1,843 research outputs found
A Stratabound Zinc-Lead Deposit in Meguma Group Metasediments at Eastville, Nova Scotia
The Eastville zinc-lead deposit, discovered by soil sampling in 1976, occurs near the contact of the Goldenvllle and Halifax Formations, the two divisions of the Cambro-Ordovician Meguma Group. The stratigraphic succession in the contact zone comprises an assemblage of quartz metawacke, calcareous quartz metawacke and slate. Quartz metawacke is predominant in the Goldenvllle Formation and slate is the dominant lithology in the overlying Halifax Formation. These rocks are interpreted as the middle to outer fan and basin plain deposits of a submarine fan complex. Pyrrhotite and pyrite, the predominant Bulphide minerals in all lithologles in the contact zone, were deposited by reduction of iron in the sediments, independent of the mineralizing process.
Sphalerite and galena occur in rocks over a 10 km strike length in elongate blebs, 2 to 5 mm long, distributed parallel to bedding and in cross-cutting fractures. The deposit is stratabound and generally occurs in black slate beds near the Goldenvllle-Halifax contact. Geochemical analyses of the rocks have indicated a concentration of Mn in the calcareous quartzite member, the upper unit of the Goldenville Formation. A relationship between the Mn enrichment and the abundance of sphalerite and galena in the section has not been established. The sulphide mineralogy, laterally continuous stratigraphy and lack of metal zonation and underlying feeder structures indicate the sphalerite and galena were syngenetically deposited from metal-rich brines at a site distant from where the brines entered the basin of deposition-
RÉSUMÉ
Le dépôt de plomb at de zinc de Eastville, qui a été découvert par des prises d'échantillons de terre en 1976, est situé pré du contact des formations Goldenville et Halifax (les deux unités du groupe Meguma). La succession stratigraphique dans la zone de contact est constitué d'un assemblage de métagrauwacke de quartz, de métagrauvacke calcaire de quartz, et d'ardoise. Le métagrauwacke de quartz est prédominant dans la formation Goldenville et l'ardoise est la lithologie dominate de la formation de Halifax, qui est superposé sur la première. Ces roches sont expllquées comme étant le cône central ou extérieur et des dépôts de la plaine d'un basin d'un compiexe de cône. La pyrrhotite et la pyrite, les minéraux sulfides principalis dans toutes les lithologles de la zone de contact, ont été déposés par une réduction de fer dans les sédiments, indépendement des processus de minéralisation.
La sphalérite et la galène se trouvent dans les roches sur une longueur de 10 kilomètres le long de la couche en temps que soufflures de 2 à 5 mm de longueur, réparties paralèllement à la couche et dans les fractures à trafers banc. Le dépôt est limite aux strates et se crouve en général dans de l'ardoise noire près du contact Goldenville-Halifax. Des analyses géochimiques des roches ont indiqué une concentration de Mn dans les quartzites calcaires, l'unité la plus é1evé de la formation Goldenville. Un rapport entre l'enrichiasement en Mn et l'abondance de la sphalerite et de la galène dans la section, n'a pas été établie. La minéralogie des sulfides, la stratigraphie laterale continue, et le manque de zonation de métaux et de structures de conduite d'alimentation, indique que la sphalerite et la galène ont été déposées sygénétiquement à partir de saumures riches en métaux dans un site éloigné de l'endroit où les saumures pénétrent le basin de dépôt.
