106 research outputs found
Optically stimulated luminescence dating of sublittoral and intertidal sediments from Dubai UAE.: Radioactive disequilibria in the uranium decay series
No full textCosmic pears from the Havelland (Germany): Ribbeck, the twelfth recorded aubrite fall in history
No full textAbstract In 1889 the German poet and novelist Theodor Fontane wrote the popular literary ballad “Herr von Ribbeck auf Ribbeck im Havelland.” The Squire von Ribbeck is described as a gentle and generous person, who often gives away pears from his pear trees to children passing by and continued donating pears after his death. Now, 135 years later the rock called Ribbeck is giving us insight into processes that happened 4.5 billion years ago. The meteorite Ribbeck (official find location: 52°37′15″N, 12°45′40″E) fell January 21, 2024, and has been classified as a brecciated aubrite. This meteoroid actually entered the Earth's atmosphere at 00:32:38 UTC over Brandenburg, west of Berlin, and the corresponding fireball was recorded by professional all sky and video cameras. More than 200 pieces (two proved by radionuclide analysis to belong to this fresh fall) were recovered totaling about 1.8 kg. Long‐lived radionuclide and noble gas data are consistent with long cosmic ray exposure (55–62 Ma) and a preatmospheric radius of Ribbeck between 20 and 30 cm. The heavily brecciated aubrite consists of major (76 ± 3 vol%) coarse‐grained FeO‐free enstatite (En 99.1 Fs <0.04 Wo 0.9 ), with a significant abundance (15.0 ± 2.5 vol%) of albitic plagioclase (Ab 95.3 An 2.0 Or 2.7 ), minor forsterite (5.5 ± 1.5 vol%; Fo 99.9 ) and 3.5 ± 1.0 vol% of opaque phases (mainly sulfides and metals) with traces of nearly FeO‐free diopside (En 53.2 Wo 46.8 ) and K‐feldspar (Ab 4.6 Or 95.4 ). The rock has a shock degree of S3 (U‐S3), and terrestrial weathering has affected metals and sulfides, resulting in the brownish appearance of rock pieces and the partial destruction of certain sulfides already within days after the fall. The bulk chemical data confirm the feldspar‐bearing aubritic composition. Ribbeck is closely related to the aubrite Bishopville. Ribbeck does not contain solar wind implanted gases and is a fragmental breccia. Concerning the Ti‐ and O‐isotope compositions, the data are similar to those of other aubrites. They are also similar to E chondrites and fall close to the data point for the bulk silicate Earth (BSE). Before the Ribbeck meteoroid entered Earth's atmosphere, it was observed in space as asteroid 2024 BX1. The aphelion distance of 2024 BX1's orbit lies in the innermost region of the asteroid belt, which is populated by the Hungaria family of minor planets characterized by their E/X‐type taxonomy and considered as the likely source of aubrites. The spectral comparison of an average large‐scale emission spectrum of Mercury converted into reflectance and of the Ribbeck meteorite spectrum does not show any meaningful similarities
The anomalous polymict ordinary chondrite breccia of Elmshorn ( H3 ‐6)—Late reaccretion after collision between two ordinary chondrite parent bodies, complete disruption, and mixing possibly about 2.8 Gyr ago
No full textAbstract Elmshorn fell April 25, 2023, about 30 km northwest of the city of Hamburg (Germany). Shortly after the fall, 21 pieces were recovered totaling a mass of 4277 g. Elmshorn is a polymict and anomalous H3‐6 chondritic, fragmental breccia. The rock is a mixture of typical H chondrite lithologies and clasts of intermediate H/L (or L, based on magnetic properties) chondrite origin. In some of the 21 pieces, the H chondrite lithologies dominate, while in others the H/L (or L) chondrite components are prevalent. The H/L chondrite assignment of these components is based on the mean composition of their olivines in equilibrated type 4 fragments (~Fa 21–22 ). The physical properties like density (3.34 g cm −3 ) and magnetic susceptibility (log χ <5.0, with χ in 10 −9 m 3 kg −1 ) are typical for L chondrites, which is inconsistent with the oxygen isotope compositions: all eight O isotope analyses from two different fragments clearly fall into the H chondrite field. Thus, the fragments found in the strewn field vary in mineralogy, mineral chemistry, and physical properties but not in O isotope characteristics. The sample most intensively studied belongs to the stones dominated by H chondrite lithologies. The chemical composition and nucleosynthetic Cr and Ti isotope data are typical for ordinary chondrites. The noble gases in Elmshorn represent a mixture between cosmogenic, radiogenic, and primordially trapped noble gases, while a solar wind component can be excluded. Because the chondritic rock of Elmshorn contains (a) H chondrite parent body interior materials (of types 5 and 6), (b) chondrite parent body near‐surface materials (of types 3 and 4), (c) fragments of an H/L chondrite (dominant in many stones), (d) shock‐darkened fragments, and (e) clasts of various types of impact melts but no solar wind‐implanted noble gases, the different components cannot have been part of a parent body regolith. The most straightforward explanation is that the fragmental breccia of Elmshorn represents a reaccreted rock after a catastrophic collision between an H chondrite parent body and another body with H/L (or L) chondrite characteristics but with deviating O isotope values (i.e. that of H chondrites), complete disruption of the bodies, mixing, and reassembly. This is the only straightforward way that the implantation of solar wind gases could have been avoided in this kind of complex breccia. The gas retention ages of about 2.8 Gyr possibly indicate the closure time after the catastrophic collision between H and H/L (or L) chondrite parent bodies, while the cosmic ray exposure age for Elmshorn, which had a preatmospheric radius of 25–40 cm, is ~17–20 Myr.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659Alexander von Humboldt-Stiftung https://doi.org/10.13039/10000515
Gamma-spectrometric analysis of high salinity fluids – how to analyze radionuclides of the thorium decay chain far from radioactive equilibrium?
