Self-dual codes, subcode structures, and applications.

The classification of self-dual codes has been an extremely active area in coding theory since 1972 [33]. A particularly interesting class of self-dual codes is those of Type II which have high minimum distance (called extremal or near-extremal). It is notable that this class of codes contains famous unique codes: the extended Hamming [8,4,4] code, the extended Golay [24,12,8] code, and the extended quadratic residue [48,24,12] code. We examine the subcode structures of Type II codes for lengths up to 24, extremal Type II codes of length 32, and give partial results on the extended quadratic residue [48,24,12] code. We also develop a generalization of self-dual codes to Network Coding Theory and give some results on existence of self-dual network codes with largest minimum distance for lengths up to 10. Complementary Information Set (CIS for short) codes, a class of classical codes recently developed in [7], have important applications to Cryptography. CIS codes contain self-dual codes as a subclass. We give a new classification result for CIS codes of length 14 and a partial result for length 16

Productivity Analysis and Use of Sequence-Based Specification in a Web-Development Environment

This study evaluates the productivity of a software team in a web-development company and assesses the effects of the sequence-based specifications process on productivity and software accuracy in this environment. This study compares two software projects completed at GoTrain Corporation in 2001 and 2002. GoTrain is an application service provider and delivers environmental, safety and health (ES&H) training courses to a variety of clients through an Internet-based learning management system (LMS), called the Academy. GoTrain was established in 1999 through the merger of two small companies – a training services organization and a web design group. Because neither of the parent companies specialized in software development, the new GoTrain programming team began creating the first Academy applications without the structure of a formal software process. This study evaluates the productivity of the GoTrain programming team at the time formal software processes were introduced into the development environment. The first project evaluated was an upgrade of the GoTrain Academy to provide Spanish support for the end-used and was performed using the Microsoft Solutions Framework ™ (MSF) Process Model. The second project was an upgrade to the Academy software to support new employee training, enhanced reporting functionality, and improved administrative features. For this project, the MSF Process Model was again used but with sequence-based specification applied to selected Academy features during the design phase. Sequence-based specification is typically used in Cleanroom software engineering to create consistent and complete product requirements through enumeration of system inputs. Focusing on active server pages (ASPs), productivity analyses were based on the total lines of code (LOC) generated during the project and the number of hours required to create the code. The count of errors discovered during testing and the hours required for rework after the Academy release were used to evaluate the accuracy and correctness of the software. A productivity increase is seen between the first and second projects. The second project had higher LOC per man-hour than the first, which is likely a result of the software team becoming more experienced with the software process, developing cohesion among the team members, and improving communication among the project group. The files utilizing the sequence-based specification process in the second project had similar LOC and man-hour values as other files modified during this development effort. Files utilizing sequence-based specification required no modification after the versioned release of the Academy, whereas 68% of the files, similar in LOC and man-hours, created using existing specification processes required modification and re-deployment following the initial release

A Comparison Of Crassostrea Virginica And C. Ariakensis In Chesapeake Bay: Does Oyster Species Affect Habitat Function?

We examined the possibility that a nonnative oyster species would provide an ecologically functional equivalent of the native oyster species if introduced into the Chesapeake Bay. Habitat complexity and associated benthic communities of experimental triploid Crassostrea virginica and Crassostrea ariakensis reefs were investigated at 4 sites of varying salinity, tidal regime, water depth, predation intensity, and disease pressure in the Chesapeake Bay region (Maryland and Virginia). Four experimental treatments were established at each site: C. virginica, C. ariakensis, 50:50 of C. virginica and C. ariakensis, and shell only. Abundance, biomass, species richness, evenness, dominance, and diversity of reef-associated fauna were evaluated in relation to habitat location and oyster species. Although habitat complexity varied with location, no differences among complexity were associated with oyster species. Similarly, differences in faunal assemblages were more pronounced between sites than within sites. Our results show functional equivalency between oyster species with respect to habitat at the intertidal site and the low-salinity subtidal location. At subtidal sites of higher salinity, however, the numbers of organisms associated with C. virginica reefs per unit of oyster biomass were significantly greater than the numbers of organisms associated with C. ariakensis reefs. Multivariate analyses of data from subtidal high-salinity sites revealed unique communities associated with C. virginica treatments, whereas mixed-oyster species assemblages were functionally equivalent to monospecific C. ariakensis experimental treatments. Our study represents the first effort to quantify the potential habitat function of C. ariakensis, which has been proposed for an intentional introduction into Chesapeake Bay, and provides evidence of species-specific similarities and differences in reef-associated communities

Infant mortality in South Africa - distribution, associations and policy implications, 2007: an ecological spatial analysis

<p>Abstract</p> <p>Background</p> <p>Many sub-Saharan countries are confronted with persistently high levels of infant mortality because of the impact of a range of biological and social determinants. In particular, infant mortality has increased in sub-Saharan Africa in recent decades due to the HIV/AIDS epidemic. The geographic distribution of health problems and their relationship to potential risk factors can be invaluable for cost effective intervention planning. The objective of this paper is to determine and map the spatial nature of infant mortality in South Africa at a sub district level in order to inform policy intervention. In particular, the paper identifies and maps high risk clusters of infant mortality, as well as examines the impact of a range of determinants on infant mortality. A Bayesian approach is used to quantify the spatial risk of infant mortality, as well as significant associations (given spatial correlation between neighbouring areas) between infant mortality and a range of determinants. The most attributable determinants in each sub-district are calculated based on a combination of prevalence and model risk factor coefficient estimates. This integrated small area approach can be adapted and applied in other high burden settings to assist intervention planning and targeting.</p> <p>Results</p> <p>Infant mortality remains high in South Africa with seemingly little reduction since previous estimates in the early 2000's. Results showed marked geographical differences in infant mortality risk between provinces as well as within provinces as well as significantly higher risk in specific sub-districts and provinces. A number of determinants were found to have a significant adverse influence on infant mortality at the sub-district level. Following multivariable adjustment increasing maternal mortality, antenatal HIV prevalence, previous sibling mortality and male infant gender remained significantly associated with increased infant mortality risk. Of these antenatal HIV sero-prevalence, previous sibling mortality and maternal mortality were found to be the most attributable respectively.</p> <p>Conclusions</p> <p>This study demonstrates the usefulness of advanced spatial analysis to both quantify excess infant mortality risk at the lowest administrative unit, as well as the use of Bayesian modelling to quantify determinant significance given spatial correlation. The "novel" integration of determinant prevalence at the sub-district and coefficient estimates to estimate attributable fractions further elucidates the "high impact" factors in particular areas and has considerable potential to be applied in other locations. The usefulness of the paper, therefore, not only suggests where to intervene geographically, but also what specific interventions policy makers should prioritize in order to reduce the infant mortality burden in specific administration areas.</p