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 TiO₂ nanofibers by adding aluminum isopropoxide to a common sol–gel precursor solution utilized to create TiO₂ nanofibers. The introduction of aluminum cations impedes the phase transformation of electrospun TiO₂ nanofibers from the anatase to the rutile phase, which inevitably occurs in the typical annealing process utilized for the formation of TiO₂ crystals. As a result, high-temperature stable anatase TiO₂ 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 TiO₂ nanofibers were utilized to prepare LIB anodes, and their electrochemical performance was compared to pristine TiO₂ nanofibers that contain both anatase and rutile phases. Compared to the electrode prepared with pristine TiO₂ nanofibers, the electrode prepared with anatase TiO₂ 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^–1)

Nitrogen and Sulfur Co-Doped Carbon Quantum Dot-Engineered TiO₂ 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^–1 K^–1) in parallel direction and 6 times larger thermal conductivity (3.9 W m^–1 K^–1) 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>^<i>1118</i>), <i>gbb</i> (<i>gbb</i>^<i>1/Df</i>), <i>wit</i> (<i>wit</i>^{<i>A12/Df</i>}), <i>mad</i> (<i>mad</i>^<i>12/Df</i>), <i>imp</i> (<i>imp</i>^<i>24/70</i>), <i>G>mav</i>^<i>RNAi</i> <i>(repo-Gal4/UAS-mav</i>^<i>RNAi</i><i>)</i>, <i>M>put</i>^<i>RNAi</i> <i>(G14-Gal4/UAS-put</i>^<i>RNAi</i><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>^<i>1118</i>), <i>mad</i> (<i>mad</i>^<i>12/Df</i>), <i>mad; N>Mad-GFP (380-Gal4/+; mad</i>^<i>12/Df</i><i>; UAS-Mad-GFP/+</i>), <i>mad; M>Mad-GFP</i> (<i>mad</i>^<i>12/Df</i><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>^<i>S25D</i>). Neuronal expression of Mad^S25D greatly reduces the accumulation of synaptic pMad (A), but does not affect the nuclear pMad levels (B). Excess presynaptic Mad^S25D 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^S25D (<i>N>Mad</i>^<i>S25D</i>) or Mad^S25A (<i>N>Mad</i>^<i>S25A</i>). (E) Representative traces of spontaneous junction currents recorded at 0.5 mM Ca²⁺. 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^S25D was overexpressed in the motor neurons. Overexpressing Mad^S25A 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>^<i>S25D</i> (<i>380-Gal4/Y; +; UAS-Mad</i>^<i>S25D</i><i>/+</i>), <i>N>Mad</i>^<i>S25A</i> (<i>380-Gal4/Y; +; UAS-Mad</i>^<i>S25A</i><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>^<i>1118</i>), <i>gbb</i> (<i>gbb</i>^<i>1/2</i>), <i>gbb; IIA</i>^<i>RNAi</i> (<i>gbb</i>^<i>1/2</i>; <i>UAS-GluRIIA</i>^<i>RNAi</i>/<i>24B-Gal4</i>), <i>gbb; wit</i> (<i>gbb</i>^<i>1/2</i>; <i>wit</i>^{<i>A12/Df</i>}), <i>G>mav</i>^<i>RNAi</i> <i>(repo-Gal4/UAS-mav</i>^<i>RNAi</i><i>)</i>, <i>gbb; G>mav</i>^<i>RNAi</i> <i>(gbb</i>^<i>1/2</i><i>; repo-Gal4/UAS-mav</i>^<i>RNAi</i>, <i>M>put</i>^<i>RNAi</i> <i>(G14-Gal4/UAS-put</i>^<i>RNAi</i><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