39 research outputs found
The Power Spectrum of Rich Clusters of Galaxies on Large Spatial Scales
We present an analysis of the redshift-space power spectrum, , of rich
clusters of galaxies based on an automated cluster catalogue selected from the
APM Galaxy Survey. We find that can be approximated by a power law,
P(k)\proptok^{n}, with over the wavenumber range
0.04\hr. Over this range of wavenumbers, the APM cluster power
spectrum has the same shape as the power spectra measured for optical and IRAS
galaxies. This is consistent with a simple linear bias model in which different
tracers have the same power spectrum as that of the mass distribution but
shifted in amplitude by a constant biasing factor. On larger scales, the power
spectrum of APM clusters flattens and appears to turn over on a scale k \sim
0.03\hmpcrev. We compare the power spectra estimated from simulated APM
cluster catalogues to those estimated directly from cubical N-body simulation
volumes and find that the APM cluster survey should give reliable estimates of
the true power spectrum at wavenumbers k \simgt 0.02\hmpcrev. These results
suggest that the observed turn-over in the power spectrum may be a real feature
of the cluster distribution and that we have detected the transition to a near
scale-invariant power spectrum implied by observations of anisotropies in the
cosmic microwave background radiation. The scale of the turn-over in the
cluster power spectrum is in good agreement with the scale of the turn-over
observed in the power spectrum of APM galaxies.Comment: 9 pages, 7 ps figures, two style files, submitted to MNRAS. Un-xxx-ed
version available at
http://www-astro.physics.ox.ac.uk/research/preprints/aug97/cluspaper.ps.g
The Power Spectrum of IRAS Galaxies
We estimate the three-dimensional power spectrum of IRAS galaxies from the
QDOT and Jy redshift surveys. We use identical estimators for both surveys
and show how the results depend on the weights assigned to the galaxies. The
power spectrum for the QDOT survey is steeper and has a higher amplitude at
wavenumbers (where is Hubble's constant in
units of 100 \kmsmpc) than the power spectrum derived from the Jy
sample. However, the QDOT power spectrum is sensitive to a small number of
galaxies in the Hercules supercluster, in agreement with a recent analysis of
galaxy counts in cells in these surveys. We argue that the QDOT results are an
upward fluctuation. We combine the two surveys to derive our best estimate of
the power spectrum of IRAS galaxies. This is shallower and has a lower
amplitude on scales \simlt 0.1 h {\rm Mpc}^{-1} than the power spectrum
derived by Feldman \et (1994) from the QDOT survey alone. The power spectrum of
the combined surveys is well described by the linear theory power spectrum of a
scale-invariant cold dark matter model with .Comment: 5 pages, uuencoded compressed PostScript, 3 figures included.
Accepted for publication in MNRAS pink page
How to find MACHOs in the Virgo Cluster
We discuss the feasibility of finding extra-galactic MACHOs by monitoring
quasars behind the Virgo cluster of galaxies. We show that with only a modest
observing programme one could detect several MACHOs in the mass range 1 X
10^{-5} to 2 X 10^{-2} solar masses if they make a significant contribution to
the mass of Virgo. The contamination by events from cosmologically distributed
MACHOs is estimated and is negligible if either the MACHO mass is greater than
about 10^{-4} solar masses or the quasar radius is greater than about 3 X
10^{15} cm.Comment: 5 pages, 1 figure, to appear in New Astronom
Density and Velocity Fields from the PSCz Survey
We present the results for the predicted density and peculiar velocity fields
and the dipole from the PSCz survey of 15,000 IRAS galaxies over 84% of the
sky. We find a significant component to the dipole arising between 6000 and
15,000 km/s, but no significant component from greater distances. The
misalignment with the CMB is 20 degrees. The most remarkable feature of the
PSCz model velocity field is a coherent large-scale flow along the baseline
connecting Perseus-Pisces, the Local Supercluster, Great Attractor and the
Shapley Concentration. We have measured the parameter beta using the amplitude
of the dipole, bulk flow and point by point comparisons between the individual
velocities of galaxies in the MarkIII and SFI datasets, and the large-scale
clustering distortion in redshift space.All our results are consistent with
beta = 0.6 +- 0.1.Comment: 8 pages, 8 figures. To appear in 'Towards an Understanding of Cosmic
Flows', Victoria, July 1999, eds Courteau,S., Strauss,M., Willick,J. PAS
Male or Female? The Answer Depends on When You Ask
Over 80 years ago, Bridges came to the conclusion that sex inDrosophila is determined by the X:A ratio. Doubts about this hypothesis are raised by taking a molecular look at how--and when--sex is determined
The Inverse Redshift-Space Operator: Reconstructing Cosmological Density and Velocity Fields
We present the linear inverse redshift space operator which maps the galaxy
density field derived from redshift surveys from redshift space to real space.
