Arsenic stability in arsenopyrite-rich cemented paste backfills: a leaching test-based assessment

Arsenic (As) is a toxicant in tailings from sulphur deposits. It represents an environmental risk because of its high solubility. Tailings can be mixed with water (typically 25%) and a low proportion of hydraulic binder (3-7%) to produce a cemented paste backfill (CPB), stored in underground mine openings. CPB is a tailings storage technique, but it could also provide environmental advantages by stabilization of polluting elements such as As. Tailings from Casa Berardi mine (QC, Canada) contain As (3800 ppm), mainly in arsenopyrite form. For this study, three different CPBs were synthesized in laboratory using Casa Berardi tailings and three different binders. These pastes were submitted to various leaching tests after 28 days of curing. The results indicate that As is released at higher concentration for a fly ash-based CPB than for slag- and Portland cement-based CPB. However, at lower pH, As is better stabilized in fly ash-based samples. These differences can be explained by a variation of solubility of As-compounds in each CPB. Several mechanisms of As release occur, as diffusion and/or dissolution/precipitation. The accelerated weathering test results show that sulphide reactivity is buffered by the neutralizing minerals contained in CPB, and influence the As release behaviour by decreasing the oxidation of As-bearing sulphides.     

The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes

Abstract: The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh‐cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L‐values and lower a‐values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L‐values, lower a‐values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh‐cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh‐cut potatoes along with NatureSeal®'s PS‐10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh‐cut potato products.     

Behaviour of Grade 8.8 bolts under natural fire conditions—Tests and model

Recent full-scale experimental tests performed on steel and composite structures have demonstrated that the presence of tensile forces in axially-restrained beams during the cooling phase of a fire could lead to bolt failures. In order to understand this observation and design structures that are not prone to such a failure mode, it is essential to have a deep knowledge of the material behaviour of all the components, including bolts, during both the heating and cooling phase.In the present article, the test set-ups and the results of the tensile and shear tests performed at the Centro Sviluppo Materiali (Italy) on Grade 8.8 bolts under heating-cooling cycles are described.Then, material laws are defined for characterising the mechanical behaviour of Grade 8.8 bolts under heating and cooling phases. These laws account for the non-reversibility of the mechanical properties of Grade 8.8 bolts.     

Testosterone and occupational choice: Actors, ministers, and other men.

Occupational differences in testosterone concentrations, focusing on actors and ministers, were explored in 3 studies. The 1st examined salivary testosterone in 7 occupational groups and an unemployed comparison group and found actors and football players higher than ministers but no other significant differences. The 2nd examined salivary testosterone in 2 kinds of actors (stage actors and comedians) and 2 kinds of ministers (pastoral ministers and missionaries) and found actors high and ministers low but no differences between subgroups within each occupation. The 3rd examined serum testosterone in entertainers and ministers in a archival sample of military veterans and found entertainers high and ministers low. The results are interpreted in terms of dominance and antisocial tendencies, with the conclusion that these variables are complex and can affect occupational preference in subtle ways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Substituting Symbol Search for Coding on the WISC-III: Canadian normative tables for Performance and Full Scale IQ scores.

A. S. Kaufman (1994) recommends that the Symbol Search, an optional subtest to the WISC-III, be substituted for Coding in the calculation of WISC-III Performance and Full Scale IQ scores. Conversion tables have been published for use with American norms. The authors provide conversion tables for the Canadian-normed WISC-III. The standardization sample consisted of a representative group of 1,100 English-speaking Canadian children. The conversion tables are provided. These tables allow Canadian WISC-III examiners to substitute Symbol Search for Coding in the calculation of the Performance and Full Scale IQ scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maximum likelihood estimation of pseudo-stoichiometry in macroscopic biological reaction schemes

Identification of pseudo-stoichiometric (or yield) coefficients is of primary importance for building a bioprocess model. In most of the applications, the estimation of these coefficients has to be performed without any knowledge of the kinetics and on the basis of a few experiments for which noisy discrete measurements of component concentrations are available. This paper proposes maximum likelihood estimators which are able to deal with measurement errors on all the signals, at each sampling time (including the initial one) and with intrinsic sign constraints on the parameters. This kind of realistic hypotheses exclude the use of the usual (weighted) least-squares estimators. The maximum likelihood estimators are proved to be unbiased (provided a first-order approximation) and their estimation error covariance matrix can be computed (at the same level of first-order approximation). The solutions are proposed in a very general framework, dealing with cell cultures (of bacteria, yeasts or animal cells) performed in stirred tank (continuous, semi-batch or batch) reactors, and without any a priori knowledge on the kinetics. The use of the estimators and their statistical properties are illustrated in a simulation case study (fed-batch bacterial cultures) and in a real case one (batch animal cell cultures).     

Environmental Legionella Assessment in Office Buildings Of Continental United States

An environmental assessment of Legionella bacteria was conducted in five office buildings in the continental United States where no legionellosis was reported. The purpose of this investigation was to (i) determine the presence of Legionella bacteria in potable and non-potable water systems, (ii) provide a baseline information for management, and (iii) evaluate the effectiveness of the remedial actions taken. Water samples were collected from all possible water sources in surveyed buildings. The samples were analyzed by both direct fluorescent antibody microscopy (DFA) and the bacterial cultural method for the presence of Legionella species. Legionella bacteria were detected in some samples collected from various water distribution systems in the buildings. Remedial action was taken to eliminate these bacteria, and case-by-case results are presented.     

Fault detection and isolation for unstable linear systems

In the design of a residual generator for an unstable plant, the unstable modes are made unobservable from the residual vector. We point out that this cannot be achieved in practice due to the discrepancy between the estimated model and the “true” plant model. Hence, we deduce that it is not possible to design a residual generator for an unstable plant, unless it is stabilized by an adequate controller. As a by-product, we provide expressions which can be used to quantify the effect of modeling uncertainties on the performance of a residual generator. The factorization approach to control theory is used for the developments     

Water,Energy and Environment Nexus: The California Experience

The paper addresses the local and inter-state connections between water, energy and the environment. Using California and the western USA as a case study, the paper highlights the difficulties of balancing the needs of diverse stakeholders and protecting valuable resources while providing reliable and safe supplies of both water and energy to agricultural, industrial and residential customers. The investigation of these complex relationships is necessary to inform local and national policy decisions regarding the management of water, energy and the environment.     

Gender differences in partner violence in a birth cohort of 21-year-olds: Bridging the gap between clinical and epidemiological approaches.

This study describes partner violence in a representative sample of young adults. Physical violence perpetration was reported by 37.2% of women and 21.8% of men. Correlates of involvement in severe physical violence differed by gender. Severe physical violence was more strongly associated with unemployment, low educational attainment, few social support resources, polydrug use, antisocial personality disorder symptoms, depression symptoms, and violence toward strangers for men than for women. Women who were victims of severe physical violence were more likely than men who were victims to experience symptoms of anxiety. The findings converge with community studies showing that more women than men are physically violent toward a partner and with clinical studies highlighting violence perpetrated against women by men with deviant characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)