Nanosize effect on high-rate Li-ion intercalation in LiCoO2 electrode

Recently, battery technology has come to require a higher rate capability. The main difficulty in high-rate charge-discharge experiments is kinetic problems due to the slow diffusion of Li-ions in electrodes. Nanosizing is a popular way to achieve a higher surface area and shorter Li-ion diffusion length for fast diffusion. However, while various nanoelectrodes that provide excellent high-rate capability have been synthesized, a size-controlled synthesis and a systematic study of nanocrystalline LiCoO2 have not been carried out because of the difficulty in controlling the size. We have established the size-controlled synthesis of nanocrystalline LiCoO2 through a hydrothermal reaction and, for the first time, clarified the structural and electrochemical properties of this intercalation cathode material. Lattice expansion in nanocrystalline LiCoO2 was found from powder X-ray diffraction measurements and Raman spectroscopy. Electrochemical measurements and theoretical analyses on nanocrystalline LiCoO2 revealed that extreme size reduction below 15 nm was not favorable for most applications. An excellent high-rate capability (65% of the 1 C rate capability at 100 C) was observed in nanocrystalline LiCoO2 with an appropriate particle size of 17 nm.     

Chemical phenotypes of the hmg1 and hmg2 mutants of Arabidopsis demonstrate the in-planta role of HMG-CoA reductase in triterpene biosynthesis

Plants produce a wide variety of cyclic triterpenes, such as sterols and triterpenoids, which are the major products of the mevalonate (MVA) pathway. It is important to understand the physiological functions of HMG-CoA reductase (HMGR) because HMGR is the rate-limiting enzyme in the MVA pathway. We have previously isolated Arabidopsis mutants in HMG1 and HMG2. Although the biochemical function of HMGR2 has been thought to be almost equal to that of HMGR1, based on similarities in their sequences, the phenotypes of mutants in these genes are quite different. Whereas hmg2 shows no abnormal phenotype under normal growth conditions, hmg1 shows pleiotropic phenotypes, including dwarfing, early senescence, and male sterility. We previously postulated that the 50% decrease in the sterol content of hmg1, as compared to that in the wild type, was a cause of these phenotypes, but comprehensive triterpene profiles of these mutants had not yet been determined. Here, we present the triterpene profiles of hmg1 and hmg2. In contrast to hmg1, hmg2 showed a sterol content 15% lower than that of the wild type. A precise triterpenoid quantification using synthesized deuterated compounds of beta-amyrin (1), alpha-amyrin (2), and lupeol (3) showed that the levels of triterpenoids in hmg1 and hmg2 were 65% and 25% lower than in the wild type (WT), respectively. These results demonstrate that HMGR2 as well as HMGR1 is responsible for the biosynthesis of triterpenes in spite of the lack of visible phenotypes in hmg2.     

Manganese(III,IV) and manganese(III) oxide clusters trapped by copper(II) complexes

Reactions of quinquedentate Schiff base ligands with Mn and Cu ions afforded icosa- and hexadecanuclear mixed-metal clusters in which dinuclear CuII complexes trapped oxo-bridged [MnIII8MnIV4O12] and [MnIII6O6] cores, respectively. Maximum entropy method analysis for synchrotron X-ray diffraction data was used to determine the oxidation states of the Mn ions.     

Al-pillared montmorillonite clay minerals: low-pressure CO adsorption at room temperature

Three kinds of Al-pillared montmorillonite clay minerals (AlPMON) ion-exchanged with cobalt(II), nickel(II), or copper(II) ions were prepared (abbreviated as CoAlPMON, NiAlPMON, or CuAlPMON, respectively). For the 673-K- and 873-K-treated samples, carbon monoxide (CO) adsorption measurement was performed at room temperature under an atmosphere of low CO pressure. The 873-K-treated CuAlPMON sample exhibited more efficient adsorption properties for CO molecules, in comparison with both-temperatures-treated CoAlPMON and NiAlPMON samples and the 673-K-treated CuAlPMON sample. In addition, irreversibly adsorbed CO was present only on the CuAlPMON sample that had been treated at 873 K; the sites responsible for strong CO adsorption were formed in the sample after the pretreatment at the higher temperature.     

