bluuebunny/crossref_metadata_2025 huggingface dataset:
On an adjacency property of graphs
Authors: Exoo Geoffrey
Published: May 2007

A graph G has property A(m, n, k) if for any sequence of m + n distinct points of G, there are at least k other points, each of which is adjacent to the first m points of the sequence but not adjacent to any of the latter n points. the minimum order among all graphs with property A(m, n, k) is denoted a(m, n, k). Bounds are given on the numbers a(m, n, k) and some exact results are indicated.
Characterizations of signed graphs
Authors: Zaslavsky Thomas
Published: May 2007

The possible classes of balanced circles of a signed graph are characterized in two ways.
Locally homogeneous graphs from groups
Authors: Vince Andrew
Published: May 2007

A graph is called locally homogeneous if the subgraphs induced at any two points are isomorphic. in this Note we give a method for constructing locally homogeneous graphs from groups. the graphs constructable in this way are exactly the locally homogeneous graphs with a point symmetric universal cover. As an example we characterize the graphs that are locally n‐cycles.
Constructions of covering triangulations with folds
Authors: Bouchet André
Published: May 2007

Let G be a graph with a known triangular embedding in a surface S, and consider G(m), the composition of G with an independant set of order m. The purpose of this paper is to construct a triangular embedding of G(m) into a surface magnified image by using a covering triangulation with folds. We make the construction for three cases. One of them is used for proving that G(m) can be triangularly embedded into a surface magnified image if G is an Eulerian graph which can be triangularly embedded into a surface S with the same orientability characteristic as magnified image.
The connectivities of line and total graphs
Authors: Bauer Douglas , Tindell Ralph
Published: May 2007

Sharp lower bounds for the point connectivity and line connectivity of the line graph L(G) and the total graph T(G) of a graph G are determined. The lower bounds are expressed in terms of the point connectivity k, line connectivity λ, and minimum degree δ of G. It is also shown that 2λ is an upper bound for k(T(G)) and that λ(T(G))= 2δ = δ(T(G)). In each case the realizable values beyond the lower bound are determined.
A counterexample to a conjecture on paths of bounded length
Authors: Boyles Stephanie M. , Exoo Geoffrey
Published: May 2007

In a recent paper Lovász, Neumann‐Lara, and Plummer studied Mengerian theorems for paths of bounded length. Their study led to a conjecture concerning the extent to which Menger's theorem can fail when restricted to paths of bounded length. In this paper we offer counterexamples to this conjecture.
A relationship between triangulated graphs, comparability graphs, proper interval graphs, proper circular‐arc graphs, and nested interval graphs
Authors: Skrien Dale J.
Published: May 2007

Given a set F of digraphs, we say a graph G is a F‐graph (resp., F*‐graph) if it has an orientation (resp., acyclic orientation) that has no induced subdigraphs isomorphic to any of the digraphs in F. It is proved that all the classes of graphs mentioned in the title are F‐graphs or F*‐graphs for subsets F of a set of three digraphs.
Uncontractable 4‐connected graphs
Authors: Martinov Nicola
Published: May 2007

The only uncontractable 4‐connected graphs are C2n for n ≥ 5 and the line graphs of the cubic cyclically 4‐connected graphs.
A review of random graphs
Authors: Karoński Michał
Published: May 2007

This paper presents a review of results dealing with structural properties and numerical characteristics of random edge‐subgraphs of complete graphs, with the connectedness of random graphs, as well as with random trees and forests.
Nonorientable genus of cartesian products of regular graphs
Authors: Pisanski Tomaž
Published: May 2007

A special type of surgery developed by A. T. White and later used by the author to construct orientable quadrilateral embeddings of Cartesian products of graphs is here expanded to cover the nonorientable case as well. This enables the nonorientable genus of many families of Cartesian products of triangle‐free graphs to be computed.
Topological subgraphs of cubic graphs and a theorem of dirac
Authors: Statman Richard
Published: May 2007

The topological subgraph relation between cubic graphs is analyzed. The analysis is then applied to generalize a theorem of Dirac.
On the decomposition of kn into complete bipartite graphs
Authors: Tverberg H.
Published: May 2007

A short proof is given of the impossibility of decomposing the complete graph on n vertices into n‐2 or fewer complete bipartite graphs.
Ramsey theory and Ramsey theoreticians
Authors: Spencer Joel
Published: May 2007

An anecdotal account of some of the events and people that have helped shape Ramsey Theory.
Generalizations of a Ramsey‐theoretic result of chvátal
Authors: Burr Stefan A. , Erdös Paul
Published: May 2007

Chvátal has shown that if T is a tree on n points then r(Kk, T) = (k – 1) (n – 1) + 1, where r is the (generalized) Ramsey number. It is shown that the same result holds when T is replaced by many other graphs. Such a T is called k‐good. The results proved all support the conjecture that any large graph that is sufficiently sparse, in the appropriate sense, is k‐good.
On the Ramsey number of trees versus graphs with large clique number
Authors: Gould Ronald J. , Jacobson Michael S.
Published: May 2007

Chvátal established that r(Tm, Kn) = (m – 1)(n – 1) + 1, where Tm is an arbitrary tree of order m and Kn is the complete graph of order n. This result was extended by Chartrand, Gould, and Polimeni who showed Kn could be replaced by a graph with clique number n and order n + 1 provided n ≧ 3 and m ≧ 3. We further extend these results to show that Kn can be replaced by any graph on n + 2 vertices with clique number n, provided n ≧ 5 and m ≧ 4. We then show that further extensions, in particular to graphs on n + 3 vertices with clique number n are impossible. We also investigate the Ramsey number of trees versus complete graphs minus sets of independent edges. We show that r(Tm, Kn –tK2) = (m – 1)(n – t – 1) + 1 for m ≧ 3, n ≧ 6, where Tm is any tree of order m except the star, and for each t, O ≦ t ≦ [(n – 2)/2].
On a Ramsey‐type problem
Authors: Chung F. R. K.
Published: May 2007

