The Stackelberg Minimum Spanning Tree Game

We consider a one-round two-player network pricing game, the Stackelberg Minimum Spanning Tree game or StackMST. The game is played on a graph (representing a network), whose edges are colored either red or blue, and where the red edges have a given fixed cost (representing the competitor??s prices). The first player chooses an assignment of prices to the blue edges, and the second player then buys the cheapest possible minimum spanning tree, using any combination of red and blue edges. The goal of the first player is to maximize the total price of purchased blue edges. This game is the minimum spanning tree analog of the well-studied Stackelberg shortest-path game. We analyze the complexity and approximability of the first player??s best strategy in StackMST. In particular, we prove that the problem is APX-hard even if there are only two different red costs, and give an approximation algorithm whose approximation ratio is at most min?{k,1+ln?b,1+ln?W}, where k is the number of distinct red costs, b is the number of blue edges, and W is the maximum ratio between red costs. We also give a natural integer linear programming formulation of the problem, and show that the integrality gap of the fractional relaxation asymptotically matches the approximation guarantee of our algorithm.     

Length conservation and speed concepts: Organizational disequilibrium training between concepts.

Administered training to Ss at varying levels of cognitive organization. Ss were 60 middle-class Israeli 6-7 yr olds. The training condition exploited structural mix between operational length and intuitive speed concepts, such that Ss successively alternated partial structures underlying these concepts. Findings were that (a) training was effective for operational speed concept acquisition among Ss with structural mix; (b) training was not effective for Ss without structural mix; (c) those who acquired the operational speed concept also acquired operational reasoning for the concept of movement; and (d) all Ss who employed an integration strategy during training became operational for speed on the posttest, while none who used other strategies acquired operational reasoning for the speed concept. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An analysis of rates of polypeptide chain elongation in avian liver explants following in vivo estrogen treatment. I. Determination of average rates of polypeptide chain elongation

Average rates of polypeptide chain elongation have been determined in cockerel liver explants on 4 successive days following an in vivo injection of 17 beta-estradiol. Incorporation of [3H]leucine by the explants is linear for at least 24 h, and the rate of protein synthesis increases significantly after estrogen injection. The explants synthesize and secrete serum albumin. B-apolipoprotein, and the phosphoprotein vitellogenin at relative rates which are similar to those reported for liver in vivo. Using this system, changes in the average rates of polypeptide chain elongation have been analyzed as a temporal sequence following a single injection of 17 beta-estradiol into cockerels. For this, average ribosome half-transit times were determined by measuring the kinetics of transfer of labeled polypeptides from polysomal-bound to released polypeptides. The data revealed a dramatic effect of estradiol on the average ribosome half-transit time with a maximum increase of 4.6-fold; however, the average size of polypeptides synthesized by explants at the peak of induction increased only 15% when compared to uninduced liver explants. These findings indicate that injection of estradiol results in large changes in the actual rates at which amino acids are added to the growing nascent polypeptide chain; that is, rates of polypeptide chain elongation. Therefore, translation-level regulation of protein synthesis in cockerel livers plays a significant part in determining the magnitude of the response to hormone stimulation.     

Multiattribute Bayesian Acceptance Sampling Plans for Screening and Scrapping Rejected Lots

A general model for multiattribute Bayesian acceptance sampling plans is developed which incorporates the multiattribute utility function of a decision maker in its design. The model accommodates various dispositions of rejected lots such as screening and scrapping. The disposition of rejected lots is shown to have a substantial impact on the solution approach used and on the ease of incorporation of multiattribute utility functions in terms of their measurement complexity, functional form, and parameter estimation. For example, if all attributes are screenable upon rejection, and the prior distributions of lot quality on each attribute are independent, then an optimal multiattribute sampling plan can be obtained simply by solving for an optimal single sampling plan on each attribute independently. A discrete search algorithm, based on pattern search, is also developed and shown to be very effective in obtaining an optimal multiattribute inspection plan when such separability cannot be accomplished.     

Psychological benefits of exercise paired with virtual reality: Outdoor exercise energizes whereas indoor virtual exercise relaxes.

In the present study the authors sought to evaluate the psychological effects of exercise when paired with virtual reality. One-hundred and twelve introductory psychology students (47 male and 65 female) were randomly assigned to one of three 20-min experimental conditions including (a) taking a brisk outdoor walk around a college campus, (b) walking on a laboratory treadmill combined with a virtual reality video presentation of the same college campus walk, or (c) viewing the virtual reality walk without participating in any actual exercise. Several standardized mood and enjoyment measures were administered immediately before and after the experimental conditions. Results suggest that greater energy was experienced while walking outside whereas less energy was reported when viewing the virtual reality walk with no actual exercise. These findings were most pronounced for female participants. Both female and male participants walking in the laboratory with the virtual reality were more relaxed and experienced the least tension of the three conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)