On Structural Parameterizations of Hitting Set: Hitting Paths in Graphs Using 2-SAT

Hitting Set is a classic problem in combinatorial optimization. Its input consists of a set system F over a finite universe U and an integer t; the question is whether there is a set of t elements that intersects every set in F. The Hitting Set problem parameterized by the size of the solution is a well-known W[2]-complete problem in parameterized complexity theory. In this paper we investigate the complexity of Hitting Set under various structural parameterizations of the input. Our starting point is the folklore result that Hitting Set is polynomial-time solvable if there is a tree T on vertex set U such that the sets in F induce connected subtrees of T. We consider the case that there is a treelike graph with vertex set U such that the sets in F induce connected subgraphs; the parameter of the problem is a measure of how treelike the graph is. Our main positive result is an algorithm that, given a graph G with cyclomatic number k, a collection P of simple paths in G, and an integer t, determines in time 2^{5k} (|G| +|P|)^O(1) whether there is a vertex set of size t that hits all paths in P. It is based on a connection to the 2-SAT problem in multiple valued logic. For other parameterizations we derive W[1]-hardness and para-NP-completeness results.Comment: Presented at the 41st International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2015. (The statement of Lemma 4 was corrected in this update.

The Labour Government, the Treasury and the £6 pay policy of July 1975

The 1974-79 Labour Government was elected in a climate of opinion that was fiercely opposed to government intervention in the wage determination process, and was committed to the principles of free collective bargaining in its manifestoes. However, by December 1974 the Treasury was advocating a formal incomes policy, and by July 1975 the government had introduced a £6 flat rate pay norm. With reference to archival sources, the paper demonstrates that TUC and Labour Party opposition to incomes policy was reconciled with the Treasury's advocacy by limiting the Bank of England‟s intervention in the foreign exchange market when sterling came under pressure. This both helped to achieve the Treasury's objective of improving the competitiveness of British industry, and acted as a catalyst for the introduction of incomes policy because the slide could be attributed to a lack of market confidence in British counter-inflation policy

Profiling of Glycan Receptors for Minute Virus of Mice in Permissive Cell Lines Towards Understanding the Mechanism of Cell Recognition

The recognition of sialic acids by two strains of minute virus of mice (MVM), MVMp (prototype) and MVMi (immunosuppressive), is an essential requirement for successful infection. To understand the potential for recognition of different modifications of sialic acid by MVM, three types of capsids, virus-like particles, wild type empty (no DNA) capsids, and DNA packaged virions, were screened on a sialylated glycan microarray (SGM). Both viruses demonstrated a preference for binding to 9-O-methylated sialic acid derivatives, while MVMp showed additional binding to 9-O-acetylated and 9-O-lactoylated sialic acid derivatives, indicating recognition differences. The glycans recognized contained a type-2 Galβ1-4GlcNAc motif (Neu5Acα2-3Galβ1-4GlcNAc or 3′SIA-LN) and were biantennary complex-type N-glycans with the exception of one. To correlate the recognition of the 3′SIA-LN glycan motif as well as the biantennary structures to their natural expression in cell lines permissive for MVMp, MVMi, or both strains, the N- and O-glycans, and polar glycolipids present in three cell lines used for in vitro studies, A9 fibroblasts, EL4 T lymphocytes, and the SV40 transformed NB324K cells, were analyzed by MALDI-TOF/TOF mass spectrometry. The cells showed an abundance of the sialylated glycan motifs recognized by the viruses in the SGM and previous glycan microarrays supporting their role in cellular recognition by MVM. Significantly, the NB324K showed fucosylation at the non-reducing end of their biantennary glycans, suggesting that recognition of these cells is possibly mediated by the Lewis X motif as in 3′SIA-LeX identified in a previous glycan microarray screen

Occupational safety and health training in DOE

Occupational safety and health (OSH) policies, programs and activities within DOE are changing rapidly. In June 1989, Secretary of Energy Watkins launched his ``Ten Point Initiative`` charting a new course for the Department of Energy (DOE) toward full accountability in the areas of environment, safety and health. Full compliance with Occupational Safety and Health Administration (OSHA) standards is now mandatory within the Department. Independent ``Tiger Teams`` are performing safety and health compliance assessments at DOE facilities to identify OSH deficiencies. A recent extensive OSHA audit of DOE OSH programs and related activities has resulted in additional changes in DOE OSH requirements. These changes coupled with those pending in the proposed OSHA Reform Act, have had, and will continue to have, a tremendous impact on the roles and responsibilities each of us has within DOE, particularly in the area of OSH training. This presentation focuses on the specific implications these changes have relating to OSH Training Requirements

The Dynamics of Poor Systems of Galaxies

We assemble and observe a sample of poor galaxy systems that is suitable for testing N-body simulations of hierarchical clustering (Navarro, Frenk, & White 1997; NFW) and other dynamical halo models (e.g., Hernquist 1990). We (1) determine the parameters of the density profile rho(r) and the velocity dispersion profile sigma(R), (2) separate emission-line galaxies from absorption-line galaxies, examining the model parameters and as a function of spectroscopic type, and (3) for the best-behaved subsample, constrain the velocity anisotropy parameter, beta, which determines the shapes of the galaxy orbits. The NFW universal profile and the Hernquist (1990) model both provide good descriptions of the spatial data. In most cases an isothermal sphere is ruled out. Systems with declining sigma(R) are well-matched by theoretical profiles in which the star-forming galaxies have predominantly radial orbits (beta > 0); many of these galaxies are probably falling in for the first time. There is significant evidence for spatial segregation of the spectroscopic classes regardless of sigma(R).Comment: 36 pages, 20 figures, and 5 tables. To appear in the Astrophysical Journa

Generalized Electromagnetic fields in Chiral Medium

The time dependent Dirac-Maxwell's Equations in presence of electric and magnetic sources are written in chiral media and the solutions for the classical problem are obtained in unique simple and consistent manner. The quaternion reformulation of generalized electromagnetic fields in chiral media has also been developed in compact, simple and consistent manner