Finite volume treatment of dispersion-relation-preserving and optimized prefactored compact schemes for wave propagation

In developing suitable numerical techniques for computational aero-acoustics, the dispersion-relation-preserving (DRP) scheme by Tam and co-workers and the optimized prefactored compact (OPC) scheme by Ashcroft and Zhang have shown desirable properties of reducing both dissipative and dispersive errors. These schemes, originally based on the finite difference, attempt to optimize the coefficients for better resolution of short waves with respect to the computational grid while maintaining pre-determined formal orders of accuracy. In the present study, finite volume formulations of both schemes are presented to better handle the nonlinearity and complex geometry encountered in many engineering applications. Linear and nonlinear wave equations, with and without viscous dissipation, have been adopted as the test problems. Highlighting the principal characteristics of the schemes and utilizing linear and nonlinear wave equations with different wavelengths as the test cases, the performance of these approaches is documented. For the linear wave equation, there is no major difference between the DRP and OPC schemes. For the nonlinear wave equations, the finite volume version of both DRP and OPC schemes offers substantially better solutions in regions of high gradient or discontinuity.     

Evaluation of structural and electrochemical properties of the MnSb–Li system as anode for Li-ion batteries

The electrochemical reaction mechanisms between lithium and cystalline MnSb are investigated by X-ray diffraction, ¹²¹Sb Mössbauer spectroscopy, and X-ray absorption spectroscopy (XAS). The analysis of the experimental data at different depths of the electrochemical discharge process reveals a complex reaction mechanism comprising two steps. The main reaction of the first step corresponds to the dispersion of lithium in the MnSb matrix with formation of the intermediate compound LiMnSb. The second step corresponds to a Li–Sb alloying process with formation of Li₃Sb.     

Charge-transfer at silver/phthalocyanines interfaces

Valence band photoemission spectroscopy (VB-PES) and inverse photoemission spectroscopy (IPES) were employed to determine the occupied and unoccupied density of states upon silver deposition onto layers of two phthalocyanines (H₂Pc and CuPc). The two different Pc molecules give rise to very distinct behaviour already during the initial stage of silver deposition. While in the CuPc case no shift occurs in the energy levels, the H₂Pc highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are shifting simultaneously by 0.3 eV, i.e., the HOMO shifts away from the Fermi level while LUMO shifts towards the Fermi level. As the silver quantity increases the HOMO levels of both Pcs are shifting towards the Fermi level. When the Fermi level is resolved in the VB spectra, the characteristic features of H₂Pc and CuPc are smeared out to some extent. Shifts in HOMO and LUMO energy positions as well as changes in line shapes are discussed in terms of charge-transfer and chemical reactions at the interfaces.     

Surface fluorination of paper in CF4-RF plasma environments

Plasma-based technologies are an exciting alternative for cellulose andpaper modification. Barrier coatings and surface functionalization of celluloseenhances properties and creates new possibilities for cellulose-based products.A parallel plate radio frequency (RF)-plasma reactor was used to modify papersubstrates under discharge parameters such as power, time and pressure. Carbontetrafluoride RF-plasma treatment of paper caused intense fluorination and itwas demonstrated that the fluorination reaction mechanisms can be controlled bythe external plasma parameters. Fluorine contents as high as 51.3% (contactangle=147°) were obtained for the treated cellulose. It was shown that eventreatment times as low as 30 s can generate relative surface fluorineatomic concentrations as high as 30%. High resolution ESCA and ATR-FTIRanalysisindicated covalently bound CF_x functional groups with CF₄treatment. It was found that under certain experimental conditionssuper-hydrophobic paper surfaces are created by combining the high surfacefluorine atomic concentrations with specific plasma-generated surfacetopographies.     

Correction to: Ethylethanolammonium 4-nitrobenzoate

Journal of Thermal Analysis and Calorimetry - The temperature dependence of molar heat capacity of Ba1.5Fe2(PO4)3 phosphate was investigated between T = 6 and 670 K with...     

Dual‐emissive polydiphenylsilane nanocomposite: effect of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine‐Zn complex

The fluorescence properties of polysilane can be strongly influenced by creating new excited states that involve electronic transitions and the relaxation to the ground state. This work presents the optical effects obtained by doping a specially designed polydiphenylsilane copolymer with Zn complex of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine. The nanocomposites have been prepared in solution by mixing the polymer with low amounts of Zn–salophen and using tetrahydrofuran as solvent. The ultraviolet–visible spectrum has shown the occurrence of an intermolecular charge transfer between polysilane and the metal complex. Photoluminescence studies have revealed an interesting dual emission profile of nanocomposite. The origin of this phenomenon has been evidenced by molecular modeling and simulation of the electronic transitions. The modeling results have unveiled a new low‐lying excited state due to intermolecular interactions. The thin films of nanocomposites have been drop‐casted from solutions. The obtained films have been studied by Transmission Electron Microscopy (TEM)‐Scanning Transmission Electron Microscopy (STEM)‐Energy Dispersive X‐ray analysis (EDX) to gain information on the film‐forming capacity and surface morphology. The results have revealed a high potential of such materials for fluorescence sensing applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Interaction of Polystyrene Nanoparticles with Supported Lipid Bilayers: Impact of Nanoparticle Size and Protein Corona

