173,871 research outputs found
Phase Diffusion in Single-Walled Carbon Nanotube Josephson Transistors
We investigate electronic transport in Josephson junctions formed by
single-walled carbon nanotubes coupled to superconducting electrodes. We
observe enhanced zero-bias conductance (up to 10e^2/h) and pronounced
sub-harmonic gap structures in differential conductance, which arise from the
multiple Andreev reflections at superconductor/nanotube interfaces. The
voltage-current characteristics of these junctions display abrupt switching
from the supercurrent branch to resistive branch, with a gate-tunable switching
current ranging from 50 pA to 2.3 nA. The finite resistance observed on the
supercurrent branch and the magnitude of the switching current are in good
agreement with calculation based on the model of classical phase diffusion
Design and analysis of a wire-driven flexible manipulator for bronchoscopic interventions
Bronchoscopic interventions are widely performed for the diagnosis and treatment of lung diseases. However, for most endobronchial devices, the lack of a bendable tip restricts their access ability to get into distal bronchi with complex bifurcations. This paper presents the design of a new wire-driven continuum manipulator to help guide these devices. The proposed manipulator is built by assembling miniaturized blocks that are featured with interlocking circular joints. It has the capability of maintaining its integrity when the lengths of actuation wires change due to the shaft flex. It allows the existence of a relatively large central cavity to pass through other instruments and enables two rotational degrees of freedom. All these features make it suitable for procedures where tubular anatomies are involved and the flexible shafts have to be considerably bent in usage, just like bronchoscopic interventions. A kinematic model is built to estimate the relationship between the translations of actuation wires and the manipulator tip position. A scale-up model is produced for evaluation experiments and the results validate the performance of the proposed mechanism
Urban Regeneration of Industrial Areas: Affordable Housing for Low Income Populations in Cities
The UK-China Sustainable Development Dialogue (SDD) is a partnership between the UK and Chinese Governments to promote collaboration and good practice on sustainable development. It is framed by a 2004 joint Prime Ministerial declaration and was formally established in 2005 by an agreement signed by UK Deputy Prime Minister John Prescott and State Councillor Tang. The SDD was founded on the recognition that, in an interdependent world, international co-operation is needed to ensure that learning is shared and efforts are made collectively towards achieving common goals. This report is the 13th and Final Paper in the SDD (Urban Strand. It draws together the core conclusions from the previous twelve papers and offers recommendations for taking the dialogue forward
Information filtering via biased heat conduction
Heat conduction process has recently found its application in personalized
recommendation [T. Zhou \emph{et al.}, PNAS 107, 4511 (2010)], which is of high
diversity but low accuracy. By decreasing the temperatures of small-degree
objects, we present an improved algorithm, called biased heat conduction (BHC),
which could simultaneously enhance the accuracy and diversity. Extensive
experimental analyses demonstrate that the accuracy on MovieLens, Netflix and
Delicious datasets could be improved by 43.5%, 55.4% and 19.2% compared with
the standard heat conduction algorithm, and the diversity is also increased or
approximately unchanged. Further statistical analyses suggest that the present
algorithm could simultaneously identify users' mainstream and special tastes,
resulting in better performance than the standard heat conduction algorithm.
This work provides a creditable way for highly efficient information filtering.Comment: 4 pages, 3 figure
Local spin polarisation of electrons in Rashba semiconductor nanowires: effects of the bound state
The local spin polarisation (LSP) of electrons in two typical semiconductor
nanowires under the modulation of Rashba spin-orbit interaction (SOI) is
investigated theoretically. The influence of both the SOI- and
structure-induced bound states on the LSP is taken into account via the
spin-resolved lattice Green function method. It is discovered that high
spin-density islands with alternative signs of polarisation are formed inside
the nanowires due to the interaction between the bound states and the Rashba
effective magnetic field. Further study shows that the spin-density islands
caused by the structure-induced bound state exhibit a strong robustness against
disorder. These findings may provide an efficient way to create local magnetic
moments and store information in semiconductors.Comment: 8 pages, 3 figure
Charge Inversion of Divalent Ionic Solutions in Silica Channels
Recent experiments (F.H.J. Van Der Heyden et al., PRL 96, 224502 (2006)) of
streaming currents in silica nanochannels with divalent ions report charge
inversion, i.e. interfacial charges attracting counterions in excess of their
own nominal charge, in conflict with existing theoretical and simulation
results. We reveal the mechanism of charge inversion by using all-atomic
molecular dynamics simulations. Our results show excellent agreement with
experiments, both qualitatively and quantitatively. We further discuss the
implications of our study for the general problem of ionic correlations in
solutions as well as in regards of the properties of silica-water interfaces.Comment: 5 pages, 5 figure
A study of the parity-odd nucleon-nucleon potential
We investigate the parity-violating nucleon-nucleon potential as obtained in
chiral effective field theory. By using resonance saturation we compare the
chiral potential to the more traditional one-meson exchange potential. In
particular, we show how parameters appearing in the different approaches can be
compared with each other and demonstrate that analyses of parity violation in
proton-proton scattering within the different approaches are in good agreement.
