Stability of heterogeneous parallel-bond adhesion clusters under static load

Adhesion interactions mediated by multiple bond types are relevant for many biological and soft matter systems, including the adhesion of biological cells and functionalized colloidal particles to various substrates. To elucidate advantages and disadvantages of multiple bond populations for the stability of heterogeneous adhesion clusters of receptor-ligand pairs, a theoretical model for a homogeneous parallel adhesion bond cluster under constant loading is extended to several bond types. The stability of the entire cluster can be tuned by changing densities of different bond populations as well as their extensional rigidity and binding properties. In particular, bond extensional rigidities determine the distribution of total load to be shared between different sub-populations. Under a gradual increase of the total load, the rupture of a heterogeneous adhesion cluster can be thought of as a multistep discrete process, in which one of the bond sub-populations ruptures first, followed by similar rupture steps of other sub-populations or by immediate detachment of the remaining cluster. This rupture behavior is qualitatively independent of involved bond types, such as slip and catch bonds. Interestingly, an optimal stability is generally achieved when the total cluster load is shared such that loads on distinct bond populations are equal to their individual critical rupture forces. We also show that cluster heterogeneity can drastically affect cluster lifetime.Comment: 11 pages, 8 figure

Deformation Quantization of Almost Kahler Models and Lagrange-Finsler Spaces

Finsler and Lagrange spaces can be equivalently represented as almost Kahler manifolds enabled with a metric compatible canonical distinguished connection structure generalizing the Levi Civita connection. The goal of this paper is to perform a natural Fedosov-type deformation quantization of such geometries. All constructions are canonically derived for regular Lagrangians and/or fundamental Finsler functions on tangent bundles.Comment: the latex 2e variant of the manuscript accepted for JMP, 11pt, 23 page

Scalar Casimir Energies of Tetrahedra

New results for scalar Casimir self-energies arising from interior modes are presented for the three integrable tetrahedral cavities. Since the eigenmodes are all known, the energies can be directly evaluated by mode summation, with a point-splitting regulator, which amounts to evaluation of the cylinder kernel. The correct Weyl divergences, depending on the volume, surface area, and the corners, are obtained, which is strong evidence that the counting of modes is correct. Because there is no curvature, the finite part of the quantum energy may be unambiguously extracted. Dirichlet and Neumann boundary conditions are considered and systematic behavior of the energy in terms of geometric invariants is explored.Comment: Talk given at QFEXT 1

Behaviour of the von Willebrand Factor in Blood Flow

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The von Willebrand factor (vWF), a large multimeric protein, is essential in hemostasis. Under normal conditions, vWF is present in blood as a globular polymer. However, in case of an injury, vWF is able to unwrap and bind to the vessel wall and to flowing platelets. Thus, platelets are significantly slowed down and can adhere to the wall and close the lesion. Nevertheless, it is still not clear how the unwrapping of the vWF is triggered. To better understand these complex processes, we employ a particle-based hydrodynamic simulation method to study the behaviour of vWF in blood flow. The vWF is modelled as a chain of beads (monomers) connected by springs. In addition, the monomers are subject to attractive interactions in order to represent characteristic properties of the vWF. The behaviour of vWF is investigated under different conditions including a freely-suspended polymer in shear flow and a polymer attached to a wall. We also examine the migration of vWF to a wall (margination) depending on shear rate and volume fraction of red blood cells (RBCs). Furthermore, the stretching of the vWF in flow direction depending on its radial position in a capillary is monitored. Our results show that attractive interactions between monomer beads increase margination efficiency and significantly affect the extension of vWF at different radial positions in blood vessels

Blood Flow in silico: From Single Cells to Blood Rheology

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Mesoscale hydrodynamics simulations of red blood cells under flow have provided much new insight into their shapes and dynamics in microchannel flow. The presented results range from the behavior of single cells in confinement and the shape changes in sedimentation, to the clustering and arrangement of many cells in microchannels and the viscosity of red blood cell suspensions under shear flow. The interaction of red blood cells with other particles and cells, such as white blood cells, platelets, and drug carriers, shows an essential role of red blood cells in the margination of other blood components

Comparison of Recombinant Human Haptocorrin Expressed in Human Embryonic Kidney Cells and Native Haptocorrin

