Numerical modelling of contaminant transport in coastal aquifers

This paper employs a two-dimensional variable density flow and transport model to investigate the transport of a dense contaminant plume in an unconfined coastal aquifer. Experimental results are also presented to show the contaminant plume in a freshwater-seawater flow system. Both the numerical and experimental results suggest that the neglect of the seawater interface does not noticeably affect the horizontal migration rate of the plume before it reaches the interface. However, the contaminant will travel further seaward and part of the solute mass will exit under the sea if the higher seawater density is not included. If the seawater density is included, the contaminant will travel upwards towards the beach along the freshwater-saltwater interface as shown experimentally. Neglect of seawater density, therefore, will result in an underestimate of solute mass rate exiting around the coastline. (C) 2002 IMACS. Published by Elsevier Science B.V. All rights reserved.

Transport safety for older people: A study of their experiences, perceptions and management needs

With evidence of increasing accident risk due to age-related declines in health and cognition affecting driver performance, there is a need for research promoting safe mobility of older people. The present study aimed to identify transport options and licensing issues for a group of older people in an Australian community. Ninety-five participants aged 75 and over were interviewed about their driving status and accident record and tested for cognitive ability. After stratification on cognitive level and driver status (current, ex-driver or non-driver), 30 were selected for further in-depth interviews concerning demographics, licence status and impact of change, travel options available and used, and travel characteristics. Considerable reliance on the motor vehicle as the mode of transport and the decision to cease driving were major quality-of-life issues. There was little evidence of planning and support in making the decision to stop driving. Some differences in transport decisions on the basis of cognitive level were evident; however, people with severely compromised cognitive ability (and, therefore, unable to give informed consent) had been excluded. The study suggested the need for resources to assist older people/carers/health professionals to plan for the transition from driver to non-driver and to manage alternative transport options more effectively

Bracken (Pteridium aquilinum)-induced DNA adducts in mouse tissues are different from the adduct induced by the activated form of the bracken carcinogen ptaquiloside

Following treatment with bracken fern (Pteridium aquilinum) extract and bracken spores a number of DNA adducts were detected by P-32-postlabeling. Three of these adducts have been described previously (Povey et al., Br. J. Cancer (1996) 74, 1342-1348) and in this study, using a slightly different protocol, four new adducts, with higher chromatographic mobility, were detected at levels ranging from 50 to 230% of those previously described, When DNA was treated in vitro with activated ptaquiloside (APT) and analysed by butanol extraction or nuclease P1 treatment, only one adduct was detected by P-32-postlabeling, This adduct was not present in the DNA from mice treated with bracken fern or spores, suggesting either that bracken contains genotoxins other than ptaquiloside or that the metabolism of ptaquiloside produces genotoxins not reflected by activated ptaquiloside. However, as the ATP-derived adduct has been detected previously in ileal DNA of bracken-fed calves, species-specific differences in the metabolism of bracken genotoxins may exist, thereby leading to differences in their biological outcomes. (C) 2001 Academic Press.

Adsorption in slit-like pores of activated carbons: Improvement of the Horvath and Kawazoe method

Anew thermodynamic approach has been developed in this paper to analyze adsorption in slitlike pores. The equilibrium is described by two thermodynamic conditions: the Helmholtz free energy must be minimal, and the grand potential functional at that minimum must be negative. This approach has led to local isotherms that describe adsorption in the form of a single layer or two layers near the pore walls. In narrow pores local isotherms have one step that could be either very sharp but continuous or discontinuous benchlike for a definite range of pore width. The latter reflects a so-called 0 --> 1 monolayer transition. In relatively wide pores, local isotherms have two steps, of which the first step corresponds to the appearance of two layers near the pore walls, while the second step corresponds to the filling of the space between these layers. All features of local isotherms are in agreement with the results obtained from the density functional theory and Monte Carlo simulations. The approach is used for determining pore size distributions of carbon materials. We illustrate this with the benzene adsorption data on activated carbon at 20, 50, and 80 degreesC, argon adsorption on activated carbon Norit ROX at 87.3 K, and nitrogen adsorption on activated carbon Norit R1 at 77.3 K.

