130,448 research outputs found
Quantum Transport Simulations of Nano-systems: An Introduction to the Green’s Function Approach
No full textIn this chapter we present a detailed treatment of coherent charge transport at the nano-scale. To begin with, we explain the Landauer-Buttiker theory and its underlaying assumptions. Then we introduce the non-equilibrium Green’s function (NEGF) technique, which provides a powerful framework to implement the theory for real device simulations and to extend it beyond linear response. The goal of the first part of the chapter is to provide the reader with the basic knowledge required to understand and implement a NEGF-based computational scheme for non-interacting tight-binding models. The second part of the chapter illustrates how NEGF can be combined with density functional theory (DFT) to carry out first-principles simulations of nanoscale devices. We provide guidelines that will allow the reader to perform practical DFT+NEGF simulations by using the most common implementations available in electronic structure software
Translational control of globin synthesis by haemin in xenopus oocytes
No full textHemin was shown to stimulate α but not β globin synthesis by study of the translation of hemoglobin mRNA in Xenopus oocytes. Hemin acted at the translational level in this system
Ein Beitrag zur Erforschung der Steinkegelaltäre vom Typ Rungger Egg. Vorbericht über die Ausgrabungen am Wallnereck in der Gemeinde Ritten (Südtirol)
No full textA Contribution to the Study of Conical Stone Altars of the Rungger Egg Type.
Preliminary Report on the Excavations at Wallnereck in the Municipalty of Ritten(South Tyrol)The site at Wallnereck in the municipality of Ritten (Bozen province, Italy) is one of themany conical stone pyramids of the Rungger Egg or Bozen type that have often been mentioned in the literature. The excavation provides the first detailed insight into the use and characteristics of such a site. It is indeed a burnt-offering place, as has been assumed by most authors, but in the case of Wallnereck it was not the conical stone pyramid that was used as a cremation site, but instead the area below it. Additionally, a dating framework for the construction of the complex could be worked out in the stage Ha D / Lt A
MeSH 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
"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.
Enhanced thermopower in covalent graphite–molecule contacts
No full textThe Seebeck effect is very attractive for technological applications as it leads to the direct conversion of heat into electricity. One of the key quantities determining the efficiency of such conversion is the thermopower S. In this paper we explore theoretically what electronic properties are responsible for the Seebeck effect in molecular junctions with graphite or graphene electrodes. We propose that S can be enhanced because of the combined effect of the dip in the density of states at the Fermi energy of these materials and the molecular resonance. Then to understand the impact of the covalent vs. non-covalent molecule–carbon bonding we calculate from first principles the electronic and transport properties of graphite/molecule/Au junctions, where both types of bonding have been reported experimentally. We ultimately predict that S is about 120 μV K−1 at room temperature for a 3,5-dimethyl-4-aminobenzene (DMAB) molecule covalently attached to the graphite electrode. This value is one order of magnitude larger than the typical values measured to date for molecular junctions and it is a signature of the direct C–C molecule–graphite bond. Finally we also demonstrate how one can control not just the absolute magnitude of S, but also its sign by designing the graphite–molecule contact. Our results lead the way towards the use of junctions with molecules covalently attached to a C-based substrate as possible new improved platforms for molecular thermoelectric devices.A. D. was supported by the “Ministerio de Economia, Industria y Competitividad - Agencia Estatal de Investigación” of Spain through the project “Transporte Electrónico, Térmico, y de Espin con la Teoría de Funcionales de Densidad” (FIS2016-79464-P), by the Basque Government through the project “Grupos Consolidados UPV/EHU” (IT1249-19) and by the European Regional Development Fund (FEDER). The initial idea of this work was conceived by the authors during the project ACMOL (Project No. 618082) funded by the European Commission under the FP7 framework.Peer reviewe
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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