On the error analyses of polarization measurements of the white-light coronagraph aboard ASO-S

The Advanced Space-based Solar Observatory(ASO-S) mission aims to explore the two most spectacular eruptions on the Sun: solar flares and coronal mass ejections(CMEs), and their magnetism.For the study of CMEs, the payload Lyman-alpha Solar Telescope(LST) has been proposed. It includes a traditional white-light coronagraph and a Lyman-alpha coronagraph which opens a new window to CME observations. Polarization measurements taken by white-light coronagraphs are crucial for deriving fundamental physical parameters of CMEs. To make such measurements, there are two options for a Stokes polarimeter which have been applied by existing white-light coronagraphs for space missions. One uses a single or triple linear polarizer, the other involves both a half-wave plate and a linear polarizer. We find that the former option is subject to less uncertainty in the derived Stokes vector propagating from detector noise.The latter option involves two plates which are prone to internal reflections and may have a reduced transmission factor. Therefore, the former option is adopted as our Stokes polarimeter scheme for LST. Based on the parameters of the intended linear polarizer(s) colorPol provided by CODIXX and the half-wave plate 2-APW-L2-012 C by Altechna, it is further shown that the imperfect maximum transmittance of the polarizer significantly increases the variance amplification of Stokes vector by at least about 50% when compared with the ideal case. The relative errors of Stokes vector caused by the imperfection of colorPol polarizer and the uncertainty due to the polarizer assembly in the telescope are estimated to be about 5%. Among the considered parameters, we find that the dominant error comes from the uncertainty in the maximum transmittance of the polarizer.     

Relative sea level changes during the Holocene in the Sisimiut area,south‐western Greenland

Holocene relative sea level (RSL) changes have been investigated by analysing and dating isolation sequences from five lakes near Sisimiut in south‐western Greenland. The transitions between marine and lacustrine sediments were determined from elemental analyses and analyses of macroscopic plant and animal remains. Radiocarbon dating was used to provide minimum ages for the transitions and to construct a RSL curve. Dating of a shell of the marine bivalve Macoma balthica indicates that deglaciation of the lowlands occurred in the early Holocene, at around 10 900 cal a BP. The RSL curve shows initial rapid regression from the marine limit at around 140 m, implying strong glacio‐isostatic rebound. We suggest that the margin of the Greenland Ice Sheet was located at the shelf break during the Last Glacial Maximum. Frequent remains of the ostracode Sarcypridopsis aculeata, which is a thermophilous brackish water species that is unknown from the extant fauna of Greenland, in one of the basins around 8500 cal a BP may mark the beginning of the Holocene thermal maximum in the region. Copyright © 2011 John Wiley & Sons, Ltd.     

Organic geochemistry of Deep Sea Drilling Project sediments from the Gulf of Calofornia—hydrothermal effects on unconsolidated diatom ooze

The effects of intrusive thermal stress have been studied on a number of Pleistocene sediment samples obtained from Leg 64 of the DSDP-IPOD program in the Gulf of California. Samples were selected from Sites 477, 478 and 481 where the organic matter was subjected to thermal stress from sill intrusions. For comparison purposes, samples from Sites 474 and 479 were selected as representative of unaltered material.The GC and GC-MS data show that lipids of the thermally unaltered samples were derived from microbial and terrestrial higher-plant detritus. Samples from sill proximities were found to contain thermally-derived distillates and those adjacent to sills contained essentially no lipids. Curie point pyrolysis combined with GC and GC-MS was used to show that kerogens from the unaltered samples reflected their predominantly autochthonous microbial origin. Pyrograms of the altered kerogens were much less complex than the unaltered samples, reflecting the thermal effects. The kerogens adjacent to the sills produce little or no pyrolysis products since these intrusions into unconsolidated, wet sediments resulted in in situ pyrolysis of the organic matter.Examination of the kerogens by ESR showed that spin density and line width pass through a maximum during the course of alteration but ESR g-values show no correlation with maturity. Stable carbon isotope (δ¹³C) values of kerogens decrease by 1–1.5‰ near the sills at Sites 477 and 481 and the atomic N/C decreases slightly with proximity to a smaller sill at Site 478. Differences in maturation behavior between Site 477 and 481 and Site 478 are attributed to dissimilarities in thermal stress and to chemical and isotopic heterogeneity of Guaymas Basin protokerogen.     

