New Techniques for Relating Dynamically Close Galaxy Pairs to Merger and Accretion Rates : Application to the SSRS2 Redshift Survey

We introduce two new pair statistics, which relate close galaxy pairs to the merger and accretion rates. We demonstrate the importance of correcting these (and other) pair statistics for selection effects related to sample depth and completeness. In particular, we highlight the severe bias that can result from the use of a flux-limited survey. The first statistic, denoted N_c, gives the number of companions per galaxy, within a specified range in absolute magnitude. N_c is directly related to the galaxy merger rate. The second statistic, called L_c, gives the total luminosity in companions, per galaxy. This quantity can be used to investigate the mass accretion rate. Both N_c and L_c are related to the galaxy correlation function and luminosity function in a straightforward manner. We outline techniques which account for various selection effects, and demonstrate the success of this approach using Monte Carlo simulations. If one assumes that clustering is independent of luminosity (which is appropriate for reasonable ranges in luminosity), then these statistics may be applied to flux-limited surveys. These techniques are applied to a sample of 5426 galaxies in the SSRS2 redshift survey. Using close dynamical pairs, we find N_c(-21<M_B<-18) = 0.0226+/-0.0052 and L_c(-21<M_B<-18) = 0.0216+/-0.0055 10^{10} h^2 L_sun at z=0.015. These are the first secure estimates of low-z close pair statistics. If N_c remains fixed with redshift, simple assumptions imply that ~ 6.6% of present day galaxies with -21<M_B<-18 have undergone mergers since z=1. When applied to redshift surveys of more distant galaxies, these techniques will yield the first robust estimates of evolution in the galaxy merger and accretion rates. [Abridged]Comment: 26 pages (including 10 postscript figures) plus 3 gif figures. Accepted for publication in ApJ. Paper (including full resolution images) also available at http://www.astro.utoronto.ca/~patton/ssrs2, along with associated pair classification experiment (clickable version of Figure 5

Spin Wave Excitation in Magnetic Insulator Thin Films by Spin-Transfer Torque

We describe excitation of dipole-exchange spin waves in insulating magnetic thin films by spin current injection at the surface of the film. An easy-axis magnetic surface anisotropy can induce a non-chiral surface spin wave mode with penetration depth inversely proportional to the strength of the surface anisotropy, which strongly reduces the critical current and enhances the excitation power. The importance of the interface spin wave modes on the excitation spectrum is reduced by spin pumping, which depends on the quality of the interface as expressed by the spin mixing conductance.Comment: 19 pages, 10 figure

Pain and learning in primary school: a population-based study.

Despite the frequency of pain among children, little is known about its effects on learning and school outcomes. The objective of this study was to quantify the association of pain and academic achievement while taking into account the presence of co-occurring emotional symptoms. A population-based stratified random sample of 1239 students aged 8 to 9 years from primary schools in Melbourne, Australia, was recruited for the Childhood to Adolescence Transition Study. Children indicated sites of pain that had lasted for a day or longer in the past month using a pain manikin. Depressive- and anxiety-related symptoms were assessed using child-reported items. National assessment results for reading and numeracy were used to measure academic achievement. Sixty-five percent of children reported pain in at least 1 body site and 16% reported chronic pain. Increasing number of pain sites was associated with poorer reading scores in a dose-response fashion (β = -3.1; 95% confidence interval -4.9 to -1.3; P < 0.001). The association was only partly attenuated when adjusting for emotional symptoms (β = -2.6; 95% confidence interval -4.5 to -0.8; P < 0.001) and was not moderated by emotional symptoms. Children with chronic pain were a year behind their peers in both reading and numeracy. Among primary school students, pain was associated with lower reading scores even after adjusting for the presence of emotional symptoms. Although population-based longitudinal studies will be required to ascertain consistency and possible causality, grounds exist for considering pain and emotional symptoms in the assessment of children with reading difficulties

High-order 3D Voronoi tessellation for identifying Isolated galaxies, Pairs and Triplets

