122,367 research outputs found
Does depleted mantle form an intrinsic part of the Iceland plume?
No full textIcelandic basalt ranges in composition from voluminous tholeiite, erupted in the rift zones, to small-volume, mildly alkaline basalt erupted off-axis. In addition, small-volume flows of primitive basalt, highly depleted in incompatible elements, are sometimes found in the actively spreading rift axes. Relative incompatible-element depletion or enrichment in Icelandic basalt is correlated with variation in radiogenic isotope ratios, implying that the mantle beneath Iceland is heterogeneous and that the relative contribution of the various mantle components relates to eruption environment (on- or off-axis) and hence to degree of melting. Thus small-degree off-axis melting preferentially samples an enriched and more fusible mantle component, whereas more extensive melting beneath the rift axes produces magma that more closely represents the bulk Iceland plume mantle composition. The small-volume flows of depleted basalt represent melts that have preferentially sampled a depleted and more refractory mantle component. A debate has arisen over the nature of the depleted component in the Iceland plume. Some authors [e.g., Hanan and Schilling, 1997] argue that the depleted component is ambient upper mantle, the source of normal mid-ocean ridge basalt (NMORB) in this region. Others [e.g., Thirlwall, 1995; Kerr et al., 1995; Fitton et al., 1997], however, have used various lines of evidence to suggest that the plume contains an intrinsic depleted component that is distinct from the NMORB source. Hanan et al. [2000] attempt to refute the existence of a depleted Iceland plume (DIP) component through a critical evaluation of the Nb-Zr-Y arguments advanced by Fitton et al. [1997] and the Hf-Nd-isotopic evidence presented by Kempton et al. [1998]. In this paper we examine the case presented by Hanan et al. [2000] and conclude that their arguments are flawed. Firstly, their trace-element data set excludes data from depleted Icelandic basalt samples and so it is not surprising that they find no evidence for a DIP component. Secondly, they present two new Hf-isotope analyses of a single depleted Icelandic basalt sample and show that the data plot in their NMORB field on an εHf versus εNd diagram. However, new data allow the resolution of distinct NMORB and depleted Icelandic basalt fields on this diagram. We conclude that trace-element and radiogenic isotope data from Iceland require the existence of a DIP component
Fredegunda Fitton, Shaw & Gauld 1988
No full textGenus <i>Fredegunda</i> Fitton, Shaw & Gauld, 1988 <p> <i>Fredegunda</i> Fitton, Shaw & Gauld, 1988, 7: 45. Type species: <i>Pimpla diluta</i> Ratzeburg, 1852.</p> <p> <b>Diagnosis.</b> Mandible with two apical teeth. Clypeus with apical margin centrally notched, bilobed. Eyes large and bare. Occipital carina complete and median dorsally dipped downward. Antenna filiform with 23 antennomeres. Epomia distinct. Notaulus shallow and short, present on anterior 0.3. Prepectal carina strong. Propodeum with median longitudinal carinae long and well developed. Submetapleural carina complete. Fore wing with 3rs-m, cu-a opposite Rs & M. Areolet receiving 2m-cu near apex. Hind wing with Cu & cu-a intercepted below the middle, distal abscissa of Cu present. Apical segment of tarsi swollen, female tarsal claw with a tooth-like basal lobe. Metasoma stout; first tergite of male strongly narrowed behind the spiracle; second tergite without oblique grooves cutting off depressed triangular areas anterolaterally. Ovipositor compressed, its apex with lower valve enlarged and partially enclosed the upper valve.</p> <p> <b>Biology.</b> Parasitoids of <i>Archanara dissoluta</i> (Treitschke), <i>A. geminipuncta</i> (Haworth), <i>Arenostola semicana</i> (Esper), <i>Chilodes maritima</i> (Tauscher) and <i>Rhizedra lutosa</i> (Hübner) (Lepidoptera: Noctuidae) (Aubert 1969; Fulmek 1968; Fitton <i>et al.</i> 1988).</p> <p> <b>Distribution.</b> Palearctic and Oriental regions.</p> <p> <b>Comments.</b> This genus was recognized by Fitton <i>et al.