Shells around black holes: the effect of freely specifiable quantities in Einstein's constraint equations

We solve Einstein's constraint equations in the conformal thin-sandwich decomposition to model thin shells of non-interacting particles in circular orbit about a non-rotating black hole. We use these simple models to explore the effects of some of the freely specifiable quantities in this decomposition on the physical content of the solutions. Specifically, we adopt either maximal slicing or Kerr-Schild slicing, and make different choices for the value of the lapse on the black hole horizon. For one particular choice of these quantities the resulting equations can be solved analytically; for all others we construct numerical solutions. We find that these different choices have no effect on our solutions when they are expressed in terms of gauge-invariant quantities.Comment: 9 pages, 4 figure

Fiber-optic three axis magnetometer prototype development

The goal of this research program was to develop a high sensitivity, fiber optic, interferometric, three-axis magnetometer for interplanetary spacecraft applications. Dynamics Technology, Inc. (DTI) has successfully integrated a low noise, high bandwidth interferometer with high sensitivity metallic glass transducers. Also, DTI has developed sophisticated signal processing electronics and complete data acquisition, filtering, and display software. The sensor was packaged in a compact, low power and weight unit which facilitates deployment. The magnetic field sensor had subgamma sensitivity and a dynamic range of 10(exp 5) gamma in a 10 Hz bandwidth. Furthermore, the vector instrument exhibited the lowest noise level when only one axis was in operation. A system noise level of 1 gamma rms was observed in a 1 Hz bandwidth. However, with the other two channels operating, the noise level increased by about one order of magnitude. Higher system noise was attributed to cross-channel interference among the dither fields

Giant dielectric constants at the approach to the insulator-metal transition

We have measured the real and imaginary parts of the dielectric susceptibility of insulating samples of P-doped Si at millikelvin temperatures at 400 MHz using a resonant transmission cavity. We find that the real part is enhanced by more than two orders of magnitude over the isolated donor polarizability, and we determine the exponent which describes the critical divergence of the real part at the insulator-metal transition by fitting the temperature dependence of the corresponding imaginary part. The form of the observed divergence remains unexplained theoretically

Social Media and Negative Word of Mouth: Strategies for Handing Unexpecting Comments

Increased usage of social media by consumers impacts businesses that find it necessary to participate to connect with customers. Because social media is conversational in nature, marketers have little control over the message, unlike more traditional forms of marketing communication. The purpose of this paper is to flesh out the tensions that exist as marketers deal with consumer-generated negative social media messages and present possible responses for marketers dealing with this form of negative word of mouth (WOM). Its contribution lies in unpacking options for companies dealing with such negative social media. Case studies and a conceptual model identifying possible strategies for businesses dealing with negative social media attacks are presented. The five general strategies identified are: delay, respond, partner, legal action, and censorship. Understanding and use of these strategies can assist businesses in dealing with negative WOM and can potentially help them protect their brand image and profitability

θ\theta-dependence of light nuclei and nucleosynthesis

We investigate the impact of the QCD vacuum at nonzero $\theta$ on the properties of light nuclei, Big Bang nucleosynthesis, and stellar nucleosynthesis. Our analysis starts with a calculation of the $\theta$-dependence of the neutron-proton mass difference and neutron decay using chiral perturbation theory. We then discuss the $\theta$-dependence of the nucleon-nucleon interaction using a one-boson-exchange model and compute the properties of the two-nucleon system. Using the universal properties of four-component fermions at large scattering length, we then deduce the binding energies of the three-nucleon and four-nucleon systems. Based on these results, we discuss the implications for primordial abundances of light nuclei, the production of nuclei in stellar environments, and implications for an anthropic view of the universe.Comment: 20 pages, 9 figure

Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump

Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zero-point for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the population level properties of the RC with seismology, and use those as priors on Gaia parallaxes to find the parallax zero-point offset. We then find the position of the RC using published values for the zero-point. We find a seismic temperature insensitive spread of the RC of ~0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of ~0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean zero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudes of -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of ~-70 K, which is compatible with known systematics in spectroscopy.Comment: Accepted for publication in MNRA

The use of induced pluripotent stem cells in domestic animals: a narrative review

Induced pluripotent stem cells (iPSCs) are undifferentiated stem cells characterized by the ability to differentiate into any cell type in the body. iPSCs are a relatively new and rapidly developing technology in many fields of biology, including developmental anatomy and physiology, pathology, and toxicology. These cells have great potential in research as they are self-renewing and pluripotent with minimal ethical concerns. Protocols for their production have been developed for many domestic animal species, which have since been used to further our knowledge in the progression and treatment of diseases. This research is valuable both for veterinary medicine as well as for the prospect of translation to human medicine. Safety, cost, and feasibility are potential barriers for this technology that must be considered before widespread clinical adoption. This review will analyze the literature pertaining to iPSCs derived from various domestic species with a focus on iPSC production and characterization, applications for tissue and disease research, and applications for disease treatment