Present limitations of accurate satellite Doppler positioning for tectonics. An example: Djibouti

One of the possibilities of the Doppler positioning from satellite is to provide geodetic measurements continuous in time without the need for reference stations. If measurements of sufficient accuracy can be achieved they may be used to study local surface displacements in relation to tectonic activity. A Doppler receiver of the MEDOC network is located near Djibouti in the Ghoubhat-Asal rift region which corresponds to the accreting plate boundary between the Arabian and African plates. In November 1978, a seismic and volcanic crisis occured in this area. Surface geodetic measurements and levellings performed in 1973 and 1978–79, just after the crisis, reveal a 60–80 cm sinking of the graben floor and a lateral extension of about 2 meters. Here we analyse Doppler measurements for the period January 1977 to November 1980. Point positions are computed for 7 to 10 day intervals using a precise ephemeris, and a moving window analysis is applied to the data. An apparent 2 meter uplift preceding the November 1978 seismic crisis is detected at Djibouti, whereas no similar phenomenon is observed at the two closest stations, Pretoria and Uccle-Brussels. However, field observations rule out a tectonic origin for this uplift. In Djibouti, the correlation between the apparent vertical station position and the electron density in the ionospheric F-layer reveals that a bias may be induced by the third order term of the ionospheric refractive index not previously taken into account, or more probably by the ray curvature through the ionosphere. This bias is particularly strong for our data set, from a station located close to the magnetic equator, and related to a period of rapid increase in the solar activity. Although our analysis fails to detect any tectonic displacement related to the rift seismic activity, it shows that similar tectonic studies by the Doppler method will be possible once the residual ionospheric errors are removed, for example by use of higher radio frequencies.     

A multimethod approach to inform epikarst drip discharge modelling: Implications for palaeo‐climate reconstruction

Resolving the hydrological processes that form speleothems and the palaeo‐climate archives that they contain is difficult. Typical approaches to hydrological investigation are not suited to karst landscapes, geophysics are seldom applied, drip monitoring and modelling have limitations, and ignoring potential hydrological impacts can result in a proxy record that does not reflect the external environment. We aim to understand the processes and controls that have created a palaeo‐climate proxy record preserved in a speleothem (JC001) in the “Grotto of Oddities,” part of the Jersey Cave at the Yarrangobilly Caves, Australia, to infer the likely nature and resolution of this record. Electrical resistivity tomography (ERT), traditional surveying, and drip discharge monitoring (April 2013 to February 2015) were used to investigate the structure and hydrology of the epikarst overlying the Grotto of Oddities. Data collected through these methods were then used to construct a physically informed and parsimonious drip hydrology model. Geophysics showed that changes in hillslope above the Grotto of Oddities are collocated with a region of low resistivity, which forms an epikarstic reservoir acting to supply enhanced discharge to the speleothem. Drip monitoring showed hysteretic behaviour with a distinct threshold response, and a simple drip classification indicated that the speleothem associated with the drip has the potential to record palaeo‐seasonality or an annual–decadal signal. Discharge modelling indicated discharge was comprised of quick and slow flow, and that discharge is probably perennial. These multimethod results together indicate that the speleothem likely represents a palaeo‐climate record of a length and resolution unprecedented for nonglacial areas of the Southern Hemisphere and for Australia in particular and will significantly enhance current knowledge of the climate of southeast Australia. Although ERT methods have previously been applied in the karst landscape, to our knowledge, this represents the first application of these multiple methods in combination as an approach to assess the fidelity of a speleothem, based on an understanding of the hydrological processes for palaeo‐climate reconstruction.     

Creating public space,creating ‘the public’: immigration politics and representation in two Copenhagen parks

ABSTRACT

Contestations over immigration, citizenship, and belonging play out every day in urban public space. In this article we study the design processes and use of two Copenhagen parks, Superkilen and Mimersparken, to explore the creation of public space and the “public” in Denmark. Who is part of the Danish “public”? What right do immigrant residents have to shape public space and their neighborhoods? How are the boundaries of Danish national identity policed and contested in public space in Copenhagen? The Danish government has increasingly moved toward far-right anti-immigrant stances, even while Copenhagen promotes a multicultural vision of a diverse and cosmopolitan city. Superkilen and Mimersparken illustrate the shortcomings of Copenhagen’s multiculturalism: though Copenhagen celebrates immigration, it left little space for residents to make meaningful decisions as political actors. In the case of Superkilen and Mimersparken, designers’ stylized idea of immigration is more celebrated than the actual presence of immigrant residents.     

Influence of natural radioactivity on creep rate

Steady-state creep in the earth's mantle is controlled by the diffusion coefficient and by the distances traveled by defects between sources and sinks. In this paper, we investigate the role played by additional vacancies created by natural radioactivity. According to recent studies, bombardment of solids by energetic particles can act as a perturbation. The resulting strain rate is proportional to the rate of vacancy creation and, contrary to ordinary creep mechanisms, is only weakly dependent on the temperature and the energy necessary to create those vacancies; it is independent of the grain size. The strain rate is of the same order of magnitude as the diffusion mechanism but smaller than the dislocation-climb rate by two to three orders of magnitude. Consequently, the strain rate produced by natural radioactivity does not play a major role in the observed rate of deformation, although it could constitute a lower limit to the creep rate and act as a regulatory mechanism. Furthermore, being less strongly affected by temperature and the vacancy-formation energy than are the other mechanisms, it is also less strongly affected by depth.     