</i> (1988) mainly based on lower valve of apex of ovipositor enlarged and the upper valve partially enclosed. It can be easily distinguished from <i>Endromopoda</i> Hellén and <i>Scambus</i> Hartig by these ovipositor characters.</p>Published as part of <i>Liu, Jing-Xian, He, Jun-Hua & Chen, Xue-Xin, 2013, The discovery of genus Fredegunda Fitton, Shaw & Gauld in China, with description of a new species (Hymenoptera, Ichneumonidae, Pimplinae), pp. 79-83 in Zootaxa 3637 (1)</i> on pages 79-80, DOI: 10.11646/zootaxa.3637.1.9, <a href="http://zenodo.org/record/283605">http://zenodo.org/record/283605</a>
Constructing the Cool Wall: A tool to explore teen meanings of cool
No full textThis paper describes the development and exploration of a tool designed to assist in investigating ‘cool’ as it applies to the design of interactive products for teenagers. The method involved the derivation of theoretical understandings of cool from literature that resulted in identification of seven core categories for cool, which were mapped to a hierarchy. The hierarchy includes having of cool things, the doing of cool activities and the being of cool. This paper focuses on a tool, the Cool Wall, developed to explore one specific facet of the hierarchy; exploring shared understanding of having cool things. The paper describes the development and construction of the tool, using a heavily participatory approach, and the results and analysis of three studies. The first study was carried out over 2 days in a school in the UK. The results of the study both provide clear insights into cool things and enable a refined understanding of cool in this context. Two additional studies are then used to identify potential shortcomings in the Cool Wall methodology. In the second study participants were able to populate a paper cool wall with anything they chose, this revealed two potential new categories of images and that the current set of images covered the majority of key themes. In the third study teenagers interpretations of the meaning of the images included in the Cool Wall were explored, this showed that the majority of meanings were as expected and a small number of unexpected interpretations provided some valuable insights
Promethes bridgmani Fitton
No full textPromethes bridgmani Fitton Promethes persulcatus Nakanishi, 1986 is a junior synonym, syn. nov. Russia, Kuril islands: Paramushir Island, inland of Rifovaya Bay; N 50 ° 29.84 ' / E 156 °05.80', 30. VII. 1999, leg. B.K. Urbain. 1 ♂. The type of Promethes persulcator Nakanishi could not be obtained, but based on the detailed description (Nakanishi, 1986) and on this male from the Kuril islands, these two species are clearly synonymous. While P. bridgmani has only been reported from Europe, P. persulcator has been recorded in Japan and the Russian Far East. Palaearctic, including Japan and the Russian Far East.Published as part of Klopfstein, Seraina, 2014, Review of the Diplazontinae (Hymenoptera, Ichneumonidae) of the Kuril islands, with descriptions of two new species in Zootaxa 3779 (1), DOI: 10.11646/zootaxa.3779.1.5, http://zenodo.org/record/23079
A joint geochemical–geophysical record of time-dependent mantle convection south of Iceland
No full textThe North Atlantic V-Shaped Ridges (VSRs) provide a spatially extensive and clear record of unsteady mantle convective circulation over >40 My>40 My. VSRs are diachronous ridges of thick crust formed with a periodicity of ∼5 My∼5 My along the Mid Atlantic Ridge, south of Iceland. We present data from a set of dredged basalt samples that shows chemical variation associated with two complete VSR crustal thickness cycles where they intersect the Mid Atlantic Ridge. The new dataset also records chemical variation associated with a VSR crustal thickness cycle along a plate spreading flow-line. Inverse correlations between crustal thickness and both incompatible trace element concentrations and incompatible element ratios such as Nb/Y and La/Sm are observed. Geochemical and crustal thickness observations can be matched using a time-dependent mid-ocean ridge melting model with a basal boundary condition of sinusoidally varying potential temperature. Our observations and models suggest that VSRs are generated when hot patches are carried up the plume stem beneath SE Iceland and spread radially outward within the asthenosphere. These patches are then drawn upward into the melting region when passing beneath the Mid Atlantic Ridge. The geometry of the VSRs and the size of the dynamically supported swell suggest that the Iceland Plume is the strongest plume in the Earth at present, with a volume flux of View the MathML source49±14 km3yr−1
