The Australia telescope 20 GHz survey: hardware, observing strategy, and scanning survey catalog

The Australia Telescope 20 GHz (AT20G) survey is a large area (2?? sr), sensitive (40 mJy), high frequency (20 GHz) survey of the southern sky. The survey was conducted in two parts: an initial fast scanning survey, and a series of more accurate follow-up observations. The follow-up survey catalog has been presented by Murphy et al. (MNRAS 402:2403, 2010). In this paper we discuss the hardware setup and scanning survey strategy as well as the production of the scanning survey catalog.     

Yam Cultivation on the East Coast of New Caledonia: adaptation of agriculture to social and economic changes

Agriculture represents less than 2 per cent of the GDP of New Caledonia where the economy (and wage-earning activities) is dominated by the service sector and the nickel industry. However, family farming remains strong, especially for the Indigenous Melanesian tribes of the east coast of New Caledonia. Yams (Dioscorea spp.) are still one of the pillars of traditional Kanak society despite the social and economic changes that followed colonisation by France. This study of Kanak yam cultivation on the north-eastern coast of New Caledonia underscores the fact that yam cultivation systems have greatly changed since the 1950s, when they were last described. In addition to customary gift exchanges and subsistence consumption, yams are increasingly being grown for market sales. Five cropping systems, three yam production systems, and three Kanak social activity systems are described and their linkages to each other are explained. There are three levels of Kanak market participation: none, transitional, and fully engaged, and the extent of market participation and associated technical choices defines farmers’ levels of cultural activity and the nature and characteristics of yam cultivation.     

Separation of phytoplanktonic pigments by HPLC for the study of phyto-zooplankton trophic relationships

Phyto-zooplankton trophic relationships were studied using phytoplanktonic pigments (chlorophylls and carotenoids) as organic natural markers. Pigments were separated by high-pressure liquid chromatography (HPLC).Comparison of pigment profiles from monospecific cultures of various taxonomic groups (Chlorophyceae, Bacillariophyceae and Cyanobacteria) and from Cladocera crustaceans (Daphnia magna) fed with these cultures, showed that the characteristic pigment associations of the different taxa are conserved during their transfer from primary producers to secondary consumers.Chromatographic profiles of the Bacillariophyceae and Chlorophyceae type were obtained fromDaphnia respectively fed with mixtures of a Chlorophyceae and a diatom species and mixture of a Chlorophyceae and a Cyanobacterium. This showed the importance of this method in demonstrating a possible selective feeding by the herbivorous zooplankton.The observation of pigment profiles of the Dinophyceae type following feeding of a zooplankton assemblage from Lake Pavin within this natural medium (phytoplankton dominated by a Dinophyceae) and of a Chlorophyceae type profile as the same assemblage was fed in the laboratory on phytoplankton from Lake Villerest (composed of about 80% Cyanobacteria and 20% Chlorophyceae), suggested that this method could be applied to the natural environment.     

Biological and Temporal Variations of Trace Element Concentrations in the Moss Species Scleropodium purum (Hedw.) Limpr.

Over a period of one year, the moss Scleropodium purum was sampled every two weeks in a French rural area to determine the levels of Li, Na, Al, Si, P, Ca, V, Mn, Fe, Zn, Ba, Hg, and Pb. The element distribution in the moss shoot was studied throughout the year. An apical bioconcentration was discovered for Na, P, Ca, Mn, and Zn, whereas higher levels were found in the basal fraction for Li, Al, Si, V, Fe, Ba, Hg, and Pb. A significant variation of element concentrations was observed during the sampling period. In the apical part Li, Al, Si, V, Fe, Ba, and Hg show maximum levels in the summer and minimum in the autumn. The same pattern was found with Ca and Mn in the whole plant, whereas Na showed opposite fluctuations.     

Assessing the impact of Celaque National Park on forest fragmentation in western Honduras

The effectiveness of parks as management regimes is much in debate. This study examines the effect of establishment of the Celaque National Park, Honduras, in 1987, on limiting deforestation through a comparison with the surrounding landscape using remote sensing, GIS and landscape pattern analysis. Pressure on the park region is found to relate spatially to the locations of towns and roads, with increasing deforestation in the landscape surrounding the park. In contrast, the park has been largely successful in maintaining forest cover. Although the extent of change within the park is not pronounced, the pattern of change is. Expansion of agriculture and coffee production have led to increasing pressure on the park boundaries, with as much as 25% of the landscape surrounding the park experiencing land cover change between 1996 and 2000. This has significant implications for the future of the park.     

The destruction of the past: Nonrenewable cultural resources

Destruction of cultural resources has increased dramatically in the last quarter of the 20th century as a result of two forces: first, development and construction, and second, the astonishing explosion of demand for primitive and prehistoric art. On the cover: Rock art of the Mimbres Culture at the Pony Hills site in south-west New Mexico. Similar rock art nearby has been destroyed by pistol shots or chipped out and illegally sold. Photo by Andrew Gulliford, Public History Program, Middle Tennessee State University.For the purposes of Legacy, the term cultural resource refers to both archeological and architectural resources. For archaeology, it includes, but is not limited to, traditions, lifeways, cultural and religious practices, and other institutions to which a community, neighborhood, Native American tribe, or other group ascribes cultural significance, together with any artifacts and real property associated with such elements. For architecture, it includes, but is not limited to, buildings, sites, districts, structures, or objects, landscapes, and vistas. In addition, the term encompasses historic documents and relics.     

