bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of chitosan molecular weight and deacetylation degree on hemostasis
Authors: Yang Jian , Tian Feng , Wang Zheng , Wang Qing , Zeng Yan‐Jun , Chen Shi‐Qian
Published: May 2007

Comparative studies have been carried out among solid‐state chitosan soliquoid, chitosan acetic acid physiological saline solution, and carboxymethyl chitosan physiological saline solution to discover the hemostatic effect of molecular weight (Mw) and deacetylation degree (DA) of chitosan. It was found that solid‐state chitosan and chitosan acetic acid physiological saline solution performed different hemostatic mechanisms. When blood mixed with chitosan acetic acid physiological saline solution, the erythrocytes aggregated and were deformed. The DA, especially a low DA, in the chitosan acetic acid physiological saline solution, had a significant effect on the unusual aggregation and deformation of erythrocytes, compared with the effect of Mw within a range between 105 and 106. However, this phenomenon could not be observed in solid‐state chitosan soliquoid. Solid‐state chitosan with a low DA absorbed more platelets and was more hemostatic. Carboxymethyl chitosan physiological saline solution had nothing to do with the aggregation and deformation of erythrocytes but caused local rouleau. The values of thrombin time (TT), prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration (FIB) were measured after the blood was mixed with solid‐state chitosan soliquoid, chitosan acetic acid physiological saline solution, and carboxymethyl chitosan physiological saline solution, separately. The results demonstrated that coagulation factors might not be activated by them. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
No effect of bone morphogenetic protein‐7 (OP‐1) on the incorporation of impacted bone grafts in a realistic acetabular model
Authors: Buma Pieter , Arts J. J. Chris , Gardeniers Jean W. M. , Verdonschot Nico , Schreurs B. Willem
Published: May 2007

Bone morphogenetic proteins (BMPs) accelerate bone repair in experimental and clinical conditions. Impacted Morsellized Cancellous Bone grafts (MCB) are successfully used to reconstruct bone defects after failed hip implants. The main question in this study was if BMP‐7 (OP‐1) mixed with MCB could accelerate the incorporation of MCB and prevents the formation of a soft tissue interface after remodeling of the MCB. A large loaded defect in the acetabulum of goats was reconstructed with a wire mesh and with MCB or MCB mixed with OP‐1. After 6 weeks, no differences were found in the revascularization process, in the number of osteoclasts resorbing the MCB, and in the thickness and appearance of the fibrous interface between MCB with or without OP‐1. After 6 weeks, enchondral bone had formed in the bone graft layer and on the periosteal anterior and superior rim in the OP‐1 group only. More periosteal bone and more bone in the holes of the mesh had been formed in most OP‐1 goats. Most MCB was replaced by new lamellar bone after 15 weeks in both groups. We speculate that during or directly after impaction most of the OP‐1 is released from the carrier inducing an early effect outside the reconstructive layer at the periosteal side of the acetabulum. Probably most OP‐1 has left the reconstruction by the time new vessels and progenitors reached the bone graft. These results do not support the use of OP‐1 in impaction bone grafting in patients. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Radiation‐induced bystander effects in malignant trophoblast cells are independent from gap junctional communication
Authors: Banaz‐Yaşar Ferya , Lennartz Klaus , Winterhager Elke , Gellhaus Alexandra
Published: May 2007

It is controversially discussed that irradiation induces bystander effects via gap junction channels and/or diffusible cellular factors such as nitric oxide or cytokines excreted from the cells into the environment. But up to now the molecular mechanism leading to a bystander response is not well understood. To discriminate between both mechanisms of bystander response, (i) mediated by gap junctional communication and/or (ii) mediated by diffusible molecules, we used non‐communicating Jeg3 malignant trophoblast cells transfected with inducible gap junction proteins, connexin43 and connexin26, respectively, based on the Tet‐On system. We co‐cultivated X‐ray irradiated and non‐irradiated bystander Jeg3 cells for 4 h, separated both cell populations by flow cytometry and evaluated the expression of activated p53 by Western blot analysis. The experimental design was proven with communicating versus non‐communicating Jeg3 cells. Interestingly, our results revealed a bystander effect which was independent from gap junctional communication properties and the connexin isoform expressed. Therefore, it seems more likely that the bystander effect is not mediated via gap junction channels but rather by paracrine mechanisms via excreted molecules in Jeg3 cells. J. Cell. Biochem. 103: 149–161, 2008. © 2007 Wiley‐Liss, Inc.
Central role of interferon regulatory factor‐1 (IRF‐1) in controlling retinoic acid inducible gene‐I (RIG‐I) expression
Authors: Su Zao‐Zhong , Sarkar Devanand , Emdad Luni , Barral Paola M. , Fisher Paul B.
Published: May 2007

Retinoic acid inducible gene‐I (RIG‐I) functions as the first line of defense against viral infection by sensing dsRNA and inducing type I interferon (IFN) production. The expression of RIG‐I itself is induced by IFN‐α/β and dsRNA. To comprehend the molecular mechanism of expression regulation, we cloned the RIG‐I promoter and analyzed its activity upon IFN‐β and dsRNA treatment. Under basal condition, RIG‐I mRNA level and promoter activity were significantly higher in normal cells versus their tumor counterparts. In both normal and cancer cells, RIG‐I expression was induced by IFN‐β and dsRNA. A single IRF‐1 binding site in the proximal promoter functioned as a crucial regulator of basal, IFN‐β‐ and dsRNA‐mediated induction of the RIG‐I promoter. IFN‐β and dsRNA treatment increased IRF‐1 binding to the RIG‐I promoter. IRF‐1 expression was also higher in normal cells than in cancer cells and it was induced by IFN‐β with similar kinetics as RIG‐I. These results confirm that by controlling RIG‐I expression, IRF‐1 plays an essential role in anti‐viral immunity. IRF‐1 is a tumor suppressor and the expression profile of RIG‐I together with its regulation by IRF‐1 and the presence of a caspase‐recruitment domain in RIG‐I suggest that RIG‐I might also possess tumor suppressor properties. J. Cell. Physiol. 213: 502–510, 2007. © 2007 Wiley‐Liss, Inc.
Paths extendable to cycles
Authors: Parsons T. D.
Published: May 2007

