3,446 research outputs found
Attitudes to telecare among older people, professional care workers and informal carers: a preventative strategy or crisis management?
This paper reports findings from an attitudinal survey towards telecare that emerged from twenty-two focus groups comprising ninety-two older people, fifty-five professional stakeholders and thirty-nine carers. These were convened in three different regions of England as a precursor to telecare service development. The results from this study suggest that informantsâ views were shaped by prior knowledge of conventional health and social care delivery in their locality and the implication is that expectations and requirements in respect of telecare services in general are likely to be informed by wider perceptions about the extent to which community care should operate as a preventative strategy or as a mechanism for crisis management
Sea turtle nesting in the Ten Thousand Islands of Florida
Loggerhead sea turtles (Caretta caretta) nest in numerous substrate and beach
types within the Ten Thousand Islands (TTl) of southwest Florida. Nesting beach
selection was analyzed on 12 islands within this archipelago. Numerous physical
characteristics were recorded to identify the relatedness of these variables and determine
their importance for nesting beach selection in C. caretta. These variables were chosen
after evaluating the islands, conducting literature searches and soliciting personal
communications. Along transects, data were collected, on the following: height of
canopy, beach width, overall slope (beach slope and slope of offshore approach) and sand
samples analyzed for pH, percentage of water, percentage of organic content, percentage
of carbonate and particle size (8 size classes). Data on ordinal aspect of beaches and
beach length were also recorded and included in the analysis. All of the variables were
analyzed by tree regression, incorporating the nesting data into the analysis. In the TTl,
loggerheads appear to prefer wider beaches (p< 0.001; R2
= 0.56) that inherently have less
slope, and secondarily, wider beaches that have low amounts of carbonate (p< O.00 1). In
addition, C. caretta favors nest sites within or in close proximity to the supra-littoral
vegetation zone of beaches in the TTl (p< 0.001). (86 page document
Sewing sound quantum flesh onto classical bones
Semiclassical transformation theory implies an integral representation for
stationary-state wave functions in terms of angle-action variables
(). It is a particular solution of Schr\"{o}dinger's time-independent
equation when terms of order and higher are omitted, but the
pre-exponential factor in the integrand of this integral
representation does not possess the correct dependence on . The origin of
the problem is identified: the standard unitarity condition invoked in
semiclassical transformation theory does not fix adequately in a
factor which is a function of the action written in terms of and
. A prescription for an improved choice of this factor, based on
succesfully reproducing the leading behaviour of wave functions in the vicinity
of potential minima, is outlined. Exact evaluation of the modified integral
representation via the Residue Theorem is possible. It yields wave functions
which are not, in general, orthogonal. However, closed-form results obtained
after Gram-Schmidt orthogonalization bear a striking resemblance to the exact
analytical expressions for the stationary-state wave functions of the various
potential models considered (namely, a P\"{o}schl-Teller oscillator and the
Morse oscillator).Comment: RevTeX4, 6 page
Constraints on supernova progenitors from spatial correlations with H-alpha emission
We have attempted to constrain the progenitors of all supernova types,
through correlations of the positions of historical supernovae with recent star
formation, as traced by H-alpha emission. Through pixel statistics we have
found that a large fraction of the SNII population do not show any association
with current star formation, which we put down to a 'runaway' fraction of these
progenitors. The SNIb/c population accurately traces the H-alpha emission, with
some suggestion that the SNIc progenitors show a higher degree of correlation
than the SNIb, suggesting higher mass progenitors for the former. Overall the
SNIa population only show a weak correlation to the positions of HII regions,
but as many as a half may be associated with a young stellar population.Comment: To appear in conference proceedings: "Supernova 1987A: 20 Years After
-- Supernovae & Gamma-Ray Bursters", held in Aspen, February 200
The Open Cluster Distance Scale: A New Empirical Approach
We present new BVRI photometry for a sample of 54 local G and K stars with accurate Hipparcos parallaxes in the metallicity range -0.4 < [Fe/H] < +0.3. We use this sample to develop a completely model-independent main sequence (MS) fitting method which we apply to 4 open clusters - the Hyades, Praesepe, the Pleiades and NGC 2516 - which all have direct Hipparcos parallax distance determinations. Comparison of our MS-fitting results with distances derived from Hipparcos parallaxes enables us to explore whether the discrepancy between the Hipparcos distance scale and other MS-fitting methods found for some clusters is a consequence of model assumptions. We find good agreement between our results and the Hipparcos ones for the Hyades and Praesepe. For the Pleiades and NGC 2516, when adopting the solar abundance determined from spectroscopy, we find significant disagreement at a level similar to that found by other MS-fitting studies. However, the colour-colour relationship for both these clusters suggests that their metallicity is significantly subsolar. Since the MS-fitting method relies on matching the cluster colours to a template MS, we argue that, when applying this method, the appropriate metallicity to adopt is the photometric subsolar one, not the solar abundance indicated by spectroscopy. Adopting photometric metallicities for all 4 clusters, we find complete agreement with the Hipparcos results and hence we conclude that the mismatch between the spectroscopic and photometric abundances for the Pleiades and NGC 2516 is responsible for the discrepancies in distance estimates found by previous studies. The origin of this mismatch in abundance scales remains an unsolved problem and some possible causes are discussed
Friedmann Equation for Brans Dicke Cosmology
In the context of Brans-Dicke scalar tensor theory of gravitation, the
cosmological Friedmann equation which relates the expansion rate of the
universe to the various fractions of energy density is analyzed rigorously. It
is shown that Brans-Dicke scalar tensor theory of gravitation brings a
negligible correction to the matter density component of Friedmann equation.