Expressions are presented for observers in both the CMBR and Local Group rest
frames. We show how these results can be generalised to flux--limited galaxy
redshift surveys. These results allow the straightforward reconstruction of
real space density and velocity fields without resort to iterative or
numerically intensive inverse methods. As a corollary to the inversion of the
density in the Local Group rest frame we present an expression for estimating
the real space velocity dipole from redshift space, allowing one to estimate
the Local Group dipole without full reconstruction of the redshift survey. We
test these results on some simple models and find the reconstruction is very
accurate. A new spherical harmonic representation of the redshift distortion
and its inverse is developed, which simplifies the reconstruction and allows
analytic calculation of the properties of the reconstructed redshift survey. We
use this representation to analyse the uncertainties in the reconstruction of
the density and velocity fields from redshift space, due to only a finite
volume being available. Both sampling and shot-noise variance terms are derived
and we discuss the limits of reconstruction analysis. We compare the
reconstructed velocity field with the true velocity field and show that
reconstruction in the Local Group rest frame is preferable, since this
eliminates the major source of uncertainty from the dipole mode. These results
can be used to transform redshift surveys to real space and may be used as part
of a full likelihood analysis to extract cosmological parameters.Comment: 13 pages (Latex), 6 postscript figures included, accepted for
publication in MNRA
Evaluation of the effect of Cooled HaEmodialysis on Cognitive function in patients suffering with end-stage KidnEy Disease (E-CHECKED): feasibility randomised control trial protocol
BACKGROUND: Cognitive impairment is common in haemodialysis (HD) patients and is associated independently with depression and mortality. This association is poorly understood, and no intervention is proven to slow cognitive decline. There is evidence that cooler dialysis fluid (dialysate) may slow white matter changes in the brain, but no study has investigated the effect of cooler dialysate on cognition. This study addresses whether cooler dialysate can prevent the decline in cognition and improve quality of life (QOL) in HD patients. METHODS: This is a multi-site prospective randomised, double-blinded feasibility trial. SETTING: Four HD units in the UK. PARTICIPANTS AND INTERVENTIONS: Ninety HD patients randomised (1:1) to standard care (dialysate temperature 36.5 °C) or intervention (dialysate temperature 35 °C) for 12 months. PRIMARY OUTCOME MEASURE: Change in cognition using the Montreal Cognitive Assessment (MoCA). SECONDARY OUTCOME MEASURES: Recruitment and attrition rates, reasons for non-recruitment, frequency of intradialytic hypotension, depressive symptom scores, patient and carers burden, a detailed computerised cognitive test and QOL assessments. ANALYSIS: mixed method approach, utilising measurement of cognition, questionnaires, physiological measurements and semi-structured interviews. DISCUSSION: The results of this feasibility trial will inform the design of a future adequately powered substantive trial investigating the effect of dialysate cooling on prevention and/or slowing in cognitive decline in patients undergoing haemodialysis using a computerised battery of neuro-cognitive tests. The main hypothesis that would be tested in this future trial is that patients treated with regular conventional haemodialysis will have a lesser decline in cognitive function and a better quality of life over 1 year by using cooler dialysis fluid at 35 °C, versus a standard dialysis fluid temperature of 36.5 °C. This also should reflect in improvements in their abilities for activities of daily living and therefore reduce carers' burden. If successful, the treatment could be universally applied at no extra cost. TRIAL REGISTRATION: ClinicalTrials.gov NCT03645733 . Registered retrospectively on 24 August 2018
The PID Odyssey 2030:outlooks, unmet needs, hurdles, and opportunities — proceedings from the IPOPI global multi-stakeholders’ summit (June 2022)
