Hydrodynamic effects on the performance of an electrochemical reactor for destruction of copper cyanide—Part 1: in situ formation of the electrocatalytic film

An electrochemical reactor with stainless-steel electrodes was used for cyanide destruction and copper electrodeposition from dilute wastewater. With mechanical stirring, pumping or gas sparging, in situ deposition of a Cu oxyhydroxide film occurred on the anode at potentials vs. AgCl/Ag and had electrocatalytic properties for oxidation of cyanides. The Cu^II/Cu^I ratio in the electrocatalytic film was found to vary with the hydrodynamic conditions. The minimum mechanical energy dissipation, ranging from 1.5 to , necessary to create sufficient turbulence for film formation, was of a similar order of magnitude for all three means of transport enhancement. However, shear rates and shear stresses at the anode resulted in shearing of the film from the stainless-steel support.     

Fractional convolution quadrature based on generalized Adams methods

In this paper we present a product quadrature rule for Volterra integral equations with weakly singular kernels based on the generalized Adams methods. The formulas represent numerical solvers for fractional differential equations, which inherit the linear stability properties already known for the integer order case. The numerical experiments confirm the valuable properties of this approach.     

Effect of melt annealing on the phase structure and rheological behavior of propylene–ethylene copolymers

The morphological and rheological properties of a commercial propylene‐ethylene copolymer (PEC) and a series of blends with different concentrations of poly (ethylene‐co‐propylene) are investigated. The blends are prepared mixing PEC with fractions obtained from it by solvent extraction. The phase structure of samples exposed to different thermal and mechanical histories was analyzed using scanning electron microscopy. The linear viscoelastic properties of the molten polymers were measured using different test sequences that include dynamic frequency and time sweeps. The phase structure of most blends changes dramatically with time when the polymers are kept in the molten state due to the coalescence of the domains. For example, the initial morphology of PEC which presents domains of ～1 μm diameter changes to regions of more than 10 μm of average diameter after 90 min at 178°C at rest. Coincidentally, the dynamic moduli of the blends change during annealing reaching values that depend on the mechanical history. For example, the elastic modulus of PEC increases ～32% during a dynamic time sweep of 45 min using a frequency of 0.1 s^?1, while it decreases ～18% when a frequency of 1 s^?1 is applied. Moreover, the modulus measured at 0.1 s^?1 of samples annealed at rest during 45 min is ～58% larger than that of the fresh material. POLYM. ENG. SCI., 47:912–921, 2007. © 2007 Society of Plastics Engineers     

Change point detection in time series data with random forests

A large class of monitoring problems can be cast as the detection of a change in the parameters of a static or dynamic system, based on the effects of these changes on one or more observed variables. In this paper, the use of random forest models to detect change points in dynamic systems is considered. The approach is based on the embedding of multivariate time series data associated with normal process conditions, followed by the extraction of features from the resulting lagged trajectory matrix. The features are extracted by recasting the data into a binary classification problem, which can be solved with a random forest model. A proximity matrix can be calculated from the model and from this matrix features can be extracted that represent the trajectory of the system in phase space. The results of the study suggest that the random forest approach may afford distinct advantages over a previously proposed linear equivalent, particularly when complex nonlinear systems need to be monitored.     

Prostaglandin E2 Enhances Gap Junctional Intercellular Communication in Clonal Epithelial Cells

Prostaglandins are a group of lipids that produce diverse physiological and pathological effects. Among them, prostaglandin E2 (PGE2) stands out for the wide variety of functions in which it participates. To date, there is little information about the influence of PGE2 on gap junctional intercellular communication (GJIC) in any type of tissue, including epithelia. In this work, we set out to determine whether PGE2 influences GJIC in epithelial cells (MDCK cells). To this end, we performed dye (Lucifer yellow) transfer assays to compare GJIC of MDCK cells treated with PGE2 and untreated cells. Our results indicated that (1) PGE2 induces a statistically significant increase in GJIC from 100 nM and from 15 min after its addition to the medium, (2) such effect does not require the synthesis of new mRNA or proteins subunits but rather trafficking of subunits already synthesized, and (3) such effect is mediated by the E2 receptor, which, in turn, triggers a signaling pathway that includes activation of adenylyl cyclase and protein kinase A (PKA). These results widen the knowledge regarding modulation of gap junctional intercellular communication by prostaglandins.     

