No description available.

No description available.

This thesis provides a powerful general-purpose proof technique for the verification of systems, whether finite or infinite. It extends the idea of finite local model-checking, which was introduced by Stirling and Walker: rather than traversing the entire state space of a model, as is done for model-checking in the sense of Emerson, Clarke et al. (checking whether a (finite) model satisfies a formula), local model-checking asks whether a particular state satisfies a formula, and only explores the nearby states far enough to answer that question. The technique used was a tableau method, constructing a tableau according to the formula and the local structure of the model. This tableau technique is here generalized to the infinite case by considering sets of states, rather than single states; because the logic used, the propositional modal mu-calculus, separates simple modal and boolean connectives from powerful fix-point operators (which make the logic more expressive than many other temporal logics), it is possible to give a relatively straightforward set of rules for constructing a tableau. Much of the subtlety is removed from the tableau itself, and put into a relation on the state space defined by the tableau-the success of the tableau then depends on the well-foundedness of this relation. This development occupies the second and third chapters: the second considers the modal mu-calculus, and explains its power, while the third develops the tableau technique itself The generalized tableau technique is exhibited on Petri nets, and various standard notions from net theory are shown to play a part in the use of the technique on nets-in particular, the invariant calculus has a major role. The requirement for a finite presentation of tableaux for infinite systems raises the question of the expressive power of the mu-calculus. This is studied in some detail, and it is shown that on reasonably powerful models of computation, such as Petri nets, the mu-calculus can express properties that are not merely undecidable, but not even arithmetical. The concluding chapter discusses some of the many questions still to be answered, such as the incorporation of formal reasoning within the tableau system, and the power required of such reasoning.

The development of the concept of a filter leads to a theory of convergence in topological spaces. There is a close relationship between the concept of a net and that of a filter.

The purpose of this study was to collect data about engagement and involvement around technology issues by principals in Virginia. Virginia public school administrators were surveyed using the Principals Technology Leadership Assessment (PTLA) instrument and results compared to the National Educational Technology Standards for Administrators (NETS-A) (ISTE, 2002). This study, though limited in scope, provided meaningful data for research. The study reflects that despite 10 years of having NETS-A in place, Virginia public school administrators are barely meeting minimum standards in five out of the six dimensions. The study correctly looked at the old NETS-A standards but resulted in a call for action to meet the new NETS-A standards. Schools of education in Virginia could modify their coursework for public school administrator preparation to account for the areas of weakness as identified from the results of this study. Virginia public school divisions could address these weaknesses through directed staff development. The results of this study indicate, when compared to the 2001 study, little or no progress has been made in the area of public school administrator engagement and involvement in technology issues. The Virginia professional associations for public school administrators need to provide, measure, and help change the attitudes about technology standards. Individually, school principals need to step up and realize that engagement with technology is an important aspect of being a school leader.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Polysialic acid (PSA) is a linear homopolymer formed of chains of 2,8-linked sialic acid. Found predominantly attached to the neural cell adhesion molecule, PSA acts to reduce cell-cell adhesion during development. It is also found in some areas of the adult central nervous system (CNS) associated with persistent neuroplasticity. Preliminary data from our laboratory indicated an inverse relationship between PSA expression and the formation of perineuronal nets (PNNs), specialised extracellular matrix structures with a role in limiting plasticity in the adult CNS. The primary aims of this thesis were to investigate this relationship in more detail, using in vitro models of PNN formation and in vivo. Also, to evaluate whether lentiviral vector-mediated PSA expression can enhance locomotor recovery and neuroplasticity in a rodent model of spinal cord injury. PNNs were heterogeneously distributed throughout the grey matter of the rat cervical spinal cord, and increased in numbers down the dorsoventral axis. Induced expression of PSA in the spinal cord of either naïve or injured rats did not alter the number or density of PNNs. Similarly, enzymatic removal of PSA from the surface of cultured embryonic neurons did not affect the formation of the PNNs. In a rodent model of cervical spinal cord injury, induced PSA expression resulted in an improvement in hindlimb, but not forelimb, locomotor function compared to animals injected with control virus. Interestingly, this was not associated with an increased density of serotonin or synaptophysin-labelled boutons in the areas of induced PSA expression. Taken together, the data presented in this thesis suggests that while induced PSA expression may contribute to improved locomotor function in a model of cervical spinal cord injury, this is not due to a reduction in the density or number of PNNs in the spinal cord.

No description available.

Explores topological spaces, filters, and nets with definitions and examples.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 74-79.