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Multi-electron redox phenazine for ready-to-charge organic batteries
Lee, M.,Hong, J.,Lee, B.,Ku, K.,Lee, S.,Park, C.,Kang, K. unknown 2017 Green Chemistry Vol. No.
<P>Organic redox compounds represent an emerging class of cathode materials in rechargeable batteries for low-cost and sustainable energy storage. However, the low operating voltage (<3 V) and necessity of using lithium-containing anodes have significantly limited their practical applicability to battery systems. Here, we introduce a new class of p-type organic redox centers based on N,N'-substituted phenazine (NSPZ) to build ready-to-charge organic batteries. In the absence of lithium-containing anodes, NSPZ cathodes facilitate reversible two-electron transfer at 3.7 and 3.1 V accompanying anion association, which results in a specific energy of 622 Wh kg(-1) in dual-ion batteries.</P>
Insight from early coral-stromatoporoid intergrowth, Late Ordovician of China
Lee, M.,Elias, R.J.,Choh, S.J.,Lee, D.J. Elsevier 2016 Palaeogeography, palaeoclimatology, palaeoecology Vol.463 No.-
One of the earliest endosymbiotic associations with stromatoporoids occurs in the Late Ordovician Xiazhen Formation of southeastern China. Bajgolia, an auloporid tabulate coral characterized by dichotomous branching due to longitudinal fission, is represented by free-living as well as endobiontic forms in various lithofacies representing a wide range of environments. Only two of 11 stromatoporoid genera (Clathrodictyon and Ecclimadictyon) hosted Bajgolia, mainly in reef and related facies. Bajgolia-stromatoporoid associations occur occasionally in the lower part of the formation, but eventually become persistent in the upper part. Such associations were initiated by larval settlement of the coral on the growth surface of the stromatoporoid. Growth of Bajgolia usually kept pace with its host, but the coral's ability to change growth direction and grow faster prevented its envelopment and termination by the stromatoporoid, allowing the establishment and recurrence of an ongoing endosymbiotic relationship between the two organisms. Endobiontic Bajgolia was able to survive with its corallites protruding from the host; in some cases, the growth form of the stromatoporoid changed in response to the coral. The relationships between Bajgolia and stromatoporoids were probably commensal, but there is also evidence for mutualism and/or parasitism. Bajgolia-stromatoporoid associations represent an important stage in the development of complex ecological relationships and community structure, prior to the common and widespread syringoporid (''caunopore tubes'')-stromatoporoid associations in the Siluro-Devonian.
Lee, M.,Hwang, Y.K.,Chang, J.S.,Chae, H.J.,Hwang, D.W. Elsevier 2016 CATALYSIS COMMUNICATIONS - Vol.84 No.-
A Ni-Cu-SiO<SUB>2</SUB> nanocomposite was studied as a catalyst for vapor-phase glycerol hydrogenation to produce 1,2-propanediol (1,2-PDO). Substitution of a small amount (3wt%) of Ni for Cu is beneficial for decreasing the Cu particle size, which would be advantageous for attaining higher 1,2-PDO selectivity and higher glycerol conversion. 92% 1,2-PDO selectivity and 100% glycerol conversion were obtained at 220<SUP>o</SUP>C, 30bar, and a weight hourly space velocity of 0.5h<SUP>-1</SUP> over Ni(3)-Cu(77)-SiO<SUB>2,</SUB> which were nearly identical to those obtained with the conventional copper chromite (CuO-Cr<SUB>2</SUB>O<SUB>3</SUB>) catalyst. Therefore, the present Ni(3)-Cu(77)-SiO<SUB>2</SUB> nanocomposite is regarded as a green and efficient catalyst for glycerol conversion into more valuable 1,2-PDO.
