"Almost-stable" matchings in the Hospitals / Residents problem with Couples

The Hospitals / Residents problem with Couples (hrc) models the allocation of intending junior doctors to hospitals where couples are allowed to submit joint preference lists over pairs of (typically geographically close) hospitals. It is known that a stable matching need not exist, so we consider min bp hrc, the problem of finding a matching that admits the minimum number of blocking pairs (i.e., is “as stable as possible”). We show that this problem is NP-hard and difficult to approximate even in the highly restricted case that each couple finds only one hospital pair acceptable. However if we further assume that the preference list of each single resident and hospital is of length at most 2, we give a polynomial-time algorithm for this case. We then present the first Integer Programming (IP) and Constraint Programming (CP) models for min bp hrc. Finally, we discuss an empirical evaluation of these models applied to randomly-generated instances of min bp hrc. We find that on average, the CP model is about 1.15 times faster than the IP model, and when presolving is applied to the CP model, it is on average 8.14 times faster. We further observe that the number of blocking pairs admitted by a solution is very small, i.e., usually at most 1, and never more than 2, for the (28,000) instances considered

Assessing alexithymia in adolescents: Psychometric properties of the Perth alexithymia questionnaire in high school students

Conceptually, alexithymia is a key transdiagnostic risk factor for the development of numerous psychopathologies across the lifespan. However, to date, most alexithymia research has focused on adults, with adolescent work limited by a lack of validated age-appropriate assessment tools. Recently, the Perth Alexithymia Questionnaire (PAQ) was introduced to enhance the comprehensiveness of alexithymia assessments, but its psychometric properties have only been tested in adults. In this study, we address this by examining the psychometric properties of the PAQ in a sample of English-speaking high school students (N = 225, aged 11 to 18), and use the PAQ to further establish the structure of the alexithymia construct in adolescents. Confirmatory factor analysis revealed that all PAQ items conformed well to the expected factor structure, supporting that the PAQ was measuring a coherent multidimensional construct, consistent with the attention-appraisal model of alexithymia. All subscale and composite scores had good to excellent internal consistency (a range =.83 to.95) and correlated in expected ways with other emotion measures. Together, these findings suggest that the multidimensional structure of the alexithymia construct manifests similarly in adolescents and adults, and that the PAQ is a valid and reliable measure of alexithymia in adolescents

Possible Observational Criteria for Distinguishing Brown Dwarfs from Planets

The difference in formation process between binary stars and planetary systems is reflected in their composition as well as their orbital architecture, particularly orbital eccentricity as a function of orbital period. It is suggested here that this difference can be used as an observational criterion to distinguish between brown dwarfs and planets. Application of the orbital criterion suggests that with three possible exceptions, all of the recently-discovered substellar companions discovered to date may be brown dwarfs and not planets. These criterion may be used as a guide for interpretation of the nature of sub-stellar mass companions to stars in the future.Comment: LaTeX, 11 pages including 2 figures, accepted for publication in the Astrophysical Journal Letter

Controlling the configuration space topology of mechanisms

Linkages are mechanical devices constructed from rigid bars and freely rotating joints studied both for their utility in engineering and as mathematical idealizations in a number of physical systems. Recently, there has been a resurgence of interest in designing linkages to perform certain tasks from the physics community. We describe a method to design the topology of the configuration space of a linkage by first identifying the manifold of critical points, then perturbing around such critical configurations. We then demonstrate our procedure by designing a mechanism to gate the propagation of a soliton in a Kane-Lubensky chain of interconnected rotors

The effects of dietary fish oil on hepatic high density and low density lipoprotein receptor activities in the rat

AbstractRats were fed either a standard ration diet or that diet supplemented with 8% by wt of a marine fish oil or safflower oil. After 10 days, plasma triacylglycerols, total cholesterol, high density lipoprotein (HDL) cholesterol, hepatic cholesterol and fatty acid synthesis and hepatic low density lipoprotein (LDL) receptor activity were significantly depressed while HDL receptor activity was significantly increased in rats fed fish oil. Fish oil-induced effects on cholesterol metabolism in the rat therefore include reciprocal changes in the activities of hepatic LDL and HDL receptors

Dimensions 1994-95

This magazine is a lab publication of journalism students enrolled in Publications Production at Des Moines Area Community College / Ankeny Campus.https://openspace.dmacc.edu/dimensions/1000/thumbnail.jp