Congregation Formation in Multiagent Systems

We present congregating both as a metaphor for describing and modeling multiagent systems (MAS) and as a means for reducing coordination costs in large-scale MAS. When agents must search for other agents to interact with, congregations provide a way for agents to bias this search towards groups of agents that have tended to produce successful interactions in the past. This causes each agent's search problem to scale with the size of a congregation rather than the size of the population as a whole. In this paper, we present a formal model of a congregation and then apply Vidal and Durfee's CLRI framework [24] to the congregating problem. We apply congregating to the affinity group domain, and show that if agents are unable to describe congregations to each other, the problem of forming optimal congregations grows exponentially with the number of agents. The introduction of labelers provides a means of coordinating agent decisions, thereby reducing the problem's complexity. We then show how a structured label space can be exploited to simplify the labeler's decision problem and make the congregating problem linear in the number of labels. We then present experimental evidence demonstrating how congregating can be used to reduce agents' search costs, thereby allowing the system to scale up. We conclude with a comparison to other methods for coordinating multiagent behavior, particularly teams and coalitions.     

Carrier correlation effects in a quantum-well semiconductor lasermedium

This paper describes the results of a microscopic treatment of carrier-carrier scattering effects in the optical gain and refractive index spectra of a quantum-well semiconductor laser structure. The approach uses the Semiconductor Maxwell Bloch equations to describe the interaction between the carriers and the laser field, in the presence of many-body Coulomb interactions. Coulomb correlation effects are treated at the level of quantum kinetic theory in the Markovian limit. This approach shows the presence of nondiagonal Coulomb correlation contributions, in addition to the familiar diagonal contributions giving rise to polarization dephasing     

Design for six sigma through robust optimization

The current push in industry is focused on ensuring not only that a product performs as desired but also that the product consistently performs as desired. To ensure consistency in product performance, “quality” is measured, improved, and controlled. Most quality initiatives have originated and been implemented in the product manufacturing stages. More recently, however, it has been observed that much of a product’s performance and quality is determined by early design decisions, by the design choices made early in the product design cycle. Consequently, quality pushes have made their way into the design cycle, and “design for quality” is the primary objective. How is this objective measured and met? The most recent quality philosophy, also originating in a manufacturing setting, is six sigma. The concepts of six sigma quality can be defined in an engineering design context through relation to the concepts of design reliability and robustness – probabilistic design approaches. Within this context, design quality is measured with respect to probability of constraint satisfaction and sensitivity of performance objectives, both of which can be related to a design “sigma level”. In this paper, we define six sigma in an engineering design context and present an implementation of design for six sigma – a robust optimization formulation that incorporates approaches from structural reliability and robust design with the concepts and philosophy of six sigma. This formulation is demonstrated using a complex automotive application: vehicle side impact crash simulation. Results presented illustrate the tradeoff between performance and quality when optimizing for six sigma reliability and robustness.     

A time-predefined local search approach to exam timetabling problems

In recent years the processing speed of computers has increased dramatically. This in turn has allowed search algorithms to execute more iterations in a given amount of real-time. Does this necessarily always lead to an improvement in the quality of final solutions? This paper is devoted to the investigation of that question. We present two variants of local search where the search time can be set as an input parameter. These two approaches are: a time-predefined variant of simulated annealing and an adaptation of the “great deluge” method. We present a comprehensive series of experiments which show that these approaches significantly outperform the previous best results (in terms of solution quality) on a range of benchmark exam timetabling problems. Of course, there is a price to pay for such better results: increased execution time. We discuss the impact of this trade-off between quality and execution time. In particular we discuss issues involving the proper estimation of the algorithm's execution time and the assessment of its importance.     

Computer-based determination of size and shape in living cells

Measurement of cell volume in living epithelial cells has become an important technique in studies of membrane transport processes that function in cell volume regulation. Planimetry of video images of optical sections enables the measurement of the cross sectional area of each section. Cell volume is calculated from the measured area of each section and the known focus displacements. In the past the measurement of cross section area has been done by manual positioning of a cursor superimposed on the video image. Each experiment generates approximately 200 images in which two or more cells may be analysed. We have developed a computer-based method that uses one image as a template, and allows automated area determination of successive images by template matching and digital image processing. This new method is comparable to the older method in speed and accuracy, but requires much less effort from the experimenter.     

Molecular pharmacology of voltage-dependent calcium channels

Voltage-dependent Ca2+ channels serve as the only link to transduce membrane depolarization into cellular Ca(2+)-dependent reactions. A wide variety of chemical substances that have the ability to modulate Ca2+ channels have been demonstrated both for their clinic utility and for importance in elucidating the molecular basis of various biological responses. Recently, introduction of molecular biology to pharmacology has brought a great deal of information about the molecular basis of drug action in Ca2+ channels. In this review, we attempt to overview recent progress in understanding the interactions between Ca2+ channels and their blockers, namely Ca2+ antagonists, from a molecular and structural point of view.     

Partial Reduction in BRCA1 Gene Dose Modulates DNA Replication Stress Level and Thereby Contributes to Sensitivity or Resistance

BRCA1 is a well-known breast cancer risk gene, involved in DNA damage repair via homologous recombination (HR) and replication fork protection. Therapy resistance was linked to loss and amplification of the BRCA1 gene causing inferior survival of breast cancer patients. Most studies have focused on the analysis of complete loss or mutations in functional domains of BRCA1. How mutations in non-functional domains contribute to resistance mechanisms remains elusive and was the focus of this study. Therefore, clones of the breast cancer cell line MCF7 with indels in BRCA1 exon 9 and 14 were generated using CRISPR/Cas9. Clones with successful introduced BRCA1 mutations were evaluated regarding their capacity to perform HR, how they handle DNA replication stress (RS), and the consequences on the sensitivity to MMC, PARP1 inhibition, and ionizing radiation. Unexpectedly, BRCA1 mutations resulted in both increased sensitivity and resistance to exogenous DNA damage, despite a reduction of HR capacity in all clones. Resistance was associated with improved DNA double-strand break repair and reduction in replication stress (RS). Lower RS was accompanied by increased activation and interaction of proteins essential for the S phase-specific DNA damage response consisting of HR proteins, FANCD2, and CHK1.