Attitude stability of artificial satellites subject to gravity gradient torque

The stability of the rotational motion of artificial satellites is analyzed considering perturbations due to the gravity gradient torque, using a canonical formulation, and Andoyer’s variables to describe the rotational motion. The stability criteria employed requires the reduction of the Hamiltonian to a normal form around the stable equilibrium points. These points are determined through a numerical study of the Hamilton’s equations of motion and linear study of their stability. Subsequently a canonical linear transformation is used to diagonalize the matrix associated to the linear part of the system resulting in a normalized quadratic Hamiltonian. A semi-analytic process of normalization based on Lie–Hori algorithm is applied to obtain the Hamiltonian normalized up to the fourth order. Lyapunov stability of the equilibrium point is performed using Kovalev and Savchenko’s theorem. This semi-analytical approach was applied considering some data sets of hypothetical satellites, and only a few cases of stable motion were observed. This work can directly be useful for the satellite maintenance under the attitude stability requirements scenario.     

Tomorrow’s Forests: Adapting to A Changing Climate

Today’s forests are largely viewed as a natural asset, growing in a climate envelope, which favors natural regeneration of species that have adapted and survived the variability’s of past climates. However, human-induced climate change, variability and extremes are no longer a theoretical concept. It is a real issue affecting all biological systems. Atmospheric scientists, using global climate models, have developed scenarios of the future climate that far exceed the traditional climate envelope and their associated forest management practices. Not all forests are alike, nor do they share the same adaptive life cycles, feedbacks and threats. Much of tomorrow’s forests will become farmed forests, managed in a pro-active, designed and adaptive envelope, to sustain multiple products, values and services. Given the life cycle of most forest species, forest management systems will need to radically adjust their limits of knowledge and adaptive strategies to initiate, enhance and plan forests in relative harmony with the future climate. Protected Areas (IUCN), Global Biosphere Reserves (UNESCO) and Smithsonian Institution sites provide an effective community-based platform to monitor changes in forest species, ecosystems and biodiversity under changing climatic conditions.     

Scenarios for Community-based Approaches to Biodiversity Conservation: a case study from the Wet Tropics,Queensland, Australia

Natural resource management approaches that deliver biodiversity conservation remain elusive, with evidence of a persistent implementation gap between biodiversity science and conservation projects. Scenarios have been identified as potentially useful in addressing the complex issues underlying this implementation gap, but have been infrequently applied to biodiversity conservation. Our paper reports on action co-research to develop, apply and assess the efficacy of scenarios within a community-based natural resource management (CBNRM) approach to biodiversity conservation at Mission Beach, a key site within the globally significant Wet Tropics bioregion. We focused on the capacity of scenarios to address the issues of contested interests and uncertainty, aiming specifically to engage the community to build a cohesive vision. The scenarios' headline messages included a projected substantial loss of habitat in coastal vegetation communities that are highly valued by all stakeholders. Our assessment identified that the use of scenarios fulfilled the intended aims, resulting in a vision for biodiversity conservation that has substantial community support. Three factors contributed to this efficacy of the scenarios: (1) the focus on threat; (2) biodiversity science integration; and (3) simplicity in presentation. Further investigation of the potential of scenarios as tools to overcome the implementation gap in biodiversity conservation is recommended.     

The herbivorous impact of microzooplankton during two short-term Lagrangian experiments off the NW coast of Galicia in summer 1998

Microzooplankton (heterotrophic microplankton and heterotrophic nanoflagellates) and their herbivorous activity were estimated from dilution experiments in August 1998 during two Lagrangian drift experiments that sampled contrasting conditions—an upwelling/relaxation event along the shelf edge and an oligotrophic offshore filament. During upwelling/relaxation, heterotrophic microplankton were present at mean surface concentrations between 15,000 and 48,000 cells l⁻¹. Heterotrophic nanoflagellate concentrations were between 200 and 700 cells ml⁻¹ and the most abundant component of the heterotrophic microplankton was the aloricate choreotrich ciliates which increased dramatically in concentration from 6,000 to 24,000 cells l⁻¹ during the first 4 days of the study. Total microzooplankton biomass reached a maximum of 39mgC.m⁻³. In the filament, which developed from the upwelling, cell concentrations were lower and averaged 4,500 cells l⁻¹ for heterotrophic microplankton and 250 cells ml⁻¹ for heterotrophic nanoflagellates. Total microzooplankton biomass was about 10–12mgC.m⁻³. Microzooplankton turned over between 40 and 85% of the phytoplankton standing stock, thereby consuming between 5 and 78mg phytoplankton carbon.m⁻³.d⁻¹. The magnitude of this activity was highest during upwelling/relaxation and was positively correlated to heterotrophic nanoflagellate biomass and chlorophyll-a concentration but not heterotrophic microplankton biomass. The proportion of primary production grazed decreased from 160 to 59% d⁻¹ during upwelling/relaxation and ranged between 60 and 90% d⁻¹ in the filament. Microzooplankton herbivory within the euphotic zone increased from 684 to >2000mgC.m⁻².d⁻¹ during upwelling/relaxation and was between 327 and 802mgC.m⁻².d⁻¹ in the filament. Although microzooplankton herbivory was lower and less variable during the filament study, microzooplankton consumed on average 60% of the phytoplankton standing stocks which was higher than found during upwelling/relaxation. Microzooplankton assimilation efficiency ranged between 3 and 33% during upwelling/relaxation and between 0 and 13% in the filament. Our data demonstrate a close coupling between phytoplankton growth and microzooplankton herbivory in surface waters off the Galician Coast and suggest that microzooplankton may have been a significant sink for phytogenic carbon during August 1998.     

Radio sources in the 2dF Galaxy Redshift Survey – II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz

We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 deg² (about 20 per cent of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio identifications – the largest and most homogeneous set of radio source spectra ever obtained. The 2dFGRS radio sources span the redshift range     to 0.438, and are a mixture of active galaxies (60 per cent) and star-forming galaxies (40 per cent). About 25 per cent of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We make a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star formation density of         .     

The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007.
The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic     ) radio sources south of  δ=−15°  with      Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz.
In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming   S ∝ν^α  , decreases from  α^8.6_4.8= 0.11  between 4.8 and 8.6 GHz to  α²⁰_8.6=−0.16  between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has  α²⁰_8.6 > −0.5)  . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies.     

The historical geography of prostitution in Perth,Western Australia

This paper charts major changes in the locational distribution of female prostitution in the Perth metropolitan area during the twentieth century, and aims to explain why these changes took place. The study confirmed that there is a positive relationship between changes to law enforcement policy and changes to the spatial distribution of the sex industry. Factors that affect law enforcement policy (and thus the location of prostitution) include the social stigma associated with prostitution, economic forces that compete for urban space and political pressures to contain and occasionally relocate the trade. At the same time, and despite a number of major spatial redistributions caused by changes to law enforcement policy in Perth, the central city area has remained the sex industry's geographical focus throughout the twentieth century. This strong preference to be centrally located is related to the sex industry's primary locational imperatives, being access to major client catchments and availability of appropriate operational premises. The paper argues that a complex set of endogenous and exogenous factors contribute to the locational behaviour of prostitution, and that these forces and their associated dynamics need to be understood in order to successfully integrate the sex industry into an equitable and orderly town planning process.     

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky  (| b | > 10°)  . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with  ( K , H , J , r _F, b _J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75)  . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with   z ≤ 0.1  , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS .