1,846 research outputs found
Platinum-group mineralogy of the Fazenda Mirabela intrusion, Brazil: the role of high temperature liquids and sulphur loss
No full textTwo distinct platinum-group mineral (PGM) assemblages have been identified in the Fazenda Mirabela intrusion that hosts the Ni–Cu–platinum-group element (PGE) Santa Rita ore zone in Bahia State, north-eastern Brazil: (i) Pt–Pd–Ni tellurides accompanied by Ag–Te, with minor electrum and native Au, and (ii) Pd alloys accompanied by minor PGE arsenides and sulphides. Assemblage (i) is present in the Santa Rita ore zone and underlying S-poor footwall dunite whereas assemblage (ii) is observed in the dunite only. The assemblage (i) PGE tellurides crystallised from a late stage semimetal-rich PGE-bearing melt produced by sulphide fractionation and/or via exsolution from sulphides during subsolidus cooling. In assemblage (i) in the Santa Rita ore zone, PGM are also commonly found within base metal sulphide (BMS) veinlets which have either formed as a result of post-magmatic hydrothermal remobilisation or by the simultaneous crystallisation of PGM and BMS from a late stage volatile-rich melt. In the S-poor footwall dunite that hosts assemblage (ii), Pd alloys have formed through the interaction of sulphides with a late stage melt or high temperature hydrothermal fluid. This liquid had a high oxygen fugacity () that caused S loss evidenced by the formation of micro-scale textures that resemble symplectites or intergrowths of sulphides with olivine and occasionally orthopyroxene, and the formation of magnetite. During sulphur loss, semimetals (particularly Te) were also stripped from the dunite while PGE were expelled from the symplectite-like sulphides forming Pd alloys. PGE tellurides are present in the dunite where S and semimetals have not been completely stripped from the rock suggesting that this late stage melt or high temperature hydrothermal fluid was not pervasive throughout the dunite
The archaeoacoustics of San Vitale, Ravenna
No full textThis research tests and assesses whether sixth-century social and cultural dynamics can be archaeologically identified by including the study of acoustics in the context of extant Late Antique Christian architecture, namely the centrally planned domed octagonal church of San Vitale at Ravenna. Implementing a holistic archaeological research strategy that includes human sensory perception of acoustical phenomena is the best approach to unravelling the complexities of social and cultural mechanisms operating in the sixth-century Mediterranean basin. The methods and issues of Archaeoacoustics are critiqued and developed in order to comment on the intentionality of acoustic attributes in sixth-century ecclesiastical architecture.The space syntax of San Vitale has been considered for isovists at key locations during the liturgical procession and sequence of the Mass celebration. These are compared with mapped areas of perceiving the acoustic characteristics of Clarity and Reverberation Time. Combining the visual and acoustic analysis of San Vitale, with a better understanding of its date and construction phases, the physical geometry and temporal logic of the church are discussed in relation to the reflexive exchange of influence between Ravenna, Milan and Constantinople. It is posited that liturgical and musical time and tempo is materially expressed in the evident and conceptual substance of San Vitale, a suggestion that offers a springboard for future study and debate
Solution of the problem of composite charge using R.D.38
No full textIn this paper the author has solved the problem of internal ballistics of composite charge using 'R.D.38' method which is based upon the usual isothermal approximation. A linear law of burning has been assumed
Author index
No full textThe articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.This is a continuation of the "Author and Subject Index to the Onderstepoort Journal
of Veterinary Science and Animal Industry (1933- l950)" and the "Onderstepoort Journal
of Veterinary Research (1951 - 1968)" which appeared in June 1969 and covers the period
1969 to 1973, i.e. Volumes 36 to 40.
