Sine-Gordon theory for the equation of state of classical hard-core Coulomb systems. II. High-temperature expansion

We perform a high-temperature expansion of the grand potential of the restrictive primitive model of electrolytes in the frame of the extended sine-Gordon theory exposed in the companion paper. We recover a result already obtained by Stell an Lebowitz (J. Chem. Phys., 49, 3706 (1968)) by means of diagrammatic expansions

Periodic formation and propagation of double layers in the expanding chamber of an inductive discharge operating in Ar/SF₆ mixtures

It has previously been shown [Tuszewski et al., Plasma Sources Sci. Technol.12, 396 (2003)] that inductive discharges in electronegative gases are subject to two types of instability: the sourceinstability related to the E to H transition and a transport instability, occurring downstream when an expanding chamber is present. These two types of instability are observed in our “helicon” reactor operated without a static magnetic field in low-pressure Ar∕SF6 mixtures. Temporally and spatially resolved measurements show that, in our experiment, the downstream instability is a periodic formation and propagation of a double layer. The double layer is born at the end of the source tube and propagates slowly to the end of the expansion region with a velocity of 150ms⁻¹

Nitrous oxide distribution and its origin in the central and eastern South Pacific Subtropical Gyre

The mechanisms of microbial nitrous oxide (N<sub>2</sub>O) production in the ocean have been the subject of many discussions in recent years. New isotopomeric tools can further refine our knowledge of N<sub>2</sub>O sources in natural environments. This study compares hydrographic, N<sub>2</sub>O concentration, and N<sub>2</sub>O isotopic and isotopomeric data from three stations along a coast-perpendicular transect in the South Pacific Ocean, extending from the center (Sts. GYR and EGY) of the subtropical oligotrophic gyre (~26° S; 114° W) to the upwelling zone (St. UPX) off the central Chilean coast (~34° S). Although AOU/N<sub>2</sub>O and NO<sub>3</sub><sup>−</sup> trends support the idea that most of the N<sub>2</sub>O (mainly from intermediate water (200–600 m)) comes from nitrification, N<sub>2</sub>O isotopomeric composition (intramolecular distribution of <sup>15</sup>N isotopes) expressed as SP (site preference of <sup>15</sup>N) shows low values (10 to 12permil) that could be attributed to the production through of microbial nitrifier denitrification (reduction of nitrite to N<sub>2</sub>O mediated by ammonium oxidizers). The coincidence of this SP signal with high – stability layer, where sinking organic particles can accumulate, suggests that N<sub>2</sub>O could be produced by nitrifier denitrification inside particles. It is postulated that deceleration of particles in the pycnocline can modify the advection - diffusion balance inside particles, allowing the accumulation of nitrite and O<sub>2</sub> depletion suitable for nitrifier denitrication. As lateral advection seems to be relatively insignificant in the gyre, in situ nitrifier denitrification could account for 40–50% of the N<sub>2</sub>O produced in this layer. In contrast, coastal upwelling system is characterized by O<sub>2</sub> deficient condition and some N deficit in a eutrophic system. Here, N<sub>2</sub>O accumulates up to 480% saturation, and isotopic and isotopomer signals show highly complex N<sub>2</sub>O production processes, which presumably reflect both the effect of nitrification and denitrification at low O<sub>2</sub> levels on N<sub>2</sub>O production, but net N<sub>2</sub>O consumption by denitrification was not observed

Equilibrium model for two low-pressure electronegative plasmas connected by a double layer

Plihon et al. [J. Appl. Phys.98, 023306 (2005)] have recently shown that double layers usually form during the expansion of a low pressure electronegative plasma. These double layers act as permeable internal boundaries between the source (upstream) plasma and the downstream expanding plasma; positive ions flow from upstream to downstream whereas negative ions flow in the opposite direction. So far, the detailed physical mechanisms leading to their formation have not been identified. In this paper, we develop a model for the two plasma equilibria, upstream and downstream, assuming that the double layer exists and couples the two plasmas. At very low pressure, typically 0.5mTorr, the coupling is strong and acts both ways. The negative ions created downstream contributes to the upstream equilibrium as well as the upstream positive ions contribute to the downstream equilibrium. As the pressure increases, the situation becomes asymmetric. The sourceplasma is not affected by the negative ions flowing from downstream, whereas the positive ions coming from the source control the downstream plasma equilibrium, where local ionization is negligible.This work has been supported by the European Space Agency, under Ariadna Study Contract No. ACT-04-3101. One of the authors A.J.L. acknowledges the hospitality of the LPTP, where the collaboration was begun

