Measurement of intracellular magnesium concentration in 3T3 fibroblasts with the fluorescent indicator Mag-indo-1

Mag-indo-1, a fluorescent probe for measuring intracellular magnesium concentration, was used in 3T3 fibroblasts with microspectrofluorometry. The complex emission fluorescence spectrum emitted by a single living cell was analyzed with a computerized method, making it possible to evaluate the contribution of each species of Mag-indo-1 to the total fluorescence. The dye self-association observed in solutions at high dye concentration was not encountered in cells. The model of equilibria of Mag-indo-1 (monomer form) with protons, magnesium, and protein was then applied to calculate the intracellular magnesium concentration. The spectral analysis evaluated the contribution of each fluorescent species of Mag-indo-1 (a deprotonated, a magnesium-bound, and a protein-bound form) and of the cell autofluorescence to the total cell fluorescence. This method permitted accurate and reproducible measurements of intracellular magnesium concentration. Finally, this method was applied to the measurement of intracellular magnesium concentration in a 3T3 fibroblast population in exponential growth phase.     

Numerical shakedown analysis of axisymmetric sandwich shells: An upper bound formulation

Shakedown analysis of axisymmetric elastic–perfectly plastic sandwich shells is performed here using a new upper bound formulation based on a special form of Koiter's theorem concerning piecewise linearized yield surfaces. Starting from finite element techniques and the Tresca sandwich yield condition, shakedown analysis is reduced to a linear programming problem which is solved by a powerful simplex algorithm. Numerical results are given for a number of examples and a comparison is made with a previously computed lower bound formulation.