Suppose a graph G has the property that if one colors the edges of G in r colors, there always exists a monochromatic triangle. Is it true that if one colors the edges of G in r + 1 colors so that every vertex is incident to at most r colors then there must be a monochromatic triangle? This problem, which was first raised by P. Erdös, is answered in the negative here.
Graphs with unique Ramsey colorings
Authors: Grossman Jerrold W.
Published: May 2007

A pair of graphs (H1, H2) is a cleaver if there is a graph G with a unique factorization G = G2 ⊕ G2 such that Gi does not contain a copy of Hi. (In case H1 = H2, H1 is a cleaver if the factorization is unique up to interchange of factors.) A variety of positive and negative results on the existence of cleavers is obtained. For example (tree, complete graph) is a cleaver, and the triangle is the cleaver of an infinite collection of minimal graphs. On the other hand, stars are not cleavers.
On a conjecture of erdöus, simonovits, and sós concerning anti‐Ramsey theorems
Authors: Alon Noga
Published: May 2007

For n ≧ k ≧ 3, let f(n,Ck) denote the maximum number m for which it is possible to color the edges of the complete graph Kn with m colors in such a way that each k‐cycle Ck in Kn has atleast two edges of the same color. Erdös, Simonovits, and Sós conjectured that for every fixed k ≧ 3, f(n, Ck) = n (k–2/2 + 1/k–1) + O(1), and proved it only for k = 3. It is shown that f(n, C4) = n + [1/3n] – 1, and the conjecture thus proved for k = 4. Some upper bounds are also obtained for f(n, Ck), k ≧ 5.
Euclidean Ramsey theorems on the n‐sphere
Authors: Graham H. L.
Published: May 2007

Let us call a finite subset X of a Euclidean m‐space Em Ramsey if for any positive integer r there is an integer n = n(X;r) such that in any partition of En into r classes C1,…, Cr, some Ci contains a set X' which is the image of X under some Euclidean motion in En. Numerous results dealing with Ramsey sets have been proved in recent years although the basic problem of characterizing the Ramsey sets remains unsettled. The strongest constraints currently known are: (i) Any Ramsey set must lie on the surface of some sphere; (ii) Any subset of the set of vertices of a rectangular parallelepiped is Ramsey. In this paper we examine the corresponding problem in the case that our underlying spaces are (unit) n‐spheres Sn and the allowed motions are orthogonal transformations of Sn onto itself. In particular, we show that for subsets of Sn which are not too “large,” results similar to (i) and (ii) hold.
On size Ramsey number of paths, trees, and circuits. I
Authors: Beck JóZsef
Published: May 2007

The size Ramsey number ř(G) of a graph G is the smallest integer ř such that there is a graph F of ř edges with the property that any two‐coloring of the edges of F yields a monochromatic copy of G. First we show that the size Ramsey number ř(Pn) of the path Pn of length n is linear in n, solving a problem of Erdös. Second we present a general upper bound on size Ramsey numbers of trees.
On a Quasi‐Ramsey problem
Authors: Erdös Paul , Pach János
Published: May 2007

It is proved that if a graph G has atleast cn log n vertices, then either G or its complement G contains a subgraph H with atleast n vertices and minimum degree atleast | V(H)|/2. This result is not far from being best possible, as is shown by a rather unusual random construction. Some related questions are also discussed.
The rise and fall of the critical graph conjecture
Authors: Chetwynd Amanda G. , Wilson Robin J.
Published: May 2007

In this expository paper we discuss the critical graph conjecture and its eventual disproof by M.K. Goldberg and others.
Graph decomposition with constraints on the connectivity and minimum degree
Authors: Thomassen Carsten
Published: May 2007

For each pair s,t of natural numbers there exist natural numbers f(s,t) and g(s,t) such that the vertex set of each graph of connectivity at least f(s,t) (respectively minimum degree at least g(s,t)) has a decomposition into sets which induce subgraphs of connectivity (respectively minimum degree) at least s and t, respectively.
Series‐parallel graphs: A logical approach
Authors: McKee T. A.
Published: May 2007

The notions “series‐parallel” and “nonseparable” are shown to be logical converses of each other when formulated in a particular dual‐like fashion. Self‐dual circuit/cutset characterizations are given of series‐parallel and of series‐parallel nonseparable graphs.
Enumeration of acyclic and unicyclic nets with four types of self‐duality
Authors: Holroyd Fred
Published: May 2007

A net is a graph in which each point and line is given a sign. The point, line, and simple duals of a net are obtained by reversing the signs of the points, lines, or both. If a net possesses two of the three types of self‐duality, it possesses all three and is said to be doubly self‐dual. Enumeration formulas are derived for nets and point, line, simply, and doubly self‐dual nets, whose underlying graphs are acyclic and unicyclic. The numbers are tabulated up to 12 points (24 for doubly self‐dual nets) in each case.
Isomorphic factorizations of complete equipartite graphs
Authors: Quinn S. J.
Published: May 2007

