Representations of Time Coordinates in FITS

In a series of three previous papers, formulation and specifics of the representation of World Coordinate Transformations in FITS data have been presented. This fourth paper deals with encoding time. Time on all scales and precisions known in astronomical datasets is to be described in an unambiguous, complete, and self-consistent manner. Employing the well--established World Coordinate System (WCS) framework, and maintaining compatibility with the FITS conventions that are currently in use to specify time, the standard is extended to describe rigorously the time coordinate. World coordinate functions are defined for temporal axes sampled linearly and as specified by a lookup table. The resulting standard is consistent with the existing FITS WCS standards and specifies a metadata set that achieves the aims enunciated above.Comment: FITS WCS Paper IV: Time. 27 pages, 11 table

Fast two-dimensional model

A two dimensional (altitude and latitude) model of the atmosphere is used to investigate problems relating to the variability of the dynamics and temperature of the atmosphere on the ozone distribution, solar cycle variations of atmospheric constituents, the sensitivity of model results to tropospheric trace gas sources, and assessment computations of changes in ozone related to manmade influences. In a comparison between two dimensional model results in which the odd nitrogen family was transported together and model results in which the odd nitrogen species was transported separately, it was found that the family approximations are adequate for perturbation scenario calculations

Species-specific abundance of bivalve larvae in relation to biological and physical conditions in a Cape Cod estuary : Waquoit Bay, Massachusetts (USA)

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 469 (2012): 53-69, doi:10.3354/meps09998.Physical and biological conditions impact recruitment and adult population structure of 34 marine invertebrates by affecting early life history processes from spawning to post-settlement. We investigated how temperature, salinity and phytoplankton influenced larval abundance and larval size structure for three species of bivalves over two non-consecutive years in Waquoit Bay, MA. Abundance and size of Mercenaria mercenaria (quahog), Anomia simplex (jingle clam), and Geukensia demissa (ribbed mussel) larvae were compared between locations in the bay and with environmental conditions. Shell birefringence patterns using polarized light microscopy were used to distinguish species. Larval abundances for all three species were higher in 2009 than in 2007 and were positively correlated with temperature in both years. Differences in larval abundance and size structure between bay sites were attributed to salinity tolerances and potential source locations. Higher survival in 2009 than in 2007, as determined by number of pediveligers, was likely due to higher temperatures and greater food availability during the peak abundance months of July and August in 2009. Yearly differences in larval growth and survival can have a large impact on recruitment. Knowing the optimal periods and locations for larval abundance and survival can be useful for isolating species-specific patterns in larval dispersal and to aid resource managers in enhancing or restoring depleted populations.This research was conducted in the National Estuarine Research Reserve System under an award to S. Gallager and C. Mingione Thompson from the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Ocean Service, National Oceanic and Atmospheric Administration

High-frequency accelerometer recording of key predatory behaviors in vipers: validation and case study with Timber Rattlesnakes (Crotalus horridus)

High-frequency accelerometer recording of key predatory behaviors in vipers: validation and case study with Timber Rattlesnakes (Crotalus horridus) Morgan Thompson, Richard H. Adams, Anna F. Tipton, and Dominic L. DeSantis Tri-axial accelerometers (ACTs) are becoming increasingly common in studies of animal behavior wherein direct observation of subjects in nature is constrained or impossible. ACTs are small (\u3c 1 g) piezo-electric (spring-like) sensors that measure three-dimensional acceleration (upward, downward, and side-to-side) derived from subject motion. When leveraged with advanced machine learning techniques, these data can enable precise automated classification of a wide range of movement-mediated behaviors. Until recently, ACTs were largely reserved for larger-bodied organisms or those most amenable to the temporary external attachment of devices. Ongoing ACT miniaturization has now expanded the breadth of organisms amenable to these methods. This project aims to expand on a recently developed framework for ACT monitoring in wild-ranging snakes, a group that has been mostly overlooked in biologging applications. We are currently conducting extensive captive validation trials for robust model training and testing to enable classification of predatory behaviors, including striking and ingestion of prey items, in Timber Rattlesnakes (Crotalus horridus). Following captive validation, we will translate this method to the field with a population of C. horridus in the lower Piedmont of middle Georgia to evaluate the efficacy of externally attached ACTs for remote and continuous monitoring of predatory behaviors by wild-ranging vipers. We envision validation of this technique carrying significant conservation and management implications; real-time monitoring of foraging efficiency in the field opens the door to improved interpretation of the causes and consequences of variation in individual behavior and performance, and its ultimate effects on population trajectories

Bulk meltwater flow and liquid water content of snowpacks mapped using the electrical self-potential (SP) method

