Aggregation of Red Blood Cells: From Rouleaux to Clot Formation

Red blood cells are known to form aggregates in the form of rouleaux. This aggregation process is believed to be reversible, but there is still no full understanding on the binding mechanism. There are at least two competing models, based either on bridging or on depletion. We review recent experimental results on the single cell level and theoretical analyses of the depletion model and of the influence of the cell shape on the binding strength. Another important aggregation mechanism is caused by activation of platelets. This leads to clot formation which is life saving in the case of wound healing but also a major cause of death in the case of a thrombus induced stroke. We review historical and recent results on the participation of red blood cells in clot formation

How Internal and External Sources of Knowledge Contribute to Firms’ Innovation Performance

This paper investigates the extent to which different knowledge sources contribute to firms’ innovation performance. The empirical analysis estimates the relationships in the structural model of the influence of knowledge sources on innovative performance using data collected through personal interviews at 303 firms. The results reveal that internal sources have the most important influence on firms’ innovative performance and confirm that, in their innovation process, firms mostly rely on knowledge developed through in-house R&D efforts, continuous improvement, and internal education and training programs. The data show that in-house learning is not sufficient for generating innovation and that firms need to supplement internal knowledge with knowledge acquired outside the firm. They mainly need to secure links with firms and institutions in the global environment if they want to secure the inflow of new ideas and approaches that will eventually lead to innovations.knowledge, innovation, structural equation modeling

The Role of Foreign Direct Investment in Transition Economies, with Special Emphasis on the Republic of Croatia

This paper examines the process of transition in Central Europe. It examines the development of international trade theories as a basis for the emergence of Foreign Direct Investment (FDI), along with a brief history of FDI. Special consideration is given to FDI as a determinate of economic growth in transitional Croatia. It is argued that Croatia has reached a level of economic development where it can make use of substantial amounts of FDI

Parameterization invariance and shape equations of elastic axisymmetric vesicles

The issue of different parameterizations of the axisymmetric vesicle shape addressed by Hu Jian-Guo and Ou-Yang Zhong-Can [ Phys.Rev. E {\bf 47} (1993) 461 ] is reassesed, especially as it transpires through the corresponding Euler - Lagrange equations of the associated elastic energy functional. It is argued that for regular, smooth contours of vesicles with spherical topology, different parameterizations of the surface are equivalent and that the corresponding Euler - Lagrange equations are in essence the same. If, however, one allows for discontinuous (higher) derivatives of the contour line at the pole, the differently parameterized Euler - Lagrange equations cease to be equivalent and describe different physical problems. It nevertheless appears to be true that the elastic energy corresponding to smooth contours remains a global minimum.Comment: 10 pages, latex, one figure include

Second variation of the Helfrich-Canham Hamiltonian and reparametrization invariance

A covariant approach towards a theory of deformations is developed to examine both the first and second variation of the Helfrich-Canham Hamiltonian -- quadratic in the extrinsic curvature -- which describes fluid vesicles at mesoscopic scales. Deformations are decomposed into tangential and normal components; At first order, tangential deformations may always be identified with a reparametrization; at second order, they differ. The relationship between tangential deformations and reparametrizations, as well as the coupling between tangential and normal deformations, is examined at this order for both the metric and the extrinsic curvature tensors. Expressions for the expansion to second order in deformations of geometrical invariants constructed with these tensors are obtained; in particular, the expansion of the Hamiltonian to this order about an equilibrium is considered. Our approach applies as well to any geometrical model for membranes.Comment: 20 page

The influence of Slovenian traffic safety agency on motor vehicle legislation

Cilj ovog rada je pregled sistema odobrenja tipa vozila u Republici Sloveniji. Kroz analizu nacionalnih propisa za motorna vozila, urađena je i komparacija sa propisima Evropske Unije. Prikazan je uticaj Agencija za bezbednost saobraćaja Republike Slovenije na pomenute propise, ali i uticaj predmetnog zakonodavstva na bezbednost saobraćaja i zaštitu životne sredine.The objective of this paper is to provide an analysis of the type-approval system in the Republic of Slovenia. In this analysis Slovenian legislation regarding motor vehicles is compared to EU legislation. Besides this the Slovenian Traffic Safety Agency's influence on the above mentioned legislation is presented, as well as the legislation's influence on safety and environmental friendliness

Viscous regularization and r-adaptive remeshing for finite element analysis of lipid membrane mechanics

As two-dimensional fluid shells, lipid bilayer membranes resist bending and stretching but are unable to sustain shear stresses. This property gives membranes the ability to adopt dramatic shape changes. In this paper, a finite element model is developed to study static equilibrium mechanics of membranes. In particular, a viscous regularization method is proposed to stabilize tangential mesh deformations and improve the convergence rate of nonlinear solvers. The Augmented Lagrangian method is used to enforce global constraints on area and volume during membrane deformations. As a validation of the method, equilibrium shapes for a shape-phase diagram of lipid bilayer vesicle are calculated. These numerical techniques are also shown to be useful for simulations of three-dimensional large-deformation problems: the formation of tethers (long tube-like exetensions); and Ginzburg-Landau phase separation of a two-lipid-component vesicle. To deal with the large mesh distortions of the two-phase model, modification of vicous regularization is explored to achieve r-adaptive mesh optimization