Detecting environmental impacts on metapopulations of mound spring invertebrates - Assessing an incidence function model

We use a stochastic patch occupancy model of invertebrates in the Mound Springs ecosystem of South Australia to assess the ability of incidence function models to detect environmental impacts on metapopulations. We assume that the probability of colonisation decreases with increasing isolation and the probability of extinction is constant across spring vents. We run the models to quasi-equilibrium, and then impose an impact by increasing the local extinction probability. We sample the output at various times pre- and postimpact, and examine the probability of detecting a significant change in population parameters. The incidence function model approach turns out to have little power to detect environmental impacts on metapopulations with small numbers of patches. (C) 2001 Elsevier Science Ltd. All rights reserved.

Integrating high and moderate spatial resolution image data to estimate forest age structure

The collection of spatial information to quantify changes to the state and condition of the environment is a fundamental component of conservation or sustainable utilization of tropical and subtropical forests, Age is an important structural attribute of old-growth forests influencing biological diversity in Australia eucalypt forests. Aerial photograph interpretation has traditionally been used for mapping the age and structure of forest stands. However this method is subjective and is not able to accurately capture fine to landscape scale variation necessary for ecological studies. Identification and mapping of fine to landscape scale vegetative structural attributes will allow the compilation of information associated with Montreal Process indicators lb and ld, which seek to determine linkages between age structure and the diversity and abundance of forest fauna populations. This project integrated measurements of structural attributes derived from a canopy-height elevation model with results from a geometrical-optical/spectral mixture analysis model to map forest age structure at a landscape scale. The availability of multiple-scale data allows the transfer of high-resolution attributes to landscape scale monitoring. Multispectral image data were obtained from a DMSV (Digital Multi-Spectral Video) sensor over St Mary's State Forest in Southeast Queensland, Australia. Local scene variance levels for different forest tapes calculated from the DMSV data were used to optimize the tree density and canopy size output in a geometric-optical model applied to a Landsat Thematic Mapper (TU) data set. Airborne laser scanner data obtained over the project area were used to calibrate a digital filter to extract tree heights from a digital elevation model that was derived from scanned colour stereopairs. The modelled estimates of tree height, crown size, and tree density were used to produce a decision-tree classification of forest successional stage at a landscape scale. The results obtained (72% accuracy), were limited in validation, but demonstrate potential for using the multi-scale methodology to provide spatial information for forestry policy objectives (ie., monitoring forest age structure).

The evolution of controlled multitasked gene networks: The role of introns and other noncoding RNAs in the development of complex organisms

Eukaryotic phenotypic diversity arises from multitasking of a core proteome of limited size. Multitasking is routine in computers, as well as in other sophisticated information systems, and requires multiple inputs and outputs to control and integrate network activity. Higher eukaryotes have a mosaic gene structure with a dual output, mRNA (protein-coding) sequences and introns, which are released from the pre-mRNA by posttranscriptional processing. Introns have been enormously successful as a class of sequences and comprise up to 95% of the primary transcripts of protein-coding genes in mammals. In addition, many other transcripts (perhaps more than half) do not encode proteins at all, but appear both to be developmentally regulated and to have genetic function. We suggest that these RNAs (eRNAs) have evolved to function as endogenous network control molecules which enable direct gene-gene communication and multitasking of eukaryotic genomes. Analysis of a range of complex genetic phenomena in which RNA is involved or implicated, including co-suppression, transgene silencing, RNA interference, imprinting, methylation, and transvection, suggests that a higher-order regulatory system based on RNA signals operates in the higher eukaryotes and involves chromatin remodeling as well as other RNA-DNA, RNA-RNA, and RNA-protein interactions. The evolution of densely connected gene networks would be expected to result in a relatively stable core proteome due to the multiple reuse of components, implying,that cellular differentiation and phenotypic variation in the higher eukaryotes results primarily from variation in the control architecture. Thus, network integration and multitasking using trans-acting RNA molecules produced in parallel with protein-coding sequences may underpin both the evolution of developmentally sophisticated multicellular organisms and the rapid expansion of phenotypic complexity into uncontested environments such as those initiated in the Cambrian radiation and those seen after major extinction events.

Analysis of acousto-ultrasonic characteristics for contact-type transducers coupled to composite laminated plates

The acousto-ultrasonic (AU) input-output characteristics for contact-type transmitting and receiving transducers coupled to composite laminated plates are considered in this paper. Combining a multiple integral transform method, an ordinary discrete layer theory for the laminates and some simplifying assumptions for the electro-mechanical transduction behaviour of the transducers, an analytical solution is developed which can deal with all the wave processes involved in the AU measurement system, i.e, wave generation, wave propagation and wave reception. The spectral response of the normal contact pressure sensed by the receiving transducer due to an arbitrary input pulse excited by the transmitting transducer is obtained. To validate the new analytical-numerical spectral technique in the low-frequency regime, the results are compared with Mindlin plate theory solutions. Based on the analytical results, numerical calculations are carried out to investigate the influence of various external parameters such as frequency content of the input pulse, transmitter/receiver spacing and transducer aperture on the output of the measurement system. The results show that the presented analytical-numerical procedure is an effective tool for understanding the input-output characteristics of the AU technique for laminated plates. (C) 2001 Elsevier Science Ltd. All rights reserved.