Seismicity and tectonics of southern Central America and adjacent regions with special attention to the surroundings of Panama

Ten new focal mechanisms are derived for earthquakes in southern Central America and its adjacent regions. These are combined with a study of seismicity and data of previous workers to delineate the position and nature of the plate boundaries in this complex region.The Middle America subduction zone may be divided into four or five distinct seismic segments. The plate boundary between North America and the Caribbean near the trench might be located more towards the south than previously suspected. Subduction has basically stopped south of the underthrusting Cocos Ridge. There is not much evidence for a seismically active strike-slip fault south of Panama, but its existence cannot be ruled out. More activity reveals the zone north of Panama which is identified as a subduction zone with normal fault events. Shallow seismicity induced by the interaction of the Nazca plate extends from the Colombia-Panama border south along the Pacific coast to meet a high-angle continental thrust fault system. Subduction with a pronounced slab starts only south of that point near a hot region which offsets the seismic trend at the trench. The Carnegie Ridge and/or the change of direction of subduction in Ecuador produce a highly active zone of seismicity mainly at the depth of 200 km. The area in the Pacific displays a termination of activity at a propagating rift west of the Galapagos Islands. The main eastern boundary of the Cocos plate, the Panama Fracture Zone, is offset towards the west at the southern end of the Malpelo Ridge. Its northern end consists of two active branches as defined by large earthquakes. A strike-slip mechanism near the southeastern flank of the Cocos Ridge was previously believed to be the site of an extended fracture zone. This paper proposes submarine volcanic activity as an alternative explanation.     

Cyclic terpenoids of contemporary resinous plant detritus and of fossil woods, ambers and coals

Cyclic terpenoids present in the solvent extractable material of fossil woods, ambers and brown coals have been analyzed. The sample series chosen consisted of wood remains preserved in Holocene to Jurassic sediments and a set of of ambers from the Philippines (copalite), Israel, Canada and Dominican Republic. The brown coals selected were from the Fortuna Garsdorf Mine and Miocene formations on Fiji.The fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons, and aromatized species were present at high concentrations, with a major amount of two-ring aromatic compounds. Tricyclic diterpenoids were the predominant compounds in the ambers. Aromatized derivatives were the major components, consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons. The saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon (C₁, C₂, etc.) substituents. Kaurane and phyllocladane isomers were present in only minor amounts. Bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples, but only traces of sesterterpenoids and triterpenoid derivatives were found.The brown coal extracts were composed of major amounts of one- and two-ring aromatized terpenoids, with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers. This was especially noticeable for the German coal, where the triterpenoids were predominant. Open C-ring aromatized structures were also present in this coal. Steroid compounds were not detectable, but some hopanes were found as minor components in the German brown coal.An overview of the skeletal structure classes identified in each sample, as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper. It can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis, constituting a general pathway for all terpenoids.     

Single-zircon evaporation combined with Pb+ emitter bedding for 207Pb/206Pb-age investigations using thermal ion mass spectrometry,and implications to zirconology

The internal precision of Pb isotope analyses using single-zircon evaporation in a double-filament solid source mass spectrometer (Kober 1986) can be improved combining the evaporation of Pb directly from the single grain with a suitable Pb⁺ emitter-bedding technique. This is most easily done by step-wise evaporating the investigated grain at temperatures of 1700–1800 K generating on the ‘cold’ ionization filament a deposit of radiogenic Pb together with further elements and compounds derived directly from the crystal. The heating of the deposit on the ionization filament to 1400–1500 K results in long-lived and stable Pb⁺ ion beams. The ‘activating reagents’ in the deposit are HfO₂ and SiO₂. Their release from the zircon grain together with the radiogenic Pb, which presumably is sited in the crystalline zircon domains as Pb⁴⁺, is probably due to disintegration reactions of trace-element silicates hosted in the grain. In the bedding deposited on the ionization filament thermally stable Pb/Hf/SiO₂ compounds are formed (PbHfSiO₅(?)). They retain the Pb isotopes on the (Re) filament up to 1400 K–1500 K and are highly efficient Pb⁺ ion emitters similar to the ‘Si-gel’-method (Cameron et al. 1969). The combined evaporation/emitter-bedding technique has been applied to natural zircons of different genesis and to isotope standards. Routinely, a Pb⁺ ion yield of 2*10^?4-1*10^?3 and a relative standard deviation of the ²⁰⁷Pb/²⁰⁶Pb ratio in the order of 1% have been obtained for sub-ng- to ng-amounts of Pb from standards and samples. The method rapidly can yield Pb isotope information on the ‘concordant’ zircon phases with a standard deviation of ±15–20 Ma of the derived ages also in the case of Paleozoic zircon populations.     

