Modeling copper partitioning in surface waters

Suspended particulate matter from the surface waters of the Susquehanna, Christina and Brandywine Rivers was collected by tangential flow filtration to study copper partitioning. Copper adsorption increased with an increase of suspended particles and decreased with low pH values or with an increase of dissolved organic matter. Effects of particulate organic matter on copper distribution between suspended particulate and solution phases were studied using modified aluminum oxide. An increase of particulate organic matter enhanced copper adsorption. Copper adsorption per mass of particulate organic carbon was similar for the different sources of suspended particles. A model, based on copper adsorption on particles and complexation with dissolved organic matter, was developed to assess copper partition coefficient as a function of the easily measurable water quality parameters: pH, alkalinity, dissolved organic carbon and particulate organic matter. The partitioning model was calibrated on pH edge data using suspended particles collected from the three rivers. The model was verified using partitioning data as a function of dissolved organic matter. The model adequately describes the system containing natural suspended solids collected from the surface waters.     

Internal migration and wages of Italian university graduates*

In this paper, we estimate wage gains due to geographic mobility of Italian university graduates three years after graduation. By means of a matching procedure we quantify wage premia associated with the choice of studying far from home, moving after graduation and moving back home after graduation. We find evidence of large heterogeneity in the returns to different migration patterns. The results show large gains for those who move after graduation and smaller gains for those who migrate to study. Conversely, those who choose to go back home after having studied in regions different from that of origin suffer small losses. Our findings are robust to a finer definition of mobility and to the subsample of individuals originating from the South.     

Hydrogeological features of a rocky massif to be used as a nuclear repository

The Sierra del Medio rocky massif is situated in the central west sector of a probably closed Cainozoic sedimentary basin. Sierra del Medio behaves as an area having a positive relief which receives rainfall and spreads it over the superficial smaller basins around. From the geological and geophysical points of view it is believed that the massif is separated from the adjacent basin water bearing formations by fractures belonging to the direct type. It is formed by Palaeozoic migmatites of granitic to tonalitic composition intruded by acidic, mesosilicic and basic dikes. Ectinite xenoliths can also be found. The different hydrogeological units in the rocky massif under study were defined preliminarily in geological, geophysical, mechanical and chemical detailed studies. Tentative isopiezometric curves are shown and geophysical profiles are analyzed.     

Illicit drugs, a novel group of environmental contaminants

It is now well established that residues from therapeutic drugs consumed by humans can end up, through the sewage system, in the surface water of populated areas. Given that the global production of major illicit drugs is comparable to that of widely used pharmaceuticals, we tested for the presence of drugs of abuse (cocaine, opioids, amphetamines and cannabis derivatives), some related opioid pharmaceuticals (codeine and methadone) and/or their metabolites in Italian and British surface waters. Having identified residues of all major drugs of abuse in raw and treated urban wastewater, we now measured their levels in several rivers and lakes by a selective multi-residue assay based on liquid chromatography-tandem mass spectrometry. Recoveries in surface water were generally higher than 80%, with overall variability of the method lower than 10%. LODs were generally lower than 0.2 ng/L, and LOQs were lower than 0.6 ng/L, with few exceptions. Many of the tested substances were found in both rivers and lakes, at concentrations ranging from high pg/L to high ng/L, with loads in rivers in the range of tenths to hundreds of grams per day. Our data indicate that residues of drugs of abuse have become widespread surface water contaminants in populated areas. Since most of these residues still have potent pharmacological activities, their presence in the aquatic environment may have potential implications for human health and wildlife.     

Hydrogen embrittlement of duplex stainless steel under cathodic protection in acidic artificial sea water in the presence of sulphide ions

By slow strain rate technique, hydrogen embrittlement (HE) of a 2205 duplex stainless steel was studied in deaerated acidic (pH 6.5) artificial sea water, in the absence and in presence of sulphide ions (1-30 ppm). Strain rate tests (1 × 10⁻⁶ s⁻¹) were performed on specimens polarized at −0.9; −1.0 and −1.2 V_SCE at 25 ± 0.1 °C. HE was evaluated by R, the ratio between the % elongation to fracture in the aggressive solution and in air.Duplex stainless steel were subjected to HE in acidic artificial sea water at −0.9 V_SCE. HE increased at −1.0 V_SCE but it was reduced at −1.2 V_SCE. This decrease was attributed to the influence of a calcareous deposit.Sulphide ions at 1 ppm were sufficient to stimulate HE of duplex stainless steel. The higher the sulphide amount and the more negative the cathodic potential, the higher HE was. In the presence of S²⁻, the shielding effect of the calcareous deposit was not evident.     

