20,523 research outputs found
Pressure Effect on the superconducting properties of LaO_{1-x}F_{x}FeAs(x=0.11) superconductor
Diamagnetic susceptibility measurements under high hydrostatic pressure (up
to 1.03 GPa) were carried out on the newly discovered Fe-based superconductor
LaO_{1-x}F_{x}FeAs(x=0.11). The transition temperature T_c, defined as the
point at the maximum slope of superconducting transition, was enhanced almost
linearly by hydrostatic pressure, yielding a dT_c/dP of about 1.2 K/GPa.
Differential diamagnetic susceptibility curves indicate that the underlying
superconducting state is complicated. It is suggested that pressure plays an
important role on pushing low T_c superconducting phase toward the main
(optimal) superconducting phase.Comment: 7 pages, 4 figure
Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China
The chemical composition of 39 cloud samples and droplet size distributions in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H2O2, sulfur( IV), organic carbon, and elemental carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 during 2007-2008 (Guo et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007-2008, but the overcompensation of ammonium led to an increase in the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 μm and most were in the range of 6.0-9.0 μm at Mt. Tai. The maximum droplet number concentration (Nd) was associated with a droplet size of 7.0 μm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets and broadened the droplet size distribution. Cloud droplets exhibited a strong interaction with atmospheric aerosols. Higher PM2.5 levels resulted in higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher PM2.5 concentrations. Clouds were an important sink for soluble materials in the atmosphere. The dilution effect of cloud water should be considered when estimating concentrations of soluble components in the cloud phase
Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China
The chemical composition of 39 cloud samples and droplet size
distributions in 24 cloud events were investigated at the summit of Mt. Tai
from July to October 2014. Inorganic ions, organic acids, metals, HCHO,
H2O2, sulfur(IV), organic carbon, and elemental carbon as well as pH and
electrical conductivity were analyzed. The acidity of the cloud water
significantly decreased from a reported value of pH 3.86 during 2007–2008 (Guo
et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate
and ammonium were both increased since 2007–2008, but the overcompensation of
ammonium led to an increase in the mean pH value. The microphysical
properties showed that cloud droplets were smaller than 26.0 µm and
most were in the range of 6.0–9.0 µm at Mt. Tai. The maximum droplet
number concentration (Nd) was associated with a droplet
size of 7.0 µm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets
and broadened the droplet size distribution. Cloud droplets exhibited a strong
interaction with atmospheric aerosols. Higher PM2. 5 levels resulted in
higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher
PM2. 5 concentrations. Clouds were an important sink for soluble materials
in the atmosphere. The dilution effect of cloud water should be considered
when estimating concentrations of soluble components in the cloud phase
Earthquake Forecast via Neutrino Tomography
We discuss the possibility of forecasting earthquakes by means of
(anti)neutrino tomography. Antineutrinos emitted from reactors are used as a
probe. As the antineutrinos traverse through a region prone to earthquakes,
observable variations in the matter effect on the antineutrino oscillation
would provide a tomography of the vicinity of the region. In this preliminary
work, we adopt a simplified model for the geometrical profile and matter
density in a fault zone. We calculate the survival probability of electron
antineutrinos for cases without and with an anomalous accumulation of electrons
which can be considered as a clear signal of the coming earthquake, at the
geological region with a fault zone, and find that the variation may reach as
much as 3% for emitted from a reactor. The case for a beam
from a neutrino factory is also investigated, and it is noted that, because of
the typically high energy associated with such neutrinos, the oscillation
length is too large and the resultant variation is not practically observable.
Our conclusion is that with the present reactor facilities and detection
techniques, it is still a difficult task to make an earthquake forecast using
such a scheme, though it seems to be possible from a theoretical point of view
while ignoring some uncertainties. However, with the development of the
geology, especially the knowledge about the fault zone, and with the
improvement of the detection techniques, etc., there is hope that a medium-term
earthquake forecast would be feasible.Comment: 6 pages, 4 figures, 1 tabl
Nernst effect of the new iron-based superconductor LaOFFeAs
We report the first Nernst effect measurement on the new iron-based
superconductor LaOFFeAs . In the normal state, the
Nernst signal is negative and very small. Below a large positive peak
caused by vortex motion is observed. The flux flowing regime is quite large
compared to conventional type-II superconductors. However, a clear deviation of
the Nernst signal from normal state background and an anomalous depression of
off-diagonal thermoelectric current in the normal state between and 50
K are observed. We propose that this anomaly in the normal state Nernst effect
could correlate with the SDW fluctuations.Comment: 8 pages, 4 figures; Latex file changed, references adde
Superconductivity induced by Ni doping in BaFeAs
A series of 122 phase BaFeNiAs ( = 0, 0.055, 0.096, 0.18,
0.23) single crystals were grown by self flux method and a dome-like Ni doping
dependence of superconducting transition temperature is discovered. The
transition temperature reaches a maximum of 20.5 K at = 0.096,
and it drops to below 4 K as 0.23. The negative thermopower in the
normal state indicates that electron-like charge carrier indeed dominates in
this system. This Ni-doped system provides another example of superconductivity
induced by electron doping in the 122 phase.Comment: 7 pages, 5 figures, revised version, added EDX result, accepted for
special issue of NJ
A framework for the successful implementation of food traceability systems in China
Implementation of food traceability systems in China faces many challenges due to the scale, diversity and complexity of China’s food supply chains. This study aims to identify critical success factors specific to the implementation of traceability systems in China. Twenty-seven critical success factors were identified in the literature. Interviews with managers at four food enterprises in a pre-study helped identify success criteria
and five additional critical success factors. These critical success factors were tested through a survey of managers in eighty-three food companies. This study identifies six dimensions for critical success factors: laws, regulations and standards; government support; consumer knowledge and support; effective management and communication; top management and vendor support; and information and system quality
The maximally entangled symmetric state in terms of the geometric measure
The geometric measure of entanglement is investigated for permutation
symmetric pure states of multipartite qubit systems, in particular the question
of maximum entanglement. This is done with the help of the Majorana
representation, which maps an n qubit symmetric state to n points on the unit
sphere. It is shown how symmetries of the point distribution can be exploited
to simplify the calculation of entanglement and also help find the maximally
entangled symmetric state. Using a combination of analytical and numerical
results, the most entangled symmetric states for up to 12 qubits are explored
and discussed. The optimization problem on the sphere presented here is then
compared with two classical optimization problems on the S^2 sphere, namely
Toth's problem and Thomson's problem, and it is observed that, in general, they
are different problems.Comment: 18 pages, 15 figures, small corrections and additions to contents and
reference
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