1,622 research outputs found
Regional geochemical and geophysical surveys in the Berwyn Dome and adjacent areas, north Wales
This report describes stream sediment and gravity
surveys carried out across the Berwyn Dome and adjacent
areas. The gravity survey confirmed the presence of a
broad regional Bouguer anomaly low in the central part of
the Dome, on which is superimposed several smaller irregular
highs and lows. Some of these local anomalies
possibly reflect small igneous bodies but more detailed
gravity surveys would be needed to determine their form.
Near Corwen the Bryneglwys Fault coincides with a 4.5
mGa1 anomaly but southwards the two features diverge,
suggesting that the density interface is related either to a
splay fault or to the eastern margin of the Lower
Palaeozoic Montgomery trough. Some other structural
trends are weakly reflected on the Bouguer anomaly and
aeromagnetic maps, but there is no clear correlation with
known base metal mineralisation. The Bouguer
anomalies cannot be attributed to particular structures
with any certainty but are probably due to a number of
factors, including variation in the Precambrian basement
and changes in the lithology and thickness of Lower
Palaeozoic sedimentary rocks. There is no evidence for a
large granitic body in Lower Palaeozoic rocks underlying
the mineralisation at Llangynog. The aeromagnetic map
suggests the presence of a magnetic basement at a depth
of 3-4 km centred beneath the northwestern margin of
the Dome.
The stream sediment survey involved the collection of a
- 100 mesh stream sediment, panned concentrate and
water sample from each of the 399 sites sampled. The
sample density was 1 site per 1.5 km*. Cu, Pb, Zn, Ba,
Fe, Mn, Co, V, Cr, Ni, Zr, MO and Sn were determined
in the stream sediments, Cu, Pb, Zn, Ba, Fe, Mn, Ce,
Sn, Sb, Ti, Ni and As in the panned concentrates and Cu,
Pb and Zn in stream waters. Major variations in the
results are related to (i) hydrous oxide precipitation processes,
(ii) contamination from human activities, (iii) base
metal and baryte mineralisation, (iv) monazite concentrations
in panned concentrates, (v) hitherto unrecorded
gold mineralisation and (vi) lithological variations. The
latter were related principally to shale-sandstone variation,
but groups of elements attributable to the presence
of basic intrusions, phosphatic rocks, coal measures,
sandstones, limestones and volcanics were also discerned.
Threshold levels were established from cumulative frequency
curve analysis, and some anomalous sites were examined
in the field. Anomalies did not form prominent
coherent groups and were generally weak and scattered,
with a wide variety of element groupings reflecting a
range of causes. Many anomalous panned concentrates
were examined mineralogically to try to . determine
whether anomalies were related to chemically extreme
background lithologies, contamination, or mineralisation.
All the anomalies were related to one or more of the
major causes of variation, although because of the very
limited amount of follow-up work carried out the precise
cause of many anomalies remains uncertain. No anomaly
is considered to represent a strong prospect but several
deserve further limited investigation, notably those
associated with (i) gold mineralisation in the northwest of
the area, (ii) baryte, perhaps accompanied by base metal
’ mineralisation, associated with Caradocian volcanics and
phosphatic rocks at several localities, (iii) mineralisation
associated with Llandeilian limestones and volcanic rocks
north of Llanrhaeadr, and (iv) copper mineralisation
associated with intrusives near the eastern margin of the
Dome, where survey data is most incomplete
Exploration for volcanogenic sulphide mineralisation at Benglog, north Wales
Exploration for volcanogenic sulphide mineralisation
around Benglog is one of three investigations
designed to assess the metallogenic potential
of the Ordovician Aran Volcanic Group.
Detailed geological mapping in the Benglog
area enabled an interpretation of the volcanic
environment, critical to such an assessment, to be
made. The eruptive rocks are acid and basic in
composition; the acid rocks are mostly ash-flow
tuffs derived from outside the area, whereas the
basic rocks have a local derivation. They are all
interbedded with dark grey or black silty mudstone
and were probably erupted in a submarine
environment. Contemporaneous dolerite sills were
intruded into wet sediment.
