Investigation of laser ablated ZnO thin films grown with Zn metal target: a structural study

High quality ZnO thin films were gown using the pulsed laser deposition technique on (0001) Al$_2$O$_3$ substrates in an oxidizing atmosphere, using a Zn metallic target. We varied the growth conditions such as the deposition temperature and the oxygen pressure. First, using a battery of techniques such as x-rays diffraction, Rutherford Backscattering spectroscopy and atomic force microscopy, we evaluated the structural quality, the stress and the degree of epitaxy of the films. Second, the relations between the deposition conditions and the structural properties, that are directly related to the nature of the thin films, are discussed qualitatively. Finally, a number of issues on how to get good-quality ZnO films are addressed.Comment: To be published in Jour. Appl. Phys. (15 August 2004

Individual and collective behavior of dust particles in a protoplanetary nebula

We study the interaction between gas and dust particles in a protoplanetary disk, comparing analytical and numerical results. We first calculate analytically the trajectories of individual particles undergoing gas drag in the disk, in the asymptotic cases of very small particles (Epstein regime) and very large particles (Stokes regime). Using a Boltzmann averaging method, we then infer their collective behavior. We compare the results of this analytical formulation against numerical computations of a large number of particles. Using successive moments of the Boltzmann equation, we derive the equivalent fluid equations for the average motion of the particles; these are intrinsically different in the Epstein and Stokes regimes. We are also able to study analytically the temporal evolution of a collection of particles with a given initial size-distribution provided collisions are ignored.Comment: 15 pages, 9 figures, submitted to Ap

Detection of CO and HCN in Pluto's atmosphere with ALMA

Observations of the Pluto-Charon system, acquired with the ALMA interferometer on June 12-13, 2015, have yielded a detection of the CO(3-2) and HCN(4-3) rotational transitions from Pluto, providing a strong confirmation of the presence of CO, and the first observation of HCN, in Pluto's atmosphere. The CO and HCN lines probe Pluto's atmosphere up to ~450 km and ~900 km altitude, respectively. The CO detection yields (i) a much improved determination of the CO mole fraction, as 515+/-40 ppm for a 12 ubar surface pressure (ii) clear evidence for a well-marked temperature decrease (i.e., mesosphere) above the 30-50 km stratopause and a best-determined temperature of 70+/-2 K at 300 km, in agreement with recent inferences from New Horizons / Alice solar occultation data. The HCN line shape implies a high abundance of this species in the upper atmosphere, with a mole fraction >1.5x10-5 above 450 km and a value of 4x10-5 near 800 km. The large HCN abundance and the cold upper atmosphere imply supersaturation of HCN to a degree (7-8 orders of magnitude) hitherto unseen in planetary atmospheres, probably due to the slow kinetics of condensation at the low pressure and temperature conditions of Pluto's upper atmosphere. HCN is also present in the bottom ~100 km of the atmosphere, with a 10-8 - 10-7 mole fraction; this implies either HCN saturation or undersaturation there, depending on the precise stratopause temperature. The HCN column is (1.6+/-0.4)x10^14 cm-2, suggesting a surface-referred net production rate of ~2x10^7 cm-2s-1. Although HCN rotational line cooling affects Pluto's atmosphere heat budget, the amounts determined in this study are insufficient to explain the well-marked mesosphere and upper atmosphere's ~70 K temperature. We finally report an upper limit on the HC3N column density (< 2x10^13 cm-2) and on the HC15N / HC14N ratio (< 1/125).Comment: Revised version. Icarus, in press, Oct. 11, 2016. 57 pages, including 13 figures and 4 table

Thermal regime of the Southeast Indian Ridge between 88°E and 140°E: Remarks on the subsidence of the ridge flanks

International audienceThe flanks of the Southeast Indian Ridge are characterized by anomalously low subsidence rates for the 0–25 Ma period: less than 300 m Ma−1/2 between 101°E and 120°E and less than 260 m Ma−1/2 within the Australian-Antarctic Discordance (AAD), between 120°E and 128°E. The expected along-axis variation in mantle temperature (∼50°C) is too small to explain this observation, even when the temperature dependence of the mantle physical properties is accounted for. We successively analyze the effect on subsidence of different factors, such as variations in crustal thickness; the dynamic contribution of an old, detached slab supposedly present within the mantle below the AAD; and depletion in ϕ m, a parameter here defined as the “ubiquitously distributed melt fraction” within the asthenosphere. These effects may all contribute to the observed, anomalously low subsidence rate of the ridge flanks, with the most significant contribution being probably related to the depletion in ϕ m. However, these effects have a deep-seated origin that cannot explain the abruptness of the transition across the fracture zones that delineate the boundaries of the AAD, near 120°E and near 128°E, respectively

Contents : Chiba Medical Journal Volume 92 Number 1 , Fabruary 2016

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The Exomars Climate Sounder (EMCS) Investigation

The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA. EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind

Engineering the magnetic and magnetocaloric properties of PrVO3 epitaxial oxide thin films by strain effects

Combining multiple degrees of freedom in strongly-correlated materials such as transition-metal oxides would lead to fascinating magnetic and magnetocaloric features. Herein, the strain effects are used to markedly tailor the magnetic and magnetocaloric properties of PrVO3 thin films. The selection of appropriate thickness and substrate enables us to dramatically decrease the coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to 0.05 T for compressive thin films making from the PrVO3 compound a nearly soft magnet. This is associated with a marked enhancement of the magnetic moment and the magnetocaloric effect that reach unusual maximum values of roughly 4.86 uB and 56.8 J/kg K in the magnetic field change of 6 T applied in the sample plane at the cryogenic temperature range (3 K), respectively. This work strongly suggests that taking advantage of different degrees of freedom and the exploitation of multiple instabilities in a nanoscale regime is a promising strategy for unveiling unexpected phases accompanied by a large magnetocaloric effect in oxides.Comment: This paper is accepted for publication in Applied Physics Letter

Determining the instar of a weevil larva (Coleoptera: Curculionidae) using a parsimonious method

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The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described