Neutron radiography determination of water diffusivity in fired clay brick.

The real time neutron and gamma radiography station at Maria reactor, Institute of Atomic Energy, Swierk, Poland, was used to investigate the isothermal water absorption into fired clay brick samples. The investigated brick is different from the bricks reported in El Abd and Milczarek [2004. Neutron radiology study of water absorption in porous building materials: anomalous diffusing analysis. J. Phys. D: Appl. Phys. 37, 2305-2313] in density and chemical composition. Neutron radiography images were acquired regularly as the absorption time elapses. The water content, theta, along the flow direction, x, namely the water profiles theta(x,t) and the water front position as a function of the absorption time, t, were extracted from neutron radiography images. The results were discussed in terms of the macroscopic theory of water infiltration in unsaturated porous media. It was shown that the water front position followed the square root t-scaling (x(m)=phi(m) square root t) and the profiles (theta-phi) converged to a universal one master curve. The water diffusivity was analytically determined from the experimental results. It has the so-called hypo-diffusive character, namely its gradient with respect to the water content is positive. Neutron radiography is a powerful method to distinguish among the unsaturated flow in different porous construction materials.

Standard and four-footed canes: their effect on the standing balance of patients with hemiparesis.

We studied 14 patients to test the hypotheses that, when patients with hemiparesis use a cane to assist standing balance, their postural sway decreases and the average position of their center of pressure (COP) shifts forward and towards the cane side, and that there is no difference in either of these parameters between standard and four-footed canes. Each subject stood on a Kistler force platform for three ten-second intervals: one without a cane, one with a standard cane, and one with a four-footed cane. Matched-pairs t tests revealed a significant decrease in both the mediolateral (ML) and anteroposterior (AP) travel (postural sway) when the subjects used the standard cane. There was also a significant shift of the average ML position of the COP toward the cane side when they used a standard cane, but no significant difference in the average AP position. When they used the four-footed cane, neither the differences in travel nor the differences in COP position were significant, although they were similar in magnitude to those measured when they used the standard cane, compared with which there was no significant difference. Two conclusions appear warranted. First, a standard cane has a significant effect on force-platform measures of the standing balance of persons with hemiparesis of mild-to-moderate severity--specifically a reduction in the extent of ML and AP postural sway and a shift in the mean position of the COP toward the cane side. Second, as regards such measures of standing balance, a four-footed cane appears to offer no advantage over a standard one.

The formation of phosphatidylethanolamine from diglyceride by extracts of Escherichia coli.

Extensively dialyzed cell-free homogenates or washed particulate fractions, of Escherichia coli in the presence of added CTP, Mg2+, serine, and rac-glycerol 3-phosphate, incorporated [32P]phosphatidic acid into phosphatidylglycerol and cardiolipin but not into phosphatidylethanolamine. [14C]Phosphatidic acid could be incorporated by these preparations into phosphatidylethanolamine in the absence of added CTP and Mg2+. CDP-diglyceride did not significantly affect the formation of [14C]phosphatidylethanolamine from [14C]phosphatidic acid. 14C-labeled diglyceride was also readily incorporated into phosphatidylethanolamine in the absence of added cofactors by both homogenate and particulate fraction. Serine stimulated the incorporation somewhat whereas CTP + Mg2+ diminished this conversion slightly because of concurrent [14C]phosphatidic acid and [14C]phosphatidylglycerol formation. CDP-diglyceride did not significantly affect the conversion of 14C-labeled diglyceride to phosphatidylethanolamine. Dialyzed 14C-labeled cytosol fractions of E. coli, obtained from cells grown in medium containing [14C]serine, transferred some of their label to phosphatidylethanolamine in the presence of fresh particulate fraction. This transfer was stimulated by added diglyceride. The results indicate that phosphatidylethanolamine can be synthesized from exogenous diglyceride by a pathway which does not require CDP-diglyceride as an intermediate but which likely makes use of an endogenous cofactor supplying phosphorylethanolamine and (or) phosphorylserine.