Similarities between Circular Polarization in Galactic Jet Sources and AGN

We compare the observational properties of the circular polarization in Galactic jet sources with that observed in AGN, and outline the constraints they place on the mechanism responsible for the circular polarization. We also discuss the implications of the time scale of polarization variations on the mechanism responsible for the circular polarization.     

Growth of the Namche Barwa Syntaxis and associated evolution of the Tsangpo Gorge: Constraints from structural and thermochronological data

The eastern syntaxis of the Himalaya, Namche Barwa, is dominated by a north-plunging antiform which began to decompress/grow at approximately 4 Ma. New fission-track analyses on both apatite and zircon, combined with previous geochronological ages, indicate that the Namche Barwa Dome also extended laterally while growing vertically. Zircon fission-track ages range from 17.6 to 0.2 Ma and have a strong relationship to the main faults of the region, including the Tertiary Tsangpo Suture, with the younger ages inside the fault bounds towards the syntaxis core on the Indian Plate and the older ages away from the fault. Apatite ages reveal that the dome has grown laterally and now impinges over the older faulted margin onto the Asian Plate. The dome is traversed by the Tsangpo which has followed the trace of the Suture for over 1300 km from its source to the entrance of the dome near Dania. As the Tsangpo crosses the dome it departs from the Suture but rejoins it some 60 km northeastwards. We construe that the Suture has been displaced by the growing antiform and as a consequence, the antecedent river has been “dragged” in a left-lateral sense along the exhuming north-plunging dome. Restoring the Suture to its position prior to 4 Ma reveals a path of the Tsangpo eastwards across the present southwestern position of the Namche Barwa indentation. This geometric reconstrunction implies that the Tsangpo and the Brahmaputra were always one and the same river. In addition, the Tsangpo was tectonically forced into juxtaposition with a tributary of the Jiali-Parlung which it probably then captured. The capture was due to tectonic forcing, in the last 4 Ma, rather than headward retreat of the paleo-Brahmaputra as has been previously suggested.     

Micro-XANES mapping of sulphur and its association with magnesium and phosphorus in the shell of the brachiopod, Terebratulina retusa

Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod Terebratulina retusa, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from T. retusa indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of T. retusa correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer.     

The use of principle component analyses in characterising trace and major elemental distribution in a 55 kyr peat deposit in tropical Australia: Implications to paleoclimate

The Lynch’s Crater peat deposit in NE-Australia is a sensitive environmental archive located in the tropical Southern Hemisphere. This unique deposit illustrates that local and regional changes had a profound effect on the local Australian ecosystem over the past 55 kyr. To obtain a proxy of past climate changes, trace and major element geochemistry analyses were applied to a 13 m peat core from the crater. Principle component analysis (PCA) was used to identify the main factors that control elemental distribution in the peat and to add interpretative strength to the geochemical behavior of selected major and trace elements. For example, Sc, Al, Cu, and Pb were found to be related to increased erosion of the basin soils, and from this, several periods of significant flux from atmospheric input and/or terrigenous run-off were identified. Geochemically mobile elements during rock weathering and pedogenesis, such as Mg, Ca, and Sr helped to identify the peat ombrotrophic-minerotrophic boundary at ∼1.5 m depth and offered important information about fluxes of these nutrients to the mire and their dynamics within the deposit. Arsenic and V comparisons between the peat record (high concentrations in some peat sections) and in local basin rocks (very low concentrations), suggested the presence of a long range, atmospheric dust source early in the formation of the mire. The Lynch’s Crater peat record presents a continuous record of environmental change in tropical Australia and contributes new understanding to geochemical processes in peatlands.     

Incidence de la cinetique de decroissance de la temperature apres le choc thermique sur les modifications d'activite des esterases et les possibilites de survie de Scolelepis (malacoceros) fuliginosa (annelide polychete)

Scolelepis fuliginosa reared in the laboratory at 13°C were put through 10-min thermal shocks at 16°C and 18°C and were then submitted to either a slow or a rapid temperature reduction. After the thermal shock, a posterior fragment of each specimen was cut off at intervals, until six days. Samples were submitted to electrophoresis on polyacrylamide gel, esterase activity being determined with α-naphthyl acetate.Enzymograms show that thermal shocks act on esterases in decreasing the activity of the main fractions. Immediate effects result in a very precocious enzymic response; more long-term effects depend on the maximum temperature, the animal's sex and the kinetics of the post-shock thermal reduction.Females are more sensitive than males. For a given Δt, esterase changes are greater and more long-lasting. After a 16°C Δt, a rapid decrease in temperature prevents the loss of activity of the middle and fast fractions in males and delays, by about 10 h, the alteration of female esterases. After 18°C ΔT, loss of activity of the middle and fast fractions occurs in less than 1 h, independently of the thermal kinetics, but survival is only possible—solely for males—with a rapid decrease in temperature which also delays females' deaths by between 24 and 48 h.In conclusion, a rapid decrease in temperature gives organisms a better resistance to thermal shock, as determined by esterase activity and controls the lethality of a high Δt.     

Small-scale variability of zooplankton pyruvate kinase activity in the Gironde Estuary plume (Atlantic French Coast): A case study under unusually low freshwater discharge

Pyruvate kinase (PK) activity measurements are used to assess the role of carbohydrates in global feeding of mesozooplankton communities inhabiting an estuary plume. As a consequence of a remarkably low freshwater discharge rate, the sea surface layers of the area under estuarine influence showed a very moderate salinity fall and a nearly total depletion in nitrates, whereas higher levels of these nutrients were found in deeper, more saline, layers. Small-scale PK activity variations in mesozooplankton appear to be closely correlated to nitrate integration values within the water column. The results were analysed in comparison with literature reports. The study produced a coherent overall interpretation, which strongly supports the reliability of this new biochemical tool in detecting assimilation of trace carbohydrates in the diet of mesozooplankton.     

Active spreading and hydrothermalism in North Fiji Basin (SW Pacific). Results of Japanese French Cruise Kaiyo 87

The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and 22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of 16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living communities confirms this activity.