Event-scale floodplain accretion revealed through tree-ring analysis of buried plains cottonwoods,Powder River,MT, USA

Six plains cottonwoods along the axis of a meander were excavated to determine if dendrochronology could identify the year and location of germination and date past overbank sedimentation events. Samples from all excavated trees showed clear anatomical changes associated with burial, including increased vessel size, decreased definition of annual ring boundaries, and decreased ring widths. Some of these burial signatures were created by deposition of only a few centimeters of sediment, and most burial events were detected by multiple samples from the same tree. Four of the trees germinated at or near the upper surfaces of bar deposits, while two germinated within thin overbank deposits draped over bar deposits, indicating that germination is closely associated with bars. Dates and inferred thicknesses of overbank sedimentation events are consistent with repeated topographic surveys and data obtained from cesium-137 (¹³⁷Cs) analyses. However, the record of overbank sedimentation extracted from the trees does not entirely reflect the history of past peak discharges documented by stream gaging, largely because individual trees are progressively less likely to be flooded through time as the river migrates farther away. Germination dates and locations closely track past positions of the river channel. Germination elevations and the elevations of the tops of point bars appear to be decreasing with time as the bend migrates, implying vertical incision by Powder River at a rate of 7.1 ± 4.3 mm/yr. The rate of floodplain growth determined by elevation changes decreases progressively through time, ultimately reaching an apparent plateau after 0.8–1.3 m of vertical accretion. While similar patterns of vertical accretion have previously been interpreted as resulting from decreasing flood probability with increasing floodplain elevation, distance from the channel is also a first-order control on vertical floodplain growth. © 2019 John Wiley & Sons, Ltd.     

Nitrogenase activity and estimates of nitrogen fixation by freshwater benthic blue‐green algae

The sandy substrate of Lake Taharoa (west coast, North Island, New Zealand ‐ 35°50'S, 173°41'E) is covered by communities of filamentous algae that extend from the exposed beach down to 21 m depth. The algae bind the sand to form crusts and mats which may break off as discrete plates. The dominant species are the blue‐greens Microcoleus, Nostoc, Phormidium, Lyngbya, Oscillatoria, Scytonema, Stigonema, Shizothrix, Calothrix, Dichothrix, Tolypothrix, and Anabaena, with occasional high concentrations of the desmid Cylindrocystis. Nitrogenase activity, measured by acetylene reduction, showed a wide range of rates (4–150 μmol C₂H₄ m^‐2h^‐1). Estimates of annual rates of nitrogen fixation by the Taharoa communities are comparable with those for periphytic blue‐green algae‐dominated systems reported elsewhere.     

High‐calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites

Abstract— Our analyses of high quality spectra of several S‐type asteroids (17 Thetis, 847 Agnia, 808 Merxia, and members of the Agnia and Merxia families) reveal that they include both low‐ and high‐calcium pyroxene with minor amounts of olivine (<20%). In addition, we find that these asteroids have ratios of high‐calcium pyroxene to total pyroxene of >～0.4. High‐calcium pyroxene is a spectrally detectable and petrologically important indicator of igneous history and may prove critical in future studies aimed at understanding the history of asteroidal bodies. The silicate mineralogy inferred for Thetis and the Merxia and Agnia family members requires that these asteroids experienced igneous differentiation, producing broadly basaltic surface lithologies. Together with 4 Vesta (and its smaller “Vestoid” family members) and the main‐belt asteroid 1489 Magnya, these new asteroids provide strong evidence for igneous differentiation of at least five asteroid parent bodies. Based on this analysis of a small subset of the near‐infrared asteroid spectra taken to date with SpeX at the NASA IRTF, we expect that the number of known differentiated asteroids will increase, consistent with the large number of parent bodies inferred from studies of iron meteorites.     

Migration in a transitional economy: Beyond the planned and spontaneous dichotomy in Vietnam

Migration is frequently portrayed as a negative force in its relationship with economic and social development. This negative perception is exhibited through describing population movements as either ‘forced’ (e.g. political and environmental refugees) or ‘voluntary’ movements (e.g. economic and uninhibited relocation). This paper examines the limitations of this conceptual dualism. It points out that the dualistic approach, widely used in the context of developing countries, simplifies a highly complex phenomenon by ignoring its essential heterogeneity and spatial and temporal dynamics. As such, it is limited in explaining and understanding the globally diversified, historically and politically contextualised situations. Focusing on the migratory experiences of contemporary Vietnam, the study identifies major patterns and trends of population mobility in the country in the past fifty years. It shows that despite the state’s continued attempts to reshape the spatial distribution of population over recent historical periods, the policy outcomes with respect to population mobility have been swayed as much by individuals and their families in pursuit of their own aspirations and livelihoods as by state plans. The Vietnam case has provided evidence of a much more complicated relationship between migration and livelihoods than the conceptual dichotomy assumes, and the opportunity for a richer set of policy options. We argue that the evidence from Vietnam, and elsewhere, warrants an integrated approach to studying migration, combining analysis at the macro- and micro-levels with the nexus lying at the critical decision-making point of the individual or household.