A parameterized perspective on packing paths of length two

We study (vertex-disjoint) packings of paths of length two (i.e., of P ₂’s) in graphs under a parameterized perspective. Starting from a maximal P ₂-packing ℘ of size j we use extremal combinatorial arguments for determining how many vertices of ℘ appear in some P ₂-packing of size (j+1) (if such a packing exists). We prove that one can ‘reuse’ 2.5j vertices. We also show that this bound is asymptotically sharp. Based on a WIN-WIN approach, we build an algorithm which decides, given a graph, if a P ₂-packing of size at least k exists in time O^*(2.448^3k)\mathcal{O}^{*}(2.448^{3k}) .     

A short proof of a result on a Vizing-like problem for integer total domination

In this note, we provide a short proof of a recent result on a Vizing-like problem for integer total domination in graphs given by Li and Hou (J. Comb. Optim., 2008).     

The internal migration patterns of the foreign-born and native-born populations in the United States: 1975-80 and 1985-90

"The focus of this article is on an examination of the influence of birthplace on the internal migration and spatial redistribution patterns of the foreign-born and native-born populations in the United States during the 1975-80 and 1985-90 periods. The analyses presented here consider the following principal questions: (1) What are the internal migration patterns of the foreign-born population in the United States, and how do they differ from those of the native-born population? (2) How do the relocation choices of various birthplace-specific foreign-born and native-born subpopulations differ from each other? (3) Are the internal migration patterns generating an increased or a decreased geographical concentration of such birthplace-specific subgroups?"     

Graphs with large paired-domination number

In this paper, we continue the study of paired-domination in graphs introduced by Haynes and Slater (1998) Networks 32: 199–206. A paired-dominating set of a graph G with no isolated vertex is a dominating set of vertices whose induced subgraph has a perfect matching. The paired-domination number of G, denoted by , is the minimum cardinality of a paired-dominating set of G. Let G be a connected graph of order n with minimum degree at least two. Haynes and Slater (1998) Networks 32: 199–206, showed that if n ≥ 6, then . In this paper, we show that there are exactly ten graphs that achieve equality in this bound. For n ≥ 14, we show that and we characterize the (infinite family of) graphs that achieve equality in this bound.Research supported in part by the South African National Research Foundation and the University of KwaZulu-Natal.     

School enrolment and mothers’ labor supply: evidence from a regression discontinuity approach

We analyze the impact on maternal employment of a universal school reform in Norway which lowered the school starting age from seven to six. We use a regression discontinuity approach exploiting exogenous variation in the compulsory school enrollment rule caused by the reform. Our results reveal positive short-term effects on labor supply (approximately five percentage points) and on earnings (about 12600/1350 NOK/Euro). Subgroup analyses show that the positive effects are much stronger for mothers with low wage potential, a group of mothers that were less likely to use formal childcare prior to the reform. The positive effects for this subgroup of mothers suggest that expanding child-care can be an effective tool for increasing labor supply of mothers who previously had relatively low labor market earnings potential.     

Firm-level indicators of instrumental and political CSR processes – A multiple case study

Recent studies have been increasingly distinguishing between instrumental and political approaches to corporate social responsibility (CSR). However, few studies have explored the firm-level processes generating these types of CSR engagements. Using Basu and Palazzo’s (2008) proposition to model CSR as a process of sensemaking, we suggest that multinational enterprises use different processes in developing capabilities around instrumental and political CSR. Our qualitative multiple case–study analysis is based on data from 42 in-depth, semi-structured interviews with 27 senior managers from British American Tobacco, Nestlé, and Hewlett Packard. Our findings from the three cases indicate that instrumental and political CSR are characterised by different sensemaking processes. We also find evidence for overlapping of processes between instrumental and political CSR.     

Theoretische und statistische Modellierung von Cross-Pressures in Kontextanalysen

Cross-pressures can be defined as individually perceived social pressure that results from heterogeneity in the social context, mainly due to conflicting social expectations of relevant social actors. In this paper we discuss the theoretical position of “cross-pressures” in the structural-individualist paradigm and present methods for modeling cross-pressures in multilevel regression models. We argue that cross pressures form a specific class of context effects, that is macro-micro links, and sketch a reconstruction as part of the problem of defining the social situation in the Model of Frame Selection. The theoretical model implies that empirical applications of the concept would ideally use multiplicative terms for the specification of cross-level interactions in multilevel models. Modeling random slopes and context fixed-effects the interaction can be identified empirically. As an example we analyze the relation between postmaterialism and environmental concern, moderated by national wealth using WVS data. Our results indicate that postmaterialism and environmental concern form an integrated value cluster in wealthy societies, but are separate constructs in poorer societies.     

„Gekommen,um zu bleiben“ – eine Analyse des Zusammenhangs zwischen personen- und kontextbezogenen Faktoren und Studienerfolg in Studiengängen der öffentlichen Verwaltung

The present study aims to investigate impact factors on study success and turnover intentions for students from different fields of public administration and management. The empirical analysis focuses on interrelations between individual (e.?g., personality, achievement satisfaction, self-efficacy) and contextual factors (procedural justice, social integration) and general study satisfaction and the intention to leave the university. The sample consisted of N?=?147 students from police and general public administration. The results indicated that there is an empirical evidence for the relevance of realistic academic and job expectations, individal personality facets, as well as for perceived justice and social integration of the students related to the discipline. Regression models showed that the expected person-job-fit predicted aspects of study satisfaction and turnover intention. In addition, individual and contextual factors moderated the interrelation, however, differently for the evaluated disciplines. Implications for students and for the design of different study programs as well as for a target group oriented communication are discussed.