Functional and multivalued dependencies in nested databases generated by record and list constructor

The impact of the list constructor on two important classes of relational dependencies is investigated. Lists represent an inevitable data structure whenever order matters and data is allowed to occur repeatedly. The list constructor is therefore supported by many advanced data models such as genomic sequence, deductive and object-oriented data models including XML. The article proposes finite axiomatisations of functional, multivalued and both functional and multivalued dependencies in nested databases supporting record and list constructor. In order to capture different data models at a time, an abstract algebraic approach based on nested attributes is taken. The presence of the list constructor calls for a new inference rule which allows to infer non-trivial functional dependencies from multivalued dependencies. Further differences to the relational theory become apparent when the independence of the inference rules is investigated. The extension of the relational theory to nested databases allows to specify more real-world constraints and increases therefore the number of application domains. * Results of this article were partly presented at the 3rd International Symposium on Foundations of Information and Knowledge Systems (FoIKS), Vienna, Austria, 2004 [58], and the 23rd International Symposium on Principles of Database Systems (PODS), Paris, France, 2004 [54]. ** Sebastian Link was supported by Marsden Funding, Royal Society of New Zealand.     

Seven Research Challenges of Generalized 3D Documents

The rapid evolution of information and communication technology has always been a source for challenging new research questions in computer science. The vision of the emerging research field of semantic 3D is to establish the notion of generalized 3D documents that are full members of the family of generalized documents. This means that access would be content-based rather than based on metadata. The purpose of this article is to highlight the research issues that impede the realization of this vision today. The seven research challenges include: (1) '3D data set' can have many meanings, (2) a sustainable 3D file format, (3) representation-independent stable 3D markup, (4) representation-independent 3D query operations, (5) documenting provenance and processing history, (6) consistency between shape and meaning, and (7) closing the semantic gap     

A survey of multiple contractions

The AGM theory of belief contraction is extended tomultiple contraction, i.e. to contraction by a set of sentences rather than by a single sentence. There are two major variants: Inpackage contraction all the sentences must be removed from the belief set, whereas inchoice contraction it is sufficient that at least one of them is removed. Constructions of both types of multiple contraction are offered and axiomatically characterized. Neither package nor choice contraction can in general be reduced to contractions by single sentences; in the finite case choice contraction allows for reduction.     

RHEOPLUS:新改良聚羧酸醚类外加剂

新一代聚羧酸醚类(PCE)减水剂RHEOPLUS已成功开发。研究发现，REOPLUS与多种水泥兼容性良好，主要表现在掺量的高效性和良好的坍落度保持能力。其卓越的性能也同样体现在高流动混凝土的应用中，即良好的泵送性、和易性、抗离析和坍落度／流动度保持能力等。此外，RHEOPLUS对早期强度的改善也为其在预制构件中的应用带来了优势。相关研究正在进行，并已取得了一些阶段性成果。     

Morphology and stress relaxation in oriented polyolefin shrink films

Morphology and stress relaxation of oriented polyolefin films has been studied. The influence of orientation on morphology of the films has been investigated using X‐ray, DSC, and TEM. The relaxation time spectrum of oriented films has been investigated. It was shown that relaxation time spectrum of composite film can be predicted if one knows the relaxation time spectrum of each component in the film. An influence of irradiation on relaxation behavior of polyethylene film was shown as well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3424–3429, 2003     

Changes of disjunctively closed bases

An operator of contraction for a belief set (a theory) can be obtained by assigning to it a belief base and an operator of partial meet contraction for that base. It is argued that closure of the base under disjunction is an intuitively reasonable condition. Axiomatic characterizations are given of the contractions of belief sets that can be generated by (various types of) partial meet contraction on disjunctively closed bases. The corresponding revision operators are also characterized. Finally, some results are reported on operations on bases that are closed under material implication.I would like to thank Hans Rott and two anonymous referees for valuable comments and the Swedish Council for Research in the Humanities and Social Sciences for financial support.     

Engineering surface charges in a subtilisin: the effects on electrophoretic and ion-exchange behaviour

The introduction or removal of multiple charged amino acid residuesin the subtilisin Savinase^TM by genetic engineering allowedus to modify the electrostatic properties of this enzyme ina systematic way. The effects of these charge changes were investigatedexperimentally using ion-exchange chromatography and electrophoreticmobility in native gels all under identical conditions. Theexperiments clearly demonstrated that the overall charge ofa given protein is not the only factor determining electrophoreticmobility at low or moderate ionic strengths. For a series ofvariants having identical overall positive charge a linear relationwas observed between mobility towards the cathode and the totalnumber of charged residues present. This effect was found todepend on the type of (chloride) salt used: calcium ions giverise to complete screening of all negative charges, whereasonly partial screening is found for magnesium and sodium ions.In contrast, in the presence of sodium phosphate the overallcharge of the enzyme becomes slightly negative. These data indicatethat cations as well as anions may strongly perturb the overallcharge of proteins depending on the type of salt and on thenumber of charged amino acid residues present. The ion-exchangebehaviour demonstrated similar results, i.e. showing strongerenzyme adsorption with increasing numbers of surface chargeson a cation-exchange column run below the isoelectric pointof the proteins. However, the apparent sign reversal noted abovefor electrophoresis with sodium phosphate did not appear inthe ion-exchange experiments. This work provides further insightinto the adsorption of proteins to surfaces and the role playedby small ions, particularly when electrostatic forces dominatethe adsorption process.