4,536 research outputs found
The role of structural characteristics in problem video game playing: a review
The structural characteristics of video games may play an important role in explaining why some people play video games to excess. This paper provides a review of the literature on structural features of video games and the psychological experience of playing video games. The dominant view of the appeal of video games is based on operant conditioning theory and the notion that video games satisfy various needs for social interaction and belonging. However, there is a lack of experimental and longitudinal data that assesses the importance of specific features in video games in excessive video game playing. Various challenges in studying the structural features of video games are discussed. Potential directions for future research are outlined, notably the need to identify what problem (as opposed to casual) players seek from the video games they play
Compositional Inversion Symmetry Breaking in Ferroelectric Perovskites
Ternary cubic perovskite compounds of the form A_(1/3)A'_(1/3)A''_(1/3)BO_3
and AB_(1/3)B'_(1/3)B''_(1/3)O_3, in which the differentiated cations form an
alternating series of monolayers, are studied using first-principles methods.
Such compounds are representative of a possible new class of materials in which
ferroelectricity is perturbed by compositional breaking of inversion symmetry.
For isovalent substitution on either sublattice, the ferroelectric double-well
potential is found to persist, but becomes sufficiently asymmetric that
minority domains may no longer survive. The strength of the symmetry breaking
is enormously stronger for heterovalent substitution, so that the double-well
behavior is completely destroyed. Possible means of tuning between these
behaviors may allow for the optimization of resulting materials properties.Comment: 4 pages, two-column style with 3 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#sai_is
Electron localization : band-by-band decomposition, and application to oxides
Using a plane wave pseudopotential approach to density functional theory we
investigate the electron localization length in various oxides. For this
purpose, we first set up a theory of the band-by-band decomposition of this
quantity, more complex than the decomposition of the spontaneous polarization
(a related concept), because of the interband coupling. We show its
interpretation in terms of Wannier functions and clarify the effect of the
pseudopotential approximation. We treat the case of different oxides: BaO,
-PbO, BaTiO and PbTiO. We also investigate the variation of the
localization tensor during the ferroelectric phase transitions of BaTiO as
well as its relationship with the Born effective charges
China’s rising hydropower demand challenges water sector
Demand for hydropower is increasing, yet the water footprints (WFs) of reservoirs and hydropower, and their contributions to water scarcity, are poorly understood. Here, we calculate reservoir WFs (freshwater that evaporates from reservoirs) and hydropower WFs (the WF of hydroelectricity) in China based on data from 875 representative reservoirs (209 with power plants). In 2010, the reservoir WF totaled 27.9 × 109 m3 (Gm3), or 22% of China’s total water consumption. Ignoring the reservoir WF seriously underestimates human water appropriation. The reservoir WF associated with industrial, domestic and agricultural WFs caused water scarcity in 6 of the 10 major Chinese river basins from 2 to 12 months annually. The hydropower WF was 6.6 Gm3 yr−1 or 3.6 m3 of water to produce a GJ (109 J) of electricity. Hydropower is a water intensive energy carrier. As a response to global climate change, the Chinese government has promoted a further increase in hydropower energy by 70% by 2020 compared to 2012. This energy policy imposes pressure on available freshwater resources and increases water scarcity. The water-energy nexus requires strategic and coordinated implementations of hydropower development among geographical regions, as well as trade-off analysis between rising energy demand and water use sustainability
Born Effective Charges of Barium Titanate: band by band decomposition and sensitivity to structural features
The Born effective charge tensors of Barium Titanate have been calculated for
each of its 4 phases. Large effective charges of Ti and O, also predicted by
shell model calculations and made plausible by a simplified model, reflect the
partial covalent character of the chemical bond. A band by band decomposition
confirms that orbital hybridization is not restricted to Ti and O atoms but
also involves Ba which appears more covalent than generally assumed. Our
calculations reveal a strong dependence of the effective charges on the atomic
positions contrasting with a relative insensitivity on isotropic volume
changes.Comment: 13 page
Beyond MFV in family symmetry theories of fermion masses
Minimal Flavour Violation (MFV) postulates that the only source of flavour
changing neutral currents and CP violation, as in the Standard Model, is the
CKM matrix. However it does not address the origin of fermion masses and mixing
and models that do usually have a structure that goes well beyond the MFV
framework. In this paper we compare the MFV predictions with those obtained in
models based on spontaneously broken (horizontal) family symmetries, both
Abelian and non-Abelian. The generic suppression of flavour changing processes
in these models turns out to be weaker than in the MFV hypothesis. Despite
this, in the supersymmetric case, the suppression may still be consistent with
a solution to the hierarchy problem, with masses of superpartners below 1 TeV.
