References of "Mahieu, Emmanuel"
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See detailPolar stratospheric descent of NOy and CO and Arctic denitrification during winter 1992-1993
Rinsland, C. P.; Salawitch, R. J.; Gunson, M. R. et al

in Journal Of Geophysical Research. Atmospheres (1999), 104(D1), 1847-1861

Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform ... [more ▼]

Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer are reported. In both instances, elevated volume mixing ratios (VMRs) of carbon monoxide (CO) were measured. A peak Antarctic CO VMR of 60 ppbv (where 1 ppbv = 10(-9) per unit volume) was measured at a potential temperature (Theta) of 710 K (similar to 27 km), about 1 km below the altitude of a pocket of elevated NOy (total reactive nitrogen) at a deep minimum in N2O (<5 ppbv). The Arctic observations also show a region of elevated vortex CO with a peak VMR of 90 ppbv at 630-670 K (similar to 25 km) but no corresponding enhancement in NOy, perhaps because of stronger dynamical activity in the northern hemisphere polar winter and/or interannual variability in the production of mesospheric NO. By comparing vortex and extravortex observations of NOy obtained at the same N2O VMR, Arctic vortex denitrification of 5 +/- 2 ppbv at 470 K (similar to 18 km) is inferred. We show that our conclusion of substantial Arctic winter 1992-1993 denitrification is robust by comparing our extravortex observations with previous polar measurements obtained over a wide range of winter conditions. Correlations of NOy with N2O measured at the same Theta by ATMOS in the Arctic vortex and at midlatitudes on board the ER-2 aircraft several weeks later lie along the same mixing line. The result demonstrates the consistency of the two data sets and confirms that the ER-2 sampled fragments of the denitrified Arctic vortex following its breakup, An analysis of the ATMOS Arctic measurements of total hydrogen shows no evidence for significant dehydration inside the vortex. [less ▲]

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See detailVertical column abundances of COF2 above the Jungfraujoch Station: update and consolidation of the database with measurements in the nu4 band region.
Mélen, Francine; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

in Atmospheric Spectroscopy Applications 1999 - Proceedings (1999)

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See detailColumn Abundance measurements of formaldehyde above the Jungfraujoch.
Demoulin, Philippe ULg; Zander, Rodolphe ULg; Mélen, F. et al

in Atmospheric Spectroscopy Applications 1999 - Proceedings (1999)

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See detailRecent Characteristic Budgets of Inorganic Chlorine and Fluorine above the Jungfraujoch Station
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Mélen, Francine et al

in Harris, N. R. P.; Kilbane-Dawe, I.; Amanatidis, G.T. (Eds.) Proceedings of the 4th European Symposium on Polar Stratospheric Ozone 1997 (1998)

Within the frame of NDSC (Network for the Detection of Stratospheric Change)-related monitoring activities conducted at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E ... [more ▼]

Within the frame of NDSC (Network for the Detection of Stratospheric Change)-related monitoring activities conducted at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m a.s.l.), long-term investigations of the inorganic chlorine and fluorine budgets have been pursued during the last years. They are based on the analysis of high-resolution infrared solar spectra, recorded with grating and Fourier transform state-of-the-art spectrometers. Nonlinear least squares fittings of synthetic spectra to the observations are performed over selected intervals, encompassing characteristic absorptions of HCl, ClONO2, HF and COF2; this allows the retrieval of their total vertical column abundances above the Jungfraujoch and the evaluation of their budgets. [less ▲]

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See detailObservations coupled to the overpasses of the polar vortex over mid-latitude Europe in winter 1995-1996
Hennen, Olivier; De Mazière, Martine; Van Roozendael, Michel et al

in Harris, N. R. P.; Kilbane-Dawe, I.; Amanatidis, G.T. (Eds.) Polar stratospheric ozone 1997 (1998)

The spring 1996 polar vortex was very deep and cold, with temperatures down to the ice formation threshold, and persisted until March. The northern hemisphere ozone decrease in winter 1995-1996 was larger ... [more ▼]

