Lightcone fluctuations in quantum gravity and extra dimensions

We discuss how compactified extra dimensions may have potentially observable effects which grow as the compactification scale decreases. This arises because of lightcone fluctuations in the uncompactified dimensions which can result in the broadening of the spectral lines from distant sources. We analyze this effect in a five dimensional model, and argue that data from gamma ray burst sources require the compactification length to be greater than about $10^5$ cm in this model.Comment: Two additional references adde

Testing MONDian Dark Matter with Galactic Rotation Curves

MONDian dark matter (MDM) is a new form of dark matter quantum that naturally accounts for Milgrom's scaling, usually associated with modified Newtonian dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at cluster and cosmic scales. In this paper, we provide the first observational test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies (z approximately 0.003). For comparison, we also fit the galactic rotation curves using MOND, and CDM. We find that all three models fit the data well. The rotation curves predicted by MDM and MOND are virtually indistinguishable over the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM density profiles are compared. We also compare with MDM the dark matter density profiles arising from MOND if Milgrom's formula is interpreted as Newtonian gravity with an extra source term instead of as a modification of inertia. We find that discrepancies between MDM and MOND will occur near the center of a typical spiral galaxy. In these regions, instead of continuing to rise sharply, the MDM mass density turns over and drops as we approach the center of the galaxy. Our results show that MDM, which restricts the nature of the dark matter quantum by accounting for Milgrom's scaling, accurately reproduces observed rotation curves.Comment: Preprint number IPMU13-0147. Accepted for publication in Ap

Macroscopic detection of the strong stochasticity threshold in Fermi-Pasta-Ulam chains of oscillators

The largest Lyapunov exponent of a system composed by a heavy impurity embedded in a chain of anharmonic nearest-neighbor Fermi-Pasta-Ulam oscillators is numerically computed for various values of the impurity mass $M$. A crossover between weak and strong chaos is obtained at the same value $\epsilon_{_T}$ of the energy density $\epsilon$ (energy per degree of freedom) for all the considered values of the impurity mass $M$. The threshold \epsi lon_{_T} coincides with the value of the energy density $\epsilon$ at which a change of scaling of the relaxation time of the momentum autocorrelation function of the impurity ocurrs and that was obtained in a previous work ~[M. Romero-Bastida and E. Braun, Phys. Rev. E {\bf65}, 036228 (2002)]. The complete Lyapunov spectrum does not depend significantly on the impurity mass $M$. These results suggest that the impurity does not contribute significantly to the dynamical instability (chaos) of the chain and can be considered as a probe for the dynamics of the system to which the impurity is coupled. Finally, it is shown that the Kolmogorov-Sinai entropy of the chain has a crossover from weak to strong chaos at the same value of the energy density that the crossover value $\epsilon_{_T}$ of largest Lyapunov exponent. Implications of this result are discussed.Comment: 6 pages, 5 figures, revtex4 styl

New observations of the NGC 1275 phenomenon

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Patient-reported outcomes following treatment with the human GLP-1 analogue liraglutide or glimepiride in monotherapy: results from a randomized controlled trial in patients with type 2 diabetes

Aim: As weight gain and hypoglycaemia associated with glimepiride therapy can negatively impact weight perceptions, psychological well-being and overall quality of life in type 2 diabetes, we investigated whether liraglutide treatment could improve these factors

Blasts and shocks in the disc of NGC 4258

We present integral field spectroscopic observations of the central region of the active galaxy NGC 4258 obtained with the fibre IFU system INTEGRAL. We have been able to detect cold neutral gas by means of the interstellar NaD doublet absorption and to trace its distribution and kinematics with respect to the underlying disc. The neutral gas is blue-shifted with projected velocities in the 120--370 km/s range. We have also detected peculiar kinematics in part of the ionized gas in this region by means of a careful kinematic decomposition. The bipolar spatial distribution of the broader component is roughly coincident with the morphology of the X-ray diffuse emission. The kinematics of this gas can be explained in terms of expansion at very high (projected) velocities of up to 300 km/s. The observations also reveal the existence of a strip of neutral gas, parallel to the major kinematic axis, that is nearly coincident with a region of very high [SII]/H$\alpha$ ratio tracing the shocked gas. Our observations are consistent with the jet model presented by \cite{wilsonetal01} in which a cocoon originating from the nuclear jet is shocking the gas in the galaxy disc. Alternatively, our observations are also consistent with the bipolar hypershell model of \cite{Sofue80} and \cite{SofueandVogler01}. On balance, we prefer the latter model as the most likely explanation for the puzzling features of this peculiar object.Comment: 7 pages, 10 colour figures. Accepted for publication in MNRAS