Adsorption of mixtures containing subcritical fluids on activated carbon

A theoretical analysis of adsorption of mixtures containing subcritical adsorbates into activated carbon is presented as an extension to the theory for pure component developed earlier by Do and coworkers. In this theory, adsorption of mixtures in a pore follows a two-stage process, similar to that for pure component systems. The first stage is the layering of molecules on the surface, with the behavior of the second and higher layers resembling to that of vapor-liquid equilibrium. The second stage is the pore-filling process when the remaining pore width is small enough and the pressure is high enough to promote the pore filling with liquid mixture having the same compositions as those of the outermost molecular layer just prior to pore filling. The Kelvin equation is applied for mixtures, with the vapor pressure term being replaced by the equilibrium pressure at the compositions of the outermost layer of the liquid film. Simulations are detailed to illustrate the effects of various parameters, and the theory is tested with a number of experimental data on mixture. The predictions were very satisfactory.

Effects of surface chemistry on aromatic compound adsorption from dilute aqueous solutions by activated carbon

Adsorption of one nondissociating and four dissociating aromatic compounds onto three untreated activated carbons from dilute aqueous solutions were investigated. All adsorption experiments were preformed in pH-controlled solutions. The experimental isotherms were analyzed using the homogeneous Langmuir model. The surface chemical properties of the activated carbons were characterized using a combination of water adsorption, X-ray photoemission spectroscopy, and mass titration. These data give rise to a new insight into the adsorption mechanism of aromatic solutes, in their molecular and ionic forms, onto untreated activated carbons. It was found that, for the hydrophilic activated carbons, the dominant adsorption forces were observed to be dipolar interactions when the solutes were in their molecular form whereas dispersive forces, such as pi-pi interactions, were most likely dominant in the case of the basic hydrophobic carbons. However, when the solutes were in their ionic form adsorption occurs in all cases through dispersive forces.

Adsorption of aromatic compounds by activated carbon: Effects of functional groups and molecular size

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Further-more, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate-sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pK(a) values of the solutes.

Modelling activated sludge flocculation using population balances

Activated sludge flocculation was modelled using population balances. The model followed the dynamics of activated sludge flocculation providing a good approximation of the change in mean floe size with time. Increasing the average velocity gradient decreased the final floe size. The breakage rate coefficient and collision efficiency also varied with the average velocity gradient. A power law relationship was found for the increase in breakage rate coefficient with increasing average velocity gradient. Further investigation will be conducted to determine the relationship between the collision efficiency and particle size to provide a better approximation of dynamic changes in the floe size distribution during flocculation. (C) 2002 Published by Elsevier Science B.V.

Basal nonselective cation permeability in rat cardiac microvascular endothelial cells

The presence of a basal nonselective cation permeability was mainly investigated in primary cultures of rat cardiac microvascular endothelial cells (CMEC) by applying both the patch-clamp technique and Fura-2 microfluorimetry. With low EGTA in the pipette solution, the resting membrane potential of CMEC was -21.2 +/- 1.1 mV, and a Ca2+-activated Cl- conductance was present. When the intracellular Ca2+ was buffered with high EGTA, the membrane potential decreased to 5.5 +/- 1.2 mV. In this condition, full or partial substitution of external Na+ by NMDG(+) proportionally reduced the inward component of the basal I-V relationship. This current was dependent on extracellular monovalent cations with a permeability sequence of K+ > Cs+ > Na+ > Li+ and was inhibited by Ca2+, La3+, Gd3+, and amiloride. The K+/Na+ permeability ratio, determined using the Goldman-Hodgkin-Katz equation, was 2.01. The outward component of the basal I-V relationship was reduced when intracellular K+ was replaced by NMDG(+), but was not sensitive to substitution by Cs+. Finally, microfluorimetric experiments indicated the existence of a basal Ca2+ entry pathway, inhibited by La3+ and Gd3+. The basal nonselective cation permeability in CMEC could be involved both in the control of myocardial ionic homeostasis, according to the model of the blood-heart barrier, and in the modulation of Ca2+ -dependent processes. (C) 2002 Elsevier Science (USA).

