Phase formation, crystallography and ionic conductivity of lithium manganese orthosilicates

On the orthosilicate join, Li4SiO4–Mn2SiO4, the new phase Li3Mn0.5SiO4 and a range of Li2+2xMn1–xSiO4 solid solutions with ∼0.76 ≤ x ≤ 1 have been prepared by high-temperature, solid-state reaction and characterized. Li3Mn0.5SiO4 is orthorhombic, space group Pnma, with a = 10.722(3) Å, b = 6.239(2) Å, and c = 5.052(3) Å. A combined analysis of X-ray and neutron powder diffraction data show that its structure is derived from the γII tetrahedral structural family typified by Li3PO4, but with additional Li+ in partially occupied, distorted octahedral sites. These octahedral sites are linked by a combination of edge- and face-sharing, similar to that in the nickel arsenide structure and their partial occupancy is responsible for an Li+ ion conductivity of, for example, ∼ 1 × 10–8 S cm–1 at 60 °C, with activation energy 0.93(1) eV, which is many orders of magnitude higher than that of Li2MnSiO4

In-Situ Neutron Studies of Electrodes for Li-Ion Batteries Using a Deuterated Electrolyte: LiCoO2 as a Case Study

An electrochemical cell for in-situ neutron powder diffraction studies of electrode materials for lithium-ion batteries is presented. The device has a coin cell geometry, consisting of 8.4 cm diameter, circular components that can be stacked together and clamped tight using sixteen polyetheretherketone (PEEK) screws. The background issue associated with incoherent scattering from hydrogen within the organic electrolyte was addressed by replacing the normal electrolyte with a deuterated analogue, significantly improving the peak-to-background ratio of the in-situ neutron data. Initial in-situ studies showed clear structural evolution within LixCoO2 during charge in a half-cell with lithium metal as the counter electrode, in agreement with previous studies. In addition, the in-situ cell was shown to provide electrochemical performance comparable to that of equivalent coin cells of the commercial design and, following these demonstration studies, is available for in-situ structural studies of other lithium cathode and anode materials during charge/discharge cycling

Glass fibre poling and applications

Recent developments in the application of poled optical fibres to electrooptic light modulation and second harmonic generation are reviewed

A Study of the 't Hooft Model with the Overlap Dirac Operator

We present the results of an exploratory numerical study of two dimensional QCD with overlap fermions. We have performed extensive simulations for U(N_c) and SU(N_c) color groups with N_c=2, 3, 4 and coupling constants chosen to satisfy the 't Hooft condition g^2 N_c =const=4/3. We have computed the meson spectrum and decay constants, the topological susceptibility and the chiral condensate. For U(N_c) gauge groups, our results indicate that the Witten-Veneziano relation is satisfied within our statistical errors and that the chiral condensate for N_f=1 is compatible with a non-zero value. Our results exhibit universality in N_c and confirm once more the excellent chiral properties of the overlap-Dirac operator.Comment: 18 pages, 4 figure

A new approach to the exact solutions of the effective mass Schrodinger equation

Effective mass Schrodinger equation is solved exactly for a given potential. Nikiforov-Uvarov method is used to obtain energy eigenvalues and the corresponding wave functions. A free parameter is used in the transformation of the wave function. The effective mass Schrodinger equation is also solved for the Morse potential transforming to the constant mass Schr\"{o}dinger equation for a potential. One can also get solution of the effective mass Schrodinger equation starting from the constant mass Schrodinger equation.Comment: 14 page

Synthesis and characterisation of the new oxyfluoride Li+ ion conductor, Li5SiO4F

A new polymorphic phase, Li5SiO4F, with Li+ ion dynamics that are structurally distinct from Li4SiO4, is described. The γ polymorph forms at 750–775 °C, melts incongruently at 800 °C and crystallizes in a monoclinic unit cell: a = 8.67(1) Å b = 16.51(1) Å c = 11.23(2) Å β = 96.61(4) ° and V = 1602.3(3) Å3. The α polymorph forms at 650 °C and appears to be metastable. The γ polymorph has a Li+ ion conductivity of 1.2 × 10−7 S cm−1 at 40 °C, that is several orders of magnitude higher than both the α polymorph and Li4SiO4, with an associated activation energy of 0.51(1) eV. Variable temperature 19F and 7Li static NMR measurements show the absence of F− mobility but the existence of Li+ mobility and confirm that Li+ is the main charge carrier in both polymorphs of Li5SiO4F. 7Li line narrowing NMR experiments suggest that the barrier to local Li hopping is fairly small (0.2–0.3 eV) with faster Li+ ion dynamics in γ-Li5SiO4F compared to α-Li5SiO4F. γ-Li5SiO4F has negligible electronic conductivity, is stable in contact with Li metal and is a new type of stoichiometric, mixed anion, Li+ ion conductor

