bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave Induced Synergetic Electron Acceleration in Inhomogeneous Solar Plasmas
Authors: Leubner M. P.
Published: July 2016

Suprathermal electron populations are generated efficiently in uniform space plasmas by resonant Landau interaction with broadband Alfvén wave spectra. Based on a simulation of the particle acceleration in response to the wave energy input within the Fokker-Planck formalism, details of the time evolution of the velocity space distribution towards commonly observed solar wind power law spectra are discussed. Furthermore, it is shown that the diffusion properties and consequently the particle energization change significantly in astrophysical environments with magnetic field and density gradients, since synergetic effects become dominant. Electrons are accelerated resonantly out of the bulk of the distribution such that they interact again with a wave packet of higher phase velocity, leading to a multi-stage energization. Hence, a unique acceleration mechanism can be achieved without postulating pre-acceleration by ad hoc mechanisms. Depending on the density and magnetic field profile, significant enhancement of energetic particles as well as stagnation in a saturated stage of suprathermal, non-Maxwellian velocity space distributions is possible. The importance of synergetic acceleration in complex solar flare structures and for solar wind heating mechanisms is discussed in relation to spacecraft observations.
Improved Analysis of COMPTEL Solar Neutron Data, with Application to the 15 June 1991 Flare
Authors: Toner M. P. , Ryan J. M. , MacKinnon A. L. , Bhattacharya D. , Macpherson K. P. , McConnell M. L. , Rank G. , Thompson A M , O'Neill T.
Published: July 2016

Direct solar flare neutrons are a valuable diagnostic of high-energy ion acceleration in these events, and COMPTEL improves over all previous cosmic neutron detectors in its capacity for neutron energy measurement. Previous studies of COMPTEL neutron data have worked with an incomplete model of the instrumental response, applying energy-by-energy detection efficiencies. Here we employ statistical regularisation techniques with the full (Monte Carlo simulation derived) response matrix to produce improved estimates of neutron numbers and energy distribution. These techniques are applied to data from the well-observed 15 June 1991 flare. Our improved treatment of the instrumental response results in a reduction of 73% in total neutron numbers, compared with previously deduced values. Implications for the picture of primary ion acceleration in this flare are briefly discussed.
HST Observations of Heliospheric and Astrospheric Lyα Absorption Toward the α Cen System
Authors: Wood B. E. , Linsky J. L. , Valenti J. A.
Published: July 2016

We use HST observations of the nearest star system (the α Cen system) to search for Lyα absorption from both heliospheric material around the Sun and analogous astrospheric material around the stars which has been heated by the collision between the solar/stellar winds and the interstellar medium. For α Cen A and B, both heliospheric and astrospheric absorption are detected, whereas for α Cen's distant companion star Proxima Cen only heliospheric absorption is detected, suggesting that Proxima Cen's astrosphere must be smaller and its wind therefore weaker than that of α Cen. Based on observations of these stars taken many years apart, we find that neither the heliospheric absorption nor the astrospheric absorption detected toward α Cen AB varies significantly.
The Influence of Solar Activity and Cosmic Rays on Terrestrial Clouds and Global Warming
Authors: Pallé Bagó E. , Butler C. J.
Published: July 2016

We analyse the new ISCCP (International Satellite Cloud Climatology Project) D2 cloud data to ascertain whether or not a connection between cosmic ray flux and cloud cover exists. Our results indicate that only the low-level cloud follows solar activity over the full period, 1983-1994. Using several proxies for solar activity and the radiative forcing for the ISCCP cloud types, we estimate the possible impact that such a solar-terrestrial connection may have on climate. We conclude that, possibly excluding the most recent decades, much of the warming of the past century can be quantitatively accounted for by the direct and indirect effects of solar activity.
The Shapes of Dark Halos
Authors: Rix Hans-Walter
Published: July 2016

Galactic and extragalactic astronomers often mean different things by “halo” the former mean the spheroidal distribution of metal poor stars around the Milky Way (MW), the latter mean the massive, dark component providing the large dynamically inferred mass in and around galaxies. This review will focus on massive, dark halos. Despite the title of this conference, we cannot restrict our attention to the shape of the MW halo: very little would be to say. We must turn to cosmological simulations and to observations of external disk galaxies in the hope of deriving a representative picture.
The Axisymmetric Stability of the Milky Way
Authors: Sellwood J. A.
Published: July 2016

The problem of axisymmetric Jeans stability of a stellar disk was essentially completely solved in the classic paper by Toomre (1964). While his analysis was strictly local, the stability criterion it yielded has been found to be remarkably reliable in global studies; I review earlier results and give a further example in Sellwood (1995, hereafter S95). Toomre (1974) concluded that the MW is safely stable to axisymmetric Jeans modes.
Faint Surface Photometry of the Halo of M31
Authors: Pritchet Chris , van den Bergh Sidney
Published: July 2016

