Neutron star mass estimates from gamma-ray eclipses in spider millisecond pulsar binaries.

Reliable neutron star mass measurements are key to determining the equation of state of cold nuclear matter, but such measurements are rare. Black widows and redbacks are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. Although inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly understood variability. Using data from the Fermi Large Area Telescope, we have searched for gamma-ray eclipses from 49 spider systems, discovering significant eclipses in 7 systems, including the prototypical black widow PSR B1957+20. Gamma-ray eclipses require direct occultation of the pulsar by the companion, and so the detection, or significant exclusion, of a gamma-ray eclipse strictly limits the binary inclination angle, providing new robust, model-independent pulsar mass constraints. For PSR B1957+20, the eclipse implies a much lighter pulsar (1.81 ± 0.07 solar masses) than inferred from optical light curve modelling.

Upgraded Giant Metrewave Radio Telescope timing of NGC 1851A: a possible millisecond pulsar - neutron star system.

In this work, we present the results of 1 yr of upgraded Giant Metrewave Radio Telescope timing measurements of PSR J0514-4002A, a 4.99-ms pulsar in a 18.8-d eccentric ([Formula: see text]) orbit with a massive companion located in the globular cluster NGC 1851. Combining these data with earlier Green Bank Telescope data, we greatly improve the precision of the rate of advance of periastron, [Formula: see text] which, assuming the validity of general relativity, results in a much refined measurement of the total mass of the binary, [Formula: see text]. Additionally, we measure the Einstein delay parameter, γ, something that has never been done for any binary system with an orbital period larger than [Formula: see text]10 h. The measured value, [Formula: see text], is by far the largest for any binary pulsar. Furthermore, we measure the proper motion of the system ([Formula: see text] and [Formula: see text]), which is not only important for analysing its motion in the cluster, but is also essential for a proper interpretation of γ, given the latter parameter's correlation with the variation of the projected semimajor axis. The measurements of γ and the proper motion enable a separation of the system component masses: we obtain a pulsar mass of [Formula: see text] and a companion mass of [Formula: see text]. This raises the possibility that the companion is also a neutron star. Searches for radio pulsations from the companion have thus far been unsuccessful; hence, we cannot confirm the latter hypothesis. The low mass of this millisecond pulsar - one of the lowest ever measured for such objects - clearly indicates that the recycling process can be achieved with a relatively small amount of mass transfer.

An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102.

Fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. The only known repeating fast radio burst source-FRB 121102-has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46 × 105 radians per square metre to +1.33 × 105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.

A direct localization of a fast radio burst and its host.

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

Axin2-expressing cells execute regeneration after skeletal injury.

The mammalian skeleton performs a diverse range of vital functions, requiring mechanisms of regeneration that restore functional skeletal cell populations after injury. We hypothesized that the Wnt pathway specifies distinct functional subsets of skeletal cell types, and that lineage tracing of Wnt-responding cells (WRCs) using the Axin2 gene in mice identifies a population of long-lived skeletal cells on the periosteum of long bone. Ablation of these WRCs disrupts healing after injury, and three-dimensional finite element modeling of the regenerate delineates their essential role in functional bone regeneration. These progenitor cells in the periosteum are activated upon injury and give rise to both cartilage and bone. Indeed, our findings suggest that WRCs may serve as a therapeutic target in the setting of impaired skeletal regeneration.

A repeating fast radio burst.

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

A millisecond pulsar in a stellar triple system.

Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar M[Symbol: see text](1.4378(13), where M[Symbol: see text]is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)M[Symbol: see text] and 0.4101(3))M[Symbol: see text], as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.

Swings between rotation and accretion power in a binary millisecond pulsar.

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.

The Nursing Observed Illness Intensity Scale (NOIIS).

Inpatient progress is monitored mostly via the observation conducted by nursing staff. These tend to be unstructured, vary in reliability between different staff members, and be dependent on what has been written in nursing notes. The Nursing Observed Illness Intensity Scale (NOIIS) was devised to provide a more objective measure of behavioural improvement and symptom reduction. The scale is completed by qualified nurses at the end of every shift, based on everyday nursing observation and interaction with patients, and scores are entered on a NOIIS 'temperature' chart. In this study, more than 6000 ratings were captured on 106 admissions to a psychiatric intensive care unit. Inter-rater reliability of the scale was found to be satisfactory, and validity against the Brief Psychiatric Rating Scale good. Scores were shown to relate to the social organization and treatment methods of the unit. Recovery curves differed significantly by diagnosis, with patients having schizophrenia showing the slowest improvement. From a clinical point of view, the NOIIS can be used to track progress, response to changes in treatment and readiness of the patient for discharge; aids staff deployment; and can be used for clinical audit. For research, the scale can be used in clinical trials of treatment outcomes.

