Precise Determination of Silicon Isotopes in Silicate Rock Reference Materials by MC‐ICP‐MS

A HF‐free sample preparation method was used to purify silicon in twelve geological RMs. Silicon isotope compositions were determined using a Neptune instrument multi‐collector‐ICP‐MS in high‐resolution mode, which allowed separation of the silicon isotope plateaus from their interferences. A 1 μg g^‐1 Mg spike was added to each sample and standard solution for online mass bias drift correction. δ³⁰Si and δ²⁹Si values are expressed in per mil (‰), relative to the NIST SRM 8546 (NBS‐28) international isotopic RM. The total variation of δ³⁰Si in the geological reference samples analysed in this study ranged from ‐0.13‰ to ‐0.29‰. Comparison with δ²⁹Si values shows that these isotopic fractionations were mass dependent. IRMM‐17 yielded a δ³⁰Si value of ‐1.41 ± 0.07‰ (2s, n = 12) in agreement with previous data. The long‐term reproducibility for natural samples obtained on BHVO‐2 yielded δ³⁰Si = ‐0.27 ± 0.08‰ (2s, n = 42) on a 12 month time scale. An in‐house Si reference sample was produced to check for the long‐term reproducibility of a mono‐elemental sample solution; this yielded a comparable uncertainty of ± 0.07‰ (2s, n = 24) over 5 months.     

GSD‐1G and MPI‐DING Reference Glasses for In Situ and Bulk Isotopic Determination

This paper contains the results of an extensive isotopic study of United States Geological Survey GSD‐1G and MPI‐DING reference glasses. Thirteen different laboratories were involved using high‐precision bulk (TIMS, MC‐ICP‐MS) and microanalytical (LA‐MC‐ICP‐MS, LA‐ICP‐MS) techniques. Detailed studies were performed to demonstrate the large‐scale and small‐scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD‐1G and the MPI‐DING glasses are suitable reference materials for microanalytical and bulk analytical purposes.     

Precipitation anomalies,economic production,and the role of “first-nature” and “second-nature” geographies: A disaggregated analysis in high-income countries

Linkages between hydroclimate variability and economic development are often theorized to be present only in developing economies. Using spatially small-scaled data from multiple decades for European regions, we examine the relationship between precipitation anomalies and economic performance in highly developed economic systems. We conduct a disaggregated empirical analysis to mitigate the bias potentially arising from spatial aggregation because precipitation realizations tend to vary drastically within larger sized economic units. We modify original precipitation indices to capture the dynamic expectation formation of economic agents about climate conditions to measure deviations from these anticipated environmental states. Using panel model regressions in a quasi-experimental research design, we analyse whether deviations from average growth rates of aggregated economic output are potentially non-linearly related to the magnitude of precipitation deviations from the anticipated climate norm within regions, after accounting for any shocks common to all regions. We find that precipitation deviations that exceed critical thresholds (intermediate anomalies) for both unusually dry and unusually wet years reduce regional growth rates. The adverse impacts are more pronounced for overly dry periods. Importantly, the relationship between economic growth and precipitation anomalies is not generalizable across all regions. Natural geographical circumstances such as prevailing climatic conditions (“first-nature” geographies) and human-made socio-economic factors such as sector structure and income level (“second-nature” geographies) moderate the anomaly response. The empirical findings substantiate the necessity to incorporate precipitation variability into the assessment of economic costs of climate change; not only in developing countries or agricultural societies but also in highly developed economic systems. Moreover, the empirical results have important implications for policy makers as uneven effect sizes at the subnational level suggest that policy measures should be targeted in space and coordinated between national and regional levels of government.     

Late Quaternary palaeohydrological changes in the large playa Lake Frome in central Australia, recorded from the Mg/Ca and Sr/Ca in ostracod valves and biotic remains

The last 42,000 years of hydrological history of Lake Frome, a large playa located in the arid part of northern South Australia, which is hypersaline and most often dry today, is reconstructed using a combination of ostracod assemblages, other microfossil remains, and the trace elemental composition of the selected halobiont ostracod species of Diacypris and Reticypris.The Mg/Ca and Sr/Ca of ostracod valves from 2 cores relate to significant hydrological changes that affected the lake over time. The reconstruction of the Sr/Ca of the lake’s waters, based on the Sr/Ca of ostracod shells, shows that when the lake fills the waters originate mostly from runoff, not from hypersaline waters located below the lake or the surrounding aquifers. The Last Glacial Maximum saw gypsum deflation from the lake.Prior to 25K yBP, Frome had a stable hydrological regime, permanent water and low salinities, with occasional freshwater conditions between 42 and 33K yBP. From 25 to 20.3K yBP, salinities fluctuated and ephemeral conditions operated. After that, until ∼14.8K yBP, a brine pool was located below the lake and was therefore under a different hydrological regime. Between 13 and 11.2K yBP, wet conditions occurred, but such conditions were not seen again during the Holocene.     