As from 1974 (Volume 41) it is intended to furnish an Author and Subject Index
in Number 4 of each volume covering all four numbers for that particular year
Noise due to unsteady flow past trailing edges
No full textThis paper presents two-dimensional direct numerical simulations (DNS) of noise generated at trailing edges (TE) with zero thickness. The simulations are conducted specifying either no-slip or slip walls in order to investigate viscous effects. In both cases, small amplitude disturbances are introduced close to the inflow boundary that serve as pressure disturbances at the TE. DNS data reveals that the unsteady Kutta condition is not satisfied, irrespective of the wall boundary condition. However, it appears that the validity of the unsteady Kutta condition is not essential for making an accurate prediction of the far field noise. The far field pressure is predicted as a function of the surface pressure difference using a 2-D modification of Amiet's classical theory, and compared with the far field pressure computed directly. Directivity plots provide evidence that the presence of boundary layers and noise generated by an unsteady wake in the no-slip cases lead to smearing of individual lobes, and that the downstream pointing lobes in no-slip wall cases are probably due to nonlinear noise generation in the wake. The simulations are conducted using a high-order accurate numerical method which is free of upwinding, artificial dissipation or any form of explicit filtering, and employs a novel boundary treatment
The Distribution of PGE and the Role of Arsenic as a Collector of PGE in the Spotted Quoll Nickel Ore Deposit in the Forrestania Greenstone Belt, Western Australia
No full textThe Spotted Quoll PGE-bearing Ni deposit in the Forrestania greenstone belt in the Archean Yilgarn block in Western Australia is a komatiite-associated massive sulfide orebody tectonically displaced from its original host. The brecciated ore contains clasts of quartz and garnet schist and is located along a shear zone overlain by banded iron formation (BIF) and underlain by BIF and quartz-biotite metasediments. The deformation of the ore has destroyed its magmatic textures and it has been sheared and recrystallized at amphibolite facies. Then the deformed ore has been subjected to a hydrothermal event that concentrated the PGE with Au and As, often at the edge of the Ni ore. The PGE are distributed between PGM and in solid solution in Ni sulfarsenides, and Pd also occurs in pentlandite. The PGM include sudburyite (PdSb), sperrylite (PtAs2), and irarsite (IrAsS). All six PGE and minor Au are hosted in gersdorffite (NiAsS). Two generations of gersdorffite have been recognized. A higher temperature magmatic euhedral Co-rich gersdorffite encloses Ir-, Pt- and Rh-bearing PGM surrounded by halos of Rh-, Ir-, and Os-rich gersdorffite. A lower temperature Ni-rich gersdorffite forms anhedral grains and rims on grains of nickeline (NiAs). In this low-temperature gersdorffite PGE are concentrated toward the mineral edges. Sudburyite and gold occur associated predominantly with nickeline. The PGE and gold are now predominantly associated with sulfarsenides that are the controlling factor for their distribution
Characteristic distribution and scale interaction of turbulence in a boundary layer
No full textThis work revisits the concept of turbulent boundary layers from a novel perspective on scale transfer. Turbulence production and dissipation together with the energy budgets are analyzed in the velocity gradient invariant phase space. In combination with filtering, the mechanism of scale coupling is investigated and illustrated for different characteristic flow topologies. The understanding of the scale coupling is important to model turbulence. Turbulence models describe the complex interaction of the scales of motion in a simplified form. The essential task of turbulence modeling is to capture the coupling of the modeled and unmodeled scales as well as the evolution of the modeled scales within the unmodeled flow. This work characterizes the scale coupling by focusing on the interfaces between modeled and unmodeled flow such as production and dissipation. The mechanisms that govern the evolution of the modeled quantities are investigated for their core properties and universal features. Direct numerical simulation (DNS) is carried out to obtain data of a compressible zero pressure-gradient flat plate turbulent boundary layer flow. This flow topology allows to unveil the effect of a wall on the coupling of scales and evolution of turbulence
Learning from One's Mistakes
No full textCreated by R.D. Lee for the Royal Statistics Society, this article describes an exercise, which highlights the effect of sampling without replacement in small populations, and leads to consideration of the relative importance of sample and population size when examining standard error. The author provides a number of exercises, an explanation of statistical errors and the importance of sample size. This is a brief, yet fine resource for those in the field of statistics
Mad to be Normal: Thoughts on Psychiatrist R.D Laing and Connections to Liberation Psychology
No full textThis article uses the film Mad to be Normal, about R.D. Laing, as an opening into the liberation psychology approaches of Martin-Baro. Examples from the author\u27s own clinical practice as well as personal experiences from life in a Catholic Worker community are included
R.D. Laing's language of experience
No full textThe radical psychiatrist R.D. Laing (1927-1989) was an accomplished author with an extensive philosophical knowledge that informed his ideas on reading, writing, and interpretation. Laing argues that psychiatry should be modeled on skilful textual exegesis rather than scientific explanation. The exegesis of a psychotic’s words and actions is difficult, he infers, because the impoverishment of our experience cuts us off from the sense that lies within seeming madness. Like philosophers such as Edmund Husserl, Laing therefore criticizes the way in which the natural sciences have invalidated subjective experience. He consequently employs a rhetoric designed to disclose with renewed vigor its complexity, variety and reality. Laing fails, however, to find an alternative to scientific reason: "experience", in his weakest work, is an irrational realm of mystical and self-validating certainty that closely parallels Heidegger’s later accounts of "Being"
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