Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C.

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ~40 keV. SN 2014C shows ordinary explosion parameters (Ek ~ 1.8 × 1051 erg and Mej ~ 1.7 M⊙). However, over an ~1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of ~1 M⊙of hydrogen-rich material at ~6 × 1016 cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ~10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 103-104 years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.

Slowly fading super-luminous supernovae that are not pair-instability explosions.

Super-luminous supernovae that radiate more than 10(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of (56)Ni are synthesized; this isotope decays to (56)Fe via (56)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10(-6) times that of the core-collapse rate.

An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core.

The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decay of the light curve follow the predicted mass accretion rate and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about two million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.

X-ray illumination of the ejecta of supernova 1987A.

When a massive star explodes as a supernova, substantial amounts of radioactive elements--primarily (56)Ni, (57)Ni and (44)Ti--are produced. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.

A relativistic type Ibc supernova without a detected gamma-ray burst.

Long duration gamma-ray bursts (GRBs) mark the explosive death of some massive stars and are a rare sub-class of type Ibc supernovae. They are distinguished by the production of an energetic and collimated relativistic outflow powered by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested in the pulse of gamma-rays and a long-lived radio afterglow. Until now, central-engine-driven supernovae have been discovered exclusively through their gamma-ray emission, yet it is expected that a larger population goes undetected because of limited satellite sensitivity or beaming of the collimated emission away from our line of sight. In this framework, the recovery of undetected GRBs may be possible through radio searches for type Ibc supernovae with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. A comparison with our radio survey of type Ibc supernovae reveals that the fraction harbouring central engines is low, about one per cent, measured independently from, but consistent with, the inferred rate of nearby GRBs. Independently, a second mildly relativistic supernova has been reported.

Supernovae, an accelerating universe and the cosmological constant.

Observations of supernova explosions halfway back to the Big Bang give plausible evidence that the expansion of the universe has been accelerating since that epoch, approximately 8 billion years ago and suggest that energy associated with the vacuum itself may be responsible for the acceleration.

The Earth's elements.

The elements that make up the earth and its inhabitants were created by earlier generations of stars.

Inflammatory aneurysm of the ascending aorta; an unreported entity.

A 69-year-old woman with an enlarging ascending aortic aneurysm is presented. At operation, the patient was noted to have extensive peri-aneurysmal fibrosis and inflammation with a 1 cm thick aneurysm wall. Pathologic examination was consistent with inflammatory aneurysm. Inflammatory aneurysms of the thoracic aorta are uncommon and this may be the first patient with this process involving the ascending aorta with both operative and pathologic findings.

Spinal cord ischemia: an evaluation of pharmacologic agents in minimizing paraplegia after aortic occlusion.

Superoxide dismutase (SOD), barbiturates, and hypothermic crystalloid were evaluated for their effectiveness in minimizing ischemic damage to the spinal cord at 40 minutes of aortic occlusion. Forty-two dogs underwent proximal and distal thoracic aortic occlusion for 40 minutes with infusion of test agents into the occluded segment. The dogs were divided into six groups. Group 1 (n = 6) served as control. Group 2 (n = 6) received hypothermic crystalloid. Group 3 (n = 6) animals received thiopental. Group 4 (n = 7) received SOD. Group 5 (n = 9) received hypothermic crystalloid and thiopental. Group 6 (n = 8) received hypothermic crystalloid, thiopental and SOD. The animals were observed for neurologic deficit for 72 hours. In group 1, six of six dogs showed complete paralysis. Five of six dogs from group 2, five of six dogs from group 3, and five of seven dogs from group 4 showed complete paraplegia. The remaining dogs in these groups showed varying degrees of recovery. Four of nine dogs in group 5 had complete paraplegia, three dogs showed varying degrees of recovery, and two dogs had no neurologic deficit. In group 6, one dog had complete paraplegia, three had partial recovery, and four had no neurologic deficit. Group 6 was the only group that showed significantly less late neurologic impairment than the control group. We concluded that although cold perfusion, barbiturates, and SOD are not protective when used alone, they are effective when all are used in combination. The combination of cold perfusion, barbiturates, and SOD significantly decreases neurologic deficit after 40 minutes of aortic occlusion.

Acute aortic rupture from cross clamp injury.

We report a case of transmural disruption and perforation of the abdominal aorta secondary to clamp injury. The literature is reviewed in reference to the traumatic effects of vascular clamps. Steps are outlined to reduce the risk of this injury.

Ocular manifestations of carotid artery atheroma.

Although carotid endarterectomy (CE) is recommended in appropriate patients with bifurcation atheroma for the prevention of stroke, these patients are also at risk for visual loss, either temporary or permanent. The presentations of patients undergoing 512 consecutive CEs were reviewed to determine the preoperative frequency and risks of ocular disturbances. Visual symptoms occurred in 131 patients (25%). Temporary, monocular blindness (amaurosis fugax, AF) was reported by 99 patients (19%). Concomitant neurologic symptoms were present in 33 (33%) of the patients with AF, and carotid artery stenoses of greater than 75% diameter were documented in 82 (83%) of these patients. No visual deficits were observed following operation. Permanent visual loss ranging from scotoma to complete blindness was documented in 32 patients (6.2%). The permanent deficits were due to retinal artery occlusions (RAO) in 20 patients (4%), ischemic optic neuropathy (ION) in eight patients (1.5%), and homonymous hemianopsia (HH) in four patients (0.7%). Visual loss occurred without any warning in 27 of these 32 cases (84%). The five cases with warning had multiple episodes of AF and then sustained RAO and blindness. Neurologic symptoms occurred concomitantly but not prior to visual symptoms in 7 of the 12 patients (58%) with ION and HH. Stenoses greater than 75% were present in 22 of 32 cases (69%) and in every case of ION. Operation had no effect on the visual deficit. Permanent visual loss occurred in a significant number of patients with carotid atheroma (6.2%). Warning in the form of visual prodroma is uncommon in these patients (16%).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute thrombosis of abdominal aortic aneurysm subsequent to Heimlich maneuver: a case report.