A complete equipartite graph is a complete multipartite graph such that the color classes are equinumerous. An isomorphic factorization of a graph is a partition of the line set into disjoint isomorphic parts. It is shown that an isomorphic factorization of the complete equipartite graph into t isomorphic subgraphs exists whenever the total number of lines is divisible by t.
Local connectivity of a random graph
Authors: Erdös P. , Palmer E. M. , Robinson R. W.
Published: May 2007

A graph is locally connected if for each vertex ν of degree ≧2, the subgraph induced by the vertices adjacent to ν is connected. In this paper we establish a sharp threshold function for local connectivity. Specifically, if the probability of an edge of a labeled graph of order n is p = ((3/2 +ϵn) log n/n)1/2 where ϵn = (log log n + log(3/8) + 2x)/(2 log n), then the limiting probability that a random graph is locally connected is exp(‐exp(‐x)).
Hamiltonian path graphs
Authors: Chartrand Gary , Kapoor S. F. , Nordhaus E. A.
Published: May 2007

The Hamiltonian path graph H(G) of a graph G is that graph having the same vertex set as G and in which two vertices u and v are adjacent if and only if G contains a Hamiltonian u‐v path. A characterization of Hamiltonian graphs isomorphic to their Hamiltonian path graphs is presented.
On Hamiltonian‐connected regular graphs
Authors: Tomescu Ioan
Published: May 2007

In this paper it is shown that any m‐regular graph of order 2m (m ≧ 3), not isomorphic to Km,m, or of order 2m + 1 (m even, m ≧ 4), is Hamiltonian connected, which extends a previous result of Nash‐Williams. As a corollary, it is derived that any such graph contains atleast m Hamiltonian cycles for odd m and atleast 1/2m Hamiltonian cycles for even m.
When the cartesian product of two directed cycles is hypo‐Hamiltonian
Authors: Penn Laurence E. , Witte David
Published: May 2007

We show that the Cartesian product Za × Zb of two directed cycles is hypo‐Hamiltonian (Hamiltonian) if and only if there is a pair of relatively prime positive integers m and n with ma + nb = ab ‐ 1 (ma + nb = ab). The result for hypo‐Hamiltonian is new; that for Hamiltonian is known. These are special cases of the fact that there is a simple circuit of length p in Za × Zb if and only if there is a pair of relatively prime non‐negative integers m and n with ma + nb = p ≤ ab.
The uniqueness of the strongly regular graph on 77 points
Authors: Brouwer A. E.
Published: May 2007

We show the uniqueness of the strongly regular graph with parameters ν = 77, k = 16, λ = O, μ = 4 embedding it in the Higman‐Sims graph as a second subconstituent, and indicate the existence of a sporadic geometry.
On the existence of specified cycles in a tournament
Authors: Benhocine Abdelhamid , Wojda A. Pawel
Published: May 2007

For 2 ≦ p ≦n and n ≧ 3, D(n, p) denotes the digraph with n vertices obtained from a directed cycle of length n by changing the orientation of p‐ 1 consecutives edges. In this paper, we prove that every tournament of order n ≧ 7 contains D(n, p) for p = 2, 3, …, n. Furthermore, we determine the tournaments of order n, 3 ≦ n ≦ 6, which do not contain D(n, p) for some p.
Infinite median graphs, (0, 2)‐graphs, and hypercubes
Authors: Bandelt Hans‐J. , Mulder Henry Martyn
Published: May 2007

Hypercubes are characterized among connected bipartite graphs by interval conditions in several ways. These results are based on the following two facts: (i) connected bipartite graphs are median provided that all their intervals induce median graphs, and (ii) median (0, 2)‐graphs are hypercubes. No cardinality restrictions are made.
On proulx's four exceptional toroidal groups
Authors: Tucker Thomas W.
Published: May 2007

V. K. Proulx has proved that every finite group having a Cayley graph embeddable in the torus is, with four unresolved exceptions, a quotient of a Euclidean space group. It was conjectured that these four unresolved groups are not exceptional, that they in fact are Euclidean space‐group quotients. It is shown here that one is not exceptional, but the other three are.
Rotation numbers for unions of circuits
Authors: Bollobás Béla , Cockayne E. J. , Yao Fang Zu
Published: May 2007

Let G be a simple undirected graph which has p vertices and is rooted at x. Informally, the rotation number h(G, x) of this rooted graph is the minimum number of edges in a p‐vertex graph F, such that for each vertex v of F, there exists a copy of G in F with the root x at v. In this paper, we calculate a lower bound for the rotation number of the graph which is the disjoint union of circuits Ck, Ce where 4 ⩽ k < ⩽, give infinite classes where this bound is exact, and obtain classes of rotation numbers for the case k = 4.
J. Howard Redfield 1879–1944
Authors: Lloyd E. Keith
Published: May 2007

During much of his life J. Howard Redfield earned his living as an engineer but his main interests lay elsewhere. He performed and wrote music and was a gifted linguist, familiar with almost all European languages, as well as with some African and Asian tongues. In middle age he turned his attention towards combinatorial mathematics but it was not until many years after his death that the mathematical world realized that he had obtained significant results.
Redfield's lost paper in a modern context
Authors: Hall J. I. , Palmer E. M. , Robinson R. W.
Published: May 2007

An alternative proof of the main results of the preceding paper by J. Howard Redfield is provided in modern terminology. The relationship of Redfield's results with a number of more recent articles is discussed. This is necessitated by the delay of over forty years between the submission and publication of his lost paper.
Regular planar graphs with faces of only two types and shortness parameters
Authors: Owens P. J.
Published: May 2007