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Turnip mosaic potyvirus probably first spread to Eurasian brassica crops from wild orchids about 1000 years ago
Turnip mosaic potyvirus (TuMV) is probably the most widespread and damaging virus that infects cultivated brassicas worldwide. Previous work has indicated that the virus originated in western Eurasia, with all of its closest relatives being viruses of monocotyledonous plants. Here we report that we have identified a sister lineage of TuMV-like potyviruses (TuMV-OM) from European orchids. The isolates of TuMV-OM form a monophyletic sister lineage to the brassica-infecting TuMVs (TuMV-BIs), and are nested within a clade of monocotyledon-infecting viruses. Extensive host-range tests showed that all of the TuMV-OMs are biologically similar to, but distinct from, TuMV-BIs and do not readily infect brassicas. We conclude that it is more likely that TuMV evolved from a TuMV-OM-like ancestor than the reverse. We did Bayesian coalescent analyses using a combination of novel and published sequence data from four TuMV genes [helper component-proteinase protein (HC-Pro), protein 3(P3), nuclear inclusion b protein (NIb), and coat protein (CP)]. Three genes (HC-Pro, P3, and NIb), but not the CP gene, gave results indicating that the TuMV-BI viruses diverged from TuMV-OMs around 1000 years ago. Only 150 years later, the four lineages of the present global population of TuMV-BIs diverged from one another. These dates are congruent with historical records of the spread of agriculture in Western Europe. From about 1200 years ago, there was a warming of the climate, and agriculture and the human population of the region greatly increased. Farming replaced woodlands, fostering viruses and aphid vectors that could invade the crops, which included several brassica cultivars and weeds. Later, starting 500 years ago, inter-continental maritime trade probably spread the TuMV-BIs to the remainder of the world
Accelerator system for the PRISM based muon to electron conversion experiment
The next generation of lepton flavor violation experiments need high
intensity and high quality muon beams. Production of such beams requires
sending a short, high intensity proton pulse to the pion production target,
capturing pions and collecting the resulting muons in the large acceptance
transport system. The substantial increase of beam quality can be obtained by
applying the RF phase rotation on the muon beam in the dedicated FFAG ring,
which was proposed for the PRISM project.This allows to reduce the momentum
spread of the beam and to purify from the unwanted components like pions or
secondary protons. A PRISM Task Force is addressing the accelerator and
detector issues that need to be solved in order to realize the PRISM
experiment. The parameters of the required proton beam, the principles of the
PRISM experiment and the baseline FFAG design are introduced. The spectrum of
alternative designs for the PRISM FFAG ring are shown. Progress on ring main
systems like injection and RF are presented. The current status of the study
and its future directions are discussed.Comment: Studies performed within the PRISM Task Force initiativ
Genetic variants alter T-bet binding and gene expression in mucosal inflammatory disease
The polarization of CD4+ T cells into distinct T helper cell lineages is essential for protective immunity against infection, but aberrant T cell polarization can cause autoimmunity. The transcription factor T-bet (TBX21) specifies the Th1 lineage and represses alternative T cell fates. Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) that may be causative for autoimmune diseases. The majority of these polymorphisms are located within non-coding distal regulatory elements. It is considered that these genetic variants contribute to disease by altering the binding of regulatory proteins and thus gene expression, but whether these variants alter the binding of lineage-specifying transcription factors has not been determined. Here, we show that SNPs associated with the mucosal inflammatory diseases Crohn’s disease, ulcerative colitis (UC) and celiac disease, but not rheumatoid arthritis or psoriasis, are enriched at T-bet binding sites. Furthermore, we identify disease-associated variants that alter T-bet binding in vitro and in vivo. ChIP-seq for T-bet in individuals heterozygous for the celiac disease-associated SNPs rs1465321 and rs2058622 and the IBD-associated SNPs rs1551398 and rs1551399, reveals decreased binding to the minor disease-associated alleles. Furthermore, we show that rs1465321 is an expression quantitative trait locus (eQTL) for the neighboring gene IL18RAP, with decreased T-bet binding associated with decreased expression of this gene. These results suggest that genetic polymorphisms may predispose individuals to mucosal autoimmune disease through alterations in T-bet binding. Other disease-associated variants may similarly act by modulating the binding of lineage-specifying transcription factors in a tissue-selective and disease-specific manner
Influence of anti-oestrogens on the specific binding in vitro of (3H)oestradiol by cytosol of rat mammary tumours and human breast carcinomata
Laboratory Development
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Measurement of the Atmospheric Muon Charge Ratio at TeV Energies with MINOS
The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray
muon data since the beginning of August, 2003 at a depth of 2070
meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA.
The data with both forward and reversed magnetic field running configurations
were combined to minimize systematic errors in the determination of the
underground muon charge ratio. When averaged, two independent analyses find the
charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.).
Using the map of the Soudan rock overburden, the muon momenta as measured
underground were projected to the corresponding values at the surface in the
energy range 1-7 TeV. Within this range of energies at the surface, the MINOS
data are consistent with the charge ratio being energy independent at the two
standard deviation level. When the MINOS results are compared with measurements
at lower energies, a clear rise in the charge ratio in the energy range 0.3 --
1.0 TeV is apparent. A qualitative model shows that the rise is consistent with
an increasing contribution of kaon decays to the muon charge ratio.Comment: 16 pages, 17 figure
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