We have obtained counts of stars near the tip of the red giant branch of M31, and have used these counts to estimate the surface brightness of the halo of M31 down to a level of μV ∼ 30 mag arcsec–2 (R ∼ 20 kpc). The surface brightness along the minor axis of the M31 halo is well-represented by a single de Vaucouleurs law (0.2 ≃ R[kpc] ≃ 20). Alternatively, the outer halo of M31 can also be modelled by a power-law density distribution of the form ρ(R) ∞ R–5. This result suggests that the globular cluster component of the halo of M31 (for which ρ ∞R–3) is more extended than the stellar halo of this galaxy. At μv Ã 28 mag arcsec–2 (R Ã 10 kpc), the axial ratio of the halo of M31 is found to be c/a = 0.55 ± 0.05.
Properties of the Galactic Bar from Hydrodynamical Simulations
Authors: Weiner Benjamin J. , Sellwood J.A.
Published: July 2016

It is well known that the existence of H I and CO gas at “forbidden” velocities in longitude-velocity (l–V) diagrams of the inner Galaxy (e.g. Liszt & Burton 1980, Liszt 1992) is inconsistent with circular motion in an axisymmetric potential. Gas flow in a barred potential could be consistent with the observations, however. We have compared the observations to 2-D hydrodynamical simulations of gas flows in a family of barred potentials. The gas flow pattern is very sensitive to the assumed potential, and the l–V distribution of cool gas in the inner Galaxy places strong constraints on several parameters of the Milky Way bar.
What is Sgr A∗?
Authors: Falcke H.
Published: July 2016

Sgr A∗ is the unique 1 Jy flat spectrum radio point source located at the dynamical center of the Galaxy and in the very center of the central star cluster (Eckart et al. 1993). Due to its unusual appearance it has long been speculated that this source is powered by a supermassive black hole–an object whose presence has been suspected to reside in the nuclei of many other galaxies as well. Its mass is believed to be as large as M• ∼ 2 m 106M⊙ (e.g. Genzel & Townes 1987) while a lower limit of M• > 200–2000M⊙ can be inferred from the low proper motion of Sgr A∗ (Backer – this volume). The currently best dynamical arguments for the million solar mass black hole stem from detailed stellar kinematic studies (Haller et al. 1995).
Diameter and Proper Motion of Sgr A∗
Authors: Backer D. C.
Published: July 2016

The best hypothesis for the energy source of the compact, nonthermal radio source in the center of our galaxy, Sagittarius A∗ (Sgr A∗), is accretion onto a massive black hole from winds emanating from nearby luminous stars. The hole mass, accretion rate, and ultimate fate of accreted matter are uncertain. In this report I give a summary of recent critical observations. The interpretation of these results supports this general hypothesis, and begins to place constraints on model parameters. If so, then Sgr A∗ is a miniature version of extragalactic AGNs in a quiescent state.
The Nature of the Scattering and Faraday Screens Toward the Galactic Center
Authors: Yusef-Zadeh F. , Parastaran P. , Wardle M. , Uchida K.
Published: July 2016

We probe the relationship between the scattering and Faraday screens toward the Galactic center by examining the scattering properties of Sgr A∗ and OH/IR stars and by measuring the rotation measure distribution of an extended nonthermal filament. The unusually large rotation and scattering measures, the evidence for anisotropic scattering, and the anisotropy in the rotation measure structure function, suggest that the Faraday and scattering media are located near the Galactic center. The results presented here are consistent with a turbulent medium of magnetized thermal electrons with the outer scale of electron density and magnetic field fluctuations being of the order of 5 × 10–4 and 2 pcs, respectively.
The Galactic Center Star Cluster: Normal Evolution!?
Authors: Schaerer Daniel
Published: July 2016

The star cluster in the Galactic center (GC) provides an exceptional test-ground for the evolution of stars in extreme environments. Its understanding is an important step for the study of stellar populations in starburst galaxies and AGN's. In this work we address the question if the central cluster can be understood by standard evolutionary scenarios, or whether other processes (collisions, mergers, atmosphere stripping etc.) need to be invoked. A more detailed account of this work will be published elsewhere.
Metallicity, Structure and Kinematics of the Milky Way's Bulge
Authors: Minniti Dante
Published: July 2016

One of the unsolved problems of the Milky Way is the interplay between the different components (disk, bulge and halo) in the inner regions, where they may all reach their maximum density. As a first approach to attack this problem, we summarize the results of a photometric and spectroscopic study of the Galactic bulge based on ∼700 K and M giants in 3 fields (Minniti 1993a). Table 1 lists the position of the fields, their projected Galactocentric distance, number of stars with spectra at present, and estimated disk contamination.
Galactic Bulges as an Evolutionary Phenomenon: Observational Evidence from the Statistics of “Box/Peanut” Bulges
Authors: Dettmar R.-J.
Published: July 2016

N-body simulations for stars in bar potentials have demonstrated over the last couple of years (e.g., Combes et al. 1990; Raha et al. 1991) that bars growing in z will lead to the presence of a bulge component. In such a scenario a central “bulge” component could develop as a resonance phenomenon caused by a bar and would be distinctly different from any “spheroidal” or “halo” component.
The Metal Pre-Enrichment of the Galactic Disk: Solving the G-Dwarf Problem
Authors: Samland M. , Hensler G.
Published: July 2016

