Aspects of selection in an interbred flock based on Perendales crossed with Merino X Romney ewes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University

Genetic, phenotypic and environmental parameters were estimated from hogget traits recorded on 237 Perendale x (Merino x Romney) ewe hoggets between 1977 and 1984. Non-genetic effects on weaning weight (WW) for 634 ewe and ram lambs were analysed. A selection objective and criteria was defined and appraised for the flock. The traits examined were hogget liveweight (HLW), greasy fleece weight (GFW), clean fleece weight (CFW), quality number (QN), character grade (CHG), handle grade (HG), cotting grade (CG), soundness grade (SG), greasy colour grade (GCG), scoured colour grade (SCG), staple length (SL), total crimp number (TCN), clean scoured yield (Y), mean fibre diameter (MFD) and crimps per centimetre (CPC). The least squares method of fitting constants was used to estimate the major environmental factors influencing the traits studied. Heritabilities (h2) were obtained by the daughter-dam regression (DDR) and daughter-dam correlation (DDC) methods. The genetic (rG), phenotypic (rP) and environmental (rE) correlations were calculated by the daughter-dam method. The estimates of environmental effects agree in most cases with the published estimates. Between year differences were important sources of variation and had a highly significant effect on all traits except SCG. Rearing rank effect was found to be the most important source of variation for WW and HLW. Age of dam and sex had a highly significant effect on WW. Neither rearing rank nor age of dam exerted any significant influence on wool traits. The estimates of heritability calculated by daughter-dam regression method were: HLW (0.16), GFW (0.17), CFW (0.24), QN (0.42), CHG (0.38), SG (0.02), GCG (0.38), SCG (0.09), SL (0.12), TCN (0.08), Y (0.41) and MFD (0.29). Genetic and phenotypic correlations calculated among some hogget traits were respectively: HLW x GFW (0.67 and 0.66); HLW x CFW (0.62 and 0.56); HLW x SL (0.79 and 0.44); HLW x MFD (-0.45 and 0.24); GFW x CFW (0.87 and 0.94); GFW x SL (0.37 and 0.60); GFW x MFD (-0.98 and 0.38); CFW x GCG (0.52 and 0.02); QN x MFD (-0.79 and -0.30); SG x MFD (0.73 and -0.21); GCG x SCG (0.87 and 0.38); GCG x Y (0.96 and 0.04) and SCG x Y (0.77 and 0.00). Lifetime economic weights derived using the marginal profit method were calculated to define a selection objective for the flock studied. The traits included in the objective were number of lambs weaned (NLW (dam)), WW, CFW, MFD and SCG. Besides the traits in the objective, HLW, GFW, QN and GCG were included as selection criteria. The appropriate selection indices for ram hoggets (I1), ewe hoggets (I2) and lambs (I3 ) were respectively: I1 =4.66 NLW (dam) + 0.62 HLW + 0.10 WW + 3.91 GFW - 1.70 MFD + 0.50 GCG. I2 =4.79 NLW (dam) + 0.61 HLW + 0.04 WW + 1.99 GFW + 0.23 QN + 1.60 GCG. I3 = 4.87 NLW (dam) + 0.48 WW

Effective Dirac Hamiltonian for anisotropic honeycomb lattices: optical properties

We derive the low-energy Hamiltonian for a honeycomb lattice with anisotropy in the hopping parameters. Taking the reported Dirac Hamiltonian for the anisotropic honeycomb lattice, we obtain its optical conductivity tensor and its transmittance for normal incidence of linearly polarized light. Also, we characterize its dichroic character due to the anisotropic optical absorption. As an application of our general findings, which reproduce the case of uniformly strained graphene, we study the optical properties of graphene under a nonmechanical distortion

Simultaneous electric and magnetic field induced nonvolatile memory

We investigate the electric field induced resistive switching effect and magnetic field induced fraction enlargement on a polycrystalline sample of a colossal magnetoresistive compound displaying intrinsic phase coexistence. Our data show that the electric effect (presumably related to the presence of inhomogeinities) is present in a broad temperature range(300 to 20 K), being observable even in a mostly homogeneous ferromagnetic state. In the temperature range in which low magnetic field determines the phase coexistence fraction, both effects, though related to different mechanisms, are found to determine multilevel nonvolatile memory capabilities simultaneously.Comment: Submited to AP

Increased photorefractive sensitivity in double-doped KTa1-xNbxO3:Fe,Ti

Double-doped KTN:Fe,Ti exhibits increased photorefractive sensitivity compared with single-doped KTN:Fe and KTN:Ti. Absorption and photoconductivity measurements correlate the increase with an increased concentration of Fe in the reduced Fe2+ valence state and to an increased fraction of Fe incorporated into the crystal from the flux

Determination of the physical parameters controlling the photorefractive effect in KTa1-xNbx O3:Cu,V

We report photorefractive, absorption, and photoconductivity measurements made on a KTa1-xNbxO3:CuY sample after a series of reduction and oxidation treatments. All relevant physical parameters that enter into the Kukhtarev model of the photorefractive effect are determined. Photorefractive measurements are compared with those expected from theory. The oxidation-reduction process is modeled, which permits us to determine the heat treatment that is necessary to produce a given index change and response time. We discuss approaches to optimization of the photorefractive sensitivity

The electrical current effect in phase separated La5/8-yPryCa3/8MnO3: Charge order melting vs. Joule heating

We have studied the effect of electric field on transport properties of the prototypical phase separated manganite La5/8-yPryCa3/8MnO3 with y=0.34. Our results show that the suggested image in which the charge ordered state is melted by the appliance of an electric current and/or voltage has to be revised. We were able to explain the observed resistivity drop in terms of an artifact related to Joule heating and the particular hysteresis that the system under study display, common to many other phase separated manganites.Comment: 2 figures. Accepted in J. Appl. Phy

Hydrostatic pressure to trigger and assist magnetic transitions: baromagnetic refrigeration

The possible application of the barocaloric effect to produce solid state refrigerators is a topic of interest in the field of applied physics. In this work, we present experimental data about the influence of external pressure on the magnetic properties of a manganite with phase separation. Using the Jahn Teller effect associated with the presence of the charge ordering we were able to follow the transition to the ferromagnetic state induced by pressure. We also demonstrated that external pressure can assist the ferromagnetic state, decreasing the magnetic field necessary to generate the magnetic transition.Comment: Acepted to be published in Applied Physics Letter