70 research outputs found

    The Geoff Egan Memorial Lecture 2011. Artefacts, art and artifice: reconsidering iconographic sources for archaeological objects in early modern Europe

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    A first systematic analysis of historic domestic material culture depicted in contemporaneous Western painting and prints, c.1400-1800. Drawing on an extensive data set, the paper proposes to methodologies and hermeneutics for historical analysis and archaeological correspondence

    A complex geo-scientific strategy for landslide hazard mitigation ? from airborne mapping to ground monitoring

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    International audienceAfter a large landslide event in Sibratsgfäll/Austria several exploration methods were evaluated on their applicability to investigate and monitor landslide areas. The resulting optimised strategy consists of the combined application of airborne electromagnetics, ground geoelectrical measurements and geoelectrical monitoring combined with hydrological and geological mapping and geotechnical modelling. Interdisciplinary communication and discussion was the primary key to assess this complicated hazard situation

    Roche lobe effects on the atmospheric loss of "Hot Jupiters"

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    Observational evidence of a hydrodynamically evaporating upper atmosphere of HD209458b (Vidal-Madjar et al. 2003; 2004) and recent theoretical studies on evaporation scenarios of ``Hot Jupiters'' in orbits around solar-like stars with the age of the Sun indicate that the upper atmospheres of short-periodic exoplanets experience hydrodynamic blow-off conditions resulting in loss rates of the order of about 10^10 - 10^12 g s^-1 (Lammer et al. 2003; Yelle 2004; Baraffe et al. 2004; Lecavlier des Etangs et al. 2004; Jaritz et al. 2005, Tian et al. 2005; Penz et al. 2007). By studying the effect of the Roche lobe on the atmospheric loss from short-periodic gas giants we found, that the effect of the Roche lobe can enhance the hydrodynamic evaporation from HD209458b by about 2 and from OGLE-TR-56b by about 2.5 times. For similar exoplanets which are closer to their host star than OGLE-TR-56b, the enhancement of the mass loss can be even larger. Moreover, we show that the effect of the Roche lobe raises the possibility that ``Hot Jupiters'' can reach blow-off conditions at temperatures which are less than expected (< 10000 K) due to the stellar X-ray and EUV (XUV) heating.Comment: 4 pages, 2 figures, submitted to A&

    An RNA-Seq Strategy to Detect the Complete Coding and Non-Coding Transcriptome Including Full-Length Imprinted Macro ncRNAs

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    Imprinted macro non-protein-coding (nc) RNAs are cis-repressor transcripts that silence multiple genes in at least three imprinted gene clusters in the mouse genome. Similar macro or long ncRNAs are abundant in the mammalian genome. Here we present the full coding and non-coding transcriptome of two mouse tissues: differentiated ES cells and fetal head using an optimized RNA-Seq strategy. The data produced is highly reproducible in different sequencing locations and is able to detect the full length of imprinted macro ncRNAs such as Airn and Kcnq1ot1, whose length ranges between 80–118 kb. Transcripts show a more uniform read coverage when RNA is fragmented with RNA hydrolysis compared with cDNA fragmentation by shearing. Irrespective of the fragmentation method, all coding and non-coding transcripts longer than 8 kb show a gradual loss of sequencing tags towards the 3′ end. Comparisons to published RNA-Seq datasets show that the strategy presented here is more efficient in detecting known functional imprinted macro ncRNAs and also indicate that standardization of RNA preparation protocols would increase the comparability of the transcriptome between different RNA-Seq datasets