The stellar metallicity distribution of low-mass stars is one of the major touchstones for models describing the chemical evolution of our Galaxy. In contrast to the gaseous components, the abundances of the stellar components also reflect the temporal enrichment. Hence, the stellar metallicity distribution is a stringent test for evolutionary models of galaxies.
Effects of Chaos in the Galactic Halo
Authors: Schuster W.J. , Allen C.
Published: July 2016

To study the way in which the principal periodic orbits in a Galactic potential determine orbital structure, horizontal and vertical surfaces of section, i.e. (dR/dt, R) and (dz/dt, z), are being used to explore the potential of Allen & Santillán (1991) and to investigate possible vertical structure in the Galactic halo. The chaotic “scattering” process due to the nearly spherical mass distribution close to the Galactic center in conjunction with the confinement of the chaotic orbits produces a vertical segregation of both chaotic and non-chaotic orbits in the halo. Certain zmax, zmin are preferred by the chaotic orbits over others as a result of the conservation of the total orbital energy and of the interaction and confinement of the chaotic orbits by the principal families of periodic orbits (Figure 1). Some of these periodic orbits have been identified. Correlations between the structure found in the observed W distribution and that of the numerically determined zmax, zmin histograms are shown for our sample of 280 halo stars (Schuster et al. 1993). W is the star's velocity perpendicular to the Galactic plane and zmax, zmin the maximum distances above or below the Galactic plane, respectively, reached by the star in the course of its orbit. This vertical structure may explain certain puzzling observations of the galactic halo, such as conflicting c/a values for the shape of the halo, and unusual velocity dispersions and/or distributions near the Galactic poles. These results are in good agreement with Hartwick's (1987) two component model for the halo.
The Chemodynamical Evolution of Spheroidal Systems and the Resultant Stellar Abundance Distribution Function
Authors: Tsujimoto T. , Shigeyama T. , Nomoto K.
Published: July 2016

We construct a chemo-dynamical model for galaxy formation using a three dimensional SPH method. We simulate the formation of two spheroidal systems, i.e., the elliptical galaxy and the Galactic bulge, based on the collapse scenario for protogalaxies. We obtain the chemodynamical formation and evolution models for the two systems during the first ∼ 1 Gyr. The relative ratio of kinetic to thermal energy of supernovae is found to heavily determine the outcome. By giving the explosion energy of supernovae to the interstellar gas with a physically meaningful relative ratio of kinetic to thermal energy, the elliptical galaxy model has the hot halo and the galactic wind, but it is not the case for the Galactic bulge model.
Vertical Equilibrium of HI in the Galactic Disk
Authors: Malhotra S.
Published: July 2016

The analysis of vertical distribution and kinematics of disks of galaxies can yield the local mass density in the disk, distinct from the integrated mass inside a radius, derived from a rotation curve. HI is a particularly good tracer because of its ubiquity, ease of observation, and near isothermal nature. In the simplest case one considers the turbulent pressure gradient of the gas balancing the gravitational force in the z-direction. But the atomic gas may be subject to other pressures, for example, magnetic, cosmic ray or radiation pressure. The relative contributions of these are essentially unconstrained. The mass densities obtained from the analysis of HI vertical equilibrium can be verified with a similar analysis only in the solar neighborhood, where the vertical distribution and kinematics of stars can give an independent measure of the total midplane mass density (ρ0).
The Dynamics of Planetary Nebulae in the Galaxy: Evidence for a Third Integral
Authors: Dejonghe H. , Durand S. , Acker A. , Chambat F.
Published: July 2016

The dynamical modeling of various tracer populations in our galaxy is an important tool in the study of its formation and evolution. Planetary Nebulae (PNe) seem to be particularly useful for such a study. In this contribution we attempt to link the dynamics of PNe and OH/IR stars, and confirm on dynamical grounds that both classes are indeed related by stellar evolution. Moreover, we show that 2 integrals of motion are probably not sufficient to characterize the dynamical state of the PNe: the models produce a velocity dispersion which is too low, pointing at the likely presence of a third integral.
Escape Velocities from Unstable Triple Stars
Authors: Anosova J. , Tanikawa K. , Colin J. , Kiseleva L. , Eggleton P.
Published: July 2016

In order to investigate a possible origin for stars with high peculiar velocities in the thick disc of our Galaxy, the dynamical evolution of 16 000 three-dimensional triple systems which consist of a binary with equal or comparable masses of componentsM1andM2and a low-mass third bodyM3is considered. We examine an extensive range of initial conditions with positions of the bodyM3randomly distributed around and inside the binary orbit.M3was given the initial radial velocityV0with respect to the center of inertia of the binary. The following dynamical system of units is used in this work: the unit of distance is the semi-major axis of the binary orbit, the unit of time is the period of the binary; the universal constant of gravity is unity. In these units the total mass of the close binary is 4π2.
The Search for Cold Molecular Gas in the Outer Galaxy
Authors: de Geus E.J. , Phillips J.A.
Published: July 2016

It is well known that the rotation curves of many galaxies remain flat well outside their optical disks. This leads to the conclusion that the visible mass in galaxies is only a small fraction of the total (see e.g. Faber & Gallagher 1979). Although we are certain that “dark matter” exists, its composition and distribution are still unknown.

