23,495 research outputs found
Electron Delocalization in Gate-Tunable Gapless Silicene
The application of a perpendicular electric field can drive silicene into a
gapless state, characterized by two nearly fully spin-polarized Dirac cones
owing to both relatively large spin-orbital interactions and inversion symmetry
breaking. Here we argue that since inter-valley scattering from non-magnetic
impurities is highly suppressed by time reversal symmetry, the physics should
be effectively single-Dirac-cone like. Through numerical calculations, we
demonstrate that there is no significant backscattering from a single impurity
that is non-magnetic and unit-cell uniform, indicating a stable delocalized
state. This conjecture is then further confirmed from a scaling of conductance
for disordered systems using the same type of impurities.Comment: 6 pages, 3 figures, published versio
The future design direction of smart clothing development
Literature indicates that Smart Clothing applications, the next generation of clothing and
electronic products, have been struggling to enter the mass market because the consumers’
latent needs have not been recognised. Moreover, the design direction of Smart Clothes
remains unclear and unfocused. Nevertheless, a clear design direction is necessary for all
product development. Therefore, this research aims to identify the design directions of the
emerging Smart Clothes industry by conducting a questionnaire survey and focus groups
with its major design contributors. The results reveal that the current strategy of embedding
a wide range of electronic functions in a garment is not suitable. This is primarily because it
does not match the users’ requirements, purchasing criteria and lifestyle. The results
highlight the respondents’ preference for personal healthcare and sportswear applications
that suit their lifestyle, are aesthetically attractive, and provide a practical function
Four dual AGN candidates observed with the VLBA
According to hierarchical structure formation models, merging galaxies are
expected to be seen in different stages of their coalescence. However,
currently there are no straightforward observational methods neither to select
nor to confirm a large number of dual active galactic nuclei (AGN) candidates.
Most attempts involve the better understanding of double-peaked narrow emission
line sources, to distinguish the objects where the emission lines originate
from narrow-line kinematics or jet-driven outflows from those which might
harbour dual AGN. We observed four such candidate sources with the Very Long
Baseline Array (VLBA) at 1.5 GHz with 10 milli-arcsecond angular
resolution where spectral profiles of AGN optical emission suggested the
existence of dual AGN. In SDSS J210449.13-000919.1 and SDSS J23044.82-093345.3,
the radio structures are aligned with the optical emission features, thus the
double-peaked emission lines might be the results of jet-driven outflows. In
the third detected source SDSS J115523.74+150756.9, the radio structure is less
extended and oriented nearly perpendicular to the position angle derived from
optical spectroscopy. The fourth source remained undetected with the VLBA but
it has been imaged with the Very Large Array at arcsec resolution a few months
before our observations, suggesting the existence of extended radio structure.
In none of the four sources did we detect two radio-emitting cores, a
convincing signature of duality.Comment: 35 pages, 3 figures, 2 tables, accepted for publication in Ap
The radio structure of 3C 316, a galaxy with double-peaked narrow optical emission lines
The galaxy 3C\,316 is the brightest in the radio band among the
optically-selected candidates exhibiting double-peaked narrow optical emission
lines. Observations with the Very Large Array (VLA), Multi-Element Remotely
Linked Interferometer Network (e-MERLIN), and the European VLBI Network (EVN)
at 5\,GHz have been used to study the radio structure of the source in order to
determine the nature of the nuclear components and to determine the presence of
radio cores. The e-MERLIN image of 3C 316 reveals a collimated coherent
east-west emission structure with a total extent of about 3 kpc. The EVN image
shows seven discrete compact knots on an S-shaped line. However, none of these
knots could be unambiguously identified as an AGN core. The observations
suggest that the majority of the radio structure belongs to a powerful radio
AGN, whose physical size and radio spectrum classify it as a compact
steep-spectrum source. Given the complex radio structure with radio blobs and
knots, the possibility of a kpc-separation dual AGN cannot be excluded if the
secondary is either a naked core or radio quiet.Comment: 12 pages, 3 figures, 2 tables. Accepted for publication in the MNRA
Parsec-scale jet properties of the gamma-ray quasar 3C 286
The quasar 3C~286 is one of two compact steep spectrum sources detected by
the {\it Fermi}/LAT. Here, we investigate the radio properties of the
parsec(pc)-scale jet and its (possible) association with the -ray
emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at
various frequencies reveal a one-sided core--jet structure extending to the
southwest at a projected distance of 1 kpc. The component at the jet base
showing an inverted spectrum is identified as the core, with a mean brightness
temperature of ~K. The jet bends at about 600 pc (in
projection) away from the core, from a position angle of to
. Based on the available VLBI data, we inferred the proper motion
speed of the inner jet as mas yr (), corresponding to a jet speed of about at an inclination
angle of between the jet and the line of sight of the observer. The
brightness temperature, jet speed and Lorentz factor are much lower than those
of -ray-emitting blazars, implying that the pc-scale jet in 3C~286 is
mildly relativistic. Unlike blazars in which -ray emission is in
general thought to originate from the beamed innermost jet, the location and
mechanism of -ray emission in 3C~286 may be different as indicated by
the current radio data. Multi-band spectrum fitting may offer a complementary
diagnostic clue of the -ray production mechanism in this source.Comment: 9 pages, 4 figures, accept for publication in MNRA
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