and the sensitivity of lateral vibration of an elastic microcantilever sensor in contact with a surface are derived analytically based on the Euler–Bernoulli beam theory by taking into account the small scale effect. The interaction of the sensor with the surface is modeled by linear springs, which restricts the results to experiments involving low-amplitude excitations. The results show that the normalized natural frequencies of nonlocal microcantilever are smaller than those for its local counterpart, especially for higher values of small scale parameters. Also, each mode has a different sensitivity to variations in surface stiffness. Moreover, the most sensitivity is observed at the first mode of vibration. When the nonlocal effect is not taken into account, the natural frequencies and the sensitivity of the microcantilever in contact with the surface are compared with those obtained in previous study without considering the nonlocal effect.     

Noise Effects on Entangled Coherent State Generated via Atom-Field Interaction and Beam Splitter

In this paper, we introduce a controllable method for producing two and three-mode entangled coherent states (ECS’s) using atom-field interaction in cavity QED and beam splitter. The generated states play central roles in linear optics, quantum computation and teleportation. We especially focus on qubit, qutrit and qufit like ECS’s and investigate their entanglement by concurrence measure. Moreover, we illustrate decoherence properties of ECS’s due to noisy channels, using negativity measure. At the end the effect of noise on monogamy inequality is discussed.     

Chemical shielding properties for BN,BP, AlN,and AlP nanocones: DFT studies

The properties of boron nitride (BN), boron phosphide (BP), aluminum nitride (AlN), and aluminum phosphide (AlP) nanocones were investigated by density functional theory (DFT) calculations. The investigated structures were optimized and chemical shielding (CS) properties including isotropic and anisotropic CS parameters were calculated for the atoms of the optimized structures. The magnitudes of CS parameters were observed to be mainly dependent on the bond lengths of considered atoms. The results indicated that the atoms could be divided into atomic layers due to the similarities of their CS properties for the atoms of each layer. The trend means that the atoms of each layer detect almost similar electronic environments. Moreover, the atoms at the apex and mouth of nanocones exhibit different properties with respect to the other atomic layers.