In a recent paper Pfenniger et al. (1994) argued strongly for the possibility that dark matter could well be in the form of cold, predominantly molecular gas in a flat distribution. To have escaped previous detection in the outer parts of our Galaxy, the gas would need to have a low temperature and thus a low emissivity. Because most substantial heating sources of gas are associated with the presence of massive stars (UV radiation and cosmic rays) this requirement may be satisfied in the Galactic plane outside the optical disk.
How Does Star Formation Affect the Large Scale Structure of the ISM?
Authors: Palouš Jan
Published: July 2016

Nearly all the star formation in the Milky Way and nearby spiral galaxies occurs in the giant molecular clouds (GMC). Inside the GMC's the units of star formation are the high density (≥ 103cm–3) and high mass (≥ 103M⊙) clumps (Blitz, 1991). Once a GMC is “infected” by star formation many clumps form stars producing a star forming region. The formation of massive stars induces destructive processes, such as H2 dissociation, HI ionization, stellar winds and supernova explosions, thus self-limiting the lifetime of GMC to ∼ 3 107 years.
Molecular Mass Distribution in the Outer Galaxy
Authors: Carey Sean J. , Mead Kathryn N. , Kutner Marc L.
Published: July 2016

The extent and nature of molecular material in the outer Galaxy (R > R⊙) has been an open, interesting question since the discovery of molecular material in the outer Galaxy (Kutner & Mead, 1981). From large scale CO surveys, two estimates of the total molecular mass have been made with the same result, M(H2) = 6 × 108 M⊙ (Wouterloot et al., 1990), (Digel et al., 1990). Both estimates have a strong bias towards large, star forming (warm) clouds. Wouterloot et al. used the IRAS point source catalog as a finder chart for their observations and the inner Galaxy mass distribution to scale their result. Digel et al. conducted an unbiased survey with a large (8.8 arcminute) beam which underestimated the amount of material in small clouds due to the effects of beam dilution.
HI Bubbles around NGC 6888
Authors: de Nicolau C. Cappa , Rogers C. , Dubner G. , St.-Louis N.
Published: July 2016

The interstellar bubbles are generally the result of the interaction of strong stellar winds with the surrounding material. HI voids and shells have been disclosed around several WR stars in our Galaxy (e.g. Niemela & Cappa de Nicolau 1991, Dubner et al. 1992). We report here an analysis of the interstellar medium in the vicinity of the WR star HD 192163 = WR 136 and the optical ring nebula NGC 6888 based on HI observations. Our aim is to look for the traces left in the cold interstellar gas by the action of the stellar winds of HD 192163.
Search for HI Bubbles Around WR Stars: WR 149
Authors: de Nicolau C. Cappa , Niemela V.S. , Herbstmeier U. , Koribalski B.
Published: July 2016

The interaction of strong stellar winds with the interstellar medium creates large cavities or interstellar bubbles surrounded by expanding outer shells. 21-cm line (HI) observations have revealed the presence of such neutral gas bubbles around several WR stars (e.g. Niemela & Cappa de Nicolau 1991 and references therein; Dubner et al. 1992).

Continuing our search for HI bubbles around WR stars, we have analyzed the neutral hydrogen distribution in the vicinity of the Wolf-Rayet star WR149, a highly reddened WN6-7 star located at 6.5 kpc in the direction (l,b) = (89.°53,+0.°65).
GS64-01-97: Expanding Supershell in the Milky Way
Authors: Ehlerová S. , Jungwiert B. , Palouš J.
Published: July 2016

The expansion of shocked interstellar medium around an OB association is an example of the astrophysical blastwave (Ostriker and McKee, 1988). The thin, cold, shell-like structure expanding supersonically accumulates the ambient medium. We assume that the shell has the zero thickness at radius of the shockwave rs and that it expands at velocity vs. The shell is divided into elements described with equations of motion: d/dt(Mvs) = dS[(P–Po) + novo(vs–vo)]–Mg(R,z), where M and dS are the mass and the surface of it, P, Po are the inside and outside pressures, no,vo are density and velocity of the ambient medium and g(R,z) is the gravitational acceleration in the Galaxy. R, z are the galactocentric cylindrical coordinates. The mass of an element increases as long as the expansion velocity component normal to the shell, v⊥ exceeds the velocity of sound in the ambient medium M = v⊥nodS. The 3D model using the above infinitesimally thin shell approximation was developed by Palouš (1990, 1992) and Silich (1992).
G54.4–0.3 — Multi-Frequency Investigation of an SNR in Interaction with the ISM
Authors: Junkes N.
Published: July 2016

G54.4–0.3 is an extended shell-type supernova remnant (SNR) in the Galactic plane. We selected this source as a candidate for the interaction of SNRs with the interstellar medium on the base of an investigation of cool IRAS point sources in the direction of SNRs. We found a statistical excess of IRAS sources with FIR spectra similar to young stellar objects (Td ≈ 25 − 45 K) in the vicinity of G54.4–0.3 and a number of other SNRs in the northern hemisphere (Junkes & Fürst 1992).
How ought one Parameterize the Milky Way?
Authors: Schechter Paul L.
Published: July 2016

In a well known paper written a quarter century ago, cosmology was described as a search for two numbers (Sandage 1970). As those of you who have attended any of the parallel sessions of Symposium 167 surely appreciate, today's cosmologists find more than just two numbers interesting. It is likewise clear from the present symposium that the number of interesting parameters associated with the Milky Way is very much greater than two.
How do the Stellar Disc and Thick Disc Stop?
Authors: Robin A.C. , Crézé M. , Mohan V.
Published: July 2016

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Very deep CCD frames probe the most external parts of the disc, providing strong evidence that the galactic density scale length for the old disc population is rather short (2.5 kpc) and drops abruptly beyond 5.5-6 kpc.

