Search

Ingestion of soil and dust is a pathway of children’s exposure to several environmental contaminants, including lead, pesticides, and fecal contamination. Empirically based estimates of central tendency for soil consumption by children in high-income countries range from 9 to 135 dry mg/day. Using a Monte Carlo simulation, we modeled the mass of soil directly and indirectly ingested per day by rural Bangladeshi children and identified the parameters that influence the mass ingested. We combined data from observations of direct and indirect ingestion among children with measurements of soil mass on the children’s hands, mother’s hands, and objects to quantify soil ingestion/day. Estimated geometric mean soil ingestion was 162 dry mg/day for children 3–5 months, 224 dry mg/day for children 6–11 months, 234 dry mg/day for children 12–23 months, 168 dry mg/day for children 24–35 months, and 178 dry mg/day for children 36–47 months old. Across all age groups, children placing their hands in their mouths accounted for 46–78% of total ingestion and mouthing objects contributed 8–12%. Direct ingestion of soil accounted for nearly 40% of soil ingested among children 6–23 months old. Sensitivity analyses identified that the parameters most affecting the estimates were the load of soil on the child’s hand, the frequency of hand-to-mouth contacts while not eating, and, for children 6–23 months old, the frequency of direct soil ingestion. In a rural, low-income setting, children’s soil consumption was substantially more than the estimates for children in high-income countries. Further characterizing soil ingestion of children in low-income contexts would improve assessments of the risks they face from soil-associated contaminants.

The initial behavior of colloidal fouling is governed by foulant–clean-membrane interaction (F–M), and its long-term behavior is determined by foulant–fouled-membrane interaction (F–F). Nevertheless, the transitional fouling behavior from F–M to F–F has not been fully understood. This study reports a novel collision attachment (CA)–Monte Carlo (MC) approach, with the stochastic colloid–membrane collision events modeled by MC and the probability of colloidal attachment to the membrane determined by the interplay of flux and the energy barrier arising from colloid–membrane interaction (Emfor F–M and Effor F–F). The long-term membrane flux remains stable for large Ef, whereas severe fouling occurs when both Emand Efare small. Our study reveals the existence of a metastable flux behavior for the combination of large Embut small Ef. The time evolution of flux behavior and colloidal deposition patterns shows a nearly constant flux for an extended period, with the high energy barrier Emretarding initial colloidal deposition. However, accidental random deposition of a colloidal particle could reduce the local energy barrier (toward the smaller Ef), seeding for further colloidal deposition in its vicinity. This initiates an uneven patch-wise fouling and eventually leads to a complete transition to F–F-dominated behavior. The metastable period can be effectively extended by increasing the energy barrier (Emor Ef) or lowering flux, which provides important implications to membrane design and operation.

The impetus for an interconnected, efficient, and adaptive manufacturing system, as advocated by the Industry 4.0 revolution, together with the latest developments in information technology, advanced manufacturing has become a prominent research topic in recent years. One critical aspect of advanced manufacturing is how to incorporate real-time demand information with a manufacturer's resource information, including workforce data and machine capacity and condition information, among others, to optimally schedule manufacturing processes with multiple objectives. In general, optimized manufacturing scheduling is a non-deterministic polynomial-time hard problem. Due to the complexity, scheduling presents a number of challenges to find the best possible solutions. This research proposes an ontology-based framework to formally represent a synchronized, station-based flow shop with a multi-skill workforce and multiple types of machines. Based on the ontology, this research develops a multi-agent reinforcement learning approach for the optimal scheduling of a manufacturing system of multi-stage processes for multiple types of products with various machines and a multi-skilled workforce. By employing a learning algorithm, this approach enables real-time cooperation between the workforce and the machines, and adaptively updates production schedules according to dynamically changing real-time events.

A novel free-standing and flexible electrospun carbon–silica composite nanofibrous membrane is newly introduced. The characterization results suggest that the electrospun composite nanofibers are constructed by carbon chains interpenetrated through a linear network of 3-dimensional SiO2. Thermogravimetric analysis indicates that the presence of insulating silica further improve the thermal resistance of the membrane. Additionally, the mechanical strength test shows that the membrane’s toughness and flexibility can be enhanced if the concentration of SiO2is maintained below 2.7 wt %. Thermal and chemical stability test show that the membrane’s wettability properties can be sustained at an elevated temperature up to 300 °C and no discernible change in wettability was observed under highly acidic and basic conditions. After surface-coating with silicone oil for 30 mins, the composite membrane exhibits ultra-hydrophobic and superoleophilic properties with water and oil contact angles being 144.2 ± 1.2° and 0°, respectively. The enhanced flexibility and selective wetting property enables the membrane to serve as an effective substrate for separating free oil from water. Lab-scale oil–water separation test indicates that the membrane possesses excellent oil–water separation efficiency. In addition, its inherent property of high porosity allows oil–water separation to be performed in a gravity-driven process with high-flux. We anticipate that this study will open up a new avenue for fabrication of free-standing carbonaceous composite membrane with tunable flexibility for energy efficient and high-throughput production of clean water.