We construct a small non‐Hamiltonian 3‐connected trivalent planar graph whose faces are all 4‐gons or 7‐gons and show that the shortness coefficient of the class of such graphs is less than one. Then, by transforming non‐Hamiltonian trivalent graphs into regular graphs of valency four or five, we obtain our main results, as follows. We show first that the class of 3‐connected r‐valent planar graphs whose faces are of only two types, triangles and q‐gons, contains non‐Hamiltonian members and has a shortness exponent less than one when r = 4, for all q ≧ 12. Under the extra restriction that, among graphs of connectivity three, only those with maximum cyclic edge‐connectivity are to be considered, we prove the same result also when r = 4, for q = 20, and when r = 5, for all q ≧ 14 except multiples of three.
Tutte's 5‐flow conjecture for the projective plane
Authors: Steinberg Richard
Published: May 2007

Heawood proved that every planar graph with no 1‐cycles is vertex 5‐colorable, which is equivalent to the statement that every planar graph with no 1‐bonds has a nowhere‐zero 5‐flow. Tutte has conjectured that every graph with no 1‐bonds has a nowhere‐zero 5‐flow. We show that Tutte's 5‐Flow Conjecture is true for all graphs embeddable in the real projective plane.
One‐factorizations of the complete graph—A survey
Authors: Mendelsohn Eric , Rosa Alexander
Published: May 2007

We survey known results on the existence and enumeration of many kinds of 1‐factorizations of the complete graph. We also mention briefly some related questions and topics, as well as applications.
Toughness and the existence of k‐factors
Authors: Enomoto Hikoe , Jackson Bill , Katerinis P. , Saito Akira
Published: May 2007

A connected graph G is called t‐tough if t · w(G ‐ S) ⩽ |S| for any subset S of V(G) with w(G ‐ S) > 1, where w(G ‐ S) is the number of connected components of G ‐ S. We prove that every k‐tough graph has a k‐factor if k|G| is even and |G| ⩾ k + 1. This result, first conjectured by Chvátal, is sharp in the following sense: For any positive integer k and for any positive real number ε, there exists a (k ‐ ε)‐tough graph G with k|G| even and |G| ⩾ k + 1 which has no k‐factor.
Orthogonal one‐factorization graphs
Authors: Dinitz Jeffrey H.
Published: May 2007

An orthogonal one‐factorization graph (OOFG) is a graph in which the vertices are one‐factorizations of some underlying graph H, and two vertices are adjacent if and only if the one‐factorizations are orthogonal. An arbitrary finite graph, G, is realizable if there is an OOFG isomorphic to G. We show that every finite graph is realizable as an OOFG with underlying graph Kn for some n. We also discuss some special cases.
On the size of graphs with complete‐factors
Authors: Akiyama Jin , Frankl Peter
Published: May 2007

A spanning subgraph H of a graph G is called a Kl‐factor if each component of H is isomorphic to the complete graph of order l. We determine the minimum size for any graph to have a Kl‐factor. Relating this result, we give a new short proof of the Erdös‐Gallai theorem on the maximum size of graphs with at most β independent edges.
Chromaticity of two‐trees
Authors: Whitehead Earl Glen
Published: May 2007

The graphs called 2‐trees are defined by recursion. The smallest 2‐tree is the complete graph on 2 vertices. A 2‐tree on n + 1 vertices (where n ≥ 2) is obtained by adding a new vertex adjacent to each of 2 arbitrarily selected adjacent vertices in a 2‐tree on n vertices. A graph G is a 2‐tree on n(≥2) vertices if and only if its chromatic polynomial is equal to γ(γ ‐ 1)(γ ‐ 2)n—2.
Edge‐disjoint spanning trees: A connectedness theorem
Authors: Farber M. , Richter B. , Shank H.
Published: May 2007

It is well known that any spanning tree of a graph can be obtained from any other by a sequence of single edge exchanges in a way that preserves, at each step, the property of being a spanning tree. We consider a variation of this problem concerning pairs of edge‐disjoint spanning trees. In particular, it is shown that any pair of edge‐disjoint spanning trees can be obtained from any other by a sequence of single edge exchanges in a way that preserves, at each step, the property of being edge‐disjoint spanning trees.
On some minimal graphs of the torus
Authors: Bodendiek R. , Wagner K.
Published: May 2007

Let Γ be the set of finite, simple and nondirected graphs being not embeddable into the torus. Furthermore let >4 be a partial order‐relation and M4 (Γ) the minimal basis of Γ. In this paper we determine three graphs of M4 (Γ) being embeddable into the projective plane and containing the subgraph W.
On Stockmeyer's non‐reconstructible tournaments
Authors: Kocay William L.
Published: May 2007

Stockmeyer (The falsity of the reconstruction conjecture for tournaments. J. Graph Theory, 1 (1977) 19–25) constructed an infinite family of non‐reconstructible tournaments. It has been known for some time that there is a flaw in the proof given there. We provide an alternative constructive proof which is much simpler than the original proof.
An upper bound for the ramsey number r(K5 − e)
Authors: Harborth H. , Mengersen I.
Published: May 2007

An upper bound of 23 is proved for the Ramsey number r(K5 − e).
Bichromaticity of bipartite graphs
Authors: Pritikin Dan
Published: May 2007

Let B be a bipartite graph with edge set E and vertex bipartition M, N. The bichromaticity β(B) is defined as the maximum number β such that a complete bipartite graph on β vertices is obtainable from B by a sequence of identifications of vertices of M or vertices of N. Let μ = max{∣M∣, ∣N∣}. Harary, Hsu, and Miller proved that β(B) ≥ μ + 1 and that β(T) = μ + 1 for T an arbitrary tree. We prove that β(B) ≤ μ + ∣E∣/μ yielding a simpler proof that β(T) = μ + 1. We also characterize graphs for which Kμ, 2 is obtainable by such identifications. For QK. the graph of the K‐dimensional cube, we obtain the inequality 2K−1 + 2 ≤ β(QK) ≤ 2K−1 + K, the upper bound attainable iff K is a power of 2.
Existence of spanning and dominating trails and circuits
Authors: Veldman H. J.
Published: May 2007

