Parameterized Approximation Schemes using Graph Widths

Combining the techniques of approximation algorithms and parameterized complexity has long been considered a promising research area, but relatively few results are currently known. In this paper we study the parameterized approximability of a number of problems which are known to be hard to solve exactly when parameterized by treewidth or clique-width. Our main contribution is to present a natural randomized rounding technique that extends well-known ideas and can be used for both of these widths. Applying this very generic technique we obtain approximation schemes for a number of problems, evading both polynomial-time inapproximability and parameterized intractability bounds

Development of an Internet-based Data Network for the Control of Salmonella in the pork production chain

To promote food safety and to increase sales of pig meat, a salmonella control program was initiated in Lower Saxony. Farm specific data on salmonella prevalence in finishing pigs are collected at the slaughterhouse. The collection of a representative sample size for each farm on a yearly basis has to be organized and the prevalence of salmonella in each finishing herd has to be calculated. The aim is to control the delivery of pigs to the slaughterhouse depending on the salmonella status of the finishing herds. Pigs originating from herds with a low salmonella prevalence will be slaughtered prior to pigs with a higher or unknown prevalence

Sports Participation, Social Networks, and Sexual Violence Perpetration

Adolescent sexual violence (SV), which includes non-contact verbal sexual harassment (SH) and forced sexual contact (FSC), is a significant public health problem with long-term impacts on health and well-being. Understanding how sports participation is linked to SV can inform prevention efforts; however, the current literature is unclear about the nature of this association. Using data from 20 high schools, we investigate whether athletes in certain sports are at higher risk of SH and FSC perpetration than either other athletes or sports non-participants, and whether the risk is moderated by gender, dismissiveness of SV, or substance use intentions. We also utilize social network data to explore the role of relationships with peers and trusted adults to attenuate SH and FSC perpetration. Second, we incorporate characteristics of friends to further examine the role and composition of peer groups in the association between sports participation and perpetration of SH and FSC. Findings revealed a bivariate association between sport contact level and SH perpetration, but not FSC, and the association disappeared after adjusting for other covariates. Most prominently, dismissiveness of SV, intentions to use substances, and prior perpetration had the strongest association with perpetration regardless of sport contact level. Results also provided some support for the influence of peers and trusted adults in the sports context. Notably, the percentage of friends who perpetrated FSC and the percentage of friends who play a low-contact sport were positively associated with FSC perpetration, and the percentage of friends who play a high-contact sport was positively associated with SH perpetration. The paper concludes with a discussion of the sports context as an important venue for comprehensive prevention efforts, including a focus on changing norms around adolescent SV and substance use

A Critical Review of Anti‐Bullying Programs in North American Elementary Schools

BACKGROUNDBullying behavior is a concern among school‐aged youth and anti‐bullying programs have been implemented in schools throughout North America. Most anti‐bullying programs are delivered to adolescent youth because antisocial‐aggressive behaviors are typically associated with this developmental stage. This paper is a review of empirically evaluated school‐based bullying prevention and intervention programs in North American elementary schools.METHODSWe conducted a systematic, critical review of bullying prevention programming. Data were analyzed to determine the study method, intervention components, measurement of bullying, aggression, or peer victimization, outcomes measured, and results.RESULTSOur review resulted in the identification of 10 interventions aimed at youth in grades K‐6 enrolled in North American elementary schools. Effective intervention strategies targeted a variety of bullying behaviors using diverse mechanisms and included a school—and community‐wide approach. Direct outcomes of the reviewed evaluations were centered on bullying, aggression, and victimization. Indirect outcomes of review evaluations included strategies for bystanders, school achievement, perceived school safety, and knowledge or attitudes about bullying.CONCLUSIONSRecommendations for promising practices in effective bullying intervention programming are offered. The review concludes with suggestions for supporting school health staff and in‐service teachers drawn from the body of research, and offers direction for future study.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151360/1/josh12814_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151360/2/josh12814.pd