This environment was suitable for volcanogenic
exhalative sulphide deposits to form and indications
of a metallogenic horizon were found at the top
of the Y Fron Formation in the form of abundant
pyrite, minor pyrrhotite and minor base metal
enrichment.
Soil samples, analysed for copper, lead and
zinc, were collected and geophysical surveys were
carried out along eleven east-west trending traverse
lines 300 m apart across the volcanic succession.
Indications were found of minor vein mineralisation
at dolerite intrusion margins and locally along
faults. Very high chargeability and low resistivity
anomalies over mudstones did not spatially
coincide with geochemical anomalies in soil, but
the secondary redistribution of metals in soils and
variable thickness of overburden precluded
confident interpretation of the source of many
soil anomalies. Geochemical drainage data, in
conjunction with rock analyses, show strong
barium enrichment in mudstones which could be
volcanogenic in origin but related to two separate
eruptive episodes.
The findings of the survey were inconclusive.
An environment suitable for the formation of
volcanogenic exhalative sulphide deposits was
established, but the geochemical and geophysical
surveys located only minor vein mineralisation and
tenuous indications of other styles of mineralisation.
Recommendations are made for further work
Cocaine self-administration in the mouse: A low- cost, chronic catheter preparation
Intravenous drug self-administration is the most valid animal model of human addiction because it allows volitional titration of the drug in the blood based on an individual’s motivational state together with the pharmacokinetic properties of the drug. Here we describe a reliable low-cost mouse self-administration catheter assembly and protocol that that can be used to assess a variety of drugs of abuse with a variety of protocols. We describe a method for intravenous catheter fabrication that allows for efficient and long-lasting intravenous drug delivery. The intravenous catheters remained intact and patent for several weeks allowing us to establish stable maintenance of cocaine acquisition. This was followed by a dose response study in the same mice. For collaborators interested in premade catheters for research please make a request at www.neuro-cloud.net/nature-precedings/pomerenze
Mineral exploration in the Cockermouth area, Cumbria. Part 2: follow-up surveys
This report describes the results of geochemical, geological and geophysical surveys across three
small areas of Carboniferous and Lower Palaeozoic rocks along the northern margin of the English
Lake District. The areas were chosen from the appraisal of regional-scale survey data described by
Cooper et al. (1991). In two of the areas, Ruthwaite and Tallentire, the objective was to provide
more information on the extent and magnitude of fracture-controlled epigenetic baryte and base
metal mineralisation. In the third area, at Whitrigg, brief surveys were carried out to aid the
interpretation of unexplained geochemical and geophysical anomalies found during two projects
carried out under the Mineral Exploration and Investment Grants Act (MEIGA).
At Ruthwaite, where a mine formerly worked baryte from a fault separating Lower Palaeozoic and
Carboniferous rocks, surface indications of further baryte mineralisation were found. Soil analyses
indicated that mineralisation may be present along the continuation of the faultline worked at
Ruthwaite and in the Eycott Volcanic Group rocks to the south of it. In this area relatively small,
but in some circumstances perhaps economically attractive, deposits of baryte may be present
under drift cover.
In the Tallentire Hill area, geological mapping followed by traverse-based soil sampling showed
that fracture-controlled mineralisation is widespread in the Carboniferous (Dinantian and
Namurian) rocks. The fracture fillings consist dominantly of baryte, often accompanied by
carbonate, with traces of copper and mercury. Where seen at surface the fracture fillings are too
small, patchy and low-grade to be of any economic importance. Baryte mineralisation also occurs
locally as patchy impregnations in sandstones. These are considered to be epigenetic deposits
related to the fracture-controlled mineralisation. Trial geophysical surveys suggested that electrical
methods may be useful in determining the extent of the mineralised sandstone. There is a
possibility that more extensive baryte deposits may be present in the limestone succession
underlying the mineralised sandstones.