Our ability to measure, quantify and assimilate hydrological properties and processes of snow in operational models is disproportionally poor compared to the significance of seasonal snowmelt as a global water resource and major risk factor in flood and avalanche forecasting. We show here that strong electrical self-potential fields are generated in melting in situ snowpacks at Rhone Glacier and Jungfraujoch Glacier, Switzerland. In agreement with theory, the diurnal evolution of self-potential magnitudes ( ∼ 60–250mV) relates to those of bulk meltwater fluxes (0–1.2 × 10−6m3s−1) principally through the permeability and the content, electrical conductivity and pH of liquid water. Previous work revealed that when fresh snow melts, ions are eluted in sequence and electrical conductivity, pH and self-potential data change diagnostically. Our snowpacks had experienced earlier stages of melt, and complementary snow pit measurements revealed that electrical conductivity ( ∼ 1–5 × 10−6Sm−1) and pH ( ∼ 6.5–6.7) as well as permeabilities (respectively  ∼ 9.7 × 10−5 and  ∼ 4.3 × 10−5m2 at Rhone Glacier and Jungfraujoch Glacier) were invariant. This implies, first, that preferential elution of ions was complete and, second, that our self-potential measurements reflect daily changes in liquid water contents. These were calculated to increase within the pendular regime from  ∼ 1 to 5 and  ∼ 3 to 5.5% respectively at Rhone Glacier and Jungfraujoch Glacier, as confirmed by ground truth measurements. We conclude that the electrical self-potential method is a promising snow and firn hydrology sensor owing to its suitability for (1) sensing lateral and vertical liquid water flows directly and minimally invasively, (2) complementing established observational programs through multidimensional spatial mapping of meltwater fluxes or liquid water content and (3) monitoring autonomously at a low cost. Future work should focus on the development of self-potential sensor arrays compatible with existing weather and snow monitoring technology and observational programs, and the integration of self-potential data into analytical frameworks.ISSN:1994-0416ISSN:1994-042

Occasional papers

no.4 (1994

A ‘driving force’ in developing the nation’s forests: The McIntire-Stennis Cooperative Forestry Research Program.

The McIntire-Stennis (M-S) Cooperative Forestry Research Program has provided fundamental support for creating and strengthening forestry research and graduate training efforts at colleges and universities across the nation for nearly 50 years. M-S funding has helped produce thousands of forestry scientists and other research professionals, and M-S–supported research has provided critical basic understanding and applied solutions to extend the benefits that flow from forests and related rangelands across the nation over time. The 1962 legislation that created the M-S program authorized funding of up to one-half of the funds appropriated for federal forestry research conducted directly by the USDA. Throughout the program’s history, however, M-S appropriations have been far below the authorized level. In 2012, the M-S program’s 50th anniversary will be celebrated. Congress and the President therefore have a truly significant “golden anniversary” opportunity to strengthen the nation’s investment in research and training that represents an essential and powerful “driving force behind progress” in sustaining forests for ecological, economic, and social benefits for present and future generations

Surface Characterization of Polycarbonate Parts from Selective Laser Sintering

Surfaces of polycarbonate Selective Laser Sintering parts are investigated to determine the characteristics affecting part quality. Surfaces are obtained from experiments by varying four factors, namely, layer thickness, laser power, part orientation, and build angle. First, spatial modes on SLS surfaces are decomposed using a qualitative spectral analysis in an attempt to find their origins. Thermal modes on the top surfaces of polycarbonate SLS parts result in the other modes being obscured; melting and part curl are concluded to be the dominant modes on these surfaces. Furthermore, surface modes resulting from building the part at an angle to the powder bed are identified and modeled. Then, mathematical measures are computed for the surfaces to determine surface precision quantitatively. An analysis-of-variance study is performed to reveal the trends in surface precision with respect to control factors. Surface precision is shown to change significantly with laser power and part orientation, and trade-offs with part strength are presented.Mechanical Engineerin

Seismic study of stellar convective cores

It has been shown that a discontinuity in the derivatives of the sound speed at the edge of the convective regions inside a star gives rise to a characteristic oscillatory signal in the frequencies of stellar oscillations. This oscillatory signal has been suggested as a means to study the base of the outer convection zone in low mass stars and possibly the outer edge of the convective core in high mass stars. Using stellar models we show that because of a phenomenon similar to aliasing in Fourier transform, it may not be possible to use this signal to detect the convective core. Nevertheless, it may be possible to determine the size of convective cores using the frequency separation \nu_{n+1,l}-\nu_{n,l}.Comment: Accepted for publication in A &