bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study on orientation and absorption spectrum of interfacial molecules by using continuum model
Authors: Ma Jian‐Yi , Wang Jing‐Bo , Li Xiang‐Yuan , Huang Yao , Zhu Quan , Fu Ke‐Xiang 
Published: June 2007

AbstractIn this work, a numerical procedure based on the continuum model is developed and applied to the solvation energy for ground state and the spectral shift against the position and the orientation of the interfacial molecule. The interface is described as a sharp boundary separating two bulk media. The polarizable continuum model (PCM) allows us to account for both electrostatic and nonelectrostatic solute–solvent interactions when we calculate the solvation energy. In this work we extend PCM to the interfacial system and the information about the position and orientation of the interfacial molecule can be obtained. Based on the developed expression of the electrostatic free energy of a nonequilibrium state, the numerical procedure has been implemented and used to deal with a series of test molecules. The time‐dependent density functional theory (TDDFT) associated with PCM is used for the electron structure and the spectroscopy calculations of the test molecules in homogeneous solvents. With the charge distribution of the ground and excited states, the position‐ and orientation‐dependencies of the solvation energy and the spectrum have been investigated for the interfacial systems, taking the electrostatic interaction, the cavitation energy, and the dispersion–repulsion interaction into account. The cavitation energy is paid particular attention, since the interface portion cut off by the occupation of the interfacial molecule contributes an extra part to the stabilization for the interfacial system. The embedding depth, the favorable orientational angle, and the spectral shift for the interfacial molecule have been investigated in detail. From the solvation energy calculations, an explanation has been given on why the interfacial molecule, even if symmetrical in structure, tends to take a tilting manner, rather than perpendicular to the interface. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Numerical computations of molecular reactions in associated systems caused by the formation of fractal structures
Authors: Tarasov D. N. , Tiger R. P. 
Published: June 2007

AbstractThe interaction between particles in a system containing fractal clusters has been computationally simulated. The fractal structure of the system has been demonstrated to determine the kinetic characteristics of particle interaction. If a system in an N‐dimensional space (N = 2, 3, 4) contains fractal clusters with the fractal dimension D > N‐1, the rate of interaction of a free particle with particles belonging to clusters depends on their concentration according to the power law. The exponent γ of this power law formally corresponds to the kinetic order of the reaction with respect to the concentration of particles belonging to the clusters. Its value is determined by the free surface of the clusters and depends on its fractal dimension D. The results of simulation qualitatively agree with the data on high, non‐integral orders of many liquid phase molecular reactions characterized by self‐organization of the medium via weak intermolecular interactions, such as hydrogen bonds. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
An approach to hedetniemi's conjecture
Authors: Sauer N. W. , Zhu X. 
Published: June 2007

AbstractFor a fixed integer n ϵ ω, a graph G of chromatic number greater than n is called persistent if for all n + 1‐chromatic graphs H, the products G × H are n + 1‐chromatic graphs. Wheter all graphs of chromatic number greater than n are persistent is a long‐standing open problem due to Hedetniemi. We call a graph G strongly persistent if G is persistent and the Hajos sum of G with any other persistent graph H is still persistent. This paper extends the class of known persistent graphs by proving the following results: If G is constructed from copies of Kn+1 by Hajos sums, adding vertices and edges and at most one contraction of nonadjacent vertices, then G is strongly persistent. © 1929 John Wiley & Sons, Inc.
A degree condition for spanning eulerian subgraphs
Authors: Chen Zhi‐Hong 
Published: June 2007

AbstractLet p ≥ 2 be a fixed integer. Let G be a simple and 2‐edge‐connected graph on n vertices, and let g be the girth of G. If d(u) + d(v) ≥ (2/(g − 2))((n/p) − 4 + g) holds whenever uv ∉ E(G), and if n is sufficiently large compared to p, then either G has a spanning eulerian subgraph or G can be contracted to a graph G1 of order at most p without a spanning eulerian subgraph. Furthermore, we characterize the graphs that satisfy the conditions above such that G1 has order p and does not have any spanning eulerian subgraph. © 1993 John Wiley & Sons, Inc.
On the edge‐toughness of a graph. II
Authors: Peng Y. H. , Tay T. S. 
Published: June 2007

