14 research outputs found
High-Temperature Stable Anatase Titanium Oxide Nanofibers for Lithium-Ion Battery Anodes
Control
of the crystal structure of electrochemically active materials is
an important approach to fabricating
high-performance electrodes for lithium-ion batteries (LIBs). Here,
we report a methodology for controlling the crystal structure of TiO<sub>2</sub> nanofibers by adding aluminum isopropoxide to a common sol–gel
precursor solution utilized to create TiO<sub>2</sub> nanofibers.
The introduction of aluminum cations impedes the phase transformation
of electrospun TiO<sub>2</sub> nanofibers from the anatase to the
rutile phase, which inevitably occurs in the typical annealing process
utilized for the formation of TiO<sub>2</sub> crystals. As a result,
high-temperature stable anatase TiO<sub>2</sub> nanofibers were created
in which the crystal structure was well-maintained even at high annealing
temperatures of up to 700 °C. Finally, the resulting anatase
TiO<sub>2</sub> nanofibers were utilized to prepare LIB anodes, and
their electrochemical performance was compared to pristine TiO<sub>2</sub> nanofibers that contain both anatase and rutile phases. Compared
to the electrode prepared with pristine TiO<sub>2</sub> nanofibers,
the electrode prepared with anatase TiO<sub>2</sub> nanofibers exhibited
excellent electrochemical performances such as an initial Coulombic
efficiency of 83.9%, a capacity retention of 89.5% after 100 cycles,
and a rate capability of 48.5% at a current density of 10 C (1 C =
200 mA g<sup>–1</sup>)
Nitrogen and Sulfur Co-Doped Carbon Quantum Dot-Engineered TiO<sub>2</sub> Graphene on Carbon Fabric for Photocatalysis Applications
Carbon quantum dots (CQDs) have gained considerable attention
owing
to their unique optoelectronic properties. However, these properties
are quenched upon the aggregation of CQDs in solid-state devices,
limiting their practical applications. Herein, we developed nitrogen
and sulfur co-doped CQDs (NS-CQDs) by in situ carbonization process
and were doped in TiO2-rGO (NS-CQDs-rGO-TiO2) nanocomposites on flexible carbon fabric substrate for efficient
solid-state photocatalytic activity. The NS-CQDs-rGO-TiO2 photocatalyst decorated on flexible carbon fabric substrate facilitates
recycling and thus improves the cycle life. The NS-CQD-rGO-TiO2 nanocomposites exhibited improved photocatalytic degradation
of 98% toward organic pollutants (methylene blue dye) than conventional
aggregation-induced quenching of N-doped CQDs-rGO-TiO2 (67%)
under the same conditions. The enhanced photocatalytic activity of
NS-CQD-rGO-TiO2 nanocomposites is ascribed to NS co-doping,
ultrasmall nanoparticle morphology, mesoporous structure, high surface
area, modified bandgap, the resulting mixed-phase TiO2,
and formation of direct Z-scheme electron transfer under ultraviolet
(UV) irradiation. Thus, this work provides insights into developing
composite materials based on rutile TiO2 for photocatalytic
environmental remediation
RTA-Treated Carbon Fiber/Copper Core/Shell Hybrid for Thermally Conductive Composites
In this paper, we demonstrate a facile
route to produce epoxy/carbon fiber composites providing continuous
heat conduction pathway of Cu with a high degree of crystal perfection
via electroplating, followed by rapid thermal annealing (RTA) treatment
and compression molding. Copper shells on carbon fibers were coated
through electroplating method and post-treated via RTA technique to
reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated
carbon fiber composites with Cu shell of 12.0 vol % prepared via simple
compression molding, revealed 18 times larger thermal conductivity
(47.2 W m<sup>–1</sup> K<sup>–1</sup>) in parallel direction
and 6 times larger thermal conductivity (3.9 W m<sup>–1</sup> K<sup>–1</sup>) in perpendicular direction than epoxy/carbon
fiber composite. Our novel composites with RTA-treated carbon fiber/Cu
core/shell hybrid showed heat conduction behavior of an excellent
polymeric composite thermal conductor with continuous heat conduction
pathway, comparable to theoretical values obtained from Hatta and
Taya model
A Novel, Noncanonical BMP Pathway Modulates Synapse Maturation at the <i>Drosophila</i> Neuromuscular Junction
<div><p>At the <i>Drosophila</i> NMJ, BMP signaling is critical for synapse growth and homeostasis. Signaling by the BMP7 homolog, Gbb, in motor neurons triggers a canonical pathway—which modulates transcription of BMP target genes, and a noncanonical pathway—which connects local BMP/BMP receptor complexes with the cytoskeleton. Here we describe a novel noncanonical BMP pathway characterized by the accumulation of the pathway effector, the phosphorylated Smad (pMad), at synaptic sites. Using genetic epistasis, histology, super resolution microscopy, and electrophysiology approaches we demonstrate that this novel pathway is genetically distinguishable from all other known BMP signaling cascades. This novel pathway does not require Gbb, but depends on presynaptic BMP receptors and specific postsynaptic glutamate receptor subtypes, the type-A receptors. Synaptic pMad is coordinated to BMP’s role in the transcriptional control of target genes by shared pathway components, but it has no role in the regulation of NMJ growth. Instead, selective disruption of presynaptic pMad accumulation reduces the postsynaptic levels of type-A receptors, revealing a positive feedback loop which appears to function to stabilize active type-A receptors at synaptic sites. Thus, BMP pathway may monitor synapse activity then function to adjust synapse growth and maturation during development.</p></div
Synaptic pMad localizes at the active zone.