Parameterized Edge Hamiltonicity

We study the parameterized complexity of the classical Edge Hamiltonian Path problem and give several fixed-parameter tractability results. First, we settle an open question of Demaine et al. by showing that Edge Hamiltonian Path is FPT parameterized by vertex cover, and that it also admits a cubic kernel. We then show fixed-parameter tractability even for a generalization of the problem to arbitrary hypergraphs, parameterized by the size of a (supplied) hitting set. We also consider the problem parameterized by treewidth or clique-width. Surprisingly, we show that the problem is FPT for both of these standard parameters, in contrast to its vertex version, which is W-hard for clique-width. Our technique, which may be of independent interest, relies on a structural characterization of clique-width in terms of treewidth and complete bipartite subgraphs due to Gurski and Wanke

Neighborhood predictors of bullying perpetration and victimization trajectories among South Korean adolescents

AimsThis study examined latent trajectories of bullying perpetration and victimization, and identified neighborhood antecedents of these trajectories among South Korean adolescents.MethodsNationally representative individual‐level data from waves 2 to 6 (middle school to high school) of the Korean Children and Youth Panel Survey were merged with neighborhood‐level data drawn from the Korean Census and the Korean Ministry of Education. Latent class growth analysis (N = 2,178) and logistic regression were conducted (N = 2,021).ResultsThree unique trajectories of bullying experience—low‐risk (80.8%), transient (13.3%), high‐risk (5.9%)—were identified. Neighborhood factors (e.g., public assistance receipt, marital status, official bullying incidents, collective efficacy) predicted these distinct developmental paths.ConclusionJoint trajectories of perpetration and victimization can inform service or policy decisions as each developmental path may represent unique experiences for youth in need of specific resources for treatment or intervention. Neighborhood indicators are important predictors of developmental trajectories of bullying experience among adolescents.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151342/1/jcop22226_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151342/2/jcop22226.pd

Well-quasi-ordering versus clique-width : new results on bigenic classes.

Daligault, Rao and Thomassé conjectured that if a hereditary class of graphs is well-quasi-ordered by the induced subgraph relation then it has bounded clique-width. Lozin, Razgon and Zamaraev recently showed that this conjecture is not true for infinitely defined classes. For finitely defined classes the conjecture is still open. It is known to hold for classes of graphs defined by a single forbidden induced subgraph H, as such graphs are well-quasi-ordered and are of bounded clique-width if and only if H is an induced subgraph of P4P4. For bigenic classes of graphs i.e. ones defined by two forbidden induced subgraphs there are several open cases in both classifications. We reduce the number of open cases for well-quasi-orderability of such classes from 12 to 9. Our results agree with the conjecture and imply that there are only two remaining cases to verify for bigenic classes

Maximizing Happiness in Graphs of Bounded Clique-Width

Clique-width is one of the most important parameters that describes structural complexity of a graph. Probably, only treewidth is more studied graph width parameter. In this paper we study how clique-width influences the complexity of the Maximum Happy Vertices (MHV) and Maximum Happy Edges (MHE) problems. We answer a question of Choudhari and Reddy '18 about parameterization by the distance to threshold graphs by showing that MHE is NP-complete on threshold graphs. Hence, it is not even in XP when parameterized by clique-width, since threshold graphs have clique-width at most two. As a complement for this result we provide a $n^{\mathcal{O}(\ell \cdot \operatorname{cw})}$ algorithm for MHE, where $\ell$ is the number of colors and $\operatorname{cw}$ is the clique-width of the input graph. We also construct an FPT algorithm for MHV with running time $\mathcal{O}^*((\ell+1)^{\mathcal{O}(\operatorname{cw})})$, where $\ell$ is the number of colors in the input. Additionally, we show $\mathcal{O}(\ell n^2)$ algorithm for MHV on interval graphs.Comment: Accepted to LATIN 202