Molybdenum distribution in Precambrian rocks of the Colorado Mineral Belt

The average Mo content of more than one hundred rock samples from the Precambrian basement of the Colorado Mineral Belt corresponds well to the global molybdenum content of crustal rocks of 1.0 ppm. There are no indications of a regional geochemical molybdenum anomaly in that part of the crust or upper mantle.     

Bitumen from Coalport tar tunnel

The Coalport (Shropshire, U.K.) Tar Tunnel bitumen has been known since 1787 and the first geochemical data are reported here. The bitumen was analyzed for molecular markers useful for correlational studies. Gas chromatographic analysis of aliphatic and aromatic hydrocarbons failed to detect any specific major components normally used for genetic correlational and maturational studies. A search for minor and trace components by gas chromatographic-mass fragmentographic analysis showed the presence of triterpenoid hydrocarbons primarily of the 17α (H)-hopane series (C₂₇ to C₃₅, ex. C₂₈) and a C₂₆ to C₃₁ series of ring A/B demethylated hopanes. Two homologous sterane series (C₂₇ to C₂₉) of the 5α, 14β, 17β (H)-sterane and 13β, 17α (H)-diasterane type were also detected. Pophyrins of the DPEP and etio series (C₂₇ to C₄₁, DPEP/etio > 1) were also found. Characterization of their alkyl substitution pattern demonstrated C₁, C₂ and C₃ substituents on the pyrole moieties of the parent petroporphyrins.The molecular markers detected in this bitumen indicate its biogenic origin and show evidence of diagenetic and geothermal maturation processes. The overall geochemical characteristics of the Coalport Tar Tunnel bitumen suggest that it corresponds to a well matured crude oil, which was heavily altered by in-reservoir biodegradation or close to surface exposure.     

Application of the Mussel Watch concept in studies of the distribution of hydrocarbons in the coastal zone of the Ebro Delta

The Mussel Watch concept was applied in a study of man-induced chemical changes in the Ebro Delta on the Catalonian coast to obtain a preliminary assessment of the distribution of synthetic organic compounds, petroleum and biogenic hydrocarbons in the local coastal zone. Mussels, oysters and clams were selected as the indicator organisms. Levels of petroleum accumulated by mussels were generally high, in the order of 100–800 μg^?1 dry weight, equivalent to those in mussels in the most polluted harbours and bays of California. The relative distributions of the steranes and pentacyclic triterpanes in the mussels were significantly different from those found in petroleum from a local field, indicating that local petroleum was not contributing to the present contamination. The composition of biogenic compounds was variable, probably reflecting differences in the composition of local plankton communities, PCB levels were high in relation to current levels in mussels from US sites, reflecting continuing PCB use in Spain. The Delta appears to be a point source of a number of organochlorine compounds, including HCB, the DDT compounds, endrin and γ-chlordane. Levels of the DDT compound o,p′-DDD, a pharmacologically active substance, were unexpectedly high; identification was confirmed by GS/MS. Many unidentified peaks were present on EC chromatograms, indicating a more complex pattern of contamination than might be suggested by printed summaries of data.     

Distribution of hydrocarbons in the oyster,Pinctada margaratifera,along the coast of Kuwait

Concentrations of total hydrocarbons within the boiling point range of the alkanes n-C₁₄ and n-C₃₂ were determined in oysters, Pinctada margaratifera, from coastal waters of Kuwait. Levels of petroleum-derived hydrocarbons were highest in an area adjacent to the major oil loading facilities. Whether the use of dispersants to treat minor spills increases levels of incorporation of petroleum compounds into the food webs could not be concluded from the data of this study. Levels of total petroleum-type hydrocarbons in the oysters at this site were equivalent to those in mussels, Mytilus sp., from harbours, bays and urban coastal areas of California. The Kuwaiti oysters lacked a C₂₈ pentacyclic triterpane that was present in extracts of mussels from southern California that had been recently exposed to a minor spill or to a natural seepage. Levels of DDE and PCB were comparable to those in relatively unpolluted areas of North America.