7,281 research outputs found
Municipal sewage sludge compost promotes Mangifera persiciforma tree growth with no risk of heavy metal contamination of soil
Helical edge and surface states in HgTe quantum wells and bulk insulators
The quantum spin Hall (QSH) effect is the property of a new state of matter
which preserves time-reversal, has an energy gap in the bulk, but has
topologically robust gapless states at the edge. Recently, it has been shown
that HgTe quantum wells realize this novel effect. In this work, we start from
realistic tight-binding models and demonstrate the existence of the helical
edge states in HgTe quantum wells and calculate their physical properties. We
also show that 3d HgTe is a topological insulator under uniaxial strain, and
show that the surface states are described by single-component massless
relativistic Dirac fermions in 2+1 dimensions. Experimental predictions are
made based on the quantitative results obtained from realistic calculations.Comment: 5 page
Quantum Anomalous Hall Effect in HgMnTe Quantum Wells
The quantum Hall effect is usually observed when the two-dimensional electron
gas is subjected to an external magnetic field, so that their quantum states
form Landau levels. In this work we predict that a new phenomenon, the quantum
anomalous Hall effect, can be realized in HgMnTe quantum wells,
without the external magnetic field and the associated Landau levels. This
effect arises purely from the spin polarization of the atoms, and the
quantized Hall conductance is predicted for a range of quantum well thickness
and the concentration of the atoms. This effect enables dissipationless
charge current in spintronics devices.Comment: 5 pages, 3 figures. For high resolution figures see final published
version when availabl
A large sample of low surface brightness disk galaxies from the SDSS. I: The sample and the stellar populations
We present the properties of a large sample (12,282) of nearly face-on low
surface brightness (LSB) disk galaxies selected from the main galaxy sample of
SDSS-DR4. These properties include B-band central surface brightness mu_0(B),
scale lengths h, integrated magnitudes, colors, and distances D. This sample
has mu_0(B) values from 22 to 24.5 mag arcsec^{-2} with a median value of 22.42
mag arcsec^{-2}, and disk scale lengths ranging from 2 to 19 kpc. They are
quite bright with M_B taking values from -18 to -23 mag with a median value of
-20.08 mag. There exist clear correlations between logh and M_B, logh and logD,
logD and M_B. However, no obvious correlations are found between mu_0(B) and
logh, colors etc. The correlation between colors and logh is weak even though
it exists. Both the optical-optical and optical-NIR color-color diagrams
indicate that most of them have a mixture of young and old stellar populations.
They also satisfy color-magnitude relations, which indicate that brighter
galaxies tend generally to be redder. The comparison between the LSBGs and a
control sample of nearly face-on disk galaxies with higher surface brightness
(HSB) with mu_0(B) from 18.5 to 22 mag arcsec^{-2} show that, at a given
luminosity or distance, the observed LSB galaxies tend to have larger scale
lengths. These trends could be seen gradually by dividing both the LSBGs and
HSBGs into two sub-groups according to surface brightness. A volume-limited
sub-sample was extracted to check the incompleteness of surface brightness. The
only one of the property relations having an obvious change is the relation of
logh versus mu_0(B), which shows a correlation in this sub-sample.Comment: 14 pages, 18 figures, accepted for publication in MNRA
Comparing the Host Galaxies of Type Ia, Type II and Type Ibc Supernovae
We compare the host galaxies of 902 supernovae, including SNe Ia, SNe II and
SNe Ibc, which are selected by cross-matching the Asiago Supernova Catalog with
the SDSS Data Release 7. We further selected 213 galaxies by requiring the
light fraction of spectral observations 15%, which could represent well the
global properties of the galaxies. Among them, 135 galaxies appear on the
Baldwin-Phillips-Terlevich diagram, which allows us to compare the hosts in
terms of star-forming, AGNs (including composites, LINERs and Seyfert 2s) and
"Absorp" (their related emission-lines are weak or non-existence) galaxies. The
diagrams related to parameters D(4000), H, stellar masses, SFRs
and specific SFRs for the SNe hosts show that almost all SNe II and most of SNe
Ibc occur in SF galaxies, which have a wide range of stellar mass and low
D(4000). The SNe Ia hosts as SF galaxies follow similar trends. A
significant fraction of SNe Ia occurs in AGNs and Absorp galaxies, which are
massive and have high D(4000). The stellar population analysis from
spectral synthesis fitting shows that the hosts of SNe II have a younger
stellar population than hosts of SNe Ia. These results are compared with those
of the 689 comparison galaxies where the SDSS fiber captures less than 15% of
the total light. These comparison galaxies appear biased towards higher
12+log(O/H) (0.1dex) at a given stellar mass. Therefore, we believe the