Performance of Transgenic Chrysanthemum Harbouring Wasabi Defensin Gene for White Rust Disease Resistance

This study was intended to obtain white rust (Puccinia horiana) disease resistance Chrysanthemum transformed with wasabi defensin gene through mediation of Agrobacterium tumefaciens from three explant sources, i.e., leaf, lateral shoot bud, and internode. Observations were made on transformation efficiency, PCR analysis, in vitro and ex vitro disease resistance tests. Results showed that efficiency of transgenic callus and shoot regeneration was found both highest from lateral shoot buds (57.5% and 50.0%, respectively). PCR analysis showed that three putative transgenic plantlets from lateral shoot buds and one from leaf explant were putative transgenic carrying the wasabi, hpt, and nptII genes. Rooting test showed that the highest number of rooted plants was found in treatment of hygromycin (Hg) 25 mg L-1 (81%) and lowest was in treatment combination of kanamycin (Km) 50 mg L-1 + Hg 25 mg L-1 (25%). In vitro disease resistance test with sorus inoculation of P. horiana, directly on the leaves, resulted in 20 resistant plants out of 30 putative transgenic plants (66.67%). Ex vitro testing on adult plants of the same samples in a confined closed greenhouse (CGH) resulted in average of 80% transgenic Chrysanthemum plants were resistant, whereas in control plants caused white rust disease symptom

A Fast Radio Burst in a Compact Galaxy Group at z ∼ 1

FRB 20220610A is a high-redshift fast radio burst (FRB) that has not been observed to repeat. Here, we present rest-frame UV and optical Hubble Space Telescope observations of the field of FRB 20220610A. The imaging reveals seven extended sources, one of which we identify as the most likely host galaxy with a spectroscopic redshift of z = 1.017. We spectroscopically confirm three additional sources to be at the same redshift and identify the system as a compact galaxy group with possible signs of interaction among group members. We determine the host of FRB 20220610A to be a star-forming galaxy with a stellar mass of ≈109.7 M ⊙, mass-weighted age of ≈2.6 Gyr, and star formation rate (integrated over the last 100 Myr) of ≈1.7 M ⊙ yr−1. These host properties are commensurate with the star-forming field galaxy population at z ∼ 1 and trace their properties analogously to the population of low-z FRB hosts. Based on estimates of the total stellar mass of the galaxy group, we calculate a fiducial contribution to the observed dispersion measure from the intragroup medium of ≈90-182 pc cm−3 (rest frame). This leaves a significant excess of 515 − 272 + 122 pc cm−3 (in the observer frame); further observation will be required to determine the origin of this excess. Given the low occurrence rates of galaxies in compact groups, the discovery of an FRB in one demonstrates a rare, novel environment in which FRBs can occur. As such groups may represent ongoing or future mergers that can trigger star formation, this supports a young stellar progenitor relative to star formation

PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation

PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.Comment: 13 page

Cracks in Martensite Plates as Hydrogen Traps in a Bearing Steel

It is demonstrated that a macroscopically homogeneous distribution of tiny cracks introduced into a martensitic bearing steel sample can provide powerful hydrogen traps. The phenomenon has been investigated through thermal desorption spectroscopy and hydrogen permeation measurements using both cracked and integral samples. The e↵ective hydrogen di↵usion coefficient through the cracked sample is found to be far less than in the uncracked one. Similarly, when samples are charged with hydrogen, and then subjected to thermal desorption analysis, the amount of hydrogen liberated from the cracked sample is smaller due to the trapping by the cracks. Theoretical analysis of the data shows that the traps due to cracks are so strong, that any hydrogen within the cracks can never in practice de-trap and cause harm by mechanisms that require the hydrogen to be mobile for the onset of embrittlement.W. Solano-Alvarez is very grateful for support from the Worshipful Company of Ironmongers, CONACyT, the Cambridge Overseas Trust, and the Roberto Rocca Education Programme.This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11661-014-2680-8