Binary Encounters With Supermassive Black Holes: Zero-Eccentricity LISA Events

Current simulations of the rate at which stellar-mass compact objects merge with supermassive black holes (called extreme mass ratio inspirals, or EMRIs) focus on two-body capture by emission of gravitational radiation. The gravitational wave signal of such events will likely involve a significant eccentricity in the sensitivity range of the Laser Interferometer Space Antenna (LISA). We show that tidal separation of stellar-mass compact object binaries by supermassive black holes will instead produce events whose eccentricity is nearly zero in the LISA band. Compared to two-body capture events, tidal separations have a high cross section and result in orbits that have a large pericenter and small apocenter. Therefore, the rate of interactions per binary is high and the resulting systems are very unlikely to be perturbed by other stars into nearly radial plunges. Depending on the fraction of compact objects that are in binaries within a few parsecs of the center, the rate of low-eccentricity LISA events could be comparable to or larger than the rate of high-eccentricity events.Comment: Final accepted version: ApJ Letters 2005, 631, L11

Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming - April 1993

Large coal resources occur in the Upper Cretaceous Williams Fork Formation and lower Tertiary Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mainly subbituminous to high-volatile B bituminous and have average gas contents of less than 100 to 200 ft3/ton (<3.12 to 6.24 m3/t). Coalbed methane resources total xx Tcf (x.xx Tm3) and are xx.xx Tcf (xxx Bm3) at drilling depths of less than 6,000 ft (<1,830 m). More than 85 percent of them are in the Williams Fork. The basin's cumulative gas/water ratio is approximately 15 ft3/bbl (2.7 m3/m3). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern margins of the basin. Prospective Williams Fork and Fort Union coals, respectively, lie basinward in association with the Cedar Mountain fault system and westward along Cherokee Arch into the Powder Wash field area. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane productivity model is proposed whose essential elements are: ground-water flow through thick coals of high rank, perpendicular to no-flow boundaries and conventional trapping along them.Bureau of Economic Geolog

Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming

Geologic and hydrologic analysis of the Upper Cretaceous Mesaverde Group shows that the major controls on the production of coalbed methane are: structural configuration, coal occurrence, gas content, hydrodynamics, and water production. Steep structural dip (500 ft/mi) and coal occurrence limit economic exploration to the eastern and southeastern margins of the basin. Coal resources occur mainly in the lower Williams Fork Formation (upper Mesaverde) in the eastern part of the basin. Most coal beds are high-volatile C to B bituminous rank and have gas contents of less than 200 scf/ton. Moreover, Williams Fork coals do not extend westward to the area of highest thermal maturity. Thus, they could not serve as conduits for long-distance migration of gas. Regionally, groundwater flows westward from an eastern recharge area across an area of low thermal maturity up the coal-rank gradient. Consequently, only a relatively small volume of gas may be available to be swept basinward for conventional trapping. The most prospective areas lie basinward, northwest of Craig, Colorado, on the upflow, downward side of a major fault zone. Gas contents in some coal beds on the downthrown side of the fault exceed 400 scf/ton. The Mesaverde is a thick, regionally interconnected aquifer system of high transmissivity, yielding large volumes of water. Paradoxically, coalbed permeabilities of 10's to 1,000's of md may be too high for economic gas production. To date, high water production and low gas content at the basin margins have limited coalbed activity in the Sand Wash Basin. Major Tertiary coal resources occur in the lower part of the Paleocene Fort Union Formation.Bureau of Economic Geolog

Four-Body Effects in Globular Cluster Black Hole Coalescence

In the high density cores of globular clusters, multibody interactions are expected to be common, with the result that black holes in binaries are hardened by interactions. It was shown by Sigurdsson & Hernquist (1993) and others that 10 solar mass black holes interacting exclusively by three-body encounters do not merge in the clusters themselves, because recoil kicks the binaries out of the clusters before the binaries are tight enough to merge. Here we consider a new mechanism, involving four-body encounters. Numerical simulations by a number of authors suggest that roughly 20-50% of binary-binary encounters will eject one star but leave behind a stable hierarchical triple. If the orbital plane of the inner binary is strongly tilted with respect to the orbital plane of the outer object, a secular Kozai resonance, first investigated in the context of asteroids in the Solar System, can increase the eccentricity of the inner body significantly. We show that in a substantial fraction of cases the eccentricity is driven to a high enough value that the inner binary will merge by gravitational radiation, without a strong accompanying kick. Thus the merged object remains in the cluster; depending on the binary fraction of black holes and the inclination distribution of newly-formed hierarchical triples, this mechanism may allow massive black holes to accumulate through successive mergers in the cores of globular clusters. It may also increase the likelihood that stellar-mass black holes in globular clusters will be detectable by their gravitational radiation.Comment: Submitted to ApJ Letters (includes emulateapj.sty

