HELIOS-K: An Ultrafast, Open-source Opacity Calculator for Radiative Transfer

We present an ultrafast opacity calculator that we name HELIOS-K. It takes a line list as an input, computes the shape of each spectral line and provides an option for grouping an enormous number of lines into a manageable number of bins. We implement a combination of Algorithm 916 and Gauss-Hermite quadrature to compute the Voigt profile, write the code in CUDA and optimise the computation for graphics processing units (GPUs). We restate the theory of the k-distribution method and use it to reduce $\sim 10^5$ to $10^8$ lines to $\sim 10$ to $10^4$ wavenumber bins, which may then be used for radiative transfer, atmospheric retrieval and general circulation models. The choice of line-wing cutoff for the Voigt profile is a significant source of error and affects the value of the computed flux by $\sim 10\%$. This is an outstanding physical (rather than computational) problem, due to our incomplete knowledge of pressure broadening of spectral lines in the far line wings. We emphasize that this problem remains regardless of whether one performs line-by-line calculations or uses the k-distribution method and affects all calculations of exoplanetary atmospheres requiring the use of wavelength-dependent opacities. We elucidate the correlated-k approximation and demonstrate that it applies equally to inhomogeneous atmospheres with a single atomic/molecular species or homogeneous atmospheres with multiple species. Using a NVIDIA K20 GPU, HELIOS-K is capable of computing an opacity function with $\sim 10^5$ spectral lines in $\sim 1$ second and is publicly available as part of the Exoclimes Simulation Platform (ESP; www.exoclime.org).Comment: Accepted by ApJ. 8 pages, 5 figure

College Students Helping America

The Corporation has produced the most comprehensive national report ever conducted on college student volunteering in the United States. "College Students Helping America" concludes that college student volunteering increased by approximately 20 percent between 2002 and 2005, as students have become involved in helping their communities. The report presents data on student volunteering and volunteers in an easily accessible format that will be useful to people -- whether experienced researchers, policy makers, or just concerned citizens -- interested in learning more about volunteering in the states. "College Students Helping America" is based on statistics from the U.S. Census Bureau and the Bureau of Labor Statistics. The report includes a state-by-state ranking of college student volunteering

The relationship of marine stratus to synoptic conditions

The marine stratus which persistently covered most of the eastern Pacific Ocean, had large clear areas during the FIRE Intensive Field Operations (IFO) in 1987. Clear zones formed inside the large oceanic cloud mass on almost every day during the IFO. The location and size of the clear zones varied from day to day implying that they were related to dynamic weather conditions and not to oceanic conditions. Forecasting of cloud cover for aircraft operations during the IFO was directed towards predicting when and where the clear and broken zones would form inside the large marine stratus cloud mass. The clear zones often formed to the northwest of the operations area and moved towards it. However, on some days the clear zones appeared to form during the day in the operations area as part of the diurnal cloud burn off. The movement of the clear zones from day to day were hard to follow because of the large diurnal changes in cloud cover. Clear and broken cloud zones formed during the day only to distort in shape and fill during the following night. The field forecasters exhibited some skill in predicting when the clear and broken cloud patterns would form in the operations area. They based their predictions on the analysis and simulations of the models run by NOAA's Numeric Meteorological Center. How the atmospheric conditions analyzed by one NOAA/NMC model related to the cloud cover is discussed

THOR 2.0: Major Improvements to the Open-Source General Circulation Model

THOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or Solar System-centric tunings. It solves the general non-hydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building upon the work of Mendon\c{c}a et al. (2016). First, while the Horizontally Explicit Vertically Implicit (HEVI) integration scheme is the same as that described in Mendon\c{c}a et al. (2016), we provide a clearer description of the scheme and improved its implementation in the code. The differences in implementation between the hydrostatic shallow (HSS), quasi-hydrostatic deep (QHD) and non-hydrostatic deep (NHD) treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally-locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and non-hydrostatic simulations are negligible in the Earth case, but pronounced in the hot Jupiter case. Finally, the effects of the so-called "sponge layer", a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR.Comment: 57 pages, 31 figures, revised, accepted for publication in ApJ

