4,099 research outputs found
Scottish theme towns: have new identities enhanced development?
Three small towns in southwest Scotland have recently been branded as distinct theme towns, based on books, artists and food. This is an attempt to make them more attractive to visitors and thereby improve their economy. The objective of this research is to establish whether the new identities possessed by the towns have enhanced their development. It is argued, using data reviewing the past decade, that they have all developed, albeit at different rates, in terms of the economy and culture. Moreover, it is maintained that social capital has been enhanced and is a factor whose importance has been under-appreciated by planners and observers of this type of process. The relevance of the new identity to the pre-branding identity is also seen as a factor in successful development and ideas of authenticity and heritage are brought to bear on the relationship
Tracking pulsar dispersion measures using the GMRT
In this paper, we describe a novel experiment for the accurate estimation of
pulsar dispersion measures using the Giant Metre-wave Radio Telescope. This
experiment was carried out for a sample of twelve pulsars, over a period of
more than one year (January 2001 to May 2002) with observations about once
every fortnight. At each epoch, the pulsar DMs were obtained from simultaneous
dual frequency observations, without requiring any absolute timing information.
The DM estimates were obtained from both the single pulse data streams and from
the average profiles. The accuracy of the DM estimates at each epoch is ~ 1
part in 10^4 or better, making the data set useful for many different kinds of
studies. The time series of DM shows significant variations on time scales of
weeks to months for most of the pulsars. A comparison of the mean DM values
from these data show significant deviations from catalog values (as well as
from other estimates in literature) for some of the pulsars, with PSR B1642-03
showing the most notable changes. From our analysis results it appears that
constancy of pulsar DMs (at the level of 1 in 10^3 or better) can not be taken
for granted. For PSR B2217+47, we see evidence for a large-scale DM gradient
over a one year period, which is modeled as being due to a blob of enhanced
electron density sampled by the line of sight. For some pulsars, including
pulsars with fairly simple profiles like PSR B1642-03, we find evidence for
small changes in DM values for different frequency pairs of measurement, a
result that needs to be investigated in detail. Another interesting result is
that we find significant differences in DM values obtained from average
profiles and single pulse data.Comment: 10 pages, 7 Postscript figures, to be published in MNRA
The distance to the Vela pulsar gauged with HST parallax oservations
The distance to the Vela pulsar (PSR B0833-45) has been traditionally assumed
to be 500 pc. Although affected by a significant uncertainty, this value stuck
to both the pulsar and the SNR. In an effort to obtain a model free distance
measurement, we have applied high resolution astrometry to the pulsar V~23.6
optical counterpart. Using a set of five HST/WFPC2 observations, we have
obtained the first optical measurement of the annual parallax of the Vela
pulsar. The parallax turns out to be 3.4 +/- 0.7 mas, implying a distance of
294(-50;+76) pc, i.e. a value significantly lower than previously believed.
This affects the estimate of the pulsar absolute luminosity and of its emission
efficiency at various wavelengths and confirms the exceptionally high value of
the N_e towards the Vela pulsar. Finally, the complete parallax data base
allows for a better measurement of the Vela pulsar proper motion
(mu_alpha(cos(delta))=-37.2 +/- 1.2 mas/yr; mu_delta=28.2 +/- 1.3 mas/yr after
correcting for the peculiar motion of the Sun) which, at the parallax distance,
implies a transverse velocity of ~65 km/s. Moreover, the proper motion position
angle appears specially well aligned with the axis of symmetry of the X-ray
nebula as seen by Chandra. Such an alignment allows to assess the space
velocity of the Vela pulsar to be ~81 km/s.Comment: LaTeX, 21 pages, 5 figures. Accepted for publication in Ap
Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory
We investigate the light-curve properties of a sample of 26 spectroscopically
confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar
Transient Factory (PTF) survey. These events are brighter than SNe Ib/c and SNe
Ic-BL, on average, by about 4 and 2~mag, respectively. The peak absolute
magnitudes of SLSNe-I in rest-frame band span ~mag, and these peaks are not powered by radioactive Ni,
unless strong asymmetries are at play. The rise timescales are longer for SLSNe
than for normal SNe Ib/c, by roughly 10 days, for events with similar decay
times. Thus, SLSNe-I can be considered as a separate population based on
photometric properties. After peak, SLSNe-I decay with a wide range of slopes,
with no obvious gap between rapidly declining and slowly declining events. The
latter events show more irregularities (bumps) in the light curves at all
times. At late times, the SLSN-I light curves slow down and cluster around the
Co radioactive decay rate. Powering the late-time light curves with
radioactive decay would require between 1 and 10 of Ni masses.
