Comparing external and internal dorsal-spine bands to interpret the age and growth of the giant lantern shark, Etmopterus baxteri (Squaliformes: Etmopteridae)

The giant lantern shark, Etmopterus baxteri, is taken as bycatch of commercial fisheries that operate in deepwater off southeastern Australia. Bands on the second dorsal spine were used to obtain age estimates. The number of bands on the external surface of the spine and within the inner dentine layer increased with animal length. Most spines had more bands on the external surface, and the rate of band formation was significantly different between the external surface and the inner dentine layer. Females had a maximum of 57 external bands and 26 internal bands, while males had up to 48 external bands and 22 internal bands. Age estimates from external bands suggest maturity (A ₅₀) at 20 years for males and 30 years for females. Internal band age estimates suggest maturity at 10.5 years for males and 11.5 years for females. Although there is a large discrepancy between these two preliminary (i.e., unvalidated) age estimates, they both suggest that E. baxteri is a long-lived and late maturing species that is likely to be susceptible to over fishing.

Surface bands on deepwater squalid dorsal-fin spines : an alternative method for ageing centroselachus crepidater

Bands on the external surface of the second dorsal-fin spine proved to be a novel method of estimating the age and growth of Centroselachus crepidater. Bands that followed the shape of the spine base were enhanced with an alizarin red derivative. Internal bands in spine cross sections were also examined. The number of both external and internal bands increased with animal size, although most spines had more external than internal bands. External bands were more reliable and were assumed to be annuli. The rate of band formation differed after five bands had been formed, and internal bands ceased forming after 30 years. Females to 54 years old and males to 34 years old were examined. Maturity occurred over a wide age range, with estimates of 20 years for females and 9 years for males. The youngest pregnant female was 27 years old. The Francis reparameterized von Bertalanffy growth model found similar growth for males and females, and the von Bertalanffy equations were L _t = 96.12^{(1 – e(–0.072(t+6.13))}) for females and L_t = 73.22(1 – e^{(–0.141(t+2.99))}) for males.

Numerical simulation of the static recrystalization at micro shear bands

The main aim of this work is application of the developed cellular automata (CA) model to investigate influence of the micro shear bands that are present in the heavily deformed material on the static recrystallization. This initial work is the results of recent experimental analyses indicating that the micro shear bands are preferred sites for nucleation of the recrystallization. The procedure of creation of the initial microstructure with features such as grains and micro shear bands as well as basis of the developed CA code for the static recrystallization are also presented in the paper. Finally, the simulation results obtained from different recrystallization temperatures for the microstructures with and without micro shear bands are compared with each other and differences are discussed.

Fine structure of shear bands formed during hot deformation of two austenitic steels

Shear bands formed during both cold and hot plastic deformation have been linked with several proposed mechanisms for the formation of ultrafine grains. The aim of the present work was to undertake a detailed investigation of the microstructural and crystallographic characteristics of the shear bands formed during hot deformation of a 22Cr-19Ni-3Mo (mass%) austenitic stainless steel and a Fe-30 mass%Ni based austenitic model alloy. These alloys were subjected to deformation in torsion and plane strain compression (PSC), respectively, at temperatures of 900°C and 950°C and strain rates of 0.7s_-1 and 10s_-1, respectively. Transmission electron microscopy and electron backscatter diffraction in conjunction with scanning electron microscopy were employed in the investigation. It has been observed that shear bands already started to form at moderate strains in a matrix of pre-existing microbands and were composed of fine, slightly elongated subgrains (fragments). These bands propagated along a similar macroscopic path and the subgrains, present within their substructure, were rotated relative to the surrounding matrix about axes approximately parallel to the sample radial and transverse directions for deformation in torsion and PSC, respectively. The subgrain boundaries were largely observed to be non-crystallographic, suggesting that the subgrains generally formed via multiple slip processes. Shear bands appeared to form through a co-operative nucleation of originally isolated subgrains that gradually interconnected with the others to form long, thin bands that subsequently thickened via the formation of new subgrains. The observed small dimensions of the subgrains present within shear bands and their large misorientations clearly indicate that these subgrains can serve as potent nucleation sites for the formation of ultrafine grain structures during both subsequent recrystallisation, as observed during the present PSC experiments, and phase transformation.

