Electron-impact excitation of Ar+: an improved determination of Ar impurity influx in tokamaks

Electron-impact scattering data for argon and its ions continue to be of interest in studies of magnetically confined plasmas. In an earlier paper, Griffin et al (1997 J. Phys. B: At. Mol. Opt. Phys. 30 3543) employed the results of 28-term and 40-term R-matrix calculations of electron-impact excitation in Ar+ to carry out a collisional-radiative modelling study of the impurity influx of argon in tokamaks. We have now completed a 452-term R-matrix with pseudo-states (RMPS) calculation of electron-impact excitation for Ar+ in order to provide more accurate excitation data; using these improved data, we have repeated the modelling studies presented in the earlier paper. We compare our excitation data, as well as the results of the collisional radiative calculations, with those arising from the 40-term R-matrix calculation and find significant differences.

The application of atomic physics within impurity diagnostics for fusion plasmas

With the focus of ITER on the transport and emission properties of tungsten, generating atomic data for complex species has received much interest. Focusing on impurity influx diagnostics, we discuss recent work on heavy species. Perturbative approaches do not work well for near neutral systems so non-perturbative data are required, presenting a particular challenge for these influx diagnostics. Recent results on Mo+ are given as an illustration of how the diagnostic applications can guide the theoretical calculations for such systems.

Calculation of the optical conductivity for the Anderson impurity model using the slave boson technique

The optical conductivity of the Anderson impurity mode l has been calculated by emp l oying the slave boson technique and an expansion in powers of l i N, where N is the d egeneracy o f the f electron level . This method has been used to find the effective mass of the conduction electrons for temperatures above and below the Kondo tempera ture. For low temperatures, the mass enhancement is f ound to be large while a t high t emperatures, the mass enhancement is sma ll. The conductivity i s f ound to be Drude like with frequency dependent effective mass and scattering time for low independent effective mass and temperatures and scattering time f requency for high t emperatures. The behavior of both the effective mass and the conductivity is in qualitative agreement with experimental r esul t s .

Spectral Reflectance Characteristics of Kimberlite Indicator Minerals and Other Selected Mineral Grains

High chromium content in kimberlite indicator minerals such as pyrope garnet and diopside is often correlated with the presence of diamonds. In this study, kimberlite indicator minerals were examined using visible light reflectance spectroscopy to determine if chromium content can be correlated with spectral absorption features. The depth of absorption features in the visible spectral region were correlated with the molecular percentage of chromium and other first series transition metal elements obtained by electron microprobe data. In the visible part of the spectrum, chromium is evident by 3 absorption features in the pyrope reflectance spectrum; one isolated and narrow feature at the wavelength 689 nm was used to correlate with the chromium mol %. The isolation of this feature in the pyrope spectra is advantageous since it is not directly affected by other proximal absorption bands that could be caused by other transition metals. Analysis of the feature indicates that as grain volume increases the depth of the absorption feature will also increase. Clustering grain volumes into fractions yields better correlation between absorption depth and mol % chromium. Other types of garnet (almandine, grossular, spessartine) and kimberlite indicator minerals (olivine, diopside, chromite, ilmenite) were analyzed to determine if other absorption features could be used to predict the proportion of specific transition metal elements. Diopside in particular illustrates the same isolated chromium absorption feature as pyrope and may indicate mol percent but needs further study with larger sample sets.

Accounting for Human Rights Violations Risk: Conflict Minerals Mandatory Disclosures under the Dodd Frank Act

This paper examines the equity market response to firms’ disclosure of human rights violation risk with regard to conflict mineral usage as required by Section 1502 of the Dodd-Frank Act (the Act). This paper assesses the aggregate equity market response to regulatory events leading to the passage of the Act, the equity market reaction to voluntary early disclosures and mandatory disclosures of conflict mineral information in Form SD, as well as the determinants of the equity market response. Using a sample of 4,399 US registrants from January 1, 2008 to September 30, 2014, we document a significant negative stock market reaction to the passage of the Act and to conflict minerals disclosures on Form SD. The equity market reaction is more negative and limited to companies that source their minerals from conflict zones, companies with human rights violations, and companies with ambiguous disclosures. Taken together, the results of this study provide an economic justification for companies with poor conflict minerals practices to improve in order to avoid high costs that will arise if firms are forced to disclose human rights abuses. This paper also provides preliminary evidence that Form SD is successful in reducing the governance gap that exposes investors to unnecessary sanction, litigation and reputation risk from firms’ activities in conflict minerals usage.

