r-Process elements from magnetorotational hypernovae.

Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1-3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4-6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7-13. Here we report the element abundance pattern of the extremely metal-poor star SMSS J200322.54-114203.3. We observe a large enhancement in r-process elements, with very low overall metallicity. The element abundance pattern is well matched by the yields of a single 25-solar-mass magnetorotational hypernova. Such a hypernova could produce not only the r-process elements, but also light elements during stellar evolution, and iron-peak elements during explosive nuclear burning. Hypernovae are often associated with long-duration γ-ray bursts in the nearby Universe8. This connection indicates that similar explosions of fast-spinning strongly magnetized stars occurred during the earliest epochs of star formation in our Galaxy.

Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way.

The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.

A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36-670839.3.

The element abundance ratios of four low-mass stars with extremely low metallicities (abundances of elements heavier than helium) indicate that the gas out of which the stars formed was enriched in each case by at most a few--and potentially only one--low-energy supernova. Such supernovae yield large quantities of light elements such as carbon but very little iron. The dominance of low-energy supernovae seems surprising, because it had been expected that the first stars were extremely massive, and that they disintegrated in pair-instability explosions that would rapidly enrich galaxies in iron. What has remained unclear is the yield of iron from the first supernovae, because hitherto no star has been unambiguously interpreted as encapsulating the yield of a single supernova. Here we report the optical spectrum of SMSS J031300.36-670839.3, which shows no evidence of iron (with an upper limit of 10(-7.1) times solar abundance). Based on a comparison of its abundance pattern with those of models, we conclude that the star was seeded with material from a single supernova with an original mass about 60 times that of the Sun (and that the supernova left behind a black hole). Taken together with the four previously mentioned low-metallicity stars, we conclude that low-energy supernovae were common in the early Universe, and that such supernovae yielded light-element enrichment with insignificant iron. Reduced stellar feedback both chemically and mechanically from low-energy supernovae would have enabled first-generation stars to form over an extended period. We speculate that such stars may perhaps have had an important role in the epoch of cosmic reionization and the chemical evolution of early galaxies.

Neurogenic overactive bladder in spinal cord injury and multiple sclerosis: role of onabotulinumtoxinA.

People with neurogenic overactive bladder from either multiple sclerosis or spinal cord injury often suffer significant morbidity and decreased quality of life. Here we review the pathophysiology of neurogenic overactive bladder and the impact it can have on people with multiple sclerosis or spinal cord injury. We also address the various traditional treatment options and focus on the use of botulinum toxin A (specifically onabotulinumtoxinA) for this condition.

Intrathecal drug therapy using the Codman Model 3000 Constant Flow Implantable Infusion Pumps: experience with 17 cases.

OBJECTIVES: The objective of this study was to evaluate the accuracy, reliability, safety, and efficacy of the Codman Model 3000 Constant Flow Implantable Infusion Pump for intrathecal baclofen delivery as a therapeutic option for the treatment of severe spasticity. The distinctive features of this pump include a raised, easily palpable septum, a safety valve protecting the bolus pathway, no programmer needed, and no battery to fail. DESIGN: A total of 17 patients with spinal cord injury, multiple sclerosis, or cerebral palsy were implanted with this pump. The accuracy of the pump and drug treatment efficacy was determined at each visit and adjustments to the dosages were made as required. All the intrathecal drug delivery system complications were reviewed. RESULTS: The expected efficacy was achieved. The accuracy of the implanted pumps ranged from 90-97% (average 94%). There were no complications due to primary pump problems. The complications reported are similar to other implantable infusion devices and include dehiscence of the suture line, pressure ulcer development, formation of seroma, inversion of the pump, baclofen overdose, and catheter failures. CONCLUSION: The Codman Model 3000 Constant Flow Implantable Infusion Pump is an accurate, reliable, and convenient option for patients needing intrathecal baclofen therapy, with complications similar to other available pumps.