Male Dominance in the New Zealand Longfin Eel Population of a New Zealand River: Probable Causes and Implications for Management

The endemic New Zealand longfin eel Anguilla dieffenbachi (hereafter, longfin eel), is overfished, and in southern South Island, New Zealand, rivers have recently become predominated by males. This study examined length and age at sexual differentiation in male eels in the Aparima River catchment (area, 1,375 km(2); mean flow, 20 m(3.)s(-1)) and the sex ratio and distribution of eels throughout the catchment. Longfin eels differentiated into males mostly at lengths from 300 to 460 mm and ages from 10 to 25+ years. Females were rare: Of 738 eels examined for sexual differentiation, 466 were males and 5 were females, and a few others, not examined, were large enough to be female. These counts suggest a male : female ratio among differentiated longfin eels of 68:1. Of 31 differentiated shortfin eels A. australis, less common in the Aparima River, 26 were females. Male longfin eels were distributed throughout the main stern and tributaries; undifferentiated eels were more prevalent in lower and middle reaches and in the main stem than in upper reaches and tributaries. In other studies, male longfin eels predominated commercial catches in the Aparima and four other southernmost rivers, by 2.4:1 to 13.6:1 males to females. The Aparima River had the most skewed sex ratio. Longfin eel catches from the Aparima River will become more male predominated because few sublegal-size females were present. The length-frequency distributions of eels in the present samples and in the commercial catches were truncated just above minimum legal size (about 460 mm), showing that few females escape the fishery. Historically, females predominated these rivers. The recent change in sex ratio is attributable partly to selective harvest of females, and partly to changes in the structure of the population from fishing, such that differentiation into males has been favored. Longevity, delayed sexual maturity, semel-parity, and endemism with restricted range make the longfin eel particularly vulnerable to overfishing

Investigations into the vortex lattice of Ni-chalcogenide and Fe-arsenide superconductors, using small-angle neutron scattering

This work summarises investigations into the superconductivity in 122-structure, I4/mmm symmetry materials; the heavy-fermion TlNi$_2$Se$_2$, and the iron-arsenides (Ba$_0$.$_5$K$_0$.$_5$)Fe$_2$As$_2$ and KFe$_2$As$_2$. Small-angle neutron scattering (SANS) was used to study the vortex lattice (VL) of single crystal samples of these superconductors under temperature, field and angle modulation. We observe a linear response of the form factor to temperature variation for TlNi$_2$Se$_2$ and KFe$_2$As$_2$, concurrent with nodal and unconventional superconductivity. Weak VL anisotropy and no VL morphology were observed in TlNi$_2$Se$_2$ and (Ba$_0$.$_5$K$_0$.$_5$)Fe$_2$As$_2$ respectively, whereas KFe$_2$As$_2$ experiences strong VL anisotropy. Observations of (Ba$_0$.$_5$K$_0$.$_5$)Fe$_2$As$_2$ confirm Pauli paramagnetic effects (PPE) above 0.1H$_c$$_2$ . PPE are seen near Tc for KFe$_2$As$_2$, but not for TlNi$_2$Se$_2$. Literature review regarding the Fermi surface and electron bands confirms van Hove singularities (vHs) near the Fermi level (E$_F$ ) for all three materials. This provides some explanation of the variation in pairing symmetry for similarly structured superconductors. The tuning of the $_v$Hs with respect to E$_F$ determines the symmetry of the gap function as well as the effective mass of the electrons for TlNi$_2$Se$_2$, (Ba$_1$$_-$$_x$K$_x$)Fe$_2$As$_2$ and KFe$_2$As$_2$

Unconventional magnetic phase separation in γ\gamma-CoV2_2O6_6

We have explored the magnetism in the non-geometrically frustrated spin-chain system $\gamma$-CoV$_{2}$O$_{6}$ which possesses a complex magnetic exchange network. Our neutron diffraction patterns at low temperatures ($T$ $\leqslant$ $T_{\mathrm{N}}$ = 6.6 K) are best described by a model in which two magnetic phases coexist in a volume ratio 65(1) : 35(1), with each phase consisting of a single spin modulation. This model fits previous studies and our observations better than the model proposed by Lenertz $et$ $al$ in J. Phys. Chem. C 118, 13981 (2014), which consisted of one phase with two spin modulations. By decreasing the temperature from $T_{\mathrm{N}}$, the minority phase of our model undergoes an incommensurate-commensurate lock-in transition at $T^{*}$ = 5.6 K. Based on these results, we propose that phase separation is an alternative approach for degeneracy-lifting in frustrated magnets

A study into automatic speaker verification with aspects of deep learning

Advancements in automatic speaker verification (ASV) can be considered to be primarily limited to improvements in modelling and classification techniques, capable of capturing ever larger amounts of speech data. This thesis begins by presenting a fairly extensive review of developments in ASV, up to the current state-of-the-art with i-vectors and PLDA. A series of practical tuning experiments then follows. It is found somewhat surprisingly, that even the training of the total variability matrix required for i-vector extraction, is potentially susceptible to unwanted variabilities. The thesis then explores the use of deep learning in ASV. A literature review is first made, with two training methodologies appearing evident: indirectly using a deep neural network trained for automatic speech recognition, and directly with speaker related output classes. The review finds that interest in direct training appears to be increasing, underpinned with the intent to discover new robust 'speaker embedding' representations. Last a preliminary experiment is presented, investigating the use of a deep convolutional network for speaker identification. The small set of results show that the network successfully identifies two test speakers, out of 84 possible speakers enrolled. It is hoped that subsequent research might lead to new robust speaker representations or features