Besides, in addition to and in standard
Einstein cosmology, another density parameter, , is
expected by the theory. This implies that if is found to
be nonzero, data will favor this model instead of the standard Einstein
cosmological model with cosmological constant and will enable more accurate
predictions for the rate of change of Newtonian gravitational constant in the
future.Comment: minor reference change
The distance to the Pleiades: Main sequence fitting in the near infrared
Hipparcos parallax measurements of stars in the Pleiades notoriously result
in a cluster distance of 118 pc; ~10% shorter than the `classical' results of
MS-fitting. In an earlier paper we developed a purely empirical MS-fitting
method to address this problem, which produced conflicting results between the
(B-V) and (V-I) colour indices, indicating that the cluster's photometric
metallicity is substantially lower than its (~solar) spectroscopic metallicity.
We were able to reconcile the discrepancy by assuming [Fe/H]=-0.4 (as indicated
from (B-V)/(V-I) colour-colour plots), and the distance moduli obtained from
the 2 indices were in agreement with the Hipparcos result, within the 1sig
errors. With the release of the 2MASS All Sky Catalogue, we now apply our
MS-fitting method to the Pleiades using the infrared colours, in order to test
the plausibility of our earlier result. Fitting in the V/(V-K) and K/(J-K)
colour planes, we find that assuming a subsolar metallicity does not produce
distances in agreement with the (B-V) and (V-I) results. However the infrared
plus (V-I) distances are in mutual agreement when adopting the spectroscopic
metallicity. By considering only stars with Mv<=6, the infrared and optical
colour indices all yield consistent distances using the spectroscopic [Fe/H].
The concordant distances thus obtained from the (B-V), (V-I), (V-K) and (J-K)
indices yield a mean of 133.8+/-3 pc, in excellent agreement with the
pre-Hipparcos MS-fitting results, and the most recent determinations from other
methods. We conclude that there are two distinct issues affecting the Pleiades:
the Hipparcos parallax is in error by ~10%, as previously claimed; the (B-V)
colours of the lower MS are anomalous, and we caution against their use for
MS-fitting to the Pleiades and similarly young open clusters. (Abridged)Comment: 8 pages. A&A accepte
Chemical abundance anticorrelations in globular cluster stars: The effect on cluster integrated spectra
It is widely accepted that individual Galactic globular clusters harbor two
coeval generations of stars, the first one born with the `standard'
-enhanced metal mixture observed in field Halo objects, the second one
characterized by an anticorrelated CN-ONa abundance pattern overimposed on the
first generation, -enhanced metal mixture. We have investigated with
appropriate stellar population synthesis models how this second generation of
stars affects the integrated spectrum of a typical metal rich Galactic globular
cluster, like 47\,Tuc, focusing our analysis on the widely used Lick-type
indices. We find that the only indices appreciably affected by the abundance
anticorrelations are Ca4227, G4300, , and NaD. The
age-sensitive Balmer line, Fe line and the [MgFe] indices widely used to
determine age, Fe and total metallicity of extragalactic systems are largely
insensitive to the second generation population. Enhanced He in second
generation stars affects also the Balmer line indices of the integrated
spectra, through the change of the turn off temperature and -- in the
assumption that the mass loss history of both stellar generations is the same
-- the horizontal branch morphology of the underlying isochrones.Comment: Accepted for publication in Ap
Aspects of quantum coherence in the optical Bloch equations
Aspects of coherence and decoherence are analyzed within the optical Bloch
equations. By rewriting the analytic solution in an alternate form, we are able
to emphasize a number of unusual features: (a) despite the Markovian nature of
the bath, coherence at long times can be retained; (b) the long-time asymptotic
degree of coherence in the system is intertwined with the asymptotic difference
in level populations; (c) the traditional population-relaxation and decoherence
times, and , lose their meaning when the system is in the presence
of an external field, and are replaced by more general overall timescales; (d)
increasing the field strength, quantified by the Rabi frequency, ,
increases the rate of decoherence rather than reducing it, as one might expect;
and (e) maximum asymptotic coherence is reached when the system parameters
satisfy .Comment: 18 pages, 6 figures; to appear in J Chem Phy
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