IPOPI held its first Global Multi-Stakeholders’ Summit on 23-24 June 2022 in Cascais, Portugal. This IPOPI initiative was designed to set the stage for a stimulating forward-thinking meeting and brainstorming discussion among stakeholders on the future priorities of the PID community. All participants were actively engaged in the entire Summit, bringing provocative questions to ensure a high level of discussion and engagement, and partnered in identifying the outlooks, unmet needs, hurdles and opportunities of PIDs for 2030. The topics that were covered include diagnosis (e.g., newborn screening [NBS], genomic sequencing— including ethical aspects on the application of genomics on NBS, the role of more accurate and timely diagnostics in impacting personalized management), treatment (e.g., the therapeutic evolution of immunoglobulins in a global environment, new therapies such as targeted therapies, new approaches in curative therapies), the interactions of Primary ID with Secondary ID, Autoinflammatory Diseases and other diseases as the field experiences an incessant evolution, and also the avenues for research in the field of humanities and human sciences such as Patient-Reported Outcome Measures (PROMs), Patient-Reported Experience Measures (PREMs), and Health-Related Quality Of Life (HRQoL). During this meeting, all participants contributed to the drafting of recommendations based on our common understanding of the future opportunities, challenges, and scenarios. As a collection of materials, perspectives and summaries, they are succinct and impactful and may help determine some of the next key steps for the PID community.</p
Understanding 'non-genetic' inheritance : insights from molecular-evolutionary crosstalk
The idea for this paper was initially proposed by I.A.-K. and was further developed by all authors in a workshop generously funded by grant No 789240 from the European Research Council (ERC) to F.J.W. S.E.S. acknowledges support from Wesleyan University and The John Templeton Foundation.Understanding the evolutionary and ecological roles of 'non-genetic' inheritance (NGI) is daunting due to the complexity and diversity of epigenetic mechanisms. We draw on insights from molecular and evolutionary biology perspectives to identify three general features of 'non-genetic' inheritance systems: (i) they are functionally interdependent with, rather than separate from, DNA sequence; (ii) precise mechanisms vary phylogenetically and operationally; and (iii) epigenetic elements are probabilistic, interactive regulatory factors and not deterministic 'epialleles' with defined genomic locations and effects. We discuss each of these features and offer recommendations for future empirical and theoretical research that implements a unifying inherited gene regulation (IGR) approach to studies of 'non-genetic' inheritance.Publisher PDFPeer reviewe
The PID Odyssey 2030: outlooks, unmet needs, hurdles, and opportunities — proceedings from the IPOPI global multi-stakeholders’ summit (June 2022)
IPOPI held its first Global Multi-Stakeholders’ Summit on 23-24 June 2022 in Cascais, Portugal. This IPOPI initiative was designed to set the stage for a stimulating forward-thinking meeting and brainstorming discussion among stakeholders on the future priorities of the PID community. All participants were actively engaged in the entire Summit, bringing provocative questions to ensure a high level of discussion and engagement, and partnered in identifying the outlooks, unmet needs, hurdles and opportunities of PIDs for 2030. The topics that were covered include diagnosis (e.g., newborn screening [NBS], genomic sequencing— including ethical aspects on the application of genomics on NBS, the role of more accurate and timely diagnostics in impacting personalized management), treatment (e.g., the therapeutic evolution of immunoglobulins in a global environment, new therapies such as targeted therapies, new approaches in curative therapies), the interactions of Primary ID with Secondary ID, Autoinflammatory Diseases and other diseases as the field experiences an incessant evolution, and also the avenues for research in the field of humanities and human sciences such as Patient-Reported Outcome Measures (PROMs), Patient-Reported Experience Measures (PREMs), and Health-Related Quality Of Life (HRQoL). During this meeting, all participants contributed to the drafting of recommendations based on our common understanding of the future opportunities, challenges, and scenarios. As a collection of materials, perspectives and summaries, they are succinct and impactful and may help determine some of the next key steps for the PID community