Let k be a positive integer, and S a nonempty set of positive integers. Suppose that G is a connected graph containing a path of length k, and that each path P of length k in G is contained in some cycle C(P) of length s ∈ S. We prove that every path of length less than k can be extended to a path of length k in G. This result answers conjectures of Entringer and Reid regarding when certain paths may be extended to cycles.
On the number of cycles of length k in a maximal planar graph
Authors: Hakimi S. L. , Schmeichel E. F.
Published: May 2007

Let G be a maximal planar graph with p vertices, and let Ck(G) denote the number of cycles of length k in G. We first present tight bounds for C3(G) and C4(G) in terms of p. We then give bounds for Ck(G) when 5 ≤ k ≤ p, and consider in particular bounds for Cp(G), in terms of p. Some conjectures and unsolved problems are stated.
A Note on Sub‐Eulerian Graphs
Authors: Jaeger F.
Published: May 2007

We present an algebraic proof of the following result: a set of edges of a multigraph G is contained in some cycle of G iff the set contains no odd cocycle of G (“cycle” means here: edge disjoint sum of elementary cycles). As a corollary we obtain the characterization of sub‐Eulerian graphs given by Boesch et al. [The spanning subgraphs of Eulerian grpahs. J. Graph Theory (1) (1977) 79–84].
Forests of label‐increasing trees
Authors: Riordan John
Published: May 2007

Label‐increasing trees are fully labeled rooted trees with the restriction that the labels are in increasing order on every path from the root; the best known example is the binary case—no tree with more than two branches at the root, or internal vertices of degree greater than three—extensively examined by Foata and Schutzenberger in A Survey of Combinatorial Theory. The forests without branching restrictions are enumerated by number of trees by Fn(x) = x(x + 1)…(x + n − 1), n >1 (F0(x) = 1), whose equivalent: Fn(x) = Yn(xT1,…, xTn), Fn(1)= Tn + 1 = n!, is readily adapted to branching restriction.
On some subclasses of well‐covered graphs
Authors: Staples Jo Ann W.
Published: May 2007

A set of points in a graph is independent if no two points in the set are adjacent. A graph is well covered if every maximal independent set is a maximum independent set or, equivalently, if every independent set is contained in a maximum independent set. The well‐covered graphs are classified by the Wn property: For a positive integer n, a graph G belongs to class Wn if ≥ n and any n disjoint independent sets are contained in n disjoint maximum independent sets. Constructions are presented that show how to build infinite families of Wn graphs containing arbitrarily large independent sets. A characterization of Wn graphs in terms of well‐covered subgraphs is given, as well as bounds for the size of a maximum independent set and the minimum and maximum degrees of points in Wn graphs.
𝒢‐constructibility of planar graphs
Authors: Mynhardt C. M. , Broere I.
Published: May 2007

In this paper, the concept of the 𝒢‐constructibility of graphs is introduced and investigated with particular reference to planar graphs. It is conjectured that the planar graphs are minimally N‐constructible, where N is a finite set of graphs and an infinite set 𝒢 is obtained such that the planar graphs are also minimally 𝒢‐constructible. Finally, some properties of the set of all N‐constructible graphs are discussed and compared with the corresponding properties of planar graphs.
The genus of the 2‐amalgamations of graphs
Authors: Decker R. W. , Glover H. H. , Huneke J. P.
Published: May 2007

A graph G is called the 2‐amalgamation of subgraphs G1 and G2 if G = G1 ∪ G2 and G1 ∩ G2 = {x, y}, 2 distinct points. in this case we write G = G1∪{x, y} G2. in this paper we show that the orientable genus, γ(G), satisfies the inequalities γ(G1) + γ(G2) − 1 ≤ γ(G1 ∪{x, y} G2) ≤ γ(G1) + γ(G2) + 1 and that this is the best possible result, i. e., the resulting three values for γ(G1 ∪{x, y} G2) which are possible can actually be realized by appropriate choices for G1 and G2.
On the theory of the matching polynomial
Authors: Godsil C. D. , Gutman I.
Published: May 2007

In this paper we report on the properties of the matching polynomial α(G) of a graph G. We present a number of recursion formulas for α(G), from which it follows that many families of orthogonal polynomials arise as matching polynomials of suitable families of graphs. We consider the relation between the matching and characteristic polynomials of a graph. Finally, we consider results which provide information on the zeros of α(G).
Pseudosimilar vertices in a graph
Authors: Kimble Robert J. , Schwenk Allen J. , Stockmeyer Paul K.
Published: May 2007

Dissimilar vertices whose removal leaves isomorphic subgraphs are called pseudosimilar. We construct infinite families of graphs having identity automorphism group, yet every vertex is pseudosimilar to some other vertex. Potential impact on the Reconstruction Conjecture is considered. We also construct, for each n, graphs containing a subset of n vertices which are mutually pseudosimilar. the analogous problem for mutually pseudosimilar edges is introduced.
Counting the 10‐point graphs by partition
Authors: Read R. C. , Wormald N. C.
Published: May 2007

