Identification of nano-sized holes by TEM in the graphene layer of graphite and the high rate discharge capability of Li-ion battery anodes

SEM images of round-shaped natural graphite, currently widely used as the anode active material of Li-ion batteries, show that the surface mainly consists of the basal plane, which suggests that the Li insertion/extraction reaction rate is quite limited. In contrast to this suggestion, however, the anode of commercial Li-ion batteries is capable of high rate charging/discharging. In order to explain this inconsistency, we propose that there are nano-holes in the graphene layers of the graphite allowing Li to be very easily inserted and extracted via the holes.Prior to the measurements a quantum chemical investigation was performed on the energy required for Li to pass through the hole in a graphene layer (E_act). The results showed that the E_act value is too high when the size is smaller than pyrene, but is fairly low for holes of the size of coronene, implying that Li can pass through the basal plane layer if there is a hole larger than coronene.Characterization of the rounded graphite sample and flaky natural graphite was conducted by constant-current charge/discharge cycle tests, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). XRD revealed no appreciable difference between the rounded graphite and flaky natural graphite, in agreement with Raman data.A detailed analysis of the HRTEM results revealed the presence of a number of variously sized circular images. We believe that these are holes in the graphene layer through which Li can pass. The mechanism of formation of the holes is discussed.     

Immunostimulatory oligonucleotide,CpG-like motif exists in Lactobacillus delbrueckii ssp. bulgaricus NIAI B6

The present study was conducted to find an immunostimulatory oligonucleotide derived from yogurt starter cultures. The chromosomal DNA was purified from nine strains of Lactobacillus delbrueckii ssp. bulgaricus and six strains of Streptococcus thermophilus. An immunostimulatory ability of the DNA was examined in a proliferation of peyer's patch and splenic B cells. Only the DNA from L. bulgaricus NIAI B6 induced a significant proliferation of both cells. When the DNA was cloned and amplified using PCR, the mitogenic activities to B cells were significantly increased by 13 of 135 DNA clones. Ten homologous nucleotide sequences were found as possible oligonucleotide sequences of mitogens, and were then chemically synthesized (sOL-LB1 to sOL-LB10). One CpG-like motif (sOL-LB7; 5'-CGGCACGCTCACGATTCTTG-3') was identified as an immunostimulatory oligonucleotide, but it did not contain palindromic CpG structure known as a B cell-specific mitogen. The sOL-LB7 substantially bound to B cells and increased the CD69 positive cells in peyer's patch cells. This study demonstrated that L. bulgaricus NIAI B6 was a good candidate of a starter culture for the production of new functional foods, "Bio-Defense Foods".     

Humidity dependence of the electric characteristics of quaternized 4-vinylpyridine-styrene copolymer/perchlorate complexes

The dependence of electrical characteristics of copolymer complexes on ambient humidity was studied for complexes of quaternized 4-vinylpyridine-styrene copolymer/perchlorate complexes. When the 4-vinylpyridine content in the copolymer increased, a linear decrease in resistivity was found. From this behaviour, it is concluded that the resistivity can be freely set by variation of the 4-vinylpyridine content in the design of a sensor material. Furthermore, the resistivity was the smallest in the HClO₄ complex and successively became large in the order of the KClO₄ complex and the LiClO₄ complex. From the electrochemical aspect, it was cleared that the degree of dissociation of the counterion exerted influence upon the resistivity of these complexes.     

Modeling of threshold‐voltage‐shift dependency on drain bias in amorphous‐silicon thin‐film transistors in active‐matrix organic light‐emitting‐diode displays

Abstract— A theoretical model to interpret appearances of the threshold voltage shift in hydrogenated amorphous‐silicon (a‐Si:H) thin‐film transistors (TFTs) is developed to better understand the instability of a‐Si:H TFTs for the driving transistors in active‐matrix organic light‐emitting‐diode (AMOLED) displays. This model assumes that the defect creation at channel in a‐Si:H is proportional to the carrier concentration, leading to the defect density varying along the channel depending on the bias conditions. The model interprets a threshold‐voltage‐shift dependency on the drain‐stress bias. The model predicts the threshold voltage shift stressed under a given gate bias applying the drain saturation voltage is 66% of that with zero drain bias, and it even goes down to 50–60% of that when stressed by applying twice the drain saturation voltage.     

Metallic state in a lime-alumina compound with nanoporous structure

We report a metallic state in a nanostructured porous crystal 12CaO x 7Al2O3 by incorporating electrons in the inherent subnanometer-sized cages, in which a three-dimensionally closely packed cage structure acts as an electronic conduction path. High-density electron doping ( approximately 2 x 10(21) cm(-3)), which was achieved by a thermal treatment in Ti metal vapor at approximately 1100 degrees C, induces homogenization of the cage geometry to a symmetric state, resulting in an insulator-metal transition with a sharp enhancement of the electron drift mobility from approximately 0.1 to 4 cm(2) V(-1) s(-1). The results provide an approach for the realization of electroactive functions in materials composed only of environmentally benign elements by utilizing the appropriate nanostructures.     

Validity of generic scenarios used in derivation of exemption levels for surface contamination considering transport-specific aspects

The exemption levels for surface contamination in units of Bq cm(-2) were derived by developing a new universal dose assessment model that consists of three generic scenarios assessed by considering manually, closely and remotely handled objects. In this paper, as part of the process of verifying the validity of these generic scenarios, annual doses that arise from transport-specific aspects are calculated. The maximum annual doses are found to be lower than 10 μSv, which is the bottom line of the exemption dose criterion. The result verifies the validity of the generic scenarios used in the previous derivation of exemption levels for surface contamination.     

System throughput improvement by optimizing timeout for wireless network coding and frame aggregation on CSMA/CA bidirectional two‐hop relaying prototype

This paper reports an outdoor experiment to optimize the timeout of wireless network coding (WNC) and frame aggregation (FA), which are implemented to carrier sense multiple access with collision avoidance (CSMA/CA)‐based wireless two‐hop relay prototype. The system throughput is improved. In the prototype, FA is implemented at the terminal nodes. Timeout function for WNC is available at the relay node and that for FA is available at the terminal nodes. Our outdoor experiment shows that optimizing the timeout values of WNC and FA can improve system throughput by 2.04‐fold compared to the conventional relay without WNC or FA. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.