1,721,039 research outputs found
Exploring two-dimensional van der Waals heavy-fermion material: Data mining theoretical approach
No full textThe discovery of two-dimensional (2D) van der Waals (vdW) materials often provides interesting playgrounds to explore novel phenomena. One of the missing components in 2D vdW materials is the intrinsic heavy-fermion systems, which can provide an additional degree of freedom to study quantum critical point (QCP), unconventional superconductivity, and emergent phenomena in vdW heterostructures. Here, we investigate 2D vdW heavy-fermion candidates through the database of experimentally known compounds based on dynamical mean-field theory calculation combined with density functional theory (DFT+DMFT). We have found that the Kondo resonance state of CeSil does not change upon exfoliation and can be easily controlled by strain and surface doping. Our result indicates that CeSil is an ideal 2D vdW heavy-fermion material and the quantum critical point can be identified by external perturbations.11Nsciescopu
Suppression of long-term facilitation by Rab3-effector protein interaction
No full textLong-term facilitation (LTF) in Aplysia is achieved by the modulation of presynaptic release. However, the underlying mechanism that might be related with the regulation of synaptic vesicle release remains unknown. Since Rab3, a neuronal GTP-binding protein, is known to be a key regulator of synaptic vesicle fusion, we investigated the involvement of Rab3 in LTF. To address this issue, we examined the effect of overexpression of wild type Aplysia Rab3 (apRab3) and its mutant forms on LTF. Overexpression of either apRab3 Q80L, a constitutively active apRab3 mutant, or wild type apRab3 completely inhibited LTF. This inhibitory role of apRab3 appears to be mediated by an interaction with an effector molecule(s), possibly Rim. Expression of apRab3 Q80L, V54E double mutant, which do not bind effector molecules such as Rim or Rabphilin, had no effect on LTF Furthermore, expression of apRab3 Q80L, F18L, D19E triple mutant, which has reduced binding activity with Rim but normally binds with Rabphilin, enhanced evoked basal synaptic release, and the increase in synaptic strength occluded LTF. In conclusion, our data suggest that apRab3 may act as a negative clamp of LTF through the interaction with effector protein(s), possibly Rim. (c) 2005 Elsevier B.V. All rights reserved
Ultrafast Infrared Photoresponse from Heavily Hydrogen-Doped VO2 Single Crystalline Nanoparticles
No full textInfrared photodetectors are sought for diverse applications and their performance relies on photoactive materials and photocurrent generation mechanisms. Her; we fabricate IR photodetectors with heavily hydrogen-doped VO2(i.e., HVO2) single-crystalline nanoparticles which show two orders greater resistivities than pure VO2. The I-V plots obtained under IR light irradiation are expressed by space charge limited current mechanism and the increase in photocurrent occurs due to the increase in the number of photoinduced trap sites. This phenomenon remarkably improves the key parameters at lambda = 780 nm of high responsivity of 35280 A/W, high detectivity of 1.12 X 10(13) Jones, and strikingly fast response times of 0.6-2.5 ns, that is, 3 orders of magnitude faster than the best records of two-dimensional structures and heterostructures. Density functional theory calculations illustrate that the generation of photoinduced trap sites is attributed to the movement of hydrogen atoms to less stable interstitial sites in VO2 under light exposure.11Nsciescopu
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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Skin-Deep Aspect of Thermopower in Bi<sub>2</sub>Q<sub>3</sub>, PbQ, and BiCuQO (Q = Se, Te): Hidden One-Dimensional Character of Their Band Edges Leading to High Thermopower
No full textConspectusThermoelectric (TE) materials have received
much attention because
of their ability to convert heat energy to electrical energy. At a
given temperature T, the efficiency of a TE material
for this energy conversion is measured by the figure of merit zT, which is related to the thermopower (or Seebeck coefficient) S, the thermal conductivity κ, and the electrical
conductivity σ of the TE material as zT = (S2σT)/κ. Bi2Q3 and PbQ (Q = Se, Te) are efficient TE materials
with high zT, although they are not ecofriendly and
their stability is poor at high temperature. In principle, a TE material
can have a high zT if it has a low thermal conductivity
and a high electrical conductivity, but the latter condition is hardly
met in a real material because the parameters S,
σ and κ have a conflicting dependence on material properties.
The difficulty in searching for TE materials of high zT is even more exasperated because the relationship between the thermopower S and the carrier density n (hereafter,
the S-vs-n relationship) for the
well-known hole-doped samples of BiCuSeO showed that the hole carriers
responsible for their thermopower are associated largely with the
electronic states lying within ∼0.5 eV of its valence band
maximum (VBM). Thus, the states governing the TE properties lie in
the “skin-deep” region from the VBM. For electron-doped
TE systems, the electron carriers responsible for their thermopower
should also be associated with the electronic states lying within
∼0.5 eV of the conduction band minimum (CBM). This makes it
difficult to predict TE materials of high zT. One
faces a similar skin-deep phenomenon in searching for superconductors
of high transition temperature because the transition from a normal
metallic to a superconducting state involves the normal metallic states
in the vicinity of the Fermi level EF. Other skin-deep
phenomena in metallic compounds include the formation of charge density
wave (CDW), which involves the electronic states in the vicinity of
their Fermi levels. For magnetic materials of transition-metal ions,
the preferred orientation of their spin moments is a skin-deep phenomenon
because it is governed by the interaction between the highest-occupied
and the lowest unoccupied d-states of these ions. In the present work
we probe the issues concerning how to find the possible range of thermopower
expected for a given TE material and hence how to recognize what experimental
values of thermopower are expected or unusual. For these purposes,
we analyze the accumulated S and n data on the three well-studied TE materials, Bi2Q3, PbQ, and BiCuQO (Q = Se, Te), as representative examples,
in terms of the ideal theoretical S-vs-n relationships, which we determine for their defect-free Bi2Q3, PbQ, and BiCuQO structures using density functional
theory (DFT) calculations under the rigid band approximation. We find
that the general trends in the experimental S-vs-n relationships are reasonably well explained by the calculated S-vs-n relationships, and the carrier densities
covering these relationships are associated with the states lying
within ∼0.5 eV from their band edges confirming the skin-deep
nature of their thermoelectric properties. Despite the fact that these
TE materials are not one-dimensional (1D) in structure, they mostly
possess sharp density-of-state peaks around their band edges because
their band dispersions have a hidden 1D character so their thermopower
is generally high in magnitude
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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