pinecone/core-2020-05-10-deduplication huggingface dataset:
Surface waters of the NW Iberian margin: Upwelling on the shelf versus outwelling of upwelled waters from the Rías Baixas

17 páginas, 1 apéndice, 7 figuras, 3 tablasA set of hydrographic surveys were carried out in the Ría of Vigo (NW Spain) at 2–4 d intervals during four 2–3 week\ud
periods in 1997, covering contrasting seasons. Residual exchange fluxes with the adjacent shelf were estimated with a\ud
2-D, non-steady-state, salinity–temperature weighted box model. Exchange fluxes consist of a steady-state term\ud
(dependent on the variability of continental runoff) and a non-steady-state term (dependent on the time changes of\ud
density gradients in the embayment). More than 95% of the short-time-scale variability of the exchange fluxes in the\ud
middle and outer rı´a can be explained by the non-steady-state term that, in turns, is correlated (R2>75%) with the\ud
offshore Ekman transport. Conversely, 96% of the variability of exchange fluxes in the inner rı´a rely on the steady-state\ud
term. The outer and middle rı´a are under the direct influence of coastal upwelling, which enhances the positive residual\ud
circulation pattern by an order of magnitude: from 102 to 103 m3 s 1. On the contrary, downwelling provokes a reversal\ud
of the circulation in the outer rı´a. The position of the downwelling front along the embayment depends on the relative\ud
importance of Ekman transport (Qx, m3 s 1 km 1) and continental runoff (R, m3 s 1). When Qx/R>7 2 the reversal\ud
of the circulation affects the middle rı´a. Our results are representative for the ‘Rı´as Baixas’, four large coastal indentations\ud
in NW Spain. During the upwelling season (spring and summer), 60% of shelf surface waters off the ‘Rı´as Baixas’ consist\ud
of fresh Eastern North Atlantic Central Water (ENACW) upwelled in situ. The remaining 40% consists of upwelled\ud
ENACW that previously enters the rı´as and it is subsequently outwelled after thermohaline modification. During the\ud
downwelling season (autumn and winter), 40% of the warm and salty oceanic subtropic surface water, which piled on the\ud
shelf by the predominant southerly winds, enters the rías.Financial support for this work came from\ud
CICYT Grant No. AMB95-1084.Peer reviewe
King Solomon's Miners- Starvation and Bioaccumulation? An Environmental Archaeological Investigation in Southern Jordan

Pyatt, B. Barker, G. Birch, P. Gilbertson, D. Grattan, J. Mattingly, D. King Solomon's Miners - Starvation and Bioaccumulation? An Environmental Archaeological Investigation in Southern Jordan. Ecotoxicology and Environmental safety 43, 305-308 (1999) Environmental Research, Section BCopper mining and smelting were important activities in various predesert wadis during the Iron Age, Nabatean, Roman, and Byzantine periods in southern Jordan and major spoil tips to gether with slag heaps remain as a legacy of such enterprises. Barley has grown in the area for a prolonged period and currently wild barley plants are affected by toxic cations, which reduce their yields. It is considered that such plants provide an adequate model to assess how similar plants would have performed, in terms of productivity, in the past. The population of miners/slaves, guards, etc., would have been subject to bioac cumulation of heavy metals, which conceivably would have led to detrimental effects on their health. Inhalation and ingestion of particulate pollutants cannot be discounted. It is argued that the population may have been further weakened as a consequence of food shortage, due to reduced plant productivity, as cereals are important foods for both humans and the animals upon which they are dependent. A sizeable mining community could only have been maintained by large-scale importation of food or a massive intensification of agricultural activity.Peer reviewe
Optical Algal Biosensor using Alkaline Phosphatase for Determination of Heavy Metals

International audienceA biosensor is constructed to detect heavy metals from inhibition of alkaline phosphatase (AP) present on the external membrane of Chlorella vulgaris microalgae. The microalgal cells are immobilized on removable membranes placed in front of the tip of an optical fiber bundle inside a homemade microcell. C. vulgaris was cultivated in the laboratory and its alkaline phosphatase activity is strongly inhibited in the presence of heavy metals. This property has been used for the determination of those toxic compounds
How lead exposure relates to temporal changes in IQ, violent crime, and unwed pregnancy

