1,771 research outputs found
The one-point PDF of the initial conditions of our local Universe from the IRAS PSC redshift catalogue
No full textThe algorithm ZTRACE of Monaco & Efstathiou is applied to the IRAS PSCz catalogue to reconstruct the initial conditions of our local Universe with a resolution down to similar to5 h(-1) Mpc. The one-point probability distribution function (PDF) of the reconstructed initial conditions is consistent with the assumptions that: (i) IRAS galaxies trace mass on scales of similar to5 h(-1) Mpc and (ii) the statistics of the primordial density fluctuations are Gaussian. We use simulated PSCz catalogues, constructed from N-body simulations with Gaussian initial conditions, to show that local non-linear bias can cause the recovered initial PDF (assuming no bias) to be non-Gaussian. However, for plausible bias models, the distortions of the recovered PDF would be difficult to detect using the volume finely sampled by the PSCz catalogue. So, for Gaussian initial conditions, a range of bias models remain compatible with our PSCz reconstruction results
Complex systems modeling for supply and demand in health and social care
No full textThis paper introduces a major new cross-disciplinary research project that looks at the UK health and social care system, as part of an ambitious, broader initiative to apply methods from complexity science to a range of key global challenges. This particular project aims to develop new, integrated models for the supply and demand of both health and social care, in the context of the societal change brought about by migration, mobility and the ageing population. We discuss the background to the work, and the broad way in which we intend to leverage complexity science. This is made more specific with a brief discussion on existing demographic models, and some examples of model-building in progress. We conclude with a glimpse into the subtly difficult problems of fostering such innovative interdisciplinarity
A Simple Empirically Motivated Template for the Unresolved Thermal Sunyaev-Zeldovich Effect
No full texta
Misurare la percezione di caring in pazienti e infermieri: validazione italiana del Caring Behaviors Inventory (CBIta).
No full textIl caring è concetto chiave dell’assistenza infermieristica e la sua espressione nell’assistenza può modificare esiti di qualità nei servizi sanitari, come la soddisfazione del paziente, e migliorare esiti organizzativi come i tassi di turnover e il benessere degli operatori sanitari.
Il Caring Behaviors Inventory è uno strumento diffuso e validato a livello internazionale che valuta la percezione di caring ricevuto e erogato, rispettivamente, da pazienti e infermieri. Questo studio presenta il processo di validazione italiana della versione a 24 item del Caring Behaviors Inventory (CBI-24) in un campione di pazienti e infermieri in contesti chirurgici. La validità di contenuto della versione italiana dello strumento è stata garantita mediante processo di forward-backward translation. Lo strumento è stato somministrato ad un campione di 213 pazienti (tasso di risposta 88%) e 178 infemieri (tasso di risposta 95%), mostrando valori di affidabilità (α di Cronbach), rispettivamente, di 0.94 e 0.92. L’analisi fattoriale confermativa suggerisce la validità del modello a 4 fattori. La versione italiana dello strumento può essere considerata valida e affidabile. Gli elevati tassi di risposta indicano inoltre alti livelli di accettabilità da parte di pazienti e infermieri e suggeriscono la sua fruibilità per una valutazione sistematica dell’assistenza nei contesti clinici e lo studio degli antecedenti del turnover e del benessere organizzativo
Models of hierarchical: galaxy formation
No full textA semi-analytic galaxy formation model, N-body GALFORM, is developed which uses outputs from an N-body simulation to follow the merger histories of dark matter halos and treats baryonic processes using the semi-analytic model of Cole et al. We find that, apart from limited mass resolution, the only significant differences between this model and the Monte-Carlo based model of Cole et al. are due to known inaccuracies in the distribution of halo progenitor masses in the Monte-Carlo method. N-body GALFORM is used to compare Smooth Particle Hydrodynamics (SPH) and semi-analytic calculations of radiative cooling in the absence of star formation. We consider two cases: firstly, a simulation of a representative volume of the Universe with relatively poor mass resolution, and, secondly, a high resolution simulation of the formation of a single galaxy. We find good agreement between the models in terms of the mass of gas which cools in each halo, the masses of individual galaxies, and the spatial distribution of the galaxies. The semi-analytic model is then compared with a realistic, high-resolution galaxy simulation which includes prescriptions for star formation and feedback. A semi-analytic model without feedback is found to best reproduce the masses of the simulated galaxy and its progenitors. This model is used to populate a large volume with semi-analytic galaxies. The resulting luminosity function has an order of magnitude too many galaxies at high and low luminosities. We conclude that, while SPH and semi-analytic cooling calculations are largely consistent and therefore likely to be reasonably reliable, current numerical models of galaxy formation still contain major uncertainties due to the treatment of feedback, which will lead them to predict very different galaxy populations. Further work is required to find simulation algorithms which can simultaneously produce realistic individual galaxies and a population with reasonable statistical properties
