Background

A common analytical technique involves using a Coxian distribution to model a general distribution, where the Coxian distribution agrees with on the first three moments. This technique is motivated by the analytical tractability of the Coxian distribution. Algorithms for mapping an input distribution to a Coxian distribution largely hinge on knowing a priori the necessary and sufficient number of stages in the representative Coxian distribution. In this paper, we formally characterize the set of distributions which are well-represented by an-stage Coxian distribution, in the sense that the Coxian distribution matches the first three moments of. We also discuss a few common, practical examples. Lastly, we derive a partial characterization of the set of busy period durations which are well-represented by an-stage Coxian distribution

Characterisation and partial sequence analysis of two novel cypoviruses isolated from the winter moth Operophtera brumata (Lepidoptera: Geometridae)

The complete nucleotide sequences of genomic segments S5 to S10 from Operophtera brumata cypovirus 18 (OpbuCPV18), and the complete nucleotide sequences of genomic segments S2, S5, S9 and S10 from Operophtera brumata cypovirus 19 (OpbuCPV19) have been determined. Each genome segment contained a single open reading frame (ORF). Conserved motifs 5′ (AGUAAA....GUUAGCU) 3′ were found at the ends of each segment of OpbuCPV18, whilst conserved motifs 5′ (AACAAA....UUUGC) 3′ were found at each segment terminus of OpbuCPV19. The putative proteins were compared with those of other members of the Reoviridae family. Phylogenetic analysis using the polyhedrin gene (S10) indicated that OpbuCPV18 was most closely related to Dendrolimus punctatus cypovirus 1, whilst OpbuCPV19 was most closely related to Trichoplusia ni cypovirus 15. In addition, analysis of S2, which encoded a putative RNA-dependant RNA polymerase gene, confirmed OpbuCPV19 belonged to the genus Cypovirus. Following the expression of the ORF from OpbuCPV19 S10, using a baculovirus expression vector, occlusion bodies were observed in insect cell culture. This demonstrated that segment 10 coded for the polyhedrin gene, capable of forming a polyhedral crystalline matrix