Cytotoxic effect,enzyme inhibition,and in silico studies of some novel N-substituted sulfonyl amides incorporating 1,3,4-oxadiazol structural motif

Molecular Diversity - The acetylcholinesterase and carbonic anhydrase inhibitors (AChEIs and hCAIs) remain key therapeutic agents for many bioactivities such as anti-Alzheimer and antiobesity...     

Temperature dependent energy relaxation time in AlGaN/AlN/GaN heterostructures

The two-dimensional (2D) electron energy relaxation in Al_0.25Ga_0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (T_e) of hot electrons was obtained from the lattice temperature (T_L) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range T_e > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al_0.25Ga_0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures.     

Laguerre-Gaussian beam scintillation on slant paths

Scintillation evaluations for Laguerre-Gaussian (LG) beams for slant paths are made using Rytov approximation. On- and off-axis scintillation is formulated and calculated up to several tens of kilometers of slant distances for different zenith angles. Scintillation index variations against radial receiver point and different source sizes are also investigated. In all cases evaluated, it is found that LG beams with higher radial mode numbers result in less scintillation than Gaussian beam. Kolmogorov spectrum function is utilized in the scintillation calculations.     

Some Tauberian conditions for Cesàro summability method

Let u = (u _n ) be a sequence of real numbers whose generator sequence is Cesàro summable to a finite number. We prove that (u _n ) is slowly oscillating if the sequence of Cesàro means of (ω _n ^(m−1)(u)) is increasing and the following two conditions are hold:

Design,modelling and simulation of a new nonlinear and full adaptive backstepping speed tracking controller for uncertain PMSM

In this study, a new nonlinear and full adaptive backstepping speed tracking control scheme is developed for an uncertain permanent magnet synchronous motor (PMSM). Except for the number of pole pairs, all the other parameters in both PMSM and load dynamics are assumed unknown. Three phase currents and rotor speed are supposed to be measurable and available for feedback in the controller design. By designing virtual control inputs and choosing appropriate Lyapunov functions, the final control and parameter estimation laws are derived. The overall control system possesses global asymptotic stability; all the signals in the closed loop system remain bounded, according to stability analysis results based on Lyapunov stability theory. Further, the proposed controller does not require computation of regression matrices, with the result that take the nonlinearities in quite general. Simulation results clearly exhibit that the controller guarantees tracking of a time varying desired reference speed trajectory under all the uncertainties in both PMSM and load dynamics without singularity and overparameterization. The results also show that all the parameter estimates converge to their true values on account of the fact that reference speed signal chosen to be sufficiently rich ensures persistency of excitation condition. Consequently, the proposed controller ensures strong robustness against all the parameter uncertainties and unknown bounded load torque disturbance in the PMSM drive system. Numerical simulations demonstrate the performance and feasibility of the proposed controller.     

Ruthenium(II) complexes bearing pyridine‐based tridentate and bidentate ligands: catalytic activity for transfer hydrogenation of aryl ketones

Ru(II) complexes of the general formula [RuCl₂(′′)(L)] (1: ′N = N_b, L = MeOH; 2: ′N = N_b, L = CH₃CN; 3: ′N = N_d, L = CH₃CN; 4: ′N = N_p, L = CH₃CN), [Ru(p‐cymene)(_a–b)Cl]Cl (5a: N N_a = 2,2′‐bipyridine; 5b: N N_b = 4,4′‐dimethyl–2,2′‐bipyridine), [Ru(′′)(_a–b)Cl]Cl (6a: ′N = N_b, _a = 2,2′‐bipyridine; 6b: ′N = N_b, _b = 4,4′‐dimethyl‐2,2′‐bipyridine; 7a: ′N = N_d, _a = 2,2′‐bipyridine; 7b: ′N = N_d, _b = 4,4′‐dimethyl‐2,2′‐bipyridine; 8a: ′N = N_p, _a = 2,2′‐bipyridine; 8b: ′N = N_p, _b = 4,4′‐dimethyl‐2,2′‐bipyridine) and [Ru(′′)(_a)Cl]BF₄ (9a: ′N = N_b; _a = 2,2′‐bipyridine) were synthesized from the corresponding [RuCl₂(p‐cymene)]₂ dimer, ′′ and _a–b ligands. The compounds were characterized by elemental analysis, IR and NMR. Complex 9a was studied by X‐ray diffraction, confirming its cationic‐mononuclear [RuCl(_bb)(_a)]⁺ nature. The synthesized Ru(II) complexes (1–8) were employed as catalysts for the transfer hydrogenation of ketones to secondary alcohols in the presence of KOH using 2‐propanol as a hydrogen source at 82°C. The rates of the transfer hydrogenation reactions strongly depended on the type of and ancillary ligands. Copyright © 2012 John Wiley & Sons, Ltd.     

Broadband circular polarizer based on high-contrast gratings

A circular polarizer, which is composed of periodic and two-dimensional dielectric high-contrast gratings, is designed theoretically such that a unity conversion efficiency is achieved at λ(0)=1.55 μm. The operation is obtained by the achievement of the simultaneous unity transmission of transverse magnetic and transverse electric waves with a phase difference of π/2, meaning that an optimized geometrical anisotropy is accomplished. By the utilization of the rigorous coupled-wave analysis and finite-difference time-domain methods, it is shown that a percent bandwidth of ～50% can be achieved when the operation bandwidth is defined as the wavelengths for which the conversion efficiency exceeds 0.9.     

Thermal and kinetic analysis of uranium salts

The thermal decomposition kinetics of UO₂C₂O₄·3H₂O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO₂C₂O₄·3H₂O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (??H ^*, ??S ^*, and ??G ^*) were calculated.     

Fluorescent sensing platform for low-cost detection of Cu2+ by coumarin derivative: DFT calculation and practical application in herbal and black tea samples

A fluorogenic probe based on a coumarin-derivative for Cu²⁺ sensing in CH₃CN/H₂O media (v/v, 95/5, 5.0 μM) was developed and applied in real samples. 3-(4-chlorophenyl)-6,7-dihydroxy-coumarin (MCPC) probe was obtained by synthetic methodologies and identified by spectral techniques. The probe MCPC showed remarkable changes with a “turn-off” fluorogenic sensing approach for the monitoring of Cu²⁺ at 456 nm under an excitation wavelength of 366 nm. The response time of the probe MCPC was founded as only 1 min. The detection limit of the probe MCPC was recorded to be 1.47 nM. The binding constant and possible stoichiometric ratio (1:1) values were determined by Benesi-Hildebrand and Job’s plot systems, respectively. The mechanism of the probe MCPC with Cu²⁺ was further confirmed by ESI-MS and FT-IR analyses, as well as supported by theoretical calculations. Furthermore, the probe MCPC was successfully employed for the practical applications to sense Cu²⁺ in different herbal and black tea samples. The proposed sensing method was also verified by ICP-OES method.