VSX J003909.7+611233: a new slowly pulsating B (SPB) star in Cassiopeia?

We report the discovery of a new 13th magnitude variable star in Cassiopeia close to the variable KP Cas.Analysis of six days of intensive photometry shows a regular, near sinusoidal modulation with an amplitude of 0.024 mag and a period of 0.43815(31)d.Although its colour indicates a spectral type around F0 the star probably suffers up to 2−2.5 magnitudes of extinction, so could be an Aor B-type star. Given the period, the low amplitude, the shape of the lightcurve and the probable spectral type we consider it most likely to be a slowly pulsating B-type (SPB) star.The variable has been registered in the International Variable Star Index with the identifier VSX J003909.7+611233

The High-Energy Polarization-Limiting Radius of Neutron Star Magnetospheres I -- Slowly Rotating Neutron Stars

In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect decouples the polarization modes of photons leaving the NS surface. Both the total intensity and the intensity in each of the two modes is preserved along a ray's path through the neutron-star magnetosphere. We analyze the consequences that this effect has on aligning the observed polarization vectors across the image of the stellar surface to generate large net polarizations. Counter to previous predictions, we show that the thermal radiation of NSs should be highly polarized even in the optical. When detected, this polarization will be the first demonstration of vacuum birefringence. It could be used as a tool to prove the high magnetic field nature of AXPs and it could also be used to constrain physical NS parameters, such as $R/M$, to which the net polarization is sensitive.Comment: 23 pages, 9 figure

Explicitly Restarted Arnoldi's Method for Monte Carlo Nuclear Criticality Calculations.

A Monte Carlo implementation of explicitly restarted Arnoldi’s method is developed for estimating eigenvalues and eigenvectors of the transport-fission operator in the Boltzmann transport equation. Arnoldi’s method is an improvement over the power method which has been used for decades. Arnoldi’s method can estimate multiple eigenvalues by orthogonalising the resulting fission sources from the application of the transport-fission operator. As part of implementing Arnoldi’s method, a solution to the physically impossible—but mathematically real—negative fission sources is developed. The fission source is discretized using a first order accurate spatial approximation to allow for orthogonalization and normalization of the fission source required for Arnoldi’s method. The eigenvalue estimates from Arnoldi’s method are compared with published results for homogeneous, one-dimensional geometries, and it is found that the eigenvalue and eigenvector estimates are accurate within statistical uncertainty. The discretization of the fission sources creates an error in the eigenvalue estimates. A second order accurate spatial approximation is created to reduce the error in eigenvalue estimates. An inexact application of the transport-fission operator isalso investigated to reduce the computational expense of estimating the eigenvalues and eigenvectors. The convergence of the fission source and eigenvalue in Arnoldi’s method is analysed and compared with the power method. Arnoldi’s method is superior to the power method for convergence of the fission source and eigenvalue because both converge nearly instantly for Arnoldi’s method while the power method may require hundreds of iterations to converge. This is shown using both homogeneous and heterogeneous one-dimensional geometries with dominance ratios close to 1.Ph.D.Nuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64765/1/jlconlin_1.pd

Distribution of modern benthic foraminiferal assemblages across the Northeast Greenland continental shelf

Analysis of benthic foraminifera in surface samples from 23 sites on the Northeast Greenland continental shelf reveal key assemblage differences between sites. Cluster analysis creates two clear geographical faunal assemblage zones: the 1) inner shelf, and 2) mid and outer shelf sites. These assemblages differ significantly, with the inner shelf sites being characterised by a high percentage and concentration of calcareous species, whilst the mid and outer shelf sites are dominated by agglutinated taxa. At almost all sites, the calcareous assemblages are dominated by Cassidulina neoteretis and Cassidulina reniforme, suggesting that they thrive across the shelf. Stetsonia horvathi, Oridorsalis tener, as well as Glomulina oculus and other miliolid species are found to be key calcareous species at many sites in the inner shelf zone, but they are rare-to-absent on the mid and outer shelf. Canonical correspondence analysis shows that September sea-ice cover and bottom water oxygen content are positively correlated with benthic foraminiferal assemblages at inner shelf sites, whereas organic carbon content is correlated with those in the mid and outer shelf. The formation of seasonal sea-ice and the Northeast Water polynya rejects brine into surrounding waters and transports CO2 to the seafloor, creating a highly corrosive environment for calcium carbonate. These environments are also highly productive, as indicated by the high organic carbon content and low bottom water oxygen content. The oxidation of this organic material creates CO2. We propose that these processes are key drivers in the dissolution of calcareous tests. In contrast, extensive sea-ice, high bottom water oxygen content and low primary productivity in the glacier-proximal region facilitates carbonate preservation

Expansion of the ligand knowledge base for chelating P,P-donor ligands (LKB-PP)

[Image: see text] We have expanded the ligand knowledge base for bidentate P,P- and P,N-donor ligands (LKB-PP, Organometallics2008, 27, 1372–1383) by 208 ligands and introduced an additional steric descriptor (nHe(8)). This expanded knowledge base now captures information on 334 bidentate ligands and has been processed with principal component analysis (PCA) of the descriptors to produce a detailed map of bidentate ligand space, which better captures ligand variation and has been used for the analysis of ligand properties