644 research outputs found
A carbon nanotubes-silicon nanoparticles network for high performance lithium rechargeable battery anodes
As an effort to address the chronic capacity fading of Si anodes and thus achieve their robust cycling performance, herein, we develop a unique electrode in which silicon nanoparticles are embedded in the carbon nanotubes network. Utilizing robust contacts between silicon nanoparticles and carbon nanotubes, the composite electrodes exhibit excellent electrochemical performance : 95.5% capacity retention after 140 cycles as well as rate capability such that at the C-rate increase from 0.1C to 1C to 10C, the specific capacities of 850, 698, and 312 mAh/g are obtained, respectively. The present investigation suggests a useful design principle for silicon as well as other high capacity alloying electrodes that undergo large volume expansions during battery operations.
Two distinct red giant branch populations in the globular cluster NGC 2419 as tracers of a merger event in the Milky Way
Recent spectroscopic observations of the outer halo globular cluster (GC) NGC
2419 show that it is unique among GCs, in terms of chemical abundance patterns,
and some suggest that it was originated in the nucleus of a dwarf galaxy. Here
we show, from the Subaru narrow-band photometry employing a calcium filter,
that the red giant-branch (RGB) of this GC is split into two distinct
subpopulations. Comparison with spectroscopy has confirmed that the redder RGB
stars in the [=(Ca] index are enhanced in [Ca/H] by 0.2
dex compared to the bluer RGB stars. Our population model further indicates
that the calcium-rich second generation stars are also enhanced in helium
abundance by a large amount (Y = 0.19). Our photometry, together with
the results for other massive GCs (e.g., Cen, M22, and NGC 1851),
suggests that the discrete distribution of RGB stars in the index might be
a universal characteristic of this growing group of peculiar GCs. The planned
narrow-band calcium photometry for the Local Group dwarf galaxies would help to
establish an empirical connection between these GCs and the primordial building
blocks in the hierarchical merging paradigm of galaxy formation.Comment: 4 pages, 4 figures, 1 table, accepted for the publication in ApJ
Promising And Anomalous Structural And Electrochemical Properties Of Polyanionic Phosphates In Sodium Ion Batteries
This work presents a recent progress on the polyanionic phosphate family that functions as cathode materials in sodium ion batteries (SIBs). Firstly, this study will cover vanadium-containing frameworks that show very stable voltage curves in different potential regimes with advantageous behaviors such as single flat voltage plateaus and the presence of intermediate phases that are beneficial for cell kinetics. In the second part of our study, some anomalous manganese activation in the SIBs pyrophosphate family that overcomes the chronic Jahn-Teller distortion, in contrast to the Li counterparts will be introduced. By employing density functional theory (DFT) calculations, it is figured out that such anomalous activation is originated from its unique crystal structure where corner-sharing is the main structural change during the phase transformation in the charge-discharge processes. In addition, unique SIBs properties will be compared to the lithium ion batteries (LIBs) analogues even for the same chemical formulae.qscienc
Aluminum nitride waveguide beam splitters for integrated quantum photonic circuits
We demonstrate integrated photonic circuits for quantum devices using
sputtered polycrystalline aluminum nitride (AlN) on insulator. The on-chip AlN
waveguide directional couplers, which are one of the most important components
in quantum photonics, are fabricated and show the output power splitting ratios
from 50:50 to 99:1. The polarization beam splitters with an extinction ratio of
more than 10 dB are also realized from the AlN directional couplers. Using the
fabricated AlN waveguide beam splitters, we observe the Hong-Ou-Mandel
interference with a visibility of 91.7 +(-) 5.66 %.Comment: 9 pages, 4 figure
Gastroprotective effects of the isopropanol extract of Artemisia princeps and its gastroretentive floating tablets on gastric mucosal injury
In this study, we investigated the gastroprotective effect of an isopropanol extract from the aerial parts of Artemisia princeps (IPAP) and developed a gastroretentive floating tablet of IPAP (IPAP-FR) for maximized local gastroprotective effects. Pre-treatment with IPAP ameliorated the gastric mucosal hemorrhagic lesions in ethanol/HCl- or indomethacin-treated rats. IPAP decreased mucosal hemorrhage of gastric ulcers induced by ethanol or indomethacin plus pyloric ligation in rats. The optimized floating tablet, IPAP-FR, floated on medium surface with more sustained eupatilin release compared to the non-floating control tablet. X-ray photographs in beagle dogs showed that IPAP-FR was retained for >2 h in the stomach. In the ethanol-induced gastric ulcer rat model, the gastric hemorrhagic lesion was improved more substantially with IPAP-FR compared to the non-floating control tablet. Based on these data, our data suggest that IPAP-FR has an improved therapeutic potential for the treatment of gastric ulcer
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