The spring 1996 polar vortex was very deep and cold, with temperatures down to the ice formation threshold, and persisted until March. The northern hemisphere ozone decrease in winter 1995-1996 was larger than ever before in the nineties. Particularly at the European mid-latitudes, transport of air masses from the polar vortex towards mid-latitudes had a noticeable impact on the stratospheric temperatures and composition. Such was not observed that clearly in the latest winter 1996-1997. In this work, signatures of polar vortex overpasses in spring 1996 at several European mid-latitude stations are indicated. Most significant events have been observed at these stations with a delay of one to four days, on the following days: 18-22/1, 14-20/2, 1-6/3, 29/3, 15-17/4. The focus here will be on the two events in March. [less ▲]

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See detailGround-based FTIR Measurements from a Series of European sites during the Winter of 1995/96 and a Comparison with a 3D Chemical Transport Model: Evidence of Chlorine Activation and Ozone depletion
Paton Walsh, C.; Bell, W.; Blumenstock, T. et al

in Harris, N. R. P.; Kilbane-Dawe, I.; Amanatidis, G.T. (Eds.) Polar stratospheric ozone 1997 (1998)

Fourier transform infra-red (FTIR) measurements of stratospheric trace species have been made at a network of five ground-based sites from 79°N to 47°N during the Northern hemisphere winter of 1995/1996 ... [more ▼]

Fourier transform infra-red (FTIR) measurements of stratospheric trace species have been made at a network of five ground-based sites from 79°N to 47°N during the Northern hemisphere winter of 1995/1996. This winter was extremely cold with temperatures below the threshold for type 1 polar stratospheric cloud (PSC) formation from mid December 1995 until early March 1996 when there was a rapid warming of the stratosphere. Over 25 days experienced temperatures low enough for ice cloud (PSC type 2) formation. Vertical columns values for HCl, ClONO2, HF and HNO3 have been derived from FTIR measurements at the following sites: Ny Alesund, Spitzbergen (79°N, 12°E); Kiruna, Sweden (67°N, 21°E); Harestua, Norway (60°N, 11°E); London, England (51°N, 0°E) and the Jungfraujoch, Switzerland (48°N, 8°E), with measurements of other stratospheric trace gases, including O3 and ClO available from some of the sites. All of these sites are equipped with high resolution Bruker 120HR or 120M spectrometers, recording atmospheric spectra in the mid infrared using the Sun as a source. These measurements have been used to provide both evidence of substantial activation within large areas of the polar vortex and a subsequent O3 depletion. The measurements suggest a well mixed central vortex area surrounded by a vortex edge that may be highly variable in composition. The measurements also provide evidence of substantial mixing of activated air from the edge of the polar vortex into middle latitudes. Comparison with the SLIMCAT 3D chemical transport model highlights the underestimation of ClONO2 concentrations in the model, with subsequent implications for underestimating O3 loss. [less ▲]

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See detailThe current budget of NOy above the Jungfraujoch as derived from IR solar observations
Demoulin, Philippe ULg; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Harris, N. R. P.; Kilbane-Dawe, I.; Amanatidis, G. T. (Eds.) Polar stratospheric ozone 1997 (1998)

This paper reports on an investigations of a series of compounds of the NOy family, based on high resolution infrared solar observations made at the ISSJ (International Scientific Station of the ... [more ▼]

This paper reports on an investigations of a series of compounds of the NOy family, based on high resolution infrared solar observations made at the ISSJ (International Scientific Station of the Jungfraujoch), Switzerland (46.55ºN, 7.99ºE, 3580 m a.s.l.). These observations are part of a long-term monitoring effort undertaken by the Liège group since the mid-1970s, and integrated more recently as a contribution to the Network for the Detection of Stratospheric Change (NDSC). Currently, vertical column abundances of over 20 molecules are retrieved from solar spectra recorded under clear sky conditions as regularly as possible, using two high resolution Fourier transform infrared (2 to 15 microns) spectrometers. [less ▲]

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See detailAn overview of NDSC-related activities at the Jungfraujoch through high-resolution infrared solar observations
Zander, Rodolphe ULg; Demoulin, Philippe ULg; Mahieu, Emmanuel ULg et al

in Bojkov, R.; Visconti, G. (Eds.) Proceedings of "The XXVIII Quadrennial Ozone Symposium" (1998)

Since the mid-1970s, infrared remote sensing at the Jungfraujoch, Switzerland, has been performed in response to the need to measure the concentrations and assess the seasonal and long-term changes of an ... [more ▼]