Pristomerus bullis Fitton in Polaszek 1994
No full textPristomerus bullis Fitton in Polaszek et al., 1994 Fig. 6 Pristomerus bullis Fitton in Polaszek et al., 1994: 83. Diagnosis Moderately sized; yellow to orange overall with base of tergite 2 infuscate, frons darker than face, and notaulus and scutellum lighter than remainder of mesonotum; face densely punctate; inner eye margins parallel; clypeus very strongly transverse, sparsely punctate with inter-punctures space smooth; malar line short; frons and vertex punctate-granulate, gena and temple coriaceous; occipital carina joining hypostomal carina shortly above mandible base; antenna with 26–32 flagellomeres, penultimate flagellomere shorter than wide; mesosoma strongly elongate, mostly very densely punctate but dorsal half of pronotum and ventral half of speculum smooth; propodeum with area superomedia narrow and elongate; hind femur rather stout; femoral tooth stout, about half as high as basally wide, followed by minute denticles; ovipositor rather short, apically moderately sinuous. B 7.3–8.3; A 3.5–4.0; F 4.0–4.7; CT 2.2–2.5; ML 0.3; POL 1.0; OOL 1.3; Fl n–1 0.7; ASM 2.8; OT 1.3; FFT 1. Male with inner margins of eyes diverging ventrally, ocelli, hind femur and femoral tooth enlarged, and mesoscutum strongly smoother; otherwise similar to female. POL 0.5; OOL 0.4. Differential diagnosis Moderately sized and yellow to orange overall; differentiated from most other Afrotropical species by the very transverse clypeus. It is thus apparently closely related to P. babinga sp. nov. but P. bullis has a significantly shorter ovipositor. Material examined Holotype TANZANIA: ♀, “ TANZANIA: Morogoro region, Mkindo. G. Bianchi, i.1991 /5, 5.8, ex Maliarpha seperatella [sic] in Rice, B.M. Type Hym 3B.2473” (BMNH). Other material UGANDA: 1 ♀, “Uganda, Kibale National Park, Kanyawara, Makerere University Biological Field Station, 1465 m, 0°35.442’N 30°21.741’E, 10.viii.2008, S. van Noort, UG 08–KF12–S03, Sweep, primary mid-altitude rainforest, near stream, SAM–HYM–P047402” (SAMC). ZAMBIA: 1 ♂, “Zambia, nr Mfuwe sweeping on the dried egg tree 09.XII.2011 Gumovsky; Mopane tree [Colophospermum mopane, Fabaceae] SAM–HYM–P049439” (SAMC). Host records Maliarpha separatella Ragonot, 1888 (Lepidoptera: Pyralidae). Distribution Tanzania. New records: Uganda, Zambia.Published as part of Rousse, Pascal & Noort, Simon van, 2015, Revision of the Afrotropical species of Pristomerus (Ichneumonidae: Cremastinae), with descriptions of 31 new species, pp. 1-129 in European Journal of Taxonomy 124 on pages 39-41, DOI: 10.5852/ejt.2015.124, http://zenodo.org/record/378021
The Iceland plume in space and time: a Sr-Nd-Pb-Hf study of the North Atlantic rifted margin
No full textNew Sr–Nd–Pb–Hf data require the existence of at least four mantle components in the genesis of basalts from the North Atlantic Igneous Province (NAIP): (1) one (or more likely a small range of) enriched component(s) within the Iceland plume, (2) a depleted component within the Iceland plume (distinct from the shallow N-MORB source), (3) a depleted sheath surrounding the plume and (4) shallow N-MORB source mantle. These components have been available since the major phase of igneous activity associated with plume head impact during Paleogene times. In Hf–Nd isotope space, samples from Iceland, DSDP Leg 49 (Sites 407, 408 and 409), ODP Legs 152 and 163 (southeast Greenland margin), the Reykjanes Ridge, Kolbeinsey Ridge and DSDP Leg 38 (Site 348) define fields that are oblique to the main ocean island