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Evolution of a pickup ion ring-beam population in large-scale interstellar turbulence and small-scale self-generated waves: Implications for the IBEX ribbon
(American Astronomical Society, 2026) Huang, Y; Guo, F; Sun, X; Noh, SJ; Zirnstein, EJ; Reisenfeld, DB; Li, H; Florinski, V; Heerikhuisen, Jacob
The secondary energetic neutral atom (ENA) mechanism proposed to explain the ribbon-like enhancement of ENA emission observed by Interplanetary Boundary Explorer (IBEX) involves a pickup ion (PUI) ring-beam population beyond the heliopause. The stability of this highly anisotropic PUI distribution is crucial for determining the physical process responsible for the ribbon formation. It has been proposed that PUIs with pitch angles near 90° can become trapped via the magnetic mirroring process in the turbulent magnetic field of the local interstellar medium. However, the turbulent mirroring scenario typically neglects self-generated waves excited by the kinetic instabilities of the ring-beam PUIs, which can efficiently scatter PUIs in pitch angle. Using a magnetohydrodynamics-particle-in-cell approach implemented in ATHENA++, we simulate the evolution of the ring-beam PUIs, incorporating both large-scale interstellar magnetic fluctuations and microscale self-excited instabilities. We examine the competition between turbulent mirroring and pitch-angle scattering by the self-generated waves. Our results show that the PUIs can be rapidly scattered toward a nearly isotropic distribution on the order of one day, much shorter than their characteristic lifetime of a couple of years. This suggests that theoretical difficulties remain for maintaining an anisotropic PUI distribution in physical models of the IBEX ribbon.
Poisson–Dirichlet approximation for the stationary distribution of the inclusion process
(Elsevier BV, 2026) Gan, Han L
We consider the approximation of the stationary distribution of the finite inclusion process with the Poisson–Dirichlet distribution. Using Stein’s method, we derive an explicit bound for the approximation error, which is of order 1/N in the thermodynamic limit. The results are achieved from a minor modification to Stein’s method for Poisson–Dirichlet distribution approximation developed in Gan and Ross, (2021). The derivatives used on test functions in Gan and Ross, (2021) were directional type derivatives specifically chosen for their measure preserving properties. Depending upon the application, these derivatives can prove cumbersome. In this note, we show that for certain test functions we can instead use more traditional derivatives, which simplifies the bounds for the Stein factors and is more amenable to the approximation of the inclusion process.
How should the information profession respond to generative artificial intelligence (GenAI)?
(SAGE Publications, 2026) Lueg, Christopher; Nichols, David M; Twidale, Michael
The internet-fueled digital information environment of the future will likely contain many contentious media objects as creation costs are significantly lower when using generative artificial intelligence (GenAI). We argue that responding to the impact of GenAI is a challenge to the whole information profession. Acknowledging the diversity among GLAM institutions (Galleries, Libraries, Archives, Museums) we propose that GLAM institutions along with their specific strengths are well placed for guiding, if not overseeing, proposed authenticity infrastructures to complement the demand for improved media literacies in the age of GenAI as these institutions are able to engage with the public in ways that often exceed the reach of more technology-focused organizations.
The factors involved in surgical decision-making in younger women diagnosed with breast cancer in Aotearoa New Zealand: A qualitative analysis
(SAGE Publications, 2024) Blackmore, Tania; Norman, Kimberley; Burrett, Vanessa; Scarlet, Jenni; Campbell, Ian; Lawrenson, Ross
Women diagnosed with breast cancer must make important surgical decisions. The decision-making process for younger women is complex, with this group more likely to have an advanced diagnosis and life-stage considerations that can impact on treatment. This study investigated the decision-making process of women aged <50 years who had undergone breast cancer surgery within the preceding 12 months in Aotearoa New Zealand. Twelve women participated in semi-structured qualitative interviews to explore the factors that influenced treatment decisions. Thematic analysis resulted in three themes. Fear was the main concept identified as the primary influence on initial decision-making. Good quality shared decision-making between patient and clinician was found to provide essential support during the diagnosis to treatment period. In addition, women expressed a need for multi-modal presentation of medical information and more material reflecting younger women. These findings inform provision for younger women making surgical decisions when diagnosed with breast cancer.
Magnetohydrodynamic turbulence and the associated spatial diffusion tensor of cosmic rays in dynamical galactic halos
(EDP Sciences, 2025) Kleimann, J; Fichtner, H; Stein, M; Dettmar, RJ; Bomans, DJ; Oughton, Sean
Context. A detailed understanding of cosmic-ray transport in galactic halos is essential for explaining various observations, such as the radio continuum measurements of synchrotron radiation from energetic electrons. Of central importance is the spatial diffusion tensor of cosmic rays, which can be computed in an ab initio manner if the turbulence in the background medium is known. Aims. The study aimed to establish a suitable framework to compute the evolution of magnetohydrodynamic (MHD) turbulence and, hence, the diffusion tensor in the dynamical halos of galaxies. Methods. The Reynolds-averaged single-fluid MHD equations were solved numerically on a cylindrical grid, assuming axial symmetry and fixed boundary conditions on a central ellipsoid representing the galaxy. The physical properties of both large-scale MHD and small-scale turbulent quantities, including the coefficients of parallel and perpendicular diffusion, were extracted from the resulting steady state. Results. Hydrodynamic validation revealed a persistent instability of the near-axis flow, which could be traced to the galaxy's gravitating mass. The results for the evolution of MHD turbulence in a galactic halo-using parameters approximating those of NGC 4631-enabled an ab initio computation of the spatial diffusion tensor of cosmic rays through the application of a state-of-the-art nonlinear theory. Conclusions. The simulation results reveal variation in turbulence quantities, (i.e., fluctuation energy, correlation scale, and cross helicity) in a dynamical halo. Furthermore, the corresponding diffusion tensor of cosmic rays exhibits significant variation throughout such a halo.