<p>(A) Diagram of BMP signaling complexes that control the accumulation of nuclear and synaptic pMad. Extracellular BMPs bind to a complex composed of Type I and Type II BMP receptors. The BMP/BMPR complexes are endocytosed and transported to the neuron soma, where they phosphorylate Mad and allow for translocation and accumulation of pMad in the motor neuron nuclei. Synaptic pMad mirrors the active postsynaptic GluRIIA and likely reflects local accumulation of BMP/BMPR complexes. (B-D) 3D-SIM images of NMJ12 boutons from third instar larvae labeled for Brp (green), pMad (red), and Neto (blue). SIM z stack maximum projections are shown in (A–B) and a single z plane is shown in (C). See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005810#pgen.1005810.s001" target="_blank">S1</a> and <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005810#pgen.1005810.s002" target="_blank">S2</a> Movies. (E) High magnification view of a single synapse profile (from panel C). The line indicates the position used for the linescan plotted in panel F. (F) Side view of a surface rendered volume of the synapse shown in panel D. (G) Intensity profile of Neto, pMad and Brp signal along the line drawn in panel E. Linescans like this were performed across many synapses to measure the distance of pMad and Neto from Brp. (H) High magnification view of a z series through a single synapse imaged <i>en face</i>. The z interval was 110nm. Both merged and individual channels are shown. See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005810#pgen.1005810.s003" target="_blank">S3 Movie</a>. Scale bars: 2 μm (B), 1 μm (C), 500 nm (C), 200 nm (E and H).</p
BMP signaling influences iGluR subtypes distribution.
<p>(A-D) Confocal images of NMJ4 boutons from third instar larvae of indicated genotypes labeled for GluRIIA (green), GluRIIB (red), and HRP (blue) (quantified in B-C). The relative intensity of postsynaptic GluRIIA and GluRIIB signals decreases unequally in mutants lacking synaptic pMad, and induces a reduction in IIA/IIB ratio, except for <i>gbb</i> mutants (A-B). Equal reduction of GluRIIA and GluRIIB signals (and thus normal IIA/IIB ratio) is found in larvae with Mav-depleted glia and Put-depleted muscle (C-D). Genotypes: control (<i>w</i><sup><i>1118</i></sup>), <i>gbb</i> (<i>gbb</i><sup><i>1/Df</i></sup>), <i>wit</i> (<i>wit</i><sup><i>A12/Df</i></sup>), <i>mad</i> (<i>mad</i><sup><i>12/Df</i></sup>), <i>imp</i> (<i>imp</i><sup><i>24/70</i></sup>), <i>G>mav</i><sup><i>RNAi</i></sup> <i>(repo-Gal4/UAS-mav</i><sup><i>RNAi</i></sup><i>)</i>, <i>M>put</i><sup><i>RNAi</i></sup> <i>(G14-Gal4/UAS-put</i><sup><i>RNAi</i></sup><i>)</i>. Error bars indicate SEM. ***; p<0.001, **; p<0.01, *; p<0.05. Scale bars: 5 μm and 1 μm (details).</p
Pre- but not postsynaptic expression of Mad-GFP restores synaptic pMad in <i>mad</i> mutants.
<p>(A-D) Confocal images of NMJ4 boutons (A) or ventral ganglia (B) (quantified in C-D) from third instar larvae immunostained for pMad (red), GFP (green), and HRP (blue). (A) Lack of synaptic pMad at <i>mad</i> null mutants is restored by expression of Mad-GFP in motor neurons (<i>mad; N>Mad-GFP</i>). Muscle expression of Mad-GFP (<i>mad; M>Mad-GFP</i>) does not rescue synaptic pMad, even though Mad-GFP accumulates around synaptic boutons. (B) Expression of Mad-GFP in motor neurons of <i>mad</i> mutants leads to elevated nuclear pMad levels. Muscle expression of Mad-GFP does not restore nuclear pMad in <i>mad</i> mutants, except for a small subset of neurons expressing Mad-GFP, which were excluded from quantification. Genotypes: control (<i>w</i><sup><i>1118</i></sup>), <i>mad</i> (<i>mad</i><sup><i>12/Df</i></sup>), <i>mad; N>Mad-GFP (380-Gal4/+; mad</i><sup><i>12/Df</i></sup><i>; UAS-Mad-GFP/+</i>), <i>mad; M>Mad-GFP</i> (<i>mad</i><sup><i>12/Df</i></sup><i>; 24B-Gal4/UAS-Mad-GFP)</i>. Error bars indicate SEM. ***; p<0.001. Scale bars: 10 μm.</p
Excess phosphomimetic Mad reduces postsynaptic GluRIIA.