Since the mid-1970s, infrared remote sensing at the Jungfraujoch, Switzerland, has been performed in response to the need to measure the concentrations and assess the seasonal and long-term changes of an increasing number of atmospheric constituents. Currently, the vertical column abundances of over 20 telluric gases are being monitored, based on the analysis of solar spectra recorded regularly between 2 and 14 microns, using two high-resolution Fourier transform spectrometers. In this paper, emphasis is placed on those activities more specifically performed within the framework of the NDSC (Network for the Detection of Stratospheric Change) whose objectives are briefly described in the introduction. [less ▲]

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See detailVertical column abundances of COF2 above the Jungfraujoch Station, derived from ground-based infrared solar observations
Mélen, F.; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Journal of Atmospheric Chemistry (1998), 29(2), 119-134

Total vertical column abundances of carbonyl fluoride (COF2) have been derived from observations made at the International Scientific Station of the Jungfraujoch (ISSJ; altitude 3.58 km, latitude 46.5 ... [more ▼]

Total vertical column abundances of carbonyl fluoride (COF2) have been derived from observations made at the International Scientific Station of the Jungfraujoch (ISSJ; altitude 3.58 km, latitude 46.5 degrees N, longitude 8.0 degrees E), Switzerland. A systematic analysis of two microwindows containing lines of the vi band was performed, based on a large set of high resolution infrared solar absorption spectra recorded with Fourier transform spectrometers, from 1985 to 1995. Examination of the whole available database indicates a significant increase of the burden of COF2 during the 1988-1995 period. The average exponential rate and the average linear rate referenced to 1992, calculated from daily mean measurements, are both equal to (4.0 +/- 0.5)% yr(-1) (one sigma error). The results are also evaluated and discussed within the context of seasonal variability and correlation between carbonyl fluoride and hydrogen fluoride (HF) columns above the ISSJ. [less ▲]

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See detailATMOS/ATLAS 3 infrared profile measurements of clouds in the tropical and subtropical upper troposphere
Rinsland, C. P.; Gunson, M. R.; Wang, P.-H. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (1998), 60(5), 903-919

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace ... [more ▼]

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 mu m region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (km(-1)) in microwindows at 831, 957, and 1204 cm(-1) have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 mu m is estimated from the smallest ice crystals observed in the 8-12 mu m region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 mu m shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3. Published by Elsevier Science Ltd. [less ▲]

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See detailATMOS/ATLAS 3 infrared profile measurements of trace gases in the November 1994 tropical and subtropical upper troposphere
Rinsland, C. P.; Gunson, M. R.; Wang, P.-H. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (1998), 60(5), 891-901

Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01 cm(-1) resolution infrared solar occultation spectra recorded between latitudes ... [more ▼]

Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01 cm(-1) resolution infrared solar occultation spectra recorded between latitudes of 5.3 degrees N and 31.4 degrees N. The observations were obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 3 shuttle flight, 3-12 November 1994. Elevated mixing ratios below the tropopause were measured for these gases during several of the occultations. The positive correlations obtained between the simultaneously measured mixing ratios suggest that the enhancements are likely the result of surface emissions, most likely biomass burning and/or urban industrial activities, followed by common injection via deep convective transport of the gases to the upper troposphere. The elevated levels of HCN may account for at least part of the "missing NOy" in the upper troposphere. Comparisons of the observations with values measured during a recent aircraft campaign are presented. Published by Elsevier Science Ltd. [less ▲]

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See detailNorthern and southern hemisphere ground-based infrared spectroscopic measurements of tropospheric carbon monoxide and ethane
Rinsland, C. P.; Jones, N. B.; Connor, B. J. et al

in Journal Of Geophysical Research. Atmospheres (1998), 103(D21), 28197-28217

Time series of CO and C2H6 measurements have been derived from high-resolution infrared solar spectra recorded in Lauder, New Zealand (45.0 degrees S, 169.7 degrees E, altitude 0.37 km), and at the U.S ... [more ▼]

