8 research outputs found
Tetrathiopyridyl-tetrathiafulvalene-based Cd(II) coordination polymers: one ligand, one metal cation, many possibilities
No full textproduction
No full textInternational audienceOptimization of negative ion sources operated with deuterium may be limited by the lack ofdata on fundamental processes. Insight can be obtained from studies focusing on a directcomparison of H2 and D2 plasmas. Herein, the ECR volume negative ion source ‘Prometheus I’operates with both H2 and D2 gases and the properties of the generated plasmas are probed bymeans of electrostatic probe and laser induced photo-detachment. A parametric study, involvingpressure and microwave (2.45 GHz) power variation, reveals similar qualitative trends for mostof the plasma properties in both gases. However, quantitively, differences do exist for the plasmapotential, the electron density and temperature, and the negative ion to electron density ratio.Electron energy distribution functions are thus isotope dependent. Overall, nearly the samemaximal H− and D− negative ion densities are achieved (i.e. 4×109 cm−3). The results areeventually elucidated with respect to the ECR heating mechanism, and the production anddestruction paths of the negative ions
Interactions between timing and transmissibility explain diverse flavivirus dynamics in Fiji
No full text© 2021, The Author(s). Zika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIKV between 2013 and 2017. To identify factors that could explain these differences in dynamics between closely related mosquito-borne flaviviruses, we jointly fit a transmission dynamic model to surveillance, serological and molecular data. We estimate that the observed dynamics of ZIKV were the result of two key factors: strong seasonal effects, which created an ecologically optimal time of year for outbreaks; and introduction of ZIKV after this optimal time, which allowed ZIKV transmission to persist over multiple seasons. The ability to jointly fit to multiple data sources could help identify a similar range of possible outbreak dynamics in other settings.This work was supported by the Medical Research Council MR/N013638/1 to A.D.H. and Wellcome Trust 206250/Z/17/Z to A.J.K
First B-dot measurements in the RAID device, an alternative negative ion source for DEMO neutral beams
No full textAs a new concept of Neutral Beam Injectors (NBI) for DEMO-like reactors, SIPHORE (IRFM, CEA, in France) expects to extract negative deuterium ions and photo-neutralize the accelerated D-. The Swiss Plasma Center (SPC) of EPFL is involved in this project by developing an innovative helicon source, which could provide the adequate D2 negative ion blade-shaped plasma, in terms of density and homogeneity along the axial direction. In the Resonant Antenna Ion Device (RAID), the test bed, a helicon wave is sustained by a resonant antenna plasma source at 13.56 MHz (input power ≤ 10 kW), connected to a cylindrical vacuum chamber (1.5 m long, 0.4 m diameter) and is surrounded by 6 Helmholtz coils, providing a DC magnetic field up to 800 G on axis. To characterize the helicon wave propagation, RAID has been recently equipped with a three-axis magnetic probe (B-dot). The paper describes the RAID experiment and its helicon source, including a 3D characterization of density and temperature, together with the B-dot design and calibration. It presents measurements of helicon wave propagation; in typical H2 plasmas (0.3 Pa), preliminary results show a helicon wave right-handed polarized with a wavelength of approximately 240 mm.SP
Coolie cartography: crossing frontiers through coolitude
No full textFollowing the abolition of Transatlantic slavery, the British introduced a new scheme of labour to replace the former. 'Indian indentureship', as it was referred to, affected nearly 2 million Indian coolies who defied the traditional ban against crossing the kala pani (dark waters) in order to work on plantations in countries such as British Guiana, Trinidad, Malaya, South Africa and Fiji. In effect, the Indian labour: diaspora emerged and established itself across the globe. Despite over 100 years of labouring and contributing to the development of their new homes, the coolies and their descendents still face political, social and cultural marginalization. The aim of this thesis is to explore the consequences of indentureship in various societies through a parallelization of inter-national coolie conditions as represented by writers of the diaspora. The three areas selected for this study are Guyana, Malaysia and Fiji. David Dabydeen (Guyana), K.S.Maniam (Malaysia) and Satendra Nandan (Fiji) all share the impetus to disclose the past as a portal into the present, thereby dismpting normative time, and by implication, a fixed sense of history. However; the most striking similarity between these writers, despite their geographical and social distance, is their literary method which centres on the theory of coolitude. Coolitude was coined by Khal Torabully as a means of recuperating the voiceless coolie, firstly, by re-membering the sea voyage across the kizla pani and secondly, by highlighting the coolie's place in the mosaic of multicultural societies. Chapter 1 details the historical, theoretical and methodical foundations of the thesis. Chapter 2 explores Dabydeen's novels The Counting House and Our Lady of Demerara while Chapter 3 is a detailed study of Maniam's novels The Return and In A Far Country. The final chapter considers Nandan's novel The Wounded Sea and collection of poetry Lines Across Black Waters. Each literary analysis seeks to understand how coolitude, as a means to historically and politically place the coolie in the current world,: links spaces between countries both through a shared colonial history and a common postcolonial condition
Interdigitated conducting tetrathiafulvalene-based coordination networks
No full textAssembly of a novel ethylenedithio-tetrathiafulvalene (EDT-TTF) derivative bearing two adjacent 4-thiopyridyl groups with M(NCS)2 nodes (M = Fe, Co) leads to two isostructural 1D coordination polymers showing an enhancement of their electronic conductivity by six orders of magnitude (10[superscript -6] vs. 10[superscript -12] S cm[superscript -1), upon surface oxidation by iodine and subsequent generation of EDT-TTF-based radicals.National Science Foundation (Award 1122374
Interactions between timing and transmissibility explain diverse flavivirus dynamics in Fiji.
No full textZika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIKV between 2013 and 2017. To identify factors that could explain these differences in dynamics between closely related mosquito-borne flaviviruses, we jointly fit a transmission dynamic model to surveillance, serological and molecular data. We estimate that the observed dynamics of ZIKV were the result of two key factors: strong seasonal effects, which created an ecologically optimal time of year for outbreaks; and introduction of ZIKV after this optimal time, which allowed ZIKV transmission to persist over multiple seasons. The ability to jointly fit to multiple data sources could help identify a similar range of possible outbreak dynamics in other settings
Magnetic field configurational study on a helicon-based plasma source for future neutral beam systems
No full textA helicon-based plasma source is under development and exploration at CEA-IRFM to produce an efficient and dense magnetized plasma column. The final objective of this development is the extraction and acceleration of a blade-like negative ion beam in view of future neutral beam injector systems for fusion reactors. The extraction of a negative ion beam from a magnetized plasma column requires a specific topology of the magnetic confinement, which significantly impacts the plasma parameters and wave propagation along the column. The magnetic confinement under investigation is based on water-cooled internal coils implemented under vacuum along the source (column) axis; these coils are supplied with a high DC current (similar to 1000 A), providing the axial magnetic field (B// similar to 10 mT). Different diagnostics developed in academic laboratories, such as 3D B-dot probes, optical emission spectroscopy and Langmuir probes, have been used for plasma characterization. The paper reports the experimental results obtained under different operating conditions of this particular magnetic confinement.SP
