Selectivity in the acylation of amino-sulphonamides

After the identification of unexpected products formed from methyl dichloro-acetate and an amino-sulphonamide during the attempted synthesis of a derivative of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide, unprecedented selective acylation of the sulphonamido group in sulphanilamide was found to occur when esters of activated carboxylic acids were allowed to condense at 25 °C with the sodium salt of sulphanilamide in methanol. The scope of this reaction was examined both with respect to the amino-sulphonamide and with respect to the ester used as acylating agent. No limitations to the reaction were found among the amino-sulphonamides examined, each of which was acylated exclusively at the sulphonamido group. Methyl dichloro-acetate and methyl tricyloroacetate were effective acylating agents, ethyl dichloro-acetate was less so, and ethyl chloroacetate was ineffective. The mechanisms of the new reaction and of the classical acylation by acyl-pyridinium ions are discussed and compared, and explanations are offered for the contra-selectivity of the two reactions. The infrared spectra of the N-aminoarenesulphonyl-2, 2-dichloroacetamides and N-aminoarenesulphonyl-2, 2, 2-trichloroacetamides made by the new method reveal that in many cases these compounds have a zwitterionic structure in the solid state which is lost in their azo-β-naphthol derivatives.     

Signing avatars: making education more inclusive

Universal Access in the Information Society - In Brazil, there are approximately 9.7 million inhabitants who are deaf or hard of hearing. Moreover, about 30% of the Brazilian deaf community is...     

Analysis of the life of cemented carbide drills with modified surfaces

The performance of cemented carbide cutting tools during machining is influenced not only by the mechanical properties of the coating and substrate but also by the topographies of their surfaces. A tool with good coating and substrate properties but unsuitable topographies may exhibit accelerated wear and, consequently, impaired performance. In this work, drills coated using physical vapor deposition (PVD) were produced with different substrate textures, which in turn generated different coating textures. The surface roughness values of the coated drills were measured together with the residual stress at the interface between substrate and coating. Drilling tests were performed and tool wear was measured during the machining process. Two different tool coatings were studied: TiAlN and TiAlCrSiN. The goal was to study how the characteristics of the substrate and coating (material, surface topography, and residual stress) influence tool life. Tool life experiments were carried out using drilling tests in AISI 1548 steel, which is often used in crankshafts. The primary tool wear mechanism was attrition in all the drills. The main conclusion of this work is that the tool with the lowest roughness and a TiAlCrSiN coating had the best performance in the conditions tested here.     

Scen@rist: an approach for verifying self-adaptive systems using runtime scenarios

Software Quality Journal - Traditional runtime quantitative verification approaches for self-adaptive systems usually rely on the use of state-transition models to describe the system behaviour and...     

Static Recrystallization Kinetics and Crystallographic Texture of Nb-Stabilized Ferritic Stainless Steel Based on Orientation Imaging Microscopy

In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol⁻¹, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554}〈225〉 orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554}〈225〉 component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.

     

Thermoplastic composites based on poly(ethylene 2,6‐naphthalate) and basalt woven fabrics: Static and dynamic mechanical properties

Composites based on poly(ethylene 2,6‐naphthalate) and basalt woven fabrics have been investigated with the aim to develop composites with a minimum service temperature of 100°C. Laminates have been manufactured by using the film‐stacking technique. A very low void content and a good fabric impregnation has been obtained as confirmed by the morphological analysis performed with scanning electron microscopy. Static flexural modulus and strength have been measured at 20, 60, and 100°C and compared with the dynamic mechanical behavior, evaluated from −100 to 220°C. A very good agreement has been detected between static and dynamic tests, proving that the dynamic mechanical analysis can be used to estimate the flexural modulus in a wide temperature range. Poly(ethylene 2,6‐naphthalate)/basalt composites have exhibited (at 20°C) a flexural modulus and strength as high as 20 GPa and 320 MPa, respectively. The flexural modulus and the flexural strength at 100°C have been found to be equal to 18 GPa and 230 MPa, confirming that this system can retain very good mechanical properties at a service temperature of 100°C. POLYM. COMPOS., 37:2549–2556, 2016. © 2015 Society of Plastics Engineers     

Iron(III) Chloride and Diorganyl Diselenide‐Promoted Nucleophilic Closures of 1‐Benzyl‐2‐alkynylbenzenes in the Preparation of 9‐(Organoselanyl)‐5H‐benzo[7]annulenes

Iron‐promoted cyclization of 1‐benzyl‐2‐alkynylbenzenes with diorganyl diselenides led to the synthesis of 9‐(organoselanyl)‐5H‐benzo[7]annulenes whereby the mutual action between diorganyl diselenides and iron(III) chloride in a 0.5:1.0 mol ratio was essential in order to achieve the maximal yields of the products. The cyclization reaction tolerated a variety of functional groups, such as trifluoromethyl, chloro, fluoro and methoxy, in both the 1‐benzyl‐2‐alkynylbenzenes and the diorganyl diselenides, giving the seven‐membered heterocyclic products exclusively via a 7‐endo‐dig cyclization process.

     

Hybrid numerical technique for evaluating wing aerodynamic loading with propeller interference

A computational investigation of the interference between wings having different aspect ratios and a tractor propeller has been carried out to accurately determine the time-averaged aerodynamic characteristics of the aircraft in terms of the modified wing loads. At first, the aerodynamic interaction has been studied by modeling the wakes both of propeller and wing, in isolated and coupled configurations. The model is based on a hybrid numerical technique, the free wake analysis (FWA) and boundary element method (BEM), applied to the wakes of a propeller and a wing, respectively. The output data has been compared with those available from the experimental procedures. Subsequently, to describe the effects of the two interacting wakes, a three-dimensional BEM approach for an untapered wingspan was applied to evaluate the wing quasisteady loads. The research focused on the wing pressure coefficient distribution related to the altered upstream conditions of the coupled propeller, hence the wing loads and the pitching moment are computed. The results confirm the advantages of the present approach using the FWA and BEM to identify the aerodynamic features of the mutual interference of a wing and a propeller at angle of attack and at a fixed propeller operating condition. Applications of this numerical hybrid scheme to an isolated wing and propeller, in quasisteady flow conditions, as well as to coupled configurations, are shown in the present paper. They demonstrate that accurate results can be obtained with very low computational effort.     

面粉中连二亚硫酸钠的分析与检测

对面粉中连二亚硫酸钠的检测方法进行研究.使用高锰酸钾对连二亚硫酸钠进行氧化,并用离子色谱进行分析,在扣除了面粉中的本底硫含量后,测定出了面粉中连二亚硫酸钠的添加量.结果表明,连二亚硫酸钠在面粉中的含量为500～2000 mg/kg时,其回收率在93.04～117.42 %,相对标准偏差在0.57～2.25 %,方法可行.