Cyanotoxin contamination of semiarid drinking water supply reservoirs

Changing global climatic conditions and the continuous eutrophication of aquatic ecosystems have led to increased frequency, duration and toxicity of cyanobacterial blooms worldwide. This makes the provision of time series information on cyanotoxins extremely crucial for effective monitoring and management of water resources. The objective of the present study was to investigate seasonal and annual changes in microcystins (MCs), cylindrospermopsins (CYNs), saxitoxins (STXs), neo-saxitoxin (neo-STX) and anatoxin-a (ATX-a) concentrations in 11 public water supply reservoirs in the semiarid region of Brazil, from 2004 to 2011. Per time, at least one cyanotoxin was present in all the investigated reservoirs. High levels of MCs, CYNs, STXs and Neo-STX were detected simultaneously in Carpina, Duas Unas, Ipojuca, and Jucazinho reservoirs. All the investigated reservoirs had significant concentrations of MCs. The highest levels of MCs were found in Carpina (303,300.0 ng g^?1) and Duas Unas (122,053.9 ng g^?1) reservoirs, while the lowest concentration of the hepatotoxins was recorded in Ipojuca (10.3 ng g^?1) reservoir. On the other hand, CYN was detected in four reservoirs, STXs and Neo-STX in ten reservoirs and ATX-a in two reservoirs. The first record of CYN in Carpina reservoir was obtained in 2006. In addition, Carpina reservoir had the highest concentration of STXs and Neo-STX in the dry and rainy seasons, respectively. The high concentration of cyanotoxins observed in most samples obtained from semiarid reservoirs in Brazil demonstrates the need for regular monitoring and updated management programs.     

Neoliberal reforms in elder care in Norway: Roles of the state, Norwegian employers, and Polish nurses

After a worldwide financial crisis in the early 1980s, many states decided to implement new public management strategies. These strategies consist of private sector management practices that aim to reduce the cost of public services. The US and the UK first adopted the new public management model and other states soon followed. The Norwegian state was initially reluctant to adopt private management practices, but it eventually implemented modified reforms that suited the Norwegian socio-political context. This article investigates the ways in which the Norwegian state and Norwegian employers shape the labor force in Norwegian nursing homes through new public management strategies, and the tools that foreign-born nurses use to challenge these structures. The Norwegian state shapes the labor force through labor market policies and the rescaling of public services to local governments, and Norwegian employers reinforce the neoliberal values of the state in their hiring practices and daily operations in the workplace. In particular, this article analyzes the interweaving neoliberal institutional and personal factors that influence the working experiences of Polish nurses in a semi-private nursing home in Oslo. The city of Oslo created a unique public–private partnership with a city-owned company that manages three nursing homes in Oslo. The findings of this study indicate that Polish nurses in one of these nursing homes were negatively affected by the new public management strategies. They improved some of their working conditions over time but structural barriers still persist despite high demand for their skills.     

Microstructural criteria for reliable thermometry in low-temperature eclogites

Two Alpine eclogite bodies, sampled in metaophiolitic complexes of the Piemonte Zone, have been studied for geothermometry. It is demonstrated that temperature estimates, by both exchange thermometry and sizes of antiphase domains in omphacites, give rise to erratic results when the defect structures of the minerals are not taken into account. Microstructural criteria, by means of both optical and TEM microscopy, for reliable thermometry in low-temperature eclogites are disscussed. The dynamically recrystallized grains are the more suitable sites for the application of exchange thermometry, while only low-strained omphacites can be used for thermometry based on APD's.     

Lower cretaceous basalt and sediments from the Kerguelen Plateau

Geological samples from the southern Kerguelen Plateau include Lower Cretaceous basalt and lava breccia, probable Lower Cretaceous conglomerate and shelf limestone, Upper Cretaceous chert with dolomite, Upper Cretaceous-Eocene ooze, and Tertiary conglomerate. Neogene sediments are only a few hundred m thick, and include foraminiferal and diatomaceous ooze, and ice-rafted debris. In conjunction with seismic reflection profiles, the samples indicate Early Cretaceous near-shore volcanism, followed by erosion, sedimentation, and subsidence through Cretaceous; arching of the plateau at the end of Cretaceous; subsidence through Paleogene; widespread emergence in mid-Tertiary; and slow subsidence through Neogene.     

Impact de la vie benthique sur la genèse de nodules calcaires dans les black shales

The study of calcareous nodules from four organic-rich black shale series allows us to suggest a prominent part for benthic organisms in creating heterogeneities in the sediment, thus favouring microbially mediated early diagenesis based on organic matter consumption. To cite this article: J.-G. Bréhéret et al., C. R. Geoscience 336 (2004).     

Heterotrophic bacterial production in the Cretan Sea (NE Mediterranean)

In March and September 1995, bacterial production was measured by the ³H-leucine method in the oligotrophic Cretan Sea (Aegean Sea, Eastern Mediterranean) in the framework of the CINCS/MTP program. Samples were obtained from four stations (a coastal, a continental shelf and 2 open-sea stations) for the construction of vertical profiles of bacterial abundance and production. Bacterial production ranged from 0.1 μg C m⁻³ h⁻¹ at 1500 m depth, to 82 μg C m⁻³ h⁻¹ in March at 50 m at the coastal station. Higher bacterial integrated production was observed in March at the coastal station (131 mg C m⁻² d⁻¹ for the 0–100 m layer). Bacterial production, integrated through the water-column, was similar in March and September for the open-sea stations (60–70 mg C m⁻² d⁻¹). Relative to production, bacterial concentrations varied little between stations and seasons ranging from 9×10⁵ ml⁻¹ to 3×10⁵ ml⁻¹. Relationships between bacterial biomass and bacterial production indicated seasonal differences, likely reflecting resource limitation of bacterial biomass in March (bloom situation), and predator limitation of bacterial biomass in September (post-bloom situation).