In this paper we discuss old and new theoretical methods for computing the number of graphs with a given partition. We also show how a judicious combination of these methods gives rise to a procedure that is sufficiently powerful to make possible the enumeration of all graphs on 10 points according to their partitions.
A graph which is edge transitive but not arc transitive
Authors: Holt D. F.
Published: May 2007

A graph having 27 vertices is described, whose automorphism group is transitive on vertices and undirected edges, but not on directed edges.
Every connected, locally connected graph is upper embeddable
Authors: Nebeský Ladislav
Published: May 2007

In this Note it is proved that every connected, locally connected graph is upper embeddable. Moreover, a lower bound for the maximum genus of the square of a connected graph is given.
On the existence of a specified cycle in digraphs with constraints on degrees
Authors: Benhocine Abdelhamid
Published: May 2007

We prove that Woodall's and Ghouila‐Houri's conditions on degrees which ensure that a digraph is Hamiltonian, also ensure that it contains the analog of a directed Hamiltonian cycle but with one edge pointing the wrong way; that is, it contains two vertices that are connected in the same direction by both an edge and a Hamiltonian path.
Isomorphic factorizations VII. Regular graphs and tournaments
Authors: Wormald N. C.
Published: May 2007

It is shown using enumeration results that for r > 2t, almost all labeled r‐regular graphs cannot be factorized into t ⩾ 2 isomorphic subgraphs. However, no examples of such nonfactorizable graphs are known which satisfy the obvious divisibility condition that the number of edges is divisible by t. Similar observations hold for regular tournaments (t ⩾ 2} and for r‐regular digraphs (r > t ⩾ 2).
On superperfect noncomparability graphs
Authors: Andreae Thomas
Published: May 2007

The class of superperfect graphs, which was previously studied by A. J. Hoffman, E. L. Johnson, and M. C. Golumbic, is a proper subclass of the class of perfect graphs; further, it properly contains the class of comparability graphs. In his book, Golumbic proves that, for split graphs, G is a comparability graph if and only if G is superperfect. Moreover, the fact that split graphs are exactly those graphs which are both triangulated and cotriangulated motivated Golumbic to ask if it is true or false that, for triangulated (or cotriangulated) graphs, G is a comparability graph if and only if G is superperfect. In the present paper, we determine those members of Gallai's list of minimal noncomparability graphs which are superperfect and, as a consequence, we find that the answer to the above question is “false” for triangulated and “true” for cotriangulated graphs.
On partitioning the edges of graphs into connected subgraphs
Authors: Jünger M. , Reinelt G. , Pulleyblank W. R.
Published: May 2007

For any positive integer s, an s‐partition of a graph G = (V, E) is a partition of E into E1 ∪ E2 ∪…︁ ∪ Ek, where ∣Ei∣ = s for 1 ≤ i ≤ k − 1 and 1 ≤ ∣Ek∣ ≤ s and each Ei induces a connected subgraph of G. We prove

If G is connected, then there exists a 2‐partition, but not necessarily a 3‐partition;

If G is 2‐edge connected, then there exists a 3‐partition, but not necessarily a 4‐partition;

If G is 3‐edge connected, then there exists a 4‐partition;

If G is 4‐edge connected, then there exists an s‐partition for all s.
Defective colorings of graphs in surfaces: Partitions into subgraphs of bounded valency
Authors: Cowen L. J. , Cowen R. H. , Woodall D. R.
Published: May 2007

We call a graph (m, k)‐colorable if its vertices can be colored with m colors in such a way that each vertex is adjacent to at most k vertices of the same color as itself. For the class of planar graphs, and the class of outerplanar graphs, we determine all pairs (m, k) such that every graph in the class is (m, k)‐colorable. We include an elementary proof (not assuming the truth of the four‐color theorem) that every planar graph is (4, 1)‐colorable. Finally, we prove that, for each compact surface S, there is an integer k = k(S) such that every graph in S can be (4, k)‐colored; we conjecture that 4 can be replaced by 3 in this statement.
A class of self‐complementary vertex‐transitive digraphs
Authors: Chia Gek‐Ling , Lim Chong‐Keang
Published: May 2007

We characterize the class of self‐complementary vertex‐transitive digraphs on a prime number p of vertices. Using this, we enumerate (i) self‐complementary strongly vertex‐transitive digraphs on p vertices, (ii) self‐complementary vertex‐transitive digraphs on p vertices, (iii) self‐complementary vertex‐transitive graphs on p vertices. Finally it is shown that every self‐complementary vertex‐transitive digraph on p vertices is either a tournament or a graph.
Some genuine graph models in anthropology
Authors: Hage Per , Harary Frank
Published: May 2007

After long implicit use, graph theory is beginning to assume its rightful place in anthropology. Current research on exchange in Oceanian societies (Melanesia, Micronesia, and Polynesia) demonstrates its value for the classification, quantification, simulation, and enumeration of structural forms.
A lower bound for r(5, 5)
Authors: Exoo Geoffrey
Published: May 2007

A K5‐free two‐coloring of the edges of K42 is described, establishing 43 as a lower bound for R(5, 5).
A degree condition for the circumference of a graph
Authors: Dean Nathaniel , Fraisse Pierre
Published: May 2007