Geometric method based on the high-order 3D Voronoi tessellation is proposed for identifying the single galaxies, pairs and triplets. This approach allows to select small galaxy groups and isolated galaxies in different environment and find the isolated systems. The volume-limited sample of galaxies from the SDSS DR5 spectroscopic survey was used. We conclude that in such small groups as pairs and triplets the segregation by luminosity is clearly observed: galaxies in the isolated pairs and triplets are on average two times more luminous than isolated galaxies. We consider the dark matter content in different systems. The median values of mass-to-luminosity ratio are 12 M_sol/L_sol for the isolated pairs and 44 M_sol/L_sol for the isolated triplets; 7 (8) M_sol/L_sol for the most compact pairs (triplets). We found also that systems in the denser environment have greater rms velocity and mass-to-luminosity ratio.Comment: 11 pages, 7 figures, Accepted 2008 October 25 in MNRA

Definition of species of pouched four-eyed opossums (Didelphidae, Philander)

We hypothesize phyletic relationships among taxa of the didelphid marsupial genus Philander, based on sequences of the mitochondrial cytochrome b gene. Data are available for six taxa recognized at either the specific or subspecific levels; P. opossum opossum Linneaus (eastern and northeastern Amazonia), P. opossum canus Osgood (western Amazonia), P. opossum fuscogriseus J. A. Allen (southeastern Central America), P. opossum frenata Olfers (southeastern Brazil), P. andersoni andersoni Osgood (northwestern Amazonia), and P. andersoni mcilhennyi Gardner and Patton (west-central Amazonia). Haplotype divergence is minimal to non-existent (<1% on average) between individuals within and among localities for each taxon. The taxon inhabiting the Atlantic forest of coastal Brazil (P. o. frenata) is highly divergent from all others, averaging nearly 14% in sequence divergence. Maximal divergence among haplotypes representative of the other taxa examined is <8%. The combination of phylogenetic relationships and local sympatry suggests a greater degree of species diversity for the genus than the two species P. opossum and P. andersoni. We recognize the Brazilian coastal P. frenata, as well as both P. andersoni and P. mcilhennyi, as valid species in addition to P. opossum. It is possible P. opossum is a composite, and that further studies will accord species status to the Middle American, western Amazonian, and eastern Amazonian-Guianan gray four-eyed opossums

Environmental Dependence of Galaxy Merger Rate in {\Lambda}CDM Universe

We make use of four galaxy catalogs based on four different semi-analytical models (SAMs) implemented in the Millennium simulation to study the environmental effects and the model dependence of galaxy merger rate. We begin the analyses by finding that galaxy merger rate in the SAMs has mild redshift evolution, consistent with results of previous works. To study the environmental dependence of galaxy merger rate, we adopt two estimators, the local overdensity (1+{\delta}n) defined as the surface density from the nth-nearest-neighbor (n = 6 is chosen in this study) and the host halo mass Mh. We find that galaxy merger rate Fmg shows strong dependence on the local overdensity (1+{\delta}n) and the dependence is similar at all redshifts. For the overdensity estimator, the merger rate Fmg is found about twenty times larger in the densest regions than in under-dense ones in two of the four models while it is roughly four times higher in the other two. In other words, the discrepancies of the merger rate difference between two extremes can differ by a factor of ~ five depending on the SAMs adopted. On the other hand for the halo mass estimator, Fmg does not monotonically increase with the host halo mass Mh, but peaks in the $M_h$ range between 10^12 and 10^13 h-1 M{\Theta}, which corresponds to group environments. High merger rate in high local density regions corresponds primarily to the high merge rate in group environments......Comment: 15 pages, 11 figures, submitted to ApJ; referee comments are incorporate

Learning health ‘safety’ within non-technical skills interprofessional simulation education: a qualitative study

