Synthesis of new phosphorus ylides: Spectroscopic and X‐ray structural studies

Stable phosphoranes, Ar₃P = CHCOR (R = C₆H₅, C₆H₄NO₂, C₆H₄OCH₃, CH₃, OCH₂C₆H₅; Ar = p‐tolyl or phenyl), have been C‐acylated by acetic anhydride to obtain new types of phosphorus ylides. Synthesis and characterization of six phosphorus ylides of the type Ar₃PC(COCH₃)(COR) are reported. The reaction of {(p‐tolyl)₃PCHCOC₆H₅} ( I ), {(p‐ tolyl)₃PCHCOC₆H₄NO₂} ( II ), {Ph₃PCHCOC₆H₄NO₂} ( III ), {Ph₃PCHCOC₆H₄OCH₃} ( IV ), {(p‐tolyl)₃PCHCOCH₃} ( V ), and {Ph₃PCHCOOCH₂C₆H₅} ( VI ) with acetic anhydride in dry chloroform as solvent gives (p‐tolyl)₃PC(COMe)(COC₆H₅), α‐acetyl‐α‐benzoylmethy‐lenetriphenylphosphorane ( 1 ), {(p‐tolyl)₃PC(COMe) (COC₆H₄NO₂)} ( 2 ), {Ph₃PC(COMe)(COC₆H₄NO₂)} ( 3 ), {Ph₃PC(COMe)(COC₆H₄OCH₃)} ( 4 ), {(p‐tolyl)₃ PC(COCH₃)₂} ( 5 ), and {Ph₃PC(COMe)(COOCH₂ C₆H₅)} ( 6 ). Single crystal X‐ray analyses for ylides 2 , 5 , and 6 reveal the monoclinic ( 2, 5 ) and triclinic ( 6 ) crystal systems. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. The geometries of these compounds have been investigated using density functional theory (DFT). In addition, electronic parameters of these compounds such as HOMO and LUMO energy, Mulliken partial charge, and dipole moment were obtained. In this paper, the reactivity of these ylides is discussed in regard to the aforementioned data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:475–485, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20633     

Effects of inclined magnetic field on mixed convection in a nanofluid filled double lid-driven cavity with volumetric heat generation or absorption using finite element method

A computational analysis has been performed on mixed convection in a double sided lid-driven cavity in the presence of volumetric heat generation or absorption. Effects of inclined magnetic field are also studied. The governing parameters are solved via Galerkin weighted residual finite element method in space and the Crank–Nicolson in time. Governing parameters are nanoparticle volume fraction (0.0?≤???≤?0.04), Richardson number (0.01?≤?Ri?≤?10), internal heat generation or absorption parameter $(?10\le q\le 10),$ inclination angle of magnetic field (0°?≤?γ?≤?90°) and Hartmann number (0?≤?Ha?≤?100). It is observed that the highest heat transfer is obtained in case of the maximum value of heat absorption. As a further finding, heat transfer decreases with increasing of Hartmann number and increases with increasing of nanoparticle volume fraction.     

X-ray and Theoretical Studies of 2-((5-Amino-1,3,4-thiadiazol-2-yl)thio)-1-phenylethanone

The crystal structure of 2-((5-amino-1,3,4-thiadiazol-2-yl)thio)-1-phenylethanone was determined by X-ray diffraction method. The compound crystallizes in orthorhombic crystal system, sp. gr. Pbca. The atoms that constitute thiadiazole and phenyl rings do not form any significant deviation from the ring planes. Compound has two intermolecular N–H···N hydrogen bonds and one C–H···π interaction. Using DFT/B3LYP method with 6-31G(d), 6-311G(d), 6-311G(d, p), and 6-311++G(d, p) basis sets, the molecular geometry of the compound was optimised. Bond lenghts, bond angles, torsion angles, dihedral angles, and HOMO–LUMO were calculated from the optimised geometry of the compound. The results obtained by X-ray diffraction method were compared with the results obtained through four different basis sets. Total energy of the molecule was calculated for four different basis sets.     

非均相催化臭氧氧化反应机制

臭氧催化氧化作为高级氧化技术是目前水处理领域研究的热点,其中非均相臭氧催化氧化技术因其氧化能力强、降低臭氧投加量特别是能显著提高有机物矿化率等优点而备受关注。非均相催化臭氧氧化领域不断研究新的催化剂,但是其反应过程及机制更加复杂。催化臭氧氧化的性能很大程度上取决于催化剂及其表面性质。污染物在催化剂表面形成络合物,或者臭氧在催化剂表面分解产生不同的含氧物种如表面氧原子、过氧化物和羟基自由基等。本文评述了非均相臭氧催化氧化反应中存在的多种机理,主要是自由基理论、氧空位理论、表面原子氧理论、表面络合物理论和臭氧直接氧化理论。催化剂表面的羟基基团是主要的催化活性中心,本文探讨了表面羟基基团催化反应机制,得出催化剂表面性质决定其表面活性位点的特性及含量,对诱导臭氧分解产生含氧活性物种起了关键作用;概述了催化剂改性后的结构形态、比表面积及其性能和作用机制;并讨论了非均相臭氧催化氧化反应催化剂未来的发展趋势,为催化臭氧氧化污水处理技术提供了理论参考。     

