Shock tracers in the molecular cloud G1.6-0.025

Observations of the molecular cloud G1.6-0.025 in the 2_K-1_K and J₀-J_?1E series and 5_?1-4₀E line of CH₃OH, the (2-1) and (3-2) lines of SiO, and the 7_?7-6_?6 line of HNCO are described. Maps of the previously observed extended cloud with V_lsr～50 km/s and high-velocity clump with V_lsr～160 km/s, as well as a newly detected clump with V_lsr～0 km/s, have been obtained. The extended cloud and high-velocity clump have a nonuniform structure. The linewidths associated with all the objects are between 20 and 35 km/s, as is typical of clouds of the Galactic center. In some directions, emission at velocities from 40 to 160 km/s and from ?10 to +75 km/s is observed at the clump boundaries, testifying to a connection between the extended cloud and the high-velocity clump and clump at V_lsr～0 km/s. Compact maser sources are probaby contributing appreciably to the emission of the extended cloud in the 5_?1-4₀E CH₃OH line. Non-LTE modeling of the methanol emission shows that the extended cloud and high-velocity clump have a relatively low hydrogen density (<10⁴ cm^?3). The specific column density of methanol in the extended cloud exceeds 6×10⁸ cm^?3s, and is 4×10⁸?6×10⁹ cm^?3s in the high-velocity clump. The kinetic temperatures of the extended cloud and high-velocity clump are estimated to be <80 K and 150–200 K, respectively. Possible mechanisms that can explain the link between the extended cloud with V_lsr～50 km/s and the clumps with V_lsr～0 km/s and ～160 km/s are briefly discussed.     

Scaling laws for radiating fluids: the pillar of laboratory astrophysics

In this paper, we derive the scaling laws for different radiating fluids. The studied regimes are relevant for both laboratory astrophysics and High Energy Density Physics. Using Lie groups theory, we obtain scaling laws, the similarity properties and the number of free parameters to rescale experiments.     

Quantimet image analysis of soil pore geometry: Comparison with tracer breakthrough curves

The relationships between two-dimensional image analysis of soil thin-sections and tracer breakthrough curves has been studied for a silty clay loam brown earth soil under saturated conditions. Initial tracer breakthrough is well in advance of one pore volume. Discrepancies between Quantimet image analysis and breakthrough curve characterization were related by inference to the role of infrequently occurring macropores not necessarily sampled on the two-dimensional images. A fundamental difficulty found in the use of image analysis is the uncertain nature of the relationship between the two-dimensional image and the three-dimensional pore system. Caution is needed in using Quantimet image analysis to describe gross properties of the three-dimensional pore system.     

Tertiary age and paleostructural inferences of the eclogitic imprint in the Austroalpine outliers and Zermatt–Saas ophiolite, western Alps

The Austroalpine Sesia-Lanzo inlier and upper Austroalpine Dent Blanche, Mt. Mary and Pillonet outliers occur on top of the western-Alpine orogenic wedge and, as a whole, override the structurally composite ophiolitic Piemonte zone. Instead, the Mt. Emilius, Glacier-Rafray, Etirol-Levaz and other lower Austroalpine eclogitic outliers are inserted within the Piemonte zone, between its upper (Combin) and lower (Zermatt-Saas) tectonic elements, or within the latter. Rb-Sr dating on phengitic micas show that the eclogitic imprint in the lower Austroalpine outliers, conventionally regarded as Late Cretaceous by comparison with the Sesia-Lanzo inlier, is of Eocene age (49-40 Ma), like the underlying Zermatt-Saas ophiolite (45-42 Ma) between the Aosta valley and Gran Paradiso massif. ⁴⁰Ar-³⁹Ar plateau ages on the same mica concentrates of the ophiolitic Zermatt-Saas nappe (46-43 Ma) are consistent with Rb-Sr dating, whereas that on the Austroalpine Glacier-Rafray klippe (92 Ma) is influenced by argon excess. The lower Austroalpine outliers underwent the subduction metamorphism concurrently with the Zermatt-Saas nappe, 20-25 Ma later than the eclogitic Sesia-Lanzo inlier and blueschist Pillonet klippe. The temporal gap and present intra-ophiolitic position mean that the lower Austroalpine outliers were probably derived from an intraoceanic extensional allochthon (Mt. Emilius domain) stranded inside the Piemonte-Ligurian ocean far from the Dent Blanche-Sesia domain and Adriatic margin.     

