Analysis of Exogenous Components of Mortality Risks

A new technique for deriving exogenous components of mortality risks from national vital statistics has been developed. Each observed death rate D_ij (where i corresponds to calendar time (year or interval of years) and j denotes the number of corresponding age group) was represented as D_ij=A_j+B_iC_j, and unknown quantities A_j, B_i, and C_j were estimated by a special procedure using the least-squares principle. The coefficients of variation do not exceed 10%. It is shown that the term A_j can be interpreted as the endogenous and the second term B_iC_j as the exogenous components of the death rate. The aggregate of endogenous components A_j can be described by a regression function, corresponding to the Gompertz-Makeham law, A(τ) =γ+β· eατ, where γ, β, and α are constants, τ is age, AττAττA_j, and τ_j, is the value of age τ in jth age group. The coefficients of variation for such a representation does not exceed 4%. An analysis of exogenous risk levels in the Moscow and Russian populations during 1980–1995 shows that since 1992 all components of exogenous risk in the Moscow population had been increasing up to 1994. The greatest contribution to the total level of exogenous risk was lethal diseases, and their death rate was 387 deaths per 100,000 persons in 1994, i.e., 61.9% of all deaths. The dynamics of exogenous mortality risk change during 1990–1994 in the Moscow population and in the Russian population without Moscow had been identical: the risk had been increasing, and its value in the Russian population had been higher than that in the Moscow population.     

Sharp bounds of the Zagreb indices of k-trees

For a graph G, the first Zagreb index M ₁ is equal to the sum of squares of the vertex degrees, and the second Zagreb index M ₂ is equal to the sum of the products of degrees of pairs of adjacent vertices. The Zagreb indices have been the focus of considerable research in computational chemistry dating back to Gutman and Trinajsti? in 1972. In 2004, Das and Gutman determined sharp upper and lower bounds for M ₁ and M ₂ values for trees along with the unique trees that obtain the minimum and maximum M ₁ and M ₂ values respectively. In this paper, we generalize the results of Das and Gutman to the generalized tree, the k-tree, where the results of Das and Gutman are for k=1. Also by showing that maximal outerplanar graphs are 2-trees, we also extend a result of Hou, Li, Song, and Wei who determined sharp upper and lower bounds for M ₁ and M ₂ values for maximal outerplanar graphs.     

The Pfaffian property of Cartesian products of graphs

Suppose that G=(V,E) is a graph with even vertices. An even cycle C is a nice cycle of G if G?V(C) has a perfect matching. An orientation of G is a Pfaffian orientation if each nice cycle C has an odd number of edges directed in either direction of the cycle. Let P _n and C _n denote the path and the cycle on n vertices, respectively. In this paper, we characterize the Pfaffian property of Cartesian products G×P _2n and G×C _2n for any graph G in terms of forbidden subgraphs of G. This extends the results in (Yan and Zhang in Discrete Appl Math 154:145–157, 2006).     

Penta-Extensions of Hereditary Classes of Graphs

Penta is the configuration shown in figure 1(a), where continuous lines represent edges and dotted lines represent non-edges. The vertex u in figure 1(a) is called the center of Penta. A graph G is called a pentagraph if every induced subgraph H of G has a vertex v which is not a center of induced Penta in H. The class of pentagraphs is a common generalization of chordal [triangulated] graphs and Mahadev graphs. We construct a polynomial-time algorithm that either find a maximum stable set of G or concludes that G is not a pentagraph. We propose a method for extending α-polynomial hereditary classes based on induced Pentas.     

Edge-colouring of joins of regular graphs II

We prove that the edges of every even graph G=G ₁+G ₂ that is the join of two regular graphs G ₁ and G ₂ can be coloured with Δ(G) colours, whenever Δ(G)=Δ(G ₁)+|V ₂|. The proof of this result together with the results in De Simone and Galluccio (J. Comb. Optim. 18:417–428, 2009) states that every even graph G that is the join of two regular graphs is Class 1. The proof yields an efficient combinatorial algorithm to find a Δ(G)-edge-colouring of this type of graphs.     

Further Evaluation of the Accuracy of Managerial Prediction of Employee Preference

Previous research (i.e., Wilder, Rost, &; McMahon, 2007 Wilder, D. A., Rost, K. and McMahon, M. 2007. The accuracy of managerial prediction of employee preference: A brief report. Journal of Organizational Behavior Management, 27(2): 1–14. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) has suggested that managers perform poorly when predicting items and activities which their employees state that they might like to earn as part of performance improvement programs. The purpose of the current study was to replicate the earlier study conducted by Wilder et al. (2007 Wilder, D. A., Rost, K. and McMahon, M. 2007. The accuracy of managerial prediction of employee preference: A brief report. Journal of Organizational Behavior Management, 27(2): 1–14. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) with a larger and more diverse sample of managers and employees. One hundred employees and 15 managers were asked to rank order a list of items/activities they thought their employees would most prefer to be incorporated into a performance improvement plan. Next, employee preference for these same items was directly assessed using an employee reinforcer survey. Kendall rank-order correlation coefficients were used to compare the results of the managerial rank with the employee reinforcer survey. Correlations ranged from ?.6 to 1, with a mean of .25.     