Effect of Calcium Ion Concentration on Small Molecule Desorption from Alginate Beads

Spherical alginate beads were prepared by ionotropic gelation of sodium alginate through the use of calcium ions. Pyranine (Py) was added to the alginate solution as a small molecule probe for fluorescence studies. Desorption of Py in water from the alginate beads cross-linked with calcium ions was studied by using the steady state fluorescence technique. The fluorescence emission intensity (I) from Py was monitored during the desorption process at 512 nm using the time drive mode of the spectrofluorometer. The increase in I was attributed to Py release from the beads. The Fickian diffusion model was used to calculate the desorption coefficients, D_, which were found to be increased up to 3% (w/v) CaCl₂ concentration in the beads, and then decreased with a further increase of CaCl₂ content. On the other hand, the encapsulation efficiency of Py in the calcium alginate beads presented the reverse behavior compared to D. It was observed that, when the content of CaCl₂ was increased, the incubation time, t_0, for the start of desorption increased.     

A new high-performance CMOS fully differential second-generation current conveyor with application example of biquad filter realisation

In this article, a new complementary metal oxide semiconductor (CMOS) high-performance fully differential second-generation current conveyor (FDCCII) implementation is proposed. The presented FDCCII provides high-output impedance at terminals Z+ and Z?, good linearity and excellent output–input current gain accuracy. Also, the proposed FDCCII circuit operates at a supply voltage of ±1.3 V. The applications of the FDCCII to realise voltage-mode multifunction filters are given. Simulations are performed using TSMC CMOS 0.35-μm technology to verify theoretical results.     

New current–mode special function continuous-time active filters employing only OTAs and OPAMPs

This paper reports three current mode second order filters, each of which realizes a specific function without any external passive elements. These filters realize low-pass notch (LPN), high-pass notch (HPN) and all-pass (AP) functions. Two OPAMPs, a double output OTA and a single output OTA are employed for each circuit. The filter structures can be easily cascaded since they have high output impedances. This property is especially useful for achieving high-order filters using these LPN and HPN filters as building blocks. The presented theory is verified with macro models in SPICE simulations and, using the SPICE parameters of the layout technology, post layout simulations are carried out, with parasitics extracted from the layouts of the filter chips.     

Auction-Based Throughput Maximization in Cognitive Radio Networks Under Interference Constraint

Cognitive radio is an emerging technique to improve the utilization of radio frequency spectrum in wireless communication networks. That is, spectrum efficiency can be increased significantly by giving opportunistic access of the frequency bands to a group of cognitive users to whom the band has not been licensed. In this paper, as a cross layer application (MAC and physical layers) of graph theory, we consider the problem of throughput maximization of spectrum allocation in cognitive radio networks under interference constraint. We propose a novel auction-based channel allocation mechanism which tries to maximize both total and primary users’ utilities while satisfying signal to interference ratio constraint on primary receivers so that transmitted packets will be successfully received, without controlling secondary user powers. For comparison we discuss a greedy algorithm as well, however, one that does not handle interference issue. In order to compare results of proposed and greedy algorithms, we propose net throughput by taking into account outage probability of primary receiver. Simulation results show that exposing higher SINR (outage) threshold not only decreases total gain and primary users’ utilities but also worsens channel distribution performance. On the other hand adding auction mechanism significantly increases total gain throughput and primary user’ s utility. Particularly, up to SINR threshold values of 20 dBs, auction provides outstanding performance and proposed algorithm has total throughput results close to those of the greedy one even though no interference constraint is applied in the greedy algorithm. Another noticeable point of simulation results is crossover of net throughputs of proposed and greedy algorithms at a SINR threshold level after which results of ABSA-UNIC and NASA-UNIC are much better. This clearly shows superiority of proposed mechanism.     

Hybrid control algorithm to improve both stable impedance range and transparency in haptic devices

An ideal haptic device should transmit a wide range of stable impedances with maximum transparency. When using active actuators, transparency improvement algorithms tend to decrease the range of attainable impedances. Passive actuators can transmit high impedances stably, but are not sufficient alone for transparency. In this study, a hybrid force control algorithm employing active and passive actuators was developed to improve the stable impedance range and transparency in haptic devices. A new transparency-Z-width plot is proposed as a way to evaluate the stable impedance range and transparency together. The hybrid control algorithm uses parameters to share the torque demand between two actuators with smooth transition. These parameters were determined and an artificial neural network (ANN) was used to extend them to the entire achievable impedance range. The algorithm was tested experimentally on a 1-DOF haptic device. The transparency experiments employed an excitation motor located at the user side of the device to evaluate various algorithms in time and frequency domains. Results showed that the proposed hybrid control algorithm enables simulation of higher range of impedances with higher transparency than the conventional algorithms.