Deeper frames in the I band allow to estimate photometric distances and confirm the position of the disk edge. A few stars are found at larger distances. Their number is exactly what we expect if the thick disk does not have any cutoff. We discuss the implications for the formation and evolution of the disc, for the star formation threshold, and for the origin of the thick disc population.
Proper Motion Study of the Galactic Rotation Curve
Authors: Fuchs B. , Frink S. , Röser S. , Wielen R.
Published: July 2016

The galactic rotation curve has been determined using the space velocities of 197 OB stars associated with 59 HII regions.
The Mass Distribution of the Milky Way Deduced from Globular Cluster Dynamics
Authors: Dauphole B. , Colin J. , Geffert M. , Odenkirchen M. , Tucholke H.-J.
Published: July 2016

We present here a new analytical Galactic potential. We used the constraint of galactic globular cluster dynamics compared to their spatial distribution. This was done with the help of the globular clusters' proper motions. The result for the clusters dynamics show a better agreement between orbital parameters and statistical distribution of the studied globular clusters than in previous published potentials. The globular cluster dynamics constrain the mass distribution on a large scale, until 40 kpc from the centre. In this model, the total mass for the Milky Way is 7.9 1011 M⊙.
The Rotation Curve from A-F Supergiants
Authors: Peterson D. M. , Slowik D.
Published: July 2016

The Galactic rotation law provides critical information for estimating the distribution of mass in the Galaxy, for tying the distance of the Sun from the Galactic center to local distance scales, and, if determined over large enough distances, for estimating the total mass of the system and the amount of nonluminous matter present. Interior to the Sun velocities are well defined by observations of the ISM, particularly HI. These techniques are not available for points exterior to the Sun and we must rely on observations of velocities of objects whose distances can be estimated. Notable among these are the Cepheids (Pont et al 1994) and the combination of CO velocities and OB cluster distances (Brand & Blitz 1993) where the two are found to coexist. Adding a new class of objects, particularly bright, relatively common objects to this effort is of importance.
Aspects of Hadamard well-posedness for classes of non-Lipschitz semilinear parabolic partial differential equations
Authors: Meyer J. C. , Needham D. J.
Published: July 2016

We study classical solutions of the Cauchy problem for a class of non-Lipschitz semilinear parabolic partial differential equations in one spatial dimension with sufficiently smooth initial data. When the nonlinearity is Lipschitz continuous, results concerning existence, uniqueness and continuous dependence on initial data are well established (see, for example, the texts of Friedman and Smoller and, in the context of the present paper, see also Meyer), as are the associated results concerning Hadamard well-posedness. We consider the situations when the nonlinearity is Hölder continuous and when the nonlinearity is upper Lipschitz continuous. Finally, we consider the situation when the nonlinearity is both Hölder continuous and upper Lipschitz continuous. In each case we focus upon the question of existence, uniqueness and continuous dependence on initial data, and thus upon aspects of Hadamard well-posedness.
Well-posedness and regularity of linear hyperbolic systems with dynamic boundary conditions
Authors: Peralta Gilbert , Propst Georg
Published: July 2016

We consider first-order hyperbolic systems on an interval with dynamic boundary conditions. These systems occur when the ordinary differential equation dynamics on the boundary interact with the waves in the interior. The well-posedness for linear systems is established using an abstract Friedrichs theorem. Due to the limited regularity of the coefficients, we need to introduce the appropriate space of test functions for the weak formulation. It is shown that the weak solutions exhibit a hidden regularity at the boundary as well as at interior points. As a consequence, the dynamics of the boundary components satisfy an additional regularity. Neither result can be achieved from standard semigroup methods. Nevertheless, we show that our weak solutions and the semigroup solutions coincide. For illustration, we give three particular physical examples that fit into our framework.
The genus, Frobenius number and pseudo-Frobenius numbers of numerical semigroups of type 2
Authors: Robles-Pérez Aureliano M. , Rosales José Carlos
Published: July 2016

We study some questions on numerical semigroups of type 2. On the one hand, we investigate the relation between the genus and the Frobenius number. On the other hand, for two fixed positive integers g1, g2, we give necessary and sufficient conditions in order to have a numerical semigroup S such that {g1, g2} is the set of its pseudo-Frobenius numbers and, moreover, we explicitly build families of such numerical semigroups.
Dynamics of a susceptible–infected–susceptible epidemic reaction–diffusion model
Authors: Keng Deng  , Yixiang Wu
Published: July 2016