<p>(A-D) Confocal images of NMJ4 boutons (A, D) and ventral ganglia (B) (quantified in C) from control and third instar larvae with a phosphomimetic Mad variant overexpressed in motor neurons (<i>N>Mad</i><sup><i>S25D</i></sup>). Neuronal expression of Mad<sup>S25D</sup> greatly reduces the accumulation of synaptic pMad (A), but does not affect the nuclear pMad levels (B). Excess presynaptic Mad<sup>S25D</sup> induces a reduction of GluRIIA synaptic signals (green) and an increase of GluRIIB (red) relative to HRP (blue) (D). Scale bars: 10 μm (A and D) and 20 μm (B). (E-I) TEVC recordings from muscle 6, segment A3, of control and third instar larvae with excess presynaptic Mad<sup>S25D</sup> (<i>N>Mad</i><sup><i>S25D</i></sup>) or Mad<sup>S25A</sup> (<i>N>Mad</i><sup><i>S25A</i></sup>). (E) Representative traces of spontaneous junction currents recorded at 0.5 mM Ca<sup>2+</sup>. Summary graphs showing the mean amplitude (F) cumulative probability (G) mean frequency (H) and decay time constant (I) of mEJCs. The mEJC amplitude and decay constant were reduced when Mad<sup>S25D</sup> was overexpressed in the motor neurons. Overexpressing Mad<sup>S25A</sup> did not affect mEJC amplitude or decay constant but showed a reduction in mEJC frequency. Scale bars: 0.5 nA/500 ms (E) and 0.2 nA/25 ms (I). Genotypes: control (<i>380-Gal4/Y</i>), <i>N>Mad</i><sup><i>S25D</i></sup> (<i>380-Gal4/Y; +; UAS-Mad</i><sup><i>S25D</i></sup><i>/+</i>), <i>N>Mad</i><sup><i>S25A</i></sup> (<i>380-Gal4/Y; +; UAS-Mad</i><sup><i>S25A</i></sup><i>/+</i>). Error bars indicate SEM. ***; p<0.001, **; p<0.01, *; p<0.05.</p
Complex genetic control for synaptic pMad accumulation.
<p>(A-C) Confocal images of NMJ4 boutons from larvae of indicated genotypes labeled for pMad (red), HRP (blue) and GluRIIA (green). The accumulation of pMad at <i>gbb</i> mutant NMJs is reduced by postsynaptic <i>GluRIIA</i> knockdown (A) or loss of Wit (B). Knockdown of Mav in the glia or Put in the striated muscle (C) diminished the synaptic pMad accumulation (quantified in D). Genotypes: control (<i>w</i><sup><i>1118</i></sup>), <i>gbb</i> (<i>gbb</i><sup><i>1/2</i></sup>), <i>gbb; IIA</i><sup><i>RNAi</i></sup> (<i>gbb</i><sup><i>1/2</i></sup>; <i>UAS-GluRIIA</i><sup><i>RNAi</i></sup>/<i>24B-Gal4</i>), <i>gbb; wit</i> (<i>gbb</i><sup><i>1/2</i></sup>; <i>wit</i><sup><i>A12/Df</i></sup>), <i>G>mav</i><sup><i>RNAi</i></sup> <i>(repo-Gal4/UAS-mav</i><sup><i>RNAi</i></sup><i>)</i>, <i>gbb; G>mav</i><sup><i>RNAi</i></sup> <i>(gbb</i><sup><i>1/2</i></sup><i>; repo-Gal4/UAS-mav</i><sup><i>RNAi</i></sup>, <i>M>put</i><sup><i>RNAi</i></sup> <i>(G14-Gal4/UAS-put</i><sup><i>RNAi</i></sup><i>)</i>. Error bars indicate SEM. ***; p<0.001, *; p<0.05. Scale bars: 5 μm.</p
Gbb is not required for local pMad accumulation.
<p>(A-B) Confocal images of ventral ganglia (A) and NMJ4 boutons (B) from larvae of indicated genotypes labeled for pMad (red) and Elav (blue) (A), or Brp (green) and HRP (blue) (B). Nuclear pMad is greatly reduced in both <i>gbb</i> and <i>wit</i> mutants, but synaptic pMad appears normal in all <i>gbb</i> null alleles tested. (C) Maximum intensity projection of 3D-SIM images of NMJ12 boutons from third instar <i>gbb</i> mutant larvae labeled for Brp (green), pMad (red), and Neto (blue). Arrows, enlarged active zones; arrowheads, multiple T-bars. (D) A single z plane of the top right bouton in panel (C) magnified. See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005810#pgen.1005810.s004" target="_blank">S4 Movie</a>. SIM z stack maximum projections are shown in (C) and single z plane in (D). (E) High magnification view of a 3D-SIM z series through of an individual <i>gbb</i> mutant synapse imaged <i>en face</i>. See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005810#pgen.1005810.s005" target="_blank">S5 Movie</a>. Scale bars: 20 μm (A), 5 μm (B), 1 μm (C), 500 nm (D), 100 nm (E).</p