bluuebunny/crossref_metadata_2025 huggingface dataset:
Stepfather Involvement and Adolescents’ Disposition Toward Having Sex
Authors: Menning Chadwick , Holtzman Mellisa , Kapinus Carolyn
Published: June 2007

CONTEXT:  Existing literature suggests that stepfather relationships may be associated with adolescents’ attitudes toward sex. Given the large number of children living with stepfathers, these associations call for the attention of researchers and intervention programs.

METHODS:  Attitudes toward sex among participants in the first wave (1994–1995) of the National Longitudinal Study of Adolescent Health (Add Health) who were living in households headed by biological mothers and stepfathers were analyzed using linear regression models. Parental involvement and maternal attitudes toward sex were included as predictors.

RESULTS:  The greater the involvement between adolescents and their stepfathers, the less positively disposed adolescents are toward having sex; however, the association holds only for males. Females’ dispositions toward sex are tied to their religiosity and their mothers’ attitudes toward sex. Both males and females who are sexually experienced view sex more positively than do those who have never had sex.

CONCLUSIONS:  Different factors influence males’ and females’ motivations to engage in sex, and intervention programs need to be structured with these differences in mind. Programs that work toward cultivating close relationships between stepfathers and stepchildren will likely be most effective for males, while programs that highlight the important role that mothers play in making clear their beliefs about the acceptability of teenagers’ sexual activity will likely be most effective for females.
Association Between Adolescent Pregnancy And a Family History of Teenage Births
Authors: East Patricia L. , Reyes Barbara T. , Horn Emily J.
Published: June 2007

CONTEXT:  The extent to which young women’s risk of adolescent pregnancy is associated with having a mother who was a teenage parent, a sister who was a teenage parent or both is not known.

METHODS:  A sample of 127 Latina and black adolescent females completed in‐depth surveys at three time points between 1994 and 2000. Logistic regression analyses were used to examine whether socioeconomic factors, mothers’ parenting characteristics and certain sibling relationship qualities explain the association between a family history of teenage births and young women’s risk of pregnancy.

RESULTS:  Compared with young women with no family history of teenage births, young women whose sister had had a teenage birth and those whose sister and mother both had had teenage births were significantly more likely to experience a teenage pregnancy (odds ratios, 4.8 and 5.1, respectively). Young women who had only a sister who had had a teenage birth had greater odds of pregnancy than young women who had only a mother who had had a teenage birth (4.5). Having both a mother and a sister who had had teenage births was independently associated with an elevated risk of pregnancy (3.7), even after controlling for socioeconomic and mothers’ parenting characteristics. Frequent companionship with an older sister was associated with increased odds of teenage pregnancy (4.5); frequent conflict with an older sister who had had a teenage birth was marginally associated with decreased odds of the outcome (0.3).

CONCLUSION:  Pregnancy prevention interventions targeting young women according to maternal and sibling teenage birth histories may be effective.
Removal and Quantification of Asian Tapeworm from Bonytail Chub Using Praziquantel
Authors: Ward David L
Published: June 2007

The spread of the Asian tapeworm Bothriocephalus acheilognathi has been identified as a potential threat to endangered cyprinid fishes, such as bonytail Gila elegans and humpback chub G. cypha. Praziquantel is often used to remove Asian tapeworms from these species, but little information is available on the effectiveness or side effects of these treatments. I performed laboratory experiments using bonytails (110–457 mm total length) to evaluate the dosage and time needed to effectively remove 100% of Asian tapeworms using praziquantel. A low dose of 0.7 mg/L for 24 h was not effective at removing all Asian tapeworms, whereas a 24-h exposure at 1.5 mg/L and higher was 100% effective. A bath treatment of 12-h duration only appears effective at the highest dose of 36 mg/L, but not all Asian tapeworms are cleared from the host within this time frame. No short-term mortality or side effects of praziquantel treatment were observed. Praziquantel bath treatments can effectively and safely remove 100% of Asian tapeworms from bonytail if dosage and treatment duration are adequate. In some cases, repeated treatments may be necessary to ensure that Asian tapeworms are not spread into new environments.
Estimation of burst rates in water distribution mains
Authors: Boxall J. B. , O'Hagan A. , Pooladsaz S. , Saul A. J. , Unwin D. M.
Published: June 2007

The ability to forecast the burst behaviour of pipes in water distribution systems is a fundamental requirement of proactive planning for investment, replacement and rehabilitation strategies. Burst behaviour is, however, a complex function of many uncertain contributing factors. Attempts to develop accurate predictive models have been limited by: data quality and quantity; the lack of associations between individual events and pipes; and the statistical techniques available and applied. Predictive expressions for annual burst rate in cast-iron and asbestos cement pipes are derived for two sample data sets from the UK. The available data were interrogated to make rigorous associations between individual events and pipes and filtered for missing, default and erroneous data. Using statistical analysis, the theory of generalised linear models, it was then possible to derive predictive expressions for burst probabilities. The resulting expressions show strong associations between annual burst rate, diameter and length and a complex association with age. Analysis was also undertaken to investigate associations with available soil data; a relative lack of consistent dependence of burst rate on these data is demonstrated.
Estimating time to failure of cast-iron water mains
Authors: Rajani B. , Tesfamariam S.
Published: June 2007