Background: Healthcare increasingly recognises and focusses on the phenomena of ‘safe practice’ and ‘patient safety.’ Success with non-technical skills (NTS) training in other industries has led to widespread transposition to healthcare education, with communication and teamwork skills central to NTS frameworks. Objective: This study set out to identify how the context of interprofessional simulation learning influences NTS acquisition and development of ‘safety’ amongst learners. Methods: Participants receiving a non-technical skills (NTS) safety focussed training package were invited to take part in a focus group interview which set out to explore communication, teamwork, and the phenomenon of safety in the context of the learning experiences they had within the training programme. The analysis was aligned with a constructivist paradigm and took an interactive methodological approach. The analysis proceeded through three stages, consisting of open, axial, and selective coding, with constant comparisons taking place throughout each phase. Each stage provided categories that could be used to explore the themes of the data. Additionally, to ensure thematic saturation, transcripts of observed simulated learning encounters were then analysed. Results: Six themes were established at the axial coding level, i.e., analytical skills, personal behaviours, communication, teamwork, context, and pedagogy. Underlying these themes, two principal concepts emerged, namely: intergroup contact anxiety – as both a result of and determinant of communication – and teamwork, both of which must be considered in relation to context. These concepts have subsequently been used to propose a framework for NTS learning. Conclusions: This study highlights the role of intergroup contact anxiety and teamwork as factors in NTS behaviour and its dissipation through interprofessional simulation learning. Therefore, this should be a key consideration in NTS education. Future research is needed to consider the role of the affective non-technical attributes of intergroup contact anxiety and teamwork as focuses for education and determinants of safe behaviour

Reducing model bias in a deep learning classifier using domain adversarial neural networks in the MINERvA experiment

We present a simulation-based study using deep convolutional neural networks (DCNNs) to identify neutrino interaction vertices in the MINERvA passive targets region, and illustrate the application of domain adversarial neural networks (DANNs) in this context. DANNs are designed to be trained in one domain (simulated data) but tested in a second domain (physics data) and utilize unlabeled data from the second domain so that during training only features which are unable to discriminate between the domains are promoted. MINERvA is a neutrino-nucleus scattering experiment using the NuMI beamline at Fermilab. $A$-dependent cross sections are an important part of the physics program, and these measurements require vertex finding in complicated events. To illustrate the impact of the DANN we used a modified set of simulation in place of physics data during the training of the DANN and then used the label of the modified simulation during the evaluation of the DANN. We find that deep learning based methods offer significant advantages over our prior track-based reconstruction for the task of vertex finding, and that DANNs are able to improve the performance of deep networks by leveraging available unlabeled data and by mitigating network performance degradation rooted in biases in the physics models used for training.Comment: 41 page

Internal kinematics of spiral galaxies in distant clusters IV. Gas kinematics of spiral galaxies in intermediate redshift clusters and in the field

(Abridged) We trace the interaction processes of galaxies at intermediate redshift by measuring the irregularity of their ionized gas kinematics, and investigate these irregularities as a function of the environment (cluster versus field) and of morphological type (spiral versus irregular). Our sample consists of 92 distant galaxies. 16 cluster (z~0.3 and z~0.5) and 29 field galaxies (mean z=0.44) of these have velocity fields with sufficient signal to be analyzed. We find that the fraction of galaxies that have irregular gas kinematics is remarkably similar in galaxy clusters and in the field at intermediate redshifts. The distribution of the field and cluster galaxies in (ir)regularity parameters space is also similar. On the other hand galaxies with small central concentration of light, that we see in the field sample, are absent in the cluster sample. We find that field galaxies at intermediate redshifts have more irregular velocity fields as well as more clumpy and less centrally concentrated light distributions than their local counterparts. Comparison with a SINS sample of 11 z ~ 2 galaxies shows that these distant galaxies have more irregular gas kinematics than our intermediate redshift cluster and field sample. We do not find a dependence of the irregularities in gas kinematics on morphological type. We find that two different indicators of star formation correlate with irregularity in the gas kinematics. More irregular gas kinematics, also more clumpy and less centrally concentrated light distributions of spiral field galaxies at intermediate redshifts in comparison to their local counterparts indicate that these galaxies are probably still in the process of building their disks via mechanisms such as accretion and mergers. On the other hand, they have less irregular gas kinematics compared to galaxies at z ~ 2.Comment: Accepted for publication in A&A, high resolution version available at http://www.astro.rug.nl/~kutdemir/13262/13262_hr.p