A note on the regularity of flows with shear-dependent viscosity

We consider a non-Newtonian fluid governed by stationary, incompressible Navier–Stokes equations with shear-dependent viscosity. Using a fixed point argument in an appropriate functional setting, we establish the existence of a strong solution for small and suitably regular data. Uniqueness results are obtained under similar conditions.     

Synthesis of chiral crown ethers and complexation with chiral protonated amine compounds: X-ray crystal and nuclear magnetic resonance studies of perchlorate salt of chiral benzo-monoaza-15-crown-5 and chiral monoaza-15-crown-5

The X-ray crystal structure of IX, perchlorate salt of R-(?-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-H?O hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(?)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification.     

Simultaneous approximations to p-adic numbers and algebraic dependence via multidimensional continued fractions

The Ramanujan Journal - Unlike the real case, there are not many studies and general techniques for providing simultaneous approximations in the field of p-adic numbers $$mathbb Q_p$$ . Here, we...     

Synthesis of R-(-)-2-ethyl-N-benzyl (benzo-monoaza-15-crown-5) and the Crystal Structure of Its Sodium Perchlorate Complex

A new complex of a chiral monoaza-crown ether, [R-(-)-2-ethyl-N-benzyl-4,7,10,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene...NaClO₄], has been prepared and studied by x-ray diffraction. The compound crystallizes in space group P2₁ with cell dimensions a = 8.721(1), b = 16.318(2), c = 8.905(1) Å, = 100.80(1)°. The sodium cation is heptacoordinated and located significantly out of the best plane of the macrocycle ring. The donor atoms of the macrocycle are in the half-chair arrangement.     

In silico fight against novel coronavirus by finding chromone derivatives as inhibitor of coronavirus main proteases enzyme

Structural Chemistry - Novel coronavirus, 2019-nCoV is a danger to the world and is spreading rapidly. Very little structural information about 2019-nCoV make this situation more difficult for drug...     

LiMSO(4)F (M = Fe, Co and Ni): promising new positive electrode materials through the DFT microscope

A theoretical study of the lithium intercalated LiMSO(4)F and deintercalated MSO(4)F systems, where M = Fe, Co and Ni has been performed within the framework of density functional theory. Beyond predictions of structural evolution and average voltages versus a lithium electrode, we have applied partial density of states and Bader's topological analysis of the electron density to the study of lithium deintercalation. Upon lithium extraction, charge rearrangement occurs for nickel between different d-orbitals, but with little net positive charge gain, while cobalt and iron atoms end up with a clear oxidized state. The participation of oxygen ions in accepting the electron of the lithium is thus enhanced for LiNiSO(4)F. However, this effect does not affect the long-range electrostatic interactions a lot in the lithiated phase, since the valence of all transition metals is very close due to initial lower oxidized state for the Ni atom in the host. It is found that this is not essentially a long-range electrostatic interaction within the lithiated phase but within the host which explains, at least partly, the increase in voltage by passing from Fe to Ni. Our results also shed light upon the possibility of getting an approximate evaluation of the local strain associated with delithiation from the atomic volume evolutions, which are also likely to affect the electrochemical potential.     

Effect of acid,water and alcohol ratios on sol-gel preparation of antireflective amorphous SiO2 coatings

Varying amounts of nitric acid catalyst, water and ethyl alcohol were used in the preparation of SiO₂ sols by hydrolysis and condensation reactions of tetraethyl orthosilicate in a one step acid catalysis process. Hydrolysis of TEOS was followed by FT-IR analyses. Size of SiO₂ particles was seen to vary in 8–41 nm range with respect to changing HNO₃ and water amounts in the sols. Gelation occurred in some systems. Surfaces of films were examined by FESEM and AFM, after coating on glass substrates by dip coating. Thicknesses of the films were measured to be in the range of 80–120 nm. 5.6 ± 0.2% point increase in light transmittance was obtained when HNO₃/TEOS (mol/mol) ratio of 4.74 × 10^? 4 and H₂O/TEOS (mol/mol) ratio of 9.08 were utilized. Sols were found to be stable for months and coatings prepared after 45 days still provided 5.2 ± 0.2% point increase in light transmittance.     

Effect of thermal-treatment of wood fibres on properties of flat-pressed wood plastic composites

This study aimed to enhance the dimensional stability of flat-pressed wood plastic composites (WPCs) containing fast growing wood fibres by a thermal-treatment method. The wood fibres were treated at three different temperatures (120, 150, or 180 °C) for 20 or 40 min in a laboratory autoclave. The WPC panels were made from dry-blended Eucalyptus camaldulensis wood fibres and polypropylene (PP) powder (50:50 by weight) using a conventional flat-press process under laboratory conditions. Thickness swelling and water absorption of the WPC panels significantly decreased with increasing the treatment temperature and time. The thermal-treatment of eucalyptus wood fibres slightly decreased the screw withdrawal resistance of the WPC panels as compared to the reference panels while the flexural properties and internal bond strength were more seriously affected by the treatment. The present study revealed that the thermal-treatment of the wood fibres significantly improved the dimensional stability of the WPC panels.     

CuO Nanostructures Based Electrochemical Sensor for Simultaneous Determination of Hydroquinone and Ascorbic Acid

A simple, sensitive and reliable electrochemical sensor has been developed based on CuO nanostructures modified glassy carbon electrode for simultaneous determination of hydroquinone (HQ) and ascorbic acid (AA). The CuO nano material was synthesized by aqueous chemical growth method using different sources of OH. The characterization of nano material was performed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The glassy carbon electrode was modified by CuO nano material using drop cast method and studied by cyclic voltammetry. The CuO/GCE exhibited excellent electrocatalytic activity towards the oxidations of HQ and AA in borate buffer solution (pH 8.0) and the corresponding electrochemical signals have appeared as two well resolved oxidation peaks with significant peak potential differences of (0.21V vs. Ag/AgCl). Differential pulse voltammetry was used for simultaneous determination of HQ and AA using the CuO/GCE. At the optimum conditions, for simultaneous determination by synchronous change of the analyte concentrations, the linear response ranges were between 0.0003–0.355 mM for HQ and 0.0001–0.30 mM for AA respectively. Furthermore, CuO/GCE was successfully applied for the independent determination of AA in fruit juices as well as for the simultaneous determination of HQ and AA in cosmetic samples.     

Antibacterial glass films prepared on metal surfaces by sol–gel method

This paper describes the preparation and characterization of glass films consisting of SiO₂, Li₂O, Na₂O, K₂O or MgO in varying compositions on stainless steel and aluminum substrates by sol–gel method. Silver phosphate or silver incorporated zeolite was also introduced into the sols for obtaining antibacterial effect. The SiO₂/Li₂O/Na₂O system having the composition of 85:5:10 wt% was found as the optimum for obtaining a stable sol and film formation. The films were investigated by scanning electron microscopy (SEM) and electron dispersive analysis by X-ray (EDX), Fourier transformed infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Homogenous films having 300 ± 20 nm thicknesses were formed by spin coating and then by curing at 500 °C for 1 h. Obtained films had high adherence to the metal substrates and they were also durable in acidic, basic or NaCl environments. They also presented a powerful antibacterial effect against E. coli.