Water distribution networks form essential components of water supply systems in most urban centres. Water mains buried in the soil/backfill are exposed to different deleterious reactions and—as a result—their design factors of safety may significantly degrade with time, leading to structural failure. In most cases, a combination of circumstances leads to the failure of a pipe. Factors contributing to pipe failure include: operational conditions; design parameters; external loads (traffic, frost, etc.); internal loads (operating and surge pressures); temperature changes; loss of bedding support, pipe properties and condition; and corrosion pit geometry. These are recorded rarely, if at all, and it is therefore very difficult to ascertain the precise causes of failure. Even if all this information were available, any attempt to estimate the pipe condition state would involve considerable uncertainty owing to large spatial and temporal variability that is inherent in this information. Estimation of time to failure is further exacerbated by the uncertainties in determining future corrosion rates. In this paper, corrosion models and a previously developed analytical model based on Winkler-type pipe–soil interaction are used to estimate time to failure. Since available data are insufficient to establish credible probability distributions, uncertainties in the input data/parameters are handled using possibility theory and fuzzy arithmetic. Sensitivity analyses are carried out to identify the critical data/parameters that merit further investigation.
Short-Term Changes in General and Memory-Specific Control Beliefs and their Relationship to Cognition in Younger and Older Adults
Authors: Bielak Allison A. M. , Hultsch David F. , Levy-Ajzenkopf Judi , MacDonald Stuart W. S. , Hunter Michael A. , Strauss Esther
Published: June 2007

We examined short-term changes in younger and older adults' control beliefs. Participants completed measures of general and memory-specific competence and locus of control on 10 bi-monthly occasions. At each occasion, participants rated their control beliefs prior to and following completion of a battery of cognitive tasks. Exposure to the set of cognitively demanding tasks led to declines in older adults' ratings of both general and memory-specific competence compared to little change or increases in younger adults' ratings. Older adults were also more inconsistent in their reported locus of control beliefs across the 10 occasions. Analyses examining the relationship between control beliefs and actual cognitive performance revealed few significant effects, suggesting that short-term changes in perceived control are not driven by monitoring changes in actual performance. The results suggest the importance of assessing short-term as well as long-term changes in perceived control to obtain a complete picture of aging-related changes.
The Grief Experiences of Certified Nursing Assistants: Personal Growth and Complicated Grief
Authors: Anderson Keith A. , Gaugler Joseph E.
Published: June 2007

The grief that certified nursing assistants (CNAs) experience following the deaths of nursing home residents has received scant attention in past research, particularly from an empirical standpoint. The purpose of this quantitative study was to investigate the grief experiences of CNAs in the nursing home setting and to identify and evaluate factors that may mediate or exacerbate grief. Participants ( N = 136) from 12 nursing homes completed self-administered surveys. Regression analyses revealed that CNAs with lower levels of perceived disenfranchised grief reported higher levels of personal growth, while CNAs with greater fear of death and those who experienced fewer deaths on the job reported higher levels of complicated grief. Practitioners and future researchers may benefit from these findings through the construction and implementation of interventions aimed at effectively enfranchising the grief experiences of this important group of healthcare workers.
Trocknungs- und Witterungsverhalten von mondphasengefälltem Fichtenholz (Picea abies Karst.) | Drying and weathering behaviour of Norway Spruce (Picea abies Karst.) wood felled according to moon phases
Authors: Zürcher Ernst
Published: June 2007

In order to investigate the significance of the moon phases at the felling date on wood properties of Norway spruce, 30 trees from the same growth site were felled at six different dates during waxing/ascending, and waning/descending moon cycles, respectively. The present work deals especially with the effect on wood-water-relations of the analysed samples, as well as with the effect on some wood properties after weathering. The results show significant differences in the second half of the experimental felling period.
Wahrnehmung von städtischen Grünräumen und Lebensqualität | Perception of urban green spaces and quality of life
Authors: Wild-Eck Stephan
Published: June 2007

The perception of urban green spaces by the population, as well as their significance, is explored on the basis of empirical studies. It has been found that there is no clear and consistent definition of green spaces, which is a prerequisite before carrying out scientific studies. Urban green spaces have a considerable impact on the quality of life in cities. Accessibility and design of these spaces is an important factor with regard to tapping their full potential, or even only part of it. In particular,objective limitations on access and use, but also subjective barriers may reduce the potential. The relevance of urban green spaces is shown using examples from three different areas: quality of life, well-being, and public health.
Das Risiko eingeschleppter Krankheiten für die Waldbäume | The risk to the forest of introduced diseases
Authors: Heiniger Ursula
Published: June 2007

With increasing globalisation the risk rises for the introduction of new and dangerous tree diseases. Using historical examples of epidemics we analyse the effect of tree diseases on the composition of forest and landscape. We discuss new diseases that could endanger the forests in Switzerland and measures to prevent their introduction.
Data analysis for numerical and categorical individual time‐series
Authors: Saporta G.
Published: June 2007

Principal components analysis and correspondence analysis may be generalized to handle time‐dependent data. For real‐valued data the basic tool is the Karhunen‐Loeve decomposition. For categorical processes harmonic analysis is presented in terms of reciprocal averaging. Details are given for approximated and interpolated solutions.
Classification of medullary lesions among paraplegic patients by the likelihood of the links method
Authors: Lerman I. C.
Published: June 2007

