1,559 research outputs found
Time course of EEG activities in continuous tracking task: a pilot study
Motor learning is crucial to surgical skills enhancement, but its neural mechanism has been investigated only using some simple tasks with limited motor involvement. This study aimed to gain more understanding of the neural dynamics during motor learning by investigating the time course of electroencephalogram (EEG) activities in the continuous tracking task that involves more motor components. One participant performed 16 trials of the continuous tracking task on Day1 and Day2 respectively. The 16-channel EEG signals were recorded and analyzed in both the resting and active states. Results showed that the tracking performance improved from Day1 to Day2. Regarding the EEG, it was found that the relative amplitude in the individual alpha band (IAB) decreased locally over primary motor cortex from the resting state to the active state on both days, and this reduction was more focused on the left primary motor cortex on Day2 compared to Day1. Moreover, in the active state the alpha coherence between central and frontal areas also significantly increased from Day1 to Day2. Time course of alpha activities may explain the tracking performance enhancement from Day1 to Day2. Future work will include more participants to extend the validity of current results.published_or_final_versio
Entanglement detection via condition of quantum correlation
We develop a novel necessary condition of quantum correlation. It is utilized
to construct -level bipartite Bell-type inequality which is strongly
resistant to noise and requires only analyses of measurement outcomes
compared to the previous result . Remarkably, a connection between
the arbitrary high-dimensional bipartite Bell-type inequality and entanglement
witnesses is found. Through the necessary condition of quantum correlation, we
propose that the witness operators to detect truly multipartite entanglement
for a generalized Greenberger-Horne-Zeilinger (GHZ) state with two local
measurement settings and a four-qubit singlet state with three settings.
Moreover, we also propose the first robust entanglement witness to detect
four-level tripartite GHZ state with only two local measurement settings
X-ray triple rings around the M87 jets in the central Virgo cluster
The Chandra X-ray data of the central Virgo cluster are re-examined to reveal
a triple-ring structure around the galaxy M87, reminiscent of the spectacular
triple-ring pattern of the SN1987A in the Large Magellanic Cloud (LMC). In the
sky plane, the two apparent smaller ellipses are roughly aligned along the M87
jets; the larger ring centers at the M87 nucleus and is likely a circle roughly
perpendicular to the M87 jet. Certain similarities of these two triple-ring
structures might hint at similar processes that operate in these two systems
with entirely different sizes and mass scales. We suspect that a major merging
event of two galaxies with nuclear supermassive black holes (SMBHs) might
create such a triple-ring structure and drove acoustic and internal gravity
waves far and near. The M87 jets are perhaps powered by a spinning SMBH
resulting from this catastrophic merging event.Comment: accepted by ApJ
Puzzles in physics
I discuss some puzzles observed in exclusive meson decays, concentrating
on the large difference between the direct CP asymmetries in the and modes, the large
branching ratio, and the large deviation of the mixing-induced CP asymmetries
in the penguins from those in the trees.Comment: 6 pages, 1 figure, talk presented at the 9th Workshop on High Energy
Physics Phenomenology, Bhubaneswar, Orissa, India, Jan. 3-14, 2006; reference
adde
A cross-sectional study on levels of second-hand smoke in restaurants and bars in five cities in China
OBJECTIVES: To assess indoor second-hand smoke (SHS) exposure in restaurants and bars via PM(2.5) (fine particles 2.5 μm in diameter and smaller) level measurements in five cities in China. METHODS: The study was conducted from July to September in 2007 in Beijing, Xi'an, Wuhan, Kunming and Guiyang. Portable aerosol monitors were used to measure PM(2.5) concentrations in 404 restaurants and bars. The occupant density and the active smoker density were calculated for each venue sampled. RESULTS: Among the 404 surveyed venues, 23 had complete smoking bans, 9 had partial smoking bans and 313 (77.5%) were observed to have allowed smoking during sampling. The geometric mean of indoor PM(2.5) levels in venues with smoking observed was 208 μg/m(3) and 99 μg/m(3) in venues without observed smoking. When outdoor PM(2.5) levels were adjusted, indoor PM(2.5) levels in venues with smoking observed were consistently significantly higher than in venues without smoking observed (F=80.49, p<0.001). Indoor PM(2.5) levels were positively correlated with outdoor PM(2.5) levels (partial rho=0.37 p<0.001) and active smoker density (partial rho=0.34, p<0.001). CONCLUSIONS: Consistent with findings in other countries, PM(2.5) levels in smoking places are significantly higher than those in smoke-free places and are strongly related to the number and density of active smokers. These findings document the high levels of SHS in hospitality venues in China and point to the urgent need for comprehensive smoke-free laws in China to protect the public from SHS hazards, as called for in Article 8 of the Framework Convention on Tobacco Control, which was ratified by China in 2005
Superluminal motion in a compact steep spectrum radio source 3C 138
We present the results of 5 GHz VLBI observations of a compact steep spectrum
source 3C 138. The data are consistent with the western end being the location
of the central activity. The observed offset between different frequencies in
the central region of 3C 138 can be accounted for by a frequency dependent
shift of the synchrotron self-absorbed core. Our new measurements confirm the
existence of a superluminal motion, but its apparent velocity of 3.3c is three
times slower than the reported one. This value is consistent with the absence
of parsec-scale counter-jet emission in the inner region, but seems still too
high to allow the overall counter-jet to be seen in terms of Doppler boosting
of an intrinsically identical jet. Either an interaction of jet with central
dense medium, or an intrinsically asymmetrical jet must be invoked to reconcile
the detected superluminal speed with the observed large scale asymmetry in 3C
138.Comment: 5 pages including 3 ps figures and 1 table, LaTex2e, accepted for
publication in Astronomy and Astrophysic
Deep underground laboratory measurement of C(,)O in the Gamow windows of the - and -processes
The C(,)O reaction is the main neutron source for
the slow-neutron-capture (s-) process in Asymptotic Giant Branch stars and for
the intermediate (i-) process. Direct measurements at astrophysical energies in
above-ground laboratories are hindered by the extremely small cross sections
and vast cosmic-ray induced background. We performed the first consistent
direct measurement in the range of 0.24 MeV to 1.9 MeV using the
accelerators at the China Jinping Underground Laboratory (CJPL) and Sichuan
University. Our measurement covers almost the entire i-process Gamow window in
which the large uncertainty of the previous experiments has been reduced from
60\% down to 15\%, eliminates the large systematic uncertainty in the
extrapolation arising from the inconsistency of existing data sets, and
provides a more reliable reaction rate for the studies of the s- and
i-processes along with the first direct determination of the alpha strength for
the near-threshold state
Multiferroic properties of Bi0.87La0.05Tb0.08FeO3 ceramics prepared by spark plasma sintering
Dense Bi0.87La0.05Tb0.08FeO3 ceramics were prepared by spark plasma sintering. The sample showed stable dielectric constant and low dielectric loss (similar to 5%), and a saturation ferroelectric loop with remnant polarization of 17 mu C/cm(2) and saturation polarization of 19 mu C/cm(2), as well as good ferromagnetism with saturation magnetization of 0.71 emu/g, at room temperature. After the sample was poled, its piezoelectric constant was measured as 12.8 pC/N, and, in particular, an obvious magnetoelectric coupling was observed. (C) 2007 American Institute of Physics
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