In the second part of this work, we extend the parity-violating potential to
next-to-next-to-leading order. We show that generally it includes both
one-pion- and two-pion-exchange corrections, but the former play no significant
role. The two-pion-exchange corrections depend on five new low-energy constants
which only become important if the leading-order weak pion-nucleon constant
turns out to be very small.Comment: Published versio
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Natural and anthropogenic forest fires recorded in the Holocene pollen record from a Jinchuan peat bog, northeastern China
Pollen and charcoal particles from a Jinchuan peat (northeastern China) were examined to investigate the fire origin and interaction between
climate, vegetation, fire and human activity during the Holocene. Pollen results show that: (i) a broadleaved deciduous forest was dominant during
the early Holocene; (ii) from ~5500 cal. yr B.P. there was a gradual increase in coniferous trees (mainly Pinus), and a decrease in broadleaved
deciduous trees (e.g. Quercus, Juglans, and Ulmus–Zelkova); (iii) after ~4200 cal. yr B.P., the deciduous forest was replaced by a mixed forest of
coniferous and deciduous trees; (iv) coniferous trees including Pinus, Abies and Picea further increased after ~2000 cal. yr B.P., reflecting a
cooler and drier climate after ~5500–4200 cal. yr B.P. Two layers of abundant microfossil charcoal particles (250–10 μm) and the coexistence of
macrofossil particles (N2 mm) suggest two local fires: fire event 1 (5120±66 cal. yr B.P.) and fire event 2 (1288±8 cal. yr B.P., AD 662±8).
Charcoal layer 1, with a large amount of Monolete psilate spores, is superimposed on the long-term trend of vegetation changes, indicating a
natural origin for fire event 1 that was probably facilitated by drying environmental conditions since the mid-Holocene. Cerealia-type pollen and a
low percentage of Monolete psilate spores were observed in charcoal layer 2, indicating that fire event 2 was caused by clearing. We suggest that
fire event 2 may be related to the spread of the Han farming culture accompanied by the territorial expansion of the Tang Dynasty to the studied
area in AD 668
The Numerical Solution of Scalar Field for Nariai Case in 5D Ricci-flat SdS Black String Space with Polynomial Approximation
As one exact candidate of the higher dimensional black hole, the 5D
Ricci-flat Schwarzschild-de Sitter black string space presents something
interesting. In this paper, we give a numerical solution to the real scalar
field around the Nariai black hole by the polynomial approximation. Unlike the
previous tangent approximation, this fitting function makes a perfect match in
the leading intermediate region and gives a good description near both the
event and the cosmological horizons. We can read from our results that the wave
is close to a harmonic one with the tortoise coordinate. Furthermore, with the
actual radial coordinate the waves pile up almost equally near the both
horizons.Comment: 8 pages, 4 figure
Chemical abundance analysis of 19 barium stars
We aim at deriving accurate atmospheric parameters and chemical abundances of
19 barium (Ba) stars, including both strong and mild Ba stars, based on the
high signal-to-noise ratio and high resolution Echelle spectra obtained from
the 2.16 m telescope at Xinglong station of National Astronomical
Observatories, Chinese Academy of Sciences. The chemical abundances of the
sample stars were obtained from an LTE, plane-parallel and line-blanketed
atmospheric model by inputting the atmospheric parameters (effective
temperatures, surface gravities, metallicity and microturbulent velocity) and
equivalent widths of stellar absorption lines. These samples of Ba stars are
giants indicated by atmospheric parameters, metallicities and kinematic
analysis about UVW velocity. Chemical abundances of 17 elements were obtained
for these Ba stars. Their light elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr,
Mn and Ni) are similar to the solar abundances. Our samples of Ba stars show
obvious overabundances of neutron-capture (n-capture) process elements relative
to the Sun. Their median abundances of [Ba/Fe], [La/Fe] and [Eu/Fe] are 0.54,
0.65 and 0.40, respectively. The YI and ZrI abundances are lower than Ba, La
and Eu, but higher than the light elements for the strong Ba stars and similar
to the iron-peak elements for the mild stars. There exists a positive
correlation between Ba intensity and [Ba/Fe]. For the n-capture elements (Y,
Zr, Ba, La), there is an anti-correlation between their [X/Fe] and [Fe/H]. We
identify nine of our sample stars as strong Ba stars with [Ba/Fe]>0.6 where
seven of them have Ba intensity Ba=2-5, one has Ba=1.5 and another one has
Ba=1.0. The remaining ten stars are classified as mild Ba stars with
0.17<[Ba/Fe]<0.54
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