Theoretically optimal forms for very long-span bridges under gravity loading.

Long-span bridges have traditionally employed suspension or cable-stayed forms, comprising vertical pylons and networks of cables supporting a bridge deck. However, the optimality of such forms over very long spans appears never to have been rigorously assessed, and the theoretically optimal form for a given span carrying gravity loading has remained unknown. To address this we here describe a new numerical layout optimization procedure capable of intrinsically modelling the self-weight of the constituent structural elements, and use this to identify the form requiring the minimum volume of material for a given span.

Giardia duodenalis typing from stools: a comparison of three approaches to extracting DNA, and validation of a probe-based real-time PCR typing assay.

A weighted, multi-attribute approach was used to compare three methods for direct extraction of Giardia duodenalis DNA from 15 microscopy-positive stools: (1) a QIAamp spin-column method for stools including a 10 min incubation at 95 °C, (2) method 1 preceded by five freeze-thaw cycles and (3) bead beating with guanidine thiocyanate using a FastPrep-28 machine followed by liquid-phase silica purification of DNA. The attributes compared included DNA yield measured using a new triose phosphate isomerase (tpi) gene probe-based real-time PCR, also described here. All three methods shared 100 % PCR positivity, while the bead-beating method provided the highest G.

A comparison of two approaches to extracting Cryptosporidium DNA from human stools as measured by a real-time PCR assay.

Direct extraction of Cryptosporidium DNA from 46 stools by bead-beating, guanidine thiocyanate and silica purification provided slightly lower PCR positivity (93.5% vs. 100%) and higher threshold cycle values (mean 34.

Resolution and evolution of the duck-billed platypus karyotype with an X1Y1X2Y2X3Y3X4Y4X5Y5 male sex chromosome constitution.

The platypus (2n = 52) has a complex karyotype that has been controversial over the last three decades. The presence of unpaired chromosomes and an unknown sex-determining system especially has defied attempts at conventional analysis. This article reports on the preparation of chromosome-specific probes from flow-sorted chromosomes and their application in the identification and classification of all platypus chromosomes.

Reversal and convergence in marsupial chromosome evolution.

The karyotypes of marsupial species are characterized by their relatively low number of chromosomes, and their conservation. Most species have diploid numbers lying between the two modes, 2n = 14 and 2n = 22, but the karyotype of Aepyprymnus rufescens is exceptional in containing 2n = 32 chromosomes. Many differences in diploid number between marsupial species can be accounted for by particular fissions and fusions, which are easy to detect because of the low numbers of chromosomes in each karyotype.