Let T be a trail of a graph G. T is a spanning trail (S‐trail) if T contains all vertices of G. T is a dominating trail (D‐trail) if every edge of G is incident with at least one vertex of T. A circuit is a nontrivial closed trail. Sufficient conditions involving lower bounds on the degree‐sum of vertices or edges are derived for graphs to have an S‐trail, S‐circuit, D‐trail, or D‐circuit. Thereby a result of Brualdi and Shanny and one mentioned by Lesniak‐Foster and Williamson are improved.
A separation property of planar triangulations
Authors: Diestel Reinhard
Published: May 2007

Every planar triangulation G has the property that each induced cycle C of length at least 4 in G separates G, but no proper subgraph of C does. This property is trivially shared by all chordal graphs since these contain no such cycles at all. We ask to what extent maximally planar graphs and chordal graphs are unique with this property — or how much larger the class of graphs is that it determines. The answer is given in the form of a characterization of this class in terms of the simplicial decompositions of its elements. The theory of simplicial decompositions appears to be a very interesting, but still largely unexploited, method of characterization in graph theory, which seems tailor‐made for problems like the one discussed.
Contractibility and NP‐completeness
Authors: Brouwer A. E. , Veldman H. J.
Published: May 2007

For a fixed graph H, let H‐CON denote the problem of determining whether a given graph is contractible to H. The complexity of H‐CON is studied for H belonging to certain classes of graphs, together covering all connected graphs of order at most 4. In particular, H‐CON is NP‐complete if H is a connected triangle‐free graph other than a star. For each connected graph H of order at most 4 other than P4 and C4, H‐CON is solvable in polynomial time.
On generalized graph colorings
Authors: Brown Jason I. , Corneil Derek G.
Published: May 2007

Given a property P, graph G, and k ⩾ 0, a P k‐coloring is a function π: V(G) → {1, …, k} such that the subgraph induced by each color class has property P; χ(G : P) is the least k, for which G has a P k‐coloring. We investigate here the theory of P colorings. Generalizations of the wellknown notions of vertex criticality and unique colorability are discussed, and we extend a theorem of Erdös to P chromatic graphs.
Minimum path decompositions of oriented cubic graphs
Authors: Reid K. B. , Wayland Keith
Published: May 2007

Pullman [3] conjectured that if k is an odd positive integer, then every orientation of a regular graph of degree k has a minimum decomposition which contains no vertex which is both the initial vertex of some path in the decomposition and the terminal vertex of some other path in the decomposition. In this paper, the conjecture is established for cubic graphs, and its connection with Kelly's conjecture for tournaments is described.
Extreme degrees in random graphs
Authors: Palka Zbigniew
Published: May 2007

Let G* be a simple undirected graph on n labeled vertices. A general approach to the investigation of the probability distribution of extreme degrees in a random subgraph of G* is given. As an example of the application of the method, we consider the case when G* is a complete bipartite graph.
Time‐lagged effects of spring Tibetan Plateau soil moisture on the monsoon over China in early summer
Authors: Chow K. C. , Chan Johnny C. L. , Shi Xueli , Liu Yiming , Ding Yihui
Published: May 2007

The objective of the present study is to investigate the effect of initial soil moisture in the Tibetan Plateau (ISMTP) during the spring period on the local and regional climate in subsequent months. Numerical experiments with different ISMTP are made from 1 April to 30 June for the year 1998 using a regional climate model. This was a wet year with anomalously high summer precipitation over China. The same experiments have also been done for the year 1995, which was a normal year with respect to the summer rainfall over China. In both years, the snow amount over the Tibetan Plateau (TP) was higher than normal in the preceding winter/spring. The results of the experiments indicated that an increase in the ISMTP may lead to decreases in the air temperature, vertical velocity, and surface heating over the TP in June. In addition to the local effects, an increase in the ISMTP may also lead to modifications of the climate in some remote regions in early summer, such as an increase in the amount of monsoon precipitation over the mid to lower reaches of the Yangtze River region in eastern China and a decrease over the south China region. These precipitation differences due to the changes in ISMTP are consistent with those due to anomalous snow cover over the TP in winter or spring. Physically, the Tibetan High is weakened with an increase in ISMTP, which leads to a change in the strength of the Asian summer monsoon. Copyright © 2007 Royal Meteorological Society
Time variations of the effects of circulation variability modes on European temperature and precipitation in winter
Authors: Beranová Romana , Huth Radan
Published: May 2007

Five modes of variability are identified in winter monthly mean 500 hPa heights over the Euro‐Atlantic sector by rotated principal component analysis. Time variations of the effects of the modes on temperature and precipitation at more than 100 European stations are examined for period 1958–1998. Time variations are investigated by running correlations with the 15‐year window. At most of the stations, the correlations with circulation patterns vary considerably in time, both for temperature and precipitation. The spatial structure of the variations is assessed by cluster analysis of time variations of correlations. The groupings together with changes in the intensity and position of the circulation modes suggest possible mechanisms of the time variations in the circulation‐to‐climate effects. Copyright © 2007 Royal Meteorological Society
Evidence of plaggen soils in European North Russia (Arkhangelsk region)
Authors: Hubbe Alicja , Chertov Oleg , Kalinina Olga , Nadporozhskaya Marina , Tolksdorf‐Lienemann Eva , Giani Luise
Published: May 2007