Anatase TiO<sub>2</sub> nanosheets with surface acid sites for Friedel-Crafts alkylation
Lee, M.,Seo, Y.,Shin, H.S.,Jo, C.,Ryoo, R. Elsevier 2016 Microporous and mesoporous materials Vol.222 No.-
<P>The solvothermal synthesis route to mesoporous TiO2 using a vinylphenol polymer structure-directing agent (SDA) was optimized to provide a high yield of bilayer nanosheets. The resultant TiO2 material exhibited a high BET area of 420 m(2) g(-1) after the removal of SDA. Structural analysis of the nanosheets was carried out using powder X-ray diffraction, high resolution-transmission electron microscopy, Raman spectroscopy and solid-state NMR. The results indicated that the TiO2 material consisted mainly of the bilayer nanosheets with (010) facet-dominant anatase crystal structure. The thickness of the nanosheet was 0.75 nm, corresponding to two unit-cell parameters along the b-axis in the anatase crystal system. More than 10% of the surface Ti atoms were terminated with bridging O-H groups and coordinatively unsaturated Ti atoms, which acted as Bronsted and Lewis acid sites. Accordingly, the anatase nanosheets exhibited catalytic performance in the liquid-phase Friedel Crafts alkylation of aromatic compounds. (C) 2015 Elsevier Inc. All rights reserved.</P>
Adipose-derived stem cell exosomes alleviate pathology of amyotrophic lateral sclerosis in vitro
Lee, M.,Ban, J.J.,Kim, K.Y.,Jeon, G.S.,Im, W.,Sung, J.J.,Kim, M. Academic Press 2016 Biochemical and biophysical research communication Vol.479 No.3
Amyotrophic lateral sclerosis (ALS) is a degenerative disorder that involves the death of motor neurons in the cortex, brain stem, and spinal cord. Adipose-derived stem cells (ADSCs) are considered as a perspective remedy for therapy of neurodegenerative diseases including ALS. Stem cells secrete various factors which can modulate a hostile environment, called paracrine effect. Exosomes are small extracellular vesicles containing cell derived factors and mediate paracrine effect of cells. Thus, exosomes from ADSCs (ADSC-exo) can be a potential candidate of therapeutic effects of stem cells. To investigate the effect of ADSC-exo on the cellular phenotypes of ALS, we used neuronal stem cells (NSCs), which can be differentiated into neuronal cells, isolated from wild type or G93A ALS mice model. ADSC-exo was treated to neuronal cells from G93A ALS mice model. Immunocytochemistry and dot-blot assay result showed that ADSC-exo alleviated aggregation of superoxide dismutase 1 (SOD1). Reduction of cytosolic SOD1 level by ADSC-exo was also confirmed by western blot. Mitochondria display various abnormalities in ALS and the decrease of phospho-CREB and PGC-1α were observed in the G93A cells. ADSC-exo treatment showed normalization of phospho-CREB/CREB ratio and PGC-1α expression level. Our results suggest that ADSC-exo modulates cellular phenotypes of ALS including SOD-1 aggregation and mitochondrial dysfunction, and can be a therapeutic candidate for ALS.
The barycenter property for robust and generic diffeomorphisms
Springer Business + Business Media 2016 Acta mathematica Sinica. English series Vol.32 No.8
<P>Let f: M (d) -> M (d) (d a parts per thousand yen 2) be a diffeomorphism on a compact C (a) manifold on M. If a diffeomorphism f belongs to the C (1)-interior of the set of all diffeomorphisms having the barycenter property, then f is Omega-stable. Moreover, if a generic diffeomorphism f has the barycenter property, then f is Omega-stable. We also apply our results to volume preserving diffeomorphisms.</P>
Conformational sampling of metastable states: Tq-REM as a novel replica exchange method
Lee, M.,Yoon, J.,Jang, S.,Shin, S. Royal Society of Chemistry 2017 Physical chemistry chemical physics Vol.19 No.7
<P>Although the replica exchange methods (REMs) were developed as efficient conformational sampling methods for bio-molecular simulations, their application to very large bio-systems is somewhat limited. We propose a new replica exchange scheme (Tq-REM) created by combining the conventional temperature-REM (T-REM) and one of the Hamiltonian-REMs, q-REM, using the effective potential with reduced barriers. In the proposed Tq-REM scheme, high temperature replicas in T-REM are substituted with q-replicas. This combined scheme is expected to exploit advantages of the T-REM and q-REM resulting in improved sampling efficiency while minimizing the drawbacks of both approaches. We investigated the performance of Tq-REM compared with T-REM by performing all-atom MD simulations on Met-enkephalin, (AAQAA) 3, and Trpzip2. It was found that convergence of the free energy surfaces was improved by Tq-REM over the conventional T-REM. In particular, the trajectories of Tq-REM were able to sample the relevant conformations for all of the metastable folding intermediates, while some of the local minimum structures are poorly represented by T-REM. The results of the present study suggest that Tq-REM can provide useful tools to investigate systems where metastable states play important roles.</P>