Base metal mineralisation associated with Ordovician shales in south-west Scotland

Several narrow, lenticular belts of black cherty mudstone and siltstone (the Moffat Shales), alternating with thick greywacke sequences, strike north-east to south-west across Galloway with uniformly steep dip. In the Penkiln Burn area, 13 km NNE of Newton Stewart, one such belt is hornfelsed and considerably broadened near the southwest margin of the Loch Doon granitic pluton. Base metal anomalies in drainage and overburden are spatially associated with the broadened section of the shale belt, which is host to weakly disseminated and epigenetic Pb-Zn-Cu mineralisation. Within the Moffat Shale sequence highly siliceous mudstone and siltstone are interbedded with chert, greywacke and possibly thin tuffaceous horizons. The broadening is structurally controlled, caused by the interference of early structures with a major reciined fold plunging to the south-east. Several phases of faulting and minor intrusion have been recognised, and the abundance of dykes is an unusual geological feature of the area. Lead is particularly enriched in drainage samples, reaching approximately 1% in pan concentrates collected close to a mineralised gossan-like zone. The main leadbearing mineral identified in the anomalous concentrates, and the in situ gossan material, is the secondary lead phosphate plumbogummite. Overburden sampling proved anomalous metal values extending for 2.3 km along strike and 500 m across strike. Lead again shows the greatest enrichment, with values ranging up to about 0.5 % , in soil close to the gossan. Zinc and copper give a weaker response in both overburden and drainage, but drilling showed that zinc, in the form of disseminated sphalerite, has a greater incidence at depth than was suggested by the surface anomalies. Three varieties of mineralisation have been recognised. The earliest consists of fine disseminations, chiefly of sphalerite and pyrite, in the hornfelsed sediments. It is characterised by zinc levels between 500 and 1000 ppm over several metres of drill core; lead levels rarely exceed 300 ppm. The second phase of mineralisation occurs in thin quartz veinlets, which in this case contain accessory sphalerite, galena and pyrite. Where the veining is intense, lead concentrations reach 7000 ppm and those of zinc 1500 ppm, but these values persist over only a few tens of cm of core. Finally, a low-temperature mineral assemblage in which plumbogummite is dominant is associated with the altered margins of dykes and gossanlike zones occupying a north-south fault system. Lead levels in the dyke margins range up to 1.5 % in zones generally less than 50 cm thick, but 4.5 %I Pb has been recorded in one specimen from the exposed gossan. Fine stratiform pyrite iaminae in mudstone interbedded with chert containing disseminated pyrite and sphalerite suggests that at leas: some of the early mineralisation is synsedimentary. Later mineralisation phases are, however, structurally controlled and the origin of the majority of the base metal mineralisation remains problematical. The unusual abundance of minor intrusions in the mineralised zone is strong circumstantial evidence for an igneous source. Full details of the soil geochemical surveys and the geophysical surveys are available for inspection at the Keyworth office of BGS

Comparison of Nuclear Suppression Effects on Meson Production at High p_T and p_L

The medium effect on the pion distribution at high $p_T$ in $AA$ collisions is compared to that of the pion distribution at high $p_L$ in $pA$ collisions. Both the suppression of the spectra and the energy losses of the measured pions are studied. Although the medium effect on $p_T$ is larger than on $p_L$, the difference is found surprisingly to be not as big as one would naively expect.Comment: 8 RevTex pages with 5 figure

Nucleon participants or quark participants?

We show that centrality dependence of charged particle pseudorapidity density at midrapidity in Au+Au collisions at RHIC is well described as proportional to We show that centrality dependence of charged particle pseudorapidity density at midrapidity in Au+Au collisions at RHIC is well described as proportional to the number of participating constituent quarks. In this approach there is no need for an additional contribution from hard processes usually considered in the models based on the number of the nucleon participants.Comment: 3 pages, 4 figures, latex, version accepted for publication in Phys.Rev.

On the evolutionary optimisation of many conflicting objectives

This inquiry explores the effectiveness of a class of modern evolutionary algorithms, represented by Non-dominated Sorting Genetic Algorithm (NSGA) components, for solving optimisation tasks with many conflicting objectives. Optimiser behaviour is assessed for a grid of mutation and recombination operator configurations. Performance maps are obtained for the dual aims of proximity to, and distribution across, the optimal trade-off surface. Performance sweet-spots for both variation operators are observed to contract as the number of objectives is increased. Classical settings for recombination are shown to be suitable for small numbers of objectives but correspond to very poor performance for higher numbers of objectives, even when large population sizes are used. Explanations for this behaviour are offered via the concepts of dominance resistance and active diversity promotion

Parton Distributions in the Valon Model

The parton distribution functions determined by CTEQ at low $Q^2$ are used as inputs to test the validity of the valon model. The valon distributions in a nucleon are first found to be nearly $Q$ independent. The parton distribution in a valon are shown to be consistent with being universal, independent of the valon type. The momentum fractions of the partons in the valon add up separately to one. These properties affirm the validity of the valon model. The various distributions are parameterized for convenient application of the model.Comment: 9 pages + 9 figures in ep