On the union of intermediate nodes of shortest paths

Consider a connected graph G=(V,E). For a pair of nodes u and v, denote by M _uv the set of intermediate nodes of a shortest path between u and v. We are intertested in minimization of the union ? _u,v∈V M _uv . We will show that this problem is NP-hard and cannot have polynomial-time ρlnδ-approximation for 0<ρ<1 unless NP?DTIME(n ^O(loglogn)) where δ is the maximum node degree of input graph. We will also construct a polynomial-time $H(\frac{\delta (\delta -1)}{2})$ -approximation for the problem where H(?) is the harmonic function.     

Minimal Tetrahedralizations of a Class of Polyhedra

Given a simple polyhedron P in the three dimensional Euclidean space, different tetrahedralizations of P may contain different numbers of tetrahedra. The minimal tetrahedralization is a tetrahedralization with the minimum number of tetrahedra. In this paper, we present some properties of the graph of polyhedra. Then we identify a class of polyhedra and show that this kind of polyhedra can be minimally tetrahedralized in O(n ²) time.     

Equivalence of two conjectures on equitable coloring of graphs

A graph G is said to be equitably k-colorable if there exists a proper k-coloring of G such that the sizes of any two color classes differ by at most one. Let Δ(G) denote the maximum degree of a vertex in G. Two Brooks-type conjectures on equitable Δ(G)-colorability have been proposed in Chen and Yen (Discrete Math., 2011) and Kierstead and Kostochka (Combinatorica 30:201–216, 2010) independently. We prove the equivalence of these conjectures.     

Opportunities of Reforming the WTO: Resistance and Potentials of Change

This paper intends to show both that a reform of the WTO is severely needed in order to establish a fairer international trade order but also that it is possible. The first section of this paper analyzes the functioning and the most controversial rules of the organization. The second and third sections intend to look for current opportunities of reforming the WTO by analyzing the main existing critical responses to the institution’s deficiencies—namely coalitions of southern Nation-States and global civil society movements—and their potential to achieve some change. It is concluded that these two key group actors, while playing different roles, do have common goals on selected issues of international trade and if so, their combined negotiating power is considerably increased for achieving a progress in the direction of a positive reform of the WTO for the developing world.

Governance of open source software: state of the art

In this overview of governance mechanisms developed within open source software (OSS) circles, three types of governance are studied: ‘spontaneous’ governance, internal governance, and governance towards outside parties. Moreover, two main ways in which lessons from OSS can be applied elsewhere are explored: peer production of products other than software, and embedding ‘peer-produced’ products and peer processes into existing institutions (‘coupling’).

Sensitivity of the Optimum to Perturbations of the Profit or Weight of an Item in the Binary Knapsack Problem

In the binary single constraint Knapsack Problem, denoted KP, we are given a knapsack of fixed capacity c and a set of n items. Each item j, j = 1,...,n, has an associated size or weight w_j and a profit p_j. The goal is to determine whether or not item j, j = 1,...,n, should be included in the knapsack. The objective is to maximize the total profit without exceeding the capacity c of the knapsack. In this paper, we study the sensitivity of the optimum of the KP to perturbations of either the profit or the weight of an item. We give approximate and exact interval limits for both cases (profit and weight) and propose several polynomial time algorithms able to reach these interval limits. The performance of the proposed algorithms are evaluated on a large number of problem instances.     

Central State Steering of Local Collaboration: Assessing the Impact of Tools of Meta-governance in Homelessness Services in England

Much of the discussion of state steering of service delivery networks to encourage collaboration at the local level has been theoretical. This study builds on this analysis systematically to assess the relationship between meta-governance tools of central government steering and the extent of local collaboration, using the case of homelessness services in England. Contrary to the pessimist expectations of some contemporary theory, central government funding tools and facilitating the transfer of best practice encourages collaboration. However, simple information provision and authority based tools are only partially effective, risking tokenistic compliance. Authority tools are more effective when combined with other tools.

