Simplified Procedure For Synthesis Research Articles

Fractional-order sliding mode control with a predefined-time observer for VTVL reusable launch vehicles under actuator faults and saturation constraints

For vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) with actuator faults and saturation constraints, this paper presents a composite control system including a high-order predefined-time extended state observer (HO-PTESO), a predefined-time anti-saturation compensator (PTASC), and a fractional-order practical predefined-time sliding mode control law (FO-PPTSMC). The HO-PTESO accomplishes the precise estimation of disturbance in a time interval predefined by only one design parameter, resulting in a simple and weakly conservative parameter tuning process for temporal demands. Moreover, the peaking value problem is well addressed. The PTASC serves to ensure the stability of the saturated system. Auxiliary variables of the PTASC remain bounded during the saturation process and vanish within the predefined time interval after the saturation process ends, avoiding long-term impacts on the attitude tracking that are common concerns for existing ASCs. Using the estimated disturbance, the FO-PPTSMC enforces unsaturated system states to a predefined residual set of the origin in a chattering-alleviated manner within the predefined time interval. Two parameters respectively predefine the convergence range and time, resulting in a considerably simplified synthesis procedure. Ultimately, numerical simulations on the double integrator system and VTVL RLV model validate the efficiency of the proposed control system.

A facile synthesis of mono-dispersed, spherical and mesoporous bioactive glass nanoparticles for biomedical applications

Bioactive glasses (BG) have become a popular class of biomaterials for a range of medical applications due to their enhanced dissolution rate, cell internalization capability and ionic dissolution products with therapeutic benefits. Here, we introduce, for the first time, a simplified synthesis procedure in order to create nanoparticles with uniform, spherical and mesoporous BG structure with a ternary composition of SiO2-CaO-P2O5. The hydroxyapatite forming ability is also evaluated to confirm the bioactivity. Doxorubicin, a model drug, is loaded within BG nanoparticles with an encapsulation efficiency was 35%. Cytotoxicity evaluations confirmed the non-toxic nature of the nanoparticles when exposed to MG63 cell line. Overall, results suggest the diverse orthopedic and dental application of mesoporous bioactive glass (MBG) nanoparticles.

Rational design of a low-cost, durable and efficient bifunctional oxygen electrode for rechargeable metal-air batteries

Economic viability of the electrochemical stationary storage of electricity produced by intermittent renewables is the bottleneck for a transition towards a fully green energy landscape. Abundance, inexpensiveness and facile preparation for novel active materials and performant electrodes facilitate scale-up and costs lowering upon their further integration into already existing manufacturing processes. Herein, we demonstrate the relevance of a low-cost approach and a design strategy for the preparation of an efficient material for bifunctional O2 electrocatalysis, and detail its further embedding into a gas diffusion electrode (GDE) architecture tested under relevant load conditions for rechargeable zinc-air battery application. A plain preparation of the active material combines α-MnO2, obtained from a simplified synthesis procedure, commercially available carbon black and Ni/NiO nanoparticles. A systematic optimization of the surface concentration of the most active catalytic ensemble and synergetic effects for both oxygen reduction and oxygen evolution reactions, taken separately, shapes the design of a bifunctional electrocatalyst. Performances of GDEs surpass the vast majority of the previous concepts, with stable overpotentials (ca. 0.35 V for each reaction, 55 % energy efficiency) over 400 h at 20 mAh∙cm−2 load cycles (for both charge and discharge), bridging the gap between promising electrocatalyst material and realistic functional electrode.

Surface chemistry and structure evaluation of Mg/Al and Mg/Fe LDH derived from magnesite and dolomite in comparison to LDH obtained from chemicals

Multiple attempts have been made to lower the cost of the adsorbents for the wastewater treatment. This work investigated the possibility of obtaining Mg/Al and Mg/Fe LDH without excessive use of chemical reagents, by replacing them with cheaper substrates. Magnesite and dolomite were used as Mg-sources in a facile co-precipitation synthesis at room temperature. Several variants of LDHs were studied regarding their chemical composition, MII/MIII molar ratio and the synthesis time. Their comprehensive characterization was provided and compared to the reference materials obtained from chemical reagents. Depending on the molar ratio the reference samples exhibited a clear shift of the XRD basal reflections, and different species of interlayer carbonates were identified by spectroscopic methods. The LDHs derived from minerals had similar structural features as compared to the reference samples. However, the synthesis of mineral-based LDHs resulted in the formation of additional phases. The formation of LDH from minerals with a molar ratio higher than 2:1 was impossible in the applied conditions. The 2 h ageing time was enough to enable the LDH formation. The transformation procedure of magnesite and dolomite to LDH via simplified synthesis procedure may significantly reduce the final cost of the adsorbents by excluding expensive chemical reagents.

Anticorrosion Behavior of Zeolite Coatings Obtained by In Situ Crystallization: A Critical Review.

Zeolites are crystalline nanoporous aluminosilicates. Thanks to their intrinsically nanoporous structure they are widely used as molecular sieves, for exchanging ions, or, also thanks to the high surface area of these structures, for catalytic applications. Furthermore, thanks to their thermal and chemical stability, in recent years zeolite coatings have been evaluated for application as anti-corrosion coatings. The non-toxicity of this class of coatings makes it possible that they will be an environmentally friendly alternative to conventional chromate-based coatings. This article provides a brief review of the anti-corrosion performance of zeolite coatings, applied by direct synthesis technique to several metals and alloys, as discussed in the literature. After a short description of the microstructure and properties of zeolites, the discussion addresses the research activities related to this topic, as reported in the literature. Comparative analysis of literature results supported the dry-gel conversion method as a promising approach that combines a simplified synthesis procedure with anti-corrosion coating performance. Based on these considerations, an evaluation of future trends is discussed along with the final remarks.

