Current Challenges Can Help Fuel Future Opportunities

Native juniper trees and invasive plants pose an expanding threat to the survival of the sagebrush ecosystem in arid western rangelands. As the trees mature, they compete with other native plants that are valuable food sources for wildlife and cattle. After these plants die back, the bare patches of soil that remain are vulnerable to erosion and encroachment from other species like cheatgrass, an invasive nonnative annual that fuels wildfires. Wildfires threaten livestock ranches, are suppressed in large part by efforts funded with taxpayer dollars, and increase the probability that invasive plants will spread and thrive in the postfire landscape. So while western juniper, pinyon pine, and other similar native trees have a role to play in this ecosystem, the thickets that are rapidly spreading across the rangelands need to be brought under control. Fortunately, the challenge these trees present to healthy rangelands also creates an opportunity for using them as a feedstock for renewable jet fuel production. And this new opportunity means that western states could significantly contribute to meeting national goals for the production of renewable bioenergy in the United States—and help the U.S. military develop homegrown and sustainable sources of alternative biofuels for powering its assortment of vehicles, planes, and ships. Agricultural Research Service researchers already have a framework in place for tackling the many issues that need to be resolved before turning a tree into a gallon of renewable fuel. In 2010, U.S. Department of Agriculture Secretary Tom Vilsack created five Regional Biomass Research Centers to maximize existing USDA research resources for bioenergy development. The goal of this effort is to develop sustainable, regional approaches for producing feedstocks so that rural communities across the country have opportunities to participate in the emerging biofuels and biobased-products economy. (See “ARS and the Regional Biomass Research Centers,” Agricultural Research, September 2012.

Measuring the Spins of Stellar Black Holes: A Progress Report

We use the Novikov-Thorne thin disk model to fit the thermal continuum X-ray spectra of black hole X-ray binaries, and thereby extract the dimensionless spin parameter a* = a/M of the black hole as a parameter of the fit. We summarize the results obtained to date for six systems and describe work in progress on additional systems. We also describe recent methodological advances, our current efforts to make our analysis software fully available to others, and our theoretical efforts to validate the Novikov-Thorne model.Comment: 6 pages, conference proceedings, X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives, AIP, eds. A. Comastri et al.; list of authors revise

Confirmation Via the Continuum-Fitting Method that the Spin of the Black Hole in Cygnus X-1 is Extreme

In Gou et al. (2011), we reported that the black hole primary in the X-ray binary Cygnus X-1 is a near-extreme Kerr black hole with a spin parameter a*>0.95(3{\sigma}). We confirm this result while setting a new and more stringent limit: a*>0.983 at the 3{\sigma}(99.7%) level of confidence. The earlier work, which was based on an analysis of all three useful spectra that were then available, was possibly biased by the presence in these spectra of a relatively strong Compton power-law component: The fraction of the thermal seed photons scattered into the power law was f_s=23-31%, while the upper limit for reliable application of the continuum-fitting method is f_s<25%. We have subsequently obtained six additional spectra of Cygnus X-1 suitable for the measurement of spin. Five of these spectra are of high quality with f_s in the range 10% to 19%, a regime where the continuum-fitting method has been shown to deliver reliable results. Individually, the six spectra give lower limits on the spin parameter that range from a*>0.95 to a*>0.98, allowing us to conservatively conclude that the spin of the black hole is a*>0.983 (3{\sigma}).Comment: 14 pages in emulated ApJ format, including 6 figures and 4 tables, ApJ in press. Discussion on the pileup effect to our spin measurement is added, including a subsection and a new figure, to reflect the referee's comments; the conclusions are unchange

The Formation and Coarsening of the Concertina Pattern

The concertina is a magnetization pattern in elongated thin-film elements of a soft material. It is a ubiquitous domain pattern that occurs in the process of magnetization reversal in direction of the long axis of the small element. Van den Berg argued that this pattern grows out of the flux closure domains as the external field is reduced. Based on experimental observations and theory, we argue that in sufficiently elongated thin-film elements, the concertina pattern rather bifurcates from an oscillatory buckling mode. Using a reduced model derived by asymptotic analysis and investigated by numerical simulation, we quantitatively predict the average period of the concertina pattern and qualitatively predict its hysteresis. In particular, we argue that the experimentally observed coarsening of the concertina pattern is due to secondary bifurcations related to an Eckhaus instability. We also link the concertina pattern to the magnetization ripple and discuss the effect of a weak (crystalline or induced) anisotropy

