Ability of Lactobacillus gasseri K 7 to inhibit Escherichia coli adhesion in vitro on Caco-2 cells and ex vivo on pigs' jejunal tissue

The ability of Lactobacillus (Lb.) gasseri K 7 to inhibit adhesion of Escherichia coli O8:K88 to intestinal mucosa was studied on cultured Caco-2 cells and ex vivo on pigs' small intestinal tissue. Lactobacilli were added simultaneously with E. coli, before E. coli and after E. coli for competition, exclusion and displacement assays. The concentration of lactobacilli on fully differentiated Caco-2 cells was 4.5+/-0.3 x 10(8) cfu/well, while the concentration of E. coli varied from 1.5 x 10(6) to 4.3 x 10(8) cfu/well. The number of E. coli adhered to Caco-2 monolayer (cfu/well) was lineary correlated (R(2)=0.97) to the concentration of added cells. In the assay simulating exclusion, E. coli adhesion was reduced by Lb. gasseri K 7 strain by 0.1 to 0.6 log cfu/well. The binding of E. coli was inhibited even more when incubated simultaneously with lactobacilli, particularly at the lowest concentration of E. coli (ratio E. coli/lactobacilli 1:248), where five-times reduction (or 0.7 log) was observed. When adhesion to tissue derived from pigs' jejunum was tested, concentration of E. coli was constant (6.9+/-0.14 x 10(7) cfu/ml), while the concentration of Lb. gasseri K 7 was 5.9 x 10(7) and 1.3 x 10(7) cfu/ml in two independent experiments, respectively. The adhesion of E. coli and Lb. gasseri K 7 cells to jejunal mucosa was similar (1.0+/-0.17 x 10(6) and 1.54+/-0.10 x 10(6) cfu/cm(2)) when the concentrations of single strains in suspensions were approximately the same. No significant competition, exclusion or displacement of E. coli by lactobacilli was observed on jejunal tissue. In conclusion, Lb. gasseri K 7 was found to be effective in reducing E. coli adhesion to Caco-2 enterocytes, but it was not able to do so in ex vivo conditions tested for pig jejunal tissue.     

On gas bubbles in industrial aluminium cells with prebaked anodes and their influence on the current distribution

The secondary current distribution in industrial aluminium cells with prebaked anodes was calculated, taking into account the gas bubbles. The input data were obtained on the basis of a physical model and data suggested in the literature. The bubbles were modelled in the following manner: (i) as very small bubbles dispersed in a homogeneous layer with higher electrical resistivity than the bulk of the electrolyte, (ii) as large bubbles modelled as discrete slabs with infinite resistivity, and (iii) as a combination of (i) and (ii). The bubble size and the number of bubbles, as well as the resistance of the homogeneous bubble layer, were varied to give an equivalent voltage drop in the range 0.1–0.4 V. Large bubbles (slabs) appeared to have a significant screening effect on the anodic current densities. The anodic current densities between slabs showed local maxima, sometimes reaching twice the value of the working current density (0.75 A cm^–2). The cathodic current densities had local minima underneath the large anodic bubbles, following their position at the anode. Underneath a bubble of 6.1 cm width, the cathodic current density decreased from 0.75 to 0.23 A cm^–2.     

Mathematical modelling of industrial aluminium cells with prebaked anodes: Part I: Current distribution and anode shape

In aluminium electrolysis cells with prebaked anodes the anode shape changes with time after a new anode has been set, reaching a steady state profile after several days. Mathematical modelling of the anode consumption, using current densities obtained by solving the Laplace equation in 2D space, showed that a constant shape is reached after 6–8.6 days, depending on the width of the gap to a neighbouring anode or to the sidewall of the cell and on the shape of the frozen sideledge. The calculated steady state shapes were similar to measured shapes of industrial anodes. The current density decreases along the side of the anode from the nominal value at the underside (0.75 A cm–2) to a minimum near the surface of the electrolyte (0.08–0.28 A cm–2) depending on the geometry. The fraction of the current passing through the sides of the anode is of the order of 15%. Two approaches to the calculation of the anode shape are discussed: one method of incremental time steps, and one method using the 'near steady-state shape condition.     

On some qualitative properties for solutions of a certain two-dimensional fractional differential systems

By means of the modification of Medve?’s de-singular method and a result of two-dimensional linear integral inequalities, components-wise (not on some norm) upper bounds are obtained for solutions of a class of nonlinear two-dimensional systems of fractional differential equations. The uniqueness and continuous dependence of the solutions are also discussed here.     

Structural Steel ASTM A709—Behavior at Uniaxial Tests Conducted at Lowered and Elevated Temperatures, Short-Time Creep Response, and Fracture Toughness Calculation

This paper presents the temperature dependence of the mechanical properties of structural high-strength low-alloy (HSLA) ASTM A709 Gr50 steel (En10025: S355 JO; DIN: ST 52-3U). Engineering stress-strain diagrams at lowered and elevated temperatures are presented. Creep responses for selected constant stresses at selected temperatures are also presented and are fit with a rheological model. Additionally, a relation between impact toughness and fracture toughness is proposed and is validated using results from notch impact tests on a Charpy pendulum impact machine.     

Removal of antimicrobials using advanced wastewater treatment

Removal of numerous classes of pharmaceuticals from the municipal and industrial wastewater, using conventional wastewater treatment, is incomplete and several studies suggested that improvement of this situation would require the application of advanced treatment techniques. This is particularly important for the treatment of industrial effluents, released from pharmaceutical industries, which can contain rather high concentrations of antimicrobials. The aim of this work was to evaluate membrane bioreactors (MBRs), nanofiltration, reverse osmosis and ozonation, as well as their combinations, for the removal of antimicrobials from a synthetic wastewater which simulated highly contaminated industrial effluents. The study was performed using a mixture of four important classes of antimicrobials, including sulfonamides (SA), fluoroquinolones (FQ), macrolides (MAC) and trimethoprim (TMP). Performance of two different types of MBRs, Kubota and Zenon, was evaluated under different regimes regarding hydraulic retention time, total organic load and total nitrogen load. It was shown that elimination of SA in MBR treatment was very efficient, while the elimination of MAC, FQ, and TMP was incomplete. A mass balance of these contaminants in MBR suggested that microbial transformation represented the main mechanism, while only a small percentage was eliminated from the aqueous phase by adsorption onto sludge particles. Nanofiltration and reverse osmosis achieved high elimination rates however produced highly contaminated concentrate. High removal was achieved using ozonation, but further research is needed to characterize formed ozonation products.