Relative to the problem presented and treated by Parisot in an earlier issue of this journal,1 we present a new solution based on our approach of hierarchical classification. The methodology used, that we will describe in a concise way, allows us to organize either the set of the descriptive variables or the set of the individuals. Its extreme generality includes a set theoretic coding which respects faithfully the globality of the intrinsic nature of the descriptive variables. Very rich results are obtained in terms of classification trees reduced to their ‘significant’ levels. One of the most significant levels corresponds to the partition obtained by Parisot. The ‘significant’ nodes indicate the most relevant associations. The signification is conceived from the empirical distribution — on the successive tree levels — of association coefficients between partition and ‘preordonnance’ (i.e. total preorder on the set of unordered object pairs).
A theoretical model of interpurchase times
Authors: Kahn Barbara E.
Published: June 2007

A theoretical model of interpurchase times at the individual level is developed. This model provides a bench‐mark for the expected regularity of a product's purchase cycle in the absence of any confounding external marketing activity. Products which empirically deviate from the theoretical expectations can then be further studied to determine the causes of the deviations. The theoretical model also tests the robustness of the assumption of a gamma distribution at the individual level, an assumption which is frequently made in the marketing literature.
The analysis of menstrual bleeding patterns: A review
Authors: Belsey E. M. , Farley T. M. M.
Published: June 2007

Patterns of vaginal bleeding are an important factor in the acceptability of contraceptive methods. The analysis of data obtained from daily menstrual diary records is a major methodological problem to which no satisfactory solution exists. This review describes approaches to the analysis of bleeding patterns among contracepting and non‐contracepting women and reviews the difficulties involved. The reference period method, introduced to avoid the arbitrary rules and definitions required for an analysis based on the concept of a menstrual cycle, is discussed and its limitations presented. The review draws on reports of meetings convened by the World Health Organization and the University of Exeter Family Planning Unit to discuss issues in the analysis. Previously unpublished methods are summarized and areas of controversy and topics for further research are identified.
Numerical analysis for factorial data analysis. Part I: Numerical software — the package INDA for microcomputers
Authors: Chatelin F. , Belaid D.
Published: June 2007

A large collection of factorial data analysis methods can be characterized by the following matrices: X, the k x n matrix of data, and A, B the symmetric positive definite matrices of size n, k which represent the chosen norms of ℝn, ℝk, respectively. All methods amount to computing the largest eigenvalues of U = XAXTB or the largest singular values of E = B1/2XA1/2. In Part I of this paper we begin by a geometrical and probabilistic interpretation of the various methods, showing how U and E are defined in each case. We then define the computational kernel for factorial data analysis. We conclude by devising the numerical aspects of software implementation for this kernel on microcomputers and presenting the package INDA.
Updating prognostic indices via regression models
Authors: O'quigley John , Moreau Thierry
Published: June 2007

In medical applications of survival analysis we are often interested in determining prognosis, and the adoption of statistical models in the establishment of a prognostic index has become common practice. The aim of this presentation is to examine the problem of re‐evaluation or the modification of any such index in the light of information subsequent to the initial assessment. Examples are given to highlight the approach.
Numerical analysis for factorial data analysis. Part II: Special purpose hardware—the programmable systolic array SARDA
Authors: Chatelin F. , Porta T.
Published: June 2007

The second part of this paper deals with the systolic implementation of the computational kernel for factorial data analysis, defined in Part I, on special‐purpose hardware. The framework of the study is that a sequence of different algorithms has to be performed on a unique hardware array. This fact has led us to the design of the programmable systolic array SARDA: this is a triangular array which consists of programmable nodes with local memory and programmable orthogonal connections.
Study of the plant recolonization process in a burnt heathland using a method of hierarchical classification
Authors: Tallur B. , Forgeard F.
Published: June 2007

The reinstallation of different plant‐species and their evolution during a ten‐year period in a heathland after a fire accident has been studied by using the algorithm of heirarchical classification based on correlation (ABC) introduced by Tallur.1 Classification under contiguity restraint of the set of observation points (subintervals of an experimental observation line) enables one to determine the ‘patches’ having uniform vegetation structure. Lerman's ‘local’ and ‘global’ statistics are used to condense the classification tree to its significant nodes and to choose the most significant partition. x2 statistics are proposed to test whether a given patch has a ‘significant’ vegetation structure and if the association between a patch and a plant species is significant. Evolution of the horizontal structure of vegetation is studied by comparing the sets of patches obtained at successive observation dates and the corresponding dominant species.
Lagged correlations in simple queueing networks
Authors: McNickle Donald C.
Published: June 2007

The correlations between the queue lengths at nodes in simple Jackson networks are investigated by the randomization numerical method. Although at a fixed point in time these queue lengths are well known to be independent when we compare values at slightly different time points substantial correlation patterns show up. Several classes of systems turn out to have either identical or closely related correlation patterns.
A general pure death process model and the distribution of the time required to remove a fixed number of elements
Authors: Shoukry E. M.
Published: June 2007

The present work derives the distribution of the time required to remove a fixed number of elements W < N, treating the problem as a pure death process with general death rate μn and initial number of elements N. The mean and variance of the distribution time are also obtained. The special case W = N is considered. The results of Sobel et al.1 turn out to be a special case of our results.
Optimality conditions for regenerative inventory systems under batch demands
Authors: Sahin Izzet
Published: June 2007

We consider a single‐item, continuous‐review, (s, S) inventory system, under complete backlogging and a constant procurement lead time. Demands occur in independent, identically distributed batches, separated by independent identically distributed intervals. The model also includes a class of periodic review systems as a special case. Of interest are the optimal control policies with respect to a stationary cost rate function, constructed to include ordering, holding and shortage costs. We study the structural properties of the cost rate function and report some new bounds and optimality conditions. An application of these to the computation and approximation of optimal policies is also discussed.
A comparison of counting process models for complicated life histories
Authors: Mau Jochen
Published: June 2007

