A geodesic finite-difference time-domain model of magnetized plasma

Electromagnetic wave propagation in the Earth-ionosphere cavity presents an interesting challenge for simulations. Three-dimensional latitude-longitude finite-difference time-domain (FDTD) models accounting for the bathymetry, topography and ionosphere have been developed and applied towards a number of applications previously. However, to date most of these models treat the ionosphere as a simple, isotropic exponential conductivity profile. Only recently has a latitude-longitude FDTD model been developed that treats the ionosphere as a magnetized cold plasma. This opens the door to modeling electromagnetic phenomena at higher frequencies and higher altitudes by accommodating more physics. Further, a geodesic (hexagonal-pentagonal) FDTD model that is more efficient, is easier to implement, and executes faster than latitude-longitude models has been recently developed. In this thesis, the magnetized cold plasma global latitude-longitude algorithm is adapted and implemented for the first time in a geodesic FDTD model of the Earth-ionosphere cavity

Families Funding Change: How Social Justice Giving Honors Our Roots and Strengthens Communities

In this paper, we offer a snapshot of family philanthropy as it often is practiced to day, including what makes traditional family philanthropy different from other forms. It is our hope that our suggestions will be considered when developing strategy, both by family funders for whom our research rings true, and for those whose experiences differ. A significant reason that social justice grantmaking is a powerful means to bolster impact is that it can be integrated into ongoing work regardless of the point of the path that a specific foundation is on

Cultivating Nonprofit Leadership: A (Missed?) Philanthropic Opportunity

From 2003-2012, the country's top foundations dedicated only 0.8 percent of total grants to nonprofit leadership development. And yet, as shown by recent historic progress around immigration, criminal justice and other social justice movements, we need leaders who are strong, skilled and connected to successfully realize positive, social change.What kind of leadership development do social change-makers need to be successful? How can foundations measure the impact of leadership development? What are the most common barriers to funding such programs and how can we overcome these challenges? What can we learn from foundations that are already supporting transformational leadership development, and from the recipients of such support? This report answers these questions and offers the following recommendations to foundations that wish to invest in the current and future leaders of social justice movements:Begin or increase funding for leadership development.Integrate leadership development with program strategy.Engage with grantees as true partners.Use a culturally inclusive lens.Build capacity that supports leadership development

Approximate Inference for Constructing Astronomical Catalogs from Images

We present a new, fully generative model for constructing astronomical catalogs from optical telescope image sets. Each pixel intensity is treated as a random variable with parameters that depend on the latent properties of stars and galaxies. These latent properties are themselves modeled as random. We compare two procedures for posterior inference. One procedure is based on Markov chain Monte Carlo (MCMC) while the other is based on variational inference (VI). The MCMC procedure excels at quantifying uncertainty, while the VI procedure is 1000 times faster. On a supercomputer, the VI procedure efficiently uses 665,000 CPU cores to construct an astronomical catalog from 50 terabytes of images in 14.6 minutes, demonstrating the scaling characteristics necessary to construct catalogs for upcoming astronomical surveys.Comment: accepted to the Annals of Applied Statistic

Cement-Based Materials With Solid-Gel Phase Change Materials For Improving Energy Efficiency Of Building Envelope

This paper evaluated the cement-based materials incorporated with novel solid-gel phase change materials (PCMs) for improving the energy efficiency of building envelopes. This novel PCM is form-stable, which will not leak as solid-liquid PCMs do and not need encapsulation, and it features high energy-storage capacity. Experimental results showed that the thermal properties of cement-based materials were improved as the increase of PCM content. A 30% replacement of sand by volume with PCM can increase the latent heat of the mixture from around 0 to 7 J/g and decrease the thermal conductivity of PCM mortar based on the generalized self-consistent (GSC) model by about 20%. However, the workability and mechanical properties were compromised. The simulation results indicated that 30% PCM-incorporated walls can contribute to 5% energy saving for cooling in a whole year and 12% reduction in peak cooling load compared with the reference without PCM. The proposed PCM composite offers a promising avenue to achieve energy-efficient building envelopes