A two-solar-mass neutron star measured using Shapiro delay.

Neutron stars are composed of the densest form of matter known to exist in our Universe, the composition and properties of which are still theoretically uncertain. Measurements of the masses or radii of these objects can strongly constrain the neutron star matter equation of state and rule out theoretical models of their composition. The observed range of neutron star masses, however, has hitherto been too narrow to rule out many predictions of 'exotic' non-nucleonic components. The Shapiro delay is a general-relativistic increase in light travel time through the curved space-time near a massive body. For highly inclined (nearly edge-on) binary millisecond radio pulsar systems, this effect allows us to infer the masses of both the neutron star and its binary companion to high precision. Here we present radio timing observations of the binary millisecond pulsar J1614-2230 that show a strong Shapiro delay signature. We calculate the pulsar mass to be (1.97 ± 0.04)M(⊙), which rules out almost all currently proposed hyperon or boson condensate equations of state (M(⊙), solar mass). Quark matter can support a star this massive only if the quarks are strongly interacting and are therefore not 'free' quarks.

Pulsar discovery by global volunteer computing.

Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period; the pulsar likely has closely aligned magnetic and spin axes. The massive computing power provided by volunteers should enable many more such discoveries.

The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge.

Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale (less than 1 Gyr) and with virtually no dispersion in the iron content. Indeed, only one cluster-like system (omega Centauri) in the Galactic halo is known to have multiple stellar populations with a significant spread in iron abundance and age. Similar findings in the Galactic bulge have been hampered by the obscuration arising from thick and varying layers of interstellar dust. Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron contents and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.

Maternal bisphenol-A levels at delivery: a looming problem?

OBJECTIVE: The objective was to determine whether bisphenol-A (BPA) is found in maternal circulation of pregnant women in the US population and is related to gestational length and birth weight. METHOD: Circulating levels of BPA were quantified by high performance liquid chromatography-tandem mass spectrometry at delivery in 40 southeastern Michigan mothers and correlated with gestational length and birth weight of offspring. RESULT: Maternal levels of unconjugated BPA ranged between 0.5 and 22.3 ng ml(-1) in southeastern Michigan mothers. There was no correlation between BPA concentrations and gestational length or birth weight of offspring. CONCLUSION: This is the first study to document measurable levels of BPA in maternal blood of the US population. Long-term follow-up studies of offspring are needed to validate or refute concerns over human fetal exposure to synthetic exogenous steroids.

Characteristics and correlates of cognitive functioning following bone marrow transplantation.

Patients who undergo bone marrow transplantation (BMT) often report cognitive problems following treatment. This study used cognitive tests and a self-report measure of subjective cognitive complaints to determine (1) the rate of objective cognitive impairment in a sample of 65 BMT patients, and (2) the correspondence of patients' cognitive complaints to their actual cognitive performance. At 6 months following BMT, patients were assessed in seven cognitive domains--attention, verbal learning, verbal memory, visual memory, simple executive function, complex executive function, and psychomotor speed. Cognitive complaints were likewise assessed. In all, 51% had at least mild impairment (-1 standard deviation (s.d.) below published norms) in one or more cognitive domains, with 28% demonstrating moderate-to-severe impairment (-2 s.d.). Older patients and patients with lower IQ were more likely to score in the impaired range on objective cognitive tests, with males and the less educated showing trends toward scores in the impaired range. Younger patients made significantly more cognitive complaints. Total cognitive complaints were unrelated to average cognitive performance, and complaints in specific cognitive domains were largely unrelated to objective performance on corresponding domains. Findings suggest that patients who complain about their cognitive performance following BMT differ from those who experience actual deficits.

Multifetal pregnancy reduction: perinatal and fiscal outcomes.