The modern statistical theory for counting processes lends itself to flexible non‐parametric analyses of complicated life histories. Its application rests upon a statistical model of multiplicative intensities, adequately constructed for the objectives of the analysis and usually derived from an underlying stochastic model of an individual course of disease. It is shown how survival times and suitable stochastic partitionings of the time axis can yield statistical models of intermittent and multi‐state exposure to a risk of death which otherwise are deduced, under stronger assumptions, from Markovian illness–death processes. Aalen's linear regression model for counting processes is applied in a non‐standard context of intermittent exposure.
Current research directions in the development of expert systems based on belief networks
Authors: Cooper Gregory F.
Published: June 2007

An expert system is a computer program that is designed to solve problems at a level comparable to that of a human expert in a given domain. Often expert systems require a representation of uncertainty. This paper highlights some of the key developments in the history of representing uncertainty in expert systems. An uncertainty representation called belief networks is then introduced and its use in expert systems is motivated. The paper concludes with a discussion of current directions in belief network research.
Reliability analysis of a stand‐by system with repair and intermediate stocks for failed and repaired units
Authors: Brandt A. , Sulanke H.
Published: June 2007

In this paper we give a reliability analysis of a stand‐by system with repair, consisting ofNworking andNRstand‐by units. Failed and repaired units are collected in intermediate stocks. Concerning the delivery from the intermediate stocks we consider two rules: (i) the collected units are delivered in fixed time intervals; (ii) the units will be delivered when there arekunits accumulated. The system fails if a unit that has failed cannot be replaced by a stand‐by unit. Using a point process approach we derive approximations for the stationary availability and mean time between failures of the system. Numerical results show that the proposed approximations, which can be handled easily, work well.
On a new naturally indexed quick clustering method with a global objective function
Authors: Owsiński Jan W.
Published: June 2007

A new clustering method is presented which proposes a class of objective functions and an algorithm which sub‐optimizes the objective functions over the whole space of partitions. The objective functions have a global nature, encompassing both the cluster contents and the cluster number. However, the accompanying suboptimization algorithm works according to a simple progressive merger scheme. The algorithmic scheme produces in a quite natural way an indexed hierarchy. The hierarchy index is not just tacked on to the method—see Diday and Moreau1—on the contrary, the algorithm refers directly to its values which measure, depending upon the particular formulation, either the relative affinity or the relative difference of the two clusters merged at a given level of hierarchy. In this way, the scale of hierarchy and hierarchy‐wise validity of clusters can easily be established, which is of great importance in analysing unstructured data sets whose generating process is unknown and can only be hypothesized after an initial structure had been established, e.g. owing to clustering, as is the case in pattern recognition—see Kaminuma2.
Foundations of the likelihood linkage analysis (LLA) classification method
Authors: Lerman I. C.
Published: June 2007

The aim of this paper is to present the concepts underlying an approach to data analysis using a hierarchical classification. The data can be provided by observation, experiment or knowledge. We begin by presenting the classical view of the context of data representation, in which the algorithm of hierarchical ascendant construction of the classification tree is set. The main notion in our method is one of ‘similarity’. The latter must be elaborated in the best way, taking into account the mathematical nature of the objects to be compared. In this elaboration, we adopt a set theoretic and combinatoric representation of the descriptive attributes, which are interpreted in terms of relations. On the other hand, we introduce a probability scale for similarity measurement by using a likelihood concept.
A bound for wilson's theorem (I)
Authors: Yanxun Chang
Published: June 2007

In 1975, Richard M. Wilson proved: Given any positive integers k ⩾ 3 and λ, there exists a constant v0 = v0(k, λ) such that v ϵ B(k,λ) for every integer v ⩾ v0 that satisfies λ(v − 1) ≡ 0(mod k − 1) and λv(v − 1) ≡ 0[mod k(k − 1)]. The proof given by Wilson does not provide an explicit value of v0. We try to find such a value v0(k, λ). In this article we consider the case λ = 1 and v ≡ 1[mod k(k − 1)]. We show that: if k ⩾ 3 and v = 1[mod k(k − 1)] where v > kkk5, then a B(v,k, 1) exists. © 1995 John Wiley & Sons, Inc.
Cycle structures of automorphisms of 2‐(v,k,1) designs
Authors: Webb Bridget S.
Published: June 2007

An automorphism of a 2−(v,k, 1) design acts as a permutation of the points and as another of the blocks. We show that the permutation of the blocks has at least as many cycles, of lengths n > k, as the permutation of the points. Looking at Steiner triple systems we show that this holds for all n unless n|Cp(n)| ⩽ 3, where Cp(n) is the set of cycles of length n of the automorphism in its action on the points. Examples of Steiner triple systems for each of these exceptions are given. Considering designs with infinitely many points, but with k finite, we show that these results generalize. © 1995 John Wiley & Sons, Inc.
The complete spectrum of 6‐cycle systems of l(kn)
Authors: Cox B. A.
Published: June 2007

In this article, it is shown that a decomposition of the line graph of the complete graph on n vertices into cycles of length 6 exist if and only if n ≢ 3 (mod 4). © 1995 John Wiley & Sons, Inc.
The multiplier conjecture for the case n = 4n1
Authors: Weisheng Qiu
Published: June 2007

