Coloring vertices of claw-free graphs in three colors

We study the computational complexity of the vertex 3-colorability problem in the class of claw-free graphs. Both the problem and the class received much attention in the literature, separately of each other. However, very little is known about the 3-colorability problem restricted to the class of claw-free graphs beyond the fact the problem is NP-complete under this restriction. In this paper we first strengthen this negative fact by revealing various further restrictions under which the problem remains NP-complete. Then we derive a number of positive results that deal with polynomially solvable cases of the problem in the class of claw-free graphs.     

Computing unique maximum matchings in $$$$ time for König–Egerváry graphs and unicyclic graphs

Let \(\alpha \left( G\right) \) denote the maximum size of an independent set of vertices and \(\mu \left( G\right) \) be the cardinality of a maximum matching in a graph \(G\). A matching saturating all the vertices is a perfect matching. If \(\alpha \left( G\right) +\mu \left( G\right) =\left| V(G)\right| \), then \(G\) is called a König–Egerváry graph. A graph is unicyclic if it is connected and has a unique cycle. It is known that a maximum matching can be found in \(O(m\cdot \sqrt{n})\) time for a graph with \(n\) vertices and \(m\) edges. Bartha (Proceedings of the 8th joint conference on mathematics and computer science, Komárno, Slovakia, 2010) conjectured that a unique perfect matching, if it exists, can be found in \(O(m)\) time. In this paper we validate this conjecture for König–Egerváry graphs and unicylic graphs. We propose a variation of Karp–Sipser leaf-removal algorithm (Karp and Sipser in Proceedings of the 22nd annual IEEE symposium on foundations of computer science, 364–375, 1981) , which ends with an empty graph if and only if the original graph is a König–Egerváry graph with a unique perfect matching (obtained as an output as well). We also show that a unicyclic non-bipartite graph \(G\) may have at most one perfect matching, and this is the case where \(G\) is a König–Egerváry graph.     

A critical look at Lo's modified R/S statistic

We report on an empirical investigation of the modified rescaled adjusted range or R/S statistic that was proposed by Lo, 1991. Econometrica 59, 1279–1313, as a test for long-range dependence with good robustness properties under ‘extra’ short-range dependence. In contrast to the classical R/S statistic that uses the standard deviation S to normalize the rescaled range R, Lo's modified R/S-statistic V_q is normalized by a modified standard deviation S_q which takes into account the covariances of the first q lags, so as to discount the influence of the short-range dependence structure that might be present in the data. Depending on the value of the resulting test-statistic V_q, the null hypothesis of no long-range dependence is either rejected or accepted. By performing Monte-Carlo simulations with ‘truly’ long-range- and short-range dependent time series, we study the behavior of V_q, as a function of q, and uncover a number of serious drawbacks to using Lo's method in practice. For example, we show that as the truncation lag q increases, the test statistic V_q has a strong bias toward accepting the null hypothesis (i.e., no long-range dependence), even in ideal situations of ‘purely’ long-range dependent data.     

Peer group self-identification in samples of Russian and U.S. adolescents

Most peer group self-identification research has been conducted in the United States. This article examined the generalizability of self-identified group name research among teens in Ufa, a city in the Russian Federation. A cross-sectional, anonymous collection of data on group self-identification, drug use, addiction concern, sensation seeking, and self-rated school performance was collected from 365 10th grade youth in Ufa and 965 10th grade youth in the United States. The results supported the existence of peer group self-identification by youth in both countries and, in general, replicated the findings that youth who self-identify as a High Risk Youth, are relatively likely to use drugs, show greater concern about becoming an addict, report a greater sensation seeking preference, higher levels of depression, and poorer school performance. Implications of these results are discussed.     

Russian Bioscience Publications and Journals in International Bibliometric Databases

This article analyzes shares and rankings of Russian bioscience publications and journals in international bibliometric databases. Studying scholarly output, international collaboration, and the share of Russian papers both in national and international journals enables the authors to highlight the current state of biological science and journals in Russia and outline some pronounced trends. A comparative analysis with the leading countries confirms good representation of Russian bioscience journals among other international serials. Certain problems remain unsolved, however: low impact factors, overrepresentation of national papers, and poor online services. Thus, Russian publishers should correct their editorial policy to improve availability and performance of serials.     

The relevance and impact of business schools: In search of a holistic view

The degree to which business schools are relevant and impactful for society has been disputed. Critics that engage in the so-called ‘relevance problem’ have argued that business schools are preoccupied with academic rigour at the expense of practical relevance, resulting in a lack of societal impact. This systematic literature review synthesizes the fragmented body of knowledge pertaining to the relevance and impact of business schools. Appreciating the contributions of both research and education, this review offers a holistic view that acknowledges the multidimensional nature of business schools. Based on an analysis of 266 journal articles, we present the four main literature streams in this domain. We find limited evidence of cross-fertilisation between discussions of research and education. However, by acknowledging the contribution of applying a multidimensional lens to the study of business schools, we develop a holistic thematic framework that provides theoretical directions for the future. Using this, we demonstrate four avenues for advancing the business school literature. First, we emphasise the potential of an institutional logics perspective to viewing business schools. Second, we offer a novel proposal for understanding the bridge between research and education. Third, we emphasise the application of a value co-creation theoretical lens when considering how business schools engage with stakeholders in research and education. Finally, we propose an all-encompassing stakeholder-centric definition of relevant and impactful knowledge and advocate for this inclusive definition to conceptually bridge the fragmented discussions of research and education.     

Weak Identification in Fuzzy Regression Discontinuity Designs

In fuzzy regression discontinuity (FRD) designs, the treatment effect is identified through a discontinuity in the conditional probability of treatment assignment. We show that when identification is weak (i.e., when the discontinuity is of a small magnitude), the usual t-test based on the FRD estimator and its standard error suffers from asymptotic size distortions as in a standard instrumental variables setting. This problem can be especially severe in the FRD setting since only observations close to the discontinuity are useful for estimating the treatment effect. To eliminate those size distortions, we propose a modified t-statistic that uses a null-restricted version of the standard error of the FRD estimator. Simple and asymptotically valid confidence sets for the treatment effect can be also constructed using this null-restricted standard error. An extension to testing for constancy of the regression discontinuity effect across covariates is also discussed. Supplementary materials for this article are available online.     

Deathbed visions from the Republic of Moldova: a content analysis of family observations

This is an interview-based study of 102 families and their observations of the last weeks and days of a dying family member. Forty-one families reported hearing about "visions," "hallucinations," or "dreams" from their dying loved one before their death. Of these 41 mixed cases, 37 cases demonstrated classic features of deathbed visions-reports of seeing dead relatives or friends communicating to the dying person. This article reports a content analysis of these 37 cases in order to identify the major psychosocial themes that seem to be conveyed by these kinds of experiences. Six major themes are identified. These themes are: support, comfort, companionship, reunion, prognosis, and choice and control. Implications of these themes are discussed in relation to their role in providing significant support for the psychological morale and social well being of dying people.