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See detailHigh-precision CoRoT space photometry and fundamental parameter determination of the B2.5V star HD 48977
Thoul, Anne ULg; Degroote, Pieter; Catala, Claude et al

in Astronomy and Astrophysics (2013), 551

We present the CoRoT light curve of the bright B2.5V star HD 48977 observed during a short run of the mission in 2008, as well as a high-resolution spectrum gathered with the HERMES spectrograph at the ... [more ▼]

We present the CoRoT light curve of the bright B2.5V star HD 48977 observed during a short run of the mission in 2008, as well as a high-resolution spectrum gathered with the HERMES spectrograph at the Mercator telescope. We use several time series analysis tools to explore the nature of the variations present in the light curve. We perform a detailed analysis of the spectrum of the star to determine its fundamental parameters and its element abundances. We find a large number of high-order g-modes, and one rotationally induced frequency. We find stable low-amplitude frequencies in the p-mode regime as well. We conclude that HD 48977 is a new Slowly Pulsating B star with fundamental parameters found to be Teff = 20000 $\pm$ 1000 K and log(g)=4.2 $/pm$ 0.1. The element abundances are similar to those found for other B stars in the solar neighbourhood. HD 48977 was observed during a short run of the CoRoT satellite implying that the frequency precision is insufficient to perform asteroseismic modelling of the star. Nevertheless, we show that a longer time series of this star would be promising for such modelling. Our present study contributes to a detailed mapping of the instability strips of B stars in view of the dominance of g-mode pulsations in the star, several of which occur in the gravito-inertial regime. [less ▲]

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See detailHigh-precision measurements of thermal expansion at cryogenic temperature on stable materials
Roose, Stéphane ULg; Heltzel, Stan

Scientific conference (2011, October 04)

The European Space Agency ESA aspires the exploration of the universe using space-borne infrared telescopes with large aperture operating at cryogenic temperature. The Herschel space telescope is ... [more ▼]

The European Space Agency ESA aspires the exploration of the universe using space-borne infrared telescopes with large aperture operating at cryogenic temperature. The Herschel space telescope is currently returning its first scientific observations orbiting from the Lagrange point L2 and the foreseen infrared observatory Spica is currently under study. The large diameter of the primary mirrors and the operation at cryogenic temperature require the use of ultra stable materials and wellcharacterised dimensional change of the structure as function of temperature. Dimensional stability and high precision data on the thermal expansion is also relevant for the cryogenic spectographs MIRI and NIRspec on the James Webb Space Telescope JWST, for high-precision laser interferometer LISA and for spacecraft sent to a hot environment such as BepiColombo and Solar Orbiter. Although European industry has proven effective at designing and building thermally stable structures, problems have been encountered in measuring the absolute CTE of stable materials. In one recent mission, the design CTE had to be changed 6 times over a 2 year period and when the telescope was tested in cryogenic conditions, an error was found in the back focal plane of over a centimetre. It is an objective of ESA to determine the CTE of stable materials continuously as function of temperature with an uncertainty of 3 ppb/K down to a temperature of 5 K. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - I. The transiting planetary system WASP-5
Southworth, John; Hinse, T. C.; Jørgensen, U. G. et al

in Monthly Notices of the Royal Astronomical Society (2009), 396

We present high-precision photometry of two transit events of the extrasolar planetary system WASP-5, obtained with the Danish 1.54-m telescope at European Southern Obseratory La Silla. In order to ... [more ▼]

