Design of a high update-rate star sensor for arcsec-level attitude determination from balloon-borne X/γ astronomy platforms

This paper describes the design of a star sensor based upon a high dynamic range CCD in order to reach an arcsec-level attitude determination in balloon-borne missions. A custom star identification software was developed and laboratory-tested on a prototype assembled using commercial components. A set of numerical simulations have been carried out to study the dependence on the pointing precision of the centroid position accuracy, the number of detected stars and the effect of the image focusing. Moreover, the role of the electronic noise and the discrete pixel structure on the light signals is identified by the analysis of numerical simulations. Laboratory tests confirm that the arcsec pointing accuracy with a 1 Hz update rate can be achieved with our combination of custom-developed software and selected hardware components.     

The Influence of Community Size and Location on Different Dimensions of Vulnerability: a case study of Australian coastal communities

ABSTRACT

Coastal communities are part of the Australian identity but little is known about their characteristics and their long-term prosperity prospects. Increased migration to coastal areas and increased exposure to extreme climatic events indicates a need for social and economic data to inform socio-ecological systems planning. Here, we undertake a geo-spatial analysis to develop a typology of Australian coastal communities and assess relative vulnerability to climate-driven environmental change for a range of social and economic indicators. The aim of this study is to understand how the vulnerability of Australian coastal communities varies with geographic location or community size, and in comparison to other community types. Results show that both the population size and location of a coastal community matter and that coastal communities overall are more vulnerable on some socio-economic dimensions to climate-driven environmental change than their rural equivalents. However, results also demonstrate that the smallest coastal communities are strong in some important aspects of the human, social and financial domains, putting them in a good position to deal with some changes. Scale-appropriate and context-specific social policies are needed to address identified socio-economic vulnerabilities, supported by a range of formal and informal institutional structures, such as strategies to improve education and female workforce participation, and encourage participation in volunteering to increase human and social capital.     

Statistical Downscaling Based on Dynamically DownscaledPredictors： Application to Monthly Precipitation in Sweden

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.     

Crustal structure and tectonic setting of the south central Andes from gravimetric analysis

Based on terrestrial gravity data, in this paper we prepared a map of Bouguer anomalies, which was filtered to separate shallow and deep gravity sources. Based on a density model and gravimetric inversion techniques, the discontinuous crust-mantle boundary and the top of crystalline basement were modeled. Subsequently, the equivalent elastic thickness (Te) was evaluated, considering information from the crust-mantle discontinuity and topographic load, finding high Te values in the eastern Andean foothills and west of the Velasco range. These results are consistent with the positive isostatic and residual Bouguer anomaly values, which suggest the presence of high-density rocks in the mid-to upper crust. In addition, petrographic and geochemical analysis conducted in surface outcrops suggest a mantle origin.     

Phenological Changes of Blooming Diatoms Promoted by Compound Bottom-Up and Top-Down Controls

Understanding phytoplankton species-specific responses to multiple biotic and abiotic stressors is fundamental to assess phenological and structural shifts at the community level. Here, we present the case of Thalassiosira curviseriata, a winter-blooming diatom in the Bahía Blanca Estuary, Argentina, which displayed a noticeable decrease in the past decade along with conspicuous changes in phenology. We compiled interannual field data to assess compound effects of environmental variations and grazing by the invasive copepod Eurytemora americana. The two species displayed opposite trends over the period examined. The diatom decreased toward the last years, mainly during the winters, and remained relatively constant over the other seasons, while the copepod increased toward the last years, with an occurrence restricted to winter and early spring. A quantitative assessment by structural equation modeling unveiled that the observed long-term trend of T. curviseriata resulted from the synergistic effects of environmental changes driven by water temperature, salinity, and grazing. These results suggest that the shift in the abundance distribution of T. curviseriata toward higher annual ranges of temperature and salinity—as displayed by habitat association curves—constitutes a functional response to avoid seasonal overlapping with its predator in late winters. The observed changes in the timing and abundance of the blooming species resulted in conspicuous shifts in primary production pulses. Our results provide insights on mechanistic processes shaping the phenology and structure of phytoplankton blooms.     

