Anomalous abundance of lithium in the roAp star HD 12098 recently discovered in the northern hemisphere of the sky

Spectral observations of Ap-CP stars with the BTA (Special Astronomical Observatory, Russian Academy of Sciences) using the NES echelle spectrometer have revealed several stars with an anomalous lithium abundance. The oscillating star HD 12098, which is the first roAp star in the northern hemisphere of the sky, merits special attention. Strong, variable LiI 6708 Å line was observed in the spectrum of this star. There are not enough observations for a reliable analysis by Doppler mapping, but there are enough to indicate the presence of lithium spots on the surface of this star similar to the roAp stars HD 83368 and HD 60435, on whose surfaces spots with a high lithium abundance have been reliably detected. Parameters for a model of its atmosphere have been chosen using the method of synthetic spectra based on atmospheric models including lines from the VALD list and several additional blended REE lines calculated by the authors. The profile of the lithium LiI 6708 Å blend has been calculated taking the magnetic field into account using the SYNTHM code. A lithium abundance has been determined for two phases of the rotation of HD 12098 that is anomalously high compared to the solar and meteoritic abundances. The large difference in the lithium abundance in the two phases (in two different regions on the star's surface) exceeds 0.5 dex and is very close to that which we have found by analyzing the spectra of the roAp stars HD 83368 and HD 60435. Thus, we have discovered yet another roAp star, HD 12098, with lithium spots on its surface. Translated from Astrofizika, Vol. 51, No. 4, pp. 607–616 (November 2008).     

Some exact solutions for the flow of fluid through tubes with uniformly porous walls

Summary This paper considers an incompressible fluid flowing through a straight, circular tube whose walls are uniformly porous. The flow is steady and one dimensional. The loss of fluid through the wall is proportional to the mean static pressure in the tube. Several formulations of the wall shear stress are considered; these formulations were motivated by the results from Hamel's radial flow problem, boundary layer flows/and boundary layer suction profiles. For each of these formulations exact solutions for the mean axial velocity and the mean static pressure of the fluid are obtained. Sample results are plotted on graphs. For the constant wall shear stress problem, the theoretical solutions compare favorably with some experimental results.Notations A, B, D, E constant parameters - a, b constant parameters - Ai(z), Bi(z) Airy functions - Ai, Bi derivatives of Airy functions - k constant of proportionality betweenV andp - L length of pores - p,p mean static pressure - p ₀ static pressure outside the tube - p ₀ value ofp atx=0 - Q constant exponent - R inside radius of the tube - T wall shear stress - T ₀ shear parameter - t wall thickness - U free stream velocity - ,u mean axial velocity - u ₀ value ofu atx=0 - V,V mean seepage velocity through the wall - v ₀ mean seepage velocity - x,x axial distance along the tube - z transformed axial distance - z ₀ value ofz atx=0 - mean outflow angle through the wall - cos - density of the fluid - wall shear stress - dynamic viscosity of the fluid - over-bar dimensional terms - no bar nondimensional terms The National Center for Atmospheric Research is sponsored by the National Science Foundation     

Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp,SE Switzerland

Evidence from ultraslow spreading mid-ocean ridges and both fossil and present-day Ocean–Continent Transitions (OCT) demonstrates that mantle serpentinization resulting from the interaction of mantle rock and water during tectonic exhumation is widespread. Observations at white smokers in modern ocean settings suggest that methane produced by serpentinization can support methanotrophic bio-systems, which use methane as the only source of carbon. An important question is whether such bio-systems are more generally pervasive in their association with serpentinized mantle in the subsurface. In this study, we examined whether there is evidence for such a methanotrophic system in exhumed serpentinized mantle at a magma-poor rifted continental margin, by probing for characteristic biological markers in these and associated sedimentary rocks in the Totalp unit of SE Switzerland. This unit represents a remnant of the former OCT of the southern Alpine Tethyan margin and was chosen because of its mild Alpine tectonic and low-grade metamorphic overprint during Alpine orogeny, hence giving potential for the preservation of indigenous organic matter (OM). Totalp samples are characterized by low organic carbon contents of 11–647 ppm. The majority of the samples contain hydrocarbons in the form of n-alkanes in the range C₁₇–C₃₆. Some sediments contain isoprenoids, for example pristane and phytane and a suite of steranes that are consistent with a marine origin for the OM preserved in the rocks. Traces of marine planktonic and bacterial OM are preserved in the serpentinized mantle and overlying sediments of this ancient Tethyan OCT, but there is no evidence that the OM has been generated from methanotrophic bio-systems.     

Regional subglacial quarrying and abrasion below hard-bedded palaeo-ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control

Three-dimensional surface visualization models derived from high-resolution LiDAR data provide new information about the type and scale of erosional processes below Late Wisconsin palaeo-ice streams traversing the boundary between Canadian Shield crystalline rocks with offlapping Palaeozoic limestones in central Ontario. The hard bed is directly analogous to that found below ice streams in East Antarctica and East Greenland and provides insight into the effects of abrupt changes in substrate type on subglacial processes. Erosion of hard crystalline Canadian Shield rock was largely ineffectual consisting of areal abrasion of rounded whalebacks and local lee side plucking. In contrast, fast flow over the strike of gently dipping well-bedded and jointed Palaeozoic limestones cut large flow-parallel grooves and ridges akin to mega-scale glacial lineations reflecting intense abrasion below narrow streams of subglacial debris dominated by hard crystalline Shield clasts (erodents). Regionally extensive plucking of structurally weak, well-jointed and bedded limestone produced large volumes of rubbly carbonate debris leaving a 25-km-wide belt of uncontrolled hummocky rubble terrain (long known as the Dummer Moraine in Southern Ontario) some 350 km long and locally as much as 10 m thick. Subglacial plucking and abrasion under fast flowing ice were highly effective in stripping limestone cover rocks from Precambrian basement, and over many glacial cycles, may have played a role in the location and excavation of numerous large and deep lake basins around the Shield–Palaeozoic boundary zone in North America.     

Multiple phases of North African humidity recorded in lacustrine sediments from the Fazzan Basin, Libyan Sahara

The Fazzan Basin of south-west Libya is at present arid with less than 20 mm of rainfall per annum. However, regionally extensive limestones, lacustrine sands and coquina (fossiliferous carbonate rock) deposits show that the Fazzan Basin previously contained a large palaeolake, indicating that the climate in the past was more humid. Optically stimulated luminescence (OSL) dating techniques have been applied to key lacustrine deposits within the basin in an attempt to provide an internally consistent chronology for this humidity record. Results indicate that palaeolake sediments within the Fazzan Basin record a very long history of palaeohydrological change, ranging from present day arid conditions to humidity capable of sustaining a lake with an approximate area of 76,250 km². The existence of humid periods in mid oxygen isotope stage 5 and the early Holocene is confirmed. An older lacustrine event, tentatively correlated to oxygen isotope stage 11, is also recognized. In addition, evidence is presented for at least two humid phases beyond the age range over which the conventional OSL dating technique is applicable. This study demonstrates that OSL dating of palaeolake sediments within the Fazzan Basin offers the potential to provide a detailed record of North African humidity spanning several glacial–interglacial cycles.     

Geochemistry of tin, tungsten and molybdenum in Swedish proterozoic granitoids: Their potential use in regional mineral exploration

The primary aim of this broad regional study is to statistically determine the Li-Sn-W-Mo-bearing potential of various granitoids using geochemical criteria. Computer based, univariate and multivariate statistical methods are applied to major- and trace-element data from about 660 granitic rock samples and over 800 major element analyses, selected from the Swedish geological literature. The granitoids are subdivided following earlier geotectonic chronologic and newer geochemical-statistical principles.Most granite types occurring in known Sn-W mineralized areas, except the granites around the W deposit of Baggetorp, were identified as potentially W-Sn-bearing. That is, they show significantly high mean and variance values for W and/or Sn as well as promising values of the probability parameters for these elements, compared to corresponding statistics for a calculated Swedish average granitoid (SAG).Evidence of very high total variability of Li, Sn and W within the individual granite types suggests the need for further tests, to control the variability errors due to sampling and preparation and errors of chemical analysis. These sources of error may obscure natural elemental heterogeneity of the granite type that is of interest in geochemical prospecting.Interpretations of Sn, W and Li frequency distribution patterns, petrochemical trends and multivariate similarity tests suggest that the primary chemistry of the granitoids is overprinted by (a) postmagmatic processes of broad regional nature, which have similarly affected the individual granite types, and (b) a wide variety of secondary alterations of local character. These conclusions imply that potential Sn and W deposits may be sought within all Swedish Proterozoic granitoids and their within all Swedish Proterozoic granitoids and their immediate sorroundings, where susch processes have redistributed and concentrated these where such processes have redistributed and concentrated these elements. However, the granites which are highly differentiated, Sn-W-Li-U-Th-F-enriched, and strongly and strongly magnetic are particularly promising target areas for further, extensive rock-geochemical prospecting and other exploration surveys. rock-geochemical prospecting and other exploration surveys.     

新疆西天山高硫化型京希-伊尔曼德金矿床的识别标志及其找矿意义

经过详细的野外地质勘查、热液蚀变及蚀变矿物学研究，流体包裹体和同位素研究，首次将西天山京希－伊尔曼德金矿床确定为高硫化型浅成低温热液金矿床。该矿床的主要识别标志为：发育以多孔状石英为特征的硅化蚀变带和高级泥化蚀变带；成矿流体性质为低盐度[W(NaCl)为0.3-4.2%]、低pH值（3－4）和高氧化态；氧同位素δ（^18O)为1.7 ‰-4.3‰,δ(D)为－60‰--80‰。金主要富集在高级泥化带和中心硅化蚀变带内。系统研究和总结了成矿地质－地球化学制约因素以及区域、靶区和勘探区尺度的找矿标志。     

XMM-Newton observations of the isolated neutron star 1RXS J214303.7+065419/RBS1774

We report XMM-Newton observations of the isolated neutron star RBS1774 and confirm its membership as an XDINS. The X-ray spectrum is best fit with an absorbed blackbody with temperature kT=101 eV and absorption edge at 0.7 keV. No power law component is required. An absorption feature in the RGS data at 0.4 keV is not evident in the EPIC data, but it is not possible to resolve this inconsistency. The star is not seen in the UV OM data to m _AB ∼21. There is a sinusoidal variation in the X-ray flux at a period of 9.437 s with an amplitude of 4%. The age as determined from cooling and magnetic field decay arguments is 10⁵–10⁶ yr for a neutron star mass of 1.35–1.5 M_⊙.