We present high-precision photometry of two transit events of the extrasolar planetary system WASP-5, obtained with the Danish 1.54-m telescope at European Southern Obseratory La Silla. In order to minimize both random and flat-fielding errors, we defocused the telescope so its point spread function approximated an annulus of diameter 40 pixel (16 arcsec). Data reduction was undertaken using standard aperture photometry plus an algorithm for optimally combining the ensemble of comparison stars. The resulting light curves have point-to-point scatters of 0.50mmag for the first transit and 0.59mmag for the second. We construct detailed signal-to-noise ratio calculations for defocused photometry, and apply them to our observations. We model the light curves with the JKTEBOP code and combine the results with tabulated predictions from theoretical stellar evolutionary models to derive the physical properties of the WASP-5 system. We find that the planet has a mass of M[SUB]b[/SUB] = 1.637 +/- 0.075 +/- 0.033M[SUB]Jup[/SUB], a radius of R[SUB]b[/SUB] = 1.171 +/- 0.056 +/- 0.012R [SUB]Jup[/SUB], a large surface gravity of g[SUB]b[/SUB] = 29.6 +/- 2.8ms[SUP]-2[/SUP] and a density of rho[SUB]b[/SUB] = 1.02 +/- 0.14 +/- 0.01rho[SUB]Jup[/SUB] (statistical and systematic uncertainties). The planet's high equilibrium temperature of T[SUB]eq[/SUB] = 1732 +/- 80K makes it a good candidate for detecting secondary eclipses. Based on data collected by Microlensing Network for the Detection of Small Terrestrial Exoplanets (MiNDSTEp) with the Danish 1.54-m telescope at the ESO La Silla Observatory. E-mail: j.k.taylor@warwick.ac.uk â ¡ Royal Society University Research Fellow. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - III. The transiting planetary system WASP-2 star
Southworth, John; Mancini, L.; Novati, S Calchi et al

in Monthly Notices of the Royal Astronomical Society (2010), 408

ABSTRACT We present high-precision photometry of three transits of the extrasolar planetary system WASP-2, obtained by defocusing the telescopes, and achieving scatters of between 0.42 and 0.73 mmag ... [more ▼]

ABSTRACT We present high-precision photometry of three transits of the extrasolar planetary system WASP-2, obtained by defocusing the telescopes, and achieving scatters of between 0.42 and 0.73 mmag versus the best-fitting model. These data are modelled using the JKTEBOP code, and taking into account the light from the recently discovered faint star close to the system. The physical properties of the WASP-2 system are derived using tabulated predictions from five different sets of stellar evolutionary models, allowing both statistical and systematic error bars to be specified. We find the mass and radius of the planet to be M[SUB]b[/SUB] = 0.846 +/- 0.055 +/- 0.023M[SUB]Jup[/SUB] and R[SUB]b[/SUB] = 1.043 +/- 0.029 +/- 0.015R[SUB]Jup[/SUB]. It has a low equilibrium temperature of 1281 +/- 21K, in agreement with a recent finding that it does not have an atmospheric temperature inversion. The first of our transit data sets has a scatter of only 0.42mmag with respect to the best-fitting light-curve model, which to our knowledge is a record for ground-based observations of a transiting extrasolar planetary system. Based on data collected by MiNDSTEp with the Danish 1.54-m telescope at the ESO La Silla Observatory. E-mail: jkt@astro.keele.ac.uk ‡ Royal Society University Research Fellow. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17 b
Southworth, John; Hinse, T. C.; Dominik, M. et al

in Monthly Notices of the Royal Astronomical Society (2012), 426

We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5 mmag per point. Our revised orbital ... [more ▼]

We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5 mmag per point. Our revised orbital period is 4.0 ± 0.6 s longer than previous measurements, a difference of 6.6σ, and does not support the published detections of orbital eccentricity in this system. We model the light curves using the JKTEBOP code and calculate the physical properties of the system by recourse to five sets of theoretical stellar model predictions. The resulting planetary radius, R[SUB]b[/SUB] = 1.932 ± 0.052 ± 0.010 R[SUB]Jup[/SUB] (statistical and systematic errors, respectively), provides confirmation that WASP-17 b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6 R[SUB]Jup[/SUB] are found around comparatively hot (T[SUB]eff[/SUB] > 5900 K) and massive (M[SUB]A[/SUB] > 1.15 M[SUB]&sun;[/SUB]) stars. Chromospheric activity indicators are available for eight of these stars, and all imply a low activity level. The planets have small or zero orbital eccentricities, so tidal effects struggle to explain their large radii. The observed dearth of large planets around small stars may be natural but could also be due to observational biases against deep transits, if these are mistakenly labelled as false positives and so not followed up. Based on data collected by MiNDSTEp with the Danish 1.54-m telescope at the ESO La Silla Observatory.Royal Society University Research Fellow. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - V. WASP-15 and WASP-16
Southworth, John; Mancini, L.; Browne, P. et al