In this article we prove that in the case n = 4n1 if (v,2 · 7 · 31) = 1 and v is not divisible by 15, then the Second Multiplier Theorem holds without the assumption n1 > λ. This improves a result due to McFarland. © 1995 John Wiley & Sons, Inc.
Bipartite designs
Authors: Hoffman D. G. , Liatti Mark
Published: June 2007

We determine here those quadruples (a,b,c,d) of positive integers for which the edges of the complete bipartite graph Kc,d can be partitioned into copies of Ka,b.
On circuits and pancyclic line graphs
Authors: Benhocine A. , Clark L. , Köhler N. , Veldman H. J.
Published: June 2007

Clark proved that L(G) is hamiltonian if G is a connected graph of order n ≥ 6 such that deg u + deg v ≥ n – 1 – p(n) for every edge uv of G, where p(n) = 0 if n is even and p(n) = 1 if n is odd. Here it is shown that the bound n – 1 – p(n) can be decreased to (2n + 1)/3 if every bridge of G is incident with a vertex of degree 1, which is a necessary condition for hamiltonicity of L(G). Moreover, the conclusion that L(G) is hamiltonian can be strengthened to the conclusion that L(G) is pancyclic. Lesniak‐Foster and Williamson proved that G contains a spanning closed trail if |V(G)| = n ≥ 6, δ(G) ≥ 2 and deg u + deg v ≥ n – 1 for every pair of nonadjacent vertices u and v. The bound n – 1 can be decreased to (2n + 3)/3 if G is connected and bridgeless, which is necessary for G to have a spanning closed trail.
A generalization of Plantholt's theorem
Authors: Hilton A. J. W.
Published: June 2007

Let K denote the complete graph K2n+1 with each edge replicated r times and let χ′(G) denote the chromatic index of a multigraph G. A multigraph G is critical if χ′(G) > χ′(G/e) for each edge e of G. Let S be a set of sn – 1 edges of K. We show that, for 0 < s ≦ r, G/S is critical and that χ′ (G/(S ∪{e})) = 2rn + r – s for all e ∈ E(G/S). Plantholt [M. Plantholt, The chromatic index of graphs with a spanning star. J. Graph Theory 5 (1981) 5–13] proved this result in the case when r = 1.
On the structure of hereditary classes of graphs
Authors: Scheinerman Edward R.
Published: June 2007

A class of graphs is hereditary if it is closed under taking induced subgraphs. Classes associated with graph representations have “composition sequences” and we show that this concept is equivalent to a notion of “amalgamation” which generalizes disjoint union of graphs. We also discuss how general hereditary classes of graphs are built up from representation classes.
Circuits including a given set of vertices
Authors: Fraisse Pierre
Published: June 2007

Let G = (V, E) be a digraph of order n, satisfying Woodall's condition ∀ x, y ∈ V, if (x, y) ∉ E, then d+(x) + d−(y) ≥ n. Let S be a subset of V of cardinality s. Then there exists a circuit including S and of length at most Min(n, 2s). In the case of oriented graphs we obtain the same result under the weaker condition d+(x) + d−(y) ≥ n – 2 (which implies hamiltonism).
When the cartesian product of two directed cycles is hyperhamiltonian
Authors: Gallian Joseph A. , Witte David
Published: June 2007

We say a digraph G is hyperhamiltonian if there is a spanning closed walk in G which passes through one vertex exactly twice and all others exactly once. We show the cartesian product Za × Zb of two directed cycles is hyperhamiltonian if and only if there are positive integers m and n with ma + nb = ab + 1 and gcd(m, n) = 1 or 2. We obtain a similar result for the vertex‐deleted subdigraphs of Za × Zb.
Edge‐transitive planar graphs
Authors: Grünbaum Branko , Shephard G. C.
Published: June 2007

Graphs which are more or less “symmetric” in one sense or another have been the subject of many investigations. In particular, finite graphs in which all edges are equivalent under isomorphisms of the graph have attracted some attention (see, for example, Fleischner and Imrich [2], Grünbaum and Shephard [5]). Here we extend this investigation to infinite planar graphs which are “reasonable” in the sense that they have locally‐finite plane embeddings. The purpose of this paper is to give a complete enumeration of such graphs, both finite and infinite.

We remark that the seemingly similar problem of determining all planar graphs in which the vertices are equivalent under isomorphisms of the graph appears to be much harder, and at present we are very far from a solution.
Spanning trails
Authors: Catlin Paul A.
Published: June 2007

For a graph G with distinguished vertices u and v, we give a sufficient condition for the existence of a (u, v)‐trail containing every vertex of G.
Pancyclic and panconnected line graphs
Authors: Benhocine Abdelhamid , Fouquet Jean‐Luc
Published: June 2007

Let G be a graph of order n ⩾ 3. We prove that if G is k‐connected (k ⩾ 2) and the degree sum of k + 1 mutually independent vertices of G is greater than 1/3(k + 1)(n + 1), then the line graph L(G) of G is pancyclic. We also prove that if G is such that the degree sum of every 2 adjacent vertices is at least n, then L(G) is panconnected with some exceptions.
Minimal extensions of graphs to absolute retracts
Authors: Pesch Erwin
Published: June 2007

