555 research outputs found
Unethical aspects of homeopathic dentistry
In the last year there has been a great deal of public debate about homeopathy, the system of alternative medicine whose main principles are that like cures like and that potency increases relative to dilution. The House of Commons Select Committee on Science and Technology concluded in November 2009 that there is no evidence base for homeopathy, and agreed with some academic commentators that homeopathy should not be funded by the NHS. While homeopathic doctors and hospitals are quite commonplace, some might be surprised to learn that there are also many homeopathic dentists practising in the UK. This paper examines the statements made by several organisations on behalf of homeopathic dentistry and suggests that they are not entirely ethical and may be in breach of various professional guidelines
The first VLBI image of an Infrared-Faint Radio Source
Context: To investigate the joint evolution of active galactic nuclei and
star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia
Telescope Compact Array of the Chandra Deep Field South and the European Large
Area ISO Survey - S1 we have identified a class of objects which are strong in
the radio but have no detectable infrared and optical counterparts. This class
has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002
have been classified as IFRS. It is not known what these objects are. Methods:
To address the many possible explanations as to what the nature of these
objects is we have observed four sources with the Australian Long Baseline
Array. Results: We have detected and imaged one of the four sources observed.
Assuming that the source is at a high redshift, we find its properties in
agreement with properties of Compact Steep Spectrum sources. However, due to
the lack of optical and infrared data the constraints are not particularly
strong.Comment: Accepted for publication in Astronomy and Astrophysics, 5 pages,
needs aa.cl
On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening
We assess the contribution of dynamical hardening by direct three-body
scattering interactions to the rate of stellar-mass black hole binary (BHB)
mergers in galactic nuclei. We derive an analytic model for the single-binary
encounter rate in a nucleus with spherical and disk components hosting a
super-massive black hole (SMBH). We determine the total number of encounters
needed to harden a BHB to the point that inspiral due to
gravitational wave emission occurs before the next three-body scattering event.
This is done independently for both the spherical and disk components. Using a
Monte Carlo approach, we refine our calculations for to include
gravitational wave emission between scattering events. For astrophysically
plausible models we find that typically 10.
We find two separate regimes for the efficient dynamical hardening of BHBs:
(1) spherical star clusters with high central densities, low velocity
dispersions and no significant Keplerian component; and (2) migration traps in
disks around SMBHs lacking any significant spherical stellar component in the
vicinity of the migration trap, which is expected due to effective orbital
inclination reduction of any spherical population by the disk. We also find a
weak correlation between the ratio of the second-order velocity moment to
velocity dispersion in galactic nuclei and the rate of BHB mergers, where this
ratio is a proxy for the ratio between the rotation- and dispersion-supported
components. Because disks enforce planar interactions that are efficient in
hardening BHBs, particularly in migration traps, they have high merger rates
that can contribute significantly to the rate of BHB mergers detected by the
advanced Laser Interferometer Gravitational-Wave Observatory.Comment: 13 pages, 9 figures, accepted for publication in MNRA
The 15-43 GHz parsec-scale circular polarization of 41 active galactic nuclei
We present the results of parsec-scale circular-polarization measurements based on Very Long Baseline Array data for a number of radio-bright, core-dominated active galactic nuclei obtained simultaneously at 15, 22 and 43 GHz. The degrees of circular polarization m(c) for the Very Long Baseline Interferometry (VLBI) core region at 15 GHz are similar to the values reported earlier at this wavelength, with typical values of a few tenths of a per cent. We find that mc as often rises as falls with increasing frequency between 15 and 22 GHz, while the degree of circular polarization at 43 GHz is in all cases higher than at 22 and 15 GHz. This behaviour seems contrary to expectations, since the degree of circular polarization from both synchrotron radiation and the Faraday conversion of linear to circular polarization - the two main mechanisms considered thus far in the literature - should decrease towards higher frequencies if the source is homogeneous. The increase in mc at 43 GHz may be due to the presence of regions of both positive and negative circular polarization with different frequency dependences ( but decreasing with increasing frequency) on small scales within the core region; alternatively, it may be associated with the intrinsic inhomogeneity of a Blandford-Konigl like jet. In several objects, the detected circular polarization appears to be near, but not coincident with, the core, although further observations are needed to confirm this. We find several cases of changes in sign with frequency, most often between 22 and 43 GHz. We find tentative evidence for transverse structure in the circular polarization of 1055+018 and 1334-127, that is consistent with their being generated by either the synchrotron mechanism or the Faraday conversion in a helical magnetic field. Our results confirm the earlier finding that the sign of the circular polarization at a given observing frequency is generally consistent across epochs separated by several years or more, suggesting stability of the magnetic-field orientation in the innermost jets
Stage of perinatal development regulates skeletal muscle mitochondrial biogenesis and myogenic regulatory factor genes with little impact of growth restriction or cross-fostering
