Platinum-group elements in the ultrabasic rocks of the Braganca and Morais massifs, northern Portugal

The ultrabasic rocks studied in this thesis are located in the Upper Allochthonous Thrust Complex nappes of the Braganca and Morais massifs, Träs-os-Montes, N. Portugal. They are relicts of residual mantle and cumulates formed at a destructive continental margin. In the Braganca massif, the ultrabasic rocks consist mainly of a harzburgite formation, which is residual mantle. This formation contains lenses of a separate chromitite-bearing dunite formation. The Morais massif assemblage, at an equivalent structural level, is made up of peridotite and gabbroic/troctolitic cumulates. The chromitite-bearing dunite formation crystallised within small magmatic masses. This chromite crystallisation acted to fractionate the associated Platinum-Group Element (PGE) assemblage. Os, Ir and Ru were incorporated as laurite and irarsite minerals during chromite grain crystallisation, and are located in textural positions from the centres to the margins of the chromite grains. In contrast Pt-bearing arsenides and sulpharsenides started crystallising after the Os, Ir, Ru group, and are only located at the margins of or in between chromite grains. More fractionated assemblages show positive slopes on chondrite normalised whole rock PGE plots. Pd is not directly associated with this fractionation. Instead its mineralisation is associated with that of the base-metal sulphide. Serpentinisation has caused recrystallisation of much original pentlandite to heazlewoodite and magnetite. At the same time Pd-bearing alloys were created, mostly adjacent to sulphide grains with the source of the Pd being in solid solution within the base-metal sulphide. Several factors suggest that the chromite mineralisation was derived from melts of boninitic affinity. The relatively high Pd/Cu ratios calculated for a silicate melt from which the chromite crystallised are consistent with this. The composition of the chromite grains, having 1000r/(Cr+Al) ratios clustering around 75, is typical of boninitic magmas. In addition the refractory composition of the harzburgite formation, and the high tenors of Pd within sulphide, show that it was a possible source for such boninitic melts. The chromite mineralisation took place down to depths of 30km within the mantle wedge of a destructive continental margin

The Application of Elementary Statistics In Analysis of Data by Selected Secondary School Students

The purpose of this study was to determine the ability of apt secondary school students to apply principles of elementary probability and statistical inference in the analysis of data following a semester of instruction in statistics and elementary probability

Accuracy of Implied Volatility Approximations Using "Nearest-to-the-Money" Option Premiums

Implied volatility is a useful bit of information for futures and options hedgers and speculators. However, extraction of implied volatility from Black-Scholes (BS) option pricing model requires a numeric search. Since 1988, there have been numerous simplifying modifications to the BS formula proposed and presented in the applied economics and finance literature to allow approximation of implied volatility directly. This study identifies and tests these simplification methods for accuracy for call only and put-call average elicitation of an implied volatility estimate. Results show that accuracy varies by method and whether call only or put-call average approaches are applied.Marketing,

Lessons from the TAPS study - Errors relating to medical records

The Threats to Australian Patient Safety (TAPS) Study collected 648 anonymous reports about threats to patient safety from a representative random sample of Australian general practitioners. These contained any events the GPs felt should not have happened and would not want to happen again, regardless of who was at fault or the outcome of the event. This series of articles presents clinical lessons resulting from the TAPS study.2 page(s

Lessons from the TAPS study - Managing investigation results - is your practice system safe?

The TAPS study found that errors in the process of providing health care were reported by general practitioners more than twice as often as deficiencies in a clinician's knowledge or skills. Approximately 20% of these process error events concerned investigations. In addition, some reported events that related to investigations included filing system and recall errors, which accounted for a further 10% of reported error events.2 page(s

Reductions in turbidity and Escherichia coli density using passive polymer treatment

Current research shows sediment basins may act as reservoirs for potentially harmful bacteria, including Escherichia coli (E. coli). E. coli preferentially attach to clay-sized particles and have been found in sediment basin outflows with high turbidity levels containing concentrations exceeding water quality standards recommended by the US Environmental Protection Agency. Since research shows E. coli preferentially attach to the clay fraction within sediment, it was hypothesized that a reduction in turbidity and TSS would create a corresponding reduction in bacterial density.  Construction site sediment basin discharge was simulated to determine whether a sediment tube configuration using anionic polymer application could reduce E. coli densities. Based on prior research, reductions in turbidity and suspended sediment were maximized by applying 100 g of granular polyacrylamide (PAM) directly to each of five sediment tubes before simulated runoff events. PAM application successfully reduced turbidity and TSS by 96% and 92%, respectively. Discharge after the last sediment tube had an average turbidity of 80 NTU and TSS of 174 mg/L.  For the low E. coli density range (5,000–10,000 MPN/100 mL), PAM application failed to create a reduction in bacterial density, but rather an increase in E. coli was observed with an average discharge of 25,226 MPN/100 mL.  Within the high E. coli density range (100,000-200,000 MPN/100 mL), a 29% reduction was recorded with an average discharge of 135, 270 MPN/100 mL