We discuss the use of K-terminal networks to represent arbitrary clutters. A given clutter has many di¤erent representations, and there does not seem to be any set of simple transformations that can be used to transform one representation of a clutter into any other. We observe that for t 2 the class of clutters that can be represented using no more than t terminals is closed under minors, and ...

A generalized Davenport-Schinzel sequence is one over a finite alphabet that contains no subsequences isomorphic to a fixed forbidden subsequence. One of the fundamental problems in this area is bounding (asymptotically) the maximum length of such sequences. Following Klazar, let Ex(σ, n) be the maximum length of a sequence over an alphabet of size n avoiding subsequences isomorphic to σ. It ha...

Reservoir characterization This paper gives an overview of the activities in geostatistics for the Petroleum industry in the domain of reservoir characterization. This description has been simplified in order to emphasize the original techniques involved. The main steps of a study consist in successively building: • the reservoir architecture where the geometry of the units is established, • th...

This paper characterizes revenue maximizing auctions for a …nite horizon version of the standard IV P model of Myerson (1981) for a seller who cannot commit not to propose a new mechanism, if previously chosen ones fail to allocate the object. We show that a revenue maximizing mechanism in the …rst period assigns the good to the buyer with the highest virtual valuation, provided that it is abov...

silica  coated magnetite  nanoparticles were  covalent  grafted with  3-aminopropyl trimethoxysilane  to give aptscmnps. reaction of  the resulted nanomaterial with 4-formyl benzo-12-crown-4 ether afforded fb12c4/aptsmnps  nanocomposite  material  in  which  the  crown ether  moiety  was  attached  through  propyl  chain  spacer. characterization of  the prepared nanocomposite was performed wit...

High-resolution transmission electron microscopy characterization of molybdenum oxide catalyst precursors is carried out for a better understanding of the mechanisms leading to the active catalytic material. The precipitated material consists of both large-unit cell crystals and randomly orientated clusters on a 3-5 nm scale. The crystalline clusters are embedded in non-crystalline material, pr...

In this paper, we explore the effects of certain forbidden substructure conditions on preordered sets. In particular, we characterize in terms of these conditions those preordered sets which can be represented as the supremum of a well-ordered ascending chain of lowersets whose members are constructed by means of alternating applications of disjoint union and ordinal sums with chains. These dec...

Biosurfactants can be classified by their chemical composition and their origin. This review briefly describes various classes of biosurfactants based on their origin and introduces a few of the most widely used biosurfactants. The current status and future trends in biosurfactant production are discussed, with an emphasis on those derived from plants. Following a brief introduction of the prop...

The graph theoretic problem of identifying the finite sets C of constraint graphs for which there is a countable universal C-free graph is closely related to the problem of determining for which sets C the model companion T ∗ C of the theory of C-free graphs is א0-categorical, and this leads back to combinatorics. Little is known about these theories from any other perspective, such as stabilit...