Antimony Mobilization through Two Contrasting Gold Ore Processing Systems,New Zealand

Antimony, a toxic metalloid similar to arsenic, is present at variable levels in most gold-bearing rocks. Antimony is soluble in the surface environment, so antimony (Sb) mobilization in mine waters is an environmental issue around gold mines. The Reefton gold mine was originally developed in gold-bearing quartz veins; Sb concentrations were low (<100 mg/kg) compared to arsenic (As) concentrations (>1,000 mg/kg), and the mine waters had low dissolved Sb (<0.1 mg/L). A second stage of gold mineralization at Reefton involved brecciation and cataclasis of quartz veins and wall rocks, with addition of stibnite (Sb₂S₃). Processing of this ore has resulted in higher dissolved Sb in mine waters (0.1–1 mg/L), even after water treatment that removes most dissolved As (to 0.01 mg/L) by adsorption to suspended iron oxyhydroxide. Competition between As and Sb for adsorption sites on iron oxyhydroxide particles may have resulted in partial exclusion of the more weakly adsorbed Sb. The high rainfall (2,000 mm/year) at Reefton ensures adequate dilution of mine waters after discharge. The Macraes gold mine has no stibnite, and most Sb is in solid solution in the abundant arsenopyrite (Sb up to 2,000 mg/kg). Pit waters have both Sb and As dissolved up to 0.1 mg/L, partly because of evaporative concentration in a low-rainfall environment. Macraes tailings waters have high As (up to 3 mg/L) but negligible Sb (<0.001 mg/L). Reefton mine gold-bearing concentrate, containing stibnite, is transported 700 km to be processed by autoclave oxidation and cyanidation at the Macraes mine. This introduction of additional Sb to the Macraes site substantially increases the Sb content of the process stream periodically. Tailings from this process have up to 3 wt% Sb, dispersed through As-rich iron oxyhydroxides that are formed in the autoclave. The Sb-rich tailings are strongly diluted (approximately 100:1) by the Macraes tailings, and adsorption of Sb to iron oxyhydroxides in the tailings piles ensures that there has been no increase in the Sb content of the tailings water since the Reefton concentrate has been added at Macraes.     

Analysis of electricity consumption: a study in the wood products industry

This paper evaluates the effect of industry segment, year, and US region on electricity consumption per employee, per dollar sales, and per square foot of plant area for wood products industries. Data was extracted from the Industrial Assessment Center (IAC) database and imported into MS Excel. The extracted dataset was examined for outliers and abnormalities with outliers outside the quantile range 0.5–99.5 dropped from the analysis. A logarithmic transformation was applied to eliminate the skewness of the original data distributions. Correlation measurements indicated a moderate association between the response variables; therefore, a multivariate analysis of variance test was performed to measure the impact of the three factors: industry type, year, and region, simultaneously on all response variables. The results indicated some effect associated with all three factors on the three measures of electricity consumption. Subsequently, univariate ANOVA tests were conducted to determine the levels of the factors that were different. Most levels of industry type were associated with significantly different energy consumption, an expected result since some of the industries are more energy intensive than others. The industries in Standard Industry Code (SIC) 2493 (reconstituted wood products) are the groups with the highest electricity consumption with means of 38,096.28 kWh/employee, 0.86 kWh/sales, and 154.14 kWh/plant area while industries grouped in SIC 2451 (mobile homes) have the smallest consumption with means of 6811.01 kWh/employee, 0.05 kWh/sales, and 9.45 kWh/plant area. Interestingly, differences in regional consumption were found to be linked to the proportion of industry types by region. Data analysis also indicated differences in electricity consumption per employee for the factor year, but for the other response variables, no differences were found. These main results indicate that industries in the wood products sector have different electricity consumption rates depending on the type of manufacturing processes they use. Therefore, industries in this sector can use these comparisons and metrics to benchmark their electricity consumption as well to understand better how electricity costs might vary depending on the region they are located.     

Lipids in vascular function

Physiological and pathological vascular responses depend on the action of numerous intercellular mediators, ranging from hormones to gases like nitric oxide, proteins, and lipids. The last group consists not only of the different types of lipoproteins, but also includes a broad array of other lipophilic signaling molecules such as fatty acids, eicosanoids, phospholipids and their derivatives, sphingolipids and isoprenoids. Due to space limitations, it is impossible to discuss all the vascular effects of lipophilic mediators or compounds. Therefore, we will focus on one of the most important lipid-mediated diseases, atherosclerosis. Lipoproteins and especially their native or oxidized lipid compounds affect vascular function in many different ways, and these effects do not only modulate atherogenesis but are of paramount physiological and pathophysiological importance in other diseases, such as inflammation, tumor metastasis, or normal wound healing.     

Dodecylhydroxydiphosphonic Acid for Solvent Extraction

Abstract

The extraction behavior of Zn(II) and Cu(II) in acetate media has been investigated using dodecylhydroxydiphosphonic acid, DHDPA, which was previously synthesized and characterized. The extraction of both cations was carried out in different media with the addition of CH₃COOH, HCl or H₂SO₄ at different pH. The maximum extraction yield of 80% for zinc, was obtained in one step after the addition of sulfuric acid at pH_i=5.5 and for copper after the addition of 10 mg of sodium acetate. The authors plan additional tests using polar solvents.     

An Innovative Tree Gradient Boosting Method Based Image Object detection from a Uniform Background Scene

Object detection is a wide area problem domain in the field of computer and machine vision. Complex background adds challenge and error margin as well to the problem significantly lot algorithms for object detection are hard to comply with occlusion and pixel bending moment affect. In this paper a highly robust algorithm ORBTRIAN for a less resolution image has been proposed and implemented using ORB detection with gradient boosting machine learning algorithm. The work has been compared with Adaboost and Surf based technology. The analysis shows 3.8% increase in performance of earlier model. The feature points extracted from ORB method are further processed to reduce the processing further. Only those points are selected which are triangularly farthest from centroid of it and only 1 point of feature selected. Thus the result is around 28%, much faster than earlier computation. The tree based GB has been implemented in this algorithm. With more number of feature points more classes need to be recognized and hence the computations performed is required an unreasonable amount of effort and time. So some nearby classes are assigned at same level using our algorithm to reduce the number of tree nodes. Overall performance of the proposed algorithm shows a significant increase in efficiency in computation time.     

Spin injection in n-type resonant tunneling diodes

We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X⁻). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to −88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.