CFD Modeling of Micromixing and Velocity Distribution in a 1.7‐MHz Tubular Sonoreactor

The effect of high‐frequency (1.7 MHz) ultrasound waves on the mixing rate in a new continuous tubular sonoreactor was investigated by CFD modeling. Modeling of piezoelectric transducer (PZT) vibrations was done based on the dynamic mesh model. Results indicate that the acoustic streams were in the direction of wave propagation and their maximum velocity near the PZT surface agreed well with experimental measurements. The micromixing efficiency of the sonoreactor was studied by adopting the Villermaux/Dushman reaction in the modeling. Comparison of the calculated relative segregation index from modeling results with experimental data revealed reasonable accordance.     

A wideband beam shaping reflector antenna using model predictive control

A novel method based on model predictive control (MPC) is presented for synthesis and optimization of a wide band reflector antenna with cosecant squared and flat‐topped radiation patterns. The proposed system is a doubly curved reflector antenna with nonlinear dynamic equation. This article investigates design and optimization of a double ridged horn reflector antenna operating within the frequency range of 8 to 18 GHz. In order to synthesize the proposed reflector antenna, MPC is used to achieve the desired radiation cosecant pattern. This method utilizes system model and tries to find the best control effort for minimizing the cost function by predicting the future behavior. The system differential equation is comprised of first and second order derivatives, so MPC can be a good solution for synthesis of a doubly reflector antenna. MPC optimizer operates based on state space model, so the proposed system is linearized in the operating range. Maximum error, the average error and side lobe level of this method for the radiation pattern of the proposed wideband antenna respectively are 1.4, 0.9, and ?20 dB. Simulation results of the radiation pattern in CST and HFSS software show that the proposed reflector antenna can be used in broadband surveillance radar systems.     

Synthesis ZnO nanoparticles from a new Zinc(II) coordination polymer precursor

A new zinc(II) nitrite coordination polymer, [Zn(3-bpdh)(NO₂)₂]_n (1), 3-bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene} was prepared and characterized by elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction and is one-dimensional polymer with coordination environment of distorted octahedral, ZnN₂O₄. Thermal decomposition of this precursor in oleic acid at 240 °C under air atmosphere results in the formation of nanoparticles of ZnO. The nano-materials were characterized by scanning electron microscopy, X-ray powder diffraction (XRD) and IR spectroscopy. The thermal stability of nano-structure ZnO was studied by thermal gravimetric and differential thermal analyses and showed that there is no reportable loss of weight in the TGA curves that proves the existence of zinc(II) oxide. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nanoscale materials.     

Electrocatalytic oxidation of ascorbic acid at a 2,2′-(1,8-octanediylbisnitriloethylidine)-bis-hydroquinone modified carbon paste electrode

Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical behavior of ascorbic acid at a carbon paste electrode modified with 2,2′-(1,8-octanediylbisnitriloethylidine)-bis-hydroquinone (1,8-OBNEBHQ). The modified carbon paste electrode showed high electrocatalytic activity toward ascorbic acid; the current was enhanced significantly relative to the situation prevailing when an unmodified carbon paste electrode was used. The electrocatalytic process was highly dependent on the pH of the supporting electrolyte. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, for electron transfer between 1,8-OBNEBHQ and carbon paste electrode were calculated as 20.2 ± 0.5 s⁻¹ and 0.47, respectively. Using differential pulse voltammetry, the calibration curves for AA were obtained over the range of 5–30 and 40–1,500 μM, respectively. The detection limit (kσ, k = 2) was 0.6 μM. With good selectivity and sensitivity, the present method provides a simple method for selective detection of ascorbic acid in biological samples.     

Macro- and micromixing in a novel sonochemical reactor using high frequency ultrasound

This paper deals with the influence of ultrasound on macro- and micromixing in a new developed sonochemical reactor. Unprecedented piezoelectric transducer arrangement with a high frequency of 1.7 MHz has been used in this novel reactor. Macromixing quality has been investigated visually and the Dushman reaction (iodide-iodate) coupled with a neutralization reaction have been examined in order to characterize micromixing quality. In addition, the effect of liquid viscosity on the segregation index has been studied. The results show that this new developed reactor can establish reasonable macro- and micromixing inside the reactor. Moreover, the performance of this reactor has been compared with a stirred tank reactor equipped with a Rushton turbine impeller. It is found that with the same input electrical power, the obtained segregation index for stirred tank reactor is approximately 10% more than proposed new ultrasound reactor, which means the sonoreactor works more efficiently.     