Alternatively, a simple magnetar model can reasonably fit the majority of
SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay
of Co, up to days from explosion. The resulting spin values do
not correlate with the host-galaxy metallicities. Finally, the analysis of our
sample cannot strengthen the case for using SLSNe-I for cosmology.Comment: 120 pages, 48 figures, 78 tables. ApJ in pres
Multiband description of the upper critical field of bulk FeSe
The upper critical field of multiband superconductors can be an essential quantity to unravel the nature of
superconducting pairing and its interplay with the electronic structure. Here we experimentally map out the
complete upper critical field phase diagram of FeSe for different magnetic field orientations at temperatures
down to 0.3 K using both resistivity and torque measurements. The temperature dependence of the upper critical
field reflects that of a multiband superconductor and requires a two-band description in the clean limit with band
coupling parameters favoring interband over intraband interactions. Despite the relatively small Maki parameter
in FeSe of α ∼ 1.6, the multiband description of the upper critical field is consistent with the stabilization of
a Fulde-Ferrell-Larkin-Ovchinnikov state below T /Tc ∼ 0.3. We find that the anomalous behavior of the upper
critical field is linked to a departure from the single-band picture, and FeSe provides a clear example of where
multiband effects and the strong anisotropy of the superconducting gap need to be taken into account
The aetiology of rickets-like lower limb deformities in Malawian children
Summary: Debilitating rickets-like lower limb deformities are common in children throughout the world, particularly in Malawi, Africa where the causes are unknown. We have identified that Blount disease and calcium deficiency rickets are the likely causes of these deformities and propose calcium supplementation as a potential treatment of Malawian rickets.
Introduction: Surgical correction of rickets-like lower limb deformities is the most common paediatric operation performed at Beit Cure Orthopaedic Hospital, Malawi. The aim of this study was to investigate the aetiology of these deformities.
Methods: Children with a tibio-femoral angle of deformity >20° were enrolled (n = 42, 3.0–15.0 years). Anthropometric and early life and well-being data were collected. Early morning serum and urine samples were collected on the morning of the operation for markers of calcium and phosphate homeostasis. Knee radiographs were obtained, and the children were diagnosed with either Blount (BD, n = 22) or evidence of rickets disease (RD, n = 20). As BD is a mechanical rather than metabolic disease, BD were assumed to be biochemically representative of the local population and thus used as a local reference for RD.
Results: There were no differences in anthropometry or early life experiences between BD and RD. Parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, total alkaline phosphatase and urinary phosphate were significantly higher and serum phosphate, 25-hydroxyvitamin D (25OHD) and tubular maximal reabsorption of phosphate significantly lower in RD than BD. There was no difference in serum calcium, fibroblast growth factor 23 or markers of iron status between groups. All children had 25OHD > 25 nmol/L.
Conclusions: Vitamin D deficiency is not implicated in the aetiology of RD or BD in Malawian children. The cause of RD in Malawi is likely to be dietary calcium deficiency leading to elevated PTH resulting in increased losses of phosphate from the bone and glomerular filtrate. The causes of BD remain unclear; there was no evidence in support of previously suggested risk factors such as being overweight or starting to walk early. Prior to surgical intervention, supplementation with calcium should be considered for children with RD
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Vegetation plays an important role in mediating future water resources
Future environmental change is expected to modify the global hydrological cycle, with consequences for the regional distribution of freshwater supplies. Regional precipitation projections, however, differ largely between models, making future water resource projections highly uncertain. Using two representative concentration pathways and nine climate models, we estimate 21st century water resources across Australia, employing both a process-based dynamic vegetation model and a simple hydrological framework commonly used in water resource studies to separate the effects of climate and vegetation on water resources. We show surprisingly robust, pathway-independent regional patterns of change in water resources despite large uncertainties in precipitation projections. Increasing plant water use efficiency (due to the changing atmospheric CO2) and reduced green vegetation cover (due to the changing climate) relieve pressure on water resources for the highly populated, humid coastal regions of eastern Australia. By contrast, in semi-arid regions across Australia, runoff declines are amplified by CO2-induced greening, which leads to increased vegetation water use. These findings highlight the importance of including vegetation dynamics in future water resource projections
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