Nomenclature of the GLUT/SLC2A family of sugar/polyol transport facilitators

The recent identification of several additional members of the family of sugar transport facilitators (gene symbol SLC2A, protein symbol GLUT) has created a heterogeneous and, in part, confusing nomenclature. Therefore, this letter provides a summary of the family members and suggests a systematic nomenclature for SLC2A and GLUT symbols.

MUC1 epithelial mucin (CD227) is expressed by activated dendritic cells

The MUC1 mucin (CD227) is a cell surface mucin originally thought to be restricted to epithelial tissues. We report that CD227 is expressed on human blood dendritic cells (DC) and monocyte-derived DC following in vitro activation. Freshly isolated murine splenic DC had very low levels of CD227; however, all DC expressed CD227 following in vitro culture. In the mouse spleen, CD227 was seen on clusters within the red pulp and surrounding the marginal zone in the white pulp. Additionally, we confirm CD227 expression by activated human T cells and show for the first time that the CD227 cytoplasmic domain is tyrosine-phosphorylated in activated T cells and DC and is associated with other phosphoproteins, indicating a role in signaling. The function of CD227 on DC and T cells requires further elucidation.

Inhibitors of COP-mediated Transport and Cholera Toxin Action Inhibit Simian Virus 40 Infection

Simian virus 40 (SV40) is a nonenveloped virus that has been shown to pass from surface caveolae to the endoplasmic reticulum in an apparently novel infectious entry pathway. We now show that the initial entry step is blocked by brefeldin A and by incubation at 20degreesC. Subsequent to the entry step, the virus reaches a domain of the rough endoplasmic reticulum by an unknown pathway. This intracellular trafficking pathway is also brefeldin A sensitive. Infection is strongly inhibited by expression of GTP-restricted ADP-ribosylation factor 1 (Arf1) and Sar1 mutants and by microinjection of antibodies to betaCOP. In addition, we demonstrate a potent inhibition of SV40 infection by the dipeptide N-benzoyl-oxycarbonyl-Gly-Phe-amide, which also inhibits late events in cholera toxin action. Our results identify novel inhibitors of SV40 infection and show that SV40 requires COPI- and COPII-dependent transport steps for successful infection.

Antagonists of protein kinase C inhibit rat retinal glutamate transport activity in situ

Neuronal and glial high-affinity transporters regulate extracellular glutamate concentration, thereby terminating synaptic transmission and preventing neuronal excitotoxicity. Glutamate transporter activity has been shown to be modulated by protein kinase C (PKC) in cell culture. This is the first study to demonstrate such modulation in situ, by following the fate of the non-metabolisable glutamate transporter substrate, D-aspartate. In the rat retina, pan-isoform PKC inhibition with chelerythrine suppressed glutamate uptake by GLAST (glutamate/aspartate transporter), the dominant excitatory amino acid transporter localized to the glial Muller cells. This effect was mimicked by rottlerin but not by Go6976, suggesting the involvement of the PKCdelta isoform, but not PKCalpha, beta or gamma. Western blotting and immunohistochemical labeling revealed that the suppression of glutamate transport was not due to a change in transporter expression. Inhibition of PKCdelta selectively suppressed GLAST but not neuronal glutamate transporter activity. These data suggest that the targeting of specific glutamate transporters with isoform-specific modulators of PKC activity may have significant implications for the understanding of neurodegenerative conditions arising from compromised glutamate homeostasis, e.g. glaucoma and amyotrophic lateral sclerosis.