Early Postnatal Exposure to a Low Dose of Nanoparticulate Silver Induces Alterations in Glutamate Transporters in Brain of Immature Rats

Due to strong antimicrobial properties, silver nanoparticles (AgNPs) are used in a wide range of medical and consumer products, including those dedicated for infants and children. While AgNPs are known to exert neurotoxic effects, current knowledge concerning their impact on the developing brain is scarce. During investigations of mechanisms of neurotoxicity in immature rats, we studied the influence of AgNPs on glutamate transporter systems which are involved in regulation of extracellular concentration of glutamate, an excitotoxic amino acid, and compared it with positive control—Ag citrate. We identified significant deposition of AgNPs in brain tissue of exposed rats over the post-exposure time. Ultrastructural alterations in endoplasmic reticulum (ER) and Golgi complexes were observed in neurons of AgNP-exposed rats, which are characteristics of ER stress. These changes presumably underlie substantial long-lasting downregulation of neuronal glutamate transporter EAAC1, which was noted in AgNP-exposed rats. Conversely, the expression of astroglial glutamate transporters GLT-1 and GLAST was not affected by exposure to AgNPs, but the activity of the transporters was diminished. These results indicate that even low doses of AgNPs administered during an early stage of life create a substantial risk for health of immature organisms. Hence, the safety of AgNP-containing products for infants and children should be carefully considered.     

Modeling of a two-step solar hydrogen production plant

The promising advances in research in two-step solar hydrogen production from water have increased interest in producing hydrogen with this technology. In this framework, the Hydrosol II Project pilot plant for producing continuous solar hydrogen from water using a ferrite-based redox technology was erected at the CIEMAT-Plataforma Solar de Almería. Two reactors allow the oxidation and reduction steps to be performed in parallel, which, sequentially switched, make hydrogen production quasi-continuous.     

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

The wear of teeth is a major factor limiting mammalian lifespans in the wild. One method of describing worn surfaces, dental microwear texture analysis, has proved powerful for reconstructing the diets of extinct vertebrates, but has yielded unexpected results in early hominins. In particular, although australopiths exhibit derived craniodental features interpreted as adaptations for eating hard foods, most do not exhibit microwear signals indicative of this diet. However, no experiments have yet demonstrated the fundamental mechanisms and causes of this wear. Here, we report nanowear experiments where individual dust particles, phytoliths and enamel chips were slid across a flat enamel surface. Microwear features produced were influenced strongly by interacting mechanical properties and particle geometry. Quartz dust was a rigid abrasive, capable of fracturing and removing enamel pieces. By contrast, phytoliths and enamel chips deformed during sliding, forming U-shaped grooves or flat troughs in enamel, without tissue loss. Other plant tissues seem too soft to mark enamel, acting as particle transporters. We conclude that dust has overwhelming importance as a wear agent and that dietary signals preserved in dental microwear are indirect. Nanowear studies should resolve controversies over adaptive trends in mammals like enamel thickening or hypsodonty that delay functional dental loss.     

Phase separation in poly(butylene terephthalate)-based materials prepared by solid-state modification

The morphology of a series of poly(butylene terephthalate) (PBT)/fatty acid dimer diol (FADD)-based copolyesters prepared by solid-state modification (SSM) was studied. It was shown that in copolyesters containing less than 10 wt% FADD two different phases, i.e. a PBT crystalline phase and a PBT-rich amorphous phase, are present. The FADD residues were more or less homogeneously distributed throughout the interlamellar regions. For copolymers containing more than 10 wt% of FADD, a three-phase morphological model has to be used due to phase separation of a FADD-rich amorphous phase from the PBT-rich matrix, as confirmed by solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. The final morphology was dependent on the morphology of the PBT/FADD-based physical mixtures prior to SSM. In addition, it was shown that FADD diffusion during SSM influences the final morphology.