In vivo evidence that the stromelysin-3 metalloproteinase contributes in a paracrine manner to epithelial cell malignancy

Stromelysin-3 (ST3; Basset, P., J.P. Bellocq, C. Wolf, I. Stoll, P. Hutin, J.M. Limacher, O.L. Podhajcer, M.P. Chenard, M.C. Rio, P. Chambon. 1990. Nature. 348:699-704) is a matrix metalloproteinase (MMP) expressed in mesenchymal cells located close to epithelial cells, during physiological and pathological tissue remodeling processes. In human carcinomas, high ST3 levels are associated with a poor clinical outcome, suggesting that ST3 plays a role during malignant processes. In this study we report the ST3 gene inactivation by homologous recombination. Although ST3 null mice (ST3-/-) were fertile and did not exhibit obvious alterations in appearance and behavior, the lack of ST3 altered malignant processes. Thus, the suppression of ST3 results in a decreased 7, 12-dimethylbenzanthracene-induced tumorigenesis in ST3-/- mice. Moreover, ST3-/- fibroblasts have lost the capacity to promote implantation of MCF7 human malignant epithelial cells in nude mice (P < 0.008). Finally, we show that this ST3 paracrine function requires extracellular matrix (ECM)-associated growth factors. Altogether, these findings give evidence that ST3 promotes, in a paracrine manner, homing of malignant epithelial cells, a key process for both primary tumors and metastases. Therefore, ST3 represents an appropriate target for specific MMP inhibitor(s) in future therapeutical approaches directed against the stromal compartment of human carcinomas.     

Fractional Order Synchronous Reluctance Motor: Analysis,Chaos Control and FPGA Implementation

This paper deals with the dynamical analysis and chaos control in a fractional order synchronous reluctance motor (FOSyncRM). Equilibrium points, characteristic equations and Eigen values of both commensurate and incommensurate FOSyncRM are presented. finite‐time Lyapunov exponents of the FOSyncRM system for fixed and varied parameters are investigated along with the bifurcation plots. Fractional order bifurcation plots are derived to show that the system shows more complex chaotic oscillations in fractional order. Chaos control in the FOSyncRM system is achieved using adaptive sliding mode controllers and the entire control algorithm is implemented in FPGA.     

A New Metal–Organic ZnII Supramolecular Assembled via Hydrogen Bonds and N···N Interactions as a New Precursor for Preparation Zinc(II) Oxide Nanoparticles, Thermal, Spectroscopic and Structural Studies

A new 1D supramolecular involving two different ligands, {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O (GB = 2-guanidinobenzimidazole and bpe = 1,2-bis(4-pyridyl)ethylene, has been synthesised, characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy. The thermal stability of compound {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O was studied by thermal gravimetric and differential thermal analyses. The single crystal X-ray analysis shows that the complex is a one-dimensional polymer involving macrocycle rings as a result of non-covalent bridging bpe ligands via N–H···N and N···N interactions, N–H···bpe···bpe···H–N, with the basic repeating {[Zn(GB)₂](μ-bpe)₃}(ClO₄)₂·H₂O units and by connecting [Zn(GB)₂]²⁺ nodes. ZnO nanoparticles were obtained by calcination of compound {[Zn(GB)₂]·(μ-bpe)₃} _n (ClO₄)_2n ·nH₂O at 500 °C in air. The nanoparticles were characterized by X-ray diffraction and scanning electron microscopy.     

Synthesis and Characterization of Zinc(II) Oxide Nanoparticles by Thermal Decomposition of Two Zinc(II) Nitrite Coordination Polymer Precursors

Two zinc(II) coordination polymers, {[Zn(3-bpdb)(NO₂)]·0.5H₂O} _n (1) and [Zn(4-bpdb)(NO₂)₂] _n (2), 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene and 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene}, have been synthesized and characterized by elemental analyses and IR spectroscopy. Nanoparticles of zinc(II) oxide have been prepared by thermolyses of two different zinc(II) coordination polymers, 1–2. The nano-materials were characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. The thermal stability of ZnO nano-particles was studied by thermal gravimetric and differential thermal analysis and showed that there is no loss of weight, which indicates that the products were zinc(II) oxide. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nanoscale materials.