Satellite and ground radiotracking of elk

Radiotracking and monitoring of free-living animals in natural environments is providing an effective new technique for acquiring information on biological processes, including animal orientation and navigation. To test the practicability of extending the technique by using satellite systems for tracking animals, a female elk was instrumented with an electronic collar. It contained both the Interrogation Recording Location System (IRLS) transponder and a Craighead-Varney ground-tracking transmitter. The elk was successfully tracked and monitored by satellite during month of April 1970. This was the first time an animal had been tracked by satellite on the surface of the earth

Fabrication of small laterally patterned multiple quantum wells

A technique of high voltage electron beam lithography and BCI_3/Ar reactive ion etching for laterally patterning GaAs/Al_0_3 Ga_(0.7) As multiple quantum wells is described. The resulting structures were analyzed using scanning electron microscopy and a novel reflection electron microscopy technique, and their geometries are shown. Narrow columns 40 nm in diameter etched 230 nm through the quantum wells were reproducibly fabricated

Investigating the effect of auxiliary objectives for the automated grading of learner english speech transcriptions

We address the task of automatically grading the language proficiency of spontaneous speech based on textual features from automatic speech recognition transcripts. Motivated by recent advances in multi-task learning, we develop neural networks trained in a multi-task fashion that learn to predict the proficiency level of non-native English speakers by taking advantage of inductive transfer between the main task (grading) and auxiliary prediction tasks: morpho-syntactic labeling, language modeling, and native language identification (L1). We encode the transcriptions with both bi-directional recurrent neural networks and with bi-directional representations from transformers, compare against a feature-rich baseline, and analyse performance at different proficiency levels and with transcriptions of varying error rates. Our best performance comes from a transformer encoder with L1 prediction as an auxiliary task. We discuss areas for improvement and potential applications for text-only speech scoring.Cambridge Assessmen

50-Year Golden Eagle Nesting Trends In South-Central Montana

Golden Eagle (Aquila chrysaetos) migration counts in the western North America have shown a significant negative trend in recent years. However, the causes of these declines are unknown and it remains unclear if declining migration counts correlate to a declining population or changes in migratory behavior. Long-term research on nesting Golden Eagle populations is lacking and is needed to properly assess the current Golden Eagle population status in many areas. In 1962, intensive monitoring efforts were initiated in a roughly 1200-mi2 study area in south-central Montana. The objectives were, among other things, to determine density and productivity of Golden Eagles. This area was re-surveyed in the mid 1990s to begin looking at long-term population trends. In 2009, we initiated a multi-year effort to investigate potential changes in the nesting trends in the same study area over a half a century. The data collected to date indicate an increase in the nesting density, similar nest success rates, and a decrease in productivity when compared with both the 1960’s and 1990s studies. The longevity of data collected in this study area allows for one of the longestterm comparisons for Golden Eagle nesting density and success in the West and provides invaluable insights into the status of nesting Golden Eagles in this region

Avian Scavengers And Lead Rifle Ammunition: Where We’re At, Challenges, And Solutions

Birds have long been recognized at risk of lead poisoning from ammunition sources, but only in recent years has rifle ammunition been identified as a source of lead toxicity in raptors and other scavenging birds. Several studies have indicated increased lead exposure in eagles but the implications to population dynamics remain unclear. We have monitored blood lead levels of Common Ravens (Corvus corax), Bald Eagles (Haliaeetus luecocehpalus), and Golden Eagles (Aquila chrysaetos) in Jackson Hole, Wyoming, since 2004 to investigate effects of spent rifle ammunition on avian scavengers. Data from ravens and Bald Eagles indicated a strong relationship between big-game hunting seasons and elevated blood lead levels. In 2009, we initiated a voluntary non-lead ammunition program in collaboration with Grand Teton National Park and the National Elk Refuge. Free, non-lead ammunition was distributed to hunters in the area. Hunter surveys indicated that 24 percent of successful hunters on the Park and Refuge used non-lead ammunition and we detected a 28-percent drop in the mean lead levels of ravens monitored from previous years after the harvest totals were controlled for. We continued the voluntary program in 2010 by selling reduced-priced non-lead ammunition, and there was greater participation in the voluntary non-lead program (33%). Further, we have outfitted 13 Bald Eagles with satellite transmitters to document the potential geographic impact our local hunting season has on the continental eagle population and found that 90 percent of eagles outfitted during the big-game hunting season breed/ summer in central Canada

Ultranarrow conducting channels defined in GaAs-AlGaAs by low-energy ion damage

We have laterally patterned the narrowest conducting wires of two-dimensional electron gas (2DEG) material reported to date. The depletion induced by low-energy ion etching of GaAs-AlGaAs 2DEG structures was used to define narrow conducting channels. We employed high voltage electron beam lithography to create a range of channel geometries with widths as small as 75 nm. Using ion beam assisted etching by Cl2 gas and Ar ions with energies as low as 150 eV, conducting channels were defined by etching only through the thin GaAs cap layer. This slight etching is sufficient to entirely deplete the underlying material without necessitating exposure of the sidewalls that results in long lateral depletion lengths. At 4.2 K, without illumination, our narrowest wires retain a carrier density and mobility at least as high as that of the bulk 2DEG and exhibit quantized Hall effects. Aharonov–Bohm oscillations are seen in rings defined by this controlled etch-damage patterning. This patterning technique holds promise for creating one-dimensional conducting wires of even smaller sizes

Dissipation in nanocrystalline-diamond nanomechanical resonators

We have measured the dissipation and frequency of nanocrystalline-diamond nanomechanical resonators with resonant frequencies between 13.7 MHz and 157.3 MHz, over a temperature range of 1.4–274 K. Using both magnetomotive network analysis and a time-domain ring-down technique, we have found the dissipation in this material to have a temperature dependence roughly following T^(0.2), with Q^(–1) ≈ 10^(–4) at low temperatures. The frequency dependence of a large dissipation feature at ~35–55 K is consistent with thermal activation over a 0.02 eV barrier with an attempt frequency of 10 GHz

First-principles calculation of mechanical properties of Si <001> nanowires and comparison to nanomechanical theory

We report the results of first-principles density functional theory calculations of the Young's modulus and other mechanical properties of hydrogen-passivated Si nanowires. The nanowires are taken to have predominantly {100} surfaces, with small {110} facets according to the Wulff shape. The Young's modulus, the equilibrium length and the constrained residual stress of a series of prismatic beams of differing sizes are found to have size dependences that scale like the surface area to volume ratio for all but the smallest beam. The results are compared with a continuum model and the results of classical atomistic calculations based on an empirical potential. We attribute the size dependence to specific physical structures and interactions. In particular, the hydrogen interactions on the surface and the charge density variations within the beam are quantified and used both to parameterize the continuum model and to account for the discrepancies between the two models and the first-principles results.Comment: 14 pages, 10 figure