Modeling of Small DC Magnetic Field Response in Trilayer Magnetoelectric Laminate Composites

We consider a magnetoelectric laminate which comprises two magnetostrictive (Ni) layers and an in-between piezoelectric layer (PZT). Using the finite-element method-based software COMSOL, we numerically calculate the induced voltage between the two faces of the PZT piezoelectric layer, by an external homogeneous small-signal magnetic field threading the three-layer Ni/PZT/Ni laminate structure. A bias magnetic field is simulated as being produced by two permanent magnets, as it is done in real experimental setups. For approaching the real materials’ properties, a measured magnetization curve of the Ni plate is used in the computations. The reported results take into account the finite-size effects of the structure, such as the fringing electric field effect and the demagnetization, as well as the effect of the finite conductivity of the Ni layers on the output voltage. The results of the simulations are compared with the experimental data and with a widely known analytical result for the induced magnetoelectric voltage

Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense Rubidium and Cesium Vapor

Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers are 290 MHz for Rb; 2500 MHz for Cs.Comment: submitted to Physical Review Letters, text + 3 figure

Paternal effects on early embryogenesis

Historically, less attention has been paid to paternal effects on early embryogenesis than maternal effects. However, it is now apparent that certain male factor infertility phenotypes are associated with increased DNA fragmentation and/or chromosome aneuploidies that may compromise early embryonic development. In addition, there is a growing body of evidence that the fertilizing sperm has more function than just carrying an intact, haploid genome. The paternally inherited centrosome is essential for normal fertilization, and the success of higher order chromatin packaging may impact embryogenesis. Epigenetic modifications of sperm chromatin may contribute to the reprogramming of the genome, and sperm delivered mRNA has also been hythesized to be necessary for embryogenesis. There is less information about the epigenetic factors affecting embryogenesis than genetic factors, but the epigenetics of gamete and early embryogenesis is a rapidly advancing field

Life History Metrics of Wahoo (Acanthocybium solandri) from the Northern Gulf of Mexico

Wahoo (Acanthocybium solandri) are highly sought in recreational and commercial fisheries in the Gulf of Mexico (GOM), yet the harvest of Wahoo is currently unmanaged in the GOM region outside of Florida waters. Life history metrics are critical to stock assessments and science-based management. Between 2014-2017, Louisiana Department of Wildlife and Fisheries (LDWF) biologists collected Wahoo otoliths and ovaries (n=198) from the northern GOM Wahoo recreational fishery based in Venice, LA to estimate life history metrics of age, growth, and maturity. A protocol was developed to section and age the small, fragile otoliths. A 2-parameter Von Bertalanffy growth model was the most biologically relevant considering the lack of smaller Wahoo sampled. The growth parameters were similar to estimates from prior Wahoo ageing studies. Maturity was determined for 31 female wahoo. When using cortical alveolar oocyte development as the indicator of physiological sexual maturity, binomial logistic regression indicated the length and age at 50% sexual maturity for female Wahoo in the northern GOM was 1015 mm FL and 0.92 years, respectively, similar to previous Wahoo maturity estimates in the GOM and Atlantic. However, when using the tertiary vitellogenic oocyte stage to estimate maturity based on spawning capable females (n=8), the length and age at 50% spawning capable maturity was 1411 mm FL and 3.5 years, respectively. The difference between these 2 maturity measures may indicate that physiological sexual maturity does not give an accurate depiction of the spawning stock

MÖSSBAUER EFFECT STUDIES OF INTERCONFIGURATION FLUCTUATIONS IN METALLIC RARE EARTH COMPOUNDS

Les spectres d'absorption sans recul du rayonnement gamma de 21,6 keV de 15lEu dans EuCu2Si2 et la EuRh2 révèlent un pic unique dont le déplacement isomérique dépend fortement de la température. Les spectres de EuxLa1-xRh2 (0,075 ⩽ x ⩽ 0,5), Eu125Pr875Rh2 et EuRh2-xPtx (0,125 ⩽ x ⩽ 1) comportent plusieurs pics, dont les déplacements isomériques varient souvent anormalement avec la température. Chaque raie de ces spectres est attribuée à un site différent de Eu, caractérisé par le nombre de proches voisins La, Pr ou Pt. Les déplacements isomériques de nombreux pics ne correspondent ni à Eu2+ ni à Eu3+, mais présentent des valeurs intermédiaires. Tous les résultats sont interprétés en terme de fluctuations rapides (τ < 4 × 10-11 s) entre les configurations 4f6 et 4f7. L'énergie nécessaire à une excitation interconfigurationnelle d'un électron de 4f6 à 4f7, en enlevant un électron de la bande de conduction jusqu'au niveau de Fermi et le plaçant ensuite dans le niveau 4f localisé, est de ~ 800 K dans EuCu2Si2 et de ~ 1 200 K dans EuRh2. Dans les composés ternaires, cette énergie dépend notablement du nombre de proches voisins La, Pr ou Pt de Eu, et aussi légèrement de la température. Les niveaux 4f localisés ont une largeur en énergie d'environ 100 K. Les spectres d'absorption sans recul Yb métal du rayonnement gamma de 84 keV de 170Yb émis par une source de 170TmxHo1-xFe2 comportent deux sous-spectres dont l'un présente 5 raies et l'autre est un pic élargi centré autour de la vitesse zéro. Ces spectres sont aussi interprétés en terme de fluctuation interconfigurationnelle (4f14 ࢒ 4f13).Recoilless absorption spectra of the 21.6 keV gamma ray of 151Eu in EuCu2Si2 and in EuRh2 reveal a single absorption line which has a strongly temperature dependent isomer shift. The recoilless absorption spectra in EuxLa1-xRh2 (0.075 ⩽ x ⩽ 0.5), Eu.125Pr.875Rh2 and EuRh2-xPtx (0.125 ⩽ x ⩽ 1) are composed of a few lines, many of which also exhibit strongly temperature dependent isomer shifts. Each line in these spectra is attributed to a different Eu site characterized by the number of La, Pr or Pt nearest neighbors. The isomer shifts of many of the lines correspond to neither Eu3+ nor Eu2+ valencies, but fall in between. All the results are interpreted in terms of fast fluctuations (τ < 4 × 10-11 s) between the 4f6 and 4f7 configurations. The energy necessary to make an interconfiguration excitation from 4f6 to 4f7, by removing an electron from the conduction band at the Fermi level and placing it in the localized 4f level, is ~ 800 K in EuCu2Si2 and ~ 1 200 K in EuRh2. In the ternary compounds, this energy depends significantly on the number of La, Pr or Pt nearest neighbors of the Eu ions, and is somewhat temperature dependent. The localized 4f levels have an energy width of about 100 K. The recoilless absorption spectra in Yb metal of the 84 keV gamma ray of 170Yb emitted by a 170TmxHo1-xFe2 source are composed of two subspectra, one of which is a 5 line split spectrum and the other is a broadened line at zero velocity. These spectra are also interpreted in terms of interconfiguration fluctuations (4f14 ࢒ 4f13)

MR-imaging of hyperpolarized 129Xe produced by spin exchange with diode-laser pumped Cs

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