Theoretical study of reactive melt infiltration to fabricate Co-Si/C composites

Cobalt-silicon based carbon composites (Co-Si/C) have established a noteworthy consideration in recent years as a replacement for conventional materials in the automotive and aerospace industries. To achieve the composite, a reactive melt infiltration process (RMI) is used, in which a melt impregnates a porous preform by capillary force. This method promises a high-volume fraction of reinforcement and can be steered in such a way to get the good “near-net” shaped components. A mathematical model is developed using reaction-formed Co-Si alloy/C composite as a prototype system for this process. The wetting behavior and contact angle are discussed; surface tension and viscosity are calculated by Wang's and Egry's equations, respectively. Pore radii of 5μm and 10μm are set as a reference on highly oriented pyrolytic graphite. The graphs are plotted using the model, to study some aspects of the infiltration dynamics. This highlights the possible connections among the various processes. In this attempt, the Co-Si (62.5 at.% silicon) alloy's maximum infiltration at 5 μm and 10 μm radii are found as 0.05668 m at 125 s and 0.22674 m at 250 s, respectively.     

Synthesis, structural elucidation and biological activities of organotin(IV) derivatives of (E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoic acid

A new series of di- and tri-organotin(IV) compounds with the general formula R_4?n SnL _n , where R?=?Me (1,2), Et (3), n-Bu (4,5), n-Oct (6), Ph (7) and L?=?(E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoate, were synthesized by reaction of silver salt of ligand or ligand acid with diorganotin dichloride/oxide and triorganotin chloride in 2:1 and 1:1 molar ratio, respectively. These compounds were characterized by elemental analyses, FT-IR, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and mass spectrometry. The spectroscopic results revealed that all the diorganotin(IV) compounds possess trigonal bipyramidal structures in solution and octahedral geometry in the solid state around the tin atom. A linear polymeric trigonal bipyramidal structure in the solid state and a tetrahedral environment around the tin atom in non-coordinating solvents has been proposed for the triorganotin(IV) compounds. All synthesized compounds were tested in vitro against a number of microorganisms to assess their biocidal activity. These studies revealed that ligand acid and some of its organotin compounds show promising activity against different strains of bacteria and fungi but lowered than reference drugs.     

Crystallographic report: 1,1‐Diphenyl‐3‐(triphenylgermyl)‐3‐(4‐chlorophenyl) propanol

The germanium atom in [(C₆H₅)₃GeCH(4‐ClC₆H₄)CH₂C(C₆H₅)₂OH] is in a distorted tetrahedral geometry. Steric hindrance precludes O? H···O intra‐ or inter‐molecular bonding. Copyright © 2005 John Wiley & Sons, Ltd.     

O-Alkylation of Menthone Oxime: Synthesis and 13C NMR Studies of a Series of Novel Oxime Ethers

A series of novel menthone oxime ethers were synthesized in three steps starting from (–)-menthol. Analysis of the ¹³C NMR chemical shift differences between α carbons of oxime derivatives (O-alkyl oximes) provides a convenient and reliable means of assigning oxime stereochemistry. It has been found that carbons syn to the oxime are shifted more upfield than carbons anti to the oxime moiety. Significant E products were obtained.     

Selective extraction of fungicide carbendazim in fruits using β‐cyclodextrin based molecularly imprinted polymers

Considering the importance of developing a new analytical approach for pesticide residue detection for the sake of ensuring food safety, a β‐cyclodextrin based molecularly imprinted polymer was prepared for selective determination of carbendazim. The polymers consist of a porous and hollow structure demonstrating the selective abundant adsorption sites for carbendazim molecule. The selectivity and adsorption capacity of the imprinted polymers were analyzed with dispersive solid‐phase extraction and analyzed with high performance liquid chromatography coupled with ultraviolet. The results of imprinted polymers were higher than non‐imprinted polymers with the maximum adsorption capacity of 3.65 mg/g within 30 min of total adsorption time. The reusability of the imprinted polymers was determined to evaluate its effectiveness and stability, which proved that the polymers lost 10% efficiency within seven consecutive recycles. The developed method displayed good linearity over the concentration range of 0.05–2.0 mg/L. The recovery percentage of 81.33–97.23 with relative standard deviations of 1.49–4.66% was obtained from spiked apple, banana, orange, and peach samples with a limit of detection of 0.03 mg/L and a limit of quantification of 0.10 mg/L (signal to noise ratio = 3/10). The overall performance of the proposed method evident that this technique provided a desirable outcome and it can be used as a convenient approach, as it qualifies the analytical standards.     

Vanadium(III) Complexes of Oxygen Donor Ligands; Their Synthesis,Spectral Characterization and Antimicrobial Studies

A new series of vanadium(III) complexes with oxygen donor ligands have been synthesized and characterized on the basis of elemental analysis, conductance, infra‐red spectroscopy, electronic spectral data and mass spectrometry. Thermal stabilities of the complexes and their kinetics were studied through thermogravimetric analysis. Estimation of vanadium in the complexes is carried out by ICP‐AES. Biological activities of the complexes 2 – 5 , 7 and 8 have also been tested against various bacteria and fungi.     

