Search results for "MINERALOGY"

Physical modelling of the melt flow during large-diameter silicon single crystal growth

2003

Abstract The reported investigations concern physical modelling of Czochralski growth of silicon large-diameter single crystals. InGaSn eutectic was used as a modelling liquid, employing actual criteria of the real process (Prandtl, Reynolds, Grashof numbers, etc.) and geometric similarity. A multi-channel measuring system was used to collect and process the temperature and flow velocity data. The investigations were focused on the study of heat transfer, in particular, the instability of the “cold zone” of the melt at the crystallization front.

Analysis of archaeological pottery by X-ray fluorescence spectrometry applying the limit dilution method

1994

A method for correcting the intensity of x-ray fluorescence (limit dilution method) is proposed for the analysis of samples with a complex matrix such as ceramic materials of archaeological interest. This method corrects the interelement effects, resolving the wide deviations which occur in the quantitative results obtained by x-ray fluorescence without correction. The contents of sodium, magnesium, aluminium, silicon, potassium, calcium, titanium and iron in sixteen archaeological ceramic samples of different origins and from different locations were determined. The results obtained are comparable to the values obtained by chemical analysis. A statistical study of the data was carried out …

The structure and stoichiometry of C-S-H

2004

Abstract This review relates to the models describing the structural evolution of calcium silicate hydrate (C-S-H) at the crystal–chemical level as a function of composition in terms of calcium to silicon ratio. The different models are compared and discussed in the light of recent spectroscopic and microscopic data. Taking into account the structure and the morphological properties of C-S-H, a surface reaction thermodynamic model has been proposed and discussed to predict and correlate the chemical and structural evolution of C-S-H with solution chemistry.

Laser-Ablation-Induced Synthesis of SiO2-Capped Noble Metal Nanoparticles in a Single Step

2010

Here we describe a simple, powerful technique based on the laser ablation of a target immersed in a water solution of a metal salt. With this method, nanoparticles of different metals and alloys can be processed very quickly. Both the target and the salt solution can be chosen to produce metal nanoparticles of different sizes, surface-oxidized nanoparticles (silica-silver, for example), or even more complex structures to be defined by the researcher on one or more steps because the technique combines the advantages of both physical and chemical methods. We have applied this technique to the fabrication of inert silica-metal (silver, gold, and silver-gold) nanoparticles with a strong surface…

Switchable Bactericidal Effects from Novel Silica-Coated Silver Nanoparticles Mediated by Light Irradiation

2011

Here we report on the triggering of antibacterial activity by a new type of silver nanoparticle coated with porous silica, Ag@silica, irradiated at their surface plasmon resonant frequency. The nanoparticles are able to bind readily to the surface of bacterial cells, although this does not affect bacterial growth since the silica shell largely attenuates the intrinsic toxicity of silver. However, upon simultaneous exposure to light corresponding to the absorption band of the nanoparticles, bacterial death is enhanced selectively on the irradiated zone. Because of the low power density used for the treatments, we discard thermal effects as the cause of cell killing. Instead, we propose that …

Volume strain, strain type and flow path in a narrow shear zone

1998

This study explores the state of finite strain and changes in the mean kinematic vorticity number, grain size, whole-rock chemistry and mineralogy across an upper amphibolite-facies shear zone in a metadiorite, northern Malawi, east-central Africa. P–T conditions during shear-zone formation and deformation were approximately 700–750 °C and 5–7 kbar and are slightly less than P–T conditions for the regional peak of metamorphism. The major rock-forming minerals, plagioclase, hornblende, biotite, and quartz, were deformed by crystal-plastic processes accompanied by, except for hornblende, dynamic recrystallization. The modal abundance of all four major rock-forming minerals shows no systematic…

Riedel-shear control on the development of pennant veins: Field example and analogue modelling

2006

Abstract The wall rocks of a crustal scale sinistral ductile shear zone in Namibia, the Purros Mylonite Zone, contain two types of asymmetric quartz veins. Bedding surfaces contain sigmoidal quartz veins with limited thickness along their symmetry axes that can be classified as tension gashes. A second type of veins consists of a striated central fault vein separating pennant-type quartz filled terminations. The tips of these “pennant veins” have a different orientation to those of the tension gashes. Analogue experiments were carried out using a sheet of silicone powder suspended on a slab of poly-dimethyl-siloxane (PDMS), both deformed in simple shear. These experiments produced open frac…

Erratum to “Identification of unknown dead bodies by X-ray image comparison of the skull using the X-ray simulation program FoXSIS” [Forensic Sci. In…

2001

Float glass colouring by ion exchange

2008

Abstract Back in the Middle Ages, glass artists used to produce yellowish colorations in soda-lime glasses using mixtures that contained silver salts, clay composites and natural oils. The resulting colour was a characteristic pale yellow known as silver-stain. This coloration is mainly caused by the extinction – absorption and, to a lesser extent, scattering – of light occasioned by silver nanoparticles formed inside the glass. This colouring technique comprises a heat treatment divided in two stages: in the first one, an ion exchange between the silver ions in the mixture and the alkali ions in the glass takes place. This process is called nucleation of silver nanoparticles. The second st…

A laboratory analysis of falling head infiltration procedures for estimating the hydraulic conductivity of soils

2006

Abstract Falling head (FH) infiltration procedures can give rapid estimates of the field saturated hydraulic conductivity ( K fs ) of soils. The objectives of this investigation were to develop a procedure for estimating both the K fs and the α ⁎ parameter of the exponential hydraulic conductivity function from a FH experiment, and to compare FH procedures differing by experimental and computational demands. A total of 33 FH experiments were carried out on repacked, sandy loam and loam soil cores. A two level (TL) analysis was applied to determine a value of α ⁎ for each soil core. K fs was then calculated by three different approaches, ranging from the fitting approach (FA) that used the m…