Corrosion behavior of pre-rusted rebars after placement in concrete

This paper presents the results of a preliminary study in which the effect of the initial rusting on the corrosion behavior of rebars embedded in concrete has been investigated. Concrete specimens were made with pre-rusted and rust free rebars of different compositions. Two concrete mixes, one with a sodium chloride content of 2 kg/m³ of concrete and the other without any sodium chloride were used. The reinforced concrete specimens, immersed in potable water and then transferred to 5% NaCl solution, were subjected to corrosion monitoring for a period of 10 months. The test results indicate that the initial rusting does not have an adverse effect on the corrosion resistance of rebars embedded in concrete.     

Improved Optoelectronic Properties of Rapid Thermally Annealed Dilute Nitride GaInNAs Photodetectors

We investigate the optical and electrical characteristics of GaInNAs/GaAs long-wavelength photodiodes grown under varying conditions by molecular beam epitaxy and subjected to postgrowth rapid thermal annealing (RTA) at a series of temperatures. It is found that the device performance of the nonoptimally grown GaInNAs p ⁺–i–n ⁺ structures, with nominal compositions of 10% In and 3.8% N, can be improved significantly by the RTA treatment to match that of optimally grown structures. The optimally annealed devices exhibit overall improvement in optical and electrical characteristics, including increased photoluminescence brightness, reduced density of deep-level traps, reduced series resistance resulting from the GaAs/GaInNAs heterointerface, lower dark current, and significantly lower background doping density, all of which can be attributed to the reduced structural disorder in the GaInNAs alloy.     

Temperature dependence of electron saturation velocity in GaAs

Electron saturation velocity is determined from the space charge resistance R/sub c/ and microwave impedance Z/sub d/ of GaAs IMPATT diodes under linear conditions. Comparison between experimental measurement and theory is used in a large frequency bandwidth (2-18 GHz) at different temperatures (T>     

CMOS RF switched capacitor bandpass filter tuned by ring VCO

A new RF switched capacitor bandpass filter and its command circuit made up of a ring voltage controlled oscillator with ‘XOR’ gates are proposed. Implemented in a standard CMOS technology, this circuit is intended to be used in a subset of professional mobile phone applications [380–520 MHz]. Experiments carried out on a prototype show a tunable center frequency range of 260 MHz [240–500 MHz], with a quality factor that can be as high as 300.     

Substitutional Atom Influence on the Electronic and Transport Properties of Mn4Si7

Mn₄Si₇ has been substituted with the following elements: Cu, Fe, Re and Cr on the Mn site, and Al, B, Ge, Sn, Ga, In, Na and Tl on the Si site. The Seebeck coefficient, electrical conductivity and power factor of the substitutional alloys have been evaluated by using density functional theory calculations, and the temperature dependence of the electronic transport properties has been investigated at different charge carrier concentrations by solving the semi-classical Boltzmann transport equation. We show that the substitution of Cu for Mn worsens the thermoelectric properties, while that with Fe appears the?most efficient for increasing the power factor. For In and Tl substitutions, the Seebeck coefficient is increased due to the high d-states contribution in the density of states at the Fermi level. Although the power factor is limited by a poor electrical conductivity, Mn₃₂Si₅₅Tl could exhibit a good figure of merit provided that the amount of Tl atoms is low (at most 1 at.%) and the charge carrier concentration is not too high (around 10²⁰ cm^?3).     

Metabolic Syndrome: Updates on Pathophysiology and Management in 2021

Metabolic syndrome (MetS) forms a cluster of metabolic dysregulations including insulin resistance, atherogenic dyslipidemia, central obesity, and hypertension. The pathogenesis of MetS encompasses multiple genetic and acquired entities that fall under the umbrella of insulin resistance and chronic low-grade inflammation. If left untreated, MetS is significantly associated with an increased risk of developing diabetes and cardiovascular diseases (CVDs). Given that CVDs constitute by far the leading cause of morbidity and mortality worldwide, it has become essential to investigate the role played by MetS in this context to reduce the heavy burden of the disease. As such, and while MetS relatively constitutes a novel clinical entity, the extent of research about the disease has been exponentially growing in the past few decades. However, many aspects of this clinical entity are still not completely understood, and many questions remain unanswered to date. In this review, we provide a historical background and highlight the epidemiology of MetS. We also discuss the current and latest knowledge about the histopathology and pathophysiology of the disease. Finally, we summarize the most recent updates about the management and the prevention of this clinical syndrome.     