Generalized quasi mode theory of macroscopic canonical quantization in cavity quantum electrodynamics and quantum optics I. Theory

The quasi mode theory of macroscopic quantization in quantum optics and cavity QED developed by Dalton, Barnett and Knight is generalized. This generalization allows for cases in which two or more quasi permittivities, along with their associated mode functions, are needed to describe the classical optics device. It brings problems such as reflection and refraction at a dielectric boundary, the linear coupler, and the coupling of two optical cavities within the scope of the theory. For the most part, the results that are obtained here are simple generalizations of those obtained in previous work. However the coupling constants, which are of great importance in applications of the theory, are shown to contain significant additional terms which cannot be 'guessed' from the simpler forms. The expressions for the coupling constants suggest that the critical factor in determining the strength of coupling between a pair of quasi modes is their degree of spatial overlap. In an accompanying paper a fully quantum theoretic derivation of the laws of reflection and refraction at a boundary is given as an illustration of the generalized theory. The quasi mode picture of this process involves the annihilation of a photon travelling in the incident region quasi mode, and the subsequent creation of a photon in either the incident region or transmitted region quasi modes.

Noise-free scattering of the quantized electromagnetic field from a dispersive linear dielectric

We study the scattering of the quantized electromagnetic field from a linear, dispersive dielectric using the scattering formalism for quantum fields. The medium is modeled as a collection of harmonic oscillators with a number of distinct resonance frequencies. This model corresponds to the Sellmeir expansion, which is widely used to describe experimental data for real dispersive media. The integral equation for the interpolating field in terms of the in field is solved and the solution used to find the out field. The relation between the ill and out creation and annihilation operators is found that allows one to calculate the S matrix for this system. In this model, we find that there are absorption bands, but the input-output relations are completely unitary. No additional quantum-noise terms are required.

Vaccine efficacy of recombinant cathepsin D aspartic protease from Schistosoma japonicum

Mice were vaccinated with recombinant Schistosoma japonicum cathepsin D aspartic protease, expressed in both insect cells and bacteria, in order to evaluate the vaccine efficacy of the schistosome protease. Mean total worm burdens were significantly reduced in vaccinated mice by 21-38%, and significant reductions in female worm burdens were also recorded (22-40%). Vaccination did not reduce fecundity; rather, we recorded increased egg output per female worm in vaccinated animals, suggesting a crowding effect. Vaccinated mice developed high levels of antibodies (predominantly IgG1, IgG2a and IgG2b isotypes), but there was no correlation between antibody levels and protective efficacy. Immune sera from vaccinated mice did not inhibit the in vitro degradation of human haemoglobin by the recombinant protease, and passive transfer of serum or antibodies from vaccinated animals, before and after parasite challenge, did not significantly reduce worm or egg burdens in recipient animals. These results suggest that antibodies may not play a key role in the protective effect elicited, and that protection may be due to a combination of humoral and cell-mediated responses.

Non-coding RNAs: the architects of eukaryotic complexity

Around 98% of all transcriptional output in humans is noncoding RNA. RNA-mediated gene regulation is widespread in higher eukaryotes and complex genetic phenomena like RNA interference, co-suppression, transgene silencing, imprinting, methylation, and possibly position-effect variegation and transvection, all involve intersecting pathways based on or connected to RNA signaling. I suggest that the central dogma is incomplete, and that intronic and other non-coding RNAs have evolved to comprise a second tier of gene expression in eukaryotes, which enables the integration and networking of complex suites of gene activity. Although proteins are the fundamental effectors of cellular function, the basis of eukaryotic complexity and phenotypic variation may lie primarily in a control architecture composed of a highly parallel system of trans-acting RNAs that relay state information required for the coordination and modulation of gene expression, via chromatin remodeling, RNA-DNA, RNA-RNA and RNA-protein interactions. This system has interesting and perhaps informative analogies with small world networks and dataflow computing.

Transforming chaos to periodic oscillations

We demonstrate that the dynamics of an autonomous chaotic class C laser can be controlled to a periodic state via external modulation of the pump. In the absence of modulation, above the chaos threshold, the laser exhibits Lorenz-like chaotic pulsations. The average amplitude and frequency of these pulsations depend on the pump power. We find that there exist parameter windows where modulation of the pump power extinguishes the chaos in favor of simpler periodic behavior. Moreover we find a number of locking ratios between the pump and laser output follow the Farey sequence.

Xmds: eXtensible multi-dimensional simulator

A software package that efficiently solves a comprehensive range of problems based on coupled complex nonlinear stochastic ODEs and PDEs is outlined. Its input and output syntax is formulated as a subset of XML, thus making a step towards a standard for specifying numerical simulations.

