Movement within eukaryotic cells largely originates from localized forces exerted by myosin motors on scaffolds of actin filaments. Although individual motors locally exert both contractile and extensile forces, large actomyosin structures at the cellular scale are overwhelmingly contractile, suggesting that the scaffold serves to favor contraction over extension. While this mechanism is well u...

Experimental observations are reported for the laminar flow of a viscoelastic liquid through a symmetrical plane sudden expansion preceded by a gradual contraction from a square duct. As is well known, for Newtonian fluid flow above a critical Reynolds number the flowfield downstream of an expansion becomes asymmetric. For the viscoelastic liquid investigated here the asymmetry is greatly reduc...

Kernel contraction is an interesting problem that can be considered a step towards belief revision. Kernels were introduced as a tool to determine why a given belief is accepted by the knowledge base. The aim of using kernels is to invalidate the reasons why that given belief is accepted, and hence rejecting that belief. We use Description Logic EL for two reasons: it is used in some large know...

Contraction Hierarchies are an experimentally well studied method to efficiently handle point-topoint shortest-path queries in large graphs. In a preprocessing stage the vertices of the input graph are iteratively removed, while the shortest-path structure of the remaining graph is preserved. This results in a hierarchy of graphs and shortest-path queries can be answered by only considering edg...

Isolated cardiac myocytes exhibit spontaneous patterns of rhythmic contraction, driven by intracellular calcium waves. In order to study the coupling between spatio-temporal calcium dynamics and cell contraction in large deformation regimes, a new strain-energy function, describing the influence of sarcomere length on the calcium-dependent generation of active intracellular stresses, is propose...

This study examines the roles of voltage-dependent Ca(2+) channels (VDCC), ryanodine receptors (RyRs), large-conductance Ca(2+)-activated K(+) (BK) channels, and small-conductance Ca(2+)-activated K(+) (SK) channels in the regulation of phasic contractions of guinea pig urinary bladder smooth muscle (UBSM). Nisoldipine (100 nM), a dihydropyridine inhibitor of VDCC, abolished spontaneous UBSM co...

The exercise pressor reflex is evoked by both mechanical and metabolic stimuli. Tendon stretch does not increase muscle metabolism and therefore is used to investigate the mechanical component of the exercise pressor reflex. An important assumption underlying the use of tendon stretch to study the mechanical component of the exercise pressor reflex is that stretch stimulates the same group III ...

Actomyosin contractility is essential for biological force generation, and is well understood in highly organized structures such as striated muscle. Additionally, actomyosin bundles devoid of this organization are known to contract both in vivo and in vitro, which cannot be described by standard muscle models. To narrow down the search for possible contraction mechanisms in these systems, we i...

Methods From a large urodynamic data base we retrospectively evaluated 358 patients (131 males and 227 females) who underwent filling cystometry and flow-pressure study for lower urinary tract symptoms (LUTS), neurological diseases or post-operative follow-up. Methods, definitions and units conform to the standards recommended by the International Continence Society, except where specifically n...

We present a new method to determine contraction kernels for the construction of graph pyramids. The new method works with undirected graphs and yields a reduction factor of at least 2.0. This means that with our method the number of vertices in the subgraph induced by any set of contractible edges is reduced to half or less by a single parallel contraction. Our method yields better reduction f...