We present a new condition on the degree sums of a graph that implies the existence of a long cycle. Let c(G) denote the length of a longest cycle in the graph G and let m be any positive integer. Suppose G is a 2‐connected graph with vertices x1,…,xn and edge set E that satisfies the property that, for any two integers j and k with j < k, xjxk ∉ E, d(xi) ⩽ j and d(xk) ⩽ K ‐ 1, we have (1) d(xi) + d(xk ⩾ m if j + k ⩾ n and (2) if j + k < n, either m ⩾ n or d(xj) + d(xk) ⩾ min(K + 1,m). Then c(G) ⩾ min(m, n). This result unifies previous results of J.C. Bermond and M. Las Vergnas, respectively.
Tight bounds on the chromatic sum of a connected graph
Authors: Thomassen Carsten , Erdös Paul , Alavi Yousef , Malde Paresh J. , Schwenk Allen J.
Published: May 2007

The chromatic sum of a graph is introduced in the dissertation of Ewa Kubicka. It is the smallest possible total among all proper colorings of G using natural numbers. In this article we determine tight bounds on the chromatic sum of a connected graph with e edges.
Alternating cycles in edge‐colored graphs
Authors: Whitehead Carol
Published: May 2007

We show that the edges of a 2‐connected graph can be partitioned into two color classes so that every vertex is incident with edges of each color and every alternating cycle passes through a single edge. We also show that the edges of a simple graph with minimum vertex degree δ ≫ 2 can be partitioned into three color classes so that every vertex is incident with edges in exactly two colors and no cycle is alternating.
Double cycle covers and the petersen graph
Authors: Catlin Paul A.
Published: May 2007

Let O(G) denote the set of odd‐degree vertices of a graph G. Let t ϵ N and let 𝒮t denote the family of graphs G whose edge set has a partition.

E(g) = E1 U E2 U … U Etsuch that O(G) = O(G[Ei]) (1 ⩽ i ⩽ t). This partition is associated with a double cycle cover of G. We show that if a graph G is at most 5 edges short of being 4‐edge‐connected, then exactly one of these holds: G ϵ 𝒮3, G has at least one cut‐edge, or G is contractible to the Petersen graph. We also improve a sufficient condition of Jaeger for G ϵ 𝒮2p+1(p ϵ N).
On critically connected digraphs
Authors: Mader W.
Published: May 2007

A digraph is called critically connected if it is connected, but the deletion of any vertex destroys the connectivity. We prove that every critically connected finite digraph has at least two vertices of outdegree one. As an application, we show that for n ≧ 2, there is no n‐connected, non‐complete, finite digraph such that the deletion of any n vertices results in a disconnected digraph.
Automorphism groups of pictures
Authors: Behrendt Gerhard
Published: May 2007

A picture is a simple graph together with an edge‐coloring, such that each vertex is incident with exactly one edge of each color. An automorphism of a picture is a graph automorphism that preserves the colors of the edges. We show that every group is isomorphic to the full automorphism group of a picture, and prove that a group is isomorphic to a vertex‐transitive subgroup of the automorphism group of a picture if and only if it can be generated by involutions.
3‐edge‐connected embeddings have few singular edges
Authors: Bender Edward A. , Richmond L. Bruce
Published: May 2007

We show that a 3‐edge‐connected graph embedded in a surface of Euler characteristic χ has at most 3 – 3χ singular edges, except in the projective plane, where it has at most one singular edge, and the sphere, where it has none. This bound is best possible for all surfaces.
Generalized exponents of primitive directed graphs
Authors: Brualdi Richard A. , Liu Bolian
Published: May 2007

The exponent of a primitive digraph is the smallest integer t such that for each ordered pair of (not necessarily distinct) vertices x and y there is a path of length t from x to y. There is considerable information known about bounds on exponents and those numbers that can be exponents of primitive digraphs with n vertices. We introduce some new parameters related to the exponent and obtain bounds on these parameters.
Steiner centers in graphs
Authors: Oellermann Ortrud R. , Tian Songlin
Published: May 2007

The Steiner distance of a set S of vertices in a connected graph G is the minimum size among all connected subgraphs of G containing S. For n ≥ 2, the n‐eccentricity en(ν) of a vertex ν of a graph G is the maximum Steiner distance among all sets S of n vertices of G that contains ν. The n‐diameter of G is the maximum n‐eccentricity among the vertices of G while the n‐radius of G is the minimum n‐eccentricity. The n‐center of G is the subgraph induced by those vertices of G having minimum n‐eccentricity. It is shown that every graph is the n‐center of some graph. Several results on the n‐center of a tree are established. In particular, it is shown that the n‐center of a tree is a tree and those trees that are n‐centers of trees are characterized.
Bounds for rectilinear crossing numbers
Authors: Bienstock Daniel , Dean Nathaniel
Published: May 2007

A rectilinear drawing of a graph is one where each edge is drawn as a straight‐line segment, and the rectilinear crossing number of a graph is the minimum number of crossings over all rectilinear drawings. We describe, for every integer k ≥ 4, a class of graphs of crossing number k, but unbounded rectilinear crossing number. This is best possible since the rectilinear crossing number is equal to the crossing number whenever the latter is at most 3. Further, if we consider drawings where each edge is drawn as a polygonal line segment with at most one break point, then the resulting crossing number is at most quadratic in the regular crossing number. © 1993 John Wiley & Sons, Inc.
Rainbow coloring the cube
Authors: Faudree R. J. , Gyárfás A. , Lesniak L. , Schelp R. H.
Published: May 2007

We prove that for d ≥ 4, d ≠ 5, the edges of the d‐dimensional cube can be colored by d colors so that all quadrangles have four distinct colors. © 1993 John Wiley & Sons, Inc.
Regular fourfold coverings with respect to the identity automorphism
Authors: Hong Sungpyo , Kwak Jin Ho
Published: May 2007

