Inequalities for Volumes of Simplices in Terms of Their Faces

By generalizing some well-known results, we first obtain an inequality involving the volume and product of s-contents of s-faces of an n-simplex. Using this we generalize two inequalities maximizing the volume of one or two simplices in terms of their edge lengths.     

Dextran-modified iron oxide nanoparticles

Dextran-modified iron oxide nanoparticles were prepared by precipitation of Fe（Ⅱ） and Fe（Ⅲ） salts with ammonium hydroxide by two methods. Iron oxide was precipitated either in the presence of dextran solution, or the dextran solution was added after precipitation. In the second method, the iron oxide particle size and size distribution could be controlled depending on the concentration of dextran in the solution. The nanoparticles were characterized by size-exclusion chromatography, transmission electron microscopy and dynamic light scattering. Optimal conditions for preparation of stable iron oxide colloid particles were determined, The dextran/iron oxide ratio 0-0,16 used in precipitation of iron salts can be recommended for synthesis of nanoparticles suitable for biomedical applications, as the colloid does not contain excess dextran and does not coagulate.     

Anodic Sampling and TLC Identification of Dental Alloys

JPC – Journal of Planar Chromatography – Modern TLC - Knowledge of the composition of an incorporated alloy is a precondition for avoiding polymetallism in subsequent prosthetic...     

Effectiveness of neutralization process in reducing heavy metals concentrations in discharged sludge from the treatment of sulphide ore for gold using instrumental neutron activation analysis

The effectiveness of the neutralization process on heavy metals precipitated in sludge has been evaluated using instrumental neutron activation analysis (INAA) facilities at the South African Nuclear Energy Corporation (Necsa). The elemental concentrations of Th, Fe, Ag, Co, Cr, As, Au and K were reduced after the neutralization process with the exception of Mn and Sn which appeared to be enhanced by the neutralization process. Even though the neutralization process was targeted at the basic ferric arsenate compound, it was found to be effective in reducing other elemental concentrations. The variations in the geochemical compositions of the sulphidic ores during treatment at various stages also showed that physical processing stages do not significantly alter the elemental concentrations in the feed materials, however, the chemically active processing stages do. Also, the enhancement of the elements at the chemical stages depends on total quality control, where the application was not very repeatable the pattern of variation of elements at some stages was found to be irregular irrespective of the ore grade. The elements; Sn, Fe, Th, K, Au, Ag, As, Cr, and Co were enhanced in almost all the chemically active stages. Au was much more enhanced during flotation and bio-oxidation processes. Correlation analysis performed to determine the distribution patterns show that Fe, As, Ag and Co are geochemically associated and might be enriched simultaneously.     

Quantification of (−)-Epicatechin and Procyanidin B2 in Chocolates

JPC – Journal of Planar Chromatography – Modern TLC - Validation of a method for the quantification of (−)-epicatechin and procyanidin B2 in chocolates is reported. After a simple...     

Triazole, benzotriazole and substituted benzotriazoles as corrosion inhibitors of iron in aerated acidic media

The effect of a 1H-1,2,3-triazole, 1,2,3-benzotriazole and a number of substituted benzotriazoles, namely 1-hydroxybenzotriazole, 1H-benzotriazole-1-methanol and N-(1H-benzotriazol-1-ylmethyl)-formamide, have been investigated with respect to the corrosion of iron in 1 mol/l HCl and 1 mol/l HClO₄. The Tafel extrapolation method, linear polarization resistance and electrochemical impedance spectroscopy illustrate the inhibiting effect of all of these compounds in both acids. They are better inhibitors in 1 mol/l HCl than in 1 mol/l HClO₄. The changes of charge transfer resistance are also indicative for adsorption and inhibition of all of these compounds. This effect increases with time up to 16 h. An equivalent circuit is suggested as a model for the impedance. The adsorption of triazole-type of compounds in both acids follows a Langmuir isotherm. Molecular modeling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies.     

The magnetoresistivity of dilute AlMn alloys

A set of accurate measurements of the low temperature magnetoresistivity of dilute AlMn alloys is presented. By using an AlV alloys as a baseline, the resulting negative magnetoresistivity is obtained and compared with theoretical calculations.     

Resistivity variation near the critical temperature in some Ni-Fe base amorphous alloys

Accurate measurements of the electrical resistivity of three Ni_80?xFe_xP₁₄B₆ alloys (with x=10, 20 and 30) were performed in the temperature interval 1.5–500 K. Resistivity (ρ) and dρ/dT behaviours near T_c for the alloys with different x values are mutually very different. In particular $\text{dρ}\text{dT}$ variation near T_c for the alloys with x=10 and 20 is Ornstein-Zernicke like while for the alloy with x=30 is of more usual energy like type. A tentative explanation of this behaviour in terms of the influence of the percolation limit on the nature of the magnetic transition is offered.     

Low temperature resistivities of FexNi80-xP14B6 metallic glasses

The resistivities of six Fe_xNi_80-xP₁₄B₆ alloys have been measured between 1.5 and 50 K. It is found that the resistivity variations both below and above the resistivity minima depend on the transition metal composition. The room temperature coefficients of the resistivity indicate the existence of the magnetic contribution to the resistivity.