On the Complexity of Constructing Evolutionary Trees

In this paper we study a few important tree optimization problems with applications to computational biology. These problems ask for trees that are consistent with an as large part of the given data as possible. We show that the maximum homeomorphic agreement subtree problem cannot be approximated within a factor of , where N is the input size, for any 0 in polynomial time unless P = NP, even if all the given trees are of height 2. On the other hand, we present an O(N log N)-time heuristic for the restriction of this problem to instances with O(1) trees of height O(1) yielding solutions within a constant factor of the optimum. We prove that the maximum inferred consensus tree problem is NP-complete, and provide a simple, fast heuristic for it yielding solutions within one third of the optimum. We also present a more specialized polynomial-time heuristic for the maximum inferred local consensus tree problem.     

Quadratic estimation in mixed linear models with two variance components

Explicit expressions for Bayes invariant quadratic estimates, biased and unbiased, are presented and proved to cover the entire class of admissible estimates in the considered classes. An unbalanced genetic model is studied for demonstration.     

Turkey's physicians' attitudes toward euthanasia: a brief research report

Euthanasia and assisted suicide are subject to an ongoing debate and discussed with various aspects. Because physicians are in a profession closely related to euthanasia, their attitudes toward this subject are significant. Thus, research intending to explore their opinions is carried out in many countries. In this study, opinions of the physicians regarding euthanasia's definition, contents, legal aspects, and acceptable conditions for its application are addressed. The questionnaire was given to 949 physicians, more than 1% of the total working in Turkey. Of the physicians who participated in the study, 49.9% agreed with the opinion that euthanasia should be legal in certain circumstances. In addition, 19% had come across a euthanasia request and the majority of physicians (55.9%) believed that euthanasia is applied secretly in the country despite the prohibitory legislation. In conclusion, the authors infer from the study itself and believe that euthanasia should be legal in certain circumstances and that the subject, which is not in the agenda of the Turkish population, should continue to be examined.     

Room assignment-rent division: A market approach

A group of friends consider renting a house but they shall first agree on how to allocate its rooms and share the rent. We propose an auction mechanism for room assignment-rent division problems which mimics the market mechanism. Our auction mechanism is efficient, envy-free, individually-rational and it yields a non-negative price to each room whenever that is possible with envy-freeness.We would like to thank seminar participants at Barcelona, Boston College, Duke, Koç, Málaga, MIT, Michigan, NYU, conference participants at the First Brazilian Workshop of Game Theory Society (Sao Paulo 2002), SED 2002-Conference on Economic Design (New York City 2002), The Sixth International Meeting of the Society for Social Choice and Welfare (Pasadena 2002), an anonymous referee for their comments and Ahmet Alkan, Selçuk Karabati, Bari Tan, nsan Tunali for insightful discussions. Sönmez gratefully acknowledges the research support of KoçBank via the KoçBank scholar program and Turkish Academy of Sciences in the framework of the Young Scientist Award Program via grant TS/TÜBA-GEBP/2002-1-19. Any errors are our own responsibility.     

Effects of multicomponent training on functional fitness in older adults

The purpose of this study was to evaluate the effects of a 9-week supervised multicomponent exercise program on functional fitness and body composition in independent older adults. Forty-two adults age 60-86 years were randomly assigned to an exercise or a control group and were evaluated before and after training. The training program consisted of 3 sessions of walking, strengthening, and flexibility exercises per week. The multicomponent training program resulted in significant (p < .005) improvements on the chair stand, arm curl, 6-min walk, and up-and-go tests. The findings of this study indicate that a 9-week training program increased upper and lower body strength, aerobic endurance, and agility/dynamic balance in older adults. The most affected components of functional fitness were lower body strength and aerobic endurance. There was no effect of the 9-week training on body composition.     

Besser entscheiden im Team — aber wie?

Investment committees of banks, pension funds or investment clubs meet regularly. The members decide together about the allocation and the timing of their own assets or their customers assets. This article will point out some pitfalls and chances that are typical in this decision making process. Especial focus is set on financial psychological aspects with regards to information processing and decision making processes. At the end of the article the author will indicate a sustainable way to improve the quality of team decisions.