Astrophysical properties of binary star clusters in the Small Magellanic Cloud

To study the evolution of binary star clusters we have imaged 7 systems in the Small Magellanic Cloud with SOAR 4-m telescope using B and V filters. The sample contains pairs with well-separated components (d < 30 pc) as well as systems that apparently merged, as evidenced by their unusual structures. By employing isochrone fittings to their CMDs we have determined reddening, age and metallicity and by fitting King models to their radial stellar density profile we have estimated core radius. Disturbances of the density profile are interpreted as an evidence of interaction. Circunstances as distances between components and their age difference are addressed in terms of the timescales involved to access the physical connection of the system. In two cases the age difference is above 50 Myr, which suggests chance alignment, capture or sequential star formation.Comment: 4 pages, 1 figure. To appear in online version of Proc. IAU Symp. 266 (Star clusters), eds. R. de Grijs and J. Lepin

Ground state magnetic dipole moment of 35K

The ground state magnetic moment of 35K has been measured using the technique of nuclear magnetic resonance on beta-emitting nuclei. The short-lived 35K nuclei were produced following the reaction of a 36Ar primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the 35K nuclei produced at 2 degrees relative to the normal primary beam axis was confirmed. Together with the mirror nucleus 35S, the measurement represents the heaviest T = 3/2 mirror pair for which the spin expectation value has been obtained. A linear behavior of gp vs. gn has been demonstrated for the T = 3/2 known mirror moments and the slope and intercept are consistent with the previous analysis of T = 1/2 mirror pairs.Comment: 14 pages, 5 figure

A double-label study of efferent projections from the Edinger-Westphal nucleus in goldfish and kelp bass

The Edinger-Westphal nucleus in goldfish was identified by retrograde labeling from the ciliary ganglion. In the same animals a few neurons near this nucleus (perinuclear Edinger-Westphal neurons) were labeled by a different retrograde tracer injected into the cerebellum. No double-labeled cells were found. Similar results were obtained in kelp bass, except that in this species no cerebellar-projecting perinuclear neurons were observed. Cerebellar-projecting Edinger-Westphal neurons have previously been described in some mammals, but not in other vertebrates. Therefore the homology of cerebellar-projecting cells of the Edinger-Westphal region in mammals and teleost fishes is doubtful

Stability and longevity in the publication careers of U.S. doctorate recipients

Since the 1950s, the number of doctorate recipients has risen dramatically in the United States. In this paper, we investigate whether the longevity of doctorate recipients’ publication careers has changed. This is achieved by matching 1951–2010 doctorate recipients with rare names in astrophysics, chemistry, economics, genetics and psychology in the dissertation database ProQuest to their publications in the publication database Web of Science. Our study shows that pre-PhD publication careers have changed: the median year of first publication has shifted from after the PhD to several years before PhD in most of the studied fields. In contrast, post-PhD publication career spans have not changed much in most fields. The share of doctorate recipients who have published for more than twenty years has remained stable over time; the shares of doctorate recipients publishing for shorter periods also remained almost unchanged. Thus, though there have been changes in pre-PhD publication careers, post-PhD career spans remained quite stable

Field-induced metal-insulator transition and switching phenomenon in correlated insulators

We study the nonequilibrium switching phenomenon associated with the metal-insulator transition under electric field E in correlated insulator by a gauge-covariant Keldysh formalism. Due to the feedback effect of the resistive current I, this occurs as a first-order transition with a hysteresis of I-V characteristics having a lower threshold electric field (\sim 10^4 Vcm^{-1}) much weaker than that for the Zener breakdown. It is also found that the localized mid-gap states introduced by impurities and defects act as hot spots across which the resonant tunneling occurs selectively, which leads to the conductive filamentary paths and reduces the energy cost of the switching function.Comment: 5 pages, 3 figures. A study on the metal-insulator transition in correlated insulators was adde

Characterization of anisotropic nano-particles by using depolarized dynamic light scattering in the near field

