Neuromagnetic Activation of Primaryand Secondary Somatosensory Cortex Following Tactile-on and Tactile-off Stimulation

Objective Magnetoencephalography (MEG) recordings were performed to investigate the cortical activation following tactile-on and tactile-off stimulation. Methods We used a 306-ch whole-head MEG system and a tactile stimulator driven by a piezoelectric actuator. Tactile stimuli were applied to the tip of right index finger. The interstimulus interval was set at 2000 ms, which included a constant stimulus of 1000 ms duration. Results Prominent somatosensory evoked magnetic fields were recorded from the contralateral hemisphere at 57.5 ms and 133.0 ms after the onset of tactile-on stimulation and at 58.2 ms and 138.5 ms after the onset of tactile-off stimulation. All corresponding equivalent current dipoles (ECDs) were located in the primary somatosensory cortex (SI). Moreover, long-latency responses (168.7 ms after tactile-on stimulation, 169.8 ms after tactile-off stimulation) were detected from the ipsilateral hemisphere. The ECDs of these signals were identified in the secondary somatosensory cortex (SII). Conclusions The somatosensory evoked magnetic fields waveforms elicited by the two tactile stimuli (tactile-on and tactile-off stimuli) with a mechanical stimulator were strikingly similar. These mechanical stimuli elicited both contralateral SI and ipsilateral SII activities. Significance Tactile stimulation with a mechanical stimulator provides new possibilities for experimental designs in studies of the human mechanoreceptor system

Structural and dynamic behavior of lithium iron polysulfide Li₈FeS₅ during charge–discharge cycling

Lithium sulfide (Li₂S) is one of the promising positive electrode materials for next-generation rechargeable lithium batteries. To improve the electrochemical performance of electronically resistive Li₂S, a Fe-doped Li₂S-based positive electrode material (Li₈FeS₅) has been recently designed and found to exhibit excellent discharge capacity close to 800 mAh g⁻¹. In the present study, we investigate the structural and dynamic behavior of Li₈FeS₅ during charge–discharge cycling. In Li₈FeS₅, Fe ions are incorporated into the Li₂S framework structure. The Li₂S-based structure is found to transform to an amorphous phase during the charge process. The delithiation-induced amorphization is associated with the formation of S-S polysulfide bonds, indicating charge compensation by S ions. The crystalline to non-crystalline structural transformation is reversible, but Li ions are extracted from the material via a two-phase reaction, although they are inserted via a single-phase process. These results indicate that the delithiation/lithiation mechanism is neither a topotactic extraction/insertion nor a conversion-type reaction. Moreover, the activation energies for Li ion diffusion in the pristine, delithiated, and lithiated materials are estimated to be in the 0.30–0.37 eV range, which corresponds to the energy barriers for local hopping of Li ions along the Li sublattice in the Li₂S framework

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Thermal radiation and direct photon production measurements with dielectrons in Pb–Pb and pp collisions

The latest ALICE results on dielectron measurements in Pb–Pb collisions at √SNN = 5.02 TeV, and in minimum-bias (MB) and high-multiplicity (HM) pp collisions at √S = 13 TeV with LHC Run 2 data are reported. The results are compared to the predictions of dielectron yields from known hadronic sources and thermal radiation from the medium. The contribution of virtual direct photons is extracted from the data by fitting the measured invariant mass distributions. We present the direct to inclusive photon ratio, as well as the direct photon yield in both pp and central Pb–Pb collisions

Electromagnetic radiation in pp and Pb--Pb collisions with dielectrons in ALICE

The latest ALICE results on low $_{{\rm T}}$ direct photon measurements via the virtual photon method are presented. Direct photons are measured in Pb–Pb collisions at $\sqrt{s}_{{\rm NN}}$ = 5.02 TeV, and in minimum-bias (MB) and high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV with LHC Run 2 data. The virtual direct-photon signal is extracted from the dielectron mass spectra. Direct photon spectrum in Pb–Pb collisions is measured in the range 1 < $_{{\rm T}}$ < 5 GeV/ and compared with theoretical predictions. In pp collisions, such measurement in minimum-bias events serves as a baseline for Pb–Pb collisions and a fundamental test for perturbative QCD (pQCD) calculations, while studies in high charged-particle multiplicity events allow one to search for thermal radiation in small colliding systems. Direct photon spectra in pp collisions for both event multiplicity classes are measured in the range 1 < $_{{\rm T}}$ < 6 GeV/. The MB result was compared with NLO pQCD calculations and the viscous hydrodynamical model. Finally, the first result with the Run 3 pp data at $\sqrt{s}$ = 13.6 TeV, using the upgraded ALICE detector to disentangle the different dielectron sources, is reported

Capacity fading mechanism of conversion-type FeF₃ electrode: Investigation by electrochemical operando nuclear magnetic resonance spectroscopy

FeF₃ has attracted considerable attention as a positive electrode material for next-generation rechargeable lithium ion batteries, because of its low cost, low risk, and high energy density, which facilitate a conversion-type lithiation/delithiation reaction. However, the conversion reaction of the FeF₃ electrode is known to suffer from capacity fading during repeated discharge–charge cycles. Herein, we find an interesting correlation between capacity fading behavior and spectral evolutions in electrochemical operando nuclear magnetic resonance (NMR) measurements. The operando ⁷Li NMR spectra demonstrate the reversible formation of metallic Fe by the conversion process during the early discharge–charge cycles. However, it is gradually suppressed after repeated cycles. Moreover, LiF is augmented at the fully charged states, indicating that FeF₃ is no longer recovered after repeated cycles. The active material can converge into FeF₂ and LiF in the degraded electrode. Another factor associated with capacity degradation is the electrolyte decomposition occurring at high voltages, which results in a resistive film coating the electrode surface. We therefore conclude that the film accumulation on repeated discharging inhibits the conversion reaction to metallic Fe and LiF, leading to a characteristic capacity fading behavior of FeF₃

Reversible lithium insertion and conversion process of amorphous VS₄ revealed by operando electrochemical NMR spectroscopy

Due to the high theoretical capacity, VS₄ is a promising electrode material for next-generation rechargeable batteries. In this study, the lithium insertion and conversion process of amorphous VS₄ was investigated using operando electrochemical nuclear magnetic resonance (NMR) spectroscopy. Amorphous VS₄ has a chain-like structure similar to that of crystalline VS₄. The chain structure was drastically changed to the [VS₄]³⁻ tetrahedral structure by lithium insertion up to the Li₃VS₄ composition. The lithium insertion into the [VS₄]³⁻-based structure proceeded further up to the Li₆VS₄ composition, with charge compensation by the reduction of the V valency. Finally, the conversion reaction from amorphous Li₆VS₄ to metallic V and 4Li₂S was observed. The structural reversibility of amorphous VS₄ was confirmed after the delithiation. It is worth mentioning that the delithiation process from the conversion products was different from the lithiation, resulting in a relatively large voltage hysteresis. Broadly, this study demonstrates that the operando electrochemical NMR technique is a useful tool for investigating the complex reaction system of non-crystalline battery materials