Electrochemical Dilatometry Study on Si-Embedded Carbon Nanotube Powder Electrodes

Si-embedded carbon nanotube (Si–C/NT) powders were prepared by dispersing carbon nanotubes (CNTs) and Si in the tetrahydrofuran solution containing poly(vinyl chloride) (PVC) as a dispersion agent, and then carbonizing the PVC. A better cycle performance was observed with the Si–C/NT containing larger void volume. The origin of this feature was addressed by an electrochemical dilatometry study, where it was found that the electrode swelling becomes less significant when the Si–C/NT possesses a larger void space. It is believed that the void space plays a buffering role against the volume expansion of Si, alleviating the breakdown of electrode integrity.This work was supported by KOSEF via the Research Center for Energy Conversion and Storage, and by the Division of Advanced Batteries in the NGE Program (project no. 10016439). We are grateful to Dr. M. Hahn (Paul Scherrer Institute, Switzerland) for his assistance in fabricating the electrochemical dilatometer

Solid-State NMR and Electrochemical Dilatometry Study on Li+ Uptake/Extraction Mechanism in SiO Electrode

This work reports the Li+ uptake/extraction mechanism in silicon monoxide (SiO) as the negative electrode in lithium secondary batteries. A combined study of solid-state 29Si- and 7Li-nuclear magnetic resonance (NMR), electrochemical dilatometry, and charge-discharge cycling consistently demonstrates that the SiO2 domain in SiO irreversibly reacts with Li+ to produce lithium silicates and Li2O in the first discharging period, whereas the elemental Si domain reversibly reacts, delivering the same chargedischarge characteristics to those of conventional amorphous Si electrodes. The volume expansion accompanied by the irreversible reaction is less significant than that caused by the lithiation of Si domain. The postmortem analysis made on cycled electrodes reveals a phase segregation between the lithium silicates/Li2O and lithiated Si phase. It is likely that the lithium silicates/Li2O phase plays a buffering role against the volume change of Si matrix, but the crack formation at the phase boundaries and eventual pulverization are still a problem to be solved.This work was supported by KOSEF via the Research Center for Energy Conversion and Storage. We are grateful to the Daegu Center at the Korea Basic Science Institute for helpful discussions and NMR measurements. We also acknowledge Dr. R. Kötz and Dr. P. Novak (Paul Scherrer Institute, Switzerland) for their assistance in fabricating the electrochemical dilatometer

A CPW-Fed Rectangular Ring Monopole Antenna for WLAN Applications

We present a simple coplanar waveguide- (CPW-) fed rectangular ring monopole antenna designed for dual-band wireless local area network (WLAN) applications. The antenna is based on a simple structure composed of a CPW feed line and a rectangular ring. Dual-band WLAN operation can be achieved by controlling the distance between the rectangular ring and the ground plane of the CPW feed line, as well as the horizontal vertical lengths of the rectangular ring. Simulated and measured data show that the antenna has a compact size of 21.4×59.4 mm2, an impedance bandwidths of 2.21–2.70 GHz and 5.04–6.03 GHz, and a reflection coefficient of less than −10 dB. The antenna also exhibits an almost omnidirectional radiation pattern. This simple compact antenna with favorable frequency characteristics therefore is attractive for applications in dual-band WLAN

SIFamide and SIFamide receptor define a novel neuropeptide signaling to promote sleep in Drosophila

SIFamide receptor (SIFR) is a Drosophila G protein-coupled receptor for the neuropeptide SIFamide (SIFa). Although the sequence and spatial expression of SIFa are evolutionarily conserved among insect species, the physiological function of SIFa/SIFR signaling remains elusive. Here, we provide genetic evidence that SIFa and SIFR promote sleep in Drosophila. Either genetic ablation of SIFa-expressing neurons in the pars intercerebralis (PI) or pan-neuronal depletion of SIFa expression shortened baseline sleep and reduced sleep-bout length, suggesting that it caused sleep fragmentation. Consistently, RNA interference-mediated knockdown of SIFR expression caused short sleep phenotypes as observed in SIFa-ablated or depleted flies. Using a panel of neuron-specific Gal4 drivers, we further mapped SIFR effects to subsets of PI neurons. Taken together, these results reveal a novel physiological role of the neuropeptide SIFa/SIFR pathway to regulate sleep through sleep-promoting neural circuits in the PI of adult fly brains.close1

Highly efficient and robust noble-metal free bifunctional water electrolysis catalyst achieved via complementary charge transfer

The operating principle of conventional water electrolysis using heterogenous catalysts has been primarily focused on the unidirectional charge transfer within the heterostructure. Herein, multidirectional charge transfer concept has been adopted within heterostructured catalysts to develop an efficient and robust bifunctional water electrolysis catalyst, which comprises perovskite oxides (La0.5Sr0.5CoO3-delta, LSC) and potassium ion-bonded MoSe2 (K-MoSe2). The complementary charge transfer from LSC and K to MoSe2 endows MoSe2 with the electron-rich surface and increased electrical conductivity, which improves the hydrogen evolution reaction (HER) kinetics. Excellent oxygen evolution reaction (OER) kinetics of LSC/K-MoSe2 is also achieved, surpassing that of the noble metal (IrO2), attributed to the enhanced adsorption capability of surface-based oxygen intermediates of the heterostructure. Consequently, the water electrolysis efficiency of LSC/K-MoSe2 exceeds the performance of the state-of-the-art Pt/C||IrO2 couple. Furthermore, LSC/K-MoSe2 exhibits remarkable chronopotentiometric stability over 2,500h under a high current density of 100mAcm(-2). While water electrolysis offers a renewable means to obtain H-2, it is necessary to understand the roles adopted by catalytic components. Here, authors explore a heterostructured MoSe2/perovskite oxide catalyst that shows multidirectional charge transfer to boost electrocatalytic water splitting