This study compares changes in children’s blood lead levels in the United States with subsequent changes in IQ, based on norm comparisons for the Cognitive Abilities Test (CogAT) given to representative national samples of children in 1984 and 1992. The CogAT norm comparisons indicate shifts in IQ levels consistent with the blood lead to IQ relationship reported by an earlier study and population shifts in average blood lead for children under age six between 1976 and 1991. The CogAT norm comparisons also support studies indicating that the IQ to blood lead slope may increase at lower blood lead levels. Furthermore, long term trends in population exposure to gasoline lead were found to be remarkably consistent with subsequent changes in violent crime and unwed pregnancy. Long term trends in paint and gasoline lead exposure are also strongly associated with subsequent trends in murder rates going back to 1900. The findings on violent crime and unwed pregnancy are consistent with published data describing the relationship between IQ and social behavior. The findings with respect to violent crime are also consistent with studies indicating that children with higher bone lead tend to display more aggressive and delinquent behavior. This analysis demonstrates that widespread exposure to lead is likely to have profound implications for a wide array of socially undesirable outcomes.
Chromatic Ramsey Theory

AbstractLet G be a countable graph which has infinite chromatic number. Ifγis a coloring of [G]2with two colors, is there then a subsetH⊆Gsuch thatγis constant on [H]2andG|H,the graph induced by G onH,has infinite chromatic number? As edges and non-edges can be colored with different colors this will be the case iff G contains an infinite clique. It turns out that if the clique size of G is unbounded but G does not contain an infinite clique then for every coloring of [G]2withτcolors, there are some two of theτcolors such that there is an infinite chromatic subgraph of G the vertex set of which forms only pairs colored in those two colors; and this is best possible, because one can always distinguish between edges and non-edges. In the case in which the graphs do not contain the complete graph onnvertices the situation is much more complicated. We will show that for every 3≤n ∈οthere is a graph G, which does not embed the complete graph onnvertices, with the property that for every positive numberτthere exists a coloring of [G]2withτcolors such that the vertex set of every infinite chromatic subgraph of G forms pairs in each of theτcolors. On the other hand there is a graph G, which does not embed the complete graph onnvertices, and which has the property that for every positive numberτand every coloring of [G]2withτcolors there is an infinite chromatic subgraph of G the pairs of which use at most 3 colors. We will generalize to the case of colorings ofk-element subsets
Antipodal Distance-transitive Covers of Complete Bipartite Graphs

AbstractThis paper completes the classification of antipodal distance-transitive covers of the complete bipartite graphsKk,k,wherek≥3.For such a cover the antipodal blocks must have sizer≤k.Although the caser=khas already been considered, we give a unified treatment ofr≤k.We use deep group-theoretic results as well as representation-theoretic data about explicit linear groups and group coset geometries.Apart from the generic examples arising from finite projective spaces, there are three sporadic examples (arising from the outer automorphisms of the symmetric groupS6and of the Mathieu groupM12and one related to non-abelian Singer groups onPG2(4))and an infinite family having solvable automorphism group (and with parametersr=qb, k=qa,where(qb-1)gcd(b,q-1)divides2a(q-1)andqis a prime power)
A New Game Chromatic Number

AbstractConsider the following two-person game on a graphG.Players I and II move alternatively to color a yet uncolored vertex ofGproperly using a pre-specified set of colors. Furthermore, Player II can only use the colors that have been used, unless he is forced to use a new color to guarantee that the graph is colored properly. The game ends when some player can no longer move. Player I wins if all vertices ofGare colored. Otherwise Player II wins. What is the minimal numberχg*(G)of colors such that Player I has a winning strategy? This problem is motivated by the game chromatic numberχg(G)introduced by Bodlaender and by the continued work of Faigle, Kern, Kierstead and Trotter. In this paper, we show thatχg*(T) ≤3for each treeT.We are also interested in determining the graphsGfor whichχ(G)= χg*(G),as well asχg*(G)for thek-inductive graphs wherekis a fixed positive integer
Transformations of a Graph Increasing its Laplacian Polynomial and Number of Spanning Trees

