Experimental and modeling of the electrodialytic and dialytic treatment of a fly ash containing Cd,Cu and Pb

A one-dimensional model is developed for simulating the electrodialytic and dialytic treatment of a fly ash containing cadmium, copper and lead. Two experimental systems have been used, a column of ash and a stirred ash suspension. The movement of Cd, Cu and Pb has been modeled taking into account the diffusion transport resulting from the concentration gradients of their compounds through the membranes and boundary layers and the electromigration of their ionic, simple and complex species during the operation. The model also includes the electromigration of the non-contaminant most important principal ionic species in the system, H⁺ and OH⁻, proceeding of the electrolysis at the electrodes, Ca²⁺, CO₃ ⁼, SO₄ ⁼, etc. proceeding from the ash and Na⁺ and NO₃ ⁻, or citrate and ammonium ions incorporated as electrolyte solutions and/or as agent solution during the ash treatment. The simulation also takes into account that OH⁻ generated on the cathode, during the electrodialytic remediation, is periodically neutralized by the addition of nitric acid in the cathode compartment. The anion and cation-exchange membranes are simply represented as ionic filters that preclude the transport of the cations and anions, respectively, with the exception of H⁺ which is retarded but pass through the anion-exchange membrane.     

Modeling residue hydrotreating

In this paper a kinetic model for the residue hydrotreating is presented. The model considers kinetics, adsorption and diffusion inside the hydrodemetallization catalyst pellets. The diffusion is described by the Stefan–Maxwell equations extended for starkly different sized molecules, due to molecular size of residue molecules large distribution. Effective diffusion coefficients vary with porosity and tortuosity evolution due to volume constraints in the catalyst pellets. The model's kinetic and thermodynamic parameters were estimated from a set of experiments carried out in a batch reactor with a Middle East vacuum residue. A comparison between experimental and simulated metal profiles inside the catalyst exhibit the slow diffusion, validating the importance of adding mass transfer phenomena and considering volume constraints even in a macroporous demetallization catalyst.The model was validated by other tests performed in the same reactor using the same vacuum residue, but with different catalysts. The differences in the catalyst pore size allowed to predict all the hydrotreatment yields, showing diffusion is a crucial factor.     

Field validation of specific ecotoxicological tools for aquatic systems impacted with acid mine drainage

Acid mine drainage (AMD) is characterised by very low pH and high heavy metal concentrations. Serious ecotoxicological effects, often leading to the complete disruption of the ecosystem, can be observed at the regions suffering this kind of contamination. Those effects can be caused either by low pH itself or by other contaminants that emerge with water acidification (mobilisation and increased solubility of heavy metals). The discrimination between the toxicity due to each of these two factors is not possible with the existing toxicity tests; the addition of chelating agents or serial dilution methods seriously alter the chemical and physical properties of the effluent. A toxicity test, based on the survival time of Ceriodaphnia dubia (Crustacea, Cladocera) neonates exposed to the unchanged effluent, was developed and field validated, on an AMD contaminated site.     

Numerical simulation of dam construction using low-CO<Subscript>2</Subscript>-emission concrete

Cement production gives rise to CO₂ emissions generated by the calcination of CaCO₃ and by the combustion of fossil fuels, being responsible for about 5% of the global CO₂ emissions. These emissions can be substantially reduced if cement replacement materials are used. In this paper two residual ashes that can be used as mineral additions are considered: sugar cane bagasse ash and rice husk ash. A case study of the construction of a dam with a blended material composed by cement and these two ashes is presented, indicating the potentiality of its use for civil engineering applications. The analyses were performed using experimental and numerical tools developed on the basis of a thermo-chemo-mechanical model. This model considers the coupling, within the theory of thermodynamics, of the several phenomena that intervene in the hydration process, namely, exothermicity, thermo-activation, chemo-plasticity, evolution of thermal and mechanical properties with the hydration reaction, which includes creep and relaxation.     