Effect of Adding Transition Metals to Copper on the Dehydrogenation Reaction of Ethanol

The present work aims to investigate the effect adding Ag, Co, Ni, Cd and Pt to copper on ethanol dehydrogenation. The catalysts synthesized by deposition–precipitation method were characterized using various physicochemical methods such as N₂ adsorption–desorption, TPR, SEM–EDX, XRD, XPS and TGA–DSC-MS. Catalytic evaluation results revealed that the predominant product of the reaction was acetaldehyde. Monometallic copper or mixed with Cd, Ag or Co show good catalytic performances. Adding nickel to copper improves the process conversion but reduces acetaldehyde selectivity, giving rise to methane in produced hydrogen. Pt-Cu/SiO₂ catalyst guides the reaction towards diethyl ether. Time on stream tests performed during 12 h at 260 °C, showed that adding Cd to Cu enhances its stability by over 30% of conversion, this is explained by the reduction of copper crystallites sintering, which makes Cd-Cu/SiO₂ a promising catalyst for the production of acetaldehyde by ethanol dehydrogenation.

Graphic Abstract

     

Synthesis of Co3O4 @ Organo/Polymeric Bentonite Structures as Environmental Photocatalysts and Antibacterial Agents for Enhanced Removal of Methyl Parathion and Pathogenic Bacteria

Two green nanocomposites of Co₃O₄ decorated CTAB/bentonite (Co@CT/BE) and chitosan/bentonite (Co@CH/BE) were synthesized as enhanced and environmental photocatalysts and antibacterial agents. As photocatalysts, the products were applied in the effective oxidation of toxic methyl parathion pesticide (MP) in wastewater under a visible light source. The application of Co@CH/BE (0.02 g) resulted in the complete oxidation of MP (50 mg/L) after 40 min and complete mineralization after 60 min. while the complete oxidation and mineralization of MP (50 mg/L) by Co@CT/BE was recognized after 75 min and 100 min, respectively. The Co@CH/BE composite is of higher activity than Co@CT/BE and can cause complete oxidation for MP at high concentrations up to 100 mg/L after 75 min. The oxidation pathway was illustrated considering the existence of the hydroxyl radicals as the active oxidizing species and the identified secondary organic compounds during the oxidation tests. The detected intermediate converted into end products of CO₂ and inorganic anions of SO₄^?2, NO₃^?, and PO₄^?3 at the final stages of the oxidation processes. As antibacterial agents, the two composites exhibit considerable inhabitation zones of about 20 mm against both the Gram-positive Staphylococcus aureus and Gram-negative bacterium Vibrio Sp. The synthetic Co@CH/BE showed the best antibacterial properties with 200 μg/mL as minimum inhibitory against Staphylococcus aureus.

     

Correction to: Synthesis of Co3O4 @ Organo/Polymeric Bentonite Structures as Environmental Photocatalysts and Antibacterial Agents for Enhanced Removal of Methyl Parathion and Pathogenic Bacteria

Journal of Inorganic and Organometallic Polymers and Materials -     

Exact quadratic load flow algorithm using network reduction and P - V data

An AC load flow computation applicable by computers with small core sizes is presented. It uses network reduction to eliminate all P-Q buses at their nominal voltages, retaining only P-V buses. The P-V bus data, as a set of nonlinear quadratic equations, are implemented in an iterative technique to restore new values for P-Q bus voltages. Then, the algorithm is repeated by using the restored voltages as nominal values until the final solution is obtained.