Natural resource base of the Fairbanks North Star Borough

This report on the natural resource base of the Fairbanks North Star Borough is one of several continuing research projects related to community planning in Alaska. It represents an interdisciplinary effort of the Mineral Industry Research Laboratory and the Institute of Social, Economic and Government Research at the University of Alaska. The result is a synthesis of the economic development potential of natural resources in the greater Fairbanks region

Phosphorylation of phosphoenolpyruvate carboxykinase in plants. Studies in plants with C4 photosynthesis and Crassulacean acid metabolism and in germinating seeds

We have previously shown that phosphoenolpyruvate carboxykinase (PEPCK) is phosphorylated in vivo in the cotyledons of darkened cucumber seedlings and that phosphorylation is reversed by light [Walker and Leegood (1995) FEBS Lett. 362, 70–74]. In this study the molecular mass of PEPCK was estimated in a range of gluconeogenic seedlings and in leaves of C4 plants and plants with Crassulacean acid metabolism (CAM). Phosphorylation of PEPCK was studied in these plants by feeding tissues with [32P]Pi and assessing phosphorylation by SDS/PAGE and autoradiography of either total proteins or of immunoprecipitated protein. In gluconeogenic seedlings and most CAM plants PEPCK had a molecular mass of 74 kDa, whereas in C4 grasses the molecular mass of PEPCK was always smaller and varied from 67–71 kDa. In all gluconeogenic seedlings and leaves of CAM plants PEPCK was phosphorylated, but it was not phosphorylated in all species of C4 grasses studied. In CAM plants, phosphorylation of PEPCK occurred at night and dephosphorylation occurred during the day. In C4 grasses phosphorylation occurred when leaves were darkened and the enzyme was dephosphorylated following illumination, but it was only phosphorylated in those plants with larger (71 kDa) molecular mass forms of PEPCK

High-temperature chemical processing on asteroids: An oxygen isotope perspective

From the introduction: Small planetary bodies accreted within 2.4 Myr of solar system formation [1]. The primitive materials (CAIs, chondrules, matrix) incorporated into these asteroids were altered by a variety of secondary processes, including aqueous alteration, shock metamorphism, thermal metamorphism and melting. Here we look primarily at the role played by thermal metamorphism and melting in altering the oxygen isotope systematics of asteroidal materials

A study of pattern recovery in recurrent correlation associative memories

In this paper, we analyze the recurrent correlation associative memory (RCAM) model of Chiueh and Goodman. This is an associative memory in which stored binary memory patterns are recalled via an iterative update rule. The update of the individual pattern-bits is controlled by an excitation function, which takes as its arguement the inner product between the stored memory patterns and the input patterns. Our contribution is to analyze the dynamics of pattern recall when the input patterns are corrupted by noise of a relatively unrestricted class. We make three contributions. First, we show how to identify the excitation function which maximizes the separation (the Fisher discriminant) between the uncorrupted realization of the noisy input pattern and the remaining patterns residing in the memory. Moreover, we show that the excitation function which gives maximum separation is exponential when the input bit-errors follow a binomial distribution. Our second contribution is to develop an expression for the expectation value of bit-error probability on the input pattern after one iteration. We show how to identify the excitation function which minimizes the bit-error probability. However, there is no closed-form solution and the excitation function must be recovered numerically. The relationship between the excitation functions which result from the two different approaches is examined for a binomial distribution of bit-errors. The final contribution is to develop a semiempirical approach to the modeling of the dynamics of the RCAM. This provides us with a numerical means of predicting the recall error rate of the memory. It also allows us to develop an expression for the storage capacity for a given recall error rate

THE IRISH ITINERANTS: SOME DEMOGRAPHIC, ECONOMIC AND EDUCATIONAL ASPECTS. BROADSHEET No. 18, May 1979

SOME selected characteristics of Irish itinerants are discussed in this paper. An account is given of some of the problems faced by itinerants based on factual material obtained from Irish official publications, books and articles on Irish itinerants, discussions with people who work with itinerants and the findings of unpublished censuses of itinerants taken by Local Authorities. The study does not involve social or psychological analysis but tries by the presentation of facts assembled together to "help, if in a small way, those who are trying to improve the lot of itinerants". The problem of itinerancy is seen by the authors as part of the problem of poverty. Itinerants are or were, on the whole, the dispossessed--poor, homeless, illiterate, despised." Some, particularly the roadside traders (whom many would not regard as itinerants), are reasonably well off but the great majority according to Patricia McCarthy (1975) were regarded as "marginal people in every sense . . . living a primitive and harsh existence." They are conscious of their poverty, avoid integration with the settled community, and have a low self esteem because of their dependence on charity and social welfare