A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817.

GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the observed γ-ray, X-ray and radio emission is due to an ultra-relativistic jet being launched during the merger (and successfully breaking out of the surrounding material), directed away from our line of sight (off-axis). The presence of such a jet is predicted from models that posit neutron-star mergers as the drivers of short hard-γ-ray bursts. Here we report that the radio light curve of GW170817 has no direct signature of the afterglow of an off-axis jet. Although we cannot completely rule out the existence of a jet directed away from the line of sight, the observed γ-ray emission could not have originated from such a jet. Instead, the radio data require the existence of a mildly relativistic wide-angle outflow moving towards us. This outflow could be the high-velocity tail of the neutron-rich material that was ejected dynamically during the merger, or a cocoon of material that breaks out when a jet launched during the merger transfers its energy to the dynamical ejecta. Because the cocoon model explains the radio light curve of GW170817, as well as the γ-ray and X-ray emission (and possibly also the ultraviolet and optical emission), it is the model that is most consistent with the observational data. Cocoons may be a ubiquitous phenomenon produced in neutron-star mergers, giving rise to a hitherto unidentified population of radio, ultraviolet, X-ray and γ-ray transients in the local Universe.

A transient radio source consistent with a merger-triggered core collapse supernova.

A core collapse supernova occurs when exothermic fusion ceases in the core of a massive star, which is typically caused by exhaustion of nuclear fuel. Theory predicts that fusion could be interrupted earlier by merging of the star with a compact binary companion. We report a luminous radio transient, VT J121001+495647, found in the Very Large Array Sky Survey. The radio emission is consistent with supernova ejecta colliding with a dense shell of material, potentially ejected by binary interaction in the centuries before explosion. We associate the supernova with an archival x-ray transient, which implies that a relativistic jet was launched during the explosion. The combination of an early relativistic jet and late-time dense interaction is consistent with expectations for a merger-driven explosion.

A radio counterpart to a neutron star merger.

Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry.

Changes in maternity care and the impact on nurses and nursing practice.

OBJECTIVE: To determine changes maternity nurses have experienced and the impact these changes have had on nursing practice. DESIGN: Descriptive survey using a randomized sample. PARTICIPANTS: Four hundred fifty-one inpatient female maternity nurses. MAIN OUTCOME MEASURES: Changes in maternity care, impact of the changes on nursing practice, and personal and professional perceptions and activities before and after the changes. RESULTS: Reported changes were use of technology, legal climate, shorter patient stay, cost containment, inclusion of family, cross training, consumer demand, and single-room maternity care. Inclusion of the family, technology, and single-room care were rated highly for worth and improvement in quality of care. Though described as challenging and rewarding, change was an energy drain. Change was often seen as a result of administrative mandate. CONCLUSIONS: Perceptions of change vary, but no change is easy to implement. Opportunities for staff input, administrative support, and adequate time and staffing levels during change facilitate adjustment.

Scaling the universe: gravitational lenses and the Hubble constant.

Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as "gravitational standard rulers" for the measurement of the rate of expansion of the Universe (Ho), as well as to constrain the values of the cosmological parameters such as Omegao and Lambdao that control the evolution of the volume of the Universe with cosmic time.

Reflections on recruitment and retention at the unit level.

This article describes factors that 451 nurses reported influenced decisions to stay or leave their positions as well as factors they believed would recruit nurses to their units. Similar categories for both recruitment and retention were salary/hours/benefits, personal growth/challenge, work environment/staff relationships, satisfaction/fulfillment, and patient contact. Stress, lack of respect or acknowledgement, and role change related to turnover. The factors are consistent with other surveys across the decade. Implications of these factors for nurse-manager recruitment and retention strategies are discussed.

Use of occlusive dressings on central venous catheter sites in hospitalized children.

Although the use of occlusive dressings in adults has been criticized in the literature, there has been little written on their use in the pediatric population. Management of dressing sites requires nursing judgement unique to this population. This study focused on the progression of microbial colonization and signs of inflammation occurring beneath repeated occlusive dressings applied to central venous catheter (CVC) insertion sites among 104 hospitalized children (neonate to 18 years). A noninvasive skin culture was obtained within 24 hours of CVC placement, 3 to 7 days later before the next routine dressing change, and at the time the CVC was discontinued or the child was discharged, whichever occurred first. Results showed a significant increase in microbial growth (p < or = .001) at the second dressing change, when serosanguinous drainage was heaviest, and continued significant growth (p < or = .001) when the dressing was discontinued. This microbial growth pattern was curious in the face of a 0.3% systemic sepsis rate. When neonates under 1,800 g were excluded from calculation, the pattern was not notable (p = .2119). Findings suggest the use of occlusive dressings during prolonged hospitalization for tunnelled CVCs does not lead to increased site infections in children over 1,800 g.

A process-driven curriculum in nursing education.

Myers et. al. show what a curriculum looks like when it's based on learning strategies and thinking processes instead of being content based. The authors identify five critical operations: clinical process, consultation, managerial process, educative/learning and the investigative processes. New NLN procedures encourage such creative designs; you'll enjoy reading about this one.

Polarization observations with the Cosmic Background Imager.

Polarization observations of the cosmic microwave background with the Cosmic Background Imager from September 2002 to May 2004 provide a significant detection of the E-mode polarization and reveal an angular power spectrum of polarized emission showing peaks and valleys that are shifted in phase by half a cycle relative to those of the total intensity spectrum. This key agreement between the phase of the observed polarization spectrum and that predicted on the basis of the total intensity spectrum provides support for the standard model of cosmology, in which dark matter and dark energy are the dominant constituents, the geometry is close to flat, and primordial density fluctuations are predominantly adiabatic with a matter power spectrum commensurate with inflationary cosmological models.

Constraints on cosmological parameters from the analysis of the cosmic lens all sky survey radio-selected gravitational lens statistics.

We derive constraints on cosmological parameters and the properties of the lensing galaxies from gravitational lens statistics based on the final Cosmic Lens All Sky Survey data. For a flat universe with a classical cosmological constant, we find that the present matter fraction of the critical density is Omega(m)=0.31(+0.27)(-0.14) (68%)+0.12-0.10 (syst). For a flat universe with a constant equation of state for dark energy w=p(x)(pressure)/rho(x)(energy density), we find w<-0.55(+0.18)(-0.11) (68%).