Consignment stock inventory policy: methodological framework and model

We consider the hierarchical coordinated control of a multi-procedure conveyor-serviced production station system with flexible stations deployed between adjacent procedures, which includes a dynamic intra-procedure switching control of the flexible stations for the goal of balancing different procedures and a dynamic inter-procedure production coordination of all of the stations within each procedure. It is complicated in terms of modelling and optimisation, and thus, it is difficult to find a solution using numerical methods; as a result, we refer to model-free learning optimisation methods. First, we establish a neuro-dynamic programming algorithm by utilising cerebellar model articulation controllers (CMACs) to approximate state-action values at an upper hierarchy. Second, according to the reaction-diffusion phenomenon, we combine a Wolf-PHC algorithm with a local information-interaction scheme to learn look-ahead control policies at the lower hierarchy. Simulation results show that, compared with traditional Q-learning and the backward Q-learning based Q-learning, our proposed CMAC-based learning optimisation methods have the advantages of yielding a higher processing rate and having a faster optimisation speed with a lower storage requirement.     

CNN‐based architecture for real‐time object‐oriented video coding applications

This paper presents a new CNN‐based architecture for real‐time video coding applications. The proposed approach, by exploiting object‐oriented CNN algorithms and MPEG encoding capabilities, enables low bit‐rate encoder/decoder to be designed. Simulation results using Claire video sequence show the effectiveness of the proposed scheme. Copyright © 2005 John Wiley & Sons, Ltd.     

Assessment of transduction of Escherichia coli Stx2-encoding phage in dairy process conditions

In the environment, bacteriophages are regarded as natural vector for the transmission of Shiga-toxin genes among Shiga-toxin Escherichia coli strains. The possibility of transduction has been noticed in intestinal tract of various animals but experimental observations on this phenomenon in food processes are lacking. To investigate the transduction in milk at different temperature profiles and cell concentrations, an experimental plan including two different Stx₂-phages (?GV2412 and ?L34), induced respectively from E. coli O157:H7 181181/2 and E. coli O157:H7 EC34, and two recipient E. coli strains (CNCTC 6896, WG5) was performed. The donor strains were generated by lysogenization of CNCTC 6896 with ?GV2412 and ?L34 respectively. Spectinomycin resistance gene (aadA) was inserted into stx₂ operon in order to select transduced cells. Transductants were never observed at 4 °C up to 24 h, whereas after a treatment at 37 °C for 2 h and at 25 °C for 22 h they were detected in 67% of the trials with a ratio of transduction varying from 1.13 10^− 6 to 7.87 10^− 8. A treatment at 48 °C for 2 h followed by a second step at 25 °C for 22 h showed an occurrence of transduction events in only 19% of cases with a ratio of transduction varying from 2.22 10^− 7 to 2.67 10^− 8. The generation of transductants and the spontaneous induction of phages in milk were not affected by initial or final concentration of the donor or recipient strains. The results show that transduction phenomenon occurs when the cells are metabolically active and it does not take place at low temperatures. Therefore, the maintenance of the chilling chain proved to be a main factor to prevent the spread of Stx-genes in dairy processes.     

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats (installed in series) to be used as permeable reactive barriers for delivery of oxidants and reductants to induce sequential bioremediation of ammonium-contaminated groundwater (approximately 120mg L(-1) NH4+-N), without bioaugmentation. The strategy was for the first group of polymer mats to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/ nitrate as the groundwater moved past and for the second group of polymer mats to deliver hydrogen or ethanol, to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. Once purging of the first polymer mat commenced, ammonium concentrations decreased downgradient from the polymer mats. Nitrification rates increased and stabilized over the 6-month experiment, with stable nitrification half-lives in the range 0.07-0.25 days. Nitrification most likely occurred in a biologically active zone at the polymer wall/aqueous interface. With hydrogen delivery via the polymer mats, a denitrification half-life (nitrate plus nitrite removal) of 3.5 days was induced. Denitrification rates were significantly enhanced when ethanol was delivered via a polymer mat, with denitrification half-lives in the range of 0.12-0.34 days. Nitrification/ denitrification rates were maintained for groundwater flow rates up to 300 m yr(-1), suggesting oxygen and ethanol delivery rates via the polymer mats were sufficient not to limit nitrification or denitrification. In soil columns, the polymer mat delivery system provided an effective and reliable technique for delivery of oxygen and hydrogen or ethanol for sequential nitrification/denitrification of ammonium-contaminated groundwater. Scale-up of this concept to a field pilot-scale is currently underway.