No full textIndigenous knowledge systems or practical everyday performances? A theoretical reconsideration of indigenous knowledge in anthropology and development studies
No full textThis article was written by Detlev Krige before he joined the University of Pretoria.Much recent writing in the social sciences - boosted by inter alia substantial
funding programmes and valid questions concerning the relationship between
identity politics, knowledge and power - have applauded the formulation of
and research into various forms of Indigenous Knowledge Systems (lKS).
This interest in and advocacy for IKS, at times formulated in the context of
debates on postcolonial identity as an alternative to paradigms constructed on
particular Western-scientific assumptions, has run parallel to a more general
shift in thinking about development initiatives as requiring participatory
research methodologies and bottom-up implementation strategies. Within
development studies and anthropology, this shift has stimulated much
research on localised knowledge practices. There is, however, little evidence
that this body of anthropological (and ethnographic) literature has informed
the thinking of those writing and working within the theoretical paradigm of
Indigenous Knowledge Systems (lKS). Making use of a number of recent
ethnographic studies on Africa, the author argues for a theoretical
reconsideration of the IKS paradigm. He highlights important criticisms of the
ways in which many indigenous knowledge systems proponents essentialise
concepts such as knowledge and culture, as well as the methodological
limitations of much current IKS research. It is argued that a focus on the nonverbal
and local knowledge embodied in everyday practices, as well as the
performance of such knowledge, signals not only the limitations of much IKS
research but also redirects our attention to reformulating and invigorating
ideas about much needed local research
How well suited are current thermodynamic models to predict or interpret the composition of (Ba,Sr)SO₄ solid-solutions in geothermal scalings?
No full textIn this study, we report results of the analysis of a particularly interesting scaling sample
from the geothermal plant in Neustadt-Glewe in northern Germany, which contained
19% Galena (PbS) and 81% of a heterogeneous assemblage of (Ba,Sr)SO₄ crystals with
varying compositions, 0.15 < X < 0.53. A main fraction of the sample (~56%) has a
barite content of X ≈ 0.32. We try to relate the solid composition of the (Ba,Sr)SO₄
solid-solution to the conditions at the geothermal plant concerning temperature,
pressure, and solution composition, and discuss it with respect to the challenges in
modelling the composition of (Ba,Sr)SO₄ solid-solutions on the basis of thermodynamic
mixing models. We note that considerable uncertainties are related to the description
of (Ba,Sr)SO₄ formation by means of thermodynamic models. The scaling composition
observed in this study would be in line with endmember solubilities as predicted by
the PhreeqC-Pitzer database for 70 °C and an interaction parameter, a0 = 1.6. According
to such a model, the scaling heterogeneity would reflect bimodal precipitation
behaviour due to various degrees of depletion of the brine with respect to X(Ba)().
Minor fluctuations in X(Ba)(): 0.0017 < X(Ba)() < 0.0042 explain the full range of
observed solid compositions. The choice especially of the interaction parameter seems
to some extent arbitrary. This knowledge gap strongly limits the interpretation of (Ba,Sr)
SO₄ compositions. Thus, it is not possible to distinguish between kinetic and thermodynamic
effects on partitioning or to use the solid-solution composition to draw conclusions
about the precipitation conditions (e.g. Temperature)
Zehn lÿrische Selbst-Porträts ... /
No full textImprint date from Gesamtverzeichnis des deutschsprachigen Schrifttums (GV), 1700-1910.Introduction signed by the editor and publisher: Theodor Weicher.Includes poetry by each author.(from t.p.) Ferdinand von Saar -- Felix Dahn -- J. Trojan --Martin Greif -- Ernst von Wildenbruch -- Detlev von Liliencron -- Gustav Falke -- Arno Holz -- R. Dehmel -- Otto Julius Bierbaum.GV 1700-1910,Mode of access: Internet
‘We are running for a living’ : work, leisure and speculative accumulation in an underground numbers lottery in Johannesburg
No full textIn this paper the author presents a historically-informed ethnography of a Johannesburg underground lottery. The meaning of this lottery is tied up with the local-level sociological organisation of lottery banks and the various actors who participate in it, with changing notions of social class, work and leisure under the conditions of growing inequality and jobless economic growth, and with the everyday strategies and agency of lottery runners and punters. The author uses the instance of this lottery to argue for a contextualised, multi-leveled and historically-grounded interpretation of the notions 'occult economies' and 'mysterious modes of accumulation' (Comaroff & Comaroff 1999a, 2000). The prominence of speculative accumulation in the context of this lottery and in the livelihood strategies of those living at the margins of the state and society are strikingly similar to financial practices under the conditions of casino capitalism, financialisation and securitisation in financial markets. In this way the author links local practices of speculative accumulation with translocal processes generated by present-day neoliberal policies and financial capitalism.Wits Institute for Social and Economic Research (WISER), University of the Witwatersran
How well suited are current thermodynamic models to predict or interpret the composition of (Ba,Sr)SO4 solid-solutions in geothermal scalings?
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