in Monthly Notices of the Royal Astronomical Society (2013), 434

We present new photometric observations of WASP-15 and WASP-16, two transiting extrasolar planetary systems with measured orbital obliquities but without photometric follow-up since their discovery papers ... [more ▼]

We present new photometric observations of WASP-15 and WASP-16, two transiting extrasolar planetary systems with measured orbital obliquities but without photometric follow-up since their discovery papers. Our new data for WASP-15 comprise observations of one transit simultaneously in four optical passbands using GROND on the MPG/European Southern Observatory (ESO) 2.2 m telescope, plus coverage of half a transit from DFOSC on the Danish 1.54 m telescope, both at ESO La Silla. For WASP-16 we present observations of four complete transits, all from the Danish telescope. We use these new data to refine the measured physical properties and orbital ephemerides of the two systems. Whilst our results are close to the originally determined values for WASP-15, we find that the star and planet in the WASP-16 system are both larger and less massive than previously thought. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - VII. The ultrashort period planet WASP-103
Southworth, J.; Mancini, L.; Ciceri, S. et al

in Monthly Notices of the Royal Astronomical Society (2014), 447(1), 711-721

We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision ... [more ▼]

We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision reference epoch for transit timing studies. The time of the reference transit mid-point is now measured to an accuracy of 4.8 s, versus 67.4 s in the discovery paper, aiding future searches for orbital decay. With the help of published spectroscopic measurements and theoretical stellar models, we determine the physical properties of the system to high precision and present a detailed error budget for these calculations. The planet has a Roche lobe filling factor of 0.58, leading to a significant asphericity; we correct its measured mass and mean density for this phenomenon. A high-resolution Lucky Imaging observation shows no evidence for faint stars close enough to contaminate the point spread function of WASP-103. Our data were obtained in the Bessell RI and the SDSS griz passbands and yield a larger planet radius at bluer optical wavelengths, to a confidence level of 7.3σ. Interpreting this as an effect of Rayleigh scattering in the planetary atmosphere leads to a measurement of the planetary mass which is too small by a factor of 5, implying that Rayleigh scattering is not the main cause of the variation of radius with wavelength. © 2014 The Authors. [less ▲]

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See detailHigh-precision photometry by telescope defocussing - II. The transiting planetary system WASP-4
Southworth, John; Hinse, T. C.; Burgdorf, M. J. et al

in Monthly Notices of the Royal Astronomical Society (2009)

We present and analyse light curves of four transits of the Southern hemisphere extrasolar planetary system WASP-4, obtained with a telescope defocused so the radius of each point spread function was 17 ... [more ▼]