A meta-analytic examination of the potential correlates and consequences of workload

Over the last four decades, occupational stress researchers have given considerable attention to the potential correlates and consequences of workload. In the current study, we use meta-analysis (overall k = 336) to quantitatively review the workload literature. In analyses of hypothesized correlates, we found that social support was negatively associated (ρ = ?.20 for supervisor support; ρ = –.11 for co-worker support) and that trait negative affectivity (ρ = .22), role ambiguity (ρ = .28), role conflict (ρ = .44) and work-family conflict (ρ = .44 for work-to-family conflict; ρ = .20 for family-to-work conflict) were each positively associated with workload. Analyses examining hypothesized outcome variables suggest that workload is negatively associated with several indices of psychological and physical well-being (ρs were generally in the –.20s and –.30s), and affective organizational commitment (ρ = –.11), and is positively associated with turnover intention (ρ = .16) and absenteeism (ρ = .07).     

L(2,1)-labelings of the edge-path-replacement of a graph

For two positive integers j and k with j≥k, an L(j,k)-labeling of a graph G is an assignment of nonnegative integers to V(G) such that the difference between labels of adjacent vertices is at least j, and the difference between labels of vertices that are distance two apart is at least k. The span of an L(j,k)-labeling of a graph G is the difference between the maximum and minimum integers used by it. The L(j,k)-labelings-number of G is the minimum span over all L(j,k)-labelings of G. This paper focuses on L(2,1)-labelings-number of the edge-path-replacement G(P _k ) of a graph G. Note that G(P ₃) is the incidence graph of G. L(2,1)-labelings of the edge-path-replacement G(P ₃) of a graph, called (2,1)-total labeling of G, was introduced by Havet and Yu in 2002 (Workshop graphs and algorithms, Dijon, France, 2003; Discrete Math. 308:498–513, 2008). They (Havet and Yu, Discrete Math. 308:498–513, 2008) obtain the bound $\Delta+1\leq\lambda^{T}_{2}(G)\leq2\Delta+1$ and conjectured $\lambda^{T}_{2}(G)\leq\Delta+3$ . In this paper, we obtain that λ(G(P _k ))≤Δ+2 for k≥5, and conjecture λ(G(P ₄))≤Δ+2 for any graph G with maximum degree Δ.     

On the upper total domination number of Cartesian products of graphs

In this paper we continue the investigation of total domination in Cartesian products of graphs first studied in (Henning, M.A., Rall, D.F. in Graphs Comb. 21:63–69, 2005). A set S of vertices in a graph G is a total dominating set of G if every vertex in G is adjacent to some vertex in S. The maximum cardinality of a minimal total dominating set of G is the upper total domination number of G, denoted by Γ _t (G). We prove that the product of the upper total domination numbers of any graphs G and H without isolated vertices is at most twice the upper total domination number of their Cartesian product; that is, Γ _t (G)Γ _t (H)≤2Γ _t (G □ H). Research of M.A. Henning supported in part by the South African National Research Foundation and the University of KwaZulu-Natal.     

Point sets in the unit square and large areas of convex hulls of subsets of points

In this paper generalizations of Heilbronn’s triangle problem to convex hulls of j points in the unit square [0,1]² are considered. By using results on the independence number of linear hypergraphs, for fixed integers k≥3 and any integers n≥k a deterministic o(n ^6k−4) time algorithm is given, which finds distributions of n points in [0,1]² such that, simultaneously for j=3,…,k, the areas of the convex hulls determined by any j of these n points are Ω((log n)^1/(j−2)/n ^{(j−1)/(j−2)}).     

信息披露的作用 ——来自拍拍贷的经验证据

  信息披露对于降低信息不对称、减少市场的非效率的作用已经得到广泛的认可。因为中国依然缺乏完善的征信体系,P2P市场上也存在着更严重的信息不对称,所以信息披露在P2P借贷市场中发挥着更为重要的作用,值得学界和业界更深入的研究。         基于拍拍贷的数据,对信息披露在P2P市场上的作用进行研究。为了比较可验证的和不可验证的标准信息披露的不同作用,选择Logistic和Tobit等不同的回归模型以及不同的模型设置,实证检验其对于是否借款成功、是否违约、内部收益率的影响以及与借款利率之间的关系。         研究结果表明,信息披露对借款成功有正向影响,可验证的标准信息披露影响更大;信息披露具有的可验证性对借款成功有正向影响。同时,信息披露多的借款者更愿意提高借款利率,表明他们可能具有更低的信用。信息披露并不总是降低违约风险,部分信息及其可验证性反而导致更高的违约率。为了得到更可靠的结果,进一步对信息披露和内部收益率进行研究,结果同样表明,部分信息披露及其可验证性会带来更低的内部收益率。在稳健性检验中,上述结论依然不变。         研究结果丰富了信息披露、信息经济学、行为经济的研究内容,有利于平台设计更好的信息披露机制,即应控制披露信息条目,只披露能反映风险的信息,从而减少信息不对称,降低由投资人决策偏差导致的损失。同时,也为监管部门制定监管条例去纠正市场偏差和保护投资者权益提供了实证依据。