aperture effect should be kept in mind when the properties of the hosts for
different types of SNe are discussed.Comment: 15 pages, 9 figure
An implementation of synthetic generation of wind data series
Wind power fluctuation is a major concern of large scale wind power grid integration. To test methods proposed for wind power grid integration, a large amount of wind data with time series are necessary and will be helpful to improve the methods. Meanwhile, due to the short operation history of most wind farms as well as limitations of data collections, the data obtained from wind farms could not satisfy the needs of data analysis. Consequently, synthetic generation of wind data series could be one of the effective solutions for this issue. In this paper, a method is presented for generating wind data series using Markov chain. Due to the high order Markov chain, the possibility matrix designed for a wind farm could cost a lot of memory, which is a problem with current computer technologies. Dynamic list will be introduced in this paper to reduce the memory required. Communication errors are un-avoidable on long way signal transmission between the control centre and wind farms. Missing of data always happens in the historical wind data series. Using these data to generate wind data series may result in some mistakes when searching related elements in the probability matrix. An adaptive method will be applied in this paper to solve the problem. The proposed method will be verified using a set of one-year historical data. The results show that the method could generate wind data series in an effective way. © 2013 IEEE.published_or_final_versio
The effects of indoor air pollution from solid fuel use on cognitive function among middle-aged and older population in China
Objectives
Growing evidence has linked outdoor air pollution exposure with higher risk of cognitive impairments. However, the role of indoor air pollution in cognitive decline is not well elaborated. By using nationally representative longitudinal data, this study aimed to explore the effects of indoor air pollution from solid fuel use on cognitive function among middle-aged and older individuals in China.
Methods
Data were obtained from 2011-2015 waves of CHARLS (China Health and Retirement Longitudinal Study). Scores from the Telephone Interview of Cognitive Status and figure drawing/word recall tests were used to measure cognitive function in 39,482 individuals. Exposure to indoor air pollution was measured as use of solid fuel for cooking. Solid fuel was defined as coal, biomass charcoal, wood, and straw; clean fuel was defined as liquefied gas, natural gas, and electricity. Linear mixed effect models were applied to examine the effect of indoor air pollution from solid fuel use on cognitive function.
Results
Participants had an average global cognitive function of 9.67 (SD=4.13). Solid fuel users made up 49.71% of participants, but this proportion was much greater among those living in rural areas (64.22%). Compared with clean fuel users, solid fuel users had worse cognitive function. On average, solid fuel users had a 0.81 (95%CI: -0.89,-0.73) lower global cognition score, 0.63 (95%CI: -0.69,-0.57) lower mental health score, and 0.16 (95%CI: -0.22,-0.14) lower episodic memory score. These effects were stronger among participants who are female, aged 65 years old and above, have education level of primary school and below, or have cardiovascular diseases.
Conclusions
These results provide evidence for the role of indoor air pollution in neurobehavioral disorders in China. Promotion of practices like expanded use of clean fuel and improved stoves in households may be crucial to significantly reduce indoor air pollution and protect mental health
Screening of external magnetic perturbation fields due to sheared plasma flow
Within the single fluid resistive magnetohydrodynamic model, systematic toroidal modelling efforts are devoted to investigate the plasma response induced screening of the applied external 3D magnetic field perturbations in the presence of sheared toroidal flow. One particular issue of interest is addressed, when the local flow speed approaches zero at the perturbation rational surface inside the plasma. Subtle screening physics, associated with the favourable averaged toroidal curvature effect (the GGJ effect (Glasser et al 1975 Phys. Fluids 7 875)), is found to play an essential role during slow flow near the rational surface by enhancing the screening at reduced flow. A strong cancellation effect between different terms of Ohm's law is discovered, leading to different screening physics in the GGJ regime, as compared to that of conventional screening of the typical resistive-inertial regime occurring at faster flow. These modelling results may be applicable to interpret certain mode locking experiments, as well as type-I edge localized mode suppression experiments, with resonant magnetic field perturbations being applied to tokamak plasmas at low input toroidal torque
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