A Ku-band active transmit-array module with a horn or patch array as a signal launching/receiving device

This paper is concerned with the design of a Ku-band active transmit-array module of transistor amplifiers excited by either a pyramidal horn or a patch array Optimal distances between the active transmit array and the signal-launching:receiving device, which is either a passive corporate-fed array or a horn, are determined to maximise the power gain at a design frequency: Having established these conditions, the complete structure is investigated in terms of operational bandwidth and near-field and far-field distributions measured at the output side of the transmit array, The experimental results show that the use of a corporate-fed array as an illuminating/receiving device gives higher gain and significantly larger operational bandwidth, An explanation for this behavior is sought.

Steepness and deepness in the Australian macroeconomy

This study uses nonparametric tests - the triples test and the BDS test, to examine whether key Australian macroeconomic aggregates exhibit nonlinearities and important 'steepness' and 'deepness' asymmetries at the business cycle frequency. Evidence is found of nonlinearities but there is little evidence of deepness in the Australian macroeconomy. However, there is evidence of steepness, especially concerning labour market variables, as well as both the CPI and M3. The evidence suggests that unemployment (employment) rises (falls) rapidly in recessions and only recovers slowly over time. Also, positive asymmetries in M3 are reflected in similar asymmetries in the CPI but not in output, consumption or investment.

Early rise in blood pressure following administration of adrenocorticotropic hormone-[1-24] in humans

1. An elevation in blood pressure has been consistently observed 24 h after adrenocorticotropic hormone (ACTH) administration and is caused by increased ACTH-stimulated cortisol secretion, in association with increased cardiac output. The aim of the present study was to investigate the previously undefined time of onset of this increase in blood pressure in normal humans. 2. Ten normal healthy volunteers received 250 mug ACTH-[1-24], in 500 mL normal saline, infused at a constant rate over 8 h. Six subjects also received a placebo infusion (normal saline only). Blood pressure, heart rate and cortisol levels were determined hourly. Adrenocorticotropic hormone (ACTH-[1-24] plus native ACTH) was measured at 0, 1, 7 and 8 h. 3. Infusion of ACTH-[1-24] produced maximal secretion rates of cortisol, resulting in a mean peak plasma level of 985 +/- 46 nmol/L at 8 h. In response, blood pressure and heart rate rose significantly by 2 h and remained generally elevated for the duration of the infusion. 4. The early onset of haemodynamic responses is consistent with classical steroid receptor-mediated genomic mechanisms, but could be due non-genomic mechanisms. 5. The cardiovascular consequences of therapeutic use of ACTH are well recognized. This results of the present study suggest that even diagnostic administration of ACTH, delivered over a few hours, may raise blood pressure.

Family dynasties in the Tasmanian native hen (Gallinula mortierii)

For species that form multi-generational and territorial family groups, resource-rich areas are predicted to support family dynasties in which one genetic lineage continuously occupies an area and may even expand to occupy surrounding areas. Data from a long-term study of Tasmanian native hens (Gallinula mortierii) support this prediction. The reproductive success and dispersal patterns of 18 hen lineages were monitored for seven breeding seasons and over several generations. The founder group with the highest average territory quality produced the highest total number of fledged young and the highest number of fledged linear descendants, accounting for 24% of the combined reproductive output of these 18 lineages. In the space of 6 years, this single genetic lineage expanded from one territory to occupy 12 of the 47 territories present in the population. This rate of expansion was over four times the population average for the same period. A multivariate analysis revealed that the success of a genetic lineage depended only on the number of high-quality territories surrounding the founder group. These results further demonstrate the resource-dependent nature of reproductive success in this species, and also highlight the potential importance of family dynasties in other cooperative species with complex social dynamics and dispersal patterns.

The ecological basis of life history variation in marsupials

Our understanding of the diversity of mammalian life histories is based almost exclusively on eutherian mammals, in which the slow-fast continuum persists even after controlling for effects of body size and phylogeny. In this paper, we use modern comparative methods to test the extent to which this eutherian-based framework can be extrapolated to metatherian mammals. First, we examine the pattern of covariation among life history traits, and second, we test for correlations between variation in life history and variation in six candidate ecological variables: type of diet, extent of intraspecific competition, risk of juvenile mortality, diurnal pattern of activity, arboreality, and rainfall pattern. Even when controlling for body size and phylogeny, we observe a slow-fast continuum in metatherian mammals. Some parameters involved are different from those identified by studies of eutherians, but the underlying relationships among longevity, fecundity, and age at maturity persist. We also show that overall variation in a key life history variable, reproductive output (measured by annual reproductive rate and litter size), is significantly related to variation in type of diet, with a foliage-rich diet being associated with low fecundity. This is interesting because, although ecological correlations have been found within some eutherian subgroups, modern comparative approaches have failed to reveal robust ecological correlates of overall life history diversity in eutherians. Copyright ESA. All rights reserved.