A Quest for (sila)0-4cyclopentasilylenes and their Arduengo Analogs by DFT

Silicon - Following our interest in exotic silylenes, here we compare and contrast 20 novel five-membered cyclic silylenes, including saturated (sila)0–4 cyclopentasilylenes (1–10) and...     

Kinetic study of radical polymerization. II. Solid‐state bulk polymerization of sodium methacrylate by differential scanning calorimetry

The solid‐state radical polymerization of sodium methacrylate was investigated. It was initiated by azobisisobutyronitrile, which was used as a radical initiator. Differential scanning calorimetry (DSC) was used to observe the endothermic and exothermic transitions during the polymerization reaction. Structural studies were performed with the DSC thermograms and Fourier transform infrared and ultraviolet–visible spectra, and all of the results confirmed the progress of the reaction. The obtained data revealed that the polymerization reaction proceeded completely with a 100% conversion. ΔH of this reaction was calculated with various amounts of the initiator, and the peak temperatures were determined at different heating rates. The activation energy (19.7 kcal mol^?1) was also obtained by the Kissinger method for this type of solid polymerization reaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1648–1654, 2003     

A novel triple notch‐bands ultra wide‐band band‐pass filters using parallel multi‐mode resonators and CSRRs

This article discusses a technique based on combination of multimode resonators (MMR) and complementary split ring resonators (CSRR) to design multi notch‐bands ultra wide‐band (UWB) band‐pass filters (BPF). The proposed structure consists of two parallel multimode resonators, resulting in a dual notch‐band UWB BPF, integrated with a single cell of CSRR to realize the third notch‐band. The mechanism of realizing the notch‐bands is mathematically presented and a triple notch‐bands UWB BPF is designed, simulated and fabricated. The overall size of the proposed filter is reported to be around 36 × 7.7 mm² where a size reduction of around 35% is demonstrated in comparison to the conventional filter. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:375–381, 2014.     

Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage (Γ) and charge transfer rate constant (k_s) of Fe(III)P immobilized on MWCNTs were 7.68 × 10⁻⁹ mol cm⁻² and 1.8 s⁻¹, respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO₃⁻, IO₃⁻ and BrO₃⁻ in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 × 10³, 7.4 × 10³ and 4.8 × 10² M⁻¹ s⁻¹, respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 μM, 2 μM to 1 mM, 8.4 nA/μM, 0.6 μM, 2 μM to 0.15 mM, 11 nA/μM, and 2.5 μM, 10 μM to 4 mM and 1.5 nA/μM, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical application of the Fe(III)P-MWCNTs-modified electrode as an amperometric sensor for chlorate, iodate and bromate detections.     

Estimating the scattering distribution of the received signals in multipath fading channels

This paper presents a novel approach for estimating the distribution of the incoming waves at the mobile unit antenna, i.e. the scattering distribution, in a typical micro-cellular system. This estimate is vital in determining many system parameters of interest as well as designing unbiased estimators for the velocity of mobile units in micro-cellular systems. The proposed approach deploys the zero-crossing rates of the quadrature components and the instantaneous frequency of the received signal at the mobile unit to estimate the scattering distribution. We also propose a new model for simulating multipath fading channels with non-isotropic scattering. We use the channel simulator to evaluate the performance of the proposed estimator for the scattering distribution. Simulation results show that proposed estimator exhibits small bias and root mean square error.     

Green synthesis and characterization of RGO/Cu nanocomposites as photocatalytic degradation of organic pollutants in waste-water

Recently, nanocomposite photocatalysts based on semiconductors have attracted much attention due to their suitable bandgap. Combination of tow of several semiconductors can slow down the electron-hole recombination. In this regard, we have depicted an eco-friendly and green fabrication technique to synthesize RGO/Cu nanocomposite by the reduction of graphene oxide and Cu²⁺ ion utilizing spearmint extract as a reductant and capping agent. The sample was identified by FTIR, XRD, FESEM, EDS, HRTEM, and CV. The results of photocatalytic performance revealed that RGO/Cu is an efficient catalyst for degrading organic pollutants. This compound can eliminate Rhodamine B (RhB) and Methylene blue (MB) 91.0% and 72.0%, respectively.     

Zinc oxide nanoparticles: solvent-free synthesis,characterization and application as heterogeneous nanocatalyst for photodegradation of dye from aqueous phase

In present study, for the first time, ZnO nanoparticles have been synthesized via a simple, novel, solvent and template free solid-state thermal decomposition of the mixed Zn(NO₃)·6H₂O and cochineal powders as a novel starting reagent at 600?°C for 3 h. The as-prepared product was analyzed by XRD, EDS, SEM, TEM, FT-IR and DRS. Besides, the effect of cochineal powder on the morphology and particle size of ZnO nanoparticles was investigated. The results exhibited that cochineal powder prevents the sintering of nanoparticles and leads to formation of uniform particles. Moreover, the efficiency of ZnO nanoparticles as a photocatalyst for the decolorization of methylene orange (MO) has been evaluated and 90% degradation of MO was obtained after 120 min.     

Investigating correlations between crack width,corrosion level and anchorage capacity

In assessing existing structures, inspection results need to be linked to the effects on load-carrying capacity; to provide such information, this study has investigated the correlation between splitting crack width, corrosion level and anchorage capacity. The study was based on 13 reinforced concrete beams that had been exposed to natural corrosion for 32 years, 11 beams with splitting cracks and 2 without. The crack pattern and widths were documented before undergoing structural testing of anchorage capacity. Thereafter, the reinforcement bars were extracted and their corrosion levels measured using two methods, gravimetric weight loss and 3D scanning. The corrosion level from the weight loss method was approximately twice as large; possible reasons are horizontal or subsurface corrosion pits, and the cleaning method. Further, for the same corrosion level, the specimens in this study had much larger crack widths and slightly lower bond capacity than the artificially corroded tests in the literature; a possible reason is that these specimens had been subjected to combined corrosion and freezing. However, the corrosion level and reduction in bond capacity related to crack width were both lower in the present than in previous studies in the literature. Thus, by formulating a damage indicator from the damage visible in the form of crack widths from artificial test data, the structural capacity is estimated to be on the safe side.