To clarify whether a particular group of soils of Archangelsk region (European N Russia) with humus‐rich topsoils exceeding the plowing zone supports an anthropogenic formation, four exemplary profiles were investigated. The investigation sites are characterized by distinct elevated surfaces, and the soils show thick toplayers of up to 60 cm with enrichment of soil organic matter and artifacts like brick, charcoal, and peat fragments, all indicating an anthropogenic origin. Increased phytolith amounts and high P contents of up to 800 mg kg–1 citric acid–soluble P and up to 1,400 mg kg–1 total P in the top horizons support an anthropogenic influence. These properties are very similar to the Plagganthrepts of NW Europe. The same is true regarding the main management aims: increasing soil fertility and overcoming the need of bedding materials. Having the required depths of the anthropogenic topsoil, the properties of the soils of the Archangelsk region allow a classification as Agrozems (Russian classification), Plaggenesche (German classification), and Plagganthrepts (US taxonomy). Since the high base saturation of the topsoil excludes a designation as plaggic horizon, the topsoil has to be considered as terric horizon, which leads to a classification as Terric Anthrosol according to WRB.
Salinity‐induced changes in growth, superoxide dismutase activity, and ion content of two olive cultivars
Authors: Goreta Smiljana , Bučević‐Popović Viljemka , Pavela‐Vrančić Maja , Perica Slavko
Published: May 2007

Olive trees (Olea europaea L.) are considered moderately tolerant to salinity, with clear differences found among cultivars. One‐year‐old self‐rooted olive plants of the Croatian cv. Oblica and Italian cv. Leccino were grown for 90 d in nutrient solutions containing 0, 66, or 166 mM NaCl, respectively. The shoot length and the number of nodes and leaves for both cultivars were not affected by salinity up to 66 mM NaCl. However, at 166 mM NaCl, growth of Leccino was reduced earlier and to a higher extent than growth of Oblica. After 10 d of exposure to 66 and 166 mM NaCl, increased activity of superoxide dismutase (SOD) was observed in Leccino, whereas there was almost no response in Oblica. Reduced SOD activity in Leccino at 166 mM NaCl was observed after prolonged stress (90 d), whereas in Oblica SOD was increased at 66 mM compared to control or 166 mM NaCl. Electrolyte and K+ leakage were increased and relative water content decreased as NaCl concentration increased with similar intensity of response measured in both cultivars. Oblica exhibited an ability to keep a higher K+ : Na+ ratio at all salinity levels compared to Leccino, but since no difference was found in leaf K+ concentration, this was mainly achieved by less Na+ ions reaching the younger leaves. The antioxidative system represents a component of the complex olive salt‐tolerance mechanism, and it seems that the role of SOD in protection from oxidative stress depends on sodium accumulation in leaves.
Saltbush (Atriplex lampa) leaf protein concentrate by ultrafiltration for use in balanced animal feed formulations
Authors: Fernández Silvia S. , Menéndez Carlos , Mucciarelli Sara , Padilla Antonio P.
Published: May 2007

The purpose of this study was to evaluate the use of ultrafiltration and discontinuous diafiltration (DD) to obtain a protein concentrate from Atriplex lampa saltbush, improving its palatability by decreasing the salt content (mainly sodium and potassium chloride). The experimental work was done using a Pellicon® cassette (25 units) system equipped with polyethersulfone organic membranes with a molecular weight cut‐off value of 10 kD. The characteristic of the membranes and the feed material, the parameters and operational conditions were studied in the pretreatment of the sample as well as in the ultrafiltration process to obtain a maximum performance. The product obtained contained 85% protein on aa dry weight basis and a marked decrease in salt content, from 40% in fresh leaves to 2.5% after processing by DD, which is in agreement with the average conductivity values observed, from 18.1 mS cm−1 in the initial aqueous alkaline extract to a final value of 3.5 mS cm−1. Measurements of normalized water permeability were determined after each wash cycle in order to verify the flow recovery through the membrane. Analysis of amino acids from the protein concentrate with a chemical score of 85.13 was calculated using a Food Agricultural Organization reference pattern (sulfur amino acids as limiting amino acids). Nitrogen retention was evaluated by means of a biological test and the following values were obtained: net protein utilization = 63.00 ± 4.00, true digestibility = 79.00 ± 5.21, and biological value = 79.80. The presence of oxalic acid, nitrates, saponins, phenolic compounds and condensate tannins is not significant. The results indicate that the concentrate obtained has a high content of lysine, making these products particularly useful as a complement for cereal flour, which is deficient in this amino acid. The determined values suggest that the product can be used in balanced animal feed formulation. Copyright © 2007 Society of Chemical Industry
Gas chromatography coupled to mass spectrometry for analyses of organic compounds and biomarkers as tracers for geological, environmental, and forensic research
Authors: Medeiros Patricia M. , Simoneit Bernd R. T.
Published: May 2007

Gas chromatography, especially when coupled with mass spectrometry, is the analytical method of choice for elucidation of biomarker compounds present in organic mixtures extracted from geological, environmental, and biological samples. This review describes the biomarker concept,i. e., the precursor natural products to the geological/environmental derivatives, and their application as multi‐tracers in the geosphere and ambient environment. The mass spectrometric methods currently utilized for such analyses are reviewed with a general key to the literature, and typical examples of applications using GC–MS are also described.
Bridged Silsesquioxanes with Organic Domains Self‐Assembled as Functionalized Molecular Channels
Authors: Romeo Hernán E. , Fanovich María A. , Williams Roberto J. J. , Matějka Libor , Pleštil Josef , Brus Jiří
Published: May 2007

A bridged silsesquioxane was obtained from a precursor synthesized by the reaction of glycidoxypropyl(trimethoxysilane) (2 mol) with cyclohexylamine (1 mol). The polycondensation in the presence of formic acid produced a hybrid material exhibiting a short‐range order based on elongated organic channels accommodating the pendant cyclohexyl fragments, bounded by inorganic domains. The presence of functional groups in the organic channels (tertiary amine, ether, hydroxyl), can be used to retain small organic molecules capable of forming hydrogen bonds. Aspirin was used as a probe to illustrate this possibility.