NEW QUALITATIVE FEATURES IN INTRAMOLECULAR DYNAMICS: SIMPLE EXAMPLES
No full textAuthor Institution: Universite du Littoral, UMR 8101 du CNRS, 59140; Dunkerque France; Rijksuniversiteit Groningen, Groningen 9747 AC, The NetherlandsMany simple quantum atomic or molecular systems possess several mutually commuting (exactly or approximately) observables (energy, angular momentum, ...). We will demonstrate that the patterns formed by joint spectra of mutually commuting operators show several specific qualitative features associated with bifurcations, monodromy, etc. Generic modifications of such patterns under the variation of one or several external parameters as well as their relation to the symmetry of the system will be discussed. As concrete systems, we will use the examples of hydrogen atom in the presence of small static electric and magnetic field, vibrational structure of triatomic linear molecules with Fermi resonance and small detuning (CO, and CS like molecules), rovibrational structure of tetrahedral molecules (such as methane or silane). Different patterns in the joint spectra of commuting operators (integrals of motion) are related to different dynamical regimes of the corresponding classical systems and to the presence of singularities of classical fibrations defined by the integrable approximations to these systems. In quantum analog systems, such singularities manifest themselves as \emph{defects of regular lattices\/}. The difference between the standard defects used in solid state physics (dislocations, disclinations, vacancies) and defects which appear in the joint spectra due to the presence of monodromy will be explained. K. Efstathiou, D. Sadovskii, B. Zhilinskii. Proc. Roy. Soc. A, submitted. R. Cushman, H. R. Dullin, A. Giacobbe, D. D. Holm, M. Joyeux, P. Lynch, D.A. Sadovskii, B. Zhilinskii. Phys. Rev. Lett., 93 024302-1-4 (2004) K. Efstathiou, D.A. Sadovskii and B.I. Zhilinskii. SIADS, 3, 261-351 (2004)
Reconstructing the primordial power spectrum
No full textWe reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large-scale structure data from the 2 Degree Field Galaxy Redshift Survey (2dFGRS). We tested four parametrizations, taking into account the uncertainties in four cosmological parameters. First we parametrize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (l = 2, 3, 4) are included in the analysis. Secondly, to investigate further the low CMB large-scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at k(c) similar to 3 x 10(-4) Mpc(-1), although k(c) = 0 (no cut) is not ruled out. Thirdly, we use a model independent parametrization, with 16 bands in wavenumber, and find no obvious sign of deviation from a power-law spectrum on the scales investigated. Furthermore, the values of the other cosmological parameters defining the model remain relatively well constrained despite the freedom in the shape of the initial power spectrum. Finally we investigate a model motivated by double inflation, in which the power spectrum has a break between two characteristic wavenumbers. We find that if a break is required to be in the range 0.01 < k/Mpc(-1) < 0.1 then the ratio of amplitudes across the break is constrained to be 1.23 +/- 0.14. Our results are consistent with a power-law spectrum that is featureless and close to scale invariant over the wavenumber range 0.005 less than or similar to k/Mpc(-1) less than or similar to 0.15, with a hint of a decrease in power on the largest scales
Cosmological parameter estimation using Very Small Array data out to ℓ= 1500
No full textWe estimate cosmological parameters using data obtained by the Very Small Array (VSA) in its extended configuration, in conjunction with a variety of other cosmic microwave background (CMB) data and external priors. Within the flat Λ cold dark matter (ΛCDM) model, we find that the inclusion of high-resolution data from the VSA modifies the limits on the cosmological parameters as compared to those suggested by the Wilkinson Microwave Anisotropy Probe (WMAP) alone, while still remaining compatible with their estimates. We find that Ωbh2= 0.0234+0.0012−0.0014, Ωdmh2= 0.111+0.014−0.016, h= 0.73+0.09−0.05, nS= 0.97+0.06−0.03, 1010AS= 23+7−3 and τ= 0.14+0.14−0.07 for WMAP and VSA when no external prior is included. On extending the model to include a running spectral index of density fluctuations, we find that the inclusion of VSA data leads to a negative running at a level of more than 95 per cent confidence ( nrun=−0.069 ± 0.032 ), something that is not significantly changed by the inclusion of a stringent prior on the Hubble constant. Inclusion of prior information from the 2dF galaxy redshift survey reduces the significance of the result by constraining the value of Ωm. We discuss the veracity of this result in the context of various systematic effects and also a broken spectral index model. We also constrain the fraction of neutrinos and find that fν < 0.087 at 95 per cent confidence, which corresponds to mν < 0.32 eV when all neutrino masses are equal. Finally, we consider the global best fit within a general cosmological model with 12 parameters and find consistency with other analyses available in the literature. The evidence for nrun < 0 is only marginal within this model
- …