We present and analyse light curves of four transits of the Southern hemisphere extrasolar planetary system WASP-4, obtained with a telescope defocused so the radius of each point spread function was 17 arcsec (44 pixels). This approach minimizes both random and systematic errors, allowing us to achieve scatters of between 0.60 and 0.88 mmag per observation over complete transit events. The light curves are augmented by published observations and analysed using the JKTEBOP code. The results of this process are combined with theoretical stellar model predictions to derive the physical properties of the WASP-4 system. We find that the mass and radius of the planet are M[SUB]b[/SUB] = 1.289[SUP]+0.090[/SUP][SUB]-0.090[/SUB][SUP]+0.039[/SUP][SUB]-0.000[/SUB]M[SUB]Jup[/SUB] and R[SUB]b[/SUB] = 1.371[SUP]+0.032[/SUP][SUB]-0.035[/SUB][SUP]+0.021[/SUP][SUB]-0.000[/SUB]R[SUB]Jup[/SUB], respectively (statistical and systematic uncertainties). These quantities give a surface gravity and density of g[SUB]b[/SUB] = 17.03[SUP]+0.97[/SUP][SUB]-0.54[/SUB]ms[SUP]-2[/SUP] and rho[SUB]b[/SUB] = 0.500[SUP]+0.032[/SUP][SUB]-0.021[/SUB][SUP]+0.000[/SUP][SUB]-0.008[/SUB] rho[SUB]Jup[/SUB], and fit the trends for short-period extrasolar planets to have relatively high masses and surface gravities. WASP-4 is now one of the best-quantified transiting extrasolar planetary systems, and significant further progress requires improvements to our understanding of the physical properties of low-mass stars. Based on data collected by MiNDSTEp with the Danish 1.54m telescope at the ESO La Silla Observatory. E-mail: jkt@astro.keele.ac.uk â ¡ Royal Society University Research Fellow. [less ▲]

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See detailHigh-precision photometry by telescope defocussing - VI. WASP-24, WASP-25 andWASP-26*
Southworth, J.; Hinse, T. C.; Burgdorf, M. et al

in Monthly Notices of the Royal Astronomical Society (2014), 444(1), 776-789

We present time series photometric observations of 13 transits in the planetary systems WASP-24, WASP-25 and WASP-26. All three systems have orbital obliquity measurements, WASP-24 andWASP-26 have been ... [more ▼]

We present time series photometric observations of 13 transits in the planetary systems WASP-24, WASP-25 and WASP-26. All three systems have orbital obliquity measurements, WASP-24 andWASP-26 have been observed with Spitzer, andWASP-25 was previously comparatively neglected. Our light curves were obtained using the telescope-defocussing method and have scatters of 0.5-1.2 mmag relative to their best-fitting geometric models. We use these data to measure the physical properties and orbital ephemerides of the systems to high precision, finding that our improved measurements are in good agreement with previous studies. High-resolution Lucky Imaging observations of all three targets show no evidence for faint stars close enough to contaminate our photometry. We confirm the eclipsing nature of the star closest to WASP-24 and present the detection of a detached eclipsing binary within 4.25 arcmin of WASP-26. © 2014 The Authors. [less ▲]

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See detailHigh-Precision Spectroscopy of Pulsating Stars
Aerts, C.; Hekker, S.; Desmet, M. et al

in Precision Spectroscopy in Astrophysics, Proceedings of the ESO/Lisbon/Aveiro Conference held in Aveiro, Portugal, 11-15 September 2006. (2008)

We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We ... [more ▼]

We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the past two decades. This has led to the opportunity to interprete line-profile variations with amplitudes of order m/s, which is a factor 1000 lower than the earliest line-profile time series studies allowed for. [less ▲]

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See detailHigh-pressure study of the beta-to-alpha transition in Ga2O3
Machon, D.; McMillan, P. F.; Xu, Bin ULg et al

in Physical Review. B, Condensed Matter and Materials Physics (2006), 73(9),

The high-pressure behavior of Ga2O3 is studied up to 40 GPa using synchrotron x-ray diffraction and Raman spectroscopy in diamond anvil cells. A phase transformation from the monoclinic beta-phase (C2/m ... [more ▼]

The high-pressure behavior of Ga2O3 is studied up to 40 GPa using synchrotron x-ray diffraction and Raman spectroscopy in diamond anvil cells. A phase transformation from the monoclinic beta-phase (C2/m) is observed at a pressure above 20-22 GPa. The high-pressure polymorph is identified as the alpha-phase that is isostructural with corundum (R (3) over barc symmetry) from the x-ray diffraction data. However, considerable anion disorder is indicated by the appearance of broad bands in the Raman spectra. The experimental results are complemented by ab initio theoretical calculations of the energetics of the two structures and the lattice dynamics. [less ▲]