Circulation in the southwestern part of the Kara Sea in September 2007

During cruise 54 of the R/V Akademik Mstislav Keldysh to the southwestern Kara Sea (September 6 to October 7, 2007), a large amount of hydrophysical data with unique spatial resolution was obtained on the basis of measurements using different instruments. The analysis of the data gave us the possibility to study the dynamics and hydrological structure of the southwestern Kara Sea basin. The main elements of the general circulation are the following: the Yamal Current, the Eastern Novaya Zemlya Current, and the St. Anna Trough Current. All these currents are topographically controlled; they flow over the bottom slopes along the isobaths. The Yamal Current begins at the Kara Gates Strait and turns to the east as part of the cyclonic circulation. Then, it turns to the north and propagates along the Yamal coast over the 100-m isobath. The Eastern Novaya Zemlya Current (its core is located over the eastern slope of the Novaya Zemlya Trough) flows to the northeast. Near the northern edge of Novaya Zemlya, it encounters the St. Anna Trough Current, separates from the coast, and flows practically to the east merging with the continuation of the Yamal Current. A strong frontal zone is formed in the region where the two currents merge above the threshold that separates the St. Anna Trough from the Novaya Zemlya Trough and divides the warm and saline Arctic waters from the cooler and fresher waters of the southwestern part of the Kara Sea. This threshold, whose depth does not exceed 100–150 m, is a barrier that prevents the spreading of the Barents Sea and Arctic waters to the southwestern part of the Kara Sea basin through the St. Anna Trough.     

Evaluating the effect of the global ionospheric map on aiding retrieval of radio occultation electron density profiles

Radio occultation (RO) has been proven to be a powerful technique for ionospheric electron density profile (EDP) retrieval. The Abel inversion currently used in RO EDP retrieval has degraded performance in regions with large horizontal gradients because of an assumption of spherical symmetry as indicated by many studies. Some alternative methods have been proposed in the past; the global ionospheric map (GIM)-aided Abel inversion is most frequently studied. Since the number of RO observations will likely increase rapidly in the near future, it is worthwhile to continue to improve retrieval method. In this study, both the simulations and the real data test have been done to evaluate the GIM-aided Abel inversion method. It is found that the GIM-aided Abel inversion can significantly improve upon the standard Abel inversion in either the F or the E region if an accurate GIM is available. However, the current IGS GIM does not appear accurate enough to improve retrieval results significantly, because of the spherical symmetry assumption and sparse global navigation satellite system (GNSS) stations used in its creation. Generating accurate GIM based on dense GNSS network to aid the Abel inversion might be an alternative method.     

Electric Potential and Fréchet Derivatives for a Uniform Anisotropic Medium with a Tilted Axis of Symmetry

In this paper we develop analytic solutions for the electric potential, current density and Fréchet derivatives at any interior point within a 3-D transversely isotropic medium having a tilted axis of symmetry. The current electrode is assumed to be on the surface of the Earth and the plane of stratification given arbitrary strike and dip. Profiles can be computed for any azimuth. The equipotentials exhibit an elliptical pattern and are not orthogonal to the current density vectors, which are strongly angle dependent. Current density reaches its maximum value in a direction parallel to the longitudinal conductivity direction. Illustrative examples of the Fréchet derivatives are given for the 2.5-D problem, in which the profile is taken perpendicular to strike. All three derivatives of the Green’s function with respect to longitudinal conductivity, transverse resistivity and dip angle of the symmetry axis (dG/dσ_l, dG/dσ_t, dG/dθ₀) show a strongly asymmetric pattern compared to the isotropic case. The patterns are aligned in the direction of the tilt angle. Such sensitivity patterns are useful in real-time experimental design as well as in the fast inversion of resistivity data collected over an anisotropic earth.