A graph H is an absolute retract if for every isometric embedding h of, into a graph G an edge‐preserving map g from G to H exists such that g · h is the identity map on H. A vertex v is embeddable in a graph G if G − v is a retract of G. An absolute retract is uniquely determined by its set of embeddable vertices. We may regard this set as a metric space. We also prove that a graph (finite metric space with integral distance) can be isometrically embedded into only one smallest absolute retract (injective hull). All graphs in this paper are finite, connected, and without multiple edges.
Homomorphisms of graphs into odd cycles
Authors: Gerards A. M. H.
Published: June 2007

We give a class of graphs G for which there exists a homomorphism (= adjacency preserving map) from V(G) to V(C), where C is the shortest odd cycle in G, thereby extending a result of Albertson, Catlin, and Gibbons. Our class of graphs is characterized by the following property: For each odd subdivision G′ of G there exists a homomorphic map from V(G′) to V(C), where C′ is the shortest odd cycle of G′.
Hamiltonian properties of the cube of a 2‐edge connected graph
Authors: Paoli M.
Published: June 2007

Let G be a 2‐edge connected graph with at least 5 vertices. For any given vertices a, b, c, and d in G with a ≠ b, there exists in G3 a hamiltonian path with endpoints a and b avoiding the edge cd, and there exists in G3 ∪ {cd} a hamiltonian path with endpoints a and b and containing the edge cd. Also, after removal of two edges or one edge and one vertex from G3, the resulting graph is still hamiltonian.
A lower bound on the number of spanning trees with k end‐vertices
Authors: Heinrich Katherine , Liu Guizhen
Published: June 2007

If a graph G with cycle rank ρ contains both spanning trees with m and with n end‐vertices, m < n, then G has at least 2ρ spanning trees with k end‐vertices for each integer k, m < k < n. Moreover, the lower bound of 2ρ is best possible.
Exotic n‐universal graphs
Authors: Parsons T. D. , Pisanski Tomaž
Published: June 2007

An n‐universal graph is a graph that contains as an induced subgraph a copy of every graph on n vertices. It is shown that for each positive integer n > 1 there exists an n‐universal graph G on 4n ‐ 1 vertices such that G is a (v, k, λ)‐graph, and both G and its complement G¯ are 1‐transitive in the sense of W. T. Tutte and are of diameter 2. The automorphism group of G is a transitive rank 3 permutation group, i.e., it acts transitively on (1) the vertices of G, (2) the ordered pairs uv of adjacent vertices of G, and (3) the ordered pairs xy of nonadjacent vertices of G.
Nowhere‐zero flows in low genus graphs
Authors: Möller Martina , Carstens Hans Georg , Brinkmann Gunnar
Published: June 2007

A nowhere‐zero k‐flow is an assignment of edge directions and integer weights in the range 1,…, k − 1 to the edges of an undirected graph such that at every vertex the flow in is equal to the flow out. Tutte has conjectured that every bridgeless graph has a nowhere‐zero 5‐flow. We show that a counterexample to this conjecture, minimal in the class of graphs embedded in a surface of fixed genus, has no face‐boundary of length <7. Moreover, in order to prove or disprove Tutte's conjecture for graphs of fixed genus γ, one has to check graphs of order at most 28(γ − 1) in the orientable case and 14(γ − 2) in the nonorientable case. So, in particular, it follows immediately that every bridgeless graph of orientable genus ⩽1 or nonorientable genus ⩽2 has a nowhere‐zero 5‐flow. Using a computer, we checked that all graphs of orientable genus ⩽2 or nonorientable genus ⩽4 have a nowhere‐zero 5‐flow.
Chromaticity of triangulated graphs
Authors: Vaderlind Paul
Published: June 2007

It is shown here that a connected graph G without subgraphs isomorphic to K4 is triangulated if and only if its chromatic polynomial P(G,λ) equals λ(λ − 1)m(λ − 2)r for some integers m ≧ 1, r ≧ 0. This result generalizes the characterization of Two‐Trees given by E.G. Whitehead [“Chromaticity of Two‐Trees,” Journal of Graph Theory 9 (1985) 279–284].
Degree sum for a triangle in a graph
Authors: Fan Genghua
Published: June 2007

Let 𝒢(n; e) denote the class of graphs on n vertices and e edges. Define f(n, e) = min max{Σ d(vi):{v1, v2,v3} induces a triangle in G}, where the maximum is taken over all triangles in the graph G and the minimum is taken over all G in 𝒢(n; e). From Turán's theorem, f(n, e) = 0 if e ⩽ n2/4; otherwise f(n,e) > 0. Bollobás and Erdös [1] asked to determine the function f(n,e) for e > n2/4. Edwards [3] proved that f(n,e) ⩾ 6e/n for e ≥ n2/3. In this paper, we consider the remaining case, namely, n2/4 < e < n2/3. A construction described in [4] shows that f(n,e) < 4 √3¯e ‐ 2n + 5. We prove that f(n,e) ≥ 21e/4n. In particular, f(n, ⌊n2/4⌋ + 1) > 21n/16, which improves a result of Erdös and Laskar [4] that f(n, ⌊n2/4⌋ + 1) > (1 + ε)n for some positive constant ε. Furthermore, if e ⩾ 0.26n2, we obtain a better result.
On the parity of crossing numbers
Authors: Archdeacon Dan , Richter R. Bruce
Published: June 2007