Light scattering techniques are widely used in many fields of condensed and sof t matter physics. Usually these methods are based on the study of the scattered light in the far field. Recently, a new family of near field detection schemes has been developed, mainly for the study of small angle light scattering. These techniques are based on the detection of the light intensity near to the sample, where light scattered at different directions overlaps but can be distinguished by Fourier transform analysis. Here we report for the first time data obtained with a dynamic near field scattering instrument, measuring both polarized and depolarized scattered light. Advantages of this procedure over the traditional far field detection include the immunity to stray light problems and the possibility to obtain a large number of statistical samples for many different wave vectors in a single instantaneous measurement. By using the proposed technique we have measured the translational and rotational diffusion coefficients of rod-like colloidal particles. The obtained data are in very good agreement with the data acquired with a traditional light scattering apparatus.Comment: Published in Optics Express. This version has changes in bibliograph

Comments on Supergravity Description of S-branes

This is a note on the coupled supergravity-tachyon matter system, which has been earlier proposed as a candidate for the effective space-time description of S-branes. In particular, we study an ansatz with the maximal ISO(p+1)xSO(8-p,1) symmetry, for general brane dimensionality p and homogeneous brane distribution in transverse space \rho_\perp. A simple application of singularity theorems shows that (for p \le 7) the most general solution with these symmetries is always singular. (This invalidates a recent claim in the literature.) We include a few general comments about the possibility of describing the decay of unstable D-branes in purely gravitational terms.Comment: 19 pages, refs adde

Rolling of Modulated Tachyon with Gauge Flux and Emergent Fundamental String

We investigate real-time tachyon dynamics of unstable D-brane carrying fundamental string charge. We construct the boundary state relevant for rolling of modulated tachyon with gauge fields excited on the world-volume, and study spatial distribution of the fundamental string charge and current as the D-brane decays. We find that, in contrast to homogeneous tachyon rolling, spatial modulation of the tachyon field triggers density wave of strings when electric field is turned on, and of string anti-string pairs when magnetic field is turned on. We show that the energy density and the fundamental string charge density are locked together, and evolve into a localized delta-function array (instead of evolving into a string fluid) until a critical time set by initial condition of rolling tachyon. When the gauge fields approach the critical limit, the fundamental strings produced become BPS-like. We also study the dynamics via effective field theory, and find agreement.Comment: 28 pages, Latex, 7 .eps figures v2: stability discussion update

Task specialization across research careers

Research careers are typically envisioned as a single path in which a scientist starts as a member of a team working under the guidance of one or more experienced scientists and, if they are successful, ends with the individual leading their own research group and training future generations of scientists. Here we study the author contribution statements of published research papers in order to explore possible biases and disparities in career trajectories in science. We used Bayesian networks to train a prediction model based on a dataset of 70,694 publications from PLoS journals, which included 347,136 distinct authors and their associated contribution statements. This model was used to predict the contributions of 222,925 authors in 6,236,239 publications, and to apply a robust archetypal analysis to profile scientists across four career stages: junior, early-career, mid-career and late-career. All three of the archetypes we found - leader, specialized, and supporting - were encountered for early-career and mid-career researchers. Junior researchers displayed only two archetypes (specialized, and supporting), as did late-career researchers (leader and supporting). Scientists assigned to the leader and specialized archetypes tended to have longer careers than those assigned to the supporting archetype. We also observed consistent gender bias at all stages: the majority of male scientists belonged to the leader archetype, while the larger proportion of women belonged to the specialized archetype, especially for early-career and mid-career researchers

Whole-genome sequencing of Theileria parva strains provides insight into parasite migration and diversification in the african continent

The disease caused by the apicomplexan protozoan parasite Theileria parva, known as East Coast fever or Corridor disease, is one of the most serious cattle diseases in Eastern, Central, and Southern Africa. We performed whole-genome sequencing of nine T. parva strains, including one of the vaccine strains (Kiambu 5), field isolates from Zambia, Uganda, Tanzania, or Rwanda, and two buffalo-derived strains. Comparison with the reference Muguga genome sequence revealed 34 814–121 545 single nucleotide polymorphisms (SNPs) that were more abundant in buffalo-derived strains. High-resolution phylogenetic trees were constructed with selected informative SNPs that allowed the investigation of possible complex recombination events among ancestors of the extant strains. We further analysed the dN/dS ratio (non-synonymous substitutions per non-synonymous site divided by synonymous substitutions per synonymous site) for 4011 coding genes to estimate potential selective pressure. Genes under possible positive selection were identified that may, in turn, assist in the identification of immunogenic proteins or vaccine candidates. This study elucidated the phylogeny of T. parva strains based on genome-wide SNPs analysis with prediction of possible past recombination events, providing insight into the migration, diversification, and evolution of this parasite species in the African continent