AbstractLetGrmndenote the set of simple graphs withnvertices andmedges,t(G)the number of spanning trees of a graphG,andL(λ,G)the Laplacian polynomial ofG.We give some operationsQon graphs such that ifG∈GrmnthenQ(G)∈GrmnandL(λ, G)≤L(λ,Q(G))forλ≤n.Because of the relationt(Ks\E(Gn)) =srs-n-2L(s,Gn) [5],these operations also increase the number of spanning trees of the corresponding complement graphs:t(Ks\E(G)) ≤ t(Ks\E(Q(G)).The approach developed can be used to find some other graph operations with the same property
On Dihedral Configurations and their Coxeter Geometries

AbstractWithin the theory of homogeneous coherent configurations, the dihedral configurations play the role which is played by the finite dihedral groups in the theory of finite groups. Imitating Tits’ construction of a geometry from a set of subgroups of a given group, we assign a geometry of rank 2 to each dihedral configuration, its ‘Coxeter geometry’. (Each finite generalized polygon is a Coxeter geometry in this sense.)Apart from general results on the relationship between dihedral configurations and their Coxeter geometries, we settle completely the (ordinary) representation theory of the dihedral configurations of rank 7. We obtain three major classes. The Coxeter geometries of the first class are exactly the non-symmetric 2-designs withI=1. The other two classes lead to questions which require a further combinatorial treatment
D-bounded Distance-regular Graphs

AbstractLet Γ=(X, R) denote a distance-regular graph with diameterD≥3 and distance functionδ. A (vertex) subgraph Δ⊆Xis said to beweak-geodetically closedwhenever for allx, y∈Δ and allz∈X,δ(x, z)+δ(z, y)≤δ(x, y)+1→z∈Δ.Γis said to beD-boundedwhenever, for allx, y ∈X, xandyare contained in a common regular weak-geodetically closed subgraph of diameterδ(x, y).Assume that Γ isD-bounded. LetP(Γ)denote the poset the elements of which are the weak-geodetically closed subgraphs of Γ with partial order by reverse inclusion. We obtain new inequalities for the intersection numbers of Γ; equality is obtained in each of these inequalities iff the intervals inP(Γ)are modular. Moreover, we show this occurs if Γ has classical parameters andD≥4.We obtain the following corollary without assuming Γ to beD-bounded:COROLLARY.Let Γ denote a distance-regular graph with classical parameters (D, b, α, β) and D≥4. Suppose that b<-1, and suppose the intersection numbers a1≠0 and c2>1. Thenβ=α1+bD1−
A New Family of Extended Generalized Quadrangles

AbstractFor every hyperovalOofPG(2,q) (qeven), we construct an extended generalized quadrangle with point-residues isomorphic to the generalized quadrangleT*2(O) of order(q-1,q+1).These extended generalized quadrangles are flag-transitive only whenq=2 or 4. Whenq=2 we obtain a thin-lined polar space with four planes on every line. Whenq=4 we obtain one of the geometries discovered by Yoshiara [28]. That geometry is produced in [28] as a quotient of another one, which is simply connected, constructed in [28] by amalgamation of parabolics. In this paper we also give a ‘topological’ construction of that simply connected geometry
Twelve Countings with Rooted Plane Trees

AbstractThe average numbers of (1) antichains, (2) maximal antichains, (3) chains, (4) infima closed sets, (5) connected sets, (6) independent sets, (7) maximal independent sets, (8) brooms, (9) matchings, (10) maximal matchings, (11) linear extensions and (12) drawings in (of) a rooted plane tree onnvertices are investigated. Using generating functions we determine the asymptotics and give some explicit formulae and identities. In conclusion, we discuss the extremal values of the above quantitites and pose some problems
Subsets with Small Sums in Abelian Groups' I: the Vosper Property

AbstractLetGbe an abelian group containing a finite subsetBsuch that, for every non-empty finite subsetA⊂G, |A+B|≥min(|G|,|A|+|B|-1).We obtain the necessary and sufficient condition for the validity of the stronger property:For every finite subset A⊂G, such that |A|≥2, |A+B|≥min(|G|-1,|A|+|B|).We apply our methods to the range of diagonal forms over finite fields, obtaining a new proof of a result of Tietäväinen. Our proof works in characteristic 2, where the question was open. We also apply our methods to obtain a new characterization for abelian Cayley graphs for which each minimum cutset originates or ends in a vertex
Closed 2-cell Embeddings of 5-crosscap Embeddable Graphs

