The Chemical State of the Calcium Reacting in the Coagulation of Blood

1. The widely accepted theory that calcium participates in the coagulation mechanism in the form of Ca++ and acts as a catalyst is not in accord with several important experimental findings: (a) The anticoagulant action of sodium oxalate is much slower than the precipitation of ionized calcium as the oxalate salt. (b) Sodium citrate begins to depress prothrombin activity at a concentration at which ionized calcium is still present. The inability of tricalcium phosphate to adsorb prothrombin from citrated plasma indicates that citrate forms a complex with prothrombin and it is postulated that prothrombin is thereby inactivated. (c) In plasma which is decalcified, i.e. in which the Ca++ is markedly reduced, the labile factor of prothrombin rapidly decreases. A concentration of 0.01 M sodium citrate sufficient to inhibit coagulation does not depress Ca++ enough to cause diminution of the labile factor, whereas when the concentration is increased to 0.02 M the labile factor decreases as rapidly as in oxalated plasma. 2. It is postulated that calcium functions in coagulation not as Ca++ but as combined with a component which is part of the prothrombin complex that is not adsorbed by tricalcium phosphate. A concentration of sodium citrate just sufficient to inhibit coagulation is not enough to remove calcium from the essential prothrombin component. The primary anticoagulant action of sodium citrate is therefore not decalcification but antiprothrombic. 3. It has been shown that citrated plasma is basically different from oxalated plasma in several important aspects. Unless cognizance is taken of these differences, serious errors and misinterpretations of experimental findings may be made

Mechanical Response of a Small Swimmer Driven by Conformational Transitions

A conformation space kinetic model is constructed to drive the deformation cycle of a three-sphere swimmer to achieve propulsion at low Reynolds number. We analyze the effect of an external load on the performance of this kinetic swimmer, and show that it depends sensitively on where the force is exerted, so that there is no general force--velocity relation. We discuss how the conformational cycle of such swimmers should be designed to increase their performance in resisting forces applied at specific points.Comment: 4 pages, 3 figures; accepted for publication in Phys. Rev. Let

Foundations of aeroelastic optimization and some applications to continuous systems

Static and dynamic aeroelastic problems in optimization of continuous system

Synthetic approaches to specifically labeled dimethyl-dideuterionaphthalenes

The purpose of this work was the study of synthetic approaches to specifically labeled deuterated 1, 4-dimethylnaphthalenes. Alkylation of ortho- and para-dibromobenzenes eventually led to the formation of some 1, 4-dimethylnaphthalene although deuteration was rather poor. Under the conditions employed, much isomerization of Friedel-Crafts products resulted. Not only did the bromines rearrange intramolecularly, but substantial rearrangement of the alkylating moiety may also have occurred. The major products of these reactions were dibromophenylcyclohexanes. It appears from the products obtained by the methods employed in our work that specific monodeuteration rather than specific dideuteration should be used to attain the desired product