We study a susceptible–infected–susceptible reaction–diffusion model with spatially heterogeneous disease transmission and recovery rates. A basic reproduction number is defined for the model. We first prove that there exists a unique endemic equilibrium if . We then consider the global attractivity of the disease-free equilibrium and the endemic equilibrium for two cases. If the disease transmission and recovery rates are constants or the diffusion rate of the susceptible individuals is equal to the diffusion rate of the infected individuals, we show that the disease-free equilibrium is globally attractive if , while the endemic equilibrium is globally attractive if .
The moment exponential stability criterion of nonlinear hybrid stochastic differential equations and its discrete approximations
Authors: Zong Xiaofeng , Wu Fuke , Huang Chengming
Published: July 2016

Based on the martingale theory and large deviation techniques, we investigate the pth moment exponential stability criterion of the exact and numerical solutions to hybrid stochastic differential equations (SDEs) under the local Lipschitz condition. This new stability criterion shows that Markovian switching can serve as a stochastic stabilizing factor by its logarithmic moment-generating function. We also investigate the pth moment exponential stability of Euler–Maruyama (EM), backward EM (BEM) and split-step backward EM (SSBEM) approximations for hybrid SDEs and show that, under the additional linear growth condition, the EM method can share the mean-square exponential stability of the exact solution for sufficiently small step size. However, the BEM method can work without the linear growth condition. We further investigate the SSBEM method under a coupled condition.
Chromatic input to cells of the magnocellular pathway: Mean
chromaticity and the relative phase of modulated lights
Authors: LEE BARRY B. , SUN HAO
Published: July 2016

If the relative phase of red and green modulated lights is changed,
at low temporal frequencies the response of cells of the magnocellular
(MC) pathway has been found to be minimal not to counterphase,
chromatic modulation (as expected of a luminance mechanism) but shifted
to some phase intermediate between luminance and chromatic modulation.
The results could only be modeled by assuming interaction between
achromatic and chromatic inputs to MC cells. The ‘phase
shift’ resembled that seen with psychophysical threshold
measurements using the same stimuli. Psychophysical results also showed
that the phase shift is dependent on the chromaticity of a background.
The results reported here show that the direction of the phase shift in
MC cells is reversed by changing the background from long to short
wavelengths and is consistent with psychophysical observations. Cell
behavior was again modeled by assuming vector summation of achromatic
and chromatic inputs. The reversal of phase-shift direction requires a
reversal in polarity of the chromatic input. The underlying
physiological mechanism may involve summation of chromatic signals of
opposite polarity; if the relative size of these signals depends on the
background, this may determine the direction of phase shift.
Parents’ preparedness for their infants’ discharge following first-stage cardiac surgery: development of a parental early warning tool
Authors: Gaskin Kerry L. , Barron David J. , Daniels Amanda
Published: July 2016

Aim

The aim of this study was to explore parental preparedness for discharge and their experiences of going home with their infant after the first-stage surgery for a functionally univentricular heart.

Background

Technological advances worldwide have improved outcomes for infants with a functionally univentricular heart over the last 3 decades; however, concern remains regarding mortality in the period between the first and second stages of surgery. The implementation of home monitoring programmes for this group of infants has improved this initial inter-stage survival; however, little is known about parents’ experiences of going home, their preparedness for discharge, and parents’ recognition of deterioration in their fragile infant.

Method

This study was conducted in 2011–2013; eight sets of parents were consulted in the research planning stage in September, 2011, and 22 parents with children aged 0–2 years responded to an online survey during November, 2012–March, 2013. Description of categorical data and deductive thematic analysis of the open-ended questions were undertaken.

Results

Not all parents were taught signs of deterioration or given written information specific to their baby. The following three themes emerged from the qualitative data:mixed emotions about going home,knowledge and preparedness, andsupport systems.

Conclusions

Parents are not adequately prepared for discharge and are not well equipped to recognise deterioration in their child. There is a role for greater parental education through development of an early warning tool to address the gap in parents’ understanding of signs of deterioration, enabling appropriate contact and earlier management by clinicians.
Kant's Third Critique: The Project of Unification
Authors: Gardner Sebastian
Published: July 2016

This paper offers a synoptic view of Kant's Critique of the Power of Judgement and its reception by the German Idealists. I begin by sketching Kant's conception of how its several parts fit together, and emphasize the way in which the specifically moral motivation of Kant's project of unification of Freedom and Nature distances it from our contemporary philosophical concerns. For the German Idealists, by contrast, the CPJ's conception of the opposition of Freedom and Nature as defining the overarching task of philosophy provides a warrant and basis for bold speculative programmes. The German Idealist development therefore presupposes Kant's failure in the CPJ to resolve the problem of the relation of Freedom and Nature. What is fundamentally at issue in the argument between Kant and his successors is the question of the correct conception of philosophical systematicity and in this context I reconstruct Kant's defence of his claim to philosophical finality.
Zeitliche Trends bei den Häufigkeiten für Aufmerksamkeitsdefizit-/Hyperaktivitätsstörungen (ADHS) und Stimulanzienbehandlung
Authors: Steinhausen Hans-Christoph , Döpfner Manfred , Schubert Ingrid
Published: July 2016

