Accreting protoplanets in the LkCa 15 transition disk.

Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1,900 exoplanets have now been discovered and confirmed, none are still in the process of formation. Transition disks, protoplanetary disks with inner clearings best explained by the influence of accreting planets, are natural laboratories for the study of planet formation. Some transition disks show evidence for the presence of young planets in the form of disk asymmetries or infrared sources detected within their clearings, as in the case of LkCa 15 (refs 8, 9). Attempts to observe directly signatures of accretion onto protoplanets have hitherto proven unsuccessful. Here we report adaptive optics observations of LkCa 15 that probe within the disk clearing. With accurate source positions over multiple epochs spanning 2009-2015, we infer the presence of multiple companions on Keplerian orbits. We directly detect Hα emission from the innermost companion, LkCa 15 b, evincing hot (about 10,000 kelvin) gas falling deep into the potential well of an accreting protoplanet.

Water vapour and hydrogen in the terrestrial-planet-forming region of a protoplanetary disk.

Planetary systems (ours included) formed in disks of dust and gas around young stars. Disks are an integral part of the star and planet formation process, and knowledge of the distribution and temperature of inner-disk material is crucial for understanding terrestrial planet formation, giant planet migration, and accretion onto the central star. Although the inner regions of protoplanetary disks in nearby star-forming regions subtend only a few nano-radians, near-infrared interferometry has recently enabled the spatial resolution of these terrestrial zones. Most observations have probed only dust, which typically dominates the near-infrared emission. Here I report spectrally dispersed near-infrared interferometric observations that probe the gas (which dominates the mass and dynamics of the inner disk), in addition to the dust, within one astronomical unit (1 au, the Sun-Earth distance) of the young star MWC 480. I resolve gas, including water vapour and atomic hydrogen, interior to the edge of the dust disk; this contrasts with results of previous spectrally dispersed interferometry observations. Interactions of this accreting gas with migrating planets may lead to short-period exoplanets like those detected around main-sequence stars. The observed water vapour is probably produced by the sublimation of migrating icy bodies, and provides a potential reservoir of water for terrestrial planets.

The good ol' days is now: trends in operative experience of general surgical residents over 25 years.

To define the changing trends in operative experience of general surgery residents, the records of all residents completing our training program from 1964-1987 were reviewed. Except for a slight decline in operative experience in head and neck and gastric surgery, the experience in other primary component procedures either remained stable (major breast, esophagus, intestine, colon, pancreas, spleen and endocrine) or increased (minor breast, anorectal, hernia, biliary, vascular and trauma). A rich experience in secondary component procedures was maintained in thoracic, pediatric and plastic surgery, all of which are services within the department of surgery. A relatively low but stable experience in gynecology, neurosurgery, orthopaedics and urology has been reported, which did not change when these disciplines became separate departments. Finally, there has been a dramatic increase in endoscopic procedures performed in the surgery department despite the presence of endoscopic services in other departments. It is believed that such an institutional review of surgical resident caseload over time will be of help not only to program directors but also to accrediting and certifying organizations concerned with surgical training programs and their graduates.

Economics of trauma in a small academic medical center.

The recent changes in the mechanisms of health care funding have complicated trauma care and trauma center development. Hard data are needed on the current financial position of trauma care to plan for the future. To reduce the cost of trauma care without sacrificing the quality, we must know how the trauma dollar is spent. We reviewed the records of 100 random admissions to the trauma service of our institution in 1985. The records were examined for length of stay (LOS), intensive care unit length of stay (ICU-LOS), total hospital bill, types of third-party coverage, and overall collection rate. The hospital bill was broken down to identify the origins of trauma costs. To provide a control group, 100 patients admitted to the general surgical service and 100 other admissions were also analyzed. Trauma patients had greater LOS, ICU-LOS, total bills, and costs per day. Blunt trauma resulted in a greater LOS than penetrating trauma, but similar total bills. The collection rate from the blunt trauma patients was significantly greater. The greatest differences between trauma patients and others in resource utilization are the result of longer ICU-LOS and greater use of blood products. We did not identify any sites of potentially significant cost cutting that would not compromise patient care.