The Extreme Spin of the Black Hole in Cygnus X-1

The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations. We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole's accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk. Assuming that the spin axis of the black hole is aligned with the orbital angular momentum vector, we have determined that Cygnus X-1 contains a near-extreme Kerr black hole with a spin parameter a/M>0.95 (3\sigma). For a less probable (synchronous) dynamical model, we find a/M>0.92 (3\sigma). In our analysis, we include the uncertainties in black hole mass, orbital inclination angle and distance, and we also include the uncertainty in the calibration of the absolute flux via the Crab. These four sources of uncertainty totally dominate the error budget. The uncertainties introduced by the thin-disk model we employ are particularly small in this case given the extreme spin of the black hole and the disk's low luminosity.Comment: Paper III of three papers on Cygnus X-1; 21 pages including 5 figures and 12 tables, ApJ in press. The paper is significantly restructured; two further tests of the robustness of our spin measurement are presented, and our error analysis has been substantially improved; the conclusions are unchange

Mitigation of Shallow Groundwater Nitrate in a Poorly Drained Riparian Area and Adjacent Cropland

Riparian ecosystems, through their unique position in the agricultural landscape and ability to influence nutrient cycles, can potentially reduce NO3 loading to surface and ground waters. The purpose of this study was to determine the fate of NO3 in shallow groundwater moving along a lateral flowpath from a grass seed cropping system through an undisturbed mixed-species herbaceous riparian area. Soil A (30–45 cm) and C horizon (135–150 cm) NO3, dissolved oxygen, and nitrous oxide concentrations were significantly higher in the cropping system than the adjacent riparian area. Nitrate concentrations in both horizons of the riparian soil were consistently at or below 0.05 mg NL-1 while cropping system concentrations ranged from 1 to 12 mg N L-1. Chloride data suggested that NO3 dilution occurred from recharge by precipitation. However, a sharp decrease in NO3/Cl ratios as water moved into the riparian area indicated that additional dilution of NO3 concentrations was unlikely. Riparian area A horizon soil water had higher dissolved organic carbon than the cropping system and when the riparian soil became saturated, available electron acceptors (O2, NO3) were rapidly reduced. Dissolved inorganic carbon was significantly higher in the riparian area than the cropping system for both horizons indicating high biological activity. Carbon limitation in the cropping system may have led to microbial respiration using primarily O2 and to a lesser degree NO3. Within 6 m of the riparian/cropping system transition, NO3 was virtually undetectable

Personality Traits in Juvenile Delinquents: Associations with Peer and Family Relations

Objective: To establish family and peer correlates of personality traits shown to be predictive of future criminal recidivism. Method: 137 incarcerated boys aged 13-18 (x = 16 ± 1.2), 35% black, 21% Hispanic, 43% white, and 1% other completed the Weinberger Adjustment Inventory (WAI) and a psychosocial history obtained by a social worker. Records were summarized using two raters who assigned numerical ratings to dimensions of family and peer relations. Results: As expected, observer ratings of family and peer relationships were correlated with the personality characteristics of distress, denial and restraint as measured by the WAI. Conclusion: Family and peer relations are associated with certain personality traits that are predictive of criminal recidivism in delinquents. This study further expands the knowledge base regarding the social and interpersonal correlates of individual traits predicting criminal recidivism

On the Spin of the Black Hole in IC 10 X-1

The compact X-ray source in the eclipsing X-ray binary IC 10 X–1 has reigned for years as ostensibly the most massive stellar-mass black hole, with a mass estimated to be about twice that of its closest rival. However, striking results presented recently by Laycock et al. reveal that the mass estimate, based on emission-line velocities, is unreliable and that the mass of the X-ray source is essentially unconstrained. Using Chandra and NuSTAR data, we rule against a neutron-star model and conclude that IC 10 X–1 contains a black hole. The eclipse duration of IC 10 X–1 is shorter and its depth shallower at higher energies, an effect consistent with the X-ray emission being obscured during eclipse by a Compton-thick core of a dense wind. The spectrum is strongly disk-dominated, which allows us to constrain the spin of the black hole via X-ray continuum fitting. Three other wind-fed black hole systems are known; the masses and spins of their black holes are high: M ~ 10 - 15M_☉ and ɑ_* > 0.8. If the mass of IC 10 X-1's black hole is comparable, then its spin is likewise high

The Extreme Spin of the Black Hole in Cygnus X-1

The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations. We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole's accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk. Assuming that the spin axis of the black hole is aligned with the orbital angular momentum vector, we have determined that Cygnus X-1 contains a near-extreme Kerr black hole with a spin parameter a * > 0.95 (3σ). For a less probable (synchronous) dynamical model, we find a * > 0.92 (3σ). In our analysis, we include the uncertainties in black hole mass, orbital inclination angle, and distance, and we also include the uncertainty in the calibration of the absolute flux via the Crab. These four sources of uncertainty totally dominate the error budget. The uncertainties introduced by the thin-disk model we employ are particularly small in this case given the extreme spin of the black hole and the disk's low luminosity.Astronom