OBJECTIVE: This study was undertaken to compare the birth outcomes of a multifetal pregnancy reduction population with those of other patients delivered at Hutzel Hospital, Detroit, and to determine the fiscal impact of the multifetal pregnancy reduction program. STUDY DESIGN: In a retrospective review patients who were delivered after multifetal pregnancy reduction were compared with a general obstetric population who were delivered at Hutzel Hospital from January 1, 1986, through June 30, 1998. Outcome data were determined through a comprehensive perinatal database. The chi(2) analysis was used to examine the relationship between gestational age and delivery group. Financial data were estimated from published reports of neonatal intensive care unit admissions, cost estimates for neonatal intensive care unit care, and charges for multifetal pregnancy reduction. RESULTS: Pregnancies reduced to triplets, twins, and singletons had outcomes at least comparable to unreduced pregnancies starting at these numbers and substantially better than unreduced pregnancies with the same starting number. Financial estimates of hospitalization costs averted in the multifetal pregnancy reduction population exceeded $28 million. CONCLUSION: Use of multifetal pregnancy reduction improved obstetric outcomes for pregnancies with multiple gestations and also was associated with significant fiscal savings.

Fiscal impact of a potential legislative ban on second trimester elective terminations for prenatally diagnosed abnormalities.

This study was designed to determine the fiscal impact of a theoretical legislative ban on elective terminations for prenatally diagnosed abnormalities at Hutzel Hospital/Wayne State University. A fiscal comparison was completed for patients who had second trimester elective terminations for prenatally diagnosed abnormalities versus not allowing the procedure. An eight-year database of genetics cases and hospital and physician cost estimates for performing elective terminations for prenatally diagnosed abnormalities, and published reports of the average lifetime costs per selected birth defects, were used to calculate the net cost. The estimated lifetime cost for an average cohort year of a legislative ban on elective terminations for prenatally diagnosed abnormalities was found to be at least $8.5 million for patients treated at Hutzel Hospital. Extrapolated, a similar ban on second trimester elective terminations would have a net cost of $74 million in Michigan and $2 billion annually in the United States.

Cost-effectiveness of routine blood type and screen testing for cesarean section.

OBJECTIVE: To evaluate the usefulness and cost-effectiveness of admission blood type and screen testing for cesarean section. STUDY DESIGN: A retrospective review was conducted on patients transfused with blood during an admission that required a cesarean section over a three-year period at a tertiary care hospital. RESULTS: Of 3,962 patients who underwent cesarean section, 132 (3.3%) required a blood transfusion during their hospital stay. Medical records of 125 of the 132 patients were evaluated as to urgency and risk factors. (Seven charts could not be located.) Most of the blood transfusions were related to previously identified risk factors, including previous cesarean section, chorioamnionitis, placenta previa, abnormal presentation (breech or transverse lie), multiple pregnancies, abruptio placentae and admission anemia. Three patients received an urgent blood transfusion without a previously identifiable risk factor. Thus, we found an overall urgent blood transfusion rate without admission risk factors to be 0.8 per 1,000 cesarean sections. CONCLUSION: In the absence of significant risk factors, routine admission blood type and screen testing for cesarean section does not enhance patient care and should be eliminated. In the rare event that a patient without a previously identified risk factor requires an urgent blood transfusion, O negative blood could be given in the interim pending formal determination of type and cross-match.

Oral metronidazole vs. Metrogel Vaginal for treating bacterial vaginosis. Cost-effectiveness evaluation.

OBJECTIVE: To compare the cost-effectiveness of metronidazole versus Metrogel Vaginal in the treatment of bacterial vaginosis. STUDY DESIGN: Sixty consecutive patients with a clinical diagnosis of bacterial vaginosis were randomly assigned prospectively into either the metronidazole, 500 mg (twice daily for seven days by mouth) or Metrogel Vaginal (one applicator twice daily for five days) treatment group. The study patients were aged 18-30 years, without other medical problems. The patients proceeded with outpatient therapy and returned 7-10 days after the completion of treatment for reevaluation. During the study, patients refrained from sexual relations, avoided alcohol and drugs, and avoided all medication. The physician evaluated the patients for bacterial vaginosis through standard wet preparation, whiff test and pH testing prior to and after treatment. The patients were randomized by a nurse and were blinded for study purposes to the evaluating physician. RESULTS: Successful treatment outcomes for bacterial vaginosis occurred in 27 and 28 patients for Metrogel Vaginal and metronidazole, respectively, out of the original 30 patients in each study group. All patients introduced into the study completed the study without difficulty. No significant complications were found in either treatment group. Three patients treated with metronidazole experienced nausea during the treatment interval. The entire cost of treatment was $19.71 and $1.51 for Metrogel Vaginal and metronidazole, respectively. CONCLUSION: The most cost-effective treatment for bacterial vaginosis was generic metronidazole. While the use of the more expensive Metrogel Vaginal may be reasonable for patients experiencing side effects of oral metronidazole, most patients should be treated with the less expensive generic metronidazole.