We report a case of acute thrombosis of an abdominal aortic aneurysm secondary to a correctly applied and successful Heimlich maneuver. Although the Heimlich maneuver is generally safe and effective, this possible catastrophic consequence needs to be recognized.

Case report: late rupture of a thrombosed abdominal aortic aneurysm.

A patient with a thrombosed aortic aneurysm, proved by angiography, died of aortic rupture 5 1/2 months after thrombosis. To our knowledge, this is the first reported case of late rupture of a thrombosed aortic aneurysm. This occurrence raises questions about the long-term safety of nonresective treatment of aortic aneurysms.

Toward strategies for cost containment in surgical patients.

The University of Rochester, Department of Surgery, in response to an experimental community-wide limit on hospital budgets, studied high-cost general surgical patients as a potential source of leverage for containment of hospital costs. It was found that a small number of patients impact significantly on hospital costs. In 1980, 3935 patients at Strong Memorial Hospital (SMH) had at least one contact with a general surgical patient care or intensive care unit; 261 patients (6.6%) had total 1980 charges of more than $20,000 each. They contributed 32% of the total of both general surgical charges and patient days. A subset of 2021 patients was selected to represent more precisely the general surgical patient. The 85 high-cost patients (4.2%) of this subset were chosen for intensive study. These patients generated a significant and disproportionate per cent of total (2021) general surgical charges (26.8%) and hospital days (27.6%). Average total charges were more than 8 times those of the complementary general surgical subset (1936). Nineteen of the 85 patients (22.3%) died in the hospital and 42 patients (49.4%) were dead within 2 1/2 years. Forty patients (of the 85) were then further identified as "complex", based on multiple, usually unrelated, illnesses and multiple annual admissions. Tending to be elderly with poor prognoses, 60% of them had died by April 1983. The major criterion of complexity was the lack of a well-focused medical problem; the cure for one problem simply relinquished primacy to another. A parallel study of hospital ancillary procedures disclosed a similar high-cost pattern. Of approximately 4000 ancillary procedures, 100 (2.5%) had annual charges of $100,000 or over, accounting for two-thirds of total 1980 ancillary charges. Roughly 20% of a single patient's ordered procedures accounted for 80% of the patient's ancillary charges, thus allowing concentrated study of a relatively small number of charges. Means for cost containment may be applied logically to the high-cost patient and particularly toward the complex patient. The complex patient is especially suited for consideration, since it is postulated that these patients are endemic to all general hospitals and to all clinical services. Strategies to be developed should include: 1) a managerial system in which physicians have an incentive to contain costs, 2) an online data system, 3) an accurate, efficient way to identify prospective high-cost and complex patients and, 4) awareness by physicians, patients, and society that less expensive modes of diagnosis and therapy are an appropriate response to rationed health resources.

Upper rib fractures and mediastinal widening: indications for aortography.

Survival of patients with posttraumatic thoracic aortic rupture depends on early diagnosis. It is frequently stated that fracture of the first or second ribs and mediastinal widening are findings suggestive of thoracic aortic rupture. We found that the probability of sustaining thoracic aortic rupture is the same for patients with upper rib fractures as for those with other rib fractures (1/64 versus 5/149; p = 0.85). Also, our data fail to show a statistical difference in the incidence of thoracic aortic rupture associated with upper (first and second) rib fractures compared with no rib fracture at all (1/64 versus 9/304; p = 0.85). Thus, patients with thoracic aortic rupture are not more likely to have rib fractures (7/21 versus 14/21; p = 0.15), and if a rib fracture is present, the probability of it being at the upper level is the same as that for a fracture at any other level (1/7 versus 6/7; p = 0.06). Ratios of mediastinal width to chest width were used as a measure of mediastinal widening, and were found to be an accurate predictor of thoracic aortic rupture. Ratios greater than 0.28 at the aortic knob were 100% specific and 85% sensitive for this condition.

Traumatic aortic rupture: plain radiographic findings.

The plain radiographic findings on 20 patients with traumatic aortic rupture were analyzed. A mediastinal-width to chest-width (M/C) ratio was calculated at three thoracic levels and compared to two matched groups of patients without aortic tears. Defining an M/C ratio of 0.25 or larger at the level of the aortic arch as abnormal would identify 95% of cases with ruptured aortas, and result in 25% false-positive studies in traumatized patients. A ratio greater than 0.28 retains 85% sensitivity for aortic rupture while increasing specificity to 100%. An analysis of the prevalence and location of rib fractures showed that there was little relation between the presence of fracture and existence of an aortic tear. Therefore, an acutely injured patient with an M/C ratio of greater than 0.25 should be considered highly likely to have an aortic rupture.