National characteristics and variation in Arabic handwriting

From each of four Arabic countries; Morocco, Tunisia, Jordan and Oman, 150 participants produced handwriting samples which were examined to assess whether national characteristics were discernible. Ten characters, which have different configurations depending upon their position in the word, along with one short word, were classified into distinguishable forms, and these forms recorded for each handwriting sample. Tests of independence showed that character forms used were not independent of country (p < 0.001) for all but one character-position (this was dropped from subsequent analyses). A correspondence analysis ordination plot and analysis of similarity (R = 0.326, p = 0.0002) showed that whole samples were discernibly grouped by country, and a tree analysis produced a classification which was 71% accurate for the original data and 83% accurate for 80 new handwriting samples that underwent ‘blind’ classification. When the countries were combined into two regions, North Africa and Middle East, the grouping was more marked. Thus, there appears to be some scope for narrowing down the nationality, and particularly the wider geographical region of an author based upon the character forms they use in Arabic handwriting

Surviving infant mortality in the hierarchical merging scenario

We examine the effects of gas expulsion on initially sub-structured and out-of-equilibrium star clusters. We perform $N$-body simulations of the evolution of star clusters in a static background potential before removing that potential to model gas expulsion. We find that the initial star formation efficiency is not a good measure of the survivability of star clusters. This is because the stellar distribution can change significantly, causing a large change in the relative importance of the stellar and gas potentials. We find that the initial stellar distribution and velocity dispersion are far more important parameters than the initial star formation efficiency, and that clusters with very low star formation efficiencies can survive gas expulsion. We suggest that it is variations in cluster initial conditions rather than in their star formation efficiencies that cause some clusters to be destroyed while a few survive.Comment: 9 pages, 10 figures, 1 tabl

On the formation of trapezium-like systems

We investigate the formation and evolution of high-order massive star multiples similar to the Trapezium in the Orion Nebula Cluster. We perform ensembles of N-body simulations of the evolution of N=1000 Orion-like clusters with initial conditions ranging from cool and clumpy to relatively smooth and relaxed. We find that trapezium-like systems are frequently formed in the first 2 Myr in initially cool and clumpy clusters and can survive for significant amounts of time in such clusters. We also find that these systems are highly dynamical entities, constantly interacting with the surrounding cluster, changing their appearance and membership regularly. The eventual decay of trapezium-like systems can even destroy the host cluster. We argue that the current state of any trapezium-like system is transient and care should be taken when analysing and drawing conclusions from a single snapshot in the life of a highly dynamic object.Comment: Accepted for publication in MNRAS. Supplementary material can be found at ftp://hydra.shef.ac.uk/pub/spg/TRAP_SUPLIMENTARY.pd

Self-reported health and cardiovascular reactions to psychological stress in a large community sample: Cross-sectional and prospective associations

Exaggerated cardiovascular reactions to acute psychological stress have been implicated in a number of adverse health outcomes. This study examined, in a large community sample, the cross-sectional and prospective associations between reactivity and self-reported health. Blood pressure and heart rate were measured at rest and in response to an arithmetic stress task. Self-reported health was assessed concurrently and five years later. In cross-sectional analyses, those with excellent/good self-reported health exhibited larger cardiovascular reactions than those with fair/poor subjective health. In prospective analyses, participants who had larger cardiovascular reactions to stress were more likely to report excellent/good health five years later, taking into account their reported health status at the earlier assessment. The findings suggest that greater cardiovascular reactivity may not always be associated with negative health outcomes

Dynamical Evolution of Young Embedded Clusters: A Parameter Space Survey

This paper investigates the dynamical evolution of embedded stellar clusters from the protocluster stage, through the embedded star-forming phase, and out to ages of 10 Myr -- after the gas has been removed from the cluster. The relevant dynamical properties of young stellar clusters are explored over a wide range of possible star formation environments using N-body simulations. Many realizations of equivalent initial conditions are used to produce robust statistical descriptions of cluster evolution including the cluster bound fraction, radial probability distributions, as well as the distributions of close encounter distances and velocities. These cluster properties are presented as a function of parameters describing the initial configuration of the cluster, including the initial cluster membership N, initial stellar velocities, cluster radii, star formation efficiency, embedding gas dispersal time, and the degree of primordial mass segregation. The results of this parameter space survey, which includes about 25,000 simulations, provide a statistical description of cluster evolution as a function of the initial conditions. We also present a compilation of the FUV radiation fields provided by these same cluster environments. The output distributions from this study can be combined with other calculations, such as disk photoevaporation models and planetary scattering cross sections, to ascertain the effects of the cluster environment on the processes involved in planet formation.Comment: 65 pages including 20 figures, accepted to ApJ Supplemen

A New Independent Limit on the Cosmological Constant/Dark Energy from the Relativistic Bending of Light by Galaxies and Clusters of Galaxies

We derive new limits on the value of the cosmological constant, $\Lambda$, based on the Einstein bending of light by systems where the lens is a distant galaxy or a cluster of galaxies. We use an amended lens equation in which the contribution of $\Lambda$ to the Einstein deflection angle is taken into account and use observations of Einstein radii around several lens systems. We use in our calculations a Schwarzschild-de Sitter vacuole exactly matched into a Friedmann-Robertson-Walker background and show that a $\Lambda$-contribution term appears in the deflection angle within the lens equation. We find that the contribution of the $\Lambda$-term to the bending angle is larger than the second-order term for many lens systems. Using these observations of bending angles, we derive new limits on the value of $\Lambda$. These limits constitute the best observational upper bound on $\Lambda$ after cosmological constraints and are only two orders of magnitude away from the value determined by those cosmological constraints.Comment: 5 pages, 1 figure, matches version published in MNRA