Secondary minerals could be effective scavengers of toxic arsenic (As) and thallium (Tl). In environments polluted by mining, these elements are abundant both in acid rock/mine drainage scenarios, as ...well as in carbonate-buffered environments. In this study we have investigated the behavior of As and Tl during weathering in mine waste dumps and an associated technosol sample from the Crven Dol locality (Allchar Tl–As–Sb–Au deposit, North Macedonia) contaminated with up to 142 g kg−1 of As and 18 g kg−1 of Tl, making it an As- and Tl-extreme environment. We identified As and Tl reservoirs and discuss their difference from those observed in other naturally As- and Tl-rich environments. The pore waters show high concentrations of As (up to 196 mg L−1) and Tl (up to 660 μg L−1). Mild extractions mobilized up to 46% of the total Tl and 11% of the total As, indicating that a large amount of these toxic elements is weakly bound and can be easily mobilized into the environment. Apart from the recognition of Tl storage in several secondary phases (mainly as Tl(I) in members of the pharmacosiderite and jarosite groups, as well as Mn oxides, but also as very minor Tl(III) in other secondary phases), this study also provides the first evidence of Tl uptake by previously unknown thallium arsenate phases (with Tl:As ratios ∼ 2 and 4), detected in carbonate-buffered (near-neutral pH) As- and Tl-rich technosols and waste dumps. These results indicate the need for further studies on Tl speciation in extremely As- and Tl-rich environments.
Display omitted
•We study Tl and As retention in secondary minerals.•Pronounced Tl-concentrations: up to 18 g kg−1.•Tl is precipitated mostly as novel thallium arsenates and as dorallcharite.•Significant amount of As and Tl is bound weakly to solids.•Large quantity of As and Tl can be easily mobilized into the pore water and biota.
The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO2) addition on the physical, mechanical, ...thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5wt% nano SiO2 as additives. Specimens were heated up to 1650°C for the 3h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and thermo-mechanical (flexural strength at 1200°C) measurements. XRD and SEM/EDS analysis were done to study phases and microstructure analysis of the fired samples, respectively. Results showed that by adding up to 2.5wt% nano-SiO2, due to the formation of CaO·MgO·2SiO2 (Diopside), 2CaO·MgO·2SiO2 (Akermanite), and CaO·MgO·SiO2 (Monticellite) phases, physical and mechanical properties were enhanced. But the highest flexural strength value is achieved for 1wt% nano-SiO2 containing sample.
Objective To examine the effect of early initiation of caffeine therapy on neonatal outcomes and characterize the use of caffeine therapy in very low birth weight (VLBW) infants. Study design We ...analyzed a cohort of 62 056 VLBW infants discharged between 1997 and 2010 who received caffeine therapy. We compared outcomes in infants receiving early caffeine therapy (initial dose before 3 days of life) and those receiving late caffeine therapy (initial dose at or after 3 days of life) through propensity scoring using baseline and early clinical variables. The primary outcome was the association between the timing of caffeine initiation and the incidence of bronchopulmonary dysplasia (BPD) or death. Results We propensity score–matched 29 070 VLBW infants at a 1:1. Of infants receiving early caffeine therapy, 3681 (27.6%) died or developed BPD, compared with 4591 infants (34.0%) receiving late caffeine therapy (OR, 0.74; 99% CI, 0.69-0.80). Infants receiving early caffeine had a lower incidence of BPD (23.1% vs 30.7%; OR, 0.68; 95% CI, 0.63-0.73) and a higher incidence of death (4.5% vs 3.7%; OR, 1.23; 95% CI, 1.05-1.43). Infants receiving early caffeine therapy had less treatment of patent ductus arteriosus (OR, 0.60; 95% CI, 0.55-0.65) and a shorter duration of mechanical ventilation (mean difference, 6 days; P < .001). Conclusion Early caffeine initiation is associated with a decreased incidence of BPD. Randomized trials are needed to determine the efficacy and safety of early caffeine prophylaxis in VLBW infants.
•The DOL effect of wood in tension perpendicular to grain is investigated.•DOL models are calibrated to predict the long-term strength.•DOL value in national codes is applicable to wood loaded ...perpendicular to grain.•Relative creep strain of wood loaded perpendicular to the grain is reported.•The DOL effect on the modulus of elasticity is presented.
