Platinum-group element mineralisation in the Unst ophiolite, Shetland

The ophiolitic basic and ultrabasic rocks of the island of Unst, Shetland comprise a sequence of harzburgites, dunites, clinopyroxene-rich cumulates, and gabbro, within tectonic blocks that have been thrust over a migmatite complex during the Laxer Palaeozoic. Concentrations of chromite are found in the harzburgite and dunite, and to a small extent in the pyroxene cumulate rocks. They occur as disseminations, sometimes forming millimetre scale layers, and as more massive schlieren and pods of chromitite. Five alteration or hydrothermal events have been recognised in the ultrabasic rocks. These comprise early pervasive serpentinisation, later fracture controlled serpentinisation, veining and pervasive carbonation, minor late serpentine veining and talc-carbonate alteration controlled by fault zones. Exploration for platinum group element (PGE) mineralisation uas carried out using a combination of drainage, overburden and rock sampling. Analyses of PGE were obtained by fire assay followed by either neutron activation analysis or flameless atomic absorption spectrometry, and up to 20 other elements Here determined by X-ray fluoresence analysis. Panned concentrate samples were taken from 73 drainage sites distributed throughout the complex. Ir, the only PGE determined in all samples, showed a greater concentration in samples derived from the harzburgite unit than those from other units. Lox amplitude anomalies are present in three discrete areas in the harzburgite but the maximum level of 210 ppb Ir is associated with a sample derived from a prominent N-S zone of faulting and hydrothermal activity markedly discordant to the regional trend of layering in the harzburgite and dunite. This discordant zone, which extends for at least 7 km, is also marked by samples containing enrichments in Fe, Co, Ni, Cu and As. The highest Cr levels are associated with an area in the north of the harzburgite with no previous history of chromite working but where many locally derived pieces of chromitite float have been discovered. Relatively high Cr levels are also associated nith the area of dunite containing the greatest concentration of visible chromite and old norkings. A technique of collecting panned heavy mineral concentrates from overburden samples was adopted as a reconnaissance exploration technique after orientation sampling in the harzburgite unit at Cliff, an area with high PGE levels in chromitite and associated dunite. Systematic sampling in the Cliff area outlined a zone of coincident Pd, Pt and Rh enrichment near to but separate from the chromite workings knorrn to be enriched in PGE. In contrast the distribution of Ru was entirely different with scattered lon amplitude anomalous zones and a maximum anomaly 300m from the chromite-rich zone. Reconnaissance lines were sampled at other locations within the harzburgite, dunite and cumulate units. Lore amplitude Pd and Pt anomalies were detected xithin the dunite unit, especially in 'a traverse across the trace of the prominent N-S fault zone at Helliers Uater, adjacent to the outcrop of the cumulate unit. In general the overburden data suggest some association between PGE enrichment and enhanced levels of Ni relative to typical silicate levels apparent when expressed as the ratio Ni/MgC. Rock samples Here collected from all parts of the complex, including most of the main chromitite workings. Very high levels of all PGE occur in samples of chromitite, chromite-rich dunite and dunite from the Cliff area, with a strong positive intercorrelation between all PGE. The proportions of the various PGE are very similar to those present in deposits in major layered basic/ultrabasic complexes like Bushveld and Stillwater, irith strong relative enrichment in Pd and Pt. These PGE proportions are completely different from the Ru-Ir-0s dominant assemblage typical of ophiolitic rocks. Associated with high levels of PGE are enrichments in Ni, Cu, As, Sb and Te. There is no correlation rrith Cr and some samples of chromitite from the Cliff area contain only background levels of PGE. High to moderate levels of PGE with the same proportions of elements as the Cliff samples also occur in samples of chromitite and serpentinised dunite from the dunite unit and in samples of pyroxenite from the cumulate unit, In contrast PGE-rich samples of chromitite from the harzburgite unit near Harold's Grave have entirely different proportions of PGE with Ru and Ir in greatest abundance. This PGE distribution is similar to that in some background samples of harzburgite and closely resembles the pattern found in typical ophiolites. The PGE in the Harold's Grave samples do not exhibit the Ni enhancement noted in the Cliff PGE mineralisation. In samples from the Cliff area the platinum-group minerals (PGM) sperrylite, stibiopalladinite, hollingnorthite, laurite and possibly irarsite have been identified, mostly as grains less than 10 microns in size. In chromite-rich rocks these minerals occur Rithin chlorite haloes around chromite, in the blackened altered rims of chromite grains and in interstitial Ni-rich serpentine/carbonate intergroxths in association with pentlandite, orcellite and other Ni sulphides and arsenides, sometimes spatially related to chlorite-carbonate-magnetite veins. They also occur as fine grains Rithin magnetite rims around chromite and in magnetite or carbonate veins in dunite. The Ni sulphide/arsenide assemblage associated Rith the PGH is characteristic of serpentinisation at temperatures less than 500'C, Rell belox the range of magmatic conditions. A hydrothermal origin for the PGE mineralisation is proposed, probably related to the second phase of serpentinisation. This involved the redistribution of Ni accompanied by the introduction of As, Sb and Te probably with a StrUCtUral Control. Pre-existing concentrations of chromite may have acted as a precipitation barrier causing rich PGH deposition in the alteration haloes around chromite grains. Continuous borehole or trench sections through mineralised zones are required to assess the economic significance of the PGE mineralisation. Nevertheless the high levels of PGE attained and the evidence of xidespread occurrence of the Cliff-type PGE enrichment are favourable indications. The PGE enrichments found in the cumulate complex are of potential interest as they may originally have been of magmatic origin. Larger tonnage targets may therefore be present in this unit compared Rith the likely size of structurally-controlled mineralisation elswhere in the complex