Perelman’s invariant,Ricci flow,and the Yamabe invariants of smooth manifolds

In his study of Ricci flow, Perelman introduced a smooth-manifold invariant called . We show here that, for completely elementary reasons, this invariant simply equals the Yamabe invariant, alias the sigma constant, whenever the latter is non-positive. On the other hand, the Perelman invariant just equals +∞ whenever the Yamabe invariant is positive. Received: 6 October 2006; Revised: 17 October 2006     

Formation of wormlike aggregates of fluorocarbon-hydrocarbon hybrid surfactant by Langmuir-Blodgett transfer and alignment of gold nanoparticles

A novel anionic fluorocarbon-hydrocarbon hybrid surfactant (SS-Hyb-Na+) with a disulfide group has been synthesized from 11-bromo-1-undecanal and perfluorohexylethyl iodide via three steps. The Langmuir-Blodgett (LB) transfer of the 1:100 (mol/mol) mixed monolayer of SS-Hyb-Na+ and stearyl alcohol (C18OH) formed on an aqueous solution containing a cationic polymer, poly(diallyldimethylammonium chloride) (PDDA+Cl-) onto a hydrophobic silicon wafer yields the formation of wormlike aggregates consisting of SS-Hyb-/PDDA+ polyion complexes. It is found that the aggregates align along the withdrawal direction of the wafer substrate. When the wafer on which the wormlike aggregates exist is immersed into the dispersion of gold nanoparticles (Au NPs) prepared by the citrate reduction method, Au NPs align along the wormlike structures. Even though the surface of the wafer is placed either vertical or parallel to the monolayer compression direction during the LB transfer, the one-dimensional (1D) array of Au NPs is observed along the withdrawal direction of the wafer. This indicates that the wormlike aggregates of SS-Hyb-/PDDA+ complexes are aligned during the LB transfer, and the aligned aggregates behave as a scaffold in the 1D array of Au NPs.     

Optically induced melting of colloidal crystals and their recrystallization

Colloidal crystals melt by applying focused light of optical tweezers and recrystallize after removing it. The disturbed zone by the light grows radially from the focus point and the ordering starts from the interface with the crystal. Although the larger disturbed zone is observed for the higher power optical tweezers, a master curve is extracted by normalization of the disturbed zone. The temporal changes of the normalized disturbed zone are well described with exponential functions, indicating that the melting and recrystallization process is governed by a simple relaxation mechanism.     

Statistical and Criticality Analysis of the Lower Ionosphere Prior to the 30 October 2020 Samos (Greece) Earthquake (M6.9), Based on VLF Electromagnetic Propagation Data as Recorded by a New VLF/LF Receiver Installed in Athens (Greece)

In this work we present the statistical and criticality analysis of the very low frequency (VLF) sub-ionospheric propagation data recorded by a VLF/LF radio receiver which has recently been established at the University of West Attica in Athens (Greece). We investigate a very recent, strong (M6.9), and shallow earthquake (EQ) that occurred on 30 October 2020, very close to the northern coast of the island of Samos (Greece). We focus on the reception data from two VLF transmitters, located in Turkey and Israel, on the basis that the EQ’s epicenter was located within or very close to the 5th Fresnel zone, respectively, of the corresponding sub-ionospheric propagation path. Firstly, we employed in our study the conventional analyses known as the nighttime fluctuation method (NFM) and the terminator time method (TTM), aiming to reveal any statistical anomalies prior to the EQ’s occurrence. These analyses revealed statistical anomalies in the studied sub-ionospheric propagation paths within ~2 weeks and a few days before the EQ’s occurrence. Secondly, we performed criticality analysis using two well-established complex systems’ time series analysis methods—the natural time (NT) analysis method, and the method of critical fluctuations (MCF). The NT analysis method was applied to the VLF propagation quantities of the NFM, revealing criticality indications over a period of ~2 weeks prior to the Samos EQ, whereas MCF was applied to the raw receiver amplitude data, uncovering the time excerpts of the analyzed time series that present criticality which were closest before the Samos EQ. Interestingly, power-law indications were also found shortly after the EQ’s occurrence. However, it is shown that these do not correspond to criticality related to EQ preparation processes. Finally, it is noted that no other complex space-sourced or geophysical phenomenon that could disturb the lower ionosphere did occur during the studied time period or close after, corroborating the view that our results prior to the Samos EQ are likely related to this mainshock.