Polystyrene is one of the most widely used plastics. This article reports on the interaction of 50 and 210 nm polystyrene nanoparticles (PSNPs) with human serum albumin (HSA) and transferrin (Tf), as well as their effect on supported lipid bilayers (SLBs), using experimental and theoretical approaches. Dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements show that the increase in diameter for the PSNP-protein bioconjugates depends on nanoparticle size and type of proteins. The circular dichroism (CD) spectroscopy results demonstrate that the proteins preserve their structures when they interact with PSNPs at physiological temperatures. The quartz crystal microbalance (QCM) technique reveals that PSNPs and their bioconjugates show no strong interactions with SLBs. On the contrary, the molecular dynamics simulations (MDS) show that both proteins bind strongly to the lipid bilayer (SLBs) when compared to their binding to a polystyrene surface model. The interaction is strongly dependent on the protein and lipid bilayer composition. Both the PSNPs and their bioconjugates show no toxicity in human umbilical vein endothelial (HUVEC) cells; however, bare 210 nm PSNPs and 50 nm PSNP-Tf bioconjugates show an increase in reactive oxygen species production. This study may be relevant for assessing the impact of plastics on health.     

Hydroacridines: part 29. 15N NMR chemical shifts of 9-substituted 1,2,3,4,5,6,7,8-octahydroacridines and their N-oxides-Taft, Swain-Lupton, and other types of linear correlations

The (15)N NMR chemical shifts of 1,2,3,4,5,6,7,8-octahydroacridine, 12 of its 9-substituted derivatives, and of the corresponding N-oxides were measured and examined in terms of the 9-substituent effects and the effects of N-oxidation. For the 9-substituent effects, good linear correlations were found with the Taft and Swain-Lupton substituent constants, for both octahydroacridines and their N-oxides. The (15)N chemical shifts of both octahydroacridines and their N-oxides also correlate well, linearly with the (13)C chemical shifts of the para-carbons in analogously substituted benzene derivatives.Within the studied compounds, the magnitudes of the N-oxidation effects range from - 16.4 to - 27.4 ppm (shielding), and also correlate linearly with the Taft and Swain-Lupton substituent constants, as well as with the bond orders of the N(+)-O(-) bonds in the corresponding N-oxides. Furthermore, a very good linear correlation is found between the (15)N chemical shifts of octahydroacridines and those of the corresponding N-oxides. From the (15)N chemical shifts data, the Taft and Swain-Lupton substituent constants for the diacetylamino group (-NAc(2)) were evaluated in the present paper, as follows: sigma(R) = 0.07 and sigma(I) = 0.15; R = 0.08 and F= 0.20.     

Planar Dielectrochromatography in a Vertical Chamber

JPC – Journal of Planar Chromatography – Modern TLC - Drawn by capillary forces the developing solvent (mobile phase) migrates through the thin layer (stationary phase) over a defined...     

Study of intramolecular competition between carboxylate and phosphonate for Pt(II) with the aid of a novel tridentate carboxylato-thioether-phosphonato ligand

The tridentate dianionic ligand 2-[2'-(hydroxyisopropoxyphosphoryl)phenylsulfanyl]benzoate (L(2-)) reacts with cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) to form an S,O-chelate in which the O-coordinated group is either carboxylate or phosphonate, depending on the degree of protonation of the complex. Carboxylate appears to be the stronger ligand, and the stoichiometric reaction between cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) and L(2-) yields the neutral species [Pt(L)(NH(3))(2)], with L bound by sulfanyl and carboxylate groups, both in solution and in the solid state. Upon protonation of [Pt(L)(NH(3))(2)], the stronger basicity of the carboxylate causes the Pt coordination to switch from carboxylate to phosphonate, and the uncoordinated carboxylate group becomes protonated. In methanolic solution, the first-order kinetics of this rearrangement could be observed by (31)P NMR spectroscopy. Both complexes-the carboxylate-bound neutral complex [Pt(L)(NH(3))(2)].H(2)O (triclinic, P1 (no. 2), a=9.529(6), b=9.766(6), c=12.299(7) angstroms, alpha=106.91(2), beta=101.71(2), gamma=102.05(2) degrees, Z=2) and the perchlorate salt of the phosphonate-bound complex [Pt(LH)(NH(3))(2)]ClO(4).H(2)O (monoclinic, P2(1)/c (no. 14), a=12.095(2), b=14.046(2), c=14.448(2) angstroms, beta=95.55(2) degrees, Z=4)-were characterized by X-ray crystallography.