AbstractThe edge‐toughness T1(G) of a graph G is defined as
equation image
where the minimum is taken over every edge‐cutset X that separates G into ω (G ‐ X) components. We determine this quantity for some special classes of graphs that also gives the arboricity of these graphs. We also give a simpler proof to the following result of Peng et al.: For any positive integers r, s satisfying r/2 < s ≤ r, there exists an infinite family of graphs such that for each graph G in the family, λ(G) = r (where λ(G) is the edge‐connectivity of G) T1(G) = s, and G can be factored into s spanning trees. © 1993 John Wiley & Sons, Inc.
N‐extendability of symmetric graphs
Authors: Aldred R. E. L. , Holton D. A. , Lou Dingjun 
Published: June 2007

AbstractIt is proved that a cyclically (k − 1)(2n − 1)‐edge‐connected edge transitive k‐regular graph with even order is n‐extendable, where k ≥ 3 and k − 1 ≥ n ≥ ⌈(k + 1)/2⌉. The bound of cyclic edge connectivity is sharp when k = 3. © 1993 John Wiley & Sons, Inc.
Disjoint circuits in the cartesian product of two directed cycles
Authors: Curran Stephen 
Published: June 2007

AbstractWe show that the Cartesian product of two directed cycles Za X Zb has r disjointly embedded circuits C1, C2, ⃛, Cr with specified knot classes knot(Ci) = (mi, ni), for i = 1, 2, ⃛, r, if and only if there exist relatively prime non‐negative integers m and n such that knot(Ci) = (m, n), for i = 1, 2, ⃛, r, and r(am + bn) ≦ ab. We generalize this result to the Cayley digraph on a finite abelian group with a two‐element generating set.
Toughness, minimum degree, and the existence of 2‐factors
Authors: Bauer D. , Schmeichel E. 
Published: June 2007

AbstractDegree conditions on the vertices of a t‐tough graph G(1 ≦ t ≦ 2) that ensure the existence of a 2‐factor in G are presented. These conditions are asymptotically best possible for every t ϵ [1, 3/2] and for infinitely many t ϵ [3/2, 2].
On linear vertex‐arboricity of complementary graphs
Authors: Alavi Yousef , Liu Jiuqiang , Wang Jianfang 
Published: June 2007

AbstractThe linear vertex‐arboricity ρ(G) of a graph G is defined to be the minimum number of subsets into which the vertex set of G can be partitioned such that each subset induces a linear forest. In this paper, we give the sharp upper and lower bounds for the sum and product of linear vertex‐arboricities of a graph and its complement. Specifically, we prove that for any graph G of order p.magnified image and for any graph G of order p = (2n + 1)2, where n ≅ Z+, 2n + 2 ≦ ρ(G) + ρ(G).
A note on minimum graphs with girth pair (4, 2l + 1)
Authors: Hanson Denis , Wang Ping , Macgillivray Gary 
Published: June 2007

AbstractWe show that the size of a smallest connected k‐regular graph with girth pair (4, 2l + 1) is within a constant of (2l + 1) k/2. In so doing we disprove a conjecture of Harary and Kovacs.
Maximum chromatic polynomials of 2‐connected graphs
Authors: Tomescu Ioan 
Published: June 2007

AbstractIn this paper we obtain chromatic polynomials P(G; λ) of 2‐connected graphs of order n that are maximum for positive integer‐valued arguments λ ≧ 3. The extremal graphs are cycles Cn and these graphs are unique for every λ ≧ 3 and n ≠ 5.We also determine max{P(G; λ): G is 2‐connected of order n and G ≠ Cn} and all extremal graphs relative to this property, with some consequences on the maximum number of 3‐colorings in the class of 2‐connected graphs of order n having X(G) = 2 and X(G) = 3, respectively. For every n ≧ 5 and λ ≧ 4, the first three maximum chromatic polynomials of 2‐connected graphs are determined.
Large k‐preserving sets in infinite graphs
Authors: Huck Andreas , Niedermeyer Frank , Shelah Saharon 
Published: June 2007

AbstractLet K be a cardinal. If K χ0, define K:= K. Otherwise, let K := K + 1. We prove a conjecture of Mader: Every infinite K‐connected graph G = (V, E) contains a set S ⊆ V with |S| = |V| such that G/S is K‐connected for all S⊆ S.
Uniqueness of maximal dominating cycles in 3‐regular graphs and of hamiltonian cycles in 4‐regular graphs
Authors: Fleischner Herbert 
Published: June 2007