AbstractThe strong embedding conjecture states that every 2-connected graph has a closed 2-cell embedding in some surface, i.e. an embedding that each face is bounded by a circuit in the graph. A graph is calledk-crosscap embeddable if it can be embedded in the surface of non-orientable genusk.We confirm the strong embedding conjecture for 5-crosscap embeddable graphs. As a corollary, every such graph has a cycle double cover, i.e. a set of circuits containing every edge exactly twice. We classify simple closed curves in the surface of 3-crosscap graphs and study some topological properties of simple closed curves in the torus and the punctured torus
On abab-free and abba-free Set Partitions

AbstractThese are partitions of[l]={1,2,... ,l}intonblocks such that no four-term subsequence of [l]induces the mentioned pattern and eachkconsecutive numbers of[l]fall into different blocks. These structures are motivated by Davenport–Schinzel sequences. We summarize and extend known enumeriative results for the patternp=ababand give an explicit formula for the numberp(abab,n,l,k)of such partitions. Our main tools are generating functions. We determine the corresponding generating function forp=abbaandk=1,2,3.Fork=2there is a connection with the number of directed animals. We solve exactly two related extremal problems
A Family of Inequalities for Intersecting Antichain of Subsets of an n-set

AbstractThere are two seemingly unrelated inequalities for the intersecting antichain of subsets of ann-element set. One was obtained by Bollobás in 1973 and the other was obtained by Greene, Katona and Kleitman in 1976. By introducing a new family of non-negative real valued set functions and applying cyclic permutation approach, a family of more general inequalities is obtained. The left-hand sides of the inequalities of Bollobás and Greeneet al.are just the two extreme values of a linear function which appears in the left-hand side of one of our special family of inequalities. Furthermore, some new inequalities are provided
Graphs of Acyclic Cubical Complexes

AbstractIt is well known that chordal graphs are exactly the graphs of acyclic simplicial complexes. In this note we consider the analogous class of graphs associated with acyclic cubical complexes. These graphs can be characterized among median graphs by forbidden convex subgraphs. They possess a number of properties (in analogy to chordal graphs) not shared by all median graphs. In particular, we disprove a conjecture of Mulder on star contraction of median graphs. A restricted class of cubical complexes for which this conjecture would hold true is related to perfect graphs
T-theory: An Overview

AbstractT-theory is the name that we adopt for the theory of trees, injective envelopes of metric spaces, and all of the areas that are connected with these topics, which has been developed over the past 10–15 years in Bielefeld. Its motivation was originally—and still is to a large extent—the development of mathematical tools for reconstructing phylogenetic trees.T-theory expanded considerably when its relationships with the theory of affine buildings, valuated matroids, and decompositions of metrics were discovered. In this paper, we give a brief introduction to this theory, which we hope will serve as a useful reference to some of the main results, and also as a guide for further investigations into whatT-theory has to offer
A Combinatorial Construction For Twin Trees

AbstractThe notions of abuilding [6]and, later, atwin building[7] were introduced to give an axiomatical geometric treatment of groups with BN-pairs and with twin BN-pairs. For this reason, buildings and twin buildings have always been studied from a point of view relevant to (and originated from) BN-pairs.The notion of atwin tree,an affine twin building of rank 2, was introduced in [2] by a self-contained, very elementary and geometric definition. The study of twin trees in [2–4], and the explicit constructions given there, also use notions and groups inspired by BN-pairs.In this paper we shall present an elementary combinatorial construction for twin trees which, in a sense, is orthogonal to the BN-pairs approach. This construction gives all twin trees; in particular, it provides an easy proof that twin trees of any given valency are uncountably many (a result proved independently by M. Ronan [1]).Our approach turns out to be especially fruitful for twin trees of valency 3 (and probably of valency 4; that part of the work is still in progress). In particular, it highlights a new geometric object (a pairing)within a twin tree—and hence a new class of subgroups of its automorphism group. When the twin tree in question has a ‘rich’ automorphism group, study of these objects (and corresponding subgroups) gives a lot of new and unexpected information on combinatorial and group-theoretic structure of the twin tree
On the Complexity of Recognizing Hamming Graphs and Related Classes of Graphs

AbstractThis paper contains a new algorithm that recognizes whether a given graphGis a Hamming graph, i.e. a Cartesian product of complete graphs, inO(m)time andO(n2)space. Heremandndenote the numbers of edges and vertices ofG,respectively. Previously this was only possible inO(mlogn)time.Moreover, we present a survey of other recognition algorithms for Hamming graphs, retracts of Hamming graphs and isometric subgraphs of Hamming graphs. Special emphasis is also given to the bipartite case in which these classes are reduced to binary Hamming graphs, median graphs and partial binary Hamming graphs
Minimum (2,r)-Metrics and Integer Multiflows