Minor-axis velocity gradients in disk galaxies

We present the ionized-gas kinematics and photometry of a sample of 4 spiral galaxies which are characterized by a zero-velocity plateau along the major axis and a velocity gradient along the minor axis, respectively. By combining these new kinematical data with those available in the literature for the ionized-gas component of the S0s and spirals listed in the Revised Shapley-Ames Catalog of Bright Galaxies we realized that about 50% of unbarred galaxies show a remarkable gas velocity gradient along the optical minor axis. This fraction rises to about 60% if we include unbarred galaxies with an irregular velocity profile along the minor axis. This phenomenon is observed all along the Hubble sequence of disk galaxies, and it is particularly frequent in early-type spirals. Since minor-axis velocity gradients are unexpected if the gas is moving onto circular orbits in a disk coplanar to the stellar one, we conclude that non-circular and off-plane gas motions are not rare in the inner regions of disk galaxies.Comment: 12 pages, 4 postscript figures. Accepted for publication in A&

A Review of Hot Deck Imputation for Survey Non-response

L'imputation hot deck est une méthode de gestion des données manquantes dans laquelle chaque valeur manquante est remplacée par une réponse observée à partir d'une unité“similaire.” Bien qu'elle soit largement utilisée en pratique, sa théorie n'est pas aussi développée que celle des autres méthodes d'imputation. Nous avons constaté qu'il n'existe aucun consensus quant à la meilleure faon d'appliquer les hot deck et obtenir des inférences à partir de la série de données complète. Ici, nous passons en revue les différentes formes de hot deck et les recherches existantes sur ses propriétés statistiques. Nous décrivons les applications du hot deck actuellement utilisées, y compris le hot deck du Bureau US du recensement pour la Current Population Survey (CPS). Nous proposons aussi des exemples nombreux de variations du hot deck à la troisième National Health and Nutrition Examination Survey (NHANES III). Certains domaines possibles de recherches futures sont mises en évidence.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78729/1/j.1751-5823.2010.00103.x.pd

The rotation curves shapes of late-type dwarf galaxies

We present rotation curves derived for a sample of 62 late-type dwarf galaxies that have been observed as part of the Westerbork HI Survey of Spiral and Irregular Galaxies (WHISP) project. The rotation curves were derived by interactively fitting model data cubes to the observed cubes, taking rotation curve shape, HI distribution, inclination, and the size of the beam into account. This makes it possible to correct for the effects of beam smearing. The dwarf galaxies in our sample have rotation-curve shapes that are similar to those of late-type spiral galaxies, in the sense that their rotation curves, when expressed in units of disk scale lengths, rise as steeply in the inner parts and start to flatten at two disk scale lengths. None of the galaxies in our sample have solid-body rotation curves that extend beyond three scale lengths. The logarithmic outer rotation curve slopes are similar between late-type dwarf and spiral galaxies. Thus, whether the flat part of the rotation curve is reached seems to depend more on the extent of the rotation curve than on its amplitude. We also find that the outer rotation curve shape does not strongly depend on luminosity, at least for galaxies fainter than M_R~-19. We find that in spiral galaxies and in the central regions of late-type dwarf galaxies, the shape of the central distribution of light and the inner rise of the rotation curve are related. This implies that galaxies with stronger central concentrations of light also have higher central mass densities, and it suggests that the luminous mass dominates the gravitational potential in the central regions, even in low surface brightness dwarf galaxies.Comment: 22 pages, 2009 A&A 493, 87

A review for clinical outcomes research: hypothesis generation, data strategy, and hypothesis-driven statistical analysis

In recent years, more and more large, population-level databases have become available for clinical research. The size and complexity of these databases often present a methodological challenge for investigators. We propose that a “protocol” may facilitate the research process using these databases. In addition, much like the structured History and Physical (H&P) helps the audience appreciate the details of a patient case more systematically, a formal outcomes research protocol can also help in the systematic evaluation of an outcomes research manuscript