In the Whitrigg area, Carboniferous rocks are separated from Lower Palaeozoic rocks of the
Eycott Volcanic Group by the easterly-trending Boundary Fault and north-westerly-trending
Bothel Fault. Evidence from an old mineral working and the results of a soil survey indicate that
patchy, epigenetic, fracture-controlled baryte and base metal mineralisation occurs along the
Bothel Fault and, locally, in the adjacent rocks. A feature of this mineralisation is the presence of
mercury, which is most abundant in a sample of brecciated and altered rock from the Eycott
Volcanic Group. Prominent base metal in soil anomalies discovered by MEIGA-funded projects
near Stangerhill are not associated with barium anomalies. It was concluded that these soil
anomalies are most likely to be caused by secondary concentration in overburden, and that the
source of metals may be a sub-cropping metalliferous horizon within the Carboniferous succession
or, more probably, fracture-controlled mineralisation.
Trial geophysical surveys carried out in all three areas indicated that in ground free of artificial
sources the VLF(EM) and conductivity mapping methods could be useful for tracing faults beneath
drift and providing information on drift thickness. Closely-spaced soil sampling proved effective for
detecting mineralisation in areas where the drift cover is thin, and a trial soil-gas survey showed
that this technique could also be useful for tracing faults beneath drift
Disordered Hubbard Model with Attraction: Coupling Energy of Cooper Pairs in Small Clusters
We generalize the Cooper problem to the case of many interacting particles in
the vicinity of the Fermi level in the presence of disorder. On the basis of
this approach we study numerically the variation of the pair coupling energy in
small clusters as a function of disorder. We show that the Cooper pair energy
is strongly enhanced by disorder, which at the same time leads to the
localization of pairs.Comment: revtex, 5 pages, 6 figure
Haplotyping the human leukocyte antigen system from single chromosomes
We describe a method for determining the parental HLA haplotypes of a single individual without recourse to conventional segregation genetics. Blood samples were cultured to identify and sort chromosome 6 by bivariate flow cytometry. Single chromosome 6 amplification products were confirmed with a single nucleotide polymorphism (SNP) array and verified by deep sequencing to enable assignment of both alleles at the HLA loci, defining the two haplotypes. This study exemplifies a rapid and efficient method of haplotyping that can be applied to any chromosome pair, or indeed all chromosome pairs, using a single sorting operation. The method represents a cost-effective approach to complete phasing of SNPs, which will facilitate a deeper understanding of the links between SNPs, gene regulation and protein function
Onset of magnetism in B2 transition metals aluminides
Ab initio calculation results for the electronic structure of disordered bcc
Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6)
alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl,
NiAl) phases with point defects are presented. The calculations were performed
using the coherent potential approximation within the Korringa-Kohn-Rostoker
method (KKR-CPA) for the disordered case and the tight-binding linear
muffin-tin orbital (TB-LMTO) method for the intermetallic compounds. We studied
in particular the onset of magnetism in Fe-Al and Co-Al systems as a function
of the defect structure. We found the appearance of large local magnetic
moments associated with the transition metal (TM) antisite defect in FeAl and
CoAl compounds, in agreement with the experimental findings. Moreover, we found
that any vacancies on both sublattices enhance the magnetic moments via
reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are
ferromagnetically ordered for the whole range of composition studied, whereas
Co-Al becomes magnetic only for Co concentration >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in
Phys.Rev.
A platform for curated products from novel Open Reading Frames (nORFs) prompts reinterpretation of disease variants
Recent evidence from proteomics and deep massively parallel sequencing studies have revealed that eukaryotic genomes contain substantial numbers of as-yet-uncharacterized open reading frames (ORFs). We define these uncharacterized ORFs as novel ORFs (nORFs). nORFs in humans are mostly under 100 codons and are found in diverse regions of the genome, including in long noncoding RNAs, pseudogenes, 3′ UTRs, 5′ UTRs, and alternative reading frames of canonical protein coding exons. There is therefore a pressing need to evaluate the potential functional importance of these unannotated transcripts and proteins in biological pathways and human disease on a larger scale, rather than one at a time. In this study, we outline the creation of a valuable nORFs data set with experimental evidence of translation for the community, use measures of heritability and selection that reveal signals for functional importance, and show the potential implications for functional interpretation of genetic variants in nORFs. Our results indicate that some variants that were previously classified as being benign or of uncertain significance may have to be reinterpreted
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