Foetal growth restriction impairs skeletal muscle development and adult muscle mitochondrial biogenesis. We hypothesized that key genes involved in muscle development and mitochondrial biogenesis would be altered following uteroplacental insufficiency in rat pups, and improving postnatal nutrition by cross-fostering would ameliorate these deficits. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed on day 18 of gestation. Males and females were investigated at day 20 of gestation (E20), 1 (PN1), 7 (PN7) and 35 (PN35) days postnatally. A separate cohort of Control and Restricted pups were cross-fostered onto a different Control or Restricted mother and examined at PN7. In both sexes, peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α (PGC-1α), cytochrome c oxidase subunits 3 and 4 (COX III and IV) and myogenic regulatory factor 4 expression increased from late gestation to postnatal life, whereas mitochondrial transcription factor A, myogenic differentiation 1 (MyoD), myogenin and insulin-like growth factor I (IGF-I) decreased. Foetal growth restriction increased MyoD mRNA in females at PN7, whereas in males IGF-I mRNA was higher at E20 and PN1. Cross-fostering Restricted pups onto a Control mother significantly increased COX III mRNA in males and COX IV mRNA in both sexes above controls with little effect on other genes. Developmental age appears to be a major factor regulating skeletal muscle mitochondrial and developmental genes, with growth restriction and cross-fostering having only subtle effects. It therefore appears that reductions in adult mitochondrial biogenesis markers likely develop after weaning.<br /
Ocean Acidification: An Emerging Threat to our Marine Environment
This report aims to provide a concise overview of the present state of scientific knowledge of ocean acidification and its likely impacts on organisms and ocean ecosystems. This is particularly relevant in the context of the possible implications and ramifications of ocean acidification for Irish marine areas. Discussion on how mankind’s CO2 emissions are changing ocean chemistry; consequences of ocean acidification; ocean acidification as an emerging cause for concern; international policy drivers, strategies and necessary actions; and research and information needs are presented. Ireland’s marine location and extensive marine resources in our shelf seas, Atlantic waters and habitats of the west coast mean we are uniquely positioned to contribute to international scientific efforts to monitor and understand the impacts of ocean acidification. Monitoring and research of key biological, chemical and physical factors in these regions will allow us to determine the current status of Irish Marine waters, the rate of change in the carbonate cycle and the influence of this change on natural communities and ecosystems. The Marine Institute’s SSTI funded Sea Change programme includes a Rapid Climate Change programme. Under this, a two year collaborative project between NUI Galway and Marine Institute ‘Impacts of increased atmospheric CO2 on ocean chemistry and ecosystems’ is developing capabilities for measuring pCO2 fluxes, inorganic carbon chemistry and pH and is initiating baseline measurements of these parameters in coastal and offshore waters. This report summarises the issues and state of knowledge and communicates ongoing monitoring and research needs into acidification.Funder: Marine Institut
The HST Survey of BL Lac Objects: Gravitational Lens Candidates and Other Unusual Sources
We present HST observations of seven unusual objects from the HST ``snapshot
survey'' of BL Lac objects, of which four are gravitational lens candidates. In
three cases a double point sources is observed: 0033+595, with 1.58 arcsec
separation, and 0502+675 and 1440+122, each with arcsec separation.
The last two also show one or more galaxies, which could be either host or
lensing galaxies. If any are confirmed as lenses, these BL Lac objects are
excellent candidates for measuring H via gravitational time delay because
of their characteristic rapid, high amplitude variability. An additional
advantage is that, like other blazars, they are likely superluminal radio
sources, in which case the source plane is mapped out over a period of years,
providing strong additional constraints on the lensing mass distribution. The
fourth gravitational lens candidate is 1517+656, which is surrounded by three
arclets forming an almost perfect ring of radius 2.4 arcsec. If this is indeed
an Einstein ring, it is most likely a background source gravitationally lensed
by the BL Lac object host galaxy and possibly a surrounding group or cluster.
In the extreme case that all four candidates are true lenses, the derived
frequency of gravitational lensing in this BL Lac sample would be an order of
magnitude higher than in comparable quasar samples.
We also report on three other remarkable BL Lac objects: 0138-097, which is
surrounded by a large number of close companion galaxies; 0806+524, whose host
galaxy contains an uncommon arc-like structure; and 1959+650, which is hosted
by a gas rich elliptical galaxy with a prominent dust lane of .Comment: 29 pages in total, 12 figure
Predictors of outcome in sciatica patients following an epidural steroid injection:the POiSE prospective observational cohort study protocol
INTRODUCTION: Sciatica can be very painful and, in most cases, is due to pressure on a spinal nerve root from a disc herniation with associated inflammation. For some patients, the pain persists, and one management option is a spinal epidural steroid injection (ESI). The aim of an ESI is to relieve leg pain, improve function and reduce the need for surgery. ESIs work well in some patients but not in others, but we cannot identify these patient subgroups currently. This study aims to identify factors, including patient characteristics, clinical examination and imaging findings, that help in predicting who does well and who does not after an ESI. The overall objective is to develop a prognostic model to support individualised patient and clinical decision-making regarding ESI. METHODS: POiSE is a prospective cohort study of 439 patients with sciatica referred by their clinician for an ESI. Participants will receive weekly text messages until 12 weeks following their ESIand then again at 24 weeks following their ESI to collect data on leg pain severity. Questionnaires will be sent to participants at baseline, 6, 12 and 24 weeks after their ESI to collect data on pain, disability, recovery and additional interventions. The prognosis for the cohort will be described. The primary outcome measure for the prognostic model is leg pain at 6 weeks. Prognostic models will also be developed for secondary outcomes of disability and recovery at 6 weeks and additional interventions at 24 weeks following ESI. Statistical analyses will include multivariable linear and logistic regression with mixed effects model. ETHICS AND DISSEMINATION: The POiSE study has received ethical approval (South Central Berkshire B Research Ethics Committee 21/SC/0257). Dissemination will be guided by our patient and public engagement group and will include scientific publications, conference presentations and social media.</p
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