106,949 research outputs found
Dimerization-assisted energy transport in light-harvesting complexes
We study the role of the dimer structure of light-harvesting complex II (LH2)
in excitation transfer from the LH2 (without a reaction center (RC)) to the LH1
(surrounding the RC), or from the LH2 to another LH2. The excited and
un-excited states of a bacteriochlorophyll (BChl) are modeled by a quasi-spin.
In the framework of quantum open system theory, we represent the excitation
transfer as the total leakage of the LH2 system and then calculate the transfer
efficiency and average transfer time. For different initial states with various
quantum superposition properties, we study how the dimerization of the B850
BChl ring can enhance the transfer efficiency and shorten the average transfer
time.Comment: 11 pages, 6 figure
Learning a Mixture of Deep Networks for Single Image Super-Resolution
Single image super-resolution (SR) is an ill-posed problem which aims to
recover high-resolution (HR) images from their low-resolution (LR)
observations. The crux of this problem lies in learning the complex mapping
between low-resolution patches and the corresponding high-resolution patches.
Prior arts have used either a mixture of simple regression models or a single
non-linear neural network for this propose. This paper proposes the method of
learning a mixture of SR inference modules in a unified framework to tackle
this problem. Specifically, a number of SR inference modules specialized in
different image local patterns are first independently applied on the LR image
to obtain various HR estimates, and the resultant HR estimates are adaptively
aggregated to form the final HR image. By selecting neural networks as the SR
inference module, the whole procedure can be incorporated into a unified
network and be optimized jointly. Extensive experiments are conducted to
investigate the relation between restoration performance and different network
architectures. Compared with other current image SR approaches, our proposed
method achieves state-of-the-arts restoration results on a wide range of images
consistently while allowing more flexible design choices. The source codes are
available in http://www.ifp.illinois.edu/~dingliu2/accv2016
Multipartite quantum correlation and entanglement in four-qubit pure states
Based on the quantitative complementarity relations, we analyze thoroughly
the properties of multipartite quantum correlations and entanglement in
four-qubit pure states. We find that, unlike the three-qubit case, the single
residual correlation, the genuine three- and four-qubit correlations are not
suited to quantify entanglement. More interestingly, from our qualitative and
numerical analysis, it is conjectured that the sum of all the residual
correlations may constitute a good measure for the total multipartite
entanglement in the system.Comment: 7 pages, 3 figue
Estrogenic chemicals often leach from BPA-free plastic products that are replacements for BPA-containing polycarbonate products
Background: Xenobiotic chemicals with estrogenic activity (EA), such as bisphenol A (BPA), have been reported to
have potential adverse health effects in mammals, including humans, especially in fetal and infant stages. Concerns
about safety have caused many manufacturers to use alternatives to polycarbonate (PC) resins to make hard and
clear, reusable, plastic products that do not leach BPA. However, no study has focused on whether such BPA-free
PC-replacement products, chosen for their perceived higher safety, especially for babies, also release other chemicals
that have EA.
Methods: We used two, well-established, mammalian cell-based, assays (MCF-7 and BG1Luc) to assess the EA of
chemicals that leached into over 1000 saline or ethanol extracts of 50 unstressed or stressed (autoclaving,
microwaving, and UV radiation) BPA-free PC-replacement products. An EA antagonist, ICI 182,780, was used to confirm
that agonist activity in leachates was due to chemicals that activated the mammalian estrogen receptor.
Results: Many unstressed and stressed, PC-replacement-products made from acrylic, polystyrene, polyethersulfone, and
Tritan™ resins leached chemicals with EA, including products made for use by babies. Exposure to various forms of UV
radiation often increased the leaching of chemicals with EA. In contrast, some BPA-free PC-replacement products made
from glycol-modified polyethylene terephthalate or cyclic olefin polymer or co-polymer resins did not release chemicals
with detectable EA under any conditions tested.
Conclusions: This hazard assessment survey showed that many BPA-free PC- replacement products still leached
chemicals having significant levels of EA, as did BPA-containing PC counterparts they were meant to replace. That is,
BPA-free did not mean EA-free. However, this study also showed that some PC-replacement products did not leach
chemicals having significant levels of EA. That is, EA-free PC-replacement products could be made in commercial
quantities at prices that compete with PC-replacement products that were not BPA-free. Since plastic products often
have advantages (price, weight, shatter-resistance, etc.) compared to other materials such as steel or glass, it is not
necessary to forgo those advantages to avoid release into foodstuffs or the environment of chemicals having EA that
may have potential adverse effects on our health or the health of future generations.This work was supported by the following NIH/NIEHS grants: R44 ES011469,
01–03 (CZY); 1R43/44 ES014806, 01–03 (CZY); subcontract (CZY, PI) on
an NIH Grant 01–03 43/44ES018083-01 to PlastiPure (DK, SY PIs).Neuroscienc
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