Obliquely propagating quantum solitary waves in quantum‐magnetized plasma with ultra‐relativistic degenerate electrons and positrons

The oblique propagation of the quantum electrostatic solitary waves in magnetized relativistic quantum plasma is investigated using the quantum hydrodynamic equations. The plasma consists of dynamic relativistic degenerate electrons and positrons and a weakly relativistic ion beam. The Zakharov‐Kuznetsov equation is derived using the standard reductive perturbation technique that admits an obliquely propagating soliton solution. It is found that two types of quantum acoustic modes, that is, a slow acoustic mode and fast acoustic mode, could be propagated in our plasma model. The parameter that determines the nature of soliton, that is, compressive or rarefactive soliton, for slow mode is investigated. Our numerical results show that for the slow mode, the determining parameter is ion beam velocity in the case of relativistic degenerate electrons. We also have examined the effects of plasma parameters (like the beam velocity, the density ratio of positron to electron, the relativistic factor, and the propagation angle) on the characteristics of solitary waves.     

Double-walled carbon nanotube with surrounding elastic medium under axial pressure

In this paper, the buckling behavior and critical axial pressure of double-walled carbon nanotubes (DWCNTs) with surrounding elastic medium are investigated. A double-shell (circular cylindrical shell) model is presented and the effects of surrounding elastic medium on the outer tube and the van der Waals forces between two adjacent tubes are taken into account. The analysis and the numerical solution method are based on the classical theory of plates and shells and the Galerkin method. Equations are derived for the critical axial forces and pressures of DWCNTs; the critical axial forces and pressures are calculated for different axial half sine wavenumbers and circumferential sine wavenumbers and compared with those for single-walled carbon nanotubes (SWCNTs).Results indicate that the critical axial force of a DWCNT is higher than that of an SWCNT, but the critical axial pressure of a DWCNT is lower than the critical axial pressure of a SWCNT. Although the critical axial force of a DWCNT decreases as the axial half sine wavenumbers increase, it rises as the circumferential sine wavenumbers increase.     

Thermal and structural properties of sodium,potassium and carbonate doped strontium hydroxyfluorapatite

Ion-doping in hydroxyapatite bioceramics has attracted a lot of interest particularly for biomedical applications in repairing and replacing failure parts of musculoskeletal systems. Thus the multiple doping aims to mimic and resemble the chemical composition of the bone mineral component. Herein strontium hydroxyapatites bioceramics containing sodium Na⁺ and potassium K⁺ as cationic substituent and carbonate CO₃^2? and fluoride as anionic substituent were synthesized and characterized by several analysis techniques. Therefore the chemical assays indicated that obtained compounds were less stoichiometric comparably to bone tissues. The X-ray diffraction diagrams and the infrared spectra revealed that pure phases of hydroxyfluorapatite containg the cited ions were obtained. The triple insertion of sodium, potassium and carbonate into the apatite structure leaded to the B-type carbonate apatite. The FE-SEM micrographs of the powders were formed by agglomerates. Moreover, the particles' morphology strongly depends on the ions nature and amount. The D-GTA curves indicated that the heating of the powders from the room temperature to 1000 °C didn't affect the structural and thermal stability of the materials apart from a partial decomposition of the apatite inducing the formation of the β-tristrontium phosphate phase and enhancing the biomaterial character of the materials.     

Development of some hypersonic benchmark flows using CFD and experiment

Abstract. This paper presents a set of test cases in high speed aerodynamics that describe our perceived relationship between experiment and computation. Computational fluid dynamics, with sensible interpretation, can guide experimental design, so that wind tunnel studies can focus better on fundamental ‘benchmark’ studies. Likewise experimental data may be used as feed back to evaluate codes and to improve their physical modelling. Here we present several test cases, developed in our laboratory, that we regard as basic ‘building blocks’ for high speed aerodynamics. These include: design for boundary-layer/pressure-gradient interaction; cavity flows; shock-wave/boundary-layer interactions; techniques for a graduated and controlled study of three-dimensional separated flows. Received 10 October 2001/ Accepted 19 November 2002 Published online 4 February 2003 Correspondence to: R. Hillier (r.hillier@ic.ac.uk) An abridged version of this paper was presented at the 23rd Int. Symposium on Shock Waves at Fort Worth, Texas, from July 22 to 27, 2001     

‘Click Synthesis’ of Some Novel Benzimidazol Oxime Ethers Containing Heterocycle Residues as Potential ß‐Adrenergic Blocking Agents

The ‘click synthesis’ of some novel O‐substituted oximes, 5a – 5j , which contain heterocycle residues, as new analogs of ß‐adrenoceptor antagonists is described (Scheme 1). The synthesis of these compounds was achieved in four steps. The formation of (E)‐2‐(1H‐benzo[d]imidazol‐1‐yl)‐1‐phenylethanone oxime, followed by their reaction with 2‐(chloromethyl)oxirane, afforded mixture of oil compounds 3 and 4 , which by a subsequent tetra‐n‐butylammonium bromide (TBAB)‐catalyzed reaction with N H heterocycle compounds (Scheme 1), led to the target compounds 5a – 5j in good yields.     

CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> separation using mixed matrix membrane-based polyurethane incorporated with ZIF-8 nanoparticles

This study presents using zeolitic imidazolate framework-8 (ZIF-8) as porous filler dispersed phase and polyurethane (PU) as continuous phase to synthesis mixed matrix membranes (MMMs). ZIF-8 nanoparticles were synthesized using centrifugal method. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). In order to investigate the effect of ZIF-8 loading on the membrane performance in CO₂/CH₄ separation, different membranes were prepared with various amounts of ZIF-8 (0–50 wt%). Membranes properties were characterized by SEM, XRD, TGA, differential scanning calorimetry (DSC), and tensile analysis. SEM images exhibit that the ZIF-8 is dispersed uniformly in cross section of membrane. Thermal stability of membranes increases with addition of the ZIF-8 nanoparticles into the polymer matrix. Both tensile strength and strain at break in the MMMs increase with the ZIF-8 loading. To study the effect of feed pressure on CO₂ and CH₄ transport properties of the membranes, single gas experiments were conducted at 4, 8, and 12 bar feed pressures. Incorporation of ZIF-8 crystals into continuous PU matrix resulted in high-performance gas separation membranes. Increasing feed pressure, significantly, increased separation performances in all the membranes.     

Ultrasensitive aptasensing of lysozyme by exploiting the synergistic effect of gold nanoparticle-modified reduced graphene oxide and MWCNTs in a chitosan matrix

Microchimica Acta - The authors describe a lysozyme aptasensor based on the use of gold nanoparticles (AuNP) assembled on the carbon nanotubes, graphene oxide and chitosan. An electrochemical...     

Microwave-assisted effi cient synthesis of azlactone derivatives using 2-aminopyridine-functionalized sphere SiO2 nanoparticles as a reusable heterogeneous catalyst

In the present work, the highly efficient Erlenmeyer synthesis of azlactones catalyzed by 2- aminopyridine, supported on nano-sphere SiO2 is reported. First, the silica nanoparticles were modified with triethoxysilylpropyl chloride and then 2-aminopyridine was attached to the support via covalent linkages. This new heterogenized catalyst was used for efficient microwave-assisted synthesis of azlactone derivatives with Ac2O as a condensing agent under solvent-free conditions. The present method offers advantages including high yields, short reaction times and simple work-up. Also, the catalyst can be easily recycled and reused several times, which makes this method attractive, economic and environmentally-benign.     

Absence of biological damage from prolonged exposure to intravascular ultrasound: a swine model

Ultrasound (US) has been used in IMS II (intravascular US) and CLOTBUST (transcranial US) clinical trials for thrombolysis. During the treatment, in addition to the targeted thrombus, other biological components, such as blood and vessel walls are subjected to long durations of US exposure. In this study we explored evidence of biological damage due to mechanical forces or thermal effects of US exposure at the frequency, intensity and duration employed for thrombolysis treatment. Biological effects were investigated by exposing swine ilio-femoral arteries bilaterally to an intravascular US generating catheter and a conventional catheter. A total of 12 animals each underwent 8h of exposure to intravascular pulsed US with a frequency of 2.2MHz and spatial peak time average intensity (I(SPTA)) of 6W/cm(2) per transducer (a total of six transducers per catheter) while the ultrasonic device surface temperature was maintained at 43 degrees C. The animals were euthanized either 24+/-3h or 28+/-3 days post treatment. A range of physiological and hematological parameters were evaluated pre-, post-, and during US exposure. The vascular diameter was determined pre- and post-US exposure using angiograms. Following euthanasia, each animal underwent a gross pathological examination, and the treated vessels and an unexposed vessel were excised for comparative histopathological evaluation. No evidence of biological damage was found at the end of 8h exposure to intravascular US.     

Polynuclear 3d complexes based on potentially tetra-anionic heptadentate ligands including amido,amino and phenoxo donors: Synthesis,crystal structure and magnetic properties

The synthesis and characterization of new dinuclear Mn^III and tetranuclear Cu^II complexes, [HL¹Mn(DMSO)]₂ (1) and [H₂L²Cu₂(MeO)₂]₂ (2), are reported (H₄L¹ = 2-hydroxy-N-[2-({2-[(2-hydroxybenzoyl)amino]ethyl}amino)ethyl]benzamide and H₄L² = 2-hydroxy-N-[3-({3-[(2-hydroxybenzoyl)amino]propyl}(methyl)amino)propyl]benzamide). Single crystal X-ray structures have been determined for 1 and 2. In 1 only one of the two amide functions of H₄L¹ is deprotonated in addition to the phenol ones, while in 2 all the amide functions of H₄L² are protonated and none of the potential nitrogen donors (amide and amine) is involved in the coordination to copper. HL¹ and H₂L² do not play the role of compartmental ligands and do not wrap around one Mn and one Cu ion, respectively, but embrace two metal centers yielding, with the respective assistance of auxiliary DMSO and methoxo ligands, dinuclear manganese and tetranuclear copper complexes, respectively. 1 includes two well isolated Mn^III ions (Mn?Mn′ = 7.33 Å) that do not interact magnetically. The intermolecular Mn?Mn″ distance along the 1D chains (10.17 Å) is also too large to allow extended magnetic interactions. The pairwise magnetic interactions between the copper(II) ions in the tetranuclear complex 2 are so large that the χ_MT product is already equal to zero at room temperature, implying that the antiferromagnetic interaction is around −1000 cm⁻¹, as observed previously for di-μ-hydroxo–dicopper complexes.