Volunteering in America: 2007 City Trends and Rankings

"Volunteering in America: 2007 City Trends and Rankings" uses volunteer data collected by the U.S. Census Bureau and Bureau of Labor Statistics from 2004-2006. It ranks and includes profiles for 50 of the largest cities including the volunteer rate; the types of organizations through which residents serve; their main volunteering activities, the average hours per year and volunteer rates for age and gender demographic groups, and key trends and highlights. The report also analyzes social and demographic trends affect city volunteer rates and finds that there are four key drivers of volunteering: community attachment; commuting times, high school graduation levels and poverty; and the prevalence of nonprofits and their capacity to retain volunteers from year to year. The information on volunteering at the local level can help local governments, community leaders, service organizations, and volunteers nationwide develop a volunteer growth strategy, set goals to increase the level of individual engagement in volunteer activities, and build the infrastructure of nonprofits and communities to support more volunteer opportunities

HELIOS-Retrieval: An Open-source, Nested Sampling Atmospheric Retrieval Code, Application to the HR 8799 Exoplanets and Inferred Constraints for Planet Formation

We present an open-source retrieval code named HELIOS-Retrieval (hereafter HELIOS-R), designed to obtain chemical abundances and temperature-pressure profiles from inverting the measured spectra of exoplanetary atmospheres. In the current implementation, we use an exact solution of the radiative transfer equation, in the pure absorption limit, in our forward model, which allows us to analytically integrate over all of the outgoing rays (instead of performing Gaussian quadrature). Two chemistry models are considered: unconstrained chemistry (where the mixing ratios are treated as free parameters) and equilibrium chemistry (enforced via analytical formulae, where only the elemental abundances are free parameters). The nested sampling algorithm allows us to formally implement Occam's Razor based on a comparison of the Bayesian evidence between models. We perform a retrieval analysis on the measured spectra of the HR 8799b, c, d and e directly imaged exoplanets. Chemical equilibrium is disfavored by the Bayesian evidence for HR 8799b, c and d. We find supersolar C/O, C/H and O/H values for the outer HR 8799b and c exoplanets, while the inner HR 8799d and e exoplanets have substellar C/O, substellar C/H and superstellar O/H values. If these retrieved properties are representative of the bulk compositions of the exoplanets, then they are inconsistent with formation via gravitational instability (without late-time accretion) and consistent with a core accretion scenario in which late-time accretion of ices occurred differently for the inner and outer exoplanets. For HR 8799e, we find that spectroscopy in the K band is crucial for constraining C/O and C/H. HELIOS-R is publicly available as part of the Exoclimes Simulation Platform (ESP; www.exoclime.org).Comment: 27 pages, 21 figures, 3 tables, published in A

Back to field: uncertainty and risk in field research

The rapid spread of COVID-19 beginning in early 2020 caused global disruption. As the risk of infection rose and public health authorities around the world enacted measures to contain the virus, everyday life ground to a halt. Activities that seemed routine in late 2019 became fraught with uncertainty. Fieldwork was no exception. Most field researchers had to change or cancel at least some of their plans; some left their field in a hurry before travel was shut down while others had to lock down on site; most academic institutions restricted travel, with some even prohibiting all forms of international movement. In brief, many traditional forms of fieldwork became all but impossible during the pandemic

Osteochondritis Dissecans Development after Bone Contusion of the Knee in the Skeletally Immature: A Case Series

Osteochondritis dissecans (OCD) is thought to be an acquired osteochondral disorder, and its etiology may be multi-factorial. Trauma, both acute and repetitive events, has previously been proposed as a potential cause for OCD development. We present two cases of skeletally immature males who developed a symptomatic OCD lesion following a femoral condyle bone contusion. These cases suggest that an acute traumatic event may lead to the development of OCD of the knee

Volunteering in America: 2007 State Trends and Rankings in Civic Life

Analyzes information on volunteering in America in general and in individual states. Part one gives a general overview of American voluntarism. Part two compares rates of voluntarism across the 50 states and Washington, D.C. Part three analyzes voluntarism within each state by focusing on the number of volunteer hours and demographics. The last section is a technical note on statistical methods and data sources. With bibliographical references