More than symbioses : orchid ecology ; with examples from the Sydney Region

The Orchidaceae are one of the largest and most diverse families of flowering plants. Orchids grow as terrestrial, lithophytic, epiphytic or climbing herbs but most orchids native to the Sydney Region can be placed in one of two categories. The first consists of terrestrial, deciduous plants that live in fire-prone environments, die back seasonally to dormant underground root tubers, possess exclusively subterranean roots, which die off as the plants become dormant, and belong to the subfamily Orchidoideae. The second consists of epiphytic or lithophytic, evergreen plants that live in fire-free environments, either lack specialised storage structures or possess succulent stems or leaves that are unprotected from fire, possess aerial roots that grow over the surface of, or free of, the substrate, and which do not die off seasonally, and belong to the subfamily Epidendroideae. Orchid seeds are numerous and tiny, lacking cotyledons and endosperm and containing minimal nutrient reserves. Although the seeds of some species can commence germination on their own, all rely on infection by mycorrhizal fungi, which may be species-specific, to grow beyond the earliest stages of development. Many epidendroid orchids are viable from an early stage without their mycorrhizal fungi but most orchidoid orchids rely, at least to some extent, on their mycorrhizal fungi throughout their lives. Some are completely parasitic on their fungi and have lost the ability to photosynthesize. Some orchids parasitize highly pathogenic mycorrhizal fungi and are thus indirectly parasitic on other plants. Most orchids have specialised relationships with pollinating animals, with many species each pollinated by only one species of insect. Deceptive pollination systems, in which the plants provide no tangible reward to their pollinators, are common in the Orchidaceae. The most common form of deceit is food mimicry, while at least a few taxa mimic insect brood sites. At least six lineages of Australian orchids have independently evolved sexual deception. In this syndrome, a flower mimics the female of the pollinating insect species. Male insects are attracted to the flower and attempt to mate with it, and pollinate it in the process. Little is known of most aspects of the population ecology of orchids native to the Sydney Region, especially their responses to fire. Such knowledge would be very useful in informing decisions in wildlife management

Practical Implementation of Machine tool Metrology and Maintenance Management Systems

Maximising asset utilisation and minimising downtime and waste are becoming increasingly important to all manufacturing facilities as competition increases and profits decrease. The tools to assist with monitoring these machining processes are becoming more and more in demand. A system designed to fulfil the needs of machine tool operators and supervisors has been developed and its impact on the precision manufacturing industry is being considered. The benefits of implementing this system, compared to traditional methods, will be discussed here

Fine Structure of Marteilia sydneyi sp. n.: Haplosporidan Pathogen of Australian Oysters

A new species of oyster pathogen, Marteilia sydneyi, from Australian oysters, Crassostrea commercialis, is described incorporating light and electron microscope observations. The pathogen is a haplosporidan which exists as a plasmodium in the oyster hepatopancreas. Upon sporulation, 8 to 16 uninucleate sporangial primordia are internally cleaved (endogenously budded) from each plasmodium; thus conversion to a sporangiosorus occurs. Each sporangium enlarges and internally cleaves into 2 or 3 spore primordia each of which, in turn, internally cleaves into 3 uninucleate sporoplasms of graded sizes, the largest containing the smaller 2 in a vacuole and the intermediate-sized one containing the smallest in a vacuole. The spore wall is continuous without an orifice or operculum

Algorithms for #BIS-hard problems on expander graphs

We give an FPTAS and an efficient sampling algorithm for the high-fugacity hard-core model on bounded-degree bipartite expander graphs and the low-temperature ferromagnetic Potts model on bounded-degree expander graphs. The results apply, for example, to random (bipartite) Δ-regular graphs, for which no efficient algorithms were known for these problems (with the exception of the Ising model) in the non-uniqueness regime of the infinite Δ-regular tree

An analysis of economic infrastructure investment in South Africa

This paper analyses long-term trends in the development of South Africa's economic infrastructure and how this relates to the country's long-term economic growth. A database covering railways, roads, ports, air travel, phone lines and electricity was established for this purpose, and may facilitate further quantitative research. PSS (Pesaran, Shin and Smith, 1996, 2001) F-tests are used to identify directions of association between economic infrastructure and economic growth. These indicate long-run forcing relationships from public sector economic infrastructure investment and fixed capital stock to gross domestic product (GDP), from roads to GDP, and from GDP to a range of other types of infrastructure. There is also evidence of potential simultaneity between specific types of infrastructure and GDP. The evidence suggests three main findings. Firstly, the relationship between economic infrastructure and economic growth appears to run in both directions. Inadequate investment in infrastructure could create bottlenecks, and opportunities for promoting economic growth could be missed. Secondly, South Africa's stock of economic infrastructure has developed in phases. Policymakers should focus on choosing or encouraging the right type of infrastructure at the right time. Thirdly, the need for investment in economic infrastructure never goes away. The maintenance and expansion of infrastructure are important dimensions of supporting economic activity in a growing economy, provided that individual projects are chosen on the basis of appropriate cost-benefit analyses

Algorithms for #BIS-hard problems on expander graphs

We give an FPTAS and an efficient sampling algorithm for the high-fugacity hard-core model on bounded-degree bipartite expander graphs and the low-temperature ferromagnetic Potts model on bounded-degree expander graphs. The results apply, for example, to random (bipartite) $\Delta$-regular graphs, for which no efficient algorithms were known for these problems (with the exception of the Ising model) in the non-uniqueness regime of the infinite $\Delta$-regular tree. We also find efficient counting and sampling algorithms for proper $q$-colorings of random $\Delta$-regular bipartite graphs when $q$ is sufficiently small as a function of $\Delta$