518 research outputs found
Constraining the Equation of State with Moment of Inertia Measurements
We estimate that the moment of inertia of star A in the recently discovered
double pulsar system PSR J0737-3039 may be determined after a few years of
observation to something like 10% accuracy. This would enable accurate
estimates of the radius of the star and the presure of matter in the vicinity
of 1 to 2 times the nuclear saturation density, which would in turn provide
strong constraints on the equation of state of neutron stars and the physics of
their interiors.Comment: Submitted to ApJ, 4 figure
Question design in nurse-led and GP-led telephone triage for same-day appointment requests: a comparative investigation
Objective: To compare doctorsâ and nursesâ communication with patients in primary care telephone triage consultations. Design: Qualitative comparative study of content and form of questions in 51 telephone triage encounters between practitioners (general practitioners (GPs)=29; nurses=22) and patients requesting a same-day appointment in primary care. Audio-recordings of nurse-led calls were synchronised with video recordings of nurse's use of computer decision support software (CDSS) during triage. Setting: 2 GP practices in Devon and Warwickshire, UK. Participants: 4 GPs and 29 patients; and 4 nurses and 22 patients requesting a same-day face-to-face appointment with a GP. Main outcome measure: Form and content of practitioner-initiated questions and patient responses during clinical assessment. Results: A total of 484 questionâresponse sequences were coded (160 GP; 324 N). Despite average call lengths being similar (GP=4â
min, 37â
s, (SD=1â
min, 26â
s); N=4â
min, 39â
s, (SD=2â
min, 22â
s)), GPs and nurses differed in the average number (GP=5.51, (SD=4.66); N=14.72, (SD=6.42)), content and form of questions asked. A higher frequency of questioning in nurse-led triage was found to be due to nursesâ use of CDSS to guide telephone triage. 89% of nurse questions were oriented to asking patients about their reported symptoms or to wider-information gathering, compared to 54% of GP questions. 43% of GP questions involved eliciting patient concerns or expectations, and obtaining details of medical history, compared to 11% of nurse questions. Nurses using CDSS frequently delivered questions designed as declarative statements requesting confirmation and which typically preferred a âno problemâ response. In contrast, GPs asked a higher proportion of interrogative questions designed to request information. Conclusions: Nurses and GPs emphasise different aspects of the clinical assessment process during telephone triage. These different styles of triage have implications for the type of information available following nurse-led or doctor-led triage, and for how patients experience triage
Emergency and on-demand health care: modelling a large complex system
This paper describes how system dynamics was used as a central part of a whole-system review of emergency and on-demand health care in Nottingham, England. Based on interviews with 30 key individuals across health and social care, a 'conceptual map' of the system was developed, showing potential patient pathways through the system. This was used to construct a stock-flow model, populated with current activity data, in order to simulate patient flows and to identify system bottle-necks. Without intervention, assuming current trends continue, Nottingham hospitals are unlikely to reach elective admission targets or achieve the government target of 82% bed occupancy. Admissions from general practice had the greatest influence on occupancy rates. Preventing a small number of emergency admissions in elderly patients showed a substantial effect, reducing bed occupancy by 1% per annum over 5 years. Modelling indicated a range of undesirable outcomes associated with continued growth in demand for emergency care, but also considerable potential to intervene to alleviate these problems, in particular by increasing the care options available in the community
NS 1987A in SN 1987A
The possible detection of a compact object in the remnant of SN 1987A
presents an unprecedented opportunity to follow its early evolution. The
suspected detection stems from an excess of infrared emission from a dust blob
near the compact object's predicted position. The infrared excess could be due
to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or
black hole, magnetospheric emission or a wind originating from the spindown of
a pulsar, or thermal emission from an embedded, cooling neutron star (NS
1987A). It is shown that the last possibility is the most plausible as the
other explanations are disfavored by other observations and/or require
fine-tuning of parameters. Not only are there indications the dust blob
overlaps the predicted location of a kicked compact remnant, but its excess
luminosity also matches the expected thermal power of a 30 year old neutron
star. Furthermore, models of cooling neutron stars within the Minimal Cooling
paradigm readily fit both NS 1987A and Cas A, the next-youngest known neutron
star. If correct, a long heat transport timescale in the crust and a large
effective stellar temperature are favored, implying relatively limited crustal
n-1S0 superfluidity and an envelope with a thick layer of light elements,
respectively. If the locations don't overlap, then pulsar spindown or accretion
might be more likely, but the pulsar's period and magnetic field or the
accretion rate must be rather finely tuned. In this case, NS 1987A may have
enhanced cooling and/or a heavy-element envelope.Comment: 21 pages, 6 figures, to be published in Ap
Revisiting the Parallax of the Isolated Neutron Star RX J185635-3754 Using HST/ACS Imaging
We have redetermined the parallax and proper motion of the nearby isolated
neutron star RX~J185635-3754. We used eight observations with the high
resolution camera of the HST/ACS taken from 2002 through 2004. We performed the
astrometric fitting using five independent methods, all of which yielded
consistent results. The mean estimate of the distance is 123 (+11, -15) pc (1
sigma), in good agreement with our earlier published determination
Integrated out-of-hours care arrangements in England: observational study of progress towards single call access via NHS Direct and impact on the wider health system
Objectives: To assess the extent of service integration achieved within general practice cooperatives and NHS Direct sites participating in the Department of Healthâs national âExemplar Programmeâ for single call access to out-of-hours care via NHS Direct. To assess the impact of integrated out-of-hours care arrangements upon general practice cooperatives and the wider health system (use of emergency departments, 999 ambulance services, and minor injuries units).