Aproximació a l'estudi dels minerals a Cicle Inicial i Mitjà. 'Aproximación al estudio de los minerales en el Ciclo Inicial y Medio'.

Resumen basado en el de la publicación. Monográfico con el título: 'Geologia: idees i recursos educatius'

Minerals.

Los minerales son sustancias sólidas que forman las rocas y se originan en el interior profundo de la Tierra a elevadas temperaturas. Diferentes combinaciones de elementos forman diferentes minerales, los cuales pueden identificarse por su color, veta, forma, dureza, densidad, brillo. Los minerales han sido extraídos de los metales y piedras preciosas que los contienen, y se han utilizado para la pintura, la cerámica, las joyas e, incluso para dispositivos electrónicos. Al final del libro hay una pequeña bibliografía y direcciones de páginas web.

Effect of minerals on casein micelle stability of cows' milk

The effects of minerals on casein micelle stability of individual cows' milk, throughout a complete lactation, were investigated. Calcium and calcium ions, magnesium, phosphorus, sodium, potassium and citrate contents were analysed, together with the following physical properties of milk; pH, ethanol stability, rennet clotting time and coagulum firmness. There was an inverse non-linear relationship between free calcium ion concentration and ethanol stability (ES; r=0.84). Rennet coagulation time showed a weaker relationship with free calcium ion concentration (r=0.44) but a stronger relationship with pH (r=0.66). In addition, samples containing higher amounts of free calcium ions produced a firmer gel. Citrate in natural samples acts as a stabilizing factor, as it slightly improves milk stability. Potassium, on the other hand, exhibited a negative correlation, but only with rennet clotting time (r=-0.52). Throughout lactation the average values were; free Ca 21 concentration 1.88 mm,, pH 6.63, ES 83.2% and clotting time 13.6 min. The equilibrium relationship between pH and free Ca2+ concentration was investigated by adjusting milk pH from 5.9 to 7.1, using acid and alkali. There was a good inverse linear relationship between pH and log (free Ca 21) for individual milk samples, with a gradient of -0.62 and a standard deviation of 0.042.

Effects of phytate and minerals on the bioavailability of oxalate from food

Phytate and mineral cations are both considered as important dietary factors for inhibiting the crystallisation of calcium oxalate kidney stones in susceptible individuals. In this paper, the phytate and mineral composition of whole bran cereals (wheat, barley and oat) and legumes were determined together with their soluble and insoluble oxalate concentrations in order to investigate the effects on oxalate solubility. The oat bran sample had the highest soluble oxalate concentration at 79 ± 1.3 mg/100 g, while total and soluble oxalate concentrations in the food samples studied range from 33 to 199 mg/100 g and 14 to 79 mg/100 g, respectively. The phytate concentration was in the range from 227 to 4393 mg/100 g and the concentrations of cations were in the range 54–70 mg/100 g for calcium, 75–398 mg/100 g for magnesium, 244–1529 mg/100 g for potassium and 4–11 mg/100 g for iron. Soluble oxalate concentration did not increase in proportion to total oxalate, and the phytate concentration in all foods was sufficient to contribute to an increase in soluble oxalate concentration by binding calcium.

Ordered-defect sulfides as thermoelectric materials

The thermoelectric behaviour of the transition-metal disulphides n-type NiCr2S4 and p-type CuCrS2 is investigated. Materials prepared by high-temperature reaction were consolidated using cold-pressing and sintering, hot-pressing (HP) in graphite dies or spark-plasma sintering (SPS) in tungsten carbide dies. The consolidation conditions have a marked influence on the electrical transport properties. In addition to the effect on sample density, altering the consolidation conditions results in changes to the sample composition, including the formation of impurity phases. Maximum room-temperature power factors are 0.18 mW m-1 K-2 and 0.09 mW m-1 K-2 for NiCr2S4 and CuCrS2, respectively. Thermal conductivities of ca. 1.4 and 1.2 W m-1 K-1 lead to figures of merit of 0.024 and 0.023 for NiCr2S4 and CuCrS2, respectively.

Cobalt-related impurity centers in diamond: electronic properties and hyperfine parameters

Cobalt-related impurity centers in diamond have been studied using first principles calculations. We computed the symmetry, formation and transition energies, and hyperfine parameters of cobalt impurities in isolated configurations and in complexes involving vacancies and nitrogen atoms. We found that the Co impurity in a divacant site is energetically favorable and segregates nitrogen atoms in its neighborhood. Our results are discussed in the context of the recently observed Co-related electrically active centers in synthetic diamond.