Haptocorrin (HC) is a circulating corrinoid binding protein with unclear function. In contrast to transcobalamin, the other transport protein in blood, HC is heavily glycosylated and binds a variety of cobalamin (Cbl) analogues. HC is present not only in blood but also in various secretions like milk, tears and saliva. No recombinant form of HC has been described so far. We report the expression of recombinant human HC (rhHC) in human embryonic kidney cells. We purified the protein with a yield of 6 mg (90 nmol) per litre of cell culture supernatant. The isolated rhHC behaved as native HC concerning its spectral properties and ability to recognize both Cbl and its baseless analogue cobinamide. Similar to native HC isolated from blood, rhHC bound to the asialoglycoprotein receptor only after removal of terminal sialic acid residues by treatment with neuraminidase. Interestingly, rhHC, that compared to native HC contains four excessive amino acids (…LVPR) at the C-terminus, showed subtle changes in the binding kinetics of Cbl, cobinamide and the fluorescent Cbl conjugate CBC. The recombinant protein has properties very similar to native HC and although showing slightly different ligand binding kinetics, rhHC is valuable for further biochemical and structural studies

Сравнительный анализ ИТ-продуктов для страхового сектора российской экономики

The article is devoted to the comparative analysis of IT-products for the insurance sector of the Russian economy. Within the research the comparative analysis of the software products focused on the insurance sector of economy is carried out, the main criteria for the comparative analysis of information systems for the insurance sector are developed and proved, the expert assessment of four information systems for the insurance sector of the Russian economy is carried out by the method of the analysis of hierarchies.El artículo está dedicado a un análisis comparativo de productos de TI para el sector de seguros de la economía rusa. En el marco del estudio, se realizó un análisis comparativo de productos de software orientados al sector de seguros de la economía, se desarrollaron y corroboraron los criterios principales para un análisis comparativo de los sistemas de información para el sector de seguros, y se realizó una evaluación experta de cuatro sistemas de información para el sector de seguros de la economía rusa mediante el método de análisis de jerarquía.Статья посвящена сравнительному анализу ИТ-продуктов для страхового сектора российской экономики. В рамках исследования проведен сравнительный анализ программных продуктов, ориентированных на страховой сектор экономики, разработаны и обоснованы основные критерии для сравнительного анализа информационных систем для страхового сектора, проведена экспертная оценка четырех информационных систем для страхового сектора российской экономики методом анализа иерархий

A zeta function approach to the relation between the numbers of symmetry planes and axes of a polytope

A derivation of the Ces\`aro-Fedorov relation from the Selberg trace formula on an orbifolded 2-sphere is elaborated and extended to higher dimensions using the known heat-kernel coefficients for manifolds with piecewise-linear boundaries. Several results are obtained that relate the coefficients, $b_i$, in the Shephard-Todd polynomial to the geometry of the fundamental domain. For the 3-sphere we show that $b_4$ is given by the ratio of the volume of the fundamental tetrahedron to its Schl\"afli reciprocal.Comment: Plain TeX, 26 pages (eqn. (86) corrected

Deep-water Buccinidae (Gastropoda: Neogastropoda) from sunken wood, vents and seeps: molecular phylogeny and taxonomy

International audienceBuccinidae-like other canivorous and predatory molluscs-are generally considered to be occasional visitors or rare colonizers in deep-sea biogenic habitats. However, casual observations during tropical deep-sea cruises suggest that associations between buccinids and sunken wood, in particular, are not fortuitous. Enigmatocolus monnieri has been found to co-occur in Madagascar with bathymodiolines, vesicomyids and solemyids, indicating the presence of seeps, and species of Thermosipho gen. nov. have been sampled by submersibles and ROVs, exclusively from hydrothermal vents. A molecular phylogeny (based on CO1, 12S and 28S genes) reveals that buccinid genera potentially associated with sunken wood (Eosipho, Gaillea gen. nov., Calagrassor gen. nov., and Manaria) are closely related to taxa from vents (Thermosipho gen. nov.) and seeps (Enigmaticolus). The anatomy of several dissected species did not reveal any special trait that could be interpreted as a special adaptation to biogenic substrates. Buccinids from sunken wood are most diverse in the Indopacific centre of marine biodiversity, the "Coral Triangle", at depths between 100 and 1000 meters, with numerous species still undescribed

∗\ast-SDYM fields and heavenly spaces: II. Reductions of the ∗\ast-SDYM system

Reductions of self-dual Yang-Mills (SDYM) system for $\ast$-bracket Lie algebra to the Husain-Park (HP) heavenly equation and to sl(N,{\boldmath{C}) SDYM equation are given. An example of a sequence of $su(N)$ chiral fields ($N\geq 2$) tending for $N\to\infty$ to a curved heavenly space is found.Comment: 18 page