The aim of this paper is to count the isomorphism classes of regular fourfold coverings of a graph with respect to the identity automorphism, as M. Hofmeister did for double coverings. © 1993 John Wiley & Sons, Inc.
Extremal graphs without three‐cycles or four‐cycles
Authors: Garnick David K. , Kwong Y. H. Harris , Lazebnik Felix
Published: May 2007

We derive bounds for f(v), the maximum number of edges in a graph on v vertices that contains neither three‐cycles nor four‐cycles. Also, we give the exact value of f(v) for all v up to 24 and constructive lower bounds for all v up to 200. © 1993 John Wiley & Sons, Inc.
Generalized fibonacci cubes are mostly hamiltonian
Authors: Liu Jenshiuh , Hsu Wen‐Jing , Chung Moon Jung
Published: May 2007

TheHamiltonian problemis to determine whether a graph contains a spanning (Hamiltonian) path or cycle. Here we study the Hamiltonian problem for thegeneralized Fibonacci cubes, which are a new family of graphs that have applications in interconnection topologies [J. Liuand W.‐J. Hsu, „Distributed Algorithms for Shortest‐Path, Deadlock‐Free Routing and Broadcasting in a Class of Interconnection Topologies,”︁ International Parallel Processing Symposium (1992)]. We show that each member of this family contains a Hamiltonian path. Furthermore, we also characterize the members of this family that contain a Hamiltonian cycle.
The irredundant ramsey number s(3, 7)
Authors: Chen Guantao , Rousseau Cecil C.
Published: May 2007

The irredundant Ramsey number s(m, n) is the smallest p such that for every graph G with p vertices, either G contains an n‐element irredundant set or its complement G contains an m‐element irredundant set. Cockayne, Hattingh, and Mynhardt have given a computer‐assisted proof that s(3, 7) = 18. The purpose of this paper is to give a self‐contained proof of this result. © 1995 John Wiley & Sons, Inc.
An isomorphic factorization of the complete graph
Authors: Hwang F. K.
Published: May 2007

We give necessary and sufficient conditions that the complete graph Krc has an isomorphic factorization into Kr × Kc. We show that this factorization has an application to clone library screening. © 1995 John Wiley & Sons, Inc.
The edge reconstruction number of a disconnected graph
Authors: Molina Robert
Published: May 2007

The edge reconstruction number of a graph G, RN(G), is the minimum number of edge deleted subgraphs required to determine G up to isomorphism. We prove the following results for a disconnected graph G with at least two nontrivial components. If G has a pair of nontrivial nonisomorphic components then RN(G) ≤ 3. If G has a pair of nontrivial nonisomorphic components, is not a forest, and contains a nontrivial component other than K3 or K1,3 then RN(G) ≤ 2. Finally, if all nontrivial components of G are isomorphic to a graph with k edges, then RN(G) ≤ k + 2. The edge reconstruction results in this paper are similar to the vertex reconstruction results stated by Myrvold (“The Ally‐Reconstruction Number of a Disconnected Graph,” Ars Combinatoria, Vol. 28 [1989] pp. 123‐127), but a significant difference is that the edge reconstruction number of a disconnected graph is often two, while the vertex reconstruction number of a graph is always three or more. © 1995 John Wiley & Sons, Inc.
A new proof of the 6 color theorem
Authors: Borodin Oleg V.
Published: May 2007

In 1965 Ringel raised a 6 color problem for graphs that can be stated in at least three different forms. In particular, is it possible to color the vertices and faces of every plane graph with 6 colors so that any two adjacent or incident elements are colored differently? This 6 color problem was solved in 1984 by the present author; the proof used about 35 reducible configurations. A shorter new proof is given here using only half as many of reducible configurations. © 1995 John Wiley & Sons, Inc.
Flexibility along the neck of the ostrich (Struthio camelus) and consequences for the reconstruction of dinosaurs with extreme neck length
Authors: Dzemski Gordon , Christian Andreas
Published: May 2007

The gross morphology and the flexibility along the neck of the ostrich (Struthio camelus) were examined using fresh tissue as well as neck skeletons. The results of the morphologic studies were compared with results from observations of living ostriches. The investigation was focused on differences in the morphology and the function between different sections of the neck. Additionally, the function of major dorsal neck ligaments was examined, including measurements of force‐strain‐relations. Comparative studies of giraffes (Giraffa camelopardalis) and camels (Camelus bactrianus) were conducted to find relations between the flexibility along the neck and the general feeding strategy. The examinations revealed that the neck of the ostrich can be divided into four sections with different functions. The first is the atlas‐axis‐complex which is responsible for torsion. The adjacent cranial section of the neck is flexible in dorsoventral and lateral directions but this part of the neck is usually kept straight at rest and during feeding. Dorsoventral flexibility is highest in the middle section of the neck, whereas the base of the neck is primarily used for lateral excursions of the neck. For giraffes and camels, the posture and utilization of the neck are also reflected in the flexibility of the neck. For all three species, it is possible to reconstruct the pattern of flexibility of the neck by using the neck skeletons alone. Therefore, it appears reasonable to reconstruct the neck utilization and the feeding strategies of dinosaurs with long necks by deriving the flexibility of the neck from preserved vertebrae. For Diplodocus carnegii the neck posture and the feeding strategy were reconstructed. Two neck regions, one around the 9th neck vertebra and the second at the base of the neck, indicate that Diplodocus, like the ostrich, adopted different neck postures. The neck was probably kept very low during feeding. During interruptions of the feeding, e.g., in an alert, the head could have been lifted in an economic way by raising the cranial section of the neck. During standing and locomotion the head was probably located well above the shoulders. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Validation of direct injection electrospray LC‐MS/MS for confirmation of opiates in urine drug testing
Authors: Gustavsson E. , Andersson M. , Stephanson N. , Beck O.
Published: May 2007

