130,914 research outputs found
Transport properties and fluctuations in underdoped GdBa2Cu3Ox thin films
No full textWe have investigated the transport properties, resistivity and Hall effect, in a series of underdoped GdBa2Cu3Ox thin films grown by off-axis magnetron sputtering. We find a systematic correlation between the critical temperature T-c and the inverse Hall constant R-H(-1), related, in simple models, to the carrier concentration n. Our experimental thin film T-c(n) data are in good agreement with the temperature-doping phase diagram obtained for YBa2Cu3Ox, single crystals. By measuring the activation energies in the liquid vortex phase, and by using a 2-dimensional model for vortex dynamics, we have extracted the penetration depth of these samples, and studied the relation between the carrier concentration and the superfluid density to probe the role of phase fluctuations on superconductivity
Thickness effect on the structure and superconductivity of Nd1.2Ba1.8Cu3O7+x epitaxial films
No full textMeSH term explosion and author rank improve expert recommendations
No full textInformation 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
No full textThe 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
Ink-jet printing and drop-casting deposition of 2H-phase SnSe2 and WSe2 nanoflake assemblies for thermoelectric applications
No full textThe development of simple, scalable, and cost-effective methods to prepare Van der Waals materials for thermoelectric applications is a timely research field, whose potential and possibilities are still largely unexplored. In this work, we present a systematic study of ink-jet printing and drop-casting deposition of 2H phase SnSe2 and WSe2 nanoflake assemblies, obtained by liquid phase exfoliation, and their characterization in terms of electronic and thermoelectric properties. The choice of optimal annealing temperature and time is crucial for preserving phase purity and stoichiometry and for removing dry residues of ink solvents at interflake boundaries, while maximizing the sintering of nanoflakes. An additional pressing is beneficial to improve nanoflake orientation and packing, thus enhancing electric conductivity. In nanoflake assemblies deposited by drop casting and pressed at 1 GPa, we obtained thermoelectric power factors at room temperature up to 2.2 × 10-4 mW m-1 K-2 for SnSe2 and up to 3.0 × 10-4 mW m-1 K-2 for WSe2
Planar Nanoactuators Based on VO2Phase Transition
No full textActuation at micro- and nanoscale often requires large displacements and applied forces. The high work energy density that lies inside many phase transitions is an appealing feature for developing new actuating schemes, especially if the transition is reversible and scalable into small actuating domains. Here, we show the fabrication of a planar nanomechanical actuator having chevron-type geometry and based on the phase transition of VO2. This device is thermally activated through heating just above room temperature to trigger the VO2 crystalline symmetry change associated with the metal-insulator transition. The large lattice expansion of VO2 phase transition, compared to standard materials, is further amplified by the chevron-type geometry. DC and AC operation of the device are discussed
Graphite oxide nanocoatings as a sustaibale route to extend the applicability of biopolymer-based film
No full textIn this work, the Layer-by-Layer assembly of multilayered coatings comprising graphite oxide (GO) in combination with either chitosan or branched polyethylenimine was employed to modify the surface functional properties of polylactic acid (PLA) films. The aim is to extend the applicability of this biopolymer, which is of great industrial interest. Surface analyses by contact angle measurements and electron microscopy demonstrated the formation of a uniform GO layer, which enhanced the surface hydrophilicity. A 10 bi-layer coated film showed oxygen permeability reduced by 70% in both dry and humid conditions, compared to the neat PLA film. The use of a water soluble reducing agent allowed for the effective room temperature reduction of the GO deposited within the film, as evidenced by IR and contact angle measurements. GO reduction resulted in a significantly decreased surface resistivity and remarkable antistatic properties, suggesting possible applications in the field of antistatic packaging
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth 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.
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