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THE JUDGEMENT CALCULUS FOR INTUITIONISTIC LINEAR LOGIC: PROOF THEORY AND SEMANTICS
Authors: Valentini Silvio
Published: May 2007

In this paper we propose a new set of rules for a judgement calculus, i.e. a typed lambda calculus, based on Intuitionistic Linear Logic; these rules ease the problem of defining a suitable mathematical semantics. A proof of the canonical form theorem for this new system is given: it assures, beside the consistency of the calculus, the termination of the evaluation process of every well‐typed element. The definition of the mathematical semantics and a completeness theorem, that turns out to be a representation theorem, follow. This semantics is the basis to obtain a semantics for the evaluation process of every well‐typed program. 1991 MSC: 03B20, 03B40.
CUT ELIMINATION FOR PROPOSITIONAL DYNAMIC LOGIC WITHOUT
Authors: Bull Robert A.
Published: May 2007

The aim of this paper is to extend the semantic analysis of tense logic in Rescher/Urquhart [3] to propositional dynamic logic without*. For this we develop a nested sequential calculus whose axioms and rules directly reflect the steps in the semantic analysis. It is shown that this calculus, with the cut rule omitted, is complete with respect to the standard semantics. It follows that cut elimination does hold for this nested sequential calculus. MSC: 03B45.
RECONSTRUCTION OF BINARY RELATIONS FROM THEIR RESTRICTIONS OF CARDINALITY 2, 3, 4 and (n ‐ 1) II
Authors: Lopez Gérard , Rauzy Claire
Published: May 2007

We shall prove here that any binary relation on a base E with cardinality n > 6 is reconstructible from its restrictions of cardinality 2, 3, 4 and (n ‐ 1). This proof needs results of part I of this paper where we characterize any pair of relations R, R' which are 2‐, 3‐ and 4‐hypomorphic. As a corollary we obtain that any binary relation is (n ‐ 4)‐reconstructible (when n > 9).
A BRIEF SURVEY OF FRAMES FOR THE LAMBEK CALCULUS
Authors: Došen Kosta
Published: May 2007

Models for the Lambek calculus of syntactic categories surveyed here are based on frames that are in principle of the same type as Kripke frames for intuitionistic logic. These models are extracted from the literature on models for relevant logics, in particular the ternary relationed models introduced in the early seventies. The purpose of this brief survey is to locate some open completeness problems for variants of the Lambek calculus in the context of completeness results based on various types of ternary relational models.
BOOLEAN ALGEBRAS IN AST
Authors: Schumacher Klaus
Published: May 2007

In this paper we investigate Boolean algebras and their subalgebras in Alternative Set Theory (AST). We show that any two countable atomless Boolean algebras are isomorphic and we give an example of such a Boolean algebra. One other main result is, that there is an infinite Boolean algebra freely generated by a set. At the end of the paper we show that the sentence “There is no non‐trivial free group which is a set” is consistent with AST.
Non‐standard Analysis in WKL0
Authors: Tanaka Kazuyuki
Published: May 2007

Within a weak subsystem of second‐order arithmetic WKL0, we develop basic part of non‐standard analysis up to the Peano existence theorem.
Forcing in Finite Structures
Authors: Zambella Domenico
Published: May 2007

We present a simple and completely model‐theoretical proof of a strengthening of a theorem of Ajtai: The independence of the pigeonhole principle fromIΔ0(R). With regard to strength, the theorem proved here corresponds to the complexity/proof‐theoretical results of [10] and [14], but a different combinatorics is used. Techniques inspired by Razborov [11] replace those derived from Håstad [8]. This leads to a much shorter and very direct construction.
Transformation and reduction formulae for double q‐Clausen hypergeometric series
Authors: Chu Wenchang , Jia Cangzhi
Published: May 2007

By means of the Sears transformations, we establish eight general transformation theorems on bivariate basic hypergeometric series. Several transformation, reduction and summation formulae on the double q‐Clausen hypergeometric series are derived as consequences. Copyright © 2007 John Wiley & Sons, Ltd.
Shock formation in a chemotaxis model
Authors: Wang Zhian , Hillen Thomas
Published: May 2007

In this paper, we establish the existence of shock solutions for a simplified version of the Othmer–Stevens chemotaxis model (SIAM J. Appl. Math. 1997; 57:1044–1081). The existence of these shock solutions was suggested by Levine and Sleeman (SIAM J. Appl. Math. 1997; 57:683–730). Here, we consider the general Riemann problem and derive the shock curves in parameterized forms. By studying the travelling wave solutions, we examine the shock structure for the chemotaxis model and prove that the travelling wave speed is identical to the shock speed. Moreover, we explicitly derive an entropy–entropy flux pair to prove the uniqueness of the weak shock solutions. Some discussion is given for further study. Copyright © 2007 John Wiley & Sons, Ltd.
Berry anthocyanins as novel antioxidants in human health and disease prevention
Authors: Zafra‐Stone Shirley , Yasmin Taharat , Bagchi Manashi , Chatterjee Archana , Vinson Joe A. , Bagchi Debasis
Published: May 2007