AbstractWe construct 3‐regular (cubic) graphs G that have a dominating cycle C such that no other cycle C1 of G satisfies V(C) ⊆ V(C1). By a similar construction we obtain loopless 4‐regular graphs having precisely one hamiltonian cycle. The basis for these constructions are considerations on the uniqueness of a cycle decomposition compatible with a given eulerian trail in some eulerian graph.
Hamiltonian graphs with neighborhood intersections
Authors: Chen G. , Schelp R. H. 
Published: June 2007

AbstractIn this paper, k + 1 real numbers c1, c2, ⃛, ck+1 are found such that the following condition is sufficient for a k‐connected graph of order n to be hamiltonian: for each independent vertex set of k + 1 vertices in G.magnified image where Si = {v ≅ V:|N(v) ∩ S| = i} for 0 ≦ i ≦ k + 1. Such a set of k + 1 numbers is called an Hk‐sequence. A sufficient condition for the existence of Hk‐sequences is obtained that generalizes many known results involving sum of degrees, neighborhood unions, and/or neighborhood intersections.
A characterization of well‐covered graphs that contain neither 4‐ nor 5‐cycles
Authors: Finbow A. , Hartnell B. , Nowakowski R. J. 
Published: June 2007

AbstractA graph is well covered if every maximal independent set has the same cardinality. A vertex x, in a well‐covered graph G, is called extendable if G – {x} is well covered and β(G) = β(G – {x}). If G is a connected, well‐covered graph containing no 4‐ nor 5‐cycles as subgraphs and G contains an extendable vertex, then G is the disjoint union of edges and triangles together with a restricted set of edges joining extendable vertices. There are only 3 other connected, well‐covered graphs of this type that do not contain an extendable vertex. Moreover, all these graphs can be recognized in polynomial time.
Self‐dual embeddings of complete multipartite graphs
Authors: Archdeacon Dan 
Published: June 2007

AbstractIn this paper we examine self‐dual embeddings of complete multipartite graphs, focusing primarily on Km(n) having m parts each of size n. If m = 2, then n must be even. If the embedding is on an orientable surface, then an Euler characteristic argument shows that no such embedding exists when n is odd and m  2, 3 (mod 4); there is no such restriction for embeddings on nonorientable surfaces. We show that these embeddings exist with a few small exceptions. As a corollary, every group has a Cayley graph with a self‐dual embedding. Our main technique is an addition construction that combines self‐dual embeddings of two subgraphs into a self‐dual embedding of their union. We also apply this technique to nonregular multipartite graphs and to cubes.
Walks through every edge exactly twice
Authors: Richter R. Bruce 
Published: June 2007

AbstractIn this article, we develop a theory of walks traversing every edge exactly twice. Rosenstiehl and Read proved that if G is a graph with no set of edges that is simultaneously a cycle and a cocycle, then G is planar if and only if there is a closed walk W in G traversing every edge exactly twice such that certain sets of edges derived from W are all cocycles. One consequence of the current work is a simple proof of the Rosenstiehl‐Read theorem. Another is an unusual method for determining the rank (over the integers modulo 2) of a symmetric matrix obtained from a circle graph.
A chvátal–erdős type condition for hamiltonian graphs
Authors: Lu Xiaoyun 
Published: June 2007

AbstractFor a simple graph G of order n ≧ 3, define θ(G) = min{(d(A, A))/|A|; Ø ø A ≠ V}. We shall prove the following Chvátal–Erdős type condition: If α(G) ≦ θ(G)n, then G is Hamiltonian.
Representations of graphs modulo n
Authors: Evans Anthony B. , Fricke Gerd H. , Maneri Carl C. , McKee Terry A. , Perkel Manley 
Published: June 2007

AbstractA graph is representable modulo n if its vertices can be labeled with distinct integers between 0 and n, the difference of the labels of two vertices being relatively prime to n if and only if the vertices are adjacent. Erdős and Evans recently proved that every graph is representable modulo some positive integer. We derive a combinatorial formulation of representability modulo n and use it to characterize those graphs representable modulo certain types of integers, in particular integers with only two prime divisors. Other facets of representability are also explored. We obtain information about the values of n modulo which paths and cycles are representable.
On the existence of special depth first search trees
Authors: Korach Ephraim , Ostfeld Zvi 
Published: June 2007

