Meridional variations of temperature, C2H2 and C2H6 abundances in Saturn's stratosphere at southern summer solstice

Measurements of the vertical and latitudinal variations of temperature and C₂H₂ and C₂H₆ abundances in the stratosphere of Saturn can be used as stringent constraints on seasonal climate models, photochemical models, and dynamics. The summertime photochemical loss timescale for C₂H₆ in Saturn's middle and lower stratosphere (∼40-10,000 years, depending on altitude and latitude) is much greater than the atmospheric transport timescale; ethane observations may therefore be used to trace stratospheric dynamics. The shorter chemical lifetime for C₂H₂ (∼1-7 years depending on altitude and latitude) makes the acetylene abundance less sensitive to transport effects and more sensitive to insolation and seasonal effects. To obtain information on the temperature and hydrocarbon abundance distributions in Saturn's stratosphere, high-resolution spectral observations were obtained on September 13-14, 2002 UT at NASA's IRTF using the mid-infrared TEXES grating spectrograph. At the time of the observations, Saturn was at a LS≈270°, corresponding to Saturn's southern summer solstice. The observed spectra exhibit a strong increase in the strength of methane emission at 1230 cm⁻¹ with increasing southern latitude. Line-by-line radiative transfer calculations indicate that a temperature increase in the stratosphere of ≈10 K from the equator to the south pole between 10 and 0.01 mbar is implied. Similar observations of acetylene and ethane were also recorded. We find the 1.16 mbar mixing ratio of C₂H₂ at −1° and −83° planetocentric latitude to be and , respectively. The C₂H₂ mixing ratio at 0.12 mbar is found to be at −1° planetocentric latitude and at −83° planetocentric latitude. The 2.3 mbar mixing ratio of C₂H₆ inferred from the data is and at −1° and −83° planetocentric latitude, respectively. Further observations, creating a time baseline, will be required to completely resolve the question of how much the latitudinal variations of C₂H₂ and C₂H₆ are affected by seasonal forcing and/or stratospheric circulation.     

Geometry of Poincaré's Variables and the Secular Planetary Problem

A method for the expansion of the perturbative Hamiltonian in the planetary problem is presented, which allows one to immediately detect the terms vanishing under the averaging process. The method bases itself on a geometrical analysis, through the groups SO(3) and SU(2), of the Poincaré canonical variables or of the similar Laplace variables. As an outcome, one obtains a MAPLE program, which calculates the first averaged terms of the perturbative Hamiltonian. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intermittency of magnetic turbulence in slow solar wind

We investigate the properties of intermittency of magnetic turbulence by using magnetic field data collected by the Helios spacecraft in the inner heliosphere. Clear scaling laws for magnetic structure functions are visible in periods where the velocity of the bulk plasma is low. Within these periods we found that intermittency of magnetic turbulence is high with respect to velocity field. A comparison with fluid flows where passive scalars are more intermittent than velocity, yields to consider the magnetic field like a “passive vector”.     

Karstification as geomorphological evidence of river incision: the karst of Cousance and the Marne valley (eastern Paris Basin)

The Cousance karst (located between the valleys of the Saulx and Marne) has been studied to determine the temporal records of river incision in the eastern Paris Basin, around the ANDRA experimental nuclear waste repository. Two generations of karst are recognized. The first is a palaeophreatic karst indicative of an old base level, now uplifted +75 m above the underground streams. It is underlain and drained by a second generation of karst with active sinks, which records the vertical evolution following the entrenchment of the River Marne. Ten U/Th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes, mainly during isotopic stages 3 and 5 (between 102.4 ± 1.2 and 49.4 ± 0.4 ka bp ) but also during isotopic stage 2 at 16.3 ± 0.1 and 20.9 ± 0.3 ka bp . These dates provide an absolute age limit for the start of vertical development of the karst, at the latest during isotope stage 5c.     

Zur Bestimmung symmetrologischer Typen der Gefügeelemente im Kugelschnitt durch das Gefüge

Ohne ZusammenfassungMit 12 Textabbildungen     

Numerische Untersuchungen Über Nicht-Periodische Transtrojaner-Bahnen

For 14 values of the mass parameter μ (from 0.0010 until 0.0150) the non-periodic Transtrojan orbits (aroundL ₄ and L₅) are investigated, which on the plane restricted problem of three bodies pass the point situated opposite to the body μ (looking from the main mass) with zero velocity in the rotating coordinate system. Results: The Transtrojan state contains a finite number of ‘double librations’ (aroundL ₄ and L₅); this number decreases with growing value of the mass parameter. Above a value of mass parameter between 0.010 and 0.015 no further double-libration takes place. Certain topologic properties of the Transtrojan state are found; for example this state has a phase of narrowing and a phase of widening of the single librations; thereby the amplitudes of the librations fluctuate in a characteristic manner. The investigations will be published inAstronomische Nachrichten in German language.     

Effects of PCBs on reactive oxygen species (ROS) production by the immune cells of Paracentrotus lividus (Echinodermata)

The impact of four PCB congeners: 3,3',4,4'-tetrachlorobiphenyl (IUPAC congener #77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126), 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC #153) and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities.     

Using land cover changes and demographic data to improve hydrological modeling in the Sahel

At the beginning of the drought in the Sahel in the 1970s and 1980s, rainfall decreased markedly, but runoff coefficients and in some cases, absolute runoff increased. This situation was due to the conversion of the land cover from natural vegetation with a low annual runoff coefficient, to cropland and bare soils, whose runoff coefficients are higher. Unless they are adapted, hydrological conceptual models, such as GR2M, are unable to reproduce this increase in runoff. Despite the varying environmental and climatic conditions of the West African Sahel, we show that it is possible to increase the performance of the GR2M model simulations by elaborating a time‐varying soil water holding capacity and to incorporate this value in the annual maximum amount of water to be stored in reservoir A of the model. We looked for interactions between climate, rural society, and the environment. These interactions drive land‐cover changes in the Sahel, which in turn drive the distribution of rainfall between infiltration, evaporation, and runoff and hence the water resources, which are vital in this region. We elaborated several time series of key indicators linked to these interactions. We then integrated these changes in the runoff conditions of the GR2M model through the maximum value of the reservoir capacity. We calculated annual values of water holding capacity using the annual values of four classes of land cover, natural vegetation, cultivated area, bare soil, and surface water. We then used the hydrological model with and without this time‐varying soil value of A and compared the performances of the model under the two scenarios. Whatever the calibration period used, the Nash–Sutcliffe index was always greater in the case of the time‐varying A time series.