Mechanism of action of VP1-001 in cryAB(R120G)-associated and age-related cataracts

PurposeWe previously identified an oxysterol, VP1-001 (also known as compound 29), that partially restores the transparency of lenses with cataracts. To understand the mechanism of VP1-001, we tested the ability of its enantiomer, ent-VP1-001, to bind and stabilize αB-crystallin (cryAB) in vitro and to produce a similar therapeutic effect in cryAB(R120G) mutant and aged wild-type mice with cataracts. VP1-001 and ent-VP1-001 have identical physicochemical properties. These experiments are designed to critically evaluate whether stereoselective binding to cryAB is required for activity.MethodsWe compared the binding of VP1-001 and ent-VP1-001 to cryAB using in silico docking, differential scanning fluorimetry (DSF), and microscale thermophoresis (MST). Compounds were delivered by six topical administrations to mouse eyes over 2 weeks, and the effects on cataracts and lens refractive measures in vivo were examined. Additionally, lens epithelial and fiber cell morphologies were assessed via transmission electron microscopy.ResultsDocking studies suggested greater binding of VP1-001 into a deep groove in the cryAB dimer compared with ent-VP1-001. Consistent with this prediction, DSF and MST experiments showed that VP1-001 bound cryAB, whereas ent-VP1-001 did not. Accordingly, topical treatment of lenses with ent-VP1-001 had no effect, whereas VP1-001 produced a statistically significant improvement in lens clarity and favorable changes in lens morphology.ConclusionsThe ability of VP1-001 to bind native cryAB dimers is important for its ability to reverse lens opacity in mouse models of cataracts

Short-Term Impacts of 2017 Western North American Wildfires On Meteorology, the Atmosphere\u27s Energy Budget, and Premature Mortality

Western North American fires have been increasing in magnitude and severity over the last few decades. The complex coupling of fires with the atmospheric energy budget and meteorology creates short-term feedbacks on regional weather altering the amount of pollution to which Americans are exposed. Using a combination of model simulations and observations, this study shows that the severe fires in the summer of 2017 increased atmospheric aerosol concentrations leading to a cooling of the air at the surface, reductions in sensible heat fluxes, and a lowering of the planetary boundary layer height over land. This combination of lower-boundary layer height and increased aerosol pollution from the fires reduces air quality. We estimate that from start of August to end of October 2017, ~400 premature deaths occurred within the western US as a result of short-term exposure to elevated PM2.5 from fire smoke. As North America confronts a warming climate with more fires the short-term climate and pollution impacts of increased fire activity should be assessed within policy aimed to minimize impacts of climate change on society

Toward a descriptive model of solar particles in the heliosphere

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made

Right Ventricular Tissue Doppler in Space Flight

Tissue Doppler (TD) registers movement of a given sample of cardiac tissue throughout the cardiac cycle. TD spectra of the right ventricle (RV) were obtained from a long-duration ISS crewmember as a portion of an ongoing experiment ("Braslet" test objective). To our knowledge, this is the first report of RV TD conducted in space flight, and the data represent reproducibility and fidelity of this application in space and serve as the first "space normal" data set. Methods RV TD was performed by astronaut scientists remotely guided by an ultrasound expert from Mission Control Center, Houston, TX. In four of the subjects, RV TD was acquired from the free wall near the tricuspid annulus in two separate sessions 4 to 7 days apart. A fifth subject had only one session. All digital DICOM frames were exported for off-line analysis. Systolic (S ), early diastolic (E ) and late diastolic (A ) velocities were measured. RV Tei-index was calculated using diastolic and systolic time intervals as a combined measure of myocardial performance. Results and Discussion The mean values from the first 4 subjects (8 sessions) were used as the on-orbit reference data, and subject 5 was considered as a hypothetical patient for comparison (see Table). The greatest difference was in the early diastolic A (31 %) yet the standard deviation (a) for A amongst the reference subjects was 2.25 (mean = 16.02). Of interest is the Tei index, a simple and feasible indicator of overall ventricular function; it was similar amongst all the subjects. The late diastolic A seems to compensate for the variance in E . Normal Tei index for the RV is < 0.3, yet our data show all but one subject consistently above this level, notwithstanding their nominal responses to daily exercise in microgravity. These data remind us that the physiology of RV preload in altered gravity environments is still not completely understood