89 research outputs found
An atomic level study on the out-of-plane thermal conductivity of polycrystalline argon nanofilm
Large modulation of thermal transport in 2D semimetal triphosphides by doping-induced electron-phonon coupling
Recent studies demonstrate that novel 2D triphosphides semiconductors possess
high carrier mobility and promising thermoelectric performance, while the
carrier transport behaviors in 2D semimetal triphosphides have never been
elucidated before. Herein, using the first-principles calculations and
Boltzmann transport theory, we reveal that the electron-phonon coupling can be
significant and thus greatly inhibits the electron and phonon transport in
electron-doped BP3 and CP3. The intrinsic heat transport capacity of flexural
acoustic phonon modes in the wrinkle structure is largely suppressed arising
from the strong out-of-plane phonon scatterings, leading to the low phonon
thermal conductivity of 1.36 and 5.33 W/(mK) for BP3 and CP3 at room
temperature, and at high doping level, the enhanced scattering from electron
diminishes the phonon thermal conductivity by 71% and 54% for BP3 and CP3,
respectively. Instead, electron thermal conductivity shows nonmonotonic
variations with the increase of doping concentration, stemming from the
competition between electron-phonon scattering rates and electron group
velocity. It is worth noting that the heavy-doping effect induced strong
scattering from phonon largely suppresses the electron transport and reduces
electron thermal conductivity to the magnitude of phonon thermal conductivity.
This work sheds light on the electron and phonon transport properties in
semimetal triphosphides monolayer and provides an efficient avenue for the
modulation of carrier transport by doping-induced electron-phonon coupling
effect
Microscopic mechanism of tunable thermal conductivity in carbon nanotube-geopolymer nanocomposites
Geopolymer has been considered as a green and low-carbon material with great
potential application due to its simple synthesis process, environmental
protection, excellent mechanical properties, good chemical resistance and
durability. In this work, the molecular dynamics simulation is employed to
investigate the effect of the size, content and distribution of carbon
nanotubes on the thermal conductivity of geopolymer nanocomposites, and the
microscopic mechanism is analyzed by the phonon density of states, phonon
participation ratio and spectral thermal conductivity, etc. The results show
that there is a significant size effect in geopolymer nanocomposites system due
to the carbon nanotubes. In addition, when the content of carbon nanotubes is
16.5%, the thermal conductivity in carbon nanotubes vertical axial direction
(4.85 W/(mk)) increases 125.6% compared with the system without carbon
nanotubes (2.15 W/(mk)). However, the thermal conductivity in carbon nanotubes
vertical axial direction (1.25 W/(mk)) decreases 41.9%, which is mainly due to
the interfacial thermal resistance and phonon scattering at the interfaces. The
above results provide theoretical guidance for the tunable thermal conductivity
in carbon nanotube-geopolymer nanocomposites
Disrupted Structural Brain Connectome Is Related to Cognitive Impairment in Patients With Ischemic Leukoaraiosis
Ischemic leukoaraiosis (ILA) is related to cognitive impairment and vascular dementia in the elderly. One possible mechanism could be the disruption of white matter (WM) tracts and network function that connect distributed brain regions involved in cognition. The purpose of this study was to investigate the relationship between structural connectome and cognitive functions in ILA patients. A total of 89 patients with ILA (Fazekas score ≥ 3) and 90 healthy controls (HCs) underwent comprehensive neuropsychological examinations and diffusion tensor imaging scans. The tract-based spatial statistics approach was employed to investigate the WM integrity. Graph theoretical analysis was further applied to construct the topological architecture of the structural connectome in ILA patients. Partial correlation analysis was used to investigate the relationships between network measures and cognitive performances in the ILA group. Compared with HCs, the ILA patients showed widespread WM integrity disruptions. The ILA group displayed increased characteristic path length (Lp) and decreased global network efficiency at the level of the whole brain relative to HCs, and reduced nodal efficiencies, predominantly in the frontal–subcortical and limbic system regions. Furthermore, these structural connectomic alterations were associated with cognitive impairment in ILA patients. The association between WM changes (i.e., fractional anisotropy and mean diffusivity measures) and cognitive function was mediated by the structural connectivity measures (i.e., local network efficiency and Lp). In conclusion, cognitive impairment in ILA patients is related to microstructural disruption of multiple WM fibers and topological disorganization of structural networks, which have implications in understanding the relationship between ILA and the possible attendant cognitive impairment
- …