For an integer n ⩾ 1, a graph G has an n‐constant crossing number if, for any two good drawings ϕ and ϕ′ of G in the plane, μ(ϕ) ≡ μ(ϕ′) (mod n), where μ(ϕ) is the number of crossings in ϕ. We prove that, except for trivial cases, a graph G has n‐constant crossing number if and only if n = 2 and G is either Kp or Kq,r, where p, q, and r are odd.
On feedback vertex sets and nonseparating independent sets in cubic graphs
Authors: Speckenmeyer Ewald
Published: June 2007

Let G be an undirected connected graph with n nodes. A subset F of nodes of G is a feedback vertex set (fvs) if G − F is a forest and a subset J of nodes of G is a nonseparating independent set (nsis) if no two nodes of J are adjacent and G − J is connected. f(G), z(G) denote the cardinalities of a minimum fvs and a maximum nsis, respectively, of G. The equation f(G) = n/2 − z(G) + 1 and two new upper bounds on f(G) are derived for cubic graphs G.
A result on Hamiltonian line graphs involving restrictions on induced subgraphs
Authors: Veldman H. J.
Published: June 2007

It is shown that the existence of a Hamilton cycle in the line graph of a graph G can be ensured by imposing certain restrictions on certain induced subgraphs of G. Thereby a number of known results on hamiltonian line graphs are improved, including the earliest results in terms of vertex degrees. One particular consequence is that every graph of diameter 2 and order at least 4 has a hamiltonian line graph.
Counting double covers of graphs
Authors: Hofmeister M.
Published: June 2007

Any group of automorphisms of a graph G induces a notion of isomorphism between double covers of G. The corresponding isomorphism classes will be counted.
On connectivities of tree graphs
Authors: Liu Guizhen
Published: June 2007

Let T(G) be the tree graph of a graph G with cycle rank r. Then κ(T(G)) ⩾ m(G) − r, where κ(T(G)) and m(G) denote the connectivity of T(G) and the length of a minimum cycle basis for G, respectively. Moreover, the lower bound of m(G) − r is best possible.
An 11‐vertex theorem for 3‐connected cubic graphs
Authors: Aldred R. E. L. , BauSheng  , Holton D. A. , Royle Gordon F.
Published: June 2007

In this paper we determine the circumstances under which a set of 11 vertices in a 3‐connected cubic graph lies on a cycle. In addition, we consider the number of such cycles that exist and characterize those graphs in which a set of 9 vertices lies in exactly two cycles.
Circumference of a regular graph
Authors: Aung Min
Published: June 2007

It is proved that a 4‐connected, δ‐regular graph G either is Hamiltonian, or has at least 3δ + 1 vertices and contains a cycle of length at least min{4δ ‐ 4, 1/2 (|G| + 3δ ‐ 2)}. Examples supplied by B. Jackson and H.A. Jung show that min{4δ ‐ 4, 1/2(|G| + 3δ ‐ 2)} cannot be replaced by 4δ + 1.
Ramsey numbers for graphs with five vertices
Authors: Hendry George R. T.
Published: June 2007

The Ramsey numbers r(F1, F2) are tabulated for essentially all but six pairs of graphs F1 and F2 with five vertices.
Common root functions of two digraphs
Authors: Mao‐cheng Cai
Published: June 2007

Let D1 and D2 be finite digraphs, both with vertex set V, let a and b be given functions from V to Z+, and let k be a positive integer. In this paper we give a necessary and sufficient condition for the existence of k arc‐disjoint arborescences in each of D1 and D2 satisfying the condition that for each v in V

magnified image a(v) <r1(v) = r2(v) < b(v).

Where ri(v) denotes the number of the arborescences in Di rooted at v, i = 1, 2.
Repeated edges in 2‐factorizations
Authors: Colbourn Charles J. , Rosa Alexander
Published: June 2007

The spectrum of numbers of repeated edges in 2‐factorizations of 2Kn is determined for all n. The techniques employed are direct, using isomorphic factorizations of Kn, and closely related factorizations.
Local government boards in canada
Authors: Bayne J. N.
Published: June 2007

For twenty years American political scientists have seen hope in the principle of flexible state administrative supervision over municipal finance as a substitute for legislative interference and modern limitation, in line with the famous British local government board. In the last six years such boards have developed widely in Canada.
The fate of the five‐cent fare VIII. Detroit—a tale of distrust
Authors: Fitzgerald Edward T.
Published: June 2007

Every city's situation is difficult, and every city's situation is different but as these stories are told, the cases of ‘procrastinate and let the corporation squeal and the service deteriorate’ are beginning to have a familiar sound.
Sandusky and the manager plan
Authors: Hatton Augustus R.
Published: June 2007

Dr. Hatton has recently visited seven typical cities having the citymanager plan of municipal government and we expect to carry the story of his findings in the “Review” from now on. Sandusky is important because it is one of the towns from which accounts were persistently disturbing and conflicting.
Dynamic Stress Concentration around a Rectangular Crack in an Infinite Elastic Medium
Authors: Itou S.
Published: June 2007

The three‐dimensional problem of diffraction of elastic waves by a rectangular crack in an infinite elastic medium is investigated in this paper. The Fourier transform technique is used to reduce the problem to a solution of two simultaneous integral equations. To solve these equations, the crack surface displacement is expanded in a function with a double series. The unknown coefficients accompanied in that series are calculated with the aid of the Schmidt method. The dynamic stress intensity factors and the crack surface displacement are numerically computed.
Verallgemeinerte m‐Punkt‐Sekantenverfahren für schwach besetzte nichtlineare Gleichungssysteme
Authors: Mönch W.
Published: June 2007

