Positional information, positional error, and read-out precision in morphogenesis: a mathematical framework

The concept of positional information is central to our understanding of how cells in a multicellular structure determine their developmental fates. Nevertheless, positional information has neither been defined mathematically nor quantified in a principled way. Here we provide an information-theoretic definition in the context of developmental gene expression patterns and examine which features of expression patterns increase or decrease positional information. We connect positional information with the concept of positional error and develop tools to directly measure information and error from experimental data. We illustrate our framework for the case of gap gene expression patterns in the early Drosophila embryo and show how information that is distributed among only four genes is sufficient to determine developmental fates with single cell resolution. Our approach can be generalized to a variety of different model systems; procedures and examples are discussed in detail

PROGNOSTIC INVESTIGATIONS OF THE MORTALITY DUE TO CEREBROVASCULAR DISEASE IN THE REGION OF VARNA DISTRICT

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What Lies Beyond Virtual Community Informatics - Expanding a Research Agenda

The paper suggests directions for future work by bringing together the perspectives of researchers in community informatics (CI) and community operations research (COR). It begins with the assumption that community informatics has evolved into a broader field which includes also virtual CI. The outlined possibilities for future research in CI result from an analysis of past critiques of community informatics and of the evolution of group support systems and COR. The presented ideas complement and expand an earlier research agenda for virtual community informatics, aiming at the development of a better understanding of the needs for networking of virtual and physical communities

Comments about quantum symmetries of SU(3) graphs

For the SU(3) system of graphs generalizing the ADE Dynkin digrams in the classification of modular invariant partition functions in CFT, we present a general collection of algebraic objects and relations that describe fusion properties and quantum symmetries associated with the corresponding Ocneanu quantum groupo\"{i}ds. We also summarize the properties of the individual members of this system.Comment: 36 page

Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)

The magnetoconductive properties of ultrathin Pb films deposited on Si(111) are measured and compared with density-functional electronic band-structure calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111) slabs. A description with free-standing slabs is possible because it turned out that the Hall coefficient is independent of the substrate and of the crystalline order in the film. We show that the oscillations in sign of the Hall coefficient observed as a function of film thickness can be explained directly from the thickness dependent variations of the electronic bandstructure at the Fermi energy.Comment: 4 pages incl. 3 figures, RevTeX, to appear in Phys. Rev.

Decreased recall of primacy words predicts cognitive decline.

One of the cognitive changes associated with Alzheimer's disease is a diminution of the primacy effect, i.e., the tendency toward better recall of items studied early on a list compared with the rest. We examined whether learning and recall of primacy words predicted subsequent cognitive decline in 204 elderly subjects who were non-demented and cognitively intact when first examined. Our results show that poorer primacy performance in the Rey Auditory Verbal Learning Test delayed recall trials, but not in immediate recall trials, is an effective predictor of subsequent decline in general cognitive function. This pattern of performance can be interpreted as evidence that failure to consolidate primacy items is a marker of cognitive decline

Using Projects Scoring Rubrics to Assess Student Learning in an Information Systems Program

This paper is about using projects for assessment of student learning in different courses of an Information Systems (IS) program. An overview of the role of educational projects in student learning is presented. The various aspects of defining standardized rubrics across an IS program are discussed. A methodology for the use of such rubrics in assessing student learning in interrelated courses is proposed and is illustrated by example involving two Information Systems courses