Spectral Evolution of the Extraordinary Type IIn Supernova 2006gy

We present a detailed analysis of the extremely luminous Type IIn supernova SN2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, expansion speeds, and bolometric luminosity, as well as the progenitor wind density and total swept-up mass overtaken by the shock. SN2006gy can be interpreted in the context of shock interaction with a dense CSM, but with quite extreme values for the CSM mass of 20 Msun and an explosion kinetic energy of at least 5e51 erg. A key difference between SN2006gy and other SNeIIn is that, owing to its large CSM mass, the interaction region remained opaque much longer. At early times, H-alpha widths suggest that the photosphere is ahead of the shock, and photons diffuse out through the opaque CSM. The pivotal transition to optically thin emission begins around day 110, when we start to see a decrease in the blackbody radius and strengthening tracers of the post-shock shell. From the evolution of pre-shock velocities, we deduce that the CSM was ejected by the progenitor in a 1e49 erg precursor event 8yr before explosion. The large CSM mass rules out models involving stars with initial masses around 10Msun. With the full mass budget, even massive M_ZAMS=30-40 Msun progenitor stars are inadequate. At roughly solar metallicity, substantial mass loss probably occurred during the star's life, so SN 2006gy's progenitor is more consistent with LBV eruptions or pulsational pair-instability ejections in stars with initial masses above 100 Msun. This requires significant revision to current paradigms of massive-star evolution. (abridged)Comment: Really long. 30 pages, 26 figs, appendix. Submitted to ApJ - v2 corrected one referenc

Deviations From Axisymmetry Revealed by Line Polarization in the Normal Type Ia SN 2004S

We present a single epoch of high signal-to-noise ratio spectropolarimetry of the Type Ia supernova (SN Ia) 2004S taken nine days after maximum light. The flux spectrum is normal, but with the additional presence of high-velocity (HV) line features in both Ca II and Fe II. The object shows continuum polarization at the 0.4% level in the red, a value which appears to be typical of SNe Ia. The continuum data are consistent with a ~10% global asphericity in an axisymmetric geometry. Unlike previous observations of other SNe Ia with HV features, the HV features in SN 2004S show no strong polarimetric signature, though this may be due to the timing of our observations. Instead, the object shows line polarization features (P < 0.5%) that are rotated with respect to the axis of symmetry of the continuum. The line features are visible in Si II, Fe II, and Ca II, and appear to be narrowly confined in velocity space just above the photosphere. These polarization features are a result of compositional inhomogeneities in the ejecta. They may represent newly synthesized elements whose clumpy spatial distribution within the ejecta is distinct from that of the globally aspherical ejecta as a whole.Comment: 25 pages, 6 figures, AJ, minor revisions to match accepted journal versio

Transformations between 2MASS, SDSS and BVI photometric systems for late-type giants

We present colour transformations from Two Micron All Sky Survey (2MASS) photometric system to Johnson-Cousins system and to Sloan Digital Sky Survey (SDSS) system for late-type giants and vice versa. The giant star sample was formed using surface gravity constraints ($2 < \log g \leq 3$) to Cayrel de Strobel et al.\rq s (2001) spectroscopic catalogue. 2MASS, SDSS and Johnson-Cousins photometric data was taken from Cutri et al. (2003), Ofek (2008) and van Leeuwen (2007), respectively. The final sample was refined applying the following steps: (1) the data were dereddened, (2) the sample stars selected are of the highest photometric quality. We give two--colour dependent transformations as a function of metallicity as well as independent of metallicity. The transformations provide absolute magnitudes and distance determinations which can be used in space density evaluations at relatively short distances where some or all of the SDSS magnitudes of late-type giants are saturated.Comment: The variables and "f" parameters in the equations 15-17 and 27-29 were change