AbstractThe Depth First Search (DFS) algorithm is one of the basic techniques that is used in a very large variety of graph algorithms. Most applications of the DFS involve the construction of a depth‐first spanning tree (DFS tree).In this paper, we give a complete characterization of all the graphs in which every spanning tree is a DFS tree. These graphs are called Total‐DFS‐Graphs. We prove that Total‐DFS‐Graphs are closed under minors. It follows by the work of Robertson and Seymour on graph minors that there is a finite set of forbidden minors of these graphs and that there is a polynomial algorithm for their recognition. We also provide explicit characterizations of these graphs in terms of forbidden minors and forbidden topological minors. The complete characterization implies explicit linear algorithm for their recognition. In some problems the degree of some vertices in the DFS tree obtained in a certain run are crucial and therefore we also consider the following problem: Let G = (V,E) be a connected undirected graph where |V| = n and let d ϵ Nn be a degree sequence upper bound vector. Is there any DFS tree T with degree sequence dT that violates d (i.e., dT ≤ d, which means: E j such that dT(j) > d(j))? We show that this problem is NP‐complete even for the case where we restrict the degree of only on specific vertex to be less than or equal to k for a fixed k ≥ 2 (i.e., d = (n ‐ 1, ⃛, n ‐ 1, k, n ‐ 1, ⃛, n ‐ 1)). 0 1995 John Wiley & Sons, Inc.
Quasi‐transitive digraphs
Authors: Bang‐Jensen Jørgen , Huang Jing 
Published: June 2007

AbstractA digraph is quasi‐transitive if there is a complete adjacency between the inset and the outset of each vertex. Quasi‐transitive digraphs are interseting because of their relation to comparability graphs. Specifically, a graph can be oriented as a quasi‐transitive digraph if and only if it is a comparability graph. Quasi‐transitive digraphs are also of interest as they share many nice properties of tournaments. Indeed, we show that every strongly connected quasi‐transitive digraphs D on at least four vertices has two vertices v1 and v2 such that D – vi is strongly connected for i = 1, 2. A result of tournaments on the existence of a pair of arc‐disjoint in‐ and out‐branchings rooted at the same vertex can also be extended to quasi‐transitive digraphs. However, some properties of tournaments, like hamiltonicity, cannot be extended directly to quasi‐transitive digraphs. Therefore we characterize those quasi‐transitive digraphs which have a hamiltonian cycle, respectively a hamiltonian path. We show the existence of highly connected quasi‐transitive digraphs D with a factor (a collection of disjoint cycles covering the vertex set of D), which have a cycle of every length 3 ≦ k ≦ |V(D)| − 1 through every vertex and yet they are not hamiltonian. Finally we characterize pancyclic and vertex pancyclic quasi‐transitive digraphs. © 1995, John Wiley & Sons, Inc.
Relative length of long paths and cycles in graphs with large degree sums
Authors: Enomoto Hikoe , van den Heuvel Jan , Kaneko Atsushi , Saito Akira 
Published: June 2007

AbstractFor a graph G, p(G) denotes the order of a longest path in G and c(G) the order of a longest cycle. We show that if G is a connected graph n ≥ 3 vertices such that d(u) + d(v) + d(w) ≧ n for all triples u, v, w of independent vertices, then G satisfies c(G) ≥ p(G) – 1, or G is in one of six families of exceptional graphs. This generalizes results of Bondy and of Bauer, Morgana, Schmeichel, and Veldman. © 1995, John Wiley & Sons, Inc.
2‐connected coverings of bounded degree in 3‐connected graphs
Authors: Gao Zhicheng 
Published: June 2007

AbstractIn a recent paper, Barnette showed that every 3‐connected planar graph has a 2‐connected spanning subgraph of maximum degree at most fifteen, he also constructed a planar triangulation that does not have 2‐connected spanning subgraphs of maximum degree five. In this paper, we show that every 3‐connected graph which is embeddable in the sphere, the projective plane, the torus or the Klein bottle has a 2‐connected spanning subgraph of maximum degree at most six. © 1995 John Wiley & Sons, Inc.
Cross‐leg tibial posterior perforator flap
Authors: Georgescu Alexandru V. , Irina Capota , Ileana Matei 
Published: June 2007