Preliminary limits of a logarithmic correction to the Newtonian gravitational potential in binary pulsars

We obtain preliminary limits on a logarithmic correction to the Newtonian gravitational potential by using five binary pulsars:PSR J0737-3039,PSR B1534+12,PSR J1756-2251,PSR B1913+16 and PSR B2127+11C.This kind of correction may originate from fundamental frameworks,like string theories,effective models of gravity due to quantum effects and the non-local gravity scheme.We estimate the upper limit of the Tohline-Kuhn-Kruglyak parameter λ and the lower limit of the FabrisCampos parameter a,which parameterize the correction and are connected to each other by αλ=—1.By analyzing the advances of periastron of these binary pulsars,we find that the preliminary upper limit of α is 0.19±0.14 kpc~(-1) and the preliminary lower limit of λ is-5.2±3.8 kpc.They are compatible with the bounds based on dynamics of spiral galaxies but quite different from those given by solar system dynamics.These results indicate that this logarithmic correction might be more observable in current timings of binary pulsars than in motions of the solar system.     

Polarimetry and Photometry of Comet C/2004 Q2 (Machholz)

We present results of polarimetry and photometry of comet C/2004 Q2 (Machholz) obtained with the 0.7-m telescope of Institute of Astronomy at the Karazin Kharkiv National University on February 3 and 4, and March 4 and 14, 2005. The observations were carried out with a one-channel photoelectric photometer-polarimeter. The IHW continuum UC (λ3650/80 Å), BC (λ4845/65 Å), RC (λ6840/90 Å) and emission filters CN (λ3871/50 Å), C₃ (λ4060/70 Å), and C2 (λ5140/90 Å) were used. Degree of the comet polarization at phase angles ≈ 52° and ≈44° in the red continuum was close to that for so called dusty comets. The comet had a typical spectral gradient of polarization ΔP/Δλ=0.86% per 1000 Å. In the framework of the Haser model we have found the gas production rates Q of the CN, C₃ and C₂ species and the dust production rates Afρ on February 4 and March 14, 2005. The ratio log[Afρ (BC)/Q(CN)] was compared with data for other comets. The normalized spectral gradient of cometary dust S’(BC,RC) was 8.7%/1000 Å for February 4 and 17.0%/1000 Å for March 14. We conclude that comet C/2004 Q2 (Machholz) in many respects is a typical dusty comet.     

Glaciotectonised Quaternary sediments at Cape Shpindler,Yugorski Peninsula,Arctic Russia: implications for glacial history,ice movements and Kara Sea Ice Sheet configuration

The coastal cliffs of Cape Shpindler, Yugorski Peninsula, Arctic Russia, occupy a key position for recording overriding ice sheets during past glaciations in the Kara Sea area, either from the Kara Sea shelf or the uplands of Yugorski Peninsula/Polar Urals. This study on Late Quaternary glacial stratigraphy and glaciotectonic structures of the Cape Shpindler coastal cliffs records two glacier advances and two ice‐free periods older than the Holocene. During interglacial conditions, a sequence of marine to fluvial sediments was deposited. This was followed by a glacial event when ice moved southwards from an ice‐divide over Novaya Zemlya and overrode and disturbed the interglacial sediments. After a second period of fluvial deposition, under interstadial or interglacial conditions, the area was again subject to glacial overriding, with the ice moving northwards from an inland ice divide. The age‐control suggests that the older glacial event could possibly belong to marine oxygen isotope stage (MOIS) 8, Drenthe (300–250 ka), and that the underlying interglacial sediments might be Holsteinian (>300 ka). One implication of this is that relict glacier ice, buried in sediments and incorporated into the permafrost, may survive several interglacial and interstadial events. The younger glacial event recognised in the Cape Shpindler sequence is interpreted to be of Early‐to‐Middle Weichselian age. It is suggested to correlate to a regional glaciation around 90 or 60 ka. The Cape Shpindler record suggests more complex glacial dynamics during that glaciation than can be explained by a concentric ice sheet located in the Kara Sea, as suggested by recent geological and model studies. Copyright © 2003 John Wiley & Sons, Ltd.