Analysis and modeling of heaping behavior of granular mixtures within a computational mechanics framework

This paper presents a continuum model of the flow of granular material during filling of a silo, using a viscoplastic constitutive relation based on the Drucker-Prager plasticity yield function. The performed simulations demonstrate the ability of the model to realistically represent complex features of granular flows during filling processes, such as heap formation and non-zero inclination angle of the bulk material-air interface. In addition, micro-mechanical parametrizations which account for particle size segregation are incorporated into the model. It is found that numerical predictions of segregation phenomena during filling of a binary granular mixture agree well with experimental results. Further numerical tests indicate the capability of the model to cope successfully with complex operations involving granular mixtures.

On the continuum modelling of segregation of granular mixtures during hopper emptying in core flow mode

In this paper, the application of a continuum model is presented, which deals with the discharge of multi-component granular mixtures in core flow mode. The full model description is given (including the constitutive models for the segregation mechanism) and the interactions between particles at the microscopic level are parametrised in order to predict the development of stagnant zone boundaries during core flow discharges. Finally, the model is applied to a real industrial problem and predictions are made for the segregation patterns developed during mixture discharge in core flow mode.

A Quantitative and Mechanistic Assessment of Activated Thrombin-Activatable Fibrinolysis Inhibitor and its Role in Pathological Bleeding and Thrombosis

The coagulation and fibrinolytic systems are linked by the thrombin-thrombomodulin complex which regulates each system through activation of protein C and TAFI, respectively. We have used novel assays and techniques to study the enzymology and biochemistry of TAFI and TAFIa, to measure TAFI activation in hemophilia A and protein C deficiency and to determine if enhancing TAFI activation can improve hemostasis in hemophilic plasma and whole blood. We show that TAFIa not TAFI attenuates fibrinolysis in vitro and this is supported by a relatively high catalytic efficiency (16.41μM-1s-1) of plasminogen binding site removal from fibrin degradation products (FDPs) by TAFIa. Since the catalytic efficiency of TAFIa in removing these sites is ~60-fold higher than that for inflammatory mediators such as bradykinin it is likely that FDPs are a physiological substrate of TAFIa. The high catalytic efficiency is primarily a result of a low Km which can be explained by a novel mechanism where TAFIa forms a binary complex with plasminogen and is recruited to the surface of FDPs. The low Km also suggests that TAFIa would effectively cleave lysines from FDPs during the early stages of fibrinolysis (i.e. at low concentrations of FDPs). Since individuals with hemophilia suffer from premature fibrinolysis as a result of insufficient TAFI activation we quantified TAFI activation in whole blood from hemophilic subjects. Both the rate of activation and the area under the TAFI activation time course (termed TAFIa potential) was determined to be reduced in hemophilia A and the TAFIa potential was significantly and inversely correlated with the clinical bleeding iii phenotype. Using a novel therapeutic strategy, we used soluble thrombomodulin to increase TAFI activation which improved the clot lysis time in factor VIII deficient human plasma and hemophilic dog plasma as well as hemophilic dog blood. Finally, we briefly show in a biochemical case study that TAFI activation is enhanced in protein C deficiency and when afflicted individuals are placed on Warfarin anticoagulant therapy, TAFI activation is reduced. Since TAFIa stabilizes blood clots, this suggests that reducing TAFI activation or inhibiting TAFIa may help restore blood flow in vessels with pathological thrombosis.

Dazed and Confused: Accidental Mixtures of Goods and the Theory of Acquisition of Title

This paper explores the law of accidental mixtures of goods. It traces the development of the English rules on mixture from the seminal nineteenth century case of Spence v Union Marine Insurance Co to the present day, and compares their responses to those given by the Roman law, which always has been claimed as an influence on our jurisprudence in this area. It is argued that the different answers given by English and Roman law to essentially the same problems of title result from the differing bases of these legal systems. Roman a priori theory is contrasted with the more practical reasoning of the common law, and while both sets of rules are judged to be coherent on their own terms, it is suggested that the difference between them is reflective of a more general philosophical disagreement about the proper functioning of a legal system, and the relative importance of theoretical and pragmatic considerations.