Shifts in hexapod diversification and what Haldane could have said

Data on species richness and taxon age are assembled for the extant hexapod orders (insects and their six-legged relatives). Coupled with estimates of phylogenetic relatedness, and simple statistical null models, these data are used to locate where, on the hexapod tree, significant changes in the rate of cladogenesis (speciation-minus-extinction rate) have occurred. Significant differences are found between many successive pairs of sister taxa near the base of the hexapod tree, all of which are attributable to a shift in diversification rate after the origin of the Neoptera (insects with wing flexion) and before the origin of the Holometabola (insects with complete metamorphosis). No other shifts are identifiable amongst supraordinal taxa. Whilst the Coleoptera have probably diversified faster than either of their putative sister lineages, they do not stand out relative to other closely related clades. These results suggest that any Creator had a fondness for a much more inclusive clade than the Coleoptera, definitely as large as the Eumetabola (Holometabola plus bugs and their relatives), and possibly as large as the entire Neoptera. Simultaneous, hence probable causative events are discussed, of which the origin of wing flexion has been the focus of much attention

New Cosmological Structures on Medium Angular Scales Detected with the Tenerife Experiments

We present observations at 10 and 15 GHz taken with the Tenerife experiments in a band of the sky at Dec.=+35 degrees. These experiments are sensitive to multipoles in the range l=10-30. The sensitivity per beam is 56 and 20 microK for the 10 and the 15 GHz data, respectively. After subtraction of the prediction of known radio-sources, the analysis of the data at 15 GHz at high Galactic latitude shows the presence of a signal with amplitude Delta Trms ~ 32 microK. In the case of a Harrison-Zeldovich spectrum for the primordial fluctuations, a likelihood analysis shows that this signal corresponds to a quadrupole amplitude Q_rms-ps=20.1+7.1-5.4 microK, in agreement with our previous results at Dec.+=40 degrees and with the results of the COBE DMR. There is clear evidence for the presence of individual features in the RA range 190 degrees to 250 degrees with a peak to peak amplitude of ~110 microK. A preliminary comparison between our results and COBE DMR predictions for the Tenerife experiments clearly indicates the presence of individual features common to both. The constancy in amplitude over such a large range in frequency (10-90 GHz) is strongly indicative of an intrinsic cosmological origin for these structures.Comment: ApJ Letters accepted, 13 pages Latex (uses AASTEX) and 4 encapsulated postscript figures

The effect of stellar-mass black holes on the structural evolution of massive star clusters

We present the results of realistic N-body modelling of massive star clusters in the Magellanic Clouds, aimed at investigating a dynamical origin for the radius-age trend observed in these systems. We find that stellar-mass black holes, formed in the supernova explosions of the most massive cluster stars, can constitute a dynamically important population. If a significant number of black holes are retained (here we assume complete retention), these objects rapidly form a dense core where interactions are common, resulting in the scattering of black holes into the cluster halo, and the ejection of black holes from the cluster. These two processes heat the stellar component, resulting in prolonged core expansion of a magnitude matching the observations. Significant core evolution is also observed in Magellanic Cloud clusters at early times. We find that this does not result from the action of black holes, but can be reproduced by the effects of mass-loss due to rapid stellar evolution in a primordially mass segregated cluster.Comment: Accepted for publication in MNRAS Letters; 2 figures, 1 tabl

Aerosol studies in mid-latitude coastal environments in Australia

The results of the evaluation of several inversion procedures that were used to select one which provides the most accurate atmospheric extinction profiles for small aerosol extinction coefficients (that often predominate in the maritime airmass) are presented. Height profiles of atmospheric extinction calculated by a two component atmospheric solution to the LIDAR equation will be compared with corresponding in-situ extinction profiles based on the size distribution profiles obtained in Western Australia. Values of the aerosol backscatter to extinction ratio obtained from multi-angle LIDAR measurements will be used in this solution

The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis

The results of the Tenerife Cosmic Microwave Background (CMB) experiments are presented. These observations cover 5000 and 6500 square degrees on the sky at 10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe plateau of the CMB power spectra. The sensitivity of the results are ~31 and \~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees FWHM). The data at 15 GHz show clear detection of structure at high Galactic latitude; the results at 10 GHz are compatible with these, but at lower significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic latitude, assuming a flat CMB band power spectra gives a signal Delta T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK. These values are highly stable against the Galactic cut chosen. Assuming a Harrison-Zeldovich spectrum for the primordial fluctuations, the above values imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap

Interference between postural control and mental task performance in patients with vestibular disorder and healthy controls

OBJECTIVES - To determine whether interference between postural control and mental task performance in patients with balance system impairment and healthy subjects is due to general capacity limitations, motor control interference, competition for spatial processing resources, or a combination of these.METHOD - Postural stability was assessed in 48 patients with vestibular disorder and 24 healthy controls while they were standing with eyes closed on (a) a stable and (b) a moving platform. Mental task performance was measured by accuracy and reaction time on mental tasks, comprising high and low load, spatial and non-spatial tasks. Interference between balancing and performing mental tasks was assessed by comparing baseline (single task) levels of sway and mental task performance with levels while concurrently balancing and carrying out mental tasks.RESULTS - As the balancing task increased in difficulty, reaction times on both low load mental tasks grew progressively longer and accuracy on both high load tasks declined in patients and controls. Postural sway was essentially unaffected by mental activity in patients and controls.CONCLUSIONS - It is unlikely that dual task interference between balancing and mental activity is due to competition for spatial processing resources, as levels of interference were similar in patients with vestibular disorder and healthy controls, and were also similar for spatial and non-spatial tasks. Moreover, the finding that accuracy declined on the high load tasks when balancing cannot be attributed to motor control interference, as no motor control processing is involved in maintaining accuracy of responses. Therefore, interference between mental activity and postural control can be attributed principally to general capacity limitations, and is hence proportional to the attentional demands of both tasks

Virtual patient design : exploring what works and why : a grounded theory study

Objectives: Virtual patients (VPs) are online representations of clinical cases used in medical education. Widely adopted, they are well placed to teach clinical reasoning skills. International technology standards mean VPs can be created, shared and repurposed between institutions. A systematic review has highlighted the lack of evidence to support which of the numerous VP designs may be effective, and why. We set out to research the influence of VP design on medical undergraduates. Methods: This is a grounded theory study into the influence of VP design on undergraduate medical students. Following a review of the literature and publicly available VP cases, we identified important design properties. We integrated them into two substantial VPs produced for this research. Using purposeful iterative sampling, 46 medical undergraduates were recruited to participate in six focus groups. Participants completed both VPs, an evaluation and a 1-hour focus group discussion. These were digitally recorded, transcribed and analysed using grounded theory, supported by computer-assisted analysis. Following open, axial and selective coding, we produced a theoretical model describing how students learn from VPs. Results: We identified a central core phenomenon designated ‘learning from the VP’. This had four categories: VP Construction; External Preconditions; Student–VP Interaction, and Consequences. From these, we constructed a three-layer model describing the interactions of students with VPs. The inner layer consists of the student's cognitive and behavioural preconditions prior to sitting a case. The middle layer considers the VP as an ‘encoded object’, an e-learning artefact and as a ‘constructed activity’, with associated pedagogic and organisational elements. The outer layer describes cognitive and behavioural change. Conclusions: This is the first grounded theory study to explore VP design. This original research has produced a model which enhances understanding of how and why the delivery and design of VPs influence learning. The model may be of practical use to authors, institutions and researchers

Thermal Relics in Modified Cosmologies: Bounds on Evolution Histories of the Early Universe and Cosmological Boosts for PAMELA

Alternative cosmologies, based on extensions of General Relativity, predict modified thermal histories in the Early Universe during the pre Big Bang Nucleosynthesis (BBN) era, epoch which is not directly constrained by cosmological observations. When the expansion rate is enhanced with respect to the standard case, thermal relics typically decouple with larger relic abundances. The correct value of the relic abundance is therefore obtained for larger annihilation cross--sections, as compared to standard cosmology. A direct consequence is that indirect detection rates are enhanced. Extending previous analyses of ours, we derive updated astrophysical bounds on the dark matter annihilation cross sections and use them to constrain alternative cosmologies in the pre--BBN era. We also determine the characteristics of these alternative cosmologies in order to provide the correct value of relic abundance for a thermal relic for the (large) annihilation cross--section required to explain the PAMELA results on the positron fraction, therefore providing a "cosmological boost" solution to the dark matter interpretation of the PAMELA data.Comment: 19 pages, 27 figures, matches published versio