8,684 research outputs found
Development of an EOG (electro-oculography) based human-computer interface
Author name used in this publication: Kaiyu TongJockey Club Rehabilitation Engineering CentreRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe
Conductance plateau in quantum spin transport through an interacting quantum dot
Quantum spin transport is studied in an interacting quantum dot. It is found
that a conductance "plateau" emerges in the non-linear charge conductance by a
spin bias in the Kondo regime. The conductance plateau, as a complementary to
the Kondo peak, originates from the strong electron correlation and exchange
processes in the quantum dot, and can be regarded as one of the characteristics
in quantum spin transport.Comment: 5 pages, 5 figure
A model for luminescence of localized state ensemble
A distribution function for localized carriers,
, is proposed by solving a
rate equation, in which, electrical carriers' generation, thermal escape,
recapture and radiative recombination are taken into account. Based on this
distribution function, a model is developed for luminescence from localized
state ensemble with a Gaussian-type density of states. The model reproduces
quantitatively all the anomalous temperature behaviors of localized state
luminescence. It reduces to the well-known band-tail and luminescence quenching
models under certain approximations.Comment: 14 pages, 4 figure
Development of a Classical Force Field for the Oxidised Si Surface: Application to Hydrophilic Wafer Bonding
We have developed a classical two- and three-body interaction potential to
simulate the hydroxylated, natively oxidised Si surface in contact with water
solutions, based on the combination and extension of the Stillinger-Weber
potential and of a potential originally developed to simulate SiO2 polymorphs.
The potential parameters are chosen to reproduce the structure, charge
distribution, tensile surface stress and interactions with single water
molecules of a natively oxidised Si surface model previously obtained by means
of accurate density functional theory simulations. We have applied the
potential to the case of hydrophilic silicon wafer bonding at room temperature,
revealing maximum room temperature work of adhesion values for natively
oxidised and amorphous silica surfaces of 97 mJ/m2 and 90mJ/m2, respectively,
at a water adsorption coverage of approximately 1 monolayer. The difference
arises from the stronger interaction of the natively oxidised surface with
liquid water, resulting in a higher heat of immersion (203 mJ/m2 vs. 166
mJ/m2), and may be explained in terms of the more pronounced water structuring
close to the surface in alternating layers of larger and smaller density with
respect to the liquid bulk. The computed force-displacement bonding curves may
be a useful input for cohesive zone models where both the topographic details
of the surfaces and the dependence of the attractive force on the initial
surface separation and wetting can be taken into account
Curcumin inhibits cell proliferation of MDA-MB-231 and BT-483 breast cancer cells mediated by down-regulation of NFκB, cyclinD and MMP-1 transcription
Curcumin, an active constituent of turmeric, has been shown to possess inhibitory effect of cell proliferation and induction of apoptosis towards a board range of tumors. Cell inhibition activities of curcumin are behaved differently in various cell types. To investigate the mechanism basis for the cell inhibition of curcumin on breast cancer cell lines, we examine curcumin effect on NFκB, cell cycle regulatory proteins and matrix metalloproteinases (MMPs) in two breast cancer cell lines (MDA-MB-231 and BT-483). Cell proliferation was performed by water soluble tetrazolium WST-1 assay. The effect of curcumin's on the activity of matrix metalloproteinase-1, 3, 9 were analyzed by RT-PCR. Cell cycle regulatory protein including cyclin D1, CDK4 and p21 were examined by immunochemistry. The expressions of NFκB in breast cancer cells treated with curcumin were studied by immunochemistry and western blot. The results from WST-1 cell proliferation assay showed that curcumin exhibited the anti-proliferation effect on MDA-MB-231 and BT-483 cells in a time- and dose-dependent manner. In response to the treatment, while, the expression of cyclin D1 had declined in MDA-MB-231 and the expression of CDK4 in BT-483 had declined. MMP1 mRNA expression in BT-483 and MDA-MB-231 had significantly decreased in curcumin treatment group compared with control group. Our finding extrapolates the antitumor activity of curcumin in mediating the breast cancer cell proliferative rate and invasion by down-regulating the NFκB inducing genes. © 2009 Elsevier GmbH. All rights reserved.postprin
Biophysical controls on light response of net CO<inf>2</inf>exchange in a winter wheat field in the North China Plain
To investigate the impacts of biophysical factors on light response of net ecosystem exchange (NEE), CO2 flux was measured using the eddy covariance technique in a winter wheat field in the North China Plain from 2003 to 2006. A rectangular hyperbolic function was used to describe NEE light response. Maximum photosynthetic capacity (Pmax) was 46.6±4.0 μmol CO2 m-2 s-1 and initial light use efficiency (α) 0.059±0.006 μmol μmol-1 in April-May, two or three times as high as those in March. Stepwise multiple linear regressions showed that Pmax increased with the increase in leaf area index (LAI), canopy conductance (gc) and air temperature (Ta) but declined with increasing vapor pressure deficit (VPD) (P25°C or VPD>1.1-1.3 kPa, NEE residual increased with the increase in Ta and VPD (P<0.001), indicating that temperature and water stress occurred. When gc was more than 14 mm s-1 in March and May and 26 mm s-1 in April, the NEE residuals decline disappeared, or even turned into an increase in gc(P<0.01), implying shifts from stomatal limitation to non-stomatal limitation on NEE. Although the differences between sunny and cloudy sky conditions were unremarkable for light response parameters, simulated net CO2 uptake under the same radiation intensity averaged 18% higher in cloudy days than in sunny days during the year 2003-2006. It is necessary to include these effects in relevant carbon cycle models to improve our estimation of carbon balance at regional and global scales. © 2014 Tong et al
Constraints on holographic dark energy models using the differential ages of passively evolving galaxies
Using the absolute ages of passively evolving galaxies observed at different
redshifts, one can obtain the differential ages, the derivative of redshift
with respect to the cosmic time (i.e. ). Thus, the
Hubble parameter can be measured through the relation . By comparing the measured Hubble parameter at different
redshifts with the theoretical one containing free cosmological parameters, one
can constrain current cosmological models. In this paper, we use this method to
present the constraint on a spatially flat Friedman-Robert-Walker Universe with
a matter component and a holographic dark energy component, in which the
parameter plays a significant role in this dark energy model. Firstly we
consider three fixed values of =0.6, 1.0 and 1.4 in the fitting of data. If
we set free, the best fitting values are , ,
. It is shown that the holographic dark energy behaves like a
quintom-type at the level. This result is consistent with some other
independent cosmological constrains, which imply that is favored. We
also test the results derived from the differential ages using another
independent method based on the lookback time to galaxy clusters and the age of
the universe. It shows that our results are reliable.Comment: 18 pages including 7 figures and 1 tables. Final version for
publication in Modern Physics Letters A (MPLA)[minor revision to match the
appear version
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