131,205 research outputs found
The development of magmatism along the Cameroon Volcanic Line: Evidence from teleseismic receiver functions
No full text[1] The Cameroon Volcanic Line (CVL) in West Africa is a chain of Cenozoic volcanism with no clear age progression. The reasons for its existence are unclear, and the nature of its magmatic plumbing system is poorly understood. Specifically, whether or not the CVL crust presently contains melt and/or mafic intrusions, as is often observed at hot spots and rifts elsewhere, is presently unknown. To address this issue, we present a receiver function study of crustal structure using earthquakes recorded by the Cameroon Broadband Seismic Experiment. In regions of the CVL unaffected by Cretaceous extension associated with the breakup of Gondwana (e.g., the Garoua rift), Vp/Vs ratios are markedly low (network average ?1.74) compared to hot spots elsewhere, providing no evidence for either melt or cooled mafic crustal intrusions due to CVL magmatism. The character of P-to-S conversions from beneath the CVL also indicates that lower-crustal intrusions (often termed underplate) are not present beneath the region. Our observations thus corroborate earlier petrological studies that show CVL alkaline magmas fractionate in the mantle, not the crust, prior to eruption. Hypotheses for the formation of the CVL should not include markedly elevated upper-mantle potential temperatures, or large volumes of partial melt, both of which can explain observations at hot spots and rifts worldwide. The protracted, yet sporadic, development of small-volume alkali melts beneath the CVL may instead be explained better by lower melt volume mechanisms such as shear zone reactivation or lithospheric delamination
Tabor (James D.) Gallacher (Eugène V.), Why Waco? Cults and the Battle for Religious Freedom in America
No full textTabor (James D.) Gallacher (Eugène V.), Why Waco? Cults and the Battle for Religious Freedom in America. In: Archives de sciences sociales des religions, n°100, 1997. pp. 131-132
Tabor (James D.) Gallacher (Eugène V.), Why Waco? Cults and the Battle for Religious Freedom in America
No full textTabor (James D.) Gallacher (Eugène V.), Why Waco? Cults and the Battle for Religious Freedom in America. In: Archives de sciences sociales des religions, n°100, 1997. pp. 131-132
Themes constructed during thematic analysis mapped to four domains of treatment burden, adapted from Gallacher et al., 2013.
No full textThemes constructed during thematic analysis mapped to four domains of treatment burden, adapted from Gallacher et al., 2013.</p
Direct Band-gap Electroluminescence from Strained n-Ge Light Emmitting Diodes
No full textThe fabrication and characterisation of light emitting diode (LED) structures made of Ge grown on Si substrates is reported. The structures are circular mesa of strained n-Ge etched down to an undoped buffer of Ge. The electroluminescence exhibit average power levels at 1.7 μm of a few μW, many orders of magnitude larger than the nW previously reported. Three individual mechanisms of emission are identified which can be used to interpret the results encountered in other publications. This work potentially opens the route for integrated source of light and photodetectors above 1.6 μm on Si with applications for lab-on-a-chip and healthcare
MeSH term explosion and author rank improve expert recommendations
Get PDFInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Long wavelength >1.9 Î1⁄4m Germanium for optoelectronics using process induced strain
No full textThe photoluminescence of tensile strained germanium nanostructures is reported. Sub-micron gratings and pillars were fabricated before being embedded in strained silicon nitride films. Using different deposition conditions and different sizes of structures, the stress in the nanostructures can be controlled. The measured optical properties of the samples show that the direct band-gap is shifted drastically towards higher wavelength to over 1.9 Î1⁄4m wavelength. This process of local control of the stress in germanium nanostructures is compatible with integrated photonic devices in waveguides geometry. This work opens the route towards emitters and photo-detectors above 1.6 Î1⁄4m wavelength integrated on silicon substrates which are not presently available. © The Electrochemical Society
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
Get PDFBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Ohmic contacts to n-type germanium with low specific contact resistivity
Get PDFA low temperature nickel process has been developed that produces Ohmic contacts to n-type germanium with specific contact resistivities down to (2.3 ± 1.8) x10<sup>-7</sup> Ω-cm<sup>2</sup> for anneal temperatures of 340 degC. The low contact resistivity is attributed to the low resistivity NiGe phase which was identified using electron diffraction in a transmission electron microscope. Electrical results indicate that the linear Ohmic behaviour of the contact is attributed to quantum mechanical tunnelling through the Schottky barrier formed between the NiGe alloy and the heavily doped n-Ge.<p></p>
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