Recent Progress and Challenges of Micro‐/Nanostructured Transition Metal Carbonate Anodes for Lithium Ion Batteries

Lithium ion batteries (LIBs) have attracted tremendous interest in electric vehicles and smart grids, due to their inherent advantages of being powerful and environmentally benign. However, their performance is presently far from meeting the continually increasing demands for long‐durance mileage and long lifespan. High‐performance anodes with high specific capacity and long cyclability are of great significance to high‐energy/high‐power lithium ion batteries; however, there are still great challenges in advancing new materials beyond commercial graphite, whose capacity is low and limited by the theoretical values (372 mAh g–1). That is why scientists are continually searching for satisfying anode alternatives to graphite. Recent progress has demonstrated that transition metal carbonates (TMCs) are very promising candidates as anode materials for LIBs due to their high specific capacity, decent energy density, and simplified synthesis procedure. In this review, recent reports on TMCs and their derivatives, formulated as MCO3 (M = Mn, Co, and/or Fe, etc.), are systematically summarized. Their corresponding Li+ storage mechanisms are briefly discussed. As concrete examples, nanocrystallization technology and structural modification are represented in detail. Finally, we discuss some challenges for TMCs in LIBs and their perspectives to push energy storage of LIBs to the next‐generation level.

Fully automated preparation of [11C]choline and [18F]fluoromethylcholine using TracerLab synthesis modules and facilitated quality control using analytical HPLC

Modifications of a GE TracerLab FX(C-Pro), which can be implemented for solid-phase [(11)C]methylation are described. The simplified procedure for synthesis of [(11)C]choline uses a single Sep-Pak CM-Light cation-exchange cartridge for both solid-supported reaction and purification. Compared with the commonly used two Sep-Pak method, the low back-pressure of this Sep-Pak enables efficient and reliable production of [(11)C]choline using a TracerLab FX(C-Pro) without requirement for any gas pressure adjustment. Typical radiochemical yields (RCY) are >60%, radiochemical purity (RCP) is 99.9% and levels of residual precursor in the final product, which may inhibit the uptake of [(11)C]choline, are reduced to 1 μg/mL. Similarly, modification of a GE TracerLab FX(FN) is reported which enables gas-phase production of [(18)F]fluoromethylcholine, suitable for pre-clinical use, (in 4-6% RCY and >99.7% RCP) using a related Sep-Pak method. These modifications can be utilized for solid-phase [(11)C]methylation and [(18)F]fluoromethylation of other radiotracers, and allow straightforward switching to other module configurations for solution-phase radiochemistry or loop chemistry. In addition, we report a convenient HPLC ion chromatography method, which can monitor residual precursor and the radiochemical purity of product at the same time, providing highly efficient quality control for routine clinical application. The reported HPLC method is appropriate for analysis of doses of both [(11)C]choline and [(18)F]fluoromethylcholine, and eliminates the need for a GC method to determine residual precursor levels.

Isolation and purification of 3-hydroxy-3-methylglutaryl-coenzyme A by ion-exchange chromatography

For precise determination of the catalytic activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (EC 1.1.1.34), the HMG-CoA employed as substrate must be free of HMG, CoA, and other inhibitors of HMG-CoA reductase activity. The standard purification of HMG-CoA by paper chromatography gives poor resolution of HMG-CoA from CoA and may be accompanied by some decomposition of HMG-CoA. We describe a simplified procedure for synthesis and for isolation from the reaction mixture of homogeneous, high specific activity [3(-14)C]HMG-CoA free of HMG, CoA, or nonpolar contaminants. Isolation of HMG-CoA utilizes ion-exchange chromatography in a gradient of ammonium formate, which is subsequently removed by lyophilization. The methods are proposed for use in the preparation or isolation of HMG0CoA.

A simplified procedure for synthesis of di-[14C]acyl-labeled lecithins.

A simplified procedure for synthesis of 1,2-di-[1'-14C]oleoyl-, 1,2-di-[1'-14C]linoleoyl-, and 1,2-di-[1'-14C]eicosatrienoyl-sn-glycero-3-phosphorylcholine is described. The method involves acylation of the CdCl2 complex of glycerophosphorylcholine with a 14C-labeled fatty acid in the presence of trifluoracetic anhydride and pyridine. The 14C-labeled lecithin is isolated in pure form by preparative thin-layer chromatography and alumina column chromatography in an overall yield of 12-24%. No isomerization or peroxidation of the unsaturated acids was detected.

Simplified method for synthesis of distributed resistance networks

A new distributed-resistance-network geometry is defined, which is suitable for the realisation of a wide variety of networks. An accurate, simplified synthesis procedure, based on a property of the linear fractional transformation and transmission-line concepts, is presented.

Compound Synthesis of Threshold-Logic Network for the Realization of General Boolean Functions

This paper deals with the problem of compound synthesis of threshold-logic network, or of realizing a general Boolean function with a number of threshold-logic elements. Some basic theorems concerning the expression of a general Boolean function as a combination of a number of threshold functions are presented. The general structure of a network of m threshold-logic elements is analyzed in light of the basic theorems and properties of threshold functions. The properties of isobaric threshold functions are discussed and are utilized for compound synthesis. Methods for decomposing a function into a sum or product of unate functions and into a sum or product of threshold functions are developed. A synthesis procedure conforming with the general structure of a network of threshold-logic elements is given. A simplified synthesis procedure, which needs less cut and trial than the original procedure and is, therefore, more practical, is also presented. Some special situations are discussed. Examples are worked out to show the decomposition of functions, and to illustrate the synthesis method.

Notes- A Simplified Procedure for Synthesis of Oleic-1-C14 Acid

Notes- A Simplified Procedure for Synthesis of Oleic-1-C¹⁴ Acid