Glucocorticoids and equine pancreatic β cell function

REASONS FOR PERFORMING STUDY: Synthetic glucocorticoids are used to treat inflammatory conditions in horses. In other pregnant animals, glucocorticoids are given to stimulate fetal maturation with long-term metabolic consequences for the offspring if given preterm. However, their metabolic effects during equine pregnancy remain unknown. OBJECTIVE: Thus, this study investigated the metabolic effects of dexamethasone administration on pregnant pony mares and their foals after birth. STUDY DESIGN: Experimental study. METHODS: A total of 3 doses of dexamethasone (200 μg/kg bwt i.m.) were given to 6 pony mares at 48 h intervals beginning at ≈270 days of pregnancy. Control saline injections were given to 5 mares using the same protocol. After fasting overnight, pancreatic β cell responses to exogenous glucose were measured in the mares before, during and after treatment. After birth, pancreatic β cell responses to exogenous glucose and arginine were measured in the foals at 2 and 12 weeks. RESULTS: In mares during treatment, dexamethasone but not saline increased basal insulin concentrations and prolonged the insulin response to exogenous glucose. Basal insulin and glucose concentrations still differed significantly between the 2 groups 72 h post treatment. Dexamethasone treatment significantly reduced placental area but had little effect on foal biometry at birth or subsequently. Foal β cell function at 2 weeks was unaffected by maternal treatment. However, by 12 weeks, pancreatic β cell sensitivity to arginine, but not glucose, was less in foals delivered by dexamethasone- than saline-treated mares. CONCLUSIONS: Dexamethasone administration induced changes in maternal insulin-glucose dynamics, indicative of insulin resistance and had subtle longer term effects on post natal β cell function of the foals. The programming effects of dexamethasone in horses may be mediated partially by altered maternal metabolism and placental growth.These studies were funded by the Horserace Betting Levy Board.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/evj.12560

A Bayesian approach for estimating length-weight relationships in fishes

A Bayesian hierarchical approach is presented for the estimation of length-weight relationships (LWR) in fishes. In particular, estimates are provided for the LWR parameters a and b in general as well as by body shape. These priors and existing LWR studies were used to derive species-specific LWR parameters. In the cases of data-poor species, the analysis includes LWR studies of closely related species with the same body shape. This approach yielded LWR parameter estimates with measures of uncertainty for practically all known 32 000 species of fishes. Provided is a 3 large LWR data set extracted from www.fishbase.org, the source code of the respective analyses, and ready-to-use tools for practitioners. This is presented as an example of a self-learning online database where the addition of new studies improves the species-specific parameter estimates, and where these parameter estimates inform the analysis of new data

Glucocorticoid programming of intrauterine development.

Glucocorticoids (GCs) are important environmental and maturational signals during intrauterine development. Toward term, the maturational rise in fetal glucocorticoid receptor concentrations decreases fetal growth and induces differentiation of key tissues essential for neonatal survival. When cortisol levels rise earlier in gestation as a result of suboptimal conditions for fetal growth, the switch from tissue accretion to differentiation is initiated prematurely, which alters the phenotype that develops from the genotype inherited at conception. Although this improves the chances of survival should delivery occur, it also has functional consequences for the offspring long after birth. Glucocorticoids are, therefore, also programming signals that permanently alter tissue structure and function during intrauterine development to optimize offspring fitness. However, if the postnatal environmental conditions differ from those signaled in utero, the phenotypical outcome of early-life glucocorticoid receptor overexposure may become maladaptive and lead to physiological dysfunction in the adult. This review focuses on the role of GCs in developmental programming, primarily in farm species. It examines the factors influencing GC bioavailability in utero and the effects that GCs have on the development of fetal tissues and organ systems, both at term and earlier in gestation. It also discusses the windows of susceptibility to GC overexposure in early life together with the molecular mechanisms and long-term consequences of GC programming with particular emphasis on the cardiovascular, metabolic, and endocrine phenotype of the offspring.We would also like to thank the BBSRC, the Horserace Betting Levy Board and the Centre for Trophoblast for their financial support

Unconventional superconductivity in the nickel-chalcogenide superconductor, TlNi2_2Se2_2

We present the results of a study of the vortex lattice (VL) of the nickel chalcogenide superconductor TlNi2Se2, using small angle neutron scattering. This superconductor has the same crystal symmetry as the iron arsenide materials. Previous work points to it being a two-gap superconductor, with an unknown pairing mechanism. No structural transitions in the vortex lattice are seen in the phase diagram, arguing against d-wave gap symmetry. Empirical fits of the temperature-dependence of the form factor and penetration depth rule out a simple s-wave model, supporting the presence of nodes in the gap function. The variation of the VL opening angle with field is consistent with earlier reports of of multiple gaps

Magnetic phase diagram of the quantum spin chain compound SrCo2_{2}V2_{2}O8_{8}: a single-crystal neutron diffraction study in magnetic field

We explore the spin states in the quantum spin chain compound SrCo$_{2}$V$_{2}$O$_{8}$ up to 14.9 T and down to 50 mK, using single-crystal neutron diffraction. Upon cooling in zero-field, antiferromagnetic (AFM) order of N\'eel type develops at $T_\mathrm{{N}}$ $\simeq$ 5.0 K. Applying an external magnetic field ($H$ $\parallel$ $c$-axis) destabilizes the N\'eel order, leading to an order-disorder transition when applying a field between $T_\mathrm{{N}}$ and $\sim$ 1.5 K. Below 1.5 K, we observe a N\'eel to longitudinal spin density wave (LSDW) order transition at 3.9 T, and a LSDW to emergent AFM order transition at 7.0 T. Our results also reveal several unique signatures for the states of the spins that are not present in the isostructural counterpart BaCo$_{2}$V$_{2}$O$_{8}$.Comment: 9 pages, 9 figures. Accepted manuscrip