A method based on the direct injection of diluted urine for the identification and quantification of morphine, morphine‐3‐glucuronide, morphine‐6‐glucuronide, codeine, codeine‐6‐glucuronide, ethylmorphine, ethylmorphine‐6‐glucuronide and 6‐acetylmorphine (6AM) in human urine by electrospray ionisation liquid chromatography‐tandem mass spectrometry was validated for use as a confirmation procedure in urine drug testing. Four deuterium labelled analogues were used as internal standards: morphine‐3‐glucuronide‐D3, morphine‐D3, codeine‐D3 and 6AM‐D3. Twenty microlitre aliquots of urine were mixed with 80 μl of the internal standard solution in autosampler vials and 10 μl was injected. The chromatographic system consisted of a 2.0 × 100 mm C18 column and the gradient elution buffers used acetonitrile and 25 mmol/l formic acid. Two product ions produced from the protonated molecular ions were monitored in the selected reaction monitoring mode. The intra‐ and inter‐assay variability (coefficient of variation) was below 10% at higher levels for all analytes, but at the reporting limits the variation was above 20% for 6AM, morphine‐3‐glucuronide and codeine‐6‐glucuronide. Ion suppression occurred early after injection but did not affect the identification and quantification of the analytes in authentic samples. The method was further validated by comparison with a reference gas chromatographic‐mass spectrometric method using authentic urine samples. The two methods agreed almost completely (99%) regarding the identified analytes, but for the quantitative results there were slightly lower levels when measuring glucuronides directly as compared to total determination after hydrolysis by gas chromatography‐mass spectrometry.

We conclude that the presented liquid chromatographic‐tandem mass spectrometric method is robust and reliable, and suitable for use as a confirmation method in urine drug testing for opiates
Copyright © 2007 John Wiley & Sons, Ltd.
Electrospray ionization‐multistage tandem mass spectrometry of complex multitin organometallic compounds
Authors: Jirásko Robert , Holčapek Michal , Kolářová Lenka , Basu Baul Tushar S.
Published: May 2007

The series of 14 complex organotin(IV) compounds containing many tin atoms and noncovalent bonds in the structure was characterized by electrospray ionization multistage tandem mass spectrometry (ESI‐MSn). The mass spectra were measured in both polarity modes to obtain complementary structural information. The characteristic pattern of ten natural tin isotopes allowed the determination of the number of tin atoms in the molecular adducts and fragment ions by comparing theoretical and experimental isotopic distributions. Positive ion ESI spectra show unusual adduct formation depending on the type of organic solvent used for the direct infusion analysis owing to the ion–molecule reactions in the ion source. On the basis of the detailed spectral interpretation of organotin(IV) compounds, the fragmentation patterns of multitin organometallic compounds have been proposed. Noncovalent bonds in polymeric complexes are fragmented first, which is then followed by characteristic neutral losses in monomeric units. Copyright © 2007 John Wiley & Sons, Ltd.
Impairment of microglial responses to facial nerve axotomy in cathepsin S–deficient mice
Authors: Hao Hai Peng , Doh‐ura Katsumi , Nakanishi Hiroshi
Published: May 2007

Cathepsin S (CS) is a lysosomal/endosomal cysteine protease especially expressed in cells of a mononuclear lineage including microglia. To better understand the role of CS in microglia, we investigated microglial responses after a facial nerve axotomy in CS‐deficient (CS−/−) and wild‐type mice. Microglia in both groups accumulated in the facial motor nucleus following axotomy. However, the mean number of microglia in CS−/− mice on the axotomized side was significantly smaller than that in wild‐type mice. Microglia were found to adhere to injured motoneurons in wild‐type mice, whereas microglia abutted on injured motoneurons without spreading on their surface in CS−/− mice. At the same time, the axotomy‐induced down‐regulation of tenasin‐R, an antiadhesive perineuronal net for microglia, was partially abrogated in CS−/− mice. Primary cultured microglia prepared from CS−/− mice showed that CS deficiency caused significant suppression of migration and transmigration of microglia. In CS−/− mice, impaired recruitments of circulating monocytes and T lymphocytes and reduced expression of the class II major compatibility complex on the axotomized side were observed. Interestingly, cathepsin B, a typical lysosomal cysteine protease, was markedly expressed on the axotomized side in CS−/− but not in wild‐type microglia. Finally, we compared axotomy‐induced neuronal death in the two groups and found that the percentage of motoneurons that survived in CS−/− mice was significantly smaller than that in wild‐type mice. The present study strongly suggests that CS plays a role in the migration and activation of microglia to protect facial motoneurons against axotomy‐induced injury. © 2007 Wiley‐Liss, Inc.
Deviations in gait pattern in experimental models of hindlimb paresis shown by a novel pressure mapping system
Authors: Boyd Benjamin S. , Puttlitz Christian , Noble‐Haeusslein Linda J. , John Constance M. , Trivedi Alpa , Topp Kimberly S.
Published: May 2007