Es werden verallgemeinerte m‐Punkt‐Sekantenverfahren zur Lösung nichtlinearer Gleichungssysteme angepaßt an Aufgaben mit schwach besetzter Jacobi‐Matrix. Diese angepaßten Algorithmen werden an einigen numerischen Beispielen mit dem Verfahren von Schubert verglichen.
Optimization of Nordsieck's Method for the Numerical Integration of Ordinary Differential Equations
Authors: Gmelig R. H. J. , Traas C. R.
Published: June 2007

Stability and accuracy of Nordsieck's integration method can be improved by choosing the zero‐positions of the extraneous roots of the characteristic equation in a suitable way. Optimum zero‐positions have been found by minimizing the lower bound of the interval of absolute stability and the coefficient of the truncation error. Various properties of the improved methods have been analysed, such as the behaviour of the high‐order terms, the equivalence with multistep methods and the damping of perturbations.
Pressure Loaded Structures under Large Deformations
Authors: Bufler H.
Published: June 2007

Pressure loads are configuration dependent. The magnitude of the pressure may be considered as a function of the Eulerian or the Lagrangian coordinates respectively. The first (natural) case turns out to be conservative if a certain line integral vanishes; the second (artificial) one is always nonconservative. Basing on the theory of potential operators the condition for the conservativeness of a pressure loading acting on a finitely deformed structure is derived and the corresponding potential and incremental potential are calculated. They are needed for the variational principles of conservative elastic boundary value problems. In the nonconservative case the principle of virtual displacements and its incremental version respectively serve as an adequate description.
The Role of the Tangent Mapping in Analyzing Bifurcation Behaviour
Authors: Fink J. P. , Rheinboldt W. C.
Published: June 2007

In the study of solution manifolds of parameter‐dependent nonlinear equations extended systems of equations play an important role, especially for the computation of singular points, such as turning points, bifurcation points, etc. Various extended systems have been proposed in the literature. Here it is shown that a central feature in the construction of extended systems is the tangent map of differential geometry. A theory of extended equations based on the tangent map is presented which also exhibits the close connection with the choice of local coordinate systems. The ideas and results are illustrated with an example of a continuously stirred chemical reactor.
Zur Darstellung des turbulenten Wärmestroms
Authors: Oswatitsch K.
Published: June 2007

Das Gesetz für den turbulenten Wärmestrom wird auf neuem Wege Über einen Entropieerhaltungssatz hergeleitet. Es besagt, daß der Wärmestrom proportional zum Gefälle der potentiellen Temperatur oder zum Entropiegefälle ist und nicht zum Gefälle der Temperatur, wie dies die Fouriersche Wärmeleitungsgleichung aussagt. Der Unterschied ist insbesondere für turbulente Grenzschichten der Atmosphäre von Bedeutung, weil dort die beiden Gefälle entgegengesetzt gerichtet sein können.
Über explizite, halbimplizite und implizite Algorithmen zur endlichen und iterativen Transformation von Matrizenpaaren
Authors: Falk S.
Published: June 2007

Mit Hilfe einer neuen Strategie werden einige der bekannten multiplikativen Algorithmen (HOUSEHOLDER, HESSENBERG, DANILEWSKI, JACOBI u. a.) auf reguläre Paare verallgemeinert, ohne daß die Matrix B−1A oder eine ihr gleichwertige Umformung explizit berechnet werden müßte.
On the Convergence of the Energy, Stress Tensors, and Eigenvalues in Homogenization Problems of Elasticity
Authors: Oleinik O. A. , Shamaev A. S. , Yosifian G. A.
Published: June 2007

In this paper we study the convergence of energy integrals, stress tensors and frequencies of free vibrations for non‐homogeneous and porous elastic bodies with a periodic structure of period ε as ε → 0. The results are based on the estimates for solutions of the boundary value problem of the elasticity system with rapidly oscillating periodic coefficients, obtained in [4], [11].
Fehlerabschätzung für eine Differenzenmethode zur Approximation schwacher Lösungen von Stefan‐Aufgaben
Authors: Streit U. , Weinelt W.
Published: June 2007

In der Arbeit wird eine implizite Differenzenmethode (Gitterparameter h, τ) zur Berechnung der schwachen Lösung einer eindimensionalen Stefan‐Aufgabe betrachtet, wobei die Enthalpiefunktion geeignet approximiert wird (Parameter Δ). Unter Schwachen Regularitätsvoraussetzungen werden Fehlerabschätzungen für diese Methode gefunden. Hauptresultat ist eine Konvergenzordnung von O(Δ1/4 + h½ + τ½) in der L2‐Norm.
On Existence, Uniqueness and Asymptotic Behavior of Solutions of the Basic Equations for Carrier Transport in Semiconductors
Authors: Gajewski H.
Published: June 2007

Existence and uniqueness of temporally global solutions of the basic equations for the carrier transport in semiconductors are proved. Moreover, sufficient conditions for the convergence of transit carrier distributions to thermal equilibrium and quasi‐equilibrium distributions are formulated.
A Survey of One‐Step Splitting Methods for Semi‐Discrete First Order Hyperbolic Partial Differential Equations
Authors: de Vries H. B.
Published: June 2007

In this paper spliting methods are discussed for first order hyperbolic partial differential equations via the method of lines, and in particular the time integration will be discussed. A class of one‐step integration formulas is defined, which is shown to contain several well‐known spliting methods. For a number of methods stability results are given.