Discovery of Pulsed X-ray Emission from the SMC Transient RX J0117.6-7330

We report on the detection of pulsed, broad-band, X-ray emission from the transient source RX J0117.6-7330. The pulse period of 22 seconds is detected by the ROSAT/PSPC instrument in a 1992 Sep 30 - Oct 2 observation and by the CGRO/BATSE instrument during the same epoch. Hard X-ray pulsations are detectable by BATSE for approximately 100 days surrounding the ROSAT observation (1992 Aug 28 - Dec 8). The total directly measured X-ray luminosity during the ROSAT observation is 1.0E38 (d/60 kpc)^2 ergs s-1. The pulse frequency increases rapidly during the outburst, with a peak spin-up rate of 1.2E-10 Hz s-1 and a total frequency change 1.8%. The pulsed percentage is 11.3% from 0.1-2.5 keV, increasing to at least 78% in the 20-70 keV band. These results establish RX J0117.6-7330 as a transient Be binary system.Comment: 17 pages, Latex, aasms, accepted for publication in ApJ Letter

Predator-induced Plasticity in Egg Capsule Deposition in the Mud Snail, Tritia obsoleta

Most marine invertebrates develop in the plankton, where microscopic offspring can avoid abundant benthic predators until settlement. However, at least four phyla of marine invertebrates (Annelida, Mollusca, Nemertea, and Platyhelminthes) deposit benthic egg capsules or masses. Often, these animals possess additional means to protect their young, including chemical or morphological defenses or nonrandom selection of deposition sites. Egg capsule deposition is the dominant reproductive strategy among gastropod molluscs, including the mud snail, Tritia obsoleta. In intertidal and shallow subtidal habitats in New England, the mud snail preferentially deposits egg capsules on blades of eelgrass (Zostera marina), a substrate that stands upright in the water column. In a field and lab study, we examined deposition of T. obsoleta egg capsules and found that mud snails lay their egg capsules on eelgrass at 6-8 cm off the benthos or higher. When exposed to egg capsule predators, hermit crabs and periwinkles, mud snails increase the average height of deposition off the benthos by 1-3 cm. In the presence of hermit crabs, capsules deposited on a blade of eelgrass 5 cm above the benthos have survivorship as much as 4 times higher than capsules deposited directly on the benthos. We suggest that deposition of egg capsules off of the benthos is an adaptive response allowing mud snails to protect their embryos from benthic predators. We also provide evidence that snails use characteristics of the eelgrass itself to ensure capsules are laid well above the benthos

Experimental and theoretical electronic structure of EuRh2As2

The Fermi surfaces (FS's) and band dispersions of EuRh2As2 have been investigated using angle-resolved photoemission spectroscopy. The results in the high-temperature paramagnetic state are in good agreement with the full potential linearized augmented plane wave calculations, especially in the context of the shape of the two-dimensional FS's and band dispersion around the Gamma (0,0) and X (pi,pi) points. Interesting changes in band folding are predicted by the theoretical calculations below the magnetic transition temperature Tn=47K. However, by comparing the FS's measured at 60K and 40K, we did not observe any signature of this transition at the Fermi energy indicating a very weak coupling of the electrons to the ordered magnetic moments or strong fluctuations. Furthermore, the FS does not change across the temperature (~ 25K) where changes are observed in the Hall coefficient. Notably, the Fermi surface deviates drastically from the usual FS of the superconducting iron-based AFe2As2 parent compounds, including the absence of nesting between the Gamma and X FS pockets.Comment: 4 pages, 4 figure

Magnetic ordering in EuRh2As2 studied by x-ray resonant magnetic scattering

Element-specific x-ray resonant magnetic scattering investigations were performed to determine the magnetic structure of Eu in EuRh2As2. In the temperature range from 46 K down to 6 K, an incommensurate antiferromagnetic (ICM)structure with a temperature dependent propagation vector (0 0 0.9) coexists with a commensurate antiferromagnetic (CM) structure. Angular-dependent measurements of the magnetic intensity indicate that the magnetic moments lie in the tetragonal basal plane and are ferromagnetically aligned within the a-b plane for both magnetic structures. The ICM structure is a spiral-like magnetic structure with a turn angle of 162 deg between adjacent Eu planes. In the CM structure, this angle is 180 deg. These results are consistent with band-structure calculations which indicate a strong sensitivity of the magnetic configuration on the Eu valence.Comment: 5 pages, 5 figures (technical problem with abstract corrected, no other changes

Effect of ligand substitution on the exchange interactions in {Mn12}-type single-molecule magnets

We investigate how the ligand substitution affects the intra-molecular spin exchange interactions, studying a prototypal family of single-molecule magnets comprising dodecanuclear cluster molecules [Mn12O12(COOR)16]. We identify a simple scheme based on accumulated Pauling electronegativity numbers (a.e.n.) of the carboxylate ligand groups (R). The redistribution of the electron density, controlled by a.e.n. of a ligand, changes the degree of hybridization between 3d electrons of manganese and 2p electrons of oxygen atoms, thus changing the exchange interactions. This scheme, despite its conceptual simplicity, provides a strong correlation with the exchange energies associated with carboxylate bridges, and is confirmed by the electronic structure calculations taking into account the Coulomb correlations in magnetic molecules.Comment: 18 pages, 1 table, 4 figures. Accepted to "Inorganic Chemistry

The Impact of Diabetic Conditions and AGE/RAGE Signaling on Cardiac Fibroblast Migration

© Copyright © 2020 Burr, Harmon and Stewart. Diabetic individuals have an increased risk for developing cardiovascular disease due to stiffening of the left ventricle (LV), which is thought to occur, in part, by increased AGE/RAGE signaling inducing fibroblast differentiation. Advanced glycated end-products (AGEs) accumulate within the body over time, and under hyperglycemic conditions, the formation and accumulation of AGEs is accelerated. AGEs exert their effect by binding to their receptor (RAGE) and can induce myofibroblast differentiation, leading to increased cell migration. Previous studies have focused on fibroblast migration during wound healing, in which diabetics have impaired fibroblast migration compared to healthy individuals. However, the impact of diabetic conditions as well as AGE/RAGE signaling has not been extensively studied in cardiac fibroblasts. Therefore, the goal of this study was to determine how the AGE/RAGE signaling pathway impacts cell migration in non-diabetic and diabetic cardiac fibroblasts. Cardiac fibroblasts were isolated from non-diabetic and diabetic mice with and without functional RAGE and used to perform a migration assay. Cardiac fibroblasts were plated on plastic, non-diabetic, or diabetic collagen, and when confluency was reached, a line of migration was generated by scratching the plate and followed by treatment with pharmacological agents that modify AGE/RAGE signaling. Modification of the AGE/RAGE signaling cascade was done with ERK1/2 and PKC-ζ inhibitors as well as treatment with exogenous AGEs. Diabetic fibroblasts displayed an increase in migration compared to non-diabetic fibroblasts whereas inhibiting the AGE/RAGE signaling pathway resulted in a significant increase in migration. The results indicate that the AGE/RAGE signaling cascade causes a decrease in cardiac fibroblast migration and altering the pathway will produce alterations in cardiac fibroblast migration