A Milstein scheme for SPDEs

This article studies an infinite dimensional analog of Milstein's scheme for finite dimensional stochastic ordinary differential equations (SODEs). The Milstein scheme is known to be impressively efficient for SODEs which fulfill a certain commutativity type condition. This article introduces the infinite dimensional analog of this commutativity type condition and observes that a certain class of semilinear stochastic partial differential equation (SPDEs) with multiplicative trace class noise naturally fulfills the resulting infinite dimensional commutativity condition. In particular, a suitable infinite dimensional analog of Milstein's algorithm can be simulated efficiently for such SPDEs and requires less computational operations and random variables than previously considered algorithms for simulating such SPDEs. The analysis is supported by numerical results for a stochastic heat equation and stochastic reaction diffusion equations showing signifficant computational savings.Comment: The article is slightly revised and shortened. In particular, some numerical simulations are remove

Parsec-Scale Bipolar X-ray Shocks Produced by Powerful Jets from the Neutron Star Circinus X-1

We report the discovery of multi-scale X-ray jets from the accreting neutron star X-ray binary, Circinus X-1. The bipolar outflows show wide opening angles and are spatially coincident with the radio jets seen in new high-resolution radio images of the region. The morphology of the emission regions suggests that the jets from Circinus X-1 are running into a terminal shock with the interstellar medium, as is seen in powerful radio galaxies. This and other observations indicate that the jets have a wide opening angle, suggesting that the jets are either not very well collimated or precessing. We interpret the spectra from the shocks as cooled synchrotron emission and derive a cooling age of approximately 1600 yr. This allows us to constrain the jet power to be between 3e35 erg/s and 2e37 erg/s, making this one of a few microquasars with a direct measurement of its jet power and the only known microquasar that exhibits stationary large-scale X-ray emission.Comment: 5 pages, 4 figures, to be published in the Astrophysical Journal Letter

Muscularity and attractiveness as predictors of human egalitarianism

This is the post-print version of the final paper published in Personality and Individual Differences. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.In ancestral human environments, muscularity and height (in males) and physical attractiveness (in both sexes) would theoretically have correlated positively with one’s social status, and thus with one’s ability to benefit from social inequality. We therefore hypothesized that individuals who are more characterized by these traits would be less egalitarian (i.e., less likely to believe that resources should be distributed equally in social groups). We used a white-light 3D body scanner to extract anthropometric measurements from 118 participants, and our four egalitarianism measures included social dominance orientation and social value orientation. We found that as hypothesized, muscularity and waist–chest ratio in males, and self-perceived attractiveness in both sexes, tended to associate significantly in the predicted directions with the four egalitarianism measures; most of these correlations were of medium size. Neither height, nor two anthropometrically-assessed attractiveness measures (volume height index and waist–hip ratio), associated significantly with any egalitarianism measure in either sex. Egalitarianism has crucial social repercussions (e.g., taxes, welfare and civil rights), and results from the current study shed light on its origins

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291

We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are ~40% of the bulge sources and ~25% of the ring sources showing >3\sigma long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (~75%) and ring (~65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity AGN with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of ~1.5\times10^{37} and ~2.2\times10^{37} erg/s for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291, which suggests that the observed combined XLF is dominated by an old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative overdensity of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.Comment: 15 pages, 11 figures. Accepted for publication in Ap

Darwin’s wind hypothesis: does it work for plant dispersal in fragmented habitats?

Using the wind-dispersed plant Mycelis muralis, we examined how landscape fragmentation affects variation in seed traits contributing to dispersal. Inverse terminal velocity (Vt−1) of field-collected achenes was used as a proxy for individual seed dispersal ability. We related this measure to different metrics of landscape connectivity, at two spatial scales: in a detailed analysis of eight landscapes in Spain and along a latitudinal gradient using 29 landscapes across three European regions. In the highly patchy Spanish landscapes, seed Vt−1 increased significantly with increasing connectivity. A common garden experiment suggested that differences in Vt−1 may be in part genetically based. The Vt−1 was also found to increase with landscape occupancy, a coarser measure of connectivity, on a much broader (European) scale. Finally, Vt−1 was found to increase along a south–north latitudinal gradient. Our results for M. muralis are consistent with ‘Darwin’s wind dispersal hypothesis’ that high cost of dispersal may select for lower dispersal ability in fragmented landscapes, as well as with the ‘leading edge hypothesis’ that most recently colonized populations harbour more dispersive phenotypes.

A Longitudinal Analysis of Moving Desires, Expectations and Actual Moving Behaviour

Residential mobility theory proposes that moves are often preceded by the expression of moving desires and expectations. Much research has investigated how individuals form these premove thoughts, with a largely separate literature examining actual mobility. Although a growing number of studies link premove thoughts to subsequent moving behaviour, these often do not distinguish explicitly between different types and combinations of premove thoughts. Using 1998–2006 British Household Panel Survey data, this study investigates whether moving desires and expectations are empirically distinct premove thoughts. Using multinomial regression models we demonstrate that moving desires and expectations have different meanings, and are often held in combination: the factors associated with expecting to move differ depending upon whether the move is also desired (and vice versa). Next, using panel logistic regression models, we show that different desire–expectation combinations have different effects on the probability of subsequent moving behaviour. The study identified two important groups generally overlooked in the literature: those who expect undesired moves and those who desire to move without expecting this to happen.The definitive, peer reviewed and edited version of this article is published in Environment and Planning A, 2011, 43(11), pp. 2742-2760, doi:10.1068/a44105

Costly third-party interventions: The role of incidental anger and attention focus in punishment of the perpetrator and compensation of the victim

publisher: Elsevier articletitle: Costly third-party interventions: The role of incidental anger and attention focus in punishment of the perpetrator and compensation of the victim journaltitle: Journal of Experimental Social Psychology articlelink: http://dx.doi.org/10.1016/j.jesp.2016.04.004 content_type: article copyright: © 2016 Elsevier Inc. All rights reserved

Pathogenesis of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of disease ranging from hepatocellular steatosis through steatohepatitis to fibrosis and irreversible cirrhosis. The prevalence of NAFLD has risen rapidly in parallel with the dramatic rise in obesity and diabetes, and is rapidly becoming the most common cause of liver disease in Western countries. Indeed, NAFLD is now recognized to be the aetiology in many cases previously labelled as cryptogenic cirrhosis