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Trace doping of multiple elements enables stable battery cycling of LiCoO2 at 4.6 V
LiCoO2 is a dominant cathode material for lithium-ion (Li-ion) batteries due to its high volumetric energy density, which could potentially be further improved by charging to high voltages. However, practical adoption of high-voltage charging is hindered by LiCoO2’s structural instability at the deeply delithiated state and the associated safety concerns. Here, we achieve stable cycling of LiCoO2 at 4.6 V (versus Li/Li+) through trace Ti–Mg–Al co-doping. Using state-of-the-art synchrotron X-ray imaging and spectroscopic techniques, we report the incorporation of Mg and Al into the LiCoO2 lattice, which inhibits the undesired phase transition at voltages above 4.5 V. We also show that, even in trace amounts, Ti segregates significantly at grain boundaries and on the surface, modifying the microstructure of the particles while stabilizing the surface oxygen at high voltages. These dopants contribute through different mechanisms and synergistically promote the cycle stability of LiCoO2 at 4.6 V
Fuzzy Gravitons From Uncertain Spacetime
The recently proposed remarkable mechanism explaining ``stringy exclusion
principle" on an Anti de Sitter space is shown to be another beautiful
manifestation of spacetime uncertainty principle in string theory as well as in
M theory. Put in another way, once it is realized that the graviton of a given
angular momentum is represented by a spherical brane, we deduce the maximal
angular momentum directly from either the relation
in M theory or \Delta t\Delta x>\ap in string theory. We also show that the
result of hep-th/0003075 is similar to results on D2-branes in SU(2) WZW model.
Using the dual D2-brane representation of a membrane, we obtain the
quantization condition for the size of the membrane.Comment: 10 pages, harvmac. v2: a ref. and a note added; v3: A remark and one
more ref. adde
Supersymmteric Null-like Holographic Cosmologies
We construct a new class of 1/4-BPS time dependent domain-wall solutions with
null-like metric and dilaton in type II supergravities, which admit a null-like
big bang singularity. Based on the domain-wall/QFT correspondence, these
solutions are dual to 1/4-supersymmetric quantum field theories living on a
boundary cosmological background with time dependent coupling constant and UV
cutoff. In particular we evaluate the holographic function for the
2-dimensional dual field theory living on the corresponding null-like
cosmology. We find that this function runs in accordance with the
-theorem as the boundary universe evolves, this means that the number of
degrees of freedom is divergent at big bang and suggests the possible
resolution of big bang singularity.Comment: 26 pages;v2 references adde
Discrete States in Light-Like Linear Dilaton Background
We study the spectrum of bosonic strings in the light-like linear dilaton
background and find discrete states. These are physical states which exist only
at specific values of momentum. All except one discrete states generate
spacetime symmetries. The exceptional discrete state corresponds to constraints
which are deformations of conservation laws. The constraints resemble those
arising from symmetries, and are equally powerful, suggesting that our notion
of symmetry should be generalized.Comment: Latex, 21 pages, minor change
The clustering of SDSS galaxy groups: mass and color dependence
We use a sample of galaxy groups selected from the SDSS DR 4 with an adaptive
halo-based group finder to probe how the clustering strength of groups depends
on their masses and colors. In particular, we determine the relative biases of
groups of different masses, as well as that of groups with the same mass but
with different colors. In agreement with previous studies, we find that more
massive groups are more strongly clustered, and the inferred mass dependence of
the halo bias is in good agreement with predictions for the CDM
cosmology. Regarding the color dependence, we find that groups with red
centrals are more strongly clustered than groups of the same mass but with blue
centrals. Similar results are obtained when the color of a group is defined to
be the total color of its member galaxies. The color dependence is more
prominent in less massive groups and becomes insignificant in groups with
masses \gta 10^{14}\msunh. We construct a mock galaxy redshift survey
constructed from the large Millenium simulation that is populated with galaxies
according to the semi-analytical model of Croton et al. Applying our group
finder to this mock survey, and analyzing the mock data in exactly the same way
as the true data, we are able to accurately recover the intrinsic mass and
color dependencies of the halo bias in the model. This suggests that our group
finding algorithm and our method of assigning group masses do not induce
spurious mass and/or color dependencies in the group-galaxy correlation
function. The semi-analytical model reveals the same color dependence of the
halo bias as we find in our group catalogue. In halos with M\sim
10^{12}\msunh, though, the strength of the color dependence is much stronger
in the model than in the data.Comment: 16 pages, 14 figures, Accepted for publication in ApJ. In the new