basalt array and extend toward a component with higher 176Hf/177Hf than the N-MORB source available prior to arrival of the plume, as indicated by the compositions of Cretaceous basalts from Goban Spur (~95 Ma). Aside from Goban Spur, only basalts from Hatton Bank on the oceanward side of the Rockall Plateau (DSDP Leg 81) lie consistently within the field of N-MORB, which indicates that the compositional influence of the plume did not reach this far south and east ~55 Ma ago. Thus, Hf–Nd isotope systematics are consistent with previous studies which indicate that shallow MORB-source mantle does not represent the depleted component within the Iceland plume [Thirlwall, J. Geol. Soc. London 152 (1995) 991–996; Hards et al., J. Geol. Soc. London 152 (1995) 1003–1009; Fitton et al., Earth Planet. Sci. Lett. 153 (1997) 197–208]. They also indicate that the depleted component is a long-lived and intrinsic feature of the Iceland plume, generated during an ancient melting event in which a mineral (such as garnet) with a high Lu/Hf was a residual phase. Collectively, these data suggest a model for the Iceland plume in which a heterogeneous core, derived from the lower mantle, consists of ‘enriched’ streaks or blobs dispersed in a more depleted matrix. A distinguishing feature of both the enriched and depleted components is high Nb/Y for a given Zr/Y (i.e. positive ΔNb), but the enriched component has higher Sr and Pb isotope ratios, combined with lower εNd and εHf. This heterogeneous core is surrounded by a sheath of depleted material, similar to the depleted component of the Iceland plume in its εNd and εHf, but with lower 87Sr/86Sr, 208Pb/204Pb and negative ΔNb; this material was probably entrained from near the 670 km discontinuity when the plume stalled at the boundary between the upper and lower mantle. The plume sheath displaced more normal MORB asthenosphere (distinguished by its lower Hf for a given Nd or Zr/Nb ratio), which existed in the North Atlantic prior to plume impact. Preliminary data on MORBs from near the Azores plume suggest that much of the North Atlantic may be ‘polluted’ not only by enriched plume material but also by depleted material similar to the Iceland plume sheath. If this hypothesis is correct, it may provide a general explanation for some of the compositional diversity and variations in inferred depth of melting [Klein and Langmuir, J. Geophys. Res. 92 (1987) 8089–8115] along the MAR in the North Atlantic
Quantifying relationships between basalt geochemistry, shear wave velocity and asthenospheric temperature beneath western North America.
No full textWestern North America has an average elevation that is ∼2 km higher than cratonic North America. This difference coincides with a westward decrease in average lithospheric thickness from ∼240 to 260 basaltic samples. Forward and inverse modeling of carefully selected major, trace, and rare earth elements were used to determine melt fraction as a function of depth. Basaltic melt appears to have been generated by adiabatic decompression of dry peridotite with asthenospheric potential temperatures of 1340 ± 20 °C. Potential temperatures as high as 1365 °C were obtained for the Snake River Plain. For the youngest (i.e., <5 Ma) basalts with a subplate geochemical signature, there is a positive correlation between shear wave velocities and trace element ratios such as La/Yb. The significance of this correlation is explored by converting shear wave velocity into temperature using a global empirical parameterization. Calculated temperatures agree with those determined by inverse modeling of rare earth elements. We propose that regional epeirogenic uplift of western North America is principally maintained by widespread asthenospheric temperature anomalies lying beneath a lithospheric plate, which is considerably thinner than it was in Late Cretaceous times. Our proposal accounts for the distribution and composition of basaltic magmatism and is consistent with regional heat flow anomalies
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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