Design and simulation of a RF MEMS shunt switch for Ka and V bands and the impact of varying its geometrical parameters

RF MEMS plays an important role in microwave switching. The high performance of RF MEMS shunt such as high bandwidth, low insertion loss, and high isolation have made these switches well suitable for high performing microwave and millimeter wave circuits. This paper presents a RF MEMS shunt capacitive switch for Ka and V band application. This paper investigates the effect of various geometrical parameters on RF characteristics of the switch. The simulation results are presented and discussed.

Room temperature fast-ion conduction in imidazolium halide salts

Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10⁻³S cm⁻¹. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient ¹H NMR techniques, which indicated cation diffusion coefficients of the order of 10⁻¹⁰ m² s⁻¹ in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an ¹²⁷I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol⁻¹.

A 13C NMR study of the role of plasticizers in the conduction mechanism of solid polymer electrolytes

The addition of low molecular weight solvents such as dimethyl formamide (DMF) and propylene carbonate (PC) to urethane crosslinked polyethers results in enhancement of polymer segmental motion, as determined in this work from polymer ¹³C spin lattice relaxation measurements (T₁) and glass transition temperatures. The formation of salt-polyether complexes results in a decrease in T₁, even in the presence of the plasticizer, indicating that the polymer ether molecules are still involved in the alkali metal coordination. In a polymer electrolyte containing 1 mol kg⁻¹ LiClO₄ the addition of DMF and PC have significantly different affects on the polymer mobility, although they both enhance the conductivity. The conductivity enhancement therefore is not solely the result of an increased solvent mobility.

Solid state lithium ion conduction in pyrrolidinium imide–lithium imide salt mixtures

The properties of the binary salt system based on mixtures of methyl ethyl pyrrolidinium bis(trifluoromethane sulfonyl) imide (P₁₂) and lithium bis(trifluoromethane sulfonyl) imide (Li imide) are reported. The lithium containing mixtures were found to be more than two orders of magnitude more conductive than the parent P₁₂ phase and the 33 mol% Li imide systems showed a solid state conductivity around 1×10⁻⁴ S/cm at 20°C. This solid state conductivity is believed to take place in plastic crystal phases of the P₁₂ compound.

Fast ion conduction in an acid doped pentaglycerine plastic crystal

High proton conductivity has been achieved in the high temperature plastic crystal phase of pentaglycerine when doped with strong acids, including trifluoromethanesulfonic acid (triflic acid) and methanesulfonic acid. The solid–solid phase transition from the ordered to plastic phase in this material occurs at 86 °C and conductivities of 10^{− 3} S/cm were measured in the high temperature plastic phase on the addition of 1 mol% triflic acid. In the case of methanesulfonic acid, the conductivities showed a greater dependence on acid concentration and were lower than for triflic acid, as expected on the basis of acid strengths. Electrochemical characterisation shows a clear hydrogen reduction process indicating that the proton is the mobile species in the plastic phase.

Fast ion conduction in molecular plastic crystals

Doping of lithium salts and acids into the plastic crystal phase of succinonitrile has shown for the first time of the possibility of creating solid state electrolytes based on plastic crystalline solvents where the matrix itself is neutral and hence not intrinsically conductive. These materials illustrate the concept of a solid state electrolyte solvent. Room temperature conductivities up to 3.4×10⁻⁴ S cm⁻¹ were obtained with 5 wt.% lithium bis(trifluoromethanesulfonylamide) in succinonitrile. Pulsed field gradient NMR measurements indicate that both cation and anion are mobile in this lattice. Proton conductivity was also observed when methane sulfonic acid or glacial acetic acid was used as dopants, however, the conductivity in these systems is limited by the poor dissociating ability of these acids.

Ionic conduction in doped succinonitrile

Doping of lithium salts into the plastic crystal phase of succinonitrile does significantly increase ionic conductivity. This paper investigates the effect of anion (TFSA, Tf and BF₄) on the conductivity and diffusion of the mobile species using impedance spectroscopy and NMR. Room temperature conductivities up to 2.1×10⁻⁴ S cm⁻¹ were obtained with 1 mol% lithium bis(trifluoromethanesulfonyl)amide in succinonitrile. Pulse field gradient NMR has shown that in all three systems investigated, both cation and anion are mobile in this lattice.