scholarly journals Vermiculations in painted caves: New inputs from laboratory experiments and field observations

2021 ◽  
Vol 50 (3) ◽  
pp. 289-299
Author(s):  
Perrine Freydier ◽  
Eric Weber ◽  
Jérôme Martin ◽  
Pierre-Yves Jeannin ◽  
Béatrice Guerrier ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Water Film ◽  
Quantitative Information ◽  
Time Step ◽  
Similar Time ◽  
Chemical Monitoring ◽  
Sediment Deposits ◽  
Cave Paintings ◽  
Observation Protocol ◽  
Lascaux Cave

Vermiculations are aggregates of small particles commonly found on cave walls. They are a major concern for the conservation of painted caves, as they can potentially alter valuable prehistoric cave paintings. A previous rheological study of fine sediment deposits on cave walls revealed that this material can undergo a solid-to-liquid transition triggered by variations in the chemical composition of the water film on the wall. Such a transition could occur at the origin of vermiculations by allowing the sediment to flow under low mechanical stress. In this work, we provide quantitative information on the conditions leading to this transition and show the importance of the chemical composition of the water film on the cave walls. A complete understanding of the phenomenon will, however, require more field information. This includes monitoring of the evolution of vermiculations, for which we have developed a dedicated observation protocol. Based on the combination of photogrammetry and a geographic information system we were able to precisely map the walls of the Hall of Bulls in Lascaux cave from past and future photographs. To better understand the vermiculation process, pictures need to be taken regularly, and the chemical composition of the thin water film covering cave walls needs to be analyzed with a similar time step. The correlation between the evolution of vermiculations, the humidification phases of the walls, temperature changes and the chemical monitoring of the water film should shed new light on conditions triggering vermiculations.

scholarly journals Version 2 of the EUMETSAT OSI SAF and ESA CCI Sea Ice Concentration Climate Data Records

2018 ◽  
Author(s):  
Thomas Lavergne ◽  
Atle Macdonald Sørensen ◽  
Stefan Kern ◽  
Rasmus Tonboe ◽  
Dirk Notz ◽  
...  
Keyword(s):  
Sea Ice ◽  
Satellite Data ◽  
Grid Point ◽  
Ice Cover ◽  
Quantitative Information ◽  
Horizontal Resolution ◽  
Climate Data ◽  
Time Step ◽  
Sea Ice Concentration ◽  
Ice Concentration

Abstract. We introduce the OSI-450, the SICCI-25km and the SICCI-50km climate data records of gridded global sea-ice concentration. These three records are derived from passive microwave satellite data and offer three distinct advantages compared to existing records: First, all three records provide quantitative information on uncertainty and possibly applied filtering at every grid point and every time step. Second, they are based on dynamic tie points, which capture the time evolution of surface characteristics of the ice cover and accommodate potential calibration differences between satellite missions. Third, they are produced in the context of sustained services offering committed extension, documentation, traceability, and user support. The three records differ in the underlying satellite data (SMMR & SSM/I & SSMIS or AMSR-E & AMSR2), in the imaging frequency channels (37 GHz and either 6 GHz or 19 GHz), in their horizontal resolution (25 km or 50 km) and in the time period they cover. We introduce the underlying algorithms and provide an initial evaluation. We find that all three records compare well with independent estimates of sea-ice concentration both in regions with very high sea-ice concentration and in regions with very low sea-ice concentration. We hence trust that these records will prove helpful for a better understanding of the evolution of the Earth's sea-ice cover.

A New Unconditionally Stable Time Integration Method for Analysis of Nonlinear Structural Dynamics

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Ali Akbar Gholampour ◽  
Mehdi Ghassemieh ◽  
Mahdi Karimi-Rad
Keyword(s):  
Time Integration ◽  
Second Order ◽  
Numerical Dispersion ◽  
Computational Time ◽  
Numerical Dissipation ◽  
Integration Scheme ◽  
Time Step ◽  
Similar Time ◽  
Unconditionally Stable ◽  
Average Acceleration

A new time integration scheme is presented for solving the differential equation of motion with nonlinear stiffness. In this new implicit method, it is assumed that the acceleration varies quadratically within each time step. By increasing the order of acceleration, more terms of the Taylor series are used, which are expected to have responses with better accuracy than the classical methods. By considering this assumption and employing two parameters δ and α, a new family of unconditionally stable schemes is obtained. The order of accuracy, numerical dissipation, and numerical dispersion are used to measure the accuracy of the proposed method. Second order accuracy is achieved for all values of δ and α. The proposed method presents less dissipation at the lower modes in comparison with Newmark's average acceleration, Wilson-θ, and generalized-α methods. Moreover, this second order accurate method can control numerical damping in the higher modes. The numerical dispersion of the proposed method is compared with three unconditionally stable methods, namely, Newmark's average acceleration, Wilson-θ, and generalized-α methods. Furthermore, the overshooting effect of the proposed method is compared with these methods. By evaluating the computational time for analysis with similar time step duration, the proposed method is shown to be faster in comparison with the other methods.

