HACking at Non-linearity: Evidence from Stocks and Bonds

The implicit assumption of linearity is an important element in empirical finance. This study presents a hypothesis testing approach which examines the linear behaviour of the conditional mean between stock and bond returns. Conventional tests detect spurious non-linearity in the conditional mean caused by heteroskedasticity and/or autocorrelation. This study re-states these tests in a heteroskedasticity and autocorrelation consistent (HAC) framework and we find that stock and bond returns are indeed linear-in-the-mean in both univariate and bivariate settings. This study contends that previous research may have detected spurious non-linearity due to size distortions caused by heteroskedasticity and autocorrelation, rather than the presence of genuine non-linearity.linearity, nonlinear, heteroskedasticity-robust tests, autocorrelation-robust tests

On resonance line profiles predicted by radiation driven disk wind models

We report on resonance line profiles predicted by radiation driven disk wind models which extend radially one order of magnitude farther out than our previous models. Our main result is that the inclusion of a disk wind at larger radii changes qualitatively and quantitatively the line profiles predicted by the models. Our new models predict line absorption that is significantly stronger than those predicted by old models. Some of the previous line profiles exhibit a doubled-humped structure near the line center which is now replaced by a more plausible single, blueshifted minimum. We emphasize that the improvements in the shape as well as the strength of the absorption were achieved without changing the gross properties of the wind. In particular, our new models do not predict a higher mass-loss rate than the previous models. The main changes in the line profiles are due to the fact that the ratio between the rotational velocity and poloidal velocity of the wind decreases downstream. The new line profiles reproduce well the line absorption of the nova-like variable, IX~Vel, and promise to reproduce observations of other cataclysmic variables. This success of the radiation driven disk wind model provides an important link between outflows in OB stars and outflows in active galactic nuclei.Comment: to appear in ApJ Lette

Yucca Mountain Saturated Zone Carbon-14

This Scientific Investigation Plan (SIP) provides an overview of the work described in “Yucca Mountain Saturated Zone Carbon-14”, a proposal funded by the U.S. Department of Energy’s (DOE) Office of Repository Development under the UCCSN/YMP Co-op in support of the Science and Technology Initiatives. The objective of this work is to provide improved estimates of the time required for ground water to travel from the site of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, to the accessible environment

Resonance line-profile calculations based on hydrodynamical models of cataclysmic variable winds

We present synthetic line profiles as predicted by the models of 2-D line- driven disk winds due to Proga, Stone & Drew. We compare the model line profiles with HST observations of the cataclysmic variable IX Vel. The model wind consists of a slow outflow that is bounded on the polar side by a fast stream. We find that these two components of the wind produce distinct spectral features. The fast stream produces profiles which show features consistent with observations. These include the appearance of the P-Cygni shape for a range of inclinations, the location of the maximum depth of the absorption component at velocities less than the terminal velocity, and the transition from absorption to emission with increasing inclination. However the model profiles have too little absorption or emission equivalent width. This quantitative difference between our models and observations is not a surprise because the line-driven wind models predict a mass loss rate that is lower than the rate required by the observations. We note that the model profiles exhibit a double-humped structure near the line center which is not echoed in observations. We identify this structure with a non-negligible redshifted absorption which is formed in the slow component of the wind where the rotational velocity dominates over expansion velocity. We conclude that the next generation of disk wind models, developed for application to CVs, needs to yield stronger wind driving out to larger disk radii than do the present models.Comment: LaTeX, 19 pages, to appear in Ap

Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyFor the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes from the recent second Gaia data release. We find significant line-of-sight substructure within the association, which we quantify using a parametrized model that reproduces the observed parallax distribution. This inference approach is necessary due to the non-linearity of the parallax distance transformation and the asymmetry of the resulting probability distribution. Using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood test, we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at ∼1760 pc, further away than recent estimates have envisaged, and a foreground group at ∼1350 pc. We also calculate individual membership probabilities and identify outliers as possible non-members of the association.Peer reviewe

Tissue-specific regulation of sirtuin and nicotinamide adenine dinucleotide biosynthetic pathways identified in C57Bl/6 mice in response to high-fat feeding

Funding: The Scottish Government's Rural and Environment Science and Analytical Services Division.Peer reviewedPostprin

Groundwater Flow and Thermal Modeling to Support a Preferred Conceptual Model for the Large Hydraulic Gradient North of Yucca Mountain

This task will create a two-dimensional, saturated zone, vertical cross-section model of groundwater flow and thermal transport through the large hydraulic gradient (LHG). This model is referenced herein as the thermal model. The scope of this study is limited to presenting a postulated hydrogeologic configuration of the LHG. The conceptualization will include the use of postulated hydrogeologic structures and material properties. The thermal model will be spatially limited to the area immediately upgradient and downgradient of the LHG and will not reproduce the many hydrogeologic features of the existing regional and site-scale models. The thermal model will be orientated north to south, approximately along a saturated zone streamline. The results of the thermal modeling will be compared to temperature data reported for site wells by the U.S. Geological Survey (USGS) and in peer-reviewed journals. Most, if not all, of this reported data is non- qualified. This task will not qualify the reported data and the reported data will be used only as a basis of comparison for the model simulations