Shaking‐table tests of flat‐bottom circular silos containing grain‐like material

According to Eurocode 8, the seismic design of flat‐bottom circular silos containing grain‐like material is based on a rough estimate of the inertial force imposed on the structure by the ensiled content during an earthquake: 80% of the mass of the content multiplied by the peak ground acceleration. A recent analytical consideration of the horizontal shear force mobilised within the ensiled material during an earthquake proposed by some of the authors has resulted in a radically reduced estimate of this load suggesting that, in practice, the effective mass of the content is significantly less than that specified. This paper describes a series of laboratory tests that featured shaking table and a silo model, which were conducted in order to obtain some experimental data to verify the proposed theoretical formulations and to compare with the established code provisions. Several tests have been performed with different heights of ensiled material – about 0.5 mm diameter Ballotini glass – and different magnitudes of grain–wall friction. The results indicate that in all cases, the effective mass is indeed lower than the Eurocode specification, suggesting that the specification is overly conservative, and that the wall–grain friction coefficient strongly affects the overturning moment at the silo base. At peak ground accelerations up to around 0.35 g, the proposed analytical formulation provides an improved estimate of the inertial force imposed on such structures by their contents. Copyright © 2015 John Wiley & Sons, Ltd.     

Economic vulnerability, beer and HIV/AIDS: The struggle to sustain farmer livelihoods and indigenous sorghum varieties in eastern Uganda

Drawing on a case study from eastern Uganda, this paper describes how social and environmental factors combine to affect the sustainability of both sorghum landraces and the farmers who depend on it for food and income security. It delineates how changing regional patterns of agricultural production and consumption, institutional neglect, economic hardship, natural resource degradation and a labour supply crisis precipitated by the HIV/AIDS pandemic, may be conspiring to place sorghum landraces at risk of extinction and, thus, undermine already precarious livelihoods. The paper therefore challenges the common assumption that marginalized rural women – by virtue of having diverse varieties and species under their care – can be expected to conserve that diversity.     

Introduced marine organisms as habitat modifiers

Introductions of non-indigenous species (NIS) are mostly discussed through their impact on biodiversity. However, NIS can also act as ecosystem engineers, influencing the habitat itself, positively or negatively, directly or indirectly, which should be included when making risk assessments. Special concern should be given to changes in ecological services provided by the ecosystem. Physically, NIS may affect the substrate itself, or alter habitat architecture, indirectly influencing water movements, sediment accumulation, and light conditions. Chemical changes brought upon by NIS occur both on small and large scales, some having positive effects on ecosystem services, others can perturb epibionts. Furthermore, NIS may negatively affect natural resources, aquaculture or create fouling communities, all resulting in a negative impact on economics. However, if removed, already established NIS can be used as bioremediators, having a positive effect on different ecosystems. Using NIS for habitat management may be economically profitable, but could affect the habitat adversely.     

The border as an engine for mobility and spatial integration: A study of commuting in a Swedish–Norwegian context

The purpose of the study was to analyse how cross-border commuting differed from intranational commuting in Sweden, and how cross-border mobilities affected spatial integration. The authors analysed patterns and spatial flows of cross-border commuting by comparing them with characteristics of intranational commuting. In the article, they explore the assumption that the border constitutes an ‘engine’ for work-related mobility, which affects processes of spatial integration in cross-border areas. The empirical material comprised data from surveys of commuting from the Swedish county of Värmland to Norway and commuting within Värmland. The findings showed that cross-border commuting shared common features with intranational commuting, including how the frequency of commuting was dependent on distance. The motives for commuting differed, and the reasons for working in Norway were economic rather than professional. In terms of spatial integration, cross-border commuting was mainly one-directional, from Sweden to Norway, while leisure mobility and migration tended to be in the opposite direction. The authors conclude that the border region is characterised by integration through specialisation, which involves a permanent state of ‘transient’ mobility. Thus, a win-win situation can be distinguished, in which the border serves as a resource and an ‘engine’ for cross-border integration, mobility and economic activities.