The Information Seeking Behaviour of Distance Learners: A Case Study of the University of London International Programmes

An examination of the information behaviour of distance learning students is described, based on a case study of the International Programmes of the University of London. A comprehensive literature analysis, and comparison of relevant information behaviour models were carried out, supported by a survey of student behaviour. Following a pilot study, the main survey gained responses from 649 students, in 81 countries and following diverse study programmes. A variety of inter-related factors were found to influence information behaviour, level and subject of study being most significant. Ease and speed of access, and familiarity of sources were predominant factors. An extension of Wilson's information behaviour model is proposed to cater for the specific features of the distance learning context

Aspect-oriented domain analysis

Dissertação de Mestrado em Engenharia InformáticaDomain analysis (DA) consists of analyzing properties, concepts and solutions for a given domain of application. Based on that information, decisions are made concerning the software development for future application within that domain. In DA, feature modeling is used to describe common and variable requirements for software systems. Nevertheless, they show a limited view of the domain. In the mean time, requirement approaches can be integrated to specify the domain requirements. Among them, we have viewpoint oriented approaches that stand out by their simplicity, and efficiency organizing requirements. However, none of them deals with modularization of crosscutting subjects. A crosscutting subject can be spread out in several requirement documents. In this work we will use a viewpoint oriented approach to describe the domain requirements extended with aspects. Aspect-oriented domain analysis (AODA) is a growing area of interest as it addresses the problem of specifying crosscutting properties at the domain analysis level. The goal of this area is to obtain a better reuse at this abstraction level through the advantages of aspect orientation. The aim of this work is to propose an approach that extends domain analysis with aspects also using feature modeling and viewpoint

Viewpoints and goals: towards an integrated approach

Dissertação de Mestrado em Engenharia InformáticaRequirements elicitation and analysis have been studied according to several approaches that differ mostly on their "orientation", in this case relying on goals or viewpoints. Goal-Oriented approaches such as KAOS rely on goals to direct their process of eliciting requirements: a goal is an objective the system under consideration should achieve and represents a system property that may reflect either a functional (e.g. a service provided by the system) or a non-functional (e.g. security, performance) requirement; its satisfaction may imply the participation of several agents and the resolution of possible obstacles that may arise. The KAOS approach offers an unambiguous method for requirement decomposition and may provide a set of heuristics to approaches where one does not exist. Viewpoint-Oriented approaches such as PREview focus on gathering information pertaining to the problem from several agents that may have different, often equally valid, and incomplete perspectives on the problem. These partial intakes reflect their different responsibilities, roles, goals, or interpretations of the information sources; hence the combination of the agent and its input on the system is called a viewpoint. PREview benefits from a particularly lightweight approach to requirements encapsulation, but fails to provide a set of heuristics for the process of identifying the system's requirements. Considering the issues identified in each approach, it is verifiable that both approaches are complementary: on the one hand, KAOS offers a set of requirements elicitation heuristics through goal decomposition; on the other hand, PREview is a lightweight approach to viewpoint oriented requirements engineering, tailored especially for integration, however lacks a more systematic mechanism to guide the requirements elicitation process. The objective of this dissertation is therefore to propose a hybrid approach that builds on the PREview approach and brings together the benefits of the KAOS approach. The result is synergetic where, for example, completion is better addressed by providing a set of heuristics for requirement elicitation

