686 research outputs found
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 Firmsā Innovation Performance
This paper investigates the extent to which different knowledge sources contribute to firmsā 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 firmsā 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, uraÄena je i komparacija sa propisima Evropske Unije. Prikazan je uticaj Agencija za bezbednost saobraÄaja Republike Slovenije na pomenute propise, ali i uticaj predmetnog zakonodavstva na bezbednost saobraÄaja i zaÅ”titu 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
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