Acaricide resistance and genetic affinities of some selected populations of Tetranychus urticae Koch in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science (Horticultural) in Entomology at Massey University

A study of resistance to acaricides in a number of populations of the two-spotted spider mite, Tetranychus urticae, in New Zealand had been carried out. Natural genetic and cytoplasmic incompatibilities between populations were also investigated with a view to possible biological control of the pest. Facets of acaricide resistance that were studied included multi-resistance, cross-resistance, negatively correlated resistance and the inheritance of resistance. Chemicals used included an organophosphate representative (parathion-methyl), a carbamate (formetanate), an ungrouped compound (tricyclohexyltin hydroxide) and an organochlorine (dicofol). Cross-resistance was demonstrated between parathion-methyl and formetanate in five populations obtained from widely separate areas of New Zealand. The resistance to parathion of three strains was found to be inherited as a single dominant character and transmissible by both sexes. Cytoplasmic factors (or nucleo-cytoplasmic interactions) and minor genes were found to contribute slightly to the expression of total resistance. No resistance to tricyclohexyltin hydroxide (Plictran) and dicofol (Kelthane) was detected. High degrees of incompatibility (haploid egg lethality) were observed in the hybrids of crosses between the various populations. Chromosomal rearrangements in balanced, heterozygous conditions, in conjunction with the cytoplasm, were considered to be important factors determining the interpopulational sterilities. The interpopulational incompatibility phenomenon was found to be multi-factorial and not associated with the resistance factor. The egg mortalities of some backcross series which remained constantly high in spite of several crossings, implicated that the introduction of normal males to a resistant mite population in an enclosed area (e.g. in a glasshouse) might be a worthwhile proposition in the integrated control of spider mites. Backcross hybrids, on allowing to multiply randomly, were capable of forming new gene combinations, leading consequently to the formation of new strains which were genetically different from the original parents used in the backcross series

Decidable Models of Recursive Asynchronous Concurrency

Asynchronously communicating pushdown systems (ACPS) that satisfy the empty-stack constraint (a pushdown process may receive only when its stack is empty) are a popular decidable model for recursive programs with asynchronous atomic procedure calls. We study a relaxation of the empty-stack constraint for ACPS that permits concurrency and communication actions at any stack height, called the shaped stack constraint, thus enabling a larger class of concurrent programs to be modelled. We establish a close connection between ACPS with shaped stacks and a novel extension of Petri nets: Nets with Nested Coloured Tokens (NNCTs). Tokens in NNCTs are of two types: simple and complex. Complex tokens carry an arbitrary number of coloured tokens. The rules of NNCT can synchronise complex and simple tokens, inject coloured tokens into a complex token, and eject all tokens of a specified set of colours to predefined places. We show that the coverability problem for NNCTs is Tower-complete. To our knowledge, NNCT is the first extension of Petri nets, in the class of nets with an infinite set of token types, that has primitive recursive coverability. This result implies Tower-completeness of coverability for ACPS with shaped stacks

HoCHC: A Refutationally Complete and Semantically Invariant System of Higher-order Logic Modulo Theories

We present a simple resolution proof system for higher-order constrained Horn clauses (HoCHC) - a system of higher-order logic modulo theories - and prove its soundness and refutational completeness w.r.t. the standard semantics. As corollaries, we obtain the compactness theorem and semi-decidability of HoCHC for semi-decidable background theories, and we prove that HoCHC satisfies a canonical model property. Moreover a variant of the well-known translation from higher-order to 1st-order logic is shown to be sound and complete for HoCHC in standard semantics. We illustrate how to transfer decidability results for (fragments of) 1st-order logic modulo theories to our higher-order setting, using as example the Bernays-Schonfinkel-Ramsey fragment of HoCHC modulo a restricted form of Linear Integer Arithmetic

The Suppression of Radiation Reaction and Laser Field Depletion in Laser-Electron beam interaction

The effects of radiation reaction (RR) have been studied extensively by using the ultraintense laser interacts with the counter-propagating relativistic electron. At the laser intensity at the order of $10^{23}$ W/cm$^2$, the effects of RR are significant in a few laser period for a relativistic electron. However, the laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulate this interaction with a beam of $10^9$ electrons by means of Particle-in-Cell (PIC) method. We observed that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is due to the ponderomotive force that prevents the electrons from approaching the center of the laser pulse and leads to the interaction at weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.Comment: 6 pages, 3 figure

The Lazy Lambda Calculus : an investigation into the foundations of functional programming

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