Porous TiO2hollow aggregates have been synthesized on a large scale by means of a simple hydrothermal method without using any templates. The as‐prepared products were characterized by means of field emission scanning electron microscopy, XRD, TEM, nitrogen adsorption, UV/Vis diffuse reflectance spectroscopy, and FTIR spectroscopy. The photocatalytic activity of the aggregates was demonstrated through the photocatalytic degradation of Rhodamine B. Structural characterization indicates that the porous TiO2aggregates are 500–800 nm in diameter and display mesoporous structure. The average pore sizes and BET surface areas of the aggregates are 12 nm and 168 m2g−1, respectively. Optical adsorption investigations show that the aggregates possess an optical band‐gap energy of 3.36 eV. The as‐prepared products were substantially more effective photocatalysts than the commercially available photocatalyst P25. The dye degradation rate of the porous TiO2hollow aggregates is more than twice that of P25. The high photoactivities of the aggregates can be attributed to the combined effects of several factors, namely, large surface areas, the existence of mesopores, and the high band‐gap energy. In addition, the as‐prepared products can be easily recycled.

A systematic investigation of the relationship between chlorine exposure of a thin film composite crosslinked polyamide membrane (LE membrane, FilmTec©) and changes in membrane performance (water flux and salt rejection) is discussed here. Performance change of crosslinked polyamide membranes due to chlorination depended on pH and concentration of chlorine in the soaking bath. Membranes chlorinated at low pH and high chlorine concentration showed flux decreases at an early stage of filtration and then increases with filtration time. On the other hand, membranes chlorinated at high pH and low chlorine concentration showed flux increases at an early stage and then decreases with filtration time. Performance of chlorinated polyamide membranes was determined by the balance between rearrangement of polymer chains and the distortion of the chains due to chlorination. A conceptual model of performance change was proposed consistent with the chlorination of polyamide membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5895–5902, 2006

Experimental data for carbonate adsorption onto synthetic goethite, spanning 3 orders of magnitude in carbonate concentrations, were simulated using the triple-layer surface complexation model (TLM). A single set of TLM parameters successfully described the adsorption behavior versus pH over the concentration range obtained from closed and open CO2conditions. An optimization analysis was performed for all possible interfacial charge configurations using FITEQL3.2. The results yielded an optimum charge allocation of 0 and −1 in the 0- and β-planes, respectively, which suggests a monodentate complex most probably in an inner-sphere configuration (SOCOO−β). Fourier transform infrared (FTIR) spectroscopic measurements on open systems at atmospheric PCO2confirmed this result by showing a clear peak split (155 cm−1) of the ν3C–O asymmetric stretching frequency of surface-bound carbonate, consistent with that reported for monodentate Co(III)–carbonato inner-sphere solution complexes. An additional Na+–ternary complex (SOCOONa) was invoked in the TLM construct to improve simulations of the enhanced carbonate adsorption occurring at high ionic strength and high pH. The model was successful in predicting carbonate adsorption behavior under diffferent conditions than it was calibrated for. Projections for equilibration at higher PCO2's (1–10%) than those used in this work show the potential for carbonate sorption densities of up to 2.5–3 μmol/m2.

Laboratory experiments were conducted with well‐characterized minerals to test the applicability of selective extraction schemes for Se and As partitioning in soils and sediments. Two specific steps were tested: the reductive dissolution of amorphous iron oxides and the oxidation of organic material. Selenium and As associated with amorphous iron oxides were usually not found in solution after reductive dissolution, due to readsorption onto other minerals unaffected by the extractant. Oxidants intended to dissolve organic material also oxidized Se(IV) adsorbed on a mineral to Se(VI), causing the release of Se(VI) to the extractant solution. The selective extraction schemes which are currently available do not appear to produce reliable results for Se and As partitioning among sediment components.

CHEMICAL reactions of the sort that might have produced peptides from amino acids on the primitive Earth can be catalysed by kaolinite1, montmorillonite2, hydroxyapatite3–5and condensed phosphates6–8Hydroxyapatite has been suggested as a source of condensed phosphates because it yields pyrophosphate when reacted with cyanate9. For this reason, and because phosphates polymerize amino acids, we have investigated whether peptide formation can be enhanced by cyanate added to hydroxyapatite or orthophosphates. After we reported our preliminary results (at the national meeting of the American Chemical Society in Washington DC in September 1971), Choughuley et al.10confirmed that orthophosphates catalysed the condensation of amino acids to peptides.

Porous basketry-like TiO2(B) microspheres consisting of nanowires were fabricated via hydrothermal and spray-drying process. The calcined microspheres exhibited effective photocatalytic performance on photodegradation of organic pollutant. In addition, it was very easy to recycle the TiO2(B) nanowire microspheres for reuse.