Zusammenfassung. Zeitliche Veränderungen in der Häufigkeit psychischer Störungen stellen besondere Herausforderungen für die Versorgungsplanung dar. In dieser Übersichtsarbeit wird die spezielle Frage nach einer Zunahme der Prävalenz- und Inzidenzraten von Aufmerksamkeitsdefizit-/Hyperaktivitätsstörungen (ADHS) anhand von Ergebnissen internationaler epidemiologischer Studien aus mehreren Jahrzehnten geprüft. Während Studien zur Prävalenz keine Hinweise auf eine systematische Zunahme von ADHS in den jeweils untersuchten Bevölkerungen liefern, zeigen nationale und internationale Studien zur Inzidenz von ADHS, dass die Anzahl behandelter Personen mit ADHS in der jüngeren Vergangenheit deutlich angestiegen ist. Dieser Anstieg ist auch bei Kontrolle einer allgemein gestiegenen Inanspruchnahme der Psychiatrie noch nachzuweisen. Insgesamt hat sich also die Kluft zwischen Behandlungsbedürftigkeit und tatsächlicher Behandlung bei ADHS über die Zeit verringert. Hingegen haben deutsche Studien zur Verschreibung von Medikamenten nach Jahren des Anstiegs in jüngster Zeit auch abnehmende Tendenzen gezeigt.
Charting Ice Sheet Contributions to Global Sea Level Rise
Authors: Briggs Kate , Shepherd Andrew , Hogg Anna , Ivins Erik , Schlegel Nicole , Joughin Ian , Smith Ben , Krinner Gerhard , Moyano Gorka , Nowicki Sophie , Payne Tony , Rignot Eric , Velicogna Isabella , Scambos Ted , van den Broeke Michiel , Whitehouse Pippa
Published: July 2016

An international team produced an integrated assessment of polar ice mass losses in 2012. Now efforts to provide an up-to-date assessment are under way, with an open invitation for participation.
Cellular mechanisms for cargo delivery and polarity maintenance at different polar domains in plant cells
Authors: Łangowski Łukasz , Wabnik Krzysztof , Li Hongjiang , Vanneste Steffen , Naramoto Satoshi , Tanaka Hirokazu , Friml Jiří
Published: July 2016

The asymmetric localization of proteins in the plasma membrane domains of eukaryotic cells is a fundamental manifestation of cell polarity that is central to multicellular organization and developmental patterning. In plants, the mechanisms underlying the polar localization of cargo proteins are still largely unknown and appear to be fundamentally distinct from those operating in mammals. Here, we present a systematic, quantitative comparative analysis of the polar delivery and subcellular localization of proteins that characterize distinct polar plasma membrane domains in plant cells. The combination of microscopic analyses and computational modeling revealed a mechanistic framework common to diverse polar cargos and underlying the establishment and maintenance of apical, basal, and lateral polar domains in plant cells. This mechanism depends on the polar secretion, constitutive endocytic recycling, and restricted lateral diffusion of cargos within the plasma membrane. Moreover, our observations suggest that polar cargo distribution involves the individual protein potential to form clusters within the plasma membrane and interact with the extracellular matrix. Our observations provide insights into the shared cellular mechanisms of polar cargo delivery and polarity maintenance in plant cells.
Stat3 and C/EBPβ synergize to induce miR‐21 and miR‐181b expression during sepsis
Authors: McClure Clara , McPeak Melissa B , Youssef Dima , Yao Zhi Q , McCall Charles E , El Gazzar Mohamed
Published: July 2016

Myeloid‐derived suppressor cells (MDSCs) increase late sepsis immunosuppression and mortality in mice. We reported that microRNA (miR) 21 and miR‐181b expression in Gr1+CD11b+ myeloid progenitors increase septic MDSCs in mice by arresting macrophage and dendritic cell differentiation. Here, we report how sepsis regulates miR‐21 and miR‐181b transcription. In vivo and in vitro binding studies have shown that C/EBPα transcription factor, which promotes normal myeloid cell differentiation, binds both miRNA promoters in Gr1+CD11b+ cells from sham mice. In contrast, in sepsis Gr1+CD11b+ MDSCs miR‐21 and miR‐181b promoters bind both transcription factors Stat3 and C/EBPβ, which co‐imunoprecipitate as a single complex. Mechanistically, transcription factor Rb phosphorylation supports Stat3 and C/EBPβ accumulation at both miRNA promoters, and C/EBPβ or Stat3 depletion by siRNA in sepsis Gr1+CD11b+ MDSCs inhibits miR‐21 and miR‐181b expression. To further support this molecular path for MDSC accumulation, we found that Stat3 and C/EBP binding at miR‐21 or miR‐181b promoter was induced by IL‐6, using a luciferase reporter gene transfection into naive Gr1+CD11b+ cells. Identifying how sepsis MDSCs are generated may inform new treatments to reverse sepsis immunosuppression.
Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe
Authors: Sun J. P. , Matsuura K. , Ye G. Z. , Mizukami Y. , Shimozawa M. , Matsubayashi K. , Yamashita M. , Watashige T. , Kasahara S. , Matsuda Y. , Yan J. -Q. , Sales B. C. , Uwatoko Y. , Cheng J. -G. , Shibauchi T.
Published: July 2016