scholarly journals Dating the Lascaux Cave Gour Formation

Radiocarbon ◽  
2011 ◽  
Vol 53 (3) ◽  
pp. 479-500 ◽  
Author(s):  
D Genty ◽  
S Konik ◽  
H Valladas ◽  
D Blamart ◽  
J Hellstrom ◽  
...  
Keyword(s):  
Organic Matter ◽  
Eastern Mediterranean ◽  
Seepage Water ◽  
Calibration Data ◽  
Atlantic Period ◽  
Carbonate Deposit ◽  
Cave Paintings ◽  
Geomorphological Changes ◽  
Lascaux Cave ◽  
First Time

Lascaux Cave is renowned for its outstanding prehistoric paintings, strikingly well-preserved over about 18,000 yr. While stalagmites and stalactites are almost absent in the cave, there is an extensive calcite flowstone that covered a large part of the cave until its opening for tourists during the 1950s. The deposit comprises a succession of calcite rims, or “gours,” which allowed seepage water to pond in large areas in the cave. Their possible role in preservation of the cave paintings has often been evoked, but until now this deposit has not been studied in detail. Here, we present 24 new radiocarbon accelerator mass spectrometry (AMS) and 6 uranium-thorium (U-Th) analyses from the calcite of the gours, 4 AMS 14C dates from charcoals trapped in the calcite, and 4 AMS 14C analyses on organic matter extracted from the calcite. Combining the calibrated 14C ages obtained on charcoals and organic matter and U-Th ages from 14C analyses made on the carbonate, has allowed the calculation of the dead carbon proportion (dcp) of the carbonate deposits. The latter, used with the initial atmospheric 14C activities reconstructed with the new IntCal09 calibration data, allows high-resolution age estimation of the gour calcite samples and their growth rates. The carbonate deposit grew between 9530 and 6635 yr cal BP (for dcp = 10.7 ± 1.8%; 2 σ) or between 8518 and 5489 yr cal BP (for dcp = 20.5 ± 1.9%; 2 σ). This coincides with humid periods that can be related to the Atlantic period in Europe and to Sapropel 1 in the eastern Mediterranean Sea. However, geomorphological changes at the cave entrance might also have played a role in the gour development. In the 1940s, when humans entered the cave for the first time since its prehistoric occupation, the calcite gours had already been inactive for several thousand years.

scholarly journals Version 2 of the EUMETSAT OSI SAF and ESA CCI sea-ice concentration climate data records

2019 ◽  
Vol 13 (1) ◽  
pp. 49-78 ◽  
Author(s):  
Thomas Lavergne ◽  
Atle Macdonald Sørensen ◽  
Stefan Kern ◽  
Rasmus Tonboe ◽  
Dirk Notz ◽  
...  
Keyword(s):  
Sea Ice ◽  
Satellite Data ◽  
Grid Point ◽  
Ice Cover ◽  
Quantitative Information ◽  
Horizontal Resolution ◽  
Climate Data ◽  
Time Step ◽  
Sea Ice Concentration ◽  
Ice Concentration

Abstract. We introduce the OSI-450, the SICCI-25km and the SICCI-50km climate data records of gridded global sea-ice concentration. These three records are derived from passive microwave satellite data and offer three distinct advantages compared to existing records: first, all three records provide quantitative information on uncertainty and possibly applied filtering at every grid point and every time step. Second, they are based on dynamic tie points, which capture the time evolution of surface characteristics of the ice cover and accommodate potential calibration differences between satellite missions. Third, they are produced in the context of sustained services offering committed extension, documentation, traceability, and user support. The three records differ in the underlying satellite data (SMMR & SSM/I & SSMIS or AMSR-E & AMSR2), in the imaging frequency channels (37 GHz and either 6 or 19 GHz), in their horizontal resolution (25 or 50 km), and in the time period they cover. We introduce the underlying algorithms and provide an evaluation. We find that all three records compare well with independent estimates of sea-ice concentration both in regions with very high sea-ice concentration and in regions with very low sea-ice concentration. We hence trust that these records will prove helpful for a better understanding of the evolution of the Earth's sea-ice cover.

