Conversion mechanism of NiCo2Se4 nanotube sphere anodes for potassium-ion batteries

Given the abundance of potassium resources, potassium-ion batteries are considered a low-cost alternative to lithium-ion types. However, their electrochemical performance remains rather unsatisfactory because potassium ions have sluggish kinetics and large ionic radius. In this study, NiCo2Se4 nanotube spheres are synthesized as efficient potassium storage hosts via a facile two-step hydrothermal process. The rationally designed electrode has various ameliorating morphological and functional features, including the following: (i) A hollow structure allows for relief of the volume expansion while offering an excellent electrochemical reactivity to accelerate the conversion kinetics; (ii) a high electrical conductivity for enhanced electron transfer; and (iii) myriad vacancies to supply active sites for electrochemical reactions. As such, the electrode delivers an initial reversible capacity of 458.1 mAh g−1 and retains 346.6 mAh g−1 after 300 cycles at 0.03 A g−1. The electrode sustains a high capacity of 101.4 mAh g−1 even at a high current density of 5 A g−1 and outperforms the majority of state-of-the-art anodes in terms of both cyclic capacity and rate capability, especially at above 1.0 A g−1. This study not only proves bimetallic selenides are promising candidates for potassium storage devices but also offers new insight into the rational design of electrode materials for high-rate potassium-ion batteries

Strong coordination interaction in amorphous Sn-Ti-ethylene glycol compound for stable Li-ion storage

Sn has been considered one of the most promising metallic anode materials for lithium-ion batteries (LIBs) because of its high specific capacity. Herein, we report a novel amorphous tin-titanium-ethylene glycol (Sn-Ti-EG) bimetal organic compound as an anode for LIBs. The Sn-Ti-EG electrode exhibits exceptional cyclic stability with high Li-ion storage capacity. Even after 700 cycles at a current density of 1.0 A g−1, the anode maintains a capacity of 345 mAh g−1. The unique bimetal organic structure of the Sn-Ti-EG anode and the strong coordination interaction between Sn/Ti and O within the framework effectively suppress the aggregation of Sn atoms, eliminating the usual pulverization of bulk Sn through volume expansion. Furthermore, the Sn M-edge of the X-ray absorption near-edge structure spectra obtained using soft X-ray absorption spectroscopy signifies the conversion of Sn2+ ions into Sn0 during the initial lithiation process, which is reversible upon delithiation. These findings reveal that Sn is one of the most active components that account for the excellent electrochemical performance of the Sn-Ti-EG electrode, whereas Ti has no practical contribution to the capacity of the electrode. The reversible formation of organic functional groups on the solid electrolyte interphase is also partly responsible for its cyclic stability

The mosaic genome of indigenous African cattle as a unique genetic resource for African pastoralism

© 2020, The Author(s), under exclusive licence to Springer Nature America, Inc. Cattle pastoralism plays a central role in human livelihood in Africa. However, the genetic history of its success remains unknown. Here, through whole-genome sequence analysis of 172 indigenous African cattle from 16 breeds representative of the main cattle groups, we identify a major taurine × indicine cattle admixture event dated to circa 750–1,050 yr ago, which has shaped the genome of today’s cattle in the Horn of Africa. We identify 16 loci linked to African environmental adaptations across crossbred animals showing an excess of taurine or indicine ancestry. These include immune-, heat-tolerance- and reproduction-related genes. Moreover, we identify one highly divergent locus in African taurine cattle, which is putatively linked to trypanotolerance and present in crossbred cattle living in trypanosomosis-infested areas. Our findings indicate that a combination of past taurine and recent indicine admixture-derived genetic resources is at the root of the present success of African pastoralism

A Novel In Vitro Sensing Configuration for Retinal Physiology Analysis of a Sub-Retinal Prosthesis

This paper presents a novel sensing configuration for retinal physiology analysis, using two microelectrode arrays (MEAs). In order to investigate an optimized stimulation protocol for a sub-retinal prosthesis, retinal photoreceptor cells are stimulated, and the response of retinal ganglion cells is recorded in an in vitro environment. For photoreceptor cell stimulation, a polyimide-substrate MEA is developed, using the microelectromechanical systems (MEMS) technology. For ganglion cell response recording, a conventional glass-substrate MEA is utilized. This new sensing configuration is used to record the response of retinal ganglion cells with respect to three different stimulation methods (monopolar, bipolar, and dual-monopolar stimulation methods). Results show that the geometrical relation between the stimulation microelectrode locations and the response locations seems very low. The threshold charges of the bipolar stimulation and the monopolar stimulation are in the range of 10∼20 nC. The threshold charge of the dual-monopolar stimulation is not obvious. These results provide useful guidelines for developing a sub-retinal prosthesis

Round-robin test on thermal conductivity measurement of ZnO nanofluids and comparison of experimental results with theoretical bounds

Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method. Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device. The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems. This study convincingly demonstrates that the large enhancements in the thermal conductivities of EG-based ZnO nanofluids tested are beyond the lower and upper bounds calculated using the models of the Maxwell and Nan et al. with and without the interfacial thermal resistance