Injuries to the central and peripheral nervous system result in varying degrees of paresis and as such alter gait. We developed novel quantitative measures to assess compensatory patterns of gait in experimental models of unilateral and bilateral hindlimb paresis. We hypothesized that hindlimb paresis results in unique alterations in the gait cycle that reflect the symmetry of the initial lesion. To test this hypothesis, adult, male Sprague‐Dawley rats were subjected to a unilateral sciatic nerve crush injury or a moderately severe spinal cord contusion injury at T8. Kinematic and timing parameters were captured simultaneously in all four limbs and alterations in gait were then compared to relevant sham controls. Gait analysis consisted of walking trials through a gait tunnel positioned over a Tekscan pressure sensor grid. After sciatic nerve injury, animals unweighted the injured limb by shifting their center of mass toward the contralateral forelimb and hindlimb. These changes in weight‐bearing occurred simultaneously with an increase in stance time on the contralateral limbs. As might be expected spinal cord injured animals unweighted their hindlimbs, as shown by reduced hindlimb contact force and contact pressure. These adjustments coincided with a shortening of forelimb stance time and stride length. These findings show both alterations and compensatory changes in gait that reflect the symmetry of the initial injury. © 2007 Wiley‐Liss, Inc.
Three-Quarters of Right Liver Donors Experienced Postoperative Complications† ‡
Authors: Yi Nam-Joon , Suh Kyung-Suk , Cho Jai Young , Lee Hae Won , Cho Eung-Ho , Yang Sung Hoon , Cho Yong Beom , Lee Kuhn Uk
Published: May 2007

A donor right hepatectomy (RH) is associated with a higher rate of morbidity than a left hepatectomy. Therefore, the precise morbidity should be known to improve the success of donor RH implementation. However, the rate of complication varies according to the individual definition of morbidity. This study prospectively analyzed the outcomes of 83 consecutive living donor RHs between January 2002 and July 2004 using a standardized classification of the severity of complications. The morbidity was classified using the modified Clavien system: grade I for minor complications; grade II for potentially life-threatening complications requiring pharmacological treatment; grade III for complications requiring invasive intervention; grade IV for complications causing organ dysfunction requiring intensive care unit management; and grade V complications resulting in the death of the patient. The donors were followed-up regularly for at least 12 months. No donor death or relaparotomy was noted. Overall, 65 out of 83 donors (78.3%) experienced postoperative complications: grades I, II, III, IV, and V complications in 64 (77.1%), 11 (13.3%), 1 (1.2%), 0, and 0 patients, respectively. The most common grade I complications were hyperbilirubinemia (n = 31) and pleural effusion (n = 31), and bile leakage in grade II (n = 7). The bilirubin and alanine aminotransferase levels were normal in 92.7% of donors at the 1-year follow-up. In conclusion, although most of these adverse events were minor and self-limited, 78% of right liver donors still experienced morbidity. Therefore, continuous standardized reporting of the donor morbidity as well as meticulous surgery and intensive care are essential for the success of donor RH implementation. Liver Transpl 13:797–806, 2007. © 2006 AASLD.
Pharmacokinetics of Mycophenolic Acid in Liver Transplant Patients After Intravenous and Oral Administration of Mycophenolate Mofetil†
Authors: Jain Ashok , Venkataramanan Raman , Kwong Tai , Mohanka Ravi , Orloff Mark , Abt Peter , Kashyap Randeep , Tsoulfas Georgios , Mack Cindy , Williamson Mary , Batzold Pam , Bozorgzadeh Adel
Published: May 2007

The bioavailability of mycophenolic acid (MPA) after oral administration of mycophenolate mofetil (MMF) has been reported to be more than 90% in healthy volunteers, and in kidney and thoracic organ transplant patients. Such information is limited in liver transplant (LTx) patients. The present study compares the pharmacokinetics of MPA after intravenous (IV) and oral administrations of MMF in LTx recipients. Pharmacokinetic parameters were calculated using WinNonlin software. A total of 12 deceased donor LTx patients initially received IV MMF and were switched to oral MMF after 2-7 days (mean, 3.3 ± 1.7) when oral feeds were started. Multiple blood samples were drawn immediately prior to and after IV or oral MMF and the plasma concentration of MPA was measured. The mean peak plasma concentrations and the area under the plasma concentration vs. time curve (AUC) were significantly higher after IV MMF compared to oral MMF (peak plasma concentrations of 10.7 ± 2.1 μg/mL for IV vs. 4.5 ± 2.8 μg/mL for oral; P = 0.0001; and AUC of 28.9 ± 7.1 μg · hr/mL for IV vs. 12.8 ± 4.2 μg · hr/mL for oral; P = 0.0001). The oral bioavailability of MPA was 48.5 ± 18.7%. The systemic clearance, half-life, and steady state volume of distribution of MPA were 26.9 ± 6 L/hour, 5.5 hours, and 85 liters, respectively. The terminal disposition half-life was not significantly different between the 2 routes of administration. In conclusion, during the early postoperative period, LTx recipients have MPA exposure with oral MMF of less than half that of IV MMF. Use of IV MMF immediately post-LTx may provide an immunological advantage. Liver Transpl 13:791–796, 2007. © 2007 AASLD.
Posttransplantation Lymphoproliferative Disorder—the Great Mimic in Liver Transplantation
Authors: Koch David G. , Christiansen Lydia , Lazarchick John , Stuart Robert , Willner Ira R. , Reuben Adrian
Published: May 2007