Influence of the calcium concentration in the presence of organic phosphorus on the physicochemical compatibility and stability of all-in-one admixtures for neonatal use

Background  

Preterm infants need high amounts of calcium and phosphorus for bone mineralization, which is difficult to obtain with parenteral feeding due to the low solubility of these salts. The objective of this study was to evaluate the physicochemical compatibility of high concentrations of calcium associated with organic phosphate and its influence on the stability of AIO admixtures for neonatal use.     

Optimisation of a device for pick-up of low-frequency radio signals and transmission over polymer optical fibres

The development of passive (without RF amplifier) and optimised VHF-detector/optical-modulator circuit module as a device for operation in the 88–108 MHz band will be described in this paper. It uses illumination-type light-emitting diodes (LEDs) emitting at 650 nm as the light source, coupled with poly(methyl methacrylate) polymer optical fibre. Reactive impedance matching is performed between the optoelectronic light source and the antenna by taking into account the some capacitance variation with the frequency of the antenna and of the biased LED, not resolved with the packaging parasitic effects. The relatively simple device presented here and named wireless-over-polymer optical fibre may be useful in many low-frequency radio-over-fibre applications and may contribute to energy savings.     

Comparison between urban and rural pollen of Chenopodium alba and characterization of adhered pollutant aerosol particles

In this work, the structure and protein profile of Chenopodium alba pollen samples collected in rural and urban environments were compared. Pollen structure was studied using light and scanning electron microscopy and the soluble protein profile was investigated by means of biochemical analyses (SDS-PAGE). The rural pollen has the opercules well defined while in the urban pollen there is a fine film covering its wall, and opercules are deformed. A decrease in the protein content in the urban pollen and different protein profiles were observed. Micro-Raman spectroscopic studies allowed the identification of carbon-containing particles in the urban pollen wall as well as its morphology and size. The results of this study indicate that the particles present in the urban air are diesel exhaust particles that are adsorbed and accumulated on the Chenopodium alba pollen. These particles can contribute for modifying their structure and protein content.     

InBase, the New England Biolabs Intein Database

Inteins are intervening sequences that splice as proteins, not RNA. InBase, the New England Biolabs Intein Database (http://www.neb. com/neb/inteins.html), is a comprehensive on-line database that includes the Intein Registry, along with detailed information about each intein and its host protein, tabulated comparisons and a comprehensive bibliography including papers in press.     

High pressure-temperature effects on enzymatic activity: Naringin bioconversion

Initially exploited in chemistry and physics, high-pressure technology has gained importance in various fields.     

Role of the cytoskeleton in calcium signaling in NIH 3T3 cells. An intact cytoskeleton is required for agonist-induced [Ca2+]i signaling, but not for capacitative calcium entry

Treatment of NIH 3T3 cells with cytochalasin D (10 microM, 1 h at 37 degrees C) disrupted the actin cytoskeleton and changed the cells from a planar, extended morphology, to a rounded shape. Calcium mobilization by ATP or by platelet-derived growth factor was abolished, while the ability of thapsigargin (2 microM) to empty calcium stores and activate calcium influx was unaffected. Similar experiments with nocodazole to depolymerize the tubulin network yielded identical results. Platelet-derived growth factor induced an increase in inositol phosphates, and this increase was undiminished in the presence of cytochalasin D. Therefore, the blockade of agonist responses by this drug does not result from decreased phospholipase C. Injection of inositol 1,4,5-trisphosphate (IP3) released calcium to the same extent in control and cytochalasin D-treated cells. Confocal microscopic studies revealed a significant rearrangement of the endoplasmic reticulum after cytochalasin D treatment. Thus, disruption of the cytoskeleton blocks agonist-elicited [Ca2+]i mobilization, but this effect does not result from a lower calcium storage capacity, impaired function of the IP3 receptor, or diminished phospholipase C activity. We suggest that cytoskeletal disruption alters the spatial relationship between phospholipase C and IP3 receptors, impairing phospholipase C-dependent calcium signaling. Capacitative calcium entry was not altered under these conditions, indicating that the coupling between depletion of intracellular calcium stores and calcium entry does not depend on a precise structural relationship between intracellular stores and plasma membrane calcium channels.