A comparison of FCNC and CP violation in processes involving a variety of
different family quantum numbers should be able to distinguish between various
family symmetry models and models satisfying the MFV hypothesis.Comment: 34 pages, no figure
Stellar Mass Black Hole Binaries as ULXs
Ultraluminous X-ray sources (ULXs) with Lx > 10^{39} ergs/s have been
discovered in great numbers in external galaxies with ROSAT, Chandra, and XMM.
The central question regarding this important class of sources is whether they
represent an extension in the luminosity function of binary X-ray sources
containing neutron stars and stellar-mass black holes (BHs), or a new class of
objects, e.g., systems containing intermediate-mass black holes (100-1000
Msun). We have carried out a theoretical study to test whether a large fraction
of the ULXs, especially those in galaxies with recent star formation activity,
can be explained with binary systems containing stellar-mass black holes. To
this end, we have applied a unique set of binary evolution models for
black-hole X-ray binaries, coupled to a binary population synthesis code, to
model the ULXs observed in external galaxies. We find that for donor stars with
initial masses >10 Msun the mass transfer driven by the normal nuclear
evolution of the donor star is sufficient to potentially power most ULXs. This
is the case during core hydrogen burning and, to an even more pronounced
degree, while the donor star ascends the giant branch, though the latter phases
lasts only ~5% of the main sequence phase. We show that with only a modest
violation of the Eddington limit, e.g., a factor of ~10, both the numbers and
properties of the majority of the ULXs can be reproduced. One of our
conclusions is that if stellar-mass black-hole binaries account for a
significant fraction of ULXs in star-forming galaxies, then the rate of
formation of such systems is ~3 x 10^{-7} per year normalized to a
core-collapse supernova rate of 0.01 per year.Comment: 15 pages, 12 figure
Ab initio study of ferroelectric domain walls in PbTiO3
We have investigated the atomistic structure of the 180-degree and 90-degree
domain boundaries in the ferroelectric perovskite compound PbTiO3 using a
first-principles ultrasoft-pseudopotential approach. For each case we have
computed the position, thickness and creation energy of the domain walls, and
an estimate of the barrier height for their motion has been obtained. We find
both kinds of domain walls to be very narrow with a similar width of the order
of one to two lattice constants. The energy of the 90-dergree domain wall is
calculated to be 35 mJ/m^2, about a factor of four lower than the energy of its
180-degree counterpart, and only a miniscule barrier for its motion is found.
As a surprising feature we detected a small offset of 0.15-0.2 eV in the
electrostatic potential across the 90-degree domain wall.Comment: 12 pages, with 9 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/bm_dw/index.htm
Screening and assessment tools for gaming disorder: A comprehensive systematic review
The inclusion of gaming disorder (GD) as an official diagnosis in the ICD-11 was a significant milestone for the field. However, the optimal measurement approaches for GD are currently unclear. This comprehensive systematic review aimed to identify and evaluate all available English-language GD tools and their corresponding evidence. A search of PsychINFO, PsychArticles, ScienceDirect, Scopus, Web of Science, and Google Scholar identified 32 tools employed in 320 studies (N = 462,249 participants). The evaluation framework examined tools in relation to: (1) conceptual and practical considerations; (2) alignment with DSM-5 and ICD-11 criteria; (3) type and quantity of studies and samples; and (4) psychometric properties. The evaluation showed that GD instrumentation has proliferated, with 2.5 tools, on average, published annually since 2013. Coverage of DSM-5 and ICD-11 criteria was inconsistent, especially for the criterion of continued use despite harm. Tools converge on the importance of screening for impaired control over gaming and functional impairment. Overall, no single tool was found to be clearly superior, but the AICA-Sgaming, GAS-7, IGDT-10, IGDS9-SF, and Lemmens IGD-9 scales had greater evidential support for their psychometric properties. The GD field would benefit from a standard international tool to identify gaming-related harms across the spectrum of maladaptive gaming behaviors.Peer reviewedFinal Accepted Versio
Lattice instabilities of PbZrO3/PbTiO3 [1:1] superlattices from first principles
Ab initio phonon calculations for the nonpolar reference structures of the
(001), (110), and (111) PbZrO_3/PbTiO_3 [1:1] superlattices are presented. The
unstable polar modes in the tetragonal (001) and (110) structures are confined
in either the Ti- or the Zr-centered layers and display two-mode behavior,
while in the cubic (111) case one-mode behavior is observed. Instabilities with
pure oxygen character are observed in all three structures. The implications
for the ferroelectric behavior and related properties are discussed.Comment: 12 pages, 2 figures, 7 tables, submitted to PR
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