Hardness and algorithms for rainbow connection

An edge-colored graph G is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection of a connected graph G, denoted rc(G), is the smallest number of colors that are needed in order to make G rainbow connected. In the first result of this paper we prove that computing rc(G) is NP-Hard solving an open problem from Caro et al. (Electron. J. Comb. 15, 2008, Paper R57). In fact, we prove that it is already NP-Complete to decide if rc(G)=2, and also that it is NP-Complete to decide whether a given edge-colored (with an unbounded number of colors) graph is rainbow connected. On the positive side, we prove that for every ε>0, a connected graph with minimum degree at least ε n has bounded rainbow connection, where the bound depends only on ε, and a corresponding coloring can be constructed in polynomial time. Additional non-trivial upper bounds, as well as open problems and conjectures are also presented.     

Methods to Explore Uncertainty and Bias Introduced by Job Exposure Matrices

Job exposure matrices (JEMs) are used to measure exposures based on information about particular jobs and tasks. JEMs are especially useful when individual exposure data cannot be obtained. Nonetheless, there may be other workplace exposures associated with the study disease that are not measured in available JEMs. When these exposures are also associated with the exposures measured in the JEM, biases due to uncontrolled confounding will be introduced. Furthermore, individual exposures differ from JEM measurements due to differences in job conditions and worker practices. Uncertainty may also be present at the assessor level since exposure information for each job may be imprecise or incomplete. Assigning individuals a fixed exposure determined by the JEM ignores these uncertainty sources. We examine the uncertainty displayed by bias analyses in a study of occupational electric shocks, occupational magnetic fields, and amyotrophic lateral sclerosis.     

Interdisciplinary technology assessment of service robots: the psychological/work science perspective

The article sheds light on psychological and work science aspects of the design and utilization of service robots. An initial presentation of the characteristics of man?Crobot interaction is followed by a discussion of the principles of the division of functions between human beings and robots in service area work systems. The following aspects are to be considered: (1) the organisation of societal work (such as the different employment and professional profiles of service employees), (2) the work tasks to be performed by humans and robots (such as handling, monitoring or decision-making tasks), (3) the possibilities and the limitations of realizing such tasks by means of information technology (depending, for example, on the motoric capabilities, perception and cognition of the robot). Consideration of these three design perspectives gives rise to criteria of usability. Current debate focuses on the (work science) principles of man?Cmachine communication, though in future these should be supplemented with robot-specific criteria such as "motoric capabilities" or "relationship quality." The article concludes by advocating the convergence and combination of work science criteria with ideas drawn from participative design approaches in the development and utilization of service robots.     

Dynamic effects of financial intermediation over the business cycle

This paper provides a empirical evidence that the financial intermediation disturbances can generate business cycles. We examine three countries whose financial sectors are fully developed but quite distinct in their institutional and regulatory circumstances; thus, we can infer whether financial intermediation disturbances differ across dissimilar financial environments. We find that the dynamic responses of output to financial intermediation shocks exhibit similar patterns in all cases studied. However, the various institutional and regulatory circumstances have generated different propagation mechanisms transmitting the financial disturbance to output in ways that lead the magnitudes of the responses to deviate across economies.