26 research outputs found
Comments on ``The first detections of the Extragalactic Background Light at 3000, 5500, and 8000 A'' by Bernstein, Freedman and Madore
A critical discussion is presented of the data analysis applied by Bernstein,
Freedman and Madore (2002 ApJ, 571, 56; and ApJ 571, 85) in their measurement
of the Extragalactic Background Light. There are questionable assumptions in
the analysis of the ground-based observations of the Zodiacal Light. The
modeling of the Diffuse Galactic Light is based on an underestimated value of
the dust column density along the line of sight. Comparison with the previously
presented results from the same observations reveals a puzzling situation: in
spite of a large difference in the atmospheric scattered light corrections the
derived Extragalactic Background Light values are exactly the same. The claim
of the paper of a ``detection of the Extragalactic Background Light'' appears
premature.Comment: 6 pages, accepted for Ap
The Evolution of NGC 7027 at Radio Frequencies: A New Determination of the Distance and Core Mass
We present the results of a 25-year program to monitor the radio flux
evolution of the planetary nebula NGC7027. We find significant evolution of the
spectral flux densities. The flux density at 1465 MHz, where the nebula is
optically thick, is increasing at a rate of 0.251+-0.015 % per year, caused by
the expansion of the ionized nebula. At frequencies where the emission is
optically thin, the spectral flux density is changing at a rate of
-0.145+-0.005 % per year, caused by a decrease in the number of ionizing
photons coming from the central star. A distance of 980+-100 pc is derived. By
fitting interpolated models of post-AGB evolution to the observed changes, we
find that over the 25-yr monitoring period, the stellar temperature has
increased by 3900+-900 K and the stellar bolometric luminosity has decreased by
1.75+-0.38 %. We derive a distance-independent stellar mass of 0.655+-0.01
solar masses adopting the Bloecker stellar evolution models, or about 0.04
solar masses higher when using models of Vassiliadis & Wood which may provide a
better fit. A Cloudy photoionization model is used to fit all epochs at all
frequencies simultaneously. The differences between the radio flux density
predictions and the observed values show some time-independent residuals of
typically 1 %. A possible explanation is inaccuracies in the radio flux scale
of Baars et al. We propose an adjustment to the flux density scale of the
primary radio flux calibrator 3C286, based on the Cloudy model of NGC7027. We
also calculate precise flux densities for NGC7027 for all standard continuum
bands used at the VLA, as well as for some new 30GHz experiments.Comment: submitted to the Astrophysical Journa
Caregivers’ interactions with health care services: mediator of stress or added strain? Experiences and perceptions of informal caregivers of people with dementia: a qualitative study
Background: There are an estimated 46.8 million people worldwide living with dementia in 2015, being cared for usually by family members or friends (informal caregivers). The challenges faced by informal caregivers often lead to increased levels of stress, burden and risk of care-recipient institutionalisation.
Aim: The overarching aim of this study was to explore the experiences and perceptions of informal caregivers of people with dementia when interacting with the health care system, and whether the support received acted as a mediator of caregiver stress. The secondary aim was to investigate healthcare professionals’ views and current practice regarding people with dementia and their interactions with informal caregivers.
Method: We employed a qualitative research design, using focus groups and one face-to-face interview with a purposive sample of informal caregivers and healthcare professionals (HCPs) in Lincolnshire, UK. Data were collected between March and July 2015. We used the stress-process model of stress in caregivers as a theoretical framework.
Results: We interviewed 18 caregivers and 17 HCPs. Five themes, mapped to the stress-process in caregivers’ model, captured the main challenges faced by caregivers and the type of support they wanted from health care services. Primary stressors included the challenge of diagnosing dementia; caregivers’ needs and expectations of an in-depth knowledge and understanding of dementia from HCPs; and need for carer education. Secondary role strain included lack of support and mismatch of communication and expectations. Caregiver involvement in monitoring care and disease was a potential mediator tool.
Conclusions: Fragmentation of dementia care services, lack of training for HCPs and the dearth of information for caregivers means health care services are only partially fulfilling a support role. In turn, lack of support may be intensifying caregiver stress leading to worsening in their health and well-being; thus, potentially increasing the risk of institutionalisation of their care-recipient
The Iron abundance in Galactic Planetary Nebulae
We constrain the iron abundance in a sample of 33 low-ionization Galactic
planetary nebulae (PNe) using [Fe III] lines and correcting for the
contribution of higher ionization states with ionization correction factors
(ICFs) that take into account uncertainties in the atomic data. We find very
low iron abundances in all the objects, suggesting that more than 90% of their
iron atoms are condensed onto dust grains. This number is based on the solar
iron abundance and implies a lower limit on the dust-to-gas mass ratio, due
solely to iron, of M_dust/M_gas>1.3x10^{-3} for our sample. The depletion
factors of different PNe cover about two orders of magnitude, probably
reflecting differences in the formation, growth, or destruction of their dust
grains. However, we do not find any systematic difference between the gaseous
iron abundances calculated for C-rich and O-rich PNe, suggesting similar iron
depletion efficiencies in both environments. The iron abundances of our sample
PNe are similar to those derived following the same procedure for a group of 10
Galactic H II regions. These high depletion factors argue for high depletion
efficiencies of refractory elements onto dust grains both in molecular clouds
and AGB stars, and low dust destruction efficiencies both in interstellar and
circumstellar ionized gas.Comment: Accepted for publication in ApJ. 15 pages, 4 Postscript figures,
corrected typos, Tables 2 and 3 correcte
The return of the 'Conchie': newspaper representations of conscientious objectors and pacifists in World War II
This chapter will consider the ways in which British regional and national newspapers represented conscientious objectors in the early stages of World War 11
How History Challenges Current Thinking on Hybridity: The Effects of Hybridity on London’s Transport 1933–1948.
This chapter discusses the cross-sectional relationships between national and local government, citizens and hybrid organisations via a historical case study, that of the London Passenger Transport Board (LPTB) during its existence 1933–1948. It finds that the LPTB was a good example of hybridity located in an earlier time period than most research examines, and that the arrangements by which it was governed resulted in some counter-intuitive outcomes which challenge the findings from research located in more recent periods concerning the performance of hybrid organisations. However, it supports other research proposing that the role of elites as well as institutional contexts is a key factor in the creation and operation of semi-autonomous organisations, and it accepts that objectively measuring the performance in order to make meaningful comparison is not only extremely problematic but may even inhibit performance