Edible berries, a potential source of natural anthocyanin antioxidants, have demonstrated a broad spectrum of biomedical functions. These include cardiovascular disorders, advancing age‐induced oxidative stress, inflammatory responses, and diverse degenerative diseases. Berry anthocyanins also improve neuronal and cognitive brain functions, ocular health as well as protect genomic DNA integrity. This chapter demonstrates the beneficial effects of wild blueberry, bilberry, cranberry, elderberry, raspberry seeds, and strawberry in human health and disease prevention. Furthermore, this chapter will discuss the pharmacological benefits of a novel combination of selected berry extracts known as OptiBerry, a combination of wild blueberry, wild bilberry, cranberry, elderberry, raspberry seeds, and strawberry, and its potential benefit over individual berries. Recent studies in our laboratories have demonstrated that OptiBerry exhibits high antioxidant efficacy as shown by its high oxygen radical absorbance capacity (ORAC) values, novel antiangiogenic and antiatherosclerotic activities, and potential cytotoxicity towardsHelicobacter pylori, a noxious pathogen responsible for various gastrointestinal disorders including duodenal ulcer and gastric cancer, as compared to individual berry extracts. OptiBerry also significantly inhibited basal MCP‐1 and inducible NF‐κβ transcriptions as well as the inflammatory biomarker IL‐8, and significantly reduced the ability to form hemangioma and markedly decreased EOMA cell‐induced tumor growth in anin vivomodel. Overall, berry anthocyanins trigger genetic signaling in promoting human health and disease prevention.
SiGe BiCMOS subharmonic Gilbert mixer using lumped‐element rat‐race couplers
Authors: Tseng S.‐C. , Meng C. C. , Huang G.‐W.
Published: May 2007

A single‐ended down‐conversion subharmonic mixer is implemented using 0.35‐μm SiGe BiCMOS technology. Two lumped‐element rat‐race couplers are applied to generate differential LO and RF signals. This single‐ended rat‐race mixer has the conversion gain of 25 dB, −90‐dB 2×LO‐to‐RF isolation and −78‐dB 2×LO‐to‐IF isolation at the RF frequency of 10 GHz. The input return loss is about −10 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2018–2020, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22563
Design of diffractive elements at millimeter wavelengths using subwavelength cylindrical microstructures
Authors: Mirotznik Mark S. , Creazzo Timothy , Mathews Scott
Published: May 2007

We describe a design methodology for synthesizing diffractive elements based on two‐dimensional subwavelength cylindrical microstructures. We combine a numerical and experimental approach to demonstrate that by varying the diameter, pitch, and depth of subwavelength cylindrical occlusions in a homogenous substrate it is possible to produce multiphase diffractive elements. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1880–1884, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22571
A robust parameter extraction method for HBT small‐signal equivalent circuit
Authors: Ho Sung‐Jin , Choi Min Ki , van der Weide Daniel W.
Published: May 2007

An improved pad‐deembedding technique for InGaP/GaAs HBT reducing uncertainty in measurement and equivalent circuit is proposed. Intrinsic elements are obtained by iteratively determining the external and internal base resistance. The extracted equivalent circuits demonstrate good agreement with the measured S‐parameters obtained from 45 MHz to 40 GHz for different sizes of HBTs. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1845–1848, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22573
Novel suspended‐line microstrip coupler using BCB as supporting layer
Authors: Corona‐Chavez A. , Llamas‐Garro I. , Kim Jung‐Mu , Kim Yong‐Kweon
Published: May 2007

In this letter a novel λ/4 micromachined directional coupler is presented with a 10 μm benzocyclobutene (BCB) layer used to suspend one transmission line over another one in order to achieve a 3‐dB coupling. The coupler is centered at a frequency of 24 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1813–1814, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22574
Novel ultrawideband and multiband triangular planar inverted F antenna for wireless applications
Authors: Nashaat Dalia M.
Published: May 2007

A novel multi‐ and ultrawideband operation of a single feed triangular antenna are presented. For multi and UWB operation, the proposed design are achieved by inserting U shaped slot on the triangular PIFA with unequal arms, choosing between multi and ultrawide band by adjusting feeding position. Five resonant band of multi band operation is obtained in S‐band, Q‐band, bluetooth band, and WLAN band with acceptable impedance bandwidth. There is an increase in the number of resonant operating frequencies by etching U slot on the shorting feed plate. Ultrawideband is achieved by adjusting coaxial feed to obtained impedance bandwidth 27%. Enhancement impedance bandwidth by using folded shorting plate to improving bandwidth to achieve ultrawide bandwidth around 53%. The proposed antennas have acceptable gain around 11.5 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2039–2043, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22576
The multigrid preconditioned flexible GMRES solver for hierarchical TVFEM analysis
Authors: Zhu J. , Tang Wanchun
Published: May 2007

The H1(curl) conforming finite element method is applied for the finite‐element modeling of electromagnetic structures. A p‐version multigrid method combined with flexible GMRES solver is introduced to solve the finite element system. In this scheme, the p‐version multigrid is applied as the preconditioner and the flexible GMRES solver is performed as outer iteration. Therefore, the proposed technique can efficiently eliminate the low frequency components of the error of the numerical solution and can achieve fast convergence. Numerical simulation demonstrates the superior numerical convergence of the proposed method. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2012–2018, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22577