High Electrochemical Performance Silicon Thin-Film Free-Standing Electrodes Based on Buckypaper for Flexible Lithium-Ion Batteries

Recently, applications for lithium-ion batteries (LIBs) have expanded to include electric vehicles and electric energy storage systems, extending beyond power sources for portable electronic devices. The power sources of these flexible electronic devices require the creation of thin, light, and flexible power supply devices such as flexile electrolytes/insulators, electrode materials, current collectors, and batteries that play an important role in packaging. Demand will require the progress of modern electrode materials with high capacity, rate capability, cycle stability, electrical conductivity, and mechanical flexibility for the time to come. The integration of high electrical conductivity and flexible buckypaper (oxidized Multi-walled carbon nanotubes (MWCNTs) film) and high theoretical capacity silicon materials are effective for obtaining superior high-energy-density and flexible electrode materials. Therefore, this study focuses on improving the high-capacity, capability-cycling stability of the thin-film Si buckypaper free-standing electrodes for lightweight and flexible energy-supply devices. First, buckypaper (oxidized MWCNTs) was prepared by assembling a free stand-alone electrode, and electrical conductivity tests confirmed that the buckypaper has sufficient electrical conductivity (10⁻⁴(S m⁻¹) in LIBs) to operate simultaneously with a current collector. Subsequently, silicon was deposited on the buckypaper via magnetron sputtering. Next, the thin-film Si buckypaper freestanding electrodes were heat-treated at 600 °C in a vacuum, which improved their electrochemical performance significantly. Electrochemical results demonstrated that the electrode capacity can be increased by 27/26 and 95/93 μAh in unheated and heated buckypaper current collectors, respectively. The measured discharge/charge capacities of the USi_HBP electrode were 108/106 μAh after 100 cycles, corresponding to a Coulombic efficiency of 98.1%, whereas the HSi_HBP electrode indicated a discharge/charge capacity of 193/192 μAh at the 100th cycle, corresponding to a capacity retention of 99.5%. In particular, the HSi_HBP electrode can decrease the capacity by less than 1.5% compared with the value of the first cycle after 100 cycles, demonstrating excellent electrochemical stability.     

Expression of prestin mRNA in the organotypic culture of rat cochlea

To quantitate in absolute terms the prestin mRNA levels in the explant culture of rat cochlea, we used competitive RT-PCR with a synthetic internal cRNA standard. Prestin gene expression was found at levels of 100 fg specific mRNA/microg total RNA on postnatal day 3, which corresponds to about 300 copies per outer hair cell (OHC) and is indicative of an intermediate level of expression. Two days of culturing resulted in an increase of prestin mRNA levels and in the formation of an apical-basal gradient (p<0.001). To elucidate the variations the prestin mRNA levels undergo as a result of damage to the organ of Corti, we exposed the explant cultures to ischemia and hypoxia. While total RNA was observed to remain unchanged, the numbers of OHCs and the prestin mRNA levels were found to decrease by about 20% and 35%, respectively, compared to normoxia. In conclusion, we showed that the prestin mRNA levels during in vitro development increase and form an apical-basal gradient within 2 days in culture, similar to the postnatal in vivo development. Hypoxia and ischemia result in a decrease of the prestin mRNA level in parallel with OHC loss. The prestin mRNA level can therefore be used as marker of damage to or loss of OHCs.     

Effect of different surface treatments on the repair strength of a nanofilled resin-based composite

The purpose of our study was to re-evaluate the effects of surface treatment on the bond strength of repaired methacrylate-based dental composite materials including nanofillers (Ceram X, Dentsply). The microtensile bond strengths were measured before or after thermo-mechanical fatigue simulation. The treatments were as follows: (1)No treatment (negative control), (2)Bonding agent, (3) Acetone, (4)Acetone+Bonding agent, (5)Silane, (6)Silane+Bonding agent. In the digitized SEM image of the polished aged specimens without any surface treatment, the percentage of the visible fillers relative to the whole image was calculated. Before and after fatigue, no significant differences could be observed among the different pretreatment groups. Fatigue increased the microtensile strength values of Acetone and Silane groups. The digitized SEM image reveals that 11.5% of the exposed surface could be identified as uncovered filler surface. None of surface treatments (acetone, silane and bonding agent) contributed to increase the tensile strength of repaired composite samples including nanofillers.     

Coenzyme Q10 does not protect cochlear hair cells from death in the ischemic organotypic culture

OBJECTIVE: To evaluate in vitro the effect of coenzyme Q10 (CoQ(10)) on ischemia-induced hair cell death. STUDY DESIGN: Organotypic cochlear cultures of newborn rats were subjected to ischemia with and without CoQ(10). RESULTS: Addition of CoQ(10) has not prevented HC loss. CONCLUSION: CoQ(10) seems to protect against only certain modes of cell death.     

Recombinant human erythropoietin prevents ischemia-induced apoptosis and necrosis in explant cultures of the rat organ of Corti

This study was designed to evaluate the effect of recombinant human erythropoietin (rhEPO), insulin-like growth factor-1 (rhIGF-1) and epidermal growth factor (rhEGF) on ischemia-induced hair cell loss in an organotypic cochlea culture. The apical, middle and basal parts of the organs of Corti (newborn rat, postnatal days 3-5) were exposed to ischemia (3.5 h) in glucose-free artificial perilymph (pO2 10-20 mmHg) with or without growth factors. Controls were exposed to normoxia. Twenty-four hours after the onset of ischemia, the cultures were stained using tetramethyl rhodamine isothiocyanate (TRITC) phalloidin (hair cells), propidium iodide (membrane integrity) and apoptosis detection kit (DNA-fragmentation). Ischemia (3.5 h) induced a hair cell loss of 20 and 40% in the middle and basal cochlear parts, respectively, and an increase of the numbers of PI-stained and DNA-fragmented nuclei (controls 0-1, ischemia 4-7 nuclei/100 microm). The basal part was more affected than the apical one. rhEPO and rhIGF-1 significantly attenuated the ischemia-induced hair cell loss by reducing processes involved in apoptosis and necrosis. rhEPO has been in clinical use for more than a decade and found to be well tolerated. Therefore, rhEPO could be an effective drug for the prevention of hearing loss via a hair cell protective mechanism.     

High potassium concentrations protect inner and outer hair cells in the newborn rat culture from ischemia-induced damage

Several studies indicate that an increase in the extracellular potassium (K+) concentration is a factor exerting a damaging effect on cochlear hair cells (HCs). The present study was designed to examine the effects of high extracellular K+ concentrations on the HCs under normoxic and ischemic conditions. Organotypic cultures of the organ of Corti of newborn rats were exposed to normoxia and ischemia at K+ concentrations of 5-70 mM in artificial perilymph for 3-4h. The number of IHCs and OHCs in the apical, medial and basal parts of the cochlea were counted 24h later. The work resulted in two main findings: (1) extracellular K+ concentrations of 30-70 mM had no effect on the HCs under normoxic conditions; (2) under ischemic conditions, a clear HC loss, mainly in the medial and basal cochlear parts, was observed at 5 mM K+ as previously reported. In contrast, a high extracellular K+ concentration strongly attenuated the HC loss. This effect nearly completely disappeared by the addition of both eosin, an inhibitor of the plasma membrane calcium ATPase (PMCA), and linopirdine, an inhibitor of the KCNQ4 channel, indicating that a normal activity of the PMCA and the KCNQ4 channels are key factors for HC survival under ischemia and depolarizing conditions.