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R G Downey

Publications and source records attributed to R G Downey.

5 recordsLinked to original sources
PubMed1995

Parameterized complexity analysis in computational biology.

Many computational problems in biology involve parameters for which a small range of values cover important applications. We argue that for many problems in this setting, parameterized computational complexity rather than NP-completeness is the appropriate tool for studying apparent intractability. At issue in the theory of parameterized complexity is whether a problem can be solved in time O(n alpha) for each fixed parameter value, where alpha is a constant independent of the parameter. In addition to surveying this complexity framework, we describe a new result for the Longest Common Subsequence problem. In particular, we show that the problem is hard for W[t] for all t when parameterized by the number of strings and the size of the alphabet. Lower bounds on the complexity of this basic combinatorial problem imply lower bounds on more general sequence alignment and consensus discovery problems. We also describe a number of open problems pertaining to the parameterized complexity of problems in computational biology where small parameter values are important.

Algorithms↗
PubMed1985

Dimensions of managerial work in hospital dietetic services.

The objective of this study was to identify underlying dimensions of the managerial work of hospital dietetic services professional staff. A survey instrument was developed on the basis of Mintzberg's role theory of management. Respondents were asked to rate 80 activity statements on the relative importance and time demand of each. Principal component analysis was used to determine whether items could be conceptualized meaningfully by a smaller number of components capable of accounting for interrelationships. Reliabilities and correlations were computed for the resulting managerial factor scores. Six factors were identified from the importance ratings: Upper Management, Interaction with Subordinates, Outside Activities, Quality Assurance, Communication Activities, and Personnel Activities. Similar dimensions were identified from the time-demand ratings. Findings from this analysis suggest that managers in different functional specialties and at various organizational levels tend to vary in their allocation of time and to stress different roles. As a person rises on the administrative ladder of responsibility, concentration on extramural affairs and involvement in planning are greater, and concern with specific operational problems decreases. The importance of conceptual skills was especially evident in upper administrative positions, as was the critical need for intergroup skills.

Dietary Services↗