The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (Tc) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of Tc has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ∼15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ∼6 GPa the sudden enhancement of superconductivity (Tc≤38.3 K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-Tc phase above 6 GPa. The obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-Tc cuprates.
Direct detection of a single photon by humans
Authors: Tinsley Jonathan N. , Molodtsov Maxim I. , Prevedel Robert , Wartmann David , Espigulé-Pons Jofre , Lauwers Mattias , Vaziri Alipasha
Published: July 2016

Despite investigations for over 70 years, the absolute limits of human vision have remained unclear. Rod cells respond to individual photons, yet whether a single-photon incident on the eye can be perceived by a human subject has remained a fundamental open question. Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance. This was achieved by implementing a combination of a psychophysics procedure with a quantum light source that can generate single-photon states of light. We further discover that the probability of reporting a single photon is modulated by the presence of an earlier photon, suggesting a priming process that temporarily enhances the effective gain of the visual system on the timescale of seconds.
The anti-sigma factor RsrA responds to oxidative stress by reburying its hydrophobic core
Authors: Rajasekar Karthik V. , Zdanowski Konrad , Yan Jun , Hopper Jonathan T. S. , Francis Marie-Louise R. , Seepersad Colin , Sharp Connor , Pecqueur Ludovic , Werner Jörn M. , Robinson Carol V. , Mohammed Shabaz , Potts Jennifer R. , Kleanthous Colin
Published: July 2016

Redox-regulated effector systems that counteract oxidative stress are essential for all forms of life. Here we uncover a new paradigm for sensing oxidative stress centred on the hydrophobic core of a sensor protein. RsrA is an archetypal zinc-binding anti-sigma factor that responds to disulfide stress in the cytoplasm of Actinobacteria. We show that RsrA utilizes its hydrophobic core to bind the sigma factor σR preventing its association with RNA polymerase, and that zinc plays a central role in maintaining this high-affinity complex. Oxidation of RsrA is limited by the rate of zinc release, which weakens the RsrA–σR complex by accelerating its dissociation. The subsequent trigger disulfide, formed between specific combinations of RsrA’s three zinc-binding cysteines, precipitates structural collapse to a compact state where all σR-binding residues are sequestered back into its hydrophobic core, releasing σR to activate transcription of anti-oxidant genes.
The feeder system of the Toba supervolcano from the slab to the shallow reservoir
Authors: Koulakov Ivan , Kasatkina Ekaterina , Shapiro Nikolai M. , Jaupart Claude , Vasilevsky Alexander , El Khrepy Sami , Al-Arifi Nassir , Smirnov Sergey
Published: July 2016

The Toba Caldera has been the site of several large explosive eruptions in the recent geological past, including the world’s largest Pleistocene eruption 74,000 years ago. The major cause of this particular behaviour may be the subduction of the fluid-rich Investigator Fracture Zone directly beneath the continental crust of Sumatra and possible tear of the slab. Here we show a new seismic tomography model, which clearly reveals a complex multilevel plumbing system beneath Toba. Large amounts of volatiles originate in the subducting slab at a depth of ∼150 km, migrate upward and cause active melting in the mantle wedge. The volatile-rich basic magmas accumulate at the base of the crust in a ∼50,000 km3 reservoir. The overheated volatiles continue ascending through the crust and cause melting of the upper crust rocks. This leads to the formation of a shallow crustal reservoir that is directly responsible for the supereruptions.
Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery
Authors: Clarkson M. O. , Wood R. A. , Poulton S. W. , Richoz S. , Newton R. J. , Kasemann S. A. , Bowyer F. , Krystyn L.
Published: July 2016

The end-Permian mass extinction, ∼252 million years ago, is notable for a complex recovery period of ∼5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe–S–C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota.
Salt marsh vegetation promotes efficient tidal channel networks
Authors: Kearney William S. , Fagherazzi Sergio
Published: July 2016

Tidal channel networks mediate the exchange of water, nutrients and sediment between an estuary and marshes. Biology feeds back into channel morphodynamics through the influence of vegetation on both flow and the cohesive strength of channel banks. Determining how vegetation affects channel networks is essential in understanding the biological functioning of intertidal ecosystems and their ecosystem services. However, the processes that control the formation of an efficient tidal channel network remain unclear. Here we compare the channel networks of vegetated salt marshes in Massachusetts and the Venice Lagoon to unvegetated systems in the arid environments of the Gulf of California and Yemen. We find that the unvegetated systems are dissected by less efficient channel networks than the vegetated salt marshes. These differences in network geometry reflect differences in the branching and meandering of the channels in the network, characteristics that are related to the density of vegetation on the marsh.
Correction: Corrigendum: Selectively enhanced photocurrent generation in twisted bilayer graphene with van Hove singularity
Authors: Yin Jianbo , Wang Huan , Peng Han , Tan Zhenjun , Liao Lei , Lin Li , Sun Xiao , Koh Ai Leen , Chen Yulin , Peng Hailin , Liu Zhongfan
Published: July 2016

Nature Communications 7: Article numbber:10699 (2015); Published: 7 March 2016; Updated: 19 July 2016. Technical support for this Article was not fully acknowledged. The Acknowledgements should have included the following: We are also grateful to Dr Alexei Barinov for his kind help during our beamtime at the spectramicroscopy beamline of the Elettra synchrotron.