Properties of the Mixed Polyethyleneglycoles-iodide Ions Adsorption Layers on a Mercury Electrode

Adsorption of a mixture of I- ions and polyethyleneglycoles of molecular weights 400 (PEG 400) and 10 000 (PEG 10 000) on a mercury electrode from NaClO4 solution of constant ionic strength is described. Parallel courses of linear dependences of the potential of zero charge with the increase of I- ion concentration in the Solutions with PEG and without PEG indicate removal of water molecules by adsorption of I- ions and not PEG molecules. The standard Gibbs energy of adsorption ΔadG° and parameter B obtained from the virial isotherm do not depend on PEG 10 000 concentration. This can be associated with the full coverage of the electrode surface with its molecules already at a concentration of 10-4 mol dm-3. For PEG 400, a dependence of adsorption parameters on its concentration was observed. Lower repulsive interaction between the adsorbed I- ion in PEG Solutions indicates a favourable effect of PEG molecules on I- ion adsorption compared with H2O. The values of rate constants ksapp of Zn2+ ion reduction as a piloting ion were determined. Acceleration of the processes inhibited by PEG 400 or PEG 10 000 by I- ions is based on formation of ion pairs Zn2+−I- on the mercury surface. Kinetic measurements con-firm stronger adsorption of PEG 10 000 compared with PEG 400

Causes of unrest at silicic calderas in the East African Rift: new constraints from InSAR and soil-gas chemistry at Aluto volcano, Ethiopia

This work is a contribution to the Natural Environment Research Council (NERC) funded RiftVolc project (NE/L013932/1, Rift volcanism: past, present, and future). W.H., J.B., T.A.M., and D.M.P. are supported by and contribute to the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes, and Tectonics (COMET). Envisat data were provided by ESA. ALOS data were provided through ESA third party mission. W.H. funded by NERC studentship, NE/J5000045/1. Additional funding for fieldwork was provided by University College (University of Oxford), the Geological Remote Sensing Group, the Edinburgh Geological Society, and the Leverhulme Trust. Analytical work at the University of New Mexico was supported by the Volcanic and Geothermal Volatiles Lab at the Center for Stable Isotopes and an NSF grant EAR-1113066 to T.P.F.Restless silicic calderas present major geological hazards, and yet many also host significant untapped geothermal resources. In East Africa this poses a major challenge, although the calderas are largely unmonitored their geothermal resources could provide substantial economic benefits to the region. Understanding what causes unrest at these volcanoes is vital for weighing up the opportunities against the potential risks. Here we bring together new field and remote sensing observations to evaluate causes of ground deformation at Aluto, a restless silicic volcano located in the Main Ethiopian Rift (MER). Interferometric Synthetic Aperture Radar (InSAR) data reveal the temporal and spatial characteristics of a ground deformation episode that took place between 2008 and 2010. Deformation time-series reveal pulses of accelerating uplift that transition to gradual long-term subsidence, and analytical models support inflation source depths of ∼5 km. Gases escaping along the major fault zone of Aluto show high CO2 flux, and a clear magmatic carbon signature (CO2–δ13C of −4.2 to −4.5 ‰). This provides compelling evidence that the magmatic and hydrothermal reservoirs of the complex are physically connected. We suggest that a coupled magmatic-hydrothermal system can explain the uplift-subsidence signals. We hypothesize that magmatic fluid injection and/or intrusion in the cap of the magmatic reservoir drives edifice wide inflation while subsequent deflation is related to magmatic degassing and depressurization of the hydrothermal system. These new constraints on the plumbing of Aluto yield important insights into the behaviour of rift volcanic systems and will be crucial for interpreting future patterns of unrest.Publisher PDFPeer reviewe

Les représentations de l’île Maurice dans l’imaginaire littéraire franco‑mauricien

Mauritius is a small island in the Indian Ocean, whose population approximates to that of Warsaw. Since its discovery, the island was ruled by several governments: Dutch, French, and English, before it finally became independent in 1968. On this piece of land of about 2,000 m2 live direct descendants of the inhabitants of three continents: Europe, Africa and Asia. The history of the island and the Mauritian people create its specificity. Undoubtedly, the fact that Mauritius is an island largely influences the Mauritian society. In my article, I will study how this impacts on the society, including its writers. I will seek to define the nature of their relationships. I will try to describe the various representations of the island in Franco‑Mauritian literary fiction at the turn of the twentieth and twenty‑first centuries. Since this topos is in dichotomy of good and evil, I will consider the island as a synonym of a half‑paradise and a half‑prison. Subsequently, I will analyse it as a character of its own. Finally, I will argue that Mauritius can be seen as a reflection of the world, a miniature model. In summary, afterexamining the various images of Mauritius, I will try to demonstrate its special status in the Mauritian society, especially in literature. Key words: Mauritian society, insularity, Franco‑Mauritian literary fictio

Ananda Devi: a writer at the crossroads of cultures

Ananda Devi is a francophone-Mauritian writer who lives (and creates) near Geneva. She is the author of numerous novels, short stories and volumes of poetry. Although the stories of her characters are fictitious, Devi’s texts are strongly inspired by her native island, its history and its ethnic, cultural and linguistic heterogeneity. In her novels, Devi employs numerous stylistic devices to empower individuals who are regarded as worse, excluded from the society due to their deficits

Respiration and assimilation processes reflected in the carbon isotopic composition of atmospheric carbon dioxide

This paper presents diurnal variations of concentration and carbon isotopic composition of atmospheric carbon dioxide caused by respiration and assimilation processes. Air samples were collected during early and late summer in 1998 in unpolluted area (village Guciow located near the Roztocze National Park, SE Poland) in three different environments: uncultivated field on a hill, a meadow in the Wieprz river valley and a forest. The effect is very strong during intensive vegetation growth on a sunny day and clear night. The largest diurnal variations in atmospheric CO2 concentration and its carbon isotopic composition in June above the meadow were about 480 ppm and 10‰, respectively

Diurnal variations and vertical distribution of δ13C, and concentration of atmospheric and soil CO2 in a meadow site, SE Poland

We provide the results of 24-hour observations made in a meadow site located in a small river valley in Central Europe. Samples of atmospheric air were taken from three horizons: near the soil (0.05 m), in the grass (0.5 m) and above the meadow (2 m) at two-hour intervals. At the same time, samples of soil air were collected from two horizons: -0.1 and -0.5 m. We have found a variation of δ13C above the ground from -6‰ during the day to -20‰ late at night accompanied by variations in CO2 concentration from 270 ppm during the day, to various levels late at night at different heights above the ground. The maximum concentration was 1430 ppm at the ground level. The correlation coefficient between δ 13C and reciprocal of concentration was the highest (R2 = 0.984) for the samples collected 2 m above the ground, the regression line clearly indicating CO2 mixing from the two sources: atmospheric and biogenic reservoirs. The intercept of the mixing line yields δC = -23.0‰ for the biogenic CO2. In contrast, the diurnal variations in the soil were relatively small, δ13C varied from -21.6 to -23.4‰, while CO2 concentration from 4300 to 8200 and from 24 700 to 34 500 ppm at depths of 0.1 m and 0.5 m respectively, which is less than 2-fold. Small diurnal variations are characteristic of dry soils, where δ13C is weakly correlated with CO2 concentration (in our case R2 was 0.30 and 0.54, respectively)