AbstractBackground: In the lower leg posttraumatic pathology, we are frequently confronted with tissue defects that are difficult to cover by local or distance means, because of either the poor tissue quality or the precarious local vessels. One of the still available methods for solving these cases remains the cross‐leg flap. The authors will try to demonstrate the advantages of this method, by using the cross‐leg flap based on perforator vessels. Methods: We are presenting two cases for which we practiced a cross‐leg perforator flap, based on perforator vessels emerging from the posterior tibial artery. Results: The results were favorable, demonstrated by immobilization in a comfortable position, perfect flap integration, pedicle flap's division at 14–21 days, early postsurgery ambulation. Conclusions: The cross‐leg perforator flap diminishes many of the disadvantages created by the classic cross‐leg flap and can be successfully used in cases in which other procedures are prohibited. © 2007 Wiley‐Liss, Inc. Microsurgery, 2007.
Embryology of neural tube defects: information provided by associated malformations
Authors: Cabaret A. S. , Loget P. , Loeuillet L. , Odent S. , Poulain P. 
Published: June 2007

AbstractObjectivesTo get information about embryologic mechanisms of neural tube defects (NTD), by studying the associated malformations.MethodsEighty three cases of NTD, seen at the prenatal diagnosis unit of Rennes University Hospital (France) between May 1999 and December 2002, were retrospectively studied. Cases with chromosomal anomalies (5/83), cases without available karyotype or pathologic examination were excluded. 24 spina bifida, and 27 cephalic forms (anencephalies, exencephalies, and encephaloceles) were thus analyzed.ResultsOnly 22/51 cases (43%) were strictly isolated NTD. Anomalies of tissues arising from neural crests were noted in 8/51 fetuses (16%), midline or lateralization anomalies in 12/51 (24%), and anomalies of mesoblastic tissues in 17/51 (33%). An already known syndrome was found in 4/51 cases (8%).ConclusionNDT are more extensive congenital damages that would suggest the restrictive terminology. That prompts to assess cautiously prenatal diagnosis of NTD, and to get detailed pathological examination after termination of pregnancy. Copyright © 2007 John Wiley & Sons, Ltd.
Cell‐free mRNA concentrations of CRH, PLAC1, and selectin‐P are increased in the plasma of pregnant women with preeclampsia
Authors: Purwosunu Yuditiya , Sekizawa Akihiko , Farina Antonio , Wibowo Noroyono , Okazaki Shiho , Nakamura Masamitsu , Samura Osamu , Fujito Naoya , Okai Takashi 
Published: June 2007

AbstractObjectiveTo compare mRNA concentrations of corticotrophin‐releasing hormone (CRH), placenta specific‐1 (PLAC1), and selectin‐P in preeclamptic and normal pregnancies.MethodsPeripheral blood samples were obtained from 43 pregnant women with preeclampsia and 41 control subjects. Plasma was harvested from samples and RNA extracted. Plasma RNA was analyzed using reverse transcription polymerase chain reaction (PCR) assay. Median concentrations of CRH, PLAC1, and selectin‐P mRNA in plasma were compared, to assess possible differences in distribution. Data were also stratified and compared according to clinical severity of preeclampsia. Finally, CRH, PLAC1, and selectin‐P were plotted against quantitative distributions of blood pressure and proteinuria.ResultsAll markers were differently distributed between cases and controls. Median values in subgroups correlated with severity of preeclampsia. All markers correlated with both. Selectin‐P was identified as the marker with the highest degree of correlation. No correlation was found between any markers in the control group and proteinuria or blood pressure.ConclusionCRH, PLAC1, and selectin‐P are distributed differently in preeclampsia cases compared to controls and correlate with signs of preeclampsia. Copyright © 2007 John Wiley & Sons, Ltd.
Crystal structure of the PIN domain of human telomerase‐associated protein EST1A
Authors: Takeshita Daijiro , Zenno Shuhei , Lee Woo Cheol , Saigo Kaoru , Tanokura Masaru 
Published: June 2007

AbstractSaccharomyces cerevisiae Est1p is a telomerase‐associated protein essential for telomere length homeostasis. hEST1A is one of the three human Est1p homologues and is considered to be involved not only in regulation of telomere elongation or capping but also in nonsense‐mediated degradation of RNA. hEST1A is composed of two conserved regions, Est1p homology and PIN (PilT N‐terminus) domains. The present study shows the crystal structure of the PIN domain at 1.8 Å resolution. The overall structure is composed of an α/β fold or a core structure similar to the counterpart of 5′ nucleases and an extended structure absent from archaeal PIN‐domain proteins and 5′ nucleases. The structural properties of the PIN domain indicate its putative active center consisting of invariant acidic amino acid residues, which is geometrically similar to the active center of 5′ nucleases and an archaeal PAE2754 PIN‐domain protein associated with exonuclease activity. Proteins 2007. © 2007 Wiley‐Liss, Inc.