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See detailHigh-quality remeshing using harmonic maps
Geuzaine, Christophe ULg; Marchandise, E.; Remacle, J.-F.

in Proceedings of the 5th Advanced Computational Electromagnetics workshop (2010, July)

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See detailHigh-Quality Remeshing using Harmonic Maps
Geuzaine, Christophe ULg

Scientific conference (2010, March 30)

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See detailHigh-Quality Surface Remeshing Using Harmonic Maps
Remacle, J.-F.; Geuzaine, Christophe ULg; Compère, G. et al

in International Journal for Numerical Methods in Engineering (2010), 83(4), 403-425

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See detailHigh-quality thin graphene films from fast electrochemical exfoliation
Aqil, Abdelhafid ULg; Ouhib, Farid ULg; Detrembleur, Christophe ULg et al

Poster (2013, November)

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and ... [more ▼]

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and simple electrografting acrylate monomer method to exfoliate highly oriented pyrolytic graphite (HOPG) into thin nanoplatelets and even down to the single graphene sheet level. Among the high research activity in the area of surface modification, electrografting is a very powerful method which has received comparatively little attention. This is surprising because this technique has many attractive features for modification of conducting or semi-conducting surfaces. The main interest of the electrografting process is to solve the recurrent problem of the organic/substrates interface weakness. The electrografting warranties a robust polymer/substrates interface and offers the possibility to tailor the functionality of the grafted polymer film opening the door to a wide range of demanding technological applications. The graphene sheets obtained through electrografting process give a stable suspension in dimethyl formamide (DMF), and they can self-precipitate on the surface of substrates after adding water as an antisolvent due to their strong surface hydrophobicity. Interestingly, the continuous films obtained exhibit ultratransparency (∼98% transmittance), and the lateral size of the exfoliated graphene sheets observed by AFM ~1nm. Raman and TEM characterizations corroborate that the graphene sheets exfoliated by our electrochemical method preserve the intrinsic structure of grapheme and give preferentially monolayered graphene sheets. The electrochemical behaviour of the acrylate monomer grafted graphene sheets was evaluated in lithium-half cells with no addition of conductive additive or binder. The PAN grafted graphene dispersed in DMF was coated on Cu foil and dried in a vacuum oven at 55°C for 12h. After 200 cycles, the reversible capacity was still kept at 300mAh/g at the current density of 50mA/g. These results indicate that the prepared high quality graphene sheets possess good electrochemical performances for lithium storage. This work provides an efficient approach to obtain high-quality, cost-effective, and scalable production of “graphene ink”, which may pave a way toward future applications in lithium- ion batteries. [less ▲]

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See detailHigh-rate of multiple genital HPV infections detected by DNA hybridization
Lauricella-Lefèbvre, M. A.; Piette, Jacques ULg; Lifrange, Eric ULg et al

in Journal of Medical Virology (1992), 36(4), 265-270

Cervical smears collected from 450 patients involved in a clinical follow-up of cervical human papillomaviruses (HPV) infections were screened for the presence of HPV 6b, 11, 16, and 18 DNA by both dot ... [more ▼]

Cervical smears collected from 450 patients involved in a clinical follow-up of cervical human papillomaviruses (HPV) infections were screened for the presence of HPV 6b, 11, 16, and 18 DNA by both dot blot and southern blot hybridization methods. Using very high stringency hybridization assays, the four HPV types could be easily distinguished by dot blotting. After a preliminary clinical sorting, 42.9% of the samples were found to be HPV-positive. Among the samples infected by a single HPV, type 16 was the most frequent (25.4% of the positive samples) followed by 6b (19.7%), 11 (8.3%), and 18 (7.2%). Double or even multiple infections by the different HPV types were detected at a very high rate (39.4% of the positive samples). [less ▲]