In this study, both short-term and long-term tests in tension perpendicular to grain on Northeast China Larch small clear specimens taken from glulam were conducted, in which the specimens for short-term test and the specimens for long-term test were treated as matched samples that followed the same strength distribution. The DOL effect was determined as the ratio of the applied stress of a failed specimen from the long-term test to the strength of the matching specimen of the same percentile from the short-term test. It was found that the DOL effect was more severe than that predicted by the Madison Curve for the duration shorter than one hour or so and less severe for the duration between one hour and one year by the end of the long-term test. Also, the test result showed that the MOE perpendicular to grain decreased slightly after long-term loading, but the decrease was less severe than the loss of the strength. The deformation factor of creep perpendicular to grain was found to be 2.17, which is close to the deformation factor of OSB in Service Class 1 as specified in Eurocode 5. Furthermore, the Foschi and Yao DOL model and the Nielsen DOL model were calibrated with the test data and the long-term strength can thus be predicted by the calibrated DOL models.
To meet the severe operating conditions in the metal industry, more thorough design and operational assessments about those implemented electric motors for specific applications must be emphasized. ...With its inherent robust structure, the induction motor is generally adopted to fulfill such driven objective. However, due to global warming and energy conservation concerns, those strictly enforced regulations have potentially increased the complexity and cost of high efficiency induction motor. Since the synchronous reluctance motor (SynRM) has relatively simpler structure with no copper loss in its rotor, it is a very attractive alternative for accomplishing the high-efficiency objectives of those common hoist, punch, roller, and pump applications. In addition, to eliminate drive circuits that can further reduce the overall system construction costs, the rotor barriers of the SynRM can be equipped with direct-on-line capability (DOL_SynRM) with conductors filled in. The impacts to the operational performance of these DOL_SynRMs for different applications will all be thoroughly investigated. The competitive high-efficiency DOL_SynRMs for driving various metal industry equipment can thus be offered.
Direct-on-line synchronous reluctance machines combine the characteristics of induction machines and synchronous reluctance machines. Saturation of core materials, the eddy currents, and the ...asymmetry of the rotor core and cage make it difficult to predict which kind of loads a machine can synchronize. In this paper, the start-up of a direct-on-line synchronous reluctance machine is analyzed with a magnetic field decomposition that makes it possible to quantify and isolate forces between any two distinct parts of an electric machine using a transient time-stepping finite element field solution. The results show explicitly which portion of the torque is produced by the rotor core and which by the rotor cage. Compared with conventional average torque analyses (also known as pseudo-constant-speed or quasi-steady-state analyses) used to distinguish between the torque on the rotor core and cage, the proposed method makes no assumptions on the state of the machine. This results in a more detailed view of the starting transient.
To understand the effect of chemical strengthening process on irregular geometry, a partially thinned glass substrate was strengthened according to the ion-exchange conditions, and the strengthening ...properties and the dimensional changes of the partially thinned glass were analyzed using a surface stress meter and a 3-dimensional analyzer. The results revealed that the compressive stress (CS) measured at a thin area of the glass substrate having different thicknesses was affected by the CS of a thick zone, and consequentially the CS of the thin zone was bigger than that measured at a same thickness glass. It was also found that the dimensional changes across the thin zone after chemical strengthening were relatively big, and as a result, it caused a physical deformation on the thin area due to the interference in the thick area.
The operation of a lithium-sulfur (Li-S) battery involves the transport of Li
+
ions and soluble sulfides mostly in the form of solvated ions. Key challenges in the development of Li-S battery ...technology are the diffusion of Li
+
in micropores filled with sulfur and eliminating the “shuttling” of polysulfides. Ion dimensions in solvated and desolvated forms are key parameters determining the diffusion coefficient and the rate of transport of such ions, while constrictivity effects due to the effect of pore size compared to ion size control both transport and filling of the pores. We present molecular simulations to determine the solvation parameters of electrolyte ions and sulfides S
2
2−
, S
4
2−
, S
6
2−
, and S
8
2−
in two different electrolyte systems: LiTFSI in DOL/DME and LiPF
6
in EC/DMC. The calculated parameters include the coordination number and the geometrically optimized model and dimensions, using the van der Waals surface approach, of the solvated and desolvated ions. The desolvation energy of the electrolyte ions is also calculated. Such data is useful for the modeling and design of the pore sizes of cathode host materials to be able to accommodate the different sulfides while minimizing their “shuttling” between cathode and anode.
PDF
