Mathematical modeling of T-cell activation kinetic.

T-cell activation is a crucial step in mounting of the immune response. The dynamics of T-cell receptor (TCR) specific recognition of peptide presented by major histocompatibility complex (MHC) molecule decides the fate of the T cell. Several biochemical interactions interfere resulting in a highly complex mechanism that would be difficult to understand without computer help. The aim of the present study was to define a mathematical model in order to approach the kinetics of monoclonal T-cell-specific activation. The reaction scheme was first described and the model was tested using experimental parameters from the published data. Simulations were concordant with experimental data showing proportional decrease of membrane TCR and production of interleukin-2 (IL-2). Agonist and antagonist peptides induce different levels of intracellular signal that could make the yes or no decision for entry to cell cycle. Different conditions (peptide concentrations, initial TCR density and exogenous IL-2 levels) can be tested. Several parameters are missing for parameters estimation and adjustment before it could be adapted for a polyclonal T-cell reaction model. However, the model should be of interest in setting experiments, simulation of clinical responses and optimization of preventive or therapeutic immunotherapy.

Experimental study of small aggregate settling.

The drag coefficient and hydrodynamic radius of particles are important parameters needed in crystallization science. Small aggregates of micrometric primary particles are mainly produced in stirred crystallizers. We present experimental results on the drag coefficient of macroscopic aggregates consisting of glass beads in the number range [2,100]. The drag coefficient is calculated from settling measurements in glycerol in order to preserve the Stokesian nature of typical flow around particles in a crystallizer. We show that the hydrodynamic radius of these aggregates is almost the radius based on the average projected area over all orientations. This result is extended to larger and more porous aggregates.

Turbulent Aggregation of Titania in Water.

This paper deals with the application of two in situ particle sizing methods to the study of aggregation of titanium dioxide in turbulent aqueous solutions. Turbidity measurements are used to characterize aggregation of diluted suspensions (solid volume fraction less than 10(-4)). Analysis of backscattered light can be applied to highly concentrated suspensions. Because in situ measurements are possible, the aggregation process can be followed from its beginning to the final steady state which is always observed. The influences of stirring rate and solid volume fraction on the aggregation dynamics are presented. They are interpreted in the framework of a model of aggregation which takes into account the morphology and the related optical properties of the aggregates and the physical and hydrodynamic interactions between aggregates. The complex relationship between aggregate restructuring and aggregation on one hand, and fragmentation on the other hand, is considered. Copyright 2000 Academic Press.

Turbulent Coagulation Efficiency

The coagulation of small particles in a turbulent flow is considered. A kinetic equation based on Levich's theory is proposed. It takes into account the physicochemical and hydrodynamic interactions. The predicted coagulation efficiency is compared to experimental and other theoretical works. Thanks to its compact expression, the coagulation efficiency is much easier to calculate and to manipulate than the relationships derived from other models.

The Duke-UNC Functional Social Support Questionnaire. Measurement of social support in family medicine patients.

A 14-item, self-administered, multidimensional, functional social support questionnaire was designed and evaluated on 401 patients attending a family medicine clinic. Patients were selected from randomized time-frame sampling blocks during regular office hours. The population was predominantly white, female, married, and under age 45. Eleven items remained after test-retest reliability was assessed over a 1- to 4-week follow-up period. Factor analysis and item remainder analysis reduced the remaining 11 items to a brief and easy-to-complete two-scale, eight-item functional social support instrument. Construct validity, concurrent validity, and discriminant validity are demonstrated for the two scales (confidant support--five items and affective support--three items). Factor analysis and correlations with other measures of social support suggest that the three remaining items (visits, instrumental support, and praise) are distinct entities that may need further study.