Design: Observational before and after study of demand, activity, and trends in the use of other health services.
Setting: Thirty four English general practice cooperatives with NHS Direct partners (âexemplarsâ) of which four acted as âcase exemplarsâ. Also 10 control cooperatives for comparison.
Main Outcome Measures: Extent of integration achieved (defined as the proportion of hours and the proportion of general practice patients covered by integrated arrangements), patterns of general practice cooperative demand and activity and trends in use of the wider health system in the first year.
Results: Of 31 distinct exemplars 21 (68%) integrated all out-of-hours call management by March 2004. Nine (29%) established single call access for all patients. In the only case exemplar where direct comparison was possible, cooperative nurse telephone triage before integration completed a higher proportion of calls with telephone advice than did NHS Direct afterwards (39% v 30%; p<0.0001). The proportion of calls completed by NHS Direct telephone advice at other sites was lower. There is evidence for transfer of demand from case exemplars to 999 ambulance services. A downturn in overall demand for care seen in two case exemplars was also seen in control sites.
Conclusion: The new model of out-of-hours care was implemented in a variety of settings across England by new partnerships between general practice cooperatives and NHS Direct. Single call access was not widely implemented and most patients needed to make at least two telephone calls to contact the service. In the first year, integration may have produced some reduction in total demand, but this may have been accompanied by shifts from one part of the local health system to another. NHS Direct demonstrated capability in handling calls but may not currently have sufficient capacity to support national implementation
Effect of the momentum dependence of nuclear symmetry potential on the transverse and elliptic flows
In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck
transport model, effect of the momentum dependence of nuclear symmetry
potential on nuclear transverse and elliptic flows in the neutron-rich reaction
Sn+Sn at a beam energy of 400 MeV/nucleon is studied. We find
that the momentum dependence of nuclear symmetry potential affects the rapidity
distribution of the free neutron to proton ratio, the neutron and the proton
transverse flows as a function of rapidity. The momentum dependence of nuclear
symmetry potential affects the neutron-proton differential transverse flow more
evidently than the difference of neutron and proton transverse flows as well as
the difference of proton and neutron elliptic flows. It is thus better to probe
the symmetry energy by using the difference of neutron and proton flows since
the momentum dependence of nuclear symmetry potential is still an open
question. And it is better to probe the momentum dependence of nuclear symmetry
potential by using the neutron-proton differential transverse flow and the
rapidity distribution of the free neutron to proton ratio.Comment: 6 pages, 6 figures, to be published by EPJ
Equation of state and phase transitions in asymmetric nuclear matter
The structure of the 3-dimension pressure-temperature-asymmetry surface of
equilibrium of the asymmetric nuclear matter is studied within the thermal
Thomas-Fermi approximation. Special attention is paid to the difference of the
asymmetry parameter between the boiling sheet and that of the condensation
sheet of the surface of equilibrium. We derive the condition of existence of
the regime of retrograde condensation at the boiling of the asymmetric nuclear
matter. We have performed calculations of the caloric curves in the case of
isobaric heating. We have shown the presence of the plateau region in caloric
curves at the isobaric heating of the asymmetric nuclear matter. The shape of
the caloric curve depends on the pressure and is sensitive to the value of the
asymmetry parameter. We point out that the experimental value of the plateau
temperature T \approx 7 MeV corresponds to the pressure P = 0.01 MeV/fm^3 at
the isobaric boiling.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Neutron stars with isovector scalar correlations
Neutron stars with the isovector scalar -field are studied in the
framework of the relativistic mean field () approach in a pure nucleon
plus lepton scheme. The -field leads to a larger repulsion in dense
neutron-rich matter and to a definite splitting of proton and neutron effective
masses. Both features are influencing the stability conditions of the neutron
stars. Two parametrizations for the effective nonlinear Lagrangian density are
used to calculate the nuclear equation of state () and the neutron star
properties, and compared to correlated Dirac-Brueckner results. We conclude
that in order to reproduce reasonable nuclear structure and neutron star
properties within a approach a density dependence of the coupling
constants is required.Comment: 11 pages, 5 figures, revtex4 styl
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