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See detailHigh-resolution Climatology of the North-East Atlantic using Data-Interpolating Variational Analysis
Troupin, Charles ULg; Machín, Francisco; Ouberdous, Mohamed ULg et al

Conference (2009, April 21)

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See detailHigh-resolution Climatology of the northeast Atlantic using Data-Interpolating Variational Analysis (DIVA)
Troupin, Charles ULg; Machin, Francis; Ouberdous, Mohamed ULg et al

in Journal of Geophysical Research (2010), 115(C08005), 20

Numerous climatologies are available at different resolutions and cover various parts of the global ocean. Most of them have a resolution too low to represent suitably regional processes and the methods ... [more ▼]

Numerous climatologies are available at different resolutions and cover various parts of the global ocean. Most of them have a resolution too low to represent suitably regional processes and the methods for their construction are not able to take into account the influence of physical effects (topographic constraints, boundary conditions, advection, etc.). A high-resolution atlas for temperature and salinity is developed for the northeast Atlantic Ocean on 33 depth levels. The originality of this climatology is twofold: (1) For the data set, data are collected on all major databases and aggregated to lead to an original data collection without duplicates, richer than the World Ocean Database 2005, for the same region of interest. (2) For the method, climatological fields are constructed using the variational method Data-Interpolating Variational Analysis. The formulation of the latter allows the consideration of coastlines and bottom topography, and has a numerical cost almost independent on the number of observations. Moreover, only a few parameters, determined in an objective way, are necessary to perform an analysis. The results show overall good agreement with the widely used World Ocean Atlas, but also reveal significant improvements in coastal areas. Error maps are generated according to different theories and emphasize the importance of data coverage for the creation of such climatological fields. Automatic outlier detection is performed, and its effects on the analysis are examined. The method presented here is very general and not dependent on the region, hence it may be applied for creating other regional atlas in different zones of the global ocean. [less ▲]

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See detailHigh-resolution clutter-power estimation for range-dependence compensation in conformal-array STAP
Ries, Philippe; Lapierre, Fabian D.; Lesturgie, Marc et al

Conference (2008)

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See detailHigh-resolution diatom/clay record in Lake Baikal from grey scale, and magnetic susceptibility over Holocene and Termination I
Boes, Xavier; Piotrowska, Natalia; Fagel, Nathalie ULg

in Global and Planetary Change (2005), 46(1-4), 299-313

Tracing past climate signals from Lake Baikal sediments with a "multi-annual' resolution by conventional techniques is a difficult challenge since the sedimentation rates from Termination I up to the ... [more ▼]

Tracing past climate signals from Lake Baikal sediments with a "multi-annual' resolution by conventional techniques is a difficult challenge since the sedimentation rates from Termination I up to the present range from 0.004 to 0.17 mm/year. In this paper, climate signals are reconstructed from three continuous sediment records from Vydrino Shoulder and Posolsky Bank in the Southern Basin, and Continent Ridge in the Northern Basin. For each coring site, a calendar age model was constructed using calibrated radiocarbon ages. The magnetic susceptibility is used to better constrain the age models over OIS4 to OIS1 The cores have been hardened using polymerized technique in order to allow the easy cut of thin sections that contain evidence for narrow biogenic/clayey laminations. The grey scale taken from the thin sections is used here as a high-resolution proxy record of diatom/clay ratio. The grey density values are qualitatively interpreted against the sediment components by optical microscopy from the thin sections. In the Northern Basin, the Continent station provides the best age model and sediment resolution over the Termination I period. In particular, four optima (i.e. Bolling, Allerod, Atlantic, and Subboreal) are indicated by substantial increases of the grey scale, whereas cold periods like the Younger Dryas correspond to lower grey scale values. We emphasize that the short-term variations in the grey scale at 20 mu m resolution could correspond to short climate responses in Lake Baikal sediments. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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