    Estimation of the XUV radiation onto close planets and their evaporation

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    Context: The current distribution of planet mass vs. incident stellar X-ray flux supports the idea that photoevaporation of the atmosphere may take place in close-in planets. Integrated effects have to be accounted for. A proper calculation of the mass loss rate due to photoevaporation requires to estimate the total irradiation from the whole XUV range. Aims: The purpose of this paper is to extend the analysis of the photoevaporation in planetary atmospheres from the accessible X-rays to the mostly unobserved EUV range by using the coronal models of stars to calculate the EUV contribution to the stellar spectra. The mass evolution of planets can be traced assuming that thermal losses dominate the mass loss of their atmospheres. Methods: We determine coronal models for 82 stars with exoplanets that have X-ray observations available. Then a synthetic spectrum is produced for the whole XUV range (~1-912 {\AA}). The determination of the EUV stellar flux, calibrated with real EUV data, allows us to calculate the accumulated effects of the XUV irradiation on the planet atmosphere with time, as well as the mass evolution for planets with known density. Results: We calibrate for the first time a relation of the EUV luminosity with stellar age valid for late-type stars. In a sample of 109 exoplanets, few planets with masses larger than ~1.5 Mj receive high XUV flux, suggesting that intense photoevaporation takes place in a short period of time, as previously found in X-rays. The scenario is also consistent with the observed distribution of planet masses with density. The accumulated effects of photoevaporation over time indicate that HD 209458b may have lost 0.2 Mj since an age of 20 Myr. Conclusions: Coronal radiation produces rapid photoevaporation of the atmospheres of planets close to young late-type stars. More complex models are needed to explain fully the observations.Comment: Accepted by A&A. 10 pages, 8 figures, 7 Tables (2 online). Additional online material includes 7 pages, 6 figures and 6 tables, all include

    Birth and fate of hot-Neptune planets

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    This paper presents a consistent description of the formation and the subsequent evolution of gaseous planets, with special attention to short-period, low-mass hot-Neptune planets characteristic of μ\mu Ara-like systems. We show that core accretion including migration and disk evolution and subsequent evolution taking into account irradiation and evaporation provide a viable formation mechanism for this type of strongly irradiated light planets. At an orbital distance aa \simeq 0.1 AU, this revised core accretion model leads to the formation of planets with total masses ranging from \sim 14 \mearth (0.044 \mjup) to \sim 400 \mearth (1.25 \mjup). The newly born planets have a dense core of \sim 6 \mearth, independent of the total mass, and heavy element enrichments in the envelope, MZ,env/MenvM_{\rm Z,env}/M_{\rm env} , varying from 10% to 80% from the largest to the smallest planets. We examine the dependence of the evolution of the born planet on the evaporation rate due to the incident XUV stellar flux. In order to reach a μ\mu Ara-like mass (\sim 14 \mearth) after \sim 1 Gyr, the initial planet mass must range from 166 \mearth (\sim 0.52 \mjup) to about 20 \mearth, for evaporation rates varying by 2 orders of magnitude, corresponding to 90% to 20% mass loss during evolution. The presence of a core and heavy elements in the envelope affects appreciably the structure and the evolution of the planet and yields 8\sim 8%-9% difference in radius compared to coreless objects of solar composition for Saturn-mass planets. These combinations of evaporation rates and internal compositions translate into different detection probabilities, and thus different statistical distributions for hot-Neptunes and hot-Jupiters.Comment: 4 figures, accepted for publication in Astronomy and Astrophysic

    Controlled cavity-assisted generation of single and entangled photons in semiconductor quantum dots

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    We propose a scheme, based on a single semiconductor quantum dot inside a microcavity, for the creation of single and entangled photons with controllable waveform. A lateral electric field allows to charge the quantum dot with a single electron, and breaks the usual optical selection rules. Our scheme utilizes cavity-assisted stimulated Raman adiabatic passage (STIRAP) in order to promote the surplus electron from the ground to the excited state, via excitation of a pump pulse and optical coupling to the charged exciton. This transfer is accompanied by a synchronized emission of a single-photon wavepacket, whose waveform can be controlled by the pump pulse. We investigate the influence of phonon scatterings, and show that they allow to reset the single-photon source. Finally, we propose a slight variant of our scheme which would allow for the creation of entangled multi-photon states. All our simulations are performed with realistic quantum dot and cavity parameters, which allows us to argue that our scheme can be implemented with state-of-the-art quantum dots and microcavities
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