Resource allocation in grid computing

Grid computing, in which a network of computers is integrated to create a very fast virtual computer, is becoming ever more prevalent. Examples include the TeraGrid and Planet-lab.org, as well as applications on the existing Internet that take advantage of unused computing and storage capacity of idle desktop machines, such as Kazaa, SETI@home, Climateprediction.net, and Einstein@home. Grid computing permits a network of computers to act as a very fast virtual computer. With many alternative computers available, each with varying extra capacity, and each of which may connect or disconnect from the grid at any time, it may make sense to send the same task to more than one computer. The application can then use the output of whichever computer finishes the task first. Thus, the important issue of the dynamic assignment of tasks to individual computers is complicated in grid computing by the option of assigning multiple copies of the same task to different computers. We show that under fairly mild and often reasonable conditions, maximizing task replication stochastically maximizes the number of task completions by any time. That is, it is better to do the same task on as many computers as possible, rather than assigning different tasks to individual computers. We show maximal task replication is optimal when tasks have identical size and processing times have a NWU (New Worse than Used; defined later) distribution. Computers may be heterogeneous and their speeds may vary randomly, as is the case in grid computing environments. We also show that maximal task replication, along with a c μ rule, stochastically maximizes the successful task completion process when task processing times are exponential and depend on both the task and computer, and tasks have different probabilities of completing successfully.     

Clearing the mind: A working memory model of distraction from negative mood.

The present research examined whether and how loading working memory can attenuate negative mood. In three experiments, participants were exposed to neutral, weakly negative, or strongly negative pictures followed by a task and a mood scale. Working memory demands were varied by manipulating task presence (Study 1), complexity (Study 2), and predictability (Study 3). Participants in all three experiments reported less negative moods in negative trials with high compared to low working memory demand. Working memory demands did not affect mood in the neutral trials. When working memory demands were high, participants no longer reported more negative moods in response to strongly negative pictures than to weakly negative pictures. These findings suggest that loading working memory prevents mood-congruent processing, and thereby promotes distraction from negative moods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the value of learning for Bernoulli bandits with unknown parameters

Investigates the multiarmed bandit problem, where each arm generates an infinite sequence of Bernoulli distributed rewards. The parameters of these Bernoulli distributions are unknown and initially assumed to be beta-distributed. Every time a bandit is selected, its beta-distribution is updated to new information in a Bayesian way. The objective is to maximize the long-term discounted rewards. We study the relationship between the necessity of acquiring additional information and the reward. This is done by considering two extreme situations, which occur when a bandit has been played N times: the situation where the decision maker stops learning and the situation where the decision maker acquires full information about that bandit. We show that the difference in reward between this lower and upper bound goes to zero as N grows large.     

Getting a Grip on Your Feelings: Effects of Action Orientation and External Demands on Intuitive Affect Regulation.

The authors propose that volitional action is supported by intuitive affect regulation, defined as flexible, efficient, and nonrepressive control of own affective states. Intuitive affect regulation should be most apparent among action-oriented individuals under demanding conditions. Consistent with this, a demanding context led action-oriented individuals to down-regulate negative affect in self-reports (Study 1), in an affective Simon task (Study 2), and in a face discrimination task (Study 3). In line with the idea that intuitive affect regulation is guided by top-down self-regulation processes, intuitive affect regulation in a face discrimination task was mediated by increases in self-accessibility (Study 3). No parallel effects emerged among action-oriented participants in a nondemanding context or among state-oriented participants. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Quantum dots with a paramagnetic coating as a bimodal molecular imaging probe

MRI detectable and targeted quantum dots were developed. To that aim, quantum dots were coated with paramagnetic and pegylated lipids, which resulted in a relaxivity, r(1), of nearly 2000 mM(-1)s(-1) per quantum dot. The quantum dots were functionalized by covalently linking alphavbeta3-specific RGD peptides, and the specificity was assessed and confirmed on cultured endothelial cells. The bimodal character, the high relaxivity, and the specificity of this nanoparticulate probe make it an excellent contrast agent for molecular imaging purposes.     

What's in a name: Implicit self-esteem and the automatic self.

This article explores the links between implicit self-esteem and the automatic self (D. L. Paulhus, 1993). Across 4 studies, name letter evaluations were positively biased, confirming that implicit self-esteem is generally positive (A. G. Greenwald & M. R. Banaji, 1995). Study 1 found that this name letter bias was stable over a 4-week period. Study 2 found that positive bias for name letters and positive bias for birth date numbers were correlated and that both biases became inhibited when participants were induced to respond in a deliberative manner. Studies 3–4 found that implicit self-evaluations corresponded with self-reported self-evaluations, but only when participants were evaluating themselves very quickly (Study 3) or under cognitive load (Study 4). Together, these findings support the notion that implicit self-esteem phenomena are driven by self-evaluations that are activated automatically and without conscious self-reflection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unfixing the fixed pie: A motivated information-processing approach to integrative negotiation.

Negotiators tend to believe that own and other's outcomes are diametrically opposed. When such fixed-pie perceptions (FPPs) are not revised during negotiation, integrative agreements are unlikely. It was predicted that accuracy motivation helps negotiators to release their FPPs. In 2 experiments, accuracy motivation was manipulated by (not) holding negotiators accountable for the manner in which they negotiated. Experiment 1 showed that accountability reduced FPPs during face-to-face negotiation and produced more integrative agreements. Experiment 2 corroborated these results: Accountable negotiators revised their FPPs even when information exchange was experimentally held constant. Experiment 2 also showed that accountability is effective during the encoding of outcome information. Negotiators appear flexible in their reliance on FPPs, which is consistent with a motivated information processing model of negotiation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the static assignment to parallel servers

The authors study the static assignment to M parallel, exponential, heterogeneous servers. Blocked customers are lost, while the objective is to minimize the average number of blocked customers. The problem is formulated as a stochastic control problem with partial observation, and an equivalent full observation problem is formulated. Numerical experiments are conducted and the structure of the optimal policies is studied     

Botulinum toxin type A treatment of cosmetically disturbing masseteric hypertrophy]

Two patients, a woman aged 21 and a man aged 29, with asymmetrical swellings of both mandibular angles and a painful, heavy sensation in the masticatory muscles (and in the woman also round the maxillary joint), were diagnosed as having hypertrophy of the masseter muscles. Both had the habit of jaw clenching and tooth grinding. Treatment consisted not of the traditional surgical debulking which also allows correction of overdeveloped osseous mandibular angles, but of injections with botulinum toxin type A. Injection of 40-60 IU (product: Botox) per muscle was followed by some atrophy; cosmetically satisfactory results were achieved after repetition of the treatment a few months later. Reduction of muscle volume was confirmed by a quantitative volumetric assessment of MRI scans. In the female patient, the pain also abated.     

Optimal Shift Scheduling with a Global Service Level Constraint

We study a shift scheduling problem for call centers with an overall service level objective. We prove a property of this problem, called multimodularity, that ensures that a local search algorithm terminates with a globally optimal solution. We report on computations performed using real call center data.