Time series of CO and C2H6 measurements have been derived from high-resolution infrared solar spectra recorded in Lauder, New Zealand (45.0 degrees S, 169.7 degrees E, altitude 0.37 km), and at the U.S. National Solar Observatory (31.9 degrees N, 111.6 degrees W, altitude 2.09 km) on Kitt Peak. Lauder observations were obtained between July 1993 and November 1997, while the Kitt Peak measurements were recorded between May 1977 and December 1997. Both databases were analyzed with spectroscopic parameters that included significant improvements for C2H6 relative to previous studies. Target CO and C2H6 lines were selected to achieve similar vertical samplings based on averaging kernels. These calculations show that partial columns from layers extending from the surface to the mean tropopause and from the mean tropopause to 100 km are nearly independent. Retrievals based on a semiempirical application of the Rodgers optimal estimation technique are reported for the lower laver, which has a broad maximum in sensitivity in the upper troposphere. The Lauder CO and C2H6 partial columns exhibit highly asymmetrical seasonal cycles with minima in austral autumn and sharp peaks in austral spring. The spring maxima are the result of tropical biomass burning emissions followed by deep convective vertical transport to the upper troposphere and long-range horizontal transport. Significant year-to-year variations are observed for both CO and C2H6, but the measured trends, (+0.37 +/- 0.57)% yr(-1) and (-0.64 +/- 0.79)% yr(-1), 1 sigma, respectively, indicate no significant long-term changes. The Kitt Peak data also exhibit CO and C2H6 seasonal variations in the lower layer with trends equal to (-0.27 +/- 0.17)% yr(-1) and (-1.20 +/- 0.35')% yr(-1), 1 sigma, respectively. Hence a decrease in the Kitt Peak tropospheric C2H6 column has been detected, though the CO trend is not significant. Both measurement sets are compared with previous observations, reported trends, and three-dimensional model calculations. [less ▲]

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See detailGround-based infrared solar spectroscopic measurements of carbon monoxide during 1994 Measurement of Air Pollution From Space flights
Pougatchev, N. S.; Jones, N. B.; Connor, B. J. et al

in Journal Of Geophysical Research. Atmospheres (1998), 103(D15), 19317-19325

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented ... [more ▼]

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented. Spectroscopic measurements were performed correlatively with April and October MAPS flights by nine research groups from Belgium, Canada, Germany, Japan, New Zealand, Russia, and the United States. Characterization of the techniques and error analysis were performed. The role of the CO a priori profile used in the retrieval was estimated. In most cases an agreement between spectroscopic and MAPS data is within estimated MAPS accuracy of +/-10%. [less ▲]

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See detailThe current budjet of NOy above the Jungfraujoch as derived from IR Solar Observations.
Demoulin, Philippe ULg; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Air Pollution Research Report Nr 66 (1998). (1997)

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See detailTotal vertical column abundances of atmospheric gases derived from IR remote solar observations made at the Jungfraujoch Station.
Zander, Rodolphe ULg; Demoulin, Philippe ULg; Mahieu, Emmanuel ULg et al

in Hov, O. (Ed.) Transport and Chemical Transformation of Pollutants in the Troposphere. (1997)

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See detailObserved trends in total vertical column abundances of atmospheric gases from IR solar spectra recorded at the Jungfraujoch
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Delbouille, Luc et al

in Journal of Atmospheric Chemistry (1997), 28(1-3), 227-243

Since 1984, about 15 000 high quality infrared solar spectra have been recorded with state-of-the-art grating and Fourier transform spectrometers at the International Scientific Station of the ... [more ▼]

Since 1984, about 15 000 high quality infrared solar spectra have been recorded with state-of-the-art grating and Fourier transform spectrometers at the International Scientific Station of the Jungfraujoch, Switzerland. Nonlinear least squares spectral curve fitting of selected microwindows containing isolated and well characterized lines of 20 telluric gases have allowed to retrieve their total vertical column abundances above the station, leading to observational data bases essential to derive long- and short-term changes experienced by these species during the last 12 years. In this paper, we focus on atmospheric gases of particular interest within the context of the EUROTRACTOR (Tropospheric Ozone Research) project; secular evolution as well as seasonal cycles of the minor constituents CH4, CO and of the trace gases C2H6, OCS, C2H2, HCN and H2CO are reported and discussed. The long-lived N2O is included as a tracer of the dynamic activity of the atmosphere. [less ▲]

