Exact procedures for solving the discrete ordered median problem

The discrete ordered median problem (DOMP) integrates classical discrete location problems, such as the N-median, N-center and Uncapacitated Facility Location problems. It was introduced by Nickel (In: Fleischmann B, Lasch R, Derigs U, Domschke W, Rieder U, editors. Operations Research Proceedings 2000, Berlin: Springer, 2001. p. 71–76), who formulated it as both a nonlinear and a linear integer program. We propose an alternative integer linear programming formulation for the DOMP, discuss relationships between both integer linear programming formulations, and show how properties of optimal solutions can be used to strengthen these formulations. Moreover, we present a specific branch and bound procedure to solve the DOMP more efficiently. We test the integer linear programming formulations and this branch and bound method computationally on randomly generated test problems.     

Computational comparisons of different formulations for the Stackelberg minimum spanning tree game

Let be a given graph whose edge set is partitioned into a set R of red edges and a set B of blue edges, and assume that red edges are weighted and contain a spanning tree of G. Then, the Stackelberg minimum spanning tree game (StackMST) is that of pricing (i.e., weighting) the blue edges in such a way that the total weight of the blue edges selected in a minimum spanning tree of the resulting graph is maximized. In this paper, we present different new mathematical programming formulations for the StackMST based on the properties of the minimum spanning tree problem and the bilevel optimization. We establish a theoretical and empirical comparison between these new formulations that are able to solve random instances of 20–70 nodes. We also test our models on instances in the literature, outperforming previous results.     

Effect of wheat bran in treatment of chronic nonorganic constipation. A double-blind controlled trial

An experiment was conducted to define the seasonal changes in LH secretion in ovariectomized does with oestrogen implants and the effect of immunization against melatonin. Fifteen mature Australian cashmere goats were ovariectomized and given either no further treatment or one or two implants containing oestradiol; another similar group of 15 does were immunized against melatonin before ovariectomy and oestrogen treatment. LH concentrations and livemasses were recorded every week for 2 years. Livemasses of both groups showed a distinct seasonal pattern with a summer maximum and a winter minimum irrespective of treatment. LH concentrations also showed distinct seasonal patterns with a significant interaction between the number of implants and the time of the year. In the nonimmunized does, the presence of a constant low dose of oestrogen (one implant) resulted in low concentrations of LH except from May to August, the normal period of spontaneous ovulatory activity in intact does. In contrast, nonimmunized does receiving a high dose of oestrogen (two implants) showed a rise in LH concentrations in February, and concentrations remained high until August. Immunization against melatonin abolished this differential LH secretory pattern, and both doses of oestrogen were associated with a short period of high LH concentration between May and September. These results indicate that a negative feedback effect of oestrogen results in low LH secretion for most of the year and that hypothalamic sensitivity to LH decreases for only a short period between May and August.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of gallium-67 citrate in salivary glands following radiation therapy

Gallium-67 citrate was found to localize in the salivary glands of eight patients after therapeutic doses of radiation to a treatment field including the glands. In two patients, autopsy evidence to the effect that no primary disease was present to explain such uptake was obtained. In another two patients the abnormal uptake was not observed on follow-up. The recognition that radiation sialadenitis is a potential cause of false-positive gallium scintiscans is important in their interpretation.     

Kinetic evaluation of the propranolol-quinidine combination

The kinetics of quinidine and propranolol, administered singly and in combination, were evaluated in 5 healthy subjects. The orally administered doses resulted in plasma concentrations within the therapeutic range. For each drug the average steady-state plasma concentration, maximal plasma concentration, and time of maximum plasma concentration were not altered by the presence of the other drugs. This study shows no kinetic interaction between quinidine and propranolol in normal subjects.     

Heritable chromosome rearrangements induced in rat spermatids by x-irradiation

The induction of reciprocal translocations by an exposure of rat spermatids to X-irradiation has been studied by cytological examination of dividing spermatocytes of F1 sons. The incidence of F1 translocated males was found to vary from 7.89% after exposure to 125 R to 22.44% after exposure to 500 R.     

A generalized model of equality measures in network location problems

In this paper, the concept of the ordered weighted averaging operator is applied to define a model which unifies and generalizes several inequality measures. For a location x, the value of the new objective function is the ordered weighted average of the absolute deviations from the average distance from the facilities to the location x. Several kinds of networks are studied: cyclic, tree and path networks and, for each of them, the properties of the objective function are analyzed in order to identify a finite dominating set for optimal locations. Polynomial-time algorithms are proposed for these problems, and the corresponding complexity is discussed.     

Symmetry considerations in CdSe nanocrystals

Semiconductor nanocrystals or quantum dots show a wide range of physical properties depending on their size or shape. In this paper, we show that symmetry is also an important characteristic that can lead to different electronic and optical properties. We use pseudopotential density-functional theory, within a real space approach, and address the sensitivity of electronic and optical properties with respect to the symmetry point groups associated to CdSe nanocrystals.