Effect of supplement type and grass silage:concentrate ratio on methane production by sheep

1993 ◽  
Vol 1993 ◽  
pp. 52-52 ◽  
Author(s):  
Angela R. Moss ◽  
D.I. Givens
Keyword(s):  
Chemical Composition ◽  
Methane Production ◽  
Quantitative Information ◽  
Anthropogenic Source ◽  
Grass Silage ◽  
Ruminant Animals ◽  
The Uk ◽  
Diet Type

Methane production by ruminant animals is an important anthropogenic source of methane to the atmosphere and is considered an important source to more accurately estimate and to control. It has been known for some time that, in ruminants, diet type and composition can influence methane production, yet there is little quantitative information for contemporary diets used 1n the UK. Attempts to predict methane production from either diet chemical composition or digestibility have not been successful (Moss and Givens, 1990; Johnson et al., 1991). In order to estimate more accurately the amount of methane produced by a ruminant on a given diet, it is essential to establish whether there are interactions of various substrates with forage and to relate this to the rumen environment. Previous work showing interactions has used mainly hay-based diets (Blaxter and Wainman, 1964); as grass silage is now the major forage in the UK, work with this forage was needed.

Qualitative XRF Analysis with Pattern Recognition

1989 ◽  
Vol 33 ◽  
pp. 603-613
Author(s):  
Lo. I. Yin ◽  
Stephen M. Seltzer
Keyword(s):  
Experimental Data ◽  
Pattern Recognition ◽  
Chemical Composition ◽  
Quantitative Information ◽  
Pattern Recognition Method ◽  
Geological Samples ◽  
Recognition Method ◽  
Pattern Recognition Techniques ◽  
Xrf Analysis ◽  
Pattern Recognition Approach

AbstractIn many applications of energy-dispersive XRF analysis, quantitative information concerning the chemical composition of the samples is not required. Rather, one is interested in whether a given sample is similar to some reference material or whether the chemical composition is changing from one sample to the next. We have investigated the use of pattern-recognition techniques in such applications. It will be demonstrated with experimental data that the pattern-recognition approach is extremely simple and fast. It uses only a single parameter, the normalized correlation coefficient, and can be applied directly to raw data. The efficacy of the method is illustrated with Si(Li) spectra of geological and pigment samples, and proportional counter spectra of geological samples. The pattern-recognition method should be ideally suited for field XRF applications, and the algorithm can be easily implemented on a personal computer.

The Lascaux Cave Paintings

1951 ◽  
Vol 55 (4) ◽  
pp. 402
Author(s):  
Hallam L. Movius ◽  
Fernand Windels ◽  
C. F. C. Hawkes
Keyword(s):  
Cave Paintings ◽  
Lascaux Cave

The Lascaux Cave Paintings

1950 ◽  
Vol 5 (17) ◽  
pp. 35
Author(s):  
A. G. ◽  
Fernand Windels
Keyword(s):  
Cave Paintings ◽  
Lascaux Cave

scholarly journals Modelling of base cation emissions, concentrations and deposition in the UK

2010 ◽  
Vol 10 (9) ◽  
pp. 21989-22018 ◽  
Author(s):  
M. Werner ◽  
M. Kryza ◽  
A. J. Dore ◽  
M. Błaś ◽  
S. Hallsworth ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Sea Water ◽  
Monitoring Network ◽  
Base Cations ◽  
Base Cation ◽  
Sea Surface ◽  
Time Step ◽  
The Uk

Abstract. Base cations exerts a large impact on various geochemical and geophysical processes both in the atmosphere and at the Earth surface. One of the essential roles of these compounds is impact on surface pH causing an increase in alkalinity and neutralizing the effects of acidity generated by sulphur and nitrogen deposition. During recent years anthropogenic emissions of base cations in the UK have decreased substantially, by about 70% for Na+, 78% for Mg2+, 75% for Ca2+ and about 48% for K+ for the period 1990–2006. For the island regions, such as the is UK, the main source of base cation particles is the aerosol produced from the sea surface. Here, the sea salt aerosol (SSA) emissions are calculated with parameterisations proposed by Maårtensson et al. (2003); ultra fine particles, Monahan et al. (1986); fine particles and Smith and Harisson (1998); coarse particles continuously with a 0.1 μ m size step using WRF-modelled wind speed data at a 5 km × 5 km grid square resolution with a 3 h time step for two selected years 2003 and 2006. SSA production has been converted into base cation emissions, with the assumption that the chemical composition of the particle emitted from the sea surface is equal to the chemical composition of sea water, and used as input data in the Fine Resolution Atmospheric Multi-pollutant Exchange Model (FRAME). FRAME model results, yearly mean concentrations and total wet deposition at a 5 km × 5 km grid resolution, are compared with concentrations in air and wet deposition from the National Monitoring Network and measurements based estimates of UK deposition budget. The correlation coefficient for wet deposition achieves high values for Na+ and Mg2+, and for Ca2+ there is significant scattering. Base cation concentration is also represented well, with some overestimations on the west coast and underestimations in the centre of the land.

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