Ecology and biogeochemistry of contrasting trophic environments in the South East Pacific by carbon isotope ratios on lipid biomarkers

International audienceThe distribution of lipid biomarkers and their carbon isotope composition was investigated on suspended particles from different contrasting trophic environments at six sites in the South East Pacific. High algal biomass with diatom-related lipids was characteristic in the upwelling zone, whereas haptophyte lipids were proportionally most abundant in the nutrient-poor settings of the centre of the South Pacific Gyre and on its easter edge. Dinoflagellate–sterols were minor contributors in all of the studied area and cyanobacteria-hydrocarbons were at maximum in the high nutrient low chlorophyll regime of the subequatorial waters at near the Marquesas archipelago. The taxonomic and spatial variability of the relationships between carbon photosynthetic fractionation and environmental conditions for four specific algal taxa (diatoms, haptophytes, dinoflagellates and cyanobacteria) was also investigated. The carbon isotope fractionation factor (ep) of the diatom marker varied over a range of 16‰ along the different trophic systems. In contrast, ep of dinoflagellate, cyanobacteria and alkenone markers varied only by 7–10‰. The low fractionation factors and small variations between the different phytoplankton markers measured in the upwelling area likely reveals uniformly high specific growth rates within the four phytoplankton taxa, and/or that transport of inorganic carbon into phytoplankton cells may not only occur by diffusion but by other carbon concentrating mechanisms (CCM). In contrast, in the oligotrophic zone, i.e. gyre and eastgyre, relatively high ep values, especially for the diatom marker, indicate diffusive CO2 uptake by the eukaryotic phytoplankton. At these nutrient-poor sites, the lowest ep values for haptophytes, dinoflagellates and cyanobacteria infer higher growth rates compared to diatoms

Collective modes in uniaxial incommensurate-commensurate systems with the real order parameter

The basic Landau model for uniaxial systems of the II class is nonintegrable, and allows for various stable and metastable periodic configurations, beside that representing the uniform (or dimerized) ordering. In the present paper we complete the analysis of this model by performing the second order variational procedure, and formulating the combined Floquet-Bloch approach to the ensuing nonstandard linear eigenvalue problem. This approach enables an analytic derivation of some general conclusions on the stability of particular states, and on the nature of accompanied collective excitations. Furthermore, we calculate numerically the spectra of collective modes for all states participating in the phase diagram, and analyze critical properties of Goldstone modes at all second order and first order transitions between disordered, uniform and periodic states. In particular it is shown that the Goldstone mode softens as the underlying soliton lattice becomes more and more dilute.Comment: 19 pages, 16 figures, REVTeX, to be published in Journal of Physics A: Mathematical and Genera

Development and testing of Indoor Soundscape Questionnaire for evaluating contextual experience in public spaces

An Indoor Soundscape Questionnaire aiming at the evaluation of indoor public sound environments was designed, statistically tested and presented. It was established through initial pilot studies and three main factors under contextual experience variable are established as (1) psychological factors, (2) space usage factors and (3) demographical factors. In addition to the questions on demographical and space usage factors, detailed questions on psychological factors are designed and statistically tested for expectation, perception and reaction categories of the psychological factor. The questionnaire was applied as part of a case study in enclosed library foyer environments to a group of 270 participants through non-experimental survey data sampling. The reliability and validity scores of the Indoor Soundscape Questionnaire were statistically tested and confirmed. Furthermore, statistical tests were used to derive relationships between contextual experience variables of psychological, space usage and demographical factors. Chi-square test of goodness-of-fit results showed statistical significances of demographical and space usage factors with the psychological factors

Magnetic field stabilization for high-accuracy mass measurements on exotic nuclides

The magnetic-field stability of a mass spectrometer plays a crucial role in precision mass measurements. In the case of mass determination of short-lived nuclides with a Penning trap, major causes of instabilities are temperature fluctuations in the vicinity of the trap and pressure fluctuations in the liquid helium cryostat of the superconducting magnet. Thus systems for the temperature and pressure stabilization of the Penning trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN have been installed. A reduction of the fluctuations by at least one order of magnitude downto dT=+/-5mK and dp=+/-50mtorr has been achieved, which corresponds to a relative frequency change of 2.7x10^{-9} and 1.5x10^{-10}, respectively. With this stabilization the frequency determination with the Penning trap only shows a linear temporal drift over several hours on the 10 ppb level due to the finite resistance of the superconducting magnet coils.Comment: 23 pages, 13 figure