Direct Product Decompositions of Lattices, Closures and Relation Schemes

In this paper we study direct product decompositions of closure operations and lattices of closed sets. We characterize direct product decompositions of lattices of closed sets in terms of closure operations, and find those decompositions of lattices which correspond to the decompositions of closures. If a closure on a finite set is represented by its implication base (i.e. a binary relation on a powerset), we construct a polynomial algorithm to find its direct product decompositions. The main characterization theorem is also applied to define direct product decompositions of relational database schemes and to find out what properties of relational databases and schemes are preserved under decompositions

Ensuring the existence of a BCNF-decomposition that preserves functional dependencies in O (N2) time

A simple condition is presented that ensures that a relation scheme R with a set F of functional dependencies has a Boyce-Codd normal form (BCNF)-decomposition that has the lossless-join property and preserves functional dependencies

A Port Graph Rewriting Approach to Relational Database Modelling

International audienceWe present new algorithms to compute the Syntactic Closure and the Minimal Cover of a set of functional dependencies, using strategic port graph rewriting. We specify a Visual Domain Specific Language to model relational database schemata as port graphs, and provide an extension to port graph rewriting rules. Using these rules we implement strategies to compute a syntactic closure, analyse it and find minimal covers, essential for schema normalisation. The graph program provides a visual description of the computation steps coupled with analysis features not available in other approaches. We prove soundness and completeness of the computed closure. This methodology is implemented in PORGY

Programmed state assignment algorithms for asynchronous sequential machines.

An important step in the synthesis procedure for realizing a normal fundamental mode asynchronous sequential circuit is the internal state assignment. Although systematic methods have been developed to construct minimum-transition-time state assignments, they become long and tedious with hand methods for machines with more than 7 or 8 internal states. To extend the application of these algorithms to larger problems, this paper presents an efficient digital computer program for generating minimum-variable state assignments. An alternate program is also presented which, though shorter, does not guarantee a minimum-variable assignment --Abstract, page ii

Preferentially Quantized Linker DNA Lengths in Saccharomyces cerevisiae

The exact lengths of linker DNAs connecting adjacent nucleosomes specify the intrinsic three-dimensional structures of eukaryotic chromatin fibers. Some studies suggest that linker DNA lengths preferentially occur at certain quantized values, differing one from another by integral multiples of the DNA helical repeat, ∼10 bp; however, studies in the literature are inconsistent. Here, we investigate linker DNA length distributions in the yeast Saccharomyces cerevisiae genome, using two novel methods: a Fourier analysis of genomic dinucleotide periodicities adjacent to experimentally mapped nucleosomes and a duration hidden Markov model applied to experimentally defined dinucleosomes. Both methods reveal that linker DNA lengths in yeast are preferentially periodic at the DNA helical repeat (∼10 bp), obeying the forms 10n+5 bp (integer n). This 10 bp periodicity implies an ordered superhelical intrinsic structure for the average chromatin fiber in yeast

Classification and sensitivity of taxonomic and functional diversity indices of anurans in the Andean coffee cultural landscape

Taxonomical and functional facets of diversity are crucial to imderstanding the effects of landscape transformaron on species assemblages, although there is a lack of consensus on the degree of congruence between diversity’ indices across land-uses. We evaluated the effect of natural and anthropogenic land cover types on anurans in the Andean región of Colombia. Changes between land cover types were detected but no effect of dimatic season on the structure of anuran assemblages. Species with larger body sizes showed a greater affínity for anthropogenic land cover types. We analyzed the functional facet of diversity- (based on diet and morpho-logical traits) and discovered that the degree of congruence with taxonomic diversity metrics changed when comparing different land cover types. We evidenced a strong effect of the type of vegetation cover on the Hill numbers (from zero to third orders) for functional diversity’ but not for the other taxonomic diversity indices. Of all the diversity metrics evaluated, we found that Rao’s quadratic entropy, functional dispersión, and average functional diversity were the most sensitive indices to land-use change. Surprisingly, the surrounding of houses, the land cover type with the greater degree of anthropogenic intervention had the higher valúes of functional diversity, suggesting broader types of species resource acquisition. These results suggest the importance of landscape mosaics in the conservation of different facets of anuran diversity. We also emphasize the importance of measuring anuran functional traits to understand more comprehensively the effects of landscape trans-formation at the assemblage level and to appropriately direct conservation and management actions.N/

Data and results from a study of internal convective cooling systems for hypersonic aircraft

An extensive survey of current and future airframe construction materials and coolants was conducted, so that the most promising candidates could be examined for cooled-panel, cooling-system and airframe concepts. Consideration was given to over 100 structural materials, 50 coolants, 6 classes of structural panel concepts, 4 classes of thermal panel concepts with numerous variations, and 3 overall cooled airframe design approaches, including unshielded, shielded, and dual temperature types. The concept identification and parametric comparison phase examined all major elements of the convectively cooled airframe, including the differing requirements at various locations on the aircraft. The parametric results were used for the investigation to two separate vehicles, a hypersonic transport with a length of 96 meters (314 feet) and a weight of 24,000 kg (528,600 lb) and a hypersonic research airplane, with a length of 25m (80 ft) and a weight of 20,300 kg (447,000 lb)