In multistage interconnection networks used for switching in ATM, low level flow control mechanisms such as backpressure are used to regulate the flow of cells between stages to prevent cells from being lost due to buffer overflow. This is accomplished by signalling the upstream neighbour granting permission to send a cell where there is free buffer space for the cell to be received in the swit...

Removal of MTA from dentin by applying 37% hydrochloric acid (HCl) to reduce microhardness and push-out bond strength. Forty dentin slices were filled with WMTA and divided into two groups (n = 20). Ten slices remained untreated while others were exposed to either HCl or phosphate buffer saline (PBS) and all samples were subjected to pushout test. The mode of bond failures was determined by SEM...

A central concept in algebraic topology since the 1970's has been that of delooping machine [4] [23] [29]. Such a " machine " corresponds to a notion of H-space, or space with a multiplication satisfying associativity, unity and inverse properties up to homotopy in an appropriate way, including higher order coherences as first investigated in [33]. A delooping machine is a specification of the ...

Domain-speci c rule-based languages to represent the systems of reactions that occur inside cells, such as Kappa and BioNetGen, have attracted signi cant recent interest. For these models, powerful simulation and static analysis techniques have been developed to understand the behaviour of the systems that they represent, and these techniques can be transferred to other elds. The languages can ...

The focus of this paper is to endow step-wise modification of nets with refinement that preserves liveness. Modification of nets uses rules that allow substituting subnets of the left hand side by subnets of the right hand side of the rule. Such rules are then restricted so that the liveness is preserved. Rule-based modification is expressed in terms of spans of morphisms and two pushout constr...

We tackle the problem of graph transformation with particular focus on node cloning. We propose a new approach to graph rewriting, called polarized node cloning, where a node may be cloned together with either all its incident edges or with only its outgoing edges or with only its incoming edges or with none of its incident edges. We thus subsume previous works such as the sesqui-pushout, the h...

We present a new approach to rewriting obtained by enhancing and unifying existing variants inside the algebraic (or better categorical) approach to (graph) rewriting. Our approach is motivated by second-order term graph rewriting and stresses on one hand the two-step nature of rule application consisting of deleting and adding items and on the other hand the heterogeneous nature of the rewriti...

INTRODUCTION Biomechanical properties of four different commercially available small fragment cannulated screws (Twin fix (Stryker, Freiburg, Germany), Herbert, (Zimmer, Warsaw, USA), Omnitech (Unimedical, Torino, Italy), Barouk (Depuy, Warsaw, USA)), with variable pitch, used for fracture fixation were compared. MATERIALS AND METHODS Polyurethane foam blocks of three different densities with...