Case series describing posttransplantation lymphoproliferative disorder (PTLD) after liver transplantation (LTx) have been limited in number because of the rarity of the disorder. The prevalence of Epstein-Barr virus (EBV) infection and its detection, the clinical and histological diversity of disease, and survival have varied. The aim of this study is to define the clinical and pathological spectrum of PTLD after LTx, and evaluate EBV prevalence, impact of infection, and patient survival. A retrospective analysis of all LTx recipients at our institution diagnosed with PTLD from January 1990 until May 2005, recording clinical presentations, times of presentation after transplantation, histological findings, results of EBV assessment, and survival, as well as the interrelationship of these variables. Among 621 LTx recipients were 22 cases of PTLD in 21 patients, of whom 5 were children and 16 were adults. Extranodal disease was present in 17 of 22 cases (77%) involving a wide variety of organ systems, while 5/22 (23%) had lymphadenopathy. The spectrum of PTLD histopathology was equally varied. In situ hybridization for EBV showed negativity in 8 of 13 (62%) and positivity in 5 of 13 (38%) cases tested. Neither time interval from transplantation to presentation (median 33 months) nor mortality (average 32%) was influenced by EBV status. In conclusion, PTLD in LTx recipients is predominantly extranodal and can involve a wide variety of organ systems, which may confound initial diagnosis. The lymphoproliferative histological spectrum is also diverse. Nowadays, PTLD is frequently EBV-negative, and EBV status does not appear to influence clinical or pathological presentation, or survival. Liver Transpl 13:904–912, 2007. © 2007 AASLD.
A New Priority Policy for Patients with Hepatocellular Carcinoma Awaiting Liver Transplantation Within the Model for End-Stage Liver Disease System
Authors: Piscaglia Fabio , Camaggi Valeria , Ravaioli Matteo , Grazi Gian Luca , Zanello Matteo , Leoni Simona , Ballardini Giorgio , Cavrini Giulia , Pinna Antonio Daniele , Bolondi Luigi
Published: May 2007

The best prioritization of patients with hepatocellular carcinoma (HCC) waiting for liver transplantation under the model for end-stage liver disease (MELD) allocation system is still being debated. We analyzed the impact of a MELD adjustment for HCC, which consisted of the addition of an extra score (based on the HCC stage and waiting time) to the native MELD score. The outcome was analyzed for 301 patients with chronic liver disease listed for liver transplantation between March 1, 2001 and February 28, 2003 [United Network for Organ Sharing (UNOS)-Child-Turcotte-Pugh (CTP) era, 163 patients, 28.8% with HCC] and between March 1, 2003 and February 28, 2004 (HCC-MELD era, 138 patients, 29.7% with HCC). In the HCC-MELD era, the cumulative dropout risk at 6 months was 17.6% for patients with HCC versus 22.3% for those patients without HCC (P = NS), similar to that in the UNOS-CTP era. The cumulative probability of transplantation at 6 months was 70.3% versus 39.0% (P = 0.005), being higher than that in the UNOS-CTP era for patients with HCC (P = 0.02). At the end of the HCC-MELD era, 12 patients with HCC (29.3%) versus 57 without HCC (58.8%) were still on the list (P = 0.001). Both native and adjusted MELD scores were higher (P < 0.05) and progressed more in patients with HCC who dropped out than in those who underwent transplantation or remained on the list (the initial-final native MELD scores were 17.3-23.1, 15.5-15.6, and 12.8-14.1, respectively). The patients without HCC remaining on the list showed stable MELD scores (initial-final: 15.1-15.4). In conclusion, the present data support the strategy of including the native MELD scores in the allocation system for HCC. This model allows the timely transplantation of patients with HCC without severely affecting the outcome of patients without HCC. Liver Transpl 13:857–866, 2007. © 2007 AASLD.
Psychological Strain in Urgent Indications for Living Donor Liver Transplantation
Authors: Erim Yesim , Beckmann Mingo , Kroencke Sylvia , Valentin-Gamazo Camino , Malago Massimo , Broering Dieter , Rogiers Xavier , Frilling Andrea , Broelsch Christoph E. , Schulz Karl-Heinz
Published: May 2007

The ethical soundness of living donor liver transplantation (LDLT) in urgent indications is still under discussion. The aim of the survey was to investigate the psychological distress of donors in cases of hepatocellular carcinoma (HCC) or acute liver failure (ALF). In a prospective multicenter study (n = 123), health-related quality of life (QOL), anxiety, and depression were measured. The psychological distress of donors was correlated to the degree of urgency of the recipients' indication, which was classified as nonurgent, HCC, or ALF. During the donor evaluation prior to LDLT, the donors with recipients for HCC and ALF demonstrated significantly reduced mental QOL in comparison to donors for a nonurgent indication and to the German normative sample. Compared to healthy controls, anxiety and depression were significantly increased in donors for ALF. Three months after the transplantation, scores for mental QOL as well as for anxiety and depression improved and were within the normal range for the whole group as well as for the ALF donors. In conclusion, the psychological burden was temporary in nature. Our findings can be considered as arguments for the current practice to address family members as donors in cases of HCC and ALF. Liver Transpl 13:886–895, 2007. © 2007 AASLD.
Thrombolysis for Early Hepatic Artery Thrombosis
Authors: Perkins James D.
Published: May 2007

Hepatic artery thrombosis is an uncommon complication of liver transplantation. However, it is a major indication for re-transplantation. The use of transcatheter thrombolysis and subsequent surgical revascularization as a graft salvage procedure is discussed. Four of 5 cases (80%) were successful in re-establishing flow and uncovering underlying arterial anatomic defects. None were treated definitively by endoluminal measures due to an inability to resolve the underlying anatomic defects. However, 2 of 5 cases (40%) went on to a successful surgical revascularization and represent successful long-term outcome of transcatheter thrombolysis followed by definitive surgical revascularization. We conclude that, definitive endoluminal success cannot be achieved without resolving associated, and possibly instigating, underlying arterial anatomical defects. However, reestablishing flow to the graft can unmask underlying lesions as well as assess surrounding vasculature thus providing anatomical information for a more elective, better planned and definitive surgical revision.