How to build time-lock encryption

Time-lock encryption is a method to encrypt a message such that it can only be decrypted after a certain deadline has passed. We propose a novel time-lock encryption scheme, whose main advantage over prior constructions is that even receivers with relatively weak computational resources should immediately be able to decrypt after the deadline, without any interaction with the sender, other receivers, or a trusted third party. We build our time-lock encryption on top of the new concept of computational reference clocks and an extractable witness encryption scheme. We explain how to construct a computational reference clock based on Bitcoin. We show how to achieve constant level of multilinearity for witness encryption by using SNARKs. We propose a new construction of a witness encryption scheme which is of independent interest: our scheme, based on Subset-Sum, achieves extractable security without relying on obfuscation. The scheme employs multilinear maps of arbitrary order and is independent of the implementations of multilinear maps.     

A weak Galerkin method for second order elliptic problems with polynomial reduction

The second order elliptic equation, which is also know as the diffusion-convection equation, is of great interest in many branches of physics and industry. In this paper, we use the weak Galerkin finite element method to study the general second order elliptic equation. A weak Galerkin finite element method is proposed and analyzed. This scheme features piecewise polynomials of degree $k\geq 1$ on each element and piecewise polynomials of degree $k-1\geq 0$ on each edge or face of the element. Error estimates of optimal order of convergence rate are established in both discrete $H^1$ and standard $L^2$ norm. The paper also presents some numerical experiments to verify the efficiency of the method.     

Mononuclear vs. binuclear carboxylates of copper(II) with 2,2′‐bipyridine: Synthesis,characterization, structural description,and properties

Two new copper(II) carboxylate complexes with 2,2′‐bipyridine and para‐nitrophenyl acetate (complex 1 ) and phenyl acetate (complex 2 ) have been synthesized; isolated in quantitative yield; and characterized using fourier‐transform infrared spectroscopy (FT‐IR), electron paramagnetic resonance, absorption spectroscopy, electrochemistry, and powder and single crystal X‐ray diffraction (XRD) techniques. Being mononuclear, the geometry around copper in complex 1 is a Jahn–Teller distorted octahedral, while complex 2 is binuclear with slightly distorted square pyramidal geometry around both copper ions. Powder XRD indicated several peaks in spectra of both complexes, which coincided with their theoretical spectra. FT‐IR results of the carboxylate stretching frequency were in accordance with the single crystal structure data. Electron paramagnetic resonance spectra of complexes 1 and 2 yielded g_┴ values of 2.06161 and 2.24623 and 1.94959, respectively, indicating a localized electron in b₁ (d _x²_–y²‐orbital). Ultra‐violet (UV)–visible spectroscopy and electrochemistry helped in characterization, as well as in deoxyribonucleic acid (DNA)‐binding ability of the complexes, yielding DNA‐binding constant values = 1.351 × 10⁴ and 1.361 × 10⁴ and 1.820 × 10⁴ and 2.426 × 10⁴ M^?1, respectively, for complexes 1 and 2 . The complexes demonstrate good biological potential.     

Magneto-Priming Improved Nutraceutical Potential and Antimicrobial Activity of Momordica charantia L. Without Affecting Nutritive Value

The need for some economic strategies for increased growth and nutraceuticals of medicinal plants is well acknowledged now. It was hypothesized that external magnetic field treatment (MFT) of seeds affecting internal magnet of cells may affect growth and metabolism. In this study, seeds were subjected to pre-sowing magnetic field (50 mT at 5 mm for 5 s). At vegetative stage, the leaf growth, chlorophyll content, catalase (CAT), peroxidase (POD), amino acids, proteins, flavonoids, soluble sugars, total soluble phenolics, carotenoids, anthocyanins, phenolic profile (HPLC based), and antimicrobial activity of leaves (in terms of the minimum inhibitory concentration against Staphylococcus aureus and Pseudomonas aeruginosa) were studied. Yield was evaluated for nutritive components in fruit (peel+pulp) and peel. MFT improved germination percentage, growth, leaf chlorophyll, antimicrobial activity, peel amino acids, phenolics, and POD with negligible effect on fruit nutritive value. Moreover, photosynthetic pigments and cinnamic acid exhibited direct correlation with antimicrobial potential against both pathogens. However, sinapic acid showed positive correlation against Staphylococcus aureus only. Cinnamic acid, coumaric acid, syringic acid, and quercetin were in direct correlation against Pseudomonas aeruginosa; it was directly correlated with total flavonoids too. In conclusion, magnetic field can be used to manipulate plant cell metabolism promising improvement of growth, antimicrobial activity, and phenolics of interest.