version, we add the bias of the shuffled galaxy sample. The errors are
estimated according to the covariance matrix of the GGCCF, which is then
diagonalize
Biosynthesis of Nanoparticles with Green Tea for Inhibition of β-Amyloid Fibrillation Coupled with Ligands Analysis
Mai Zhang,1 Yan Li,1,2 Chunli Han,3 Shiying Chu,1 Peng Yu,1 Wenbo Cheng1,2 1Mass Spectrometry Application Center, Tianjin Guoke Medical Technology Development Co., Ltd, Tianjin, People’s Republic of China; 2Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences (CAS), Suzhou, People’s Republic of China; 3Mass Spectrometry Application Center, Shandong CAS Intelligent Manufacturing Medical Device Technology Co., Ltd, Zaozhuang, People’s Republic of ChinaCorrespondence: Wenbo Cheng, Email [email protected]: Inhibition of amyloid β protein fragment (Aβ) aggregation is considered to be one of the most effective strategies for the treatment of Alzheimer’s disease. (-)-Epigallocatechin-3-gallate (EGCG) has been found to be effective in this regard; however, owing to its low bioavailability, nanodelivery is recommended for practical applications. Compared to chemical reduction methods, biosynthesis avoids possible biotoxicity and cumbersome preparation processes.Materials and Methods: The interaction between EGCG and Aβ 42 was simulated by molecular docking, and green tea-conjugated gold nanoparticles (GT-Au NPs) and EGCG-Au NPs were synthesized using EGCG-enriched green tea and EGCG solutions, respectively. Surface active molecules of the particles were identified and analyzed using various liquid chromatography-tandem triple quadrupole mass spectrometry methods. ThT fluorescence assay, circular dichroism, and TEM were used to investigate the effect of synthesized particles on the inhibition of Aβ 42 aggregation.Results: EGCG as well as apigenin, quercetin, baicalin, and glutathione were identified as capping ligands stabilized on the surface of GT-Au NPs. They more or less inhibited Aβ 42 aggregation or promoted fibril disaggregation, with EGCG being the most effective, which bound to Aβ 42 through hydrogen bonding, hydrophobic interactions, etc. resulting in 39.86% and 88.50% inhibition of aggregation and disaggregation effects, respectively. EGCG-Au NPs were not as effective as free EGCG, whereas multiple thiols and polyphenols in green tea accelerated and optimized heavy metal detoxification. The synthesized GT-Au NPs conferred the efficacy of diverse ligands to the particles, with inhibition of aggregation and disaggregation effects of 54.69% and 88.75%, respectively, while increasing the yield, enhancing water solubility, and decreasing cost.Conclusion: Biosynthesis of nanoparticles using green tea is a promising simple and economical drug-carrying approach to confer multiple pharmacophore molecules to Au NPs. This could be used to design new drug candidates to treat Alzheimer’s disease.Keywords: gold nanoparticles, green synthesis, (-)-epigallocatechin-3-gallate, liquid chromatography tandem triple quadrupole mass spectrometry, amyloid β protein, green te
Phylogeny of Prokaryotes and Chloroplasts Revealed by a Simple Composition Approach on All Protein Sequences from Complete Genomes Without Sequence Alignment
The complete genomes of living organisms have provided much information on their phylogenetic relationships. Similarly, the complete genomes of chloroplasts have helped to resolve the evolution of this organelle in photosynthetic eukaryotes. In this paper we propose an alternative method of phylogenetic analysis using compositional statistics for all protein sequences from complete genomes. This new method is conceptually simpler than and computationally as fast as the one proposed by Qi et al. (2004b) and Chu et al. (2004). The same data sets used in Qi et al. (2004b) and Chu et al. (2004) are analyzed using the new method. Our distance-based phylogenic tree of the 109 prokaryotes and eukaryotes agrees with the biologists tree of life based on 16S rRNA comparison in a predominant majority of basic branching and most lower taxa. Our phylogenetic analysis also shows that the chloroplast genomes are separated to two major clades corresponding to chlorophytes s.l. and rhodophytes s.l. The interrelationships among the chloroplasts are largely in agreement with the current understanding on chloroplast evolution
Graphene-based modulation-doped superlattice structures
The electronic transport properties of graphene-based superlattice structures
are investigated. A graphene-based modulation-doped superlattice structure
geometry is proposed and consist of periodically arranged alternate layers:
InAs/graphene/GaAs/graphene/GaSb. Undoped graphene/GaAs/graphene structure
displays relatively high conductance and enhanced mobilities at elevated
temperatures unlike modulation-doped superlattice structure more steady and
less sensitive to temperature and robust electrical tunable control on the
screening length scale. Thermionic current density exhibits enhanced behaviour
due to presence of metallic (graphene) mono-layers in superlattice structure.
The proposed superlattice structure might become of great use for new types of
wide-band energy gap quantum devices.Comment: 5 figure
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