967 research outputs found
The Electronic and Superconducting Properties of Oxygen-Ordered MgB2 compounds of the form Mg2B3Ox
Possible candidates for the Mg2B3Ox nanostructures observed in bulk of
polycrystalline MgB2 (Ref.1) have been studied using a combination of
Z-contrast imaging, electron energy loss spectroscopy (EELS) and
first-principles calculations. The electronic structures, phonon modes, and
electron phonon coupling parameters are calculated for two oxygen-ordered MgB2
compounds of composition Mg2B3O and Mg2B3O2, and compared with those of MgB2.
We find that the density of states for both Mg2B3Ox structures show very good
agreement with EELS, indicating that they are excellent candidates to explain
the observed coherent oxygen precipitates. Incorporation of oxygen reduces the
transition temperature and gives calculated TC values of 18.3 K and 1.6 K for
Mg2B3O and Mg2B3O2, respectively.Comment: Submitted to PR
Planning for Electric Vehicles Coupled with Urban Mobility
The rising adoption of plug-in electric vehicles (PEVs) leads to the
alignment of their electricity and their mobility demands. Therefore,
transportation and power infrastructures are becoming increasingly
interdependent. In this work, we uncover patterns of PEV mobility by
integrating for the first time two unique data sets: (i) mobile phone activity
of 1.39 million Bay Area residents and (ii) charging activity of PEVs in
580,000 sessions obtained in the same region. We present a method to estimate
individual mobility of PEV drivers at fine temporal and spatial resolution
integrating survey data with mobile phone data and income information obtained
from census. Thereupon, we recommend changes in PEVs charging times of
commuters at their work stations that take into account individual travel needs
and shave the pronounced peak in power demand. Informed by the tariff of
electricity, we calculate the12 monetary gains to incentivize the adoption of
the recommendations. These results open avenues for planning for the future of
coupled transportation and electricity needs using personalized data
Near-infrared Hong-Ou-Mandel interference on a silicon quantum photonic circuit
Near-infrared Hong-Ou-Mandel quantum interference is observed in silicon
nanophotonic directional couplers with raw visibilities on-chip at 90.5%.
Spectrally-bright 1557-nm two-photon states are generated in a
periodically-poled KTiOPO4 waveguide chip, serving as the entangled photon
source and pumped with a self-injection locked laser, for the photon
statistical measurements. Efficient four-port coupling in the communications
C-band and in the high-index-contrast silicon photonics platform is
demonstrated, with matching theoretical predictions of the quantum interference
visibility. Constituents for the residual quantum visibility imperfection are
examined, supported with theoretical analysis of the sequentially-triggered
multipair biphoton contribution and techniques for visibility compensation,
towards scalable high-bitrate quantum information processing and
communications.Comment: 15 pages, 6 figure
BIM Adoption in the Cambodian Construction Industry: Key Drivers and Barriers
Critical issues surrounding the promotion and adoption of building information modeling (BIM) for construction projects are largely country-specific due to contextual socio-cultural, economic, and regulatory environments impacting construction operations and outcomes. There is little information on BIM adoption issues specific to the Cambodian construction industry (‘the industry’). This paper aims to narrow existing knowledge by investigating key drivers for, and barriers to the adoption of BIM in the industry. Using descriptive survey method, feedback was received from contractors and architects that were registered with their respective trade and professional associations in the industry. The multi-attribute method and the Statistical Package for the Social Sciences (SPSS)-based Kendall’s coefficient of concordance (W) test were used to analyze the empirical datasets. Results showed that out of the 13 significant drivers identified in the study, the most influential comprised the technology’s ability to remarkably enhance project visualization and schedule performance; this is followed by awareness that the technology is redefining how project information is created and shared among stakeholders and therefore the future of the industry that cannot be ignored. On the other hand, the most constraining barrier to the adoption of the technology, out of 19 significant barriers, related to strong industry resistance to change, especially reluctance to change from 2D drafting to 3D modeling; other highly rated barriers included the high initial cost of the software and the shortage of professionals with BIM skills. Implementation of the study findings could support greater uptake of the technology and the leveraging of its key benefits to improving project success and the growth of the Cambodian construction industry, as well as those of other developing economies that share similar socio-cultural, economic, and regulatory environments
Micro-Environment Causes Reversible Changes in DNA Methylation and mRNA Expression Profiles in Patient-Derived Glioma Stem Cells
In vitro and in vivo models are widely used in cancer research. Characterizing the similarities and differences between a patient\u27s tumor and corresponding in vitro and in vivo models is important for understanding the potential clinical relevance of experimental data generated with these models. Towards this aim, we analyzed the genomic aberrations, DNA methylation and transcriptome profiles of five parental tumors and their matched in vitro isolated glioma stem cell (GSC) lines and xenografts generated from these same GSCs using high-resolution platforms. We observed that the methylation and transcriptome profiles of in vitro GSCs were significantly different from their corresponding xenografts, which were actually more similar to their original parental tumors. This points to the potentially critical role of the brain microenvironment in influencing methylation and transcriptional patterns of GSCs. Consistent with this possibility, ex vivo cultured GSCs isolated from xenografts showed a tendency to return to their initial in vitro states even after a short time in culture, supporting a rapid dynamic adaptation to the in vitro microenvironment. These results show that methylation and transcriptome profiles are highly dependent on the microenvironment and growth in orthotopic sites partially reverse the changes caused by in vitro culturing
Tests and applications of self-consistent cranking in the interacting boson model
The self-consistent cranking method is tested by comparing the cranking
calculations in the interacting boson model with the exact results obtained
from the SU(3) and O(6) dynamical symmetries and from numerical
diagonalization. The method is used to study the spin dependence of shape
variables in the and boson models. When realistic sets of parameters
are used, both models lead to similar results: axial shape is retained with
increasing cranking frequency while fluctuations in the shape variable
are slightly reduced.Comment: 9 pages, 3 ps figures, Revte
Ab Initio Structural Energetics of Beta-Si3N4 Surfaces
Motivated by recent electron microscopy studies on the Si3N4/rare-earth oxide
interfaces, the atomic and electronic structures of bare beta-Si3N4 surfaces
are investigated from first principles. The equilibrium shape of a Si3N4
crystal is found to have a hexagonal cross section and a faceted dome-like base
in agreement with experimental observations. The large atomic relaxations on
the prismatic planes are driven by the tendency of Si to saturate its dangling
bonds, which gives rise to resonant-bond configurations or planar sp^2-type
bonding. We predict three bare surfaces with lower energies than the open-ring
(10-10) surface observed at the interface, which indicate that
non-stoichiometry and the presence of the rare-earth oxide play crucial roles
in determining the termination of the Si3N4 matrix grains.Comment: 4 Pages, 4 Figures, 1 tabl
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