AbstractLetH=(T, U)be a connected graph. AT-partitionof a setV⊇Tis a partition ofVinto subsets, each containing exactly one element ofT.We start with the following problem (*): given a multigraphG=(V, E)withV⊇T,find aT-partition Π ofVthat minimizes the sum of productsd(s, t)n(s, t)over alls,t∈T.Hered(s, t)is the distance fromstotinHandn(s, t)is the number of edges ofGbetween the sets in Π that containsandt.When the graphHis complete, (*) turns into the minimum multiway cut problem, which is known to be NP-hard even if|T|=3.On the other hand, whenHis the complete bipartite graphK2,rwith parts of 2 andr=|T|−2nodes, (*) is specialized to be the minimum (2,r)-metric problem, which can be solved in polynomial time.We prove that the multicommodity flow problem dual of the minimum (2,r)-metric problem has an integer optimal solution wheneverGisinner Eulerian(i.e. the degree of each node inV−Tis even), and such a solution can be found in polynomial time.Another nice property ofK2,ris that, independently ofG,the optimum objective value in (*) is the same as that in its factional relaxation. We call a graphHwith a similar propertyminimizableand give a description of the minimizable graphs in polyhedral terms. Finally, we show that every tree is minimizazble
Gap Inequalities for the Cut Polytope

AbstractWe introduce a new class of inequalities valid for the cut polytope, which we call gap inequalities. Each gap inequality is given by a finite sequence of integers, the ‘gap’ being defined as the smallest discrepancy arising when decomposing the sequence into two parts that are as equal as possible. Gap inequalities include hypermetric inequalities and negative type inequalities, which have been extensively studied in the literature. They are also related to a positive semidefinite relaxation of the max-cut problem.A natural question is to decide for which integer sequences the corresponding gap inequalities define facets of the cut polytope. For this property, we present a set of necessary and sufficient conditions in terms of the root patterns and of the rank of an associated matrix. We also prove that there is no facet defining inequality with gap greater than one and which is induced by a sequence of integers using only two distinct values
Ubiquity in Category for Metric Spaces and Transition Systems

AbstractWe characterize the notion of ubiquity in category, introduced and developed by P. J. Cameron since 1985, in terms of prehomogeneity, a notion introduced by J. F. Pabion for relational structures in 1972. We apply this characterization first to metric spaces and particularly graphs equipped with the graphic distance, and then to transition systems. The transition system that we display on this occasion has the same homogeneity properties as Rado’s graph and could have similar randomness properties
Consequences of the Brylawski–Lucas Theorem for Binary Matroids

AbstractThe principal theme of the present paper is to consider isomorphism classes of binary matroids as orbits of a suitable group action. This interpretation is based on a theorem of Brylawski–Lucas. A refinement of the Burnside Lemma is used in order to enumerate these orbits. Ternary matroids are dealt with in much the same way (Section 2). Counting regular matroids is more difficult, but their number can be estimated with an arbitrarily small relative error (Section 3). Other applications of the Brylawski–Lucas Theorem include checking binary matroids for isomorphism (Section 4) and for graphicness (Section 5)
Percolation Models and Animals

AbstractWe first define site- and bond-percolation models on a general graph. We underline the link between the percolation probability and the enumeration of animals. Next, we focus on certain polynomials introduced as approximants to the percolation probability for several specific graphs. We show that such polynomials can be defined for any graph and explain why they often converge in the algebra of formal power series.The difference between these polynomials—denotedPn(q)—and their formal limitP∞(q)is characterized by a doubly indexed family of correction termsdn,k. These correction terms play an important role, since they permit to extend the expansion ofP∞(q)whenPn(q)can no longer be computed. For a givenk, thedn,k's are related to ‘compact’ animals, i.e. animals with small site-perimeter with respect to their height. These animals are often easier to enumerate than general animals, and this is why some researchers were able to conjecture formulas fordn,k, forksmall, over several specified graphs. We prove some of these formulas: for site and bond directed percolation on the square lattice, and for bond directed percolation on the honeycomb lattice