Efficiency of e-learning in an information literacy course for medical students at the Masaryk University

Purpose: The main goal of this paper is to argue E-learning can be a viable alternative teaching method for Information Literacy according to a comparation of librarian’s time spent face-to-face teaching with tutoring the E-learning course, average time spent a week on learning by the students, time flexibility of E-learning, students’ satisfaction with E-learning and students’ ability to gain practical skills and theoretical knowledge through E-learning. Design/methodology/approach: Satisfaction of medical students with E-learning and their average weekly time spent learning was assessed through surveys designed in Google Documents. Weekly time spent by students learning in class and the number of librarian teaching hours were set by the university schedule and time spent on tutoring E-learning was measured. Details of accesses to study materials and submission of tasks as well as exam results were collected from Masaryk University Learning Management System. Findings: In 2011 50% less time was expended on tutoring E-learning than time spent with the same number of students in the previous three years in the classroom. One third of the students learned for more hours a week with E-learning than students in class. No significant difference in gained theoretical knowledge between these students was found. On average 90% of tasks submitted to E-learning were correct the first time. E-learning was appreciated by the students for its time (93%) and space (83 %) flexibility, the online materials (62%) and self-managing learning time (55%). Details of access to the study materials confirmed time flexibility. Originality/value: Due to time saved and considering the lack of any significant difference in the knowledge gained by students, E-learning can be a viable alternative teaching method for Information Literacy

Formal Desingularization of Surfaces - The Jung Method Revisited -

In this paper we propose the concept of formal desingularizations as a substitute for the resolution of algebraic varieties. Though a usual resolution of algebraic varieties provides more information on the structure of singularities there is evidence that the weaker concept is enough for many computational purposes. We give a detailed study of the Jung method and show how it facilitates an efficient computation of formal desingularizations for projective surfaces over a field of characteristic zero, not necessarily algebraically closed. The paper includes a generalization of Duval's Theorem on rational Puiseux parametrizations to the multivariate case and a detailed description of a system for multivariate algebraic power series computations.Comment: 33 pages, 2 figure

Typeface effects in written language: functions of typeface change for signalling meaning within text

Typeface change is one of the resources of written language which, in combination with other paralinguistic signs available to that system (use of space, punctuation, syntax manipulation are examples), can facilitate the author's intended interpretation. The thirteen studies undertaken for this research project explored the effects of typeface manipulations upon subjects' interpretations of brief texts, testing the efficiency of two conventional forms of emphasis, capital letters and italic print. Studies one to four specifically addressed issues of distinction between the two typefaces. It was found that both forms of typeface could function to intensify certain adjectives on a simple measurement scale, with capital letters providing quantifiably `more' to a referent than italics, as italics did over plain case. Both typefaces were tested for their ability to provide modulatory or contrastive emphasis for a word, where it was found that effects differed between the typefaces, suggesting divergent functions. Subjects' responses to a direct request to describe differences between capital and italic print, supported these findings. Studies five to nine examined the effects of typeface change and sentence sequence upon texts, by asking subjects to rank versions where these variables were manipulated. Strong concordances were found to be linked to information structure within the texts. Study ten took the same set of texts and presented versions individually to subjects in a story continuation task. The effects of emphasis and information sequence which were found suggest again the importance of content, which cooperated or conflicted with other paralinguistic signals in a text. The `foregrounding' effect of typeface emphasis on secondary information increased its availability for the production of continuation content. Studies eleven to thirteen looked at typeface change as a facility for signalling theme maintenance or enhancement, operating to disambiguate texts by reinforcing their `default' or natural readings, as well as its efficiency in signalling theme shift by contrastive emphasis. Different strategies of typeface emphasis were found to function for each of these requirements. Throughout all the studies, both forms of typeface emphasis were tested, either in contrast or in combination. Evidence accumulated to suggest that capital letters functioned best for providing modulatory emphasis, italic print for contrastive. Outside this issue of individual differences, typeface change itself was found to be an efficient strategy for indicating the author's intended interpretation to the reader

The social teaching of St Paul

https://place.asburyseminary.edu/ecommonsatsdigitalresources/1485/thumbnail.jp