David E. Barnes

Radar-Enabled Recovery of the Sutter’s Mill Meteorite, a Carbonaceous Chondrite Regolith Breccia

The Meteor That Fell to Earth In April 2012, a meteor was witnessed over the Sierra Nevada Mountains in California. Jenniskens et al. (p. 1583) used a combination of photographic and video images of the fireball coupled with Doppler weather radar images to facilitate the rapid recovery of meteorite fragments. A comprehensive analysis of some of these fragments shows that the Sutters Mill meteorite represents a new type of carbonaceous chondrite, a rare and primitive class of meteorites that contain clues to the origin and evolution of primitive materials in the solar system. The unexpected and complex nature of the fragments suggests that the surfaces of C-class asteroids, the presumed parent bodies of carbonaceous chondrites, are more complex than previously assumed. Analysis of this rare meteorite implies that the surfaces of C-class asteroids can be more complex than previously assumed. Doppler weather radar imaging enabled the rapid recovery of the Sutter’s Mill meteorite after a rare 4-kiloton of TNT–equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand’s parameter = 2.8 ± 0.3). Sutter’s Mill is a regolith breccia composed of CM (Mighei)–type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.

Very Fine and Ultrafine Metals and Ischemic Heart Disease in the California Central Valley 1: 2003–2007

The enhancement of mortality associated with cardiovascular and specifically ischemic heart disease (IHD) has been observed in the southern California Central Valley since at least 1990, and it continues to be a major source of mortality. While there is a strong statistical association of IHD with wintertime PM2.5 mass, the causal agents are uncertain. Medical studies identify some potential causal agents, such as very fine and ultrafine metals, but they have not been fully characterized in most Central Valley regions. To provide improved information on specific and potentially causal agents, a five site aerosol sampling transect was conducted from Redding to Bakersfield during a 17-day period of strong stagnation, January 5–22, 2009. Mass and elemental components were measured every 3 h in eight particle size modes, ranging from 10 to 0.09 μm, while the ultrafine particles (<0.09 μm) were collected on Teflon filters. Ancillary studies were performed including direct upwind–downwind profiles across a heavily traveled secondary street near a stoplight. Very fine and ultrafine iron, nickel, copper, and zinc were identified as vehicular, with the most probable sources being brake drums and pads and the lubrication oil additive zinc thiophosphate. High correlations, many with r 2 > 0.9, were found between these vehicular metals and IHD mortality, enhanced by the meteorology, terrain, and traffic patterns of the southern Central Valley. The braking systems of cars and trucks must now be considered along with direct exhaust emissions in estimating the health impacts from traffic.

Inorganic and organic aerosols downwind of California's Roseville Railyard

Inorganic and organic constituents of aerosols from a major railyard and repair facility were characterized to develop a profile of emissions from railyard activities. The railyard has very consistent downslope winds blowing laterally across the railyard for about 8 hours each night, so two sampling stations were used, one just upwind of the railyard and one downwind adjacent to the railyard fence line. Aerosol samples were collected by rotating drum impactors (DRUM and Lundgren) in up to 9 size modes for 5 weeks in summer and fall of 2005 in tandem with the Roseville Railyard Aerosol Monitoring Project (RRAMP), which measured, black carbon (BC) PM2, as well as NO and NO2. The DRUM aerosol samples were analyzed for mass, optical absorption, and elemental content in 3 h time resolution to allow separation of day and night. Organic analysis was conducted on another set of time integrated size-segregated samples taken by a Lundgren impactor during nighttime hours. The ratio between the downwind versus upwind sites at night was as high as 21.9 (NO, RRAMP) and 6.4 (optical absorption, DRUM) but many species had ratios greater than 2, demonstrating which aerosols arose from railyard activities. The main emissions from the railyard consisted of very fine (0.26 > D p > 0.09 μm) and ultrafine (<0.1 μm) aerosols associated with diesel exhaust such as mass, organic matter, transition metals, and sulfur, the latter 3.3% of the mass since locomotive diesel fuel still contained sulfur. There were also coarse soil aerosols contaminated with anthropogenic metals and petroleum-derived n-alkanes. The aerosol PAH (polycyclic aromatic hydrocarbons) profile showed higher proportions of the heavier PAHs, such as benzo[a]pyrene, compared to diesel truck exhaust on a per unit mass. These aerosols were mostly in the ultrafine (<0.1 μm) size mode, enhancing lung capture. These results and those of Roseville Railyard Aerosol Monitoring Project (RRAMP) largely confirm earlier California Air Resources Boards (ARB) model estimates of health impacts downwind of the railyard based on diesel exhaust, while adding data on very fine transition metals and contaminated soils, potentially important to human health.

ACGME Clinical and Educational Work Hour Standards: Perspectives and Recommendations from Emergency Medicine Educators

Introduction The American College of Emergency Physicians (ACEP) and the Council of Emergency Medicine Residency Directors (CORD) were invited to contribute to the 2016 Accreditation Council for Graduate Medical Education’s (ACGME) Second Resident Duty Hours in the Learning and Working Environment Congress. We describe the joint process used by ACEP and CORD to capture the opinions of emergency medicine (EM) educators on the ACGME clinical and educational work hour standards, formulate recommendations, and inform subsequent congressional testimony. Methods In 2016 our joint working group of experts in EM medical education conducted a consensus-based, mixed-methods process using survey data from medical education stakeholders in EM and expert iterative discussions to create organizational position statements and recommendations for revisions of work hour standards. A 19-item survey was administered to a convenience sample of 199 EM residency training programs using a national EM educational listserv. Results A total of 157 educational leaders responded to the survey; 92 of 157 could be linked to specific programs, yielding a targeted response rate of 46.2% (92/199) of programs. Respondents commented on the impact of clinical and educational work-hour standards on patient safety, programmatic and personnel costs, resident caseload, and educational experience. Using survey results, comments, and iterative discussions, organizational recommendations were crafted and submitted to the ACGME. Conclusion EM educators believe that ACGME clinical and educational work hour standards negatively impact the learning environment and are not optimal for promoting patient safety or the development of resident professional citizenship.

Effects of alloying in the Ce(Pt1−xAux)Si heavy fermion, dense Kondo system

Abstract We report the effects of Au substitution in the Heavy Fermion system Ce(Pt 1−x Au x )Si (0≤x≤0.10), invetigated by x-ray diffraction, electrical resistivity, and dc magnetic susceptibility measurements. CePtSi crystallizes in the LaPtSi-type tetragonal structure with 14 1 md space group and with lattice parameters a =0.4197 nm, and c =1.447 nm. The unit cell volume increases with increasing Au concentration, mainly due to an increase in the c lattice parameter. Electrical resistivity and dc magnetic susceptibility are presented for the temperature range 2 to 350K. We find the possibility of additional electronic mass enhancement in Ce(Pt 0.94 Au 0.06 )Si and a strongly compensated moment (1.3ω B ) for x≥0.08, which we attribute to Kondo compensation.

Tracking sources of fugitive dust at Nipomo Mesa, California

High concentrations of fugitive dust have been experienced in the Nipomo Mesa area, southern San Luis Obispo County, California, to the extent that the California air quality standard for PM10 has been exceeded numerous times. Population centers on the Nipomo Mesa are landward (downwind) of the Oceano Dunes State Vehicular Recreation Area (SVRA)- an off-highway vehicle (OHV) use area on an extensive coastal dune field, as well as undisturbed coastal dunes, agricultural fields, and petroleum coke storage piles at a refinery. All of these sites are potential fugitive dust sources.