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See detailOn the use of HF as a reference for the comparison of stratospheric observations and models
Chipperfield, M. P.; Burton, M.; Bell, W. et al

in Journal of Geophysical Research (1997), 102(11D), 12901-12919

Hydrogen fluoride (HF) is often used as a simple reference for other column observations of chemically active stratospheric species. However, seasonal and shorter timescale variations in column HF make ... [more ▼]

Hydrogen fluoride (HF) is often used as a simple reference for other column observations of chemically active stratospheric species. However, seasonal and shorter timescale variations in column HF make its use as a reference more complicated. In this paper we characterize the expected magnitude of these variations in HF, and variations of ratio quantities involving HF, using a two-dimensional (2-D) photochemical model and two versions of a three-dimensional (3-D) transport model. The 2-D model predicts that the column ratios HNO3/HF and HCl/HF increase from midlatitudes to the tropics, although this is very sensitive to HCl and HNO3 abundances in the tropical upper troposphere. Seasonal variations in vertical motion modifys the predicted ratios; for example, wintertime descent at high latitudes decreases HCl/HF. The ratio HNO3/HF at high latitudes is strongly modified by seasonal variations in the chemical partitioning of the odd nitrogen (NOy) species. We compare these model predictions with ground-based Fourier transform infrared spectroscopy (FTIR) observations of HF along with HCl, ClONO2 and HNO3 obtained at eight northern hemisphere sites between October 1994 and July 1995. We investigate quantitatively how HF can be used as a tracer to follow the evolution of observations at a single station and to intercompare results from different stations or with photochemical models. The magnitude of the 3-D model HF column agrees well with the observations, except on some occasions at high latitudes, giving indirect support for the important role of COF2 in the stratospheric inorganic fluorine budget. The observed day-to-day variability in the column ratios HCl/HF and HNO3/HF is much larger at high latitudes. This variability is reproduced in the 3-D models and is due to horizontal motion. Short timescale vertical displacement of the species profiles is estimated to have a small effect on the column ratios. In particular, we analyze the usefulness of the observed column ratio (ClONO2 + HCl)/HF as an indicator for chlorine activation. Current measurement uncertainties limit the degree of activation which can be unambiguously detected using this observed quantity, but we can determine that chlorine-activated air was observed above Aberdeen (58 degrees N) on 6 days in late January 1995. [less ▲]

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See detailThe 1994 northern midlatitude budget of stratospheric chlorine derived from ATMOS/ATLAS-3 observations
Zander, Rodolphe ULg; Mahieu, Emmanuel ULg; Gunson, M. R. et al

in Geophysical Research Letters (1996), 23(17), 2357-2360

Volume mixing ratio (VMR) profiles of the chlorine-bearing gases HCl, ClONO2, CCl3F, CCl2F2, CHClF2, CCl4, and CH3Cl have been measured between 3 and 49 degrees northern- and 65 to 72 degrees southern ... [more ▼]

Volume mixing ratio (VMR) profiles of the chlorine-bearing gases HCl, ClONO2, CCl3F, CCl2F2, CHClF2, CCl4, and CH3Cl have been measured between 3 and 49 degrees northern- and 65 to 72 degrees southern latitudes with the Atmospheric Trace MOlecule Spectroscopy (ATMOS) instrument during the ATmospheric Laboratory for Applications and Science (ATLAS)-3 shuttle mission of 3 to 12 November 1994. A subset of these profiles obtained between 20 and 49 degrees N at sunset, combined with ClO profiles measured by the Millimeter-wave Atmospheric Sounder (MAS) also from aboard ATLAS-3, measurements by balloon for HOCl, CH3CCl3 and C2Cl3F3, and model calculations for COClF indicates that the mean burden of chlorine, Cl-TOT, was equal to (3.53 +/- 0.10) ppbv (parts per billion by volume), 1-sigma, throughout the stratosphere at the time of the ATLAS 3 mission. This is some 37% larger than the mean 2.58 ppbv value measured by ATMOS within the same latitude zone during the Spacelab 3 flight of 29 April to 6 May 1985, consitent with an exponential growth rate of the chlorine loading in the stratosphere equal to 3.3%/yr or a linear increase of 0.10 ppbv/yr over the Spring-1985 to Fall-1994 time period. These findings are in agreement with both the burden and increase of the main anthropogenic Cl-bearing source gases at the surface during the 1980s, confirming that the stratospheric chlorine loading is primarily of anthropogenic origin. [less ▲]

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