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1. Ionization energies and cationic bond dissociation energies of RuB, RhB, OsB, IrB, and PtB

   https://doi.org/10.1063/5.0107086  

   Merriles, Dakota M.; Morse, Michael D. (August 2022, The Journal of Chemical Physics)

   Two-photon ionization thresholds of RuB, RhB, OsB, IrB, and PtB have been measured using resonant two-photon ionization spectroscopy in a jet-cooled molecular beam and have been used to derive the adiabatic ionization energies of these molecules. From the measured two-photon ionization thresholds, IE(RuB) = 7.879(9) eV, IE(RhB) = 8.234(10) eV, IE(OsB) = 7.955(9) eV, IE(IrB) = 8.301(15) eV, and IE(PtB) = 8.524(10) eV have been assigned. By employing a thermochemical cycle, cationic bond dissociation energies of these molecules have also been derived, giving D0(Ru+–B) = 4.297(9) eV, D0(Rh+–B) = 4.477(10) eV, D0(Os–B+) = 4.721(9) eV, D0(Ir–B+) = 4.925(18) eV, and D0(Pt–B+) = 5.009(10) eV. The electronic structures of the resulting cationic transition metal monoborides (MB+) have been elucidated using quantum chemical calculations. Periodic trends of the MB+ molecules and comparisons to their neutral counterparts are discussed. The possibility of quadruple chemical bonds in all of these cationic transition metal monoborides is also discussed. 

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2. Conservation of longitudinal spin polarization of positrons emitted from a thin Ni(100) foil

   https://doi.org/10.1103/PhysRevA.107.062809  

   Cecchini, G. G.; Greaves, R. G.; Mills, A. P. (June 2023, Physical Review A)

   We have discovered that 5 keV bursts of 5 × 107 positrons with an initial longitudinal spin polarization of (28.8 ± 0.7)%, when implanted into a thin Ni(100) crystal, are emitted with 20% efficiency at thermal energies from its surface with (30.9 ± 0.5)% polarization. We conclude that the positron spin polarization is preserved while interacting with the Ni, despite the 0.61 T average transverse magnetization of the Ni at room temperature. The resulting polarized beam has been focused to a 0.025-mm mean-diameter spot when accelerated to 5 keV and will be uniquely suited for experiments on a neutral spin aligned e+-e − plasma, spin- and angle-resolved positronium emission spectroscopy, and critical for producing a triplet positronium Bose-Einstein condensate. 

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3. Action principles and conservation laws for Chew–Goldberger–Low anisotropic plasmas

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   Webb, G.M.; Anco, S.C.; Meleshko, S.V.; Zank, G.P. (August 2022, Journal of Plasma Physics)

   The ideal Chew–Goldberger–Low (CGL) plasma equations, including the double adiabatic conservation laws for the parallel ( $$p_\parallel$$ ) and perpendicular pressure ( $$p_\perp$$ ), are investigated using a Lagrangian variational principle. An Euler–Poincaré variational principle is developed and the non-canonical Poisson bracket is obtained, in which the non-canonical variables consist of the mass flux $${\boldsymbol {M}}$$ , the density $$\rho$$ , the entropy variable $$\sigma =\rho S$$ and the magnetic induction $${\boldsymbol {B}}$$ . Conservation laws of the CGL plasma equations are derived via Noether's theorem. The Galilean group leads to conservation of energy, momentum, centre of mass and angular momentum. Cross-helicity conservation arises from a fluid relabelling symmetry, and is local or non-local depending on whether the gradient of $$S$$ is perpendicular to $${\boldsymbol {B}}$$ or otherwise. The point Lie symmetries of the CGL system are shown to comprise the Galilean transformations and scalings. 

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4. Precision Electroweak Measurements with ILC250

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   Wilson, Graham (January 2021, Proceedings of 40th International Conference on High Energy physics — PoS(ICHEP2020))

   null (Ed.)

   We discuss the improvements that the ILC can make in precision electroweak observables based on studies with the ILD detector concept. These include observables from WW production at a centre of mass energy of 250 GeV and above, and especially from a dedicated stage of running at the Z pole. These improvements take advantage of the ILC capabilities for polarized electron and positron beams, and an accelerator design that accommodates data-taking at a wide range of beam energies. The studies include experimental considerations evaluated in the context of the ILD detector concept and discussion of experimental strategies targeted at controlling especially systematic uncertainties associated with the center-of-mass energy. 

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5. Disclosing the catalog pulsars dominating the Galactic positron flux

   https://doi.org/10.1088/1475-7516/2025/02/029  

   Orusa, Luca; Manconi, Silvia; Donato, Fiorenza; Mauro, Mattia Di (February 2025, Journal of Cosmology and Astroparticle Physics)

   Abstract The cosmic-ray flux of positrons is measured with high precision by the space-borne particle spectrometer AMS-02. The hypothesis that pulsars and their nebulae can significantly contribute to the excess of the AMS-02 positron flux has been consolidated after the observation of aγ-ray emission at GeV and TeV energies of a few degree size around a few sources, that provide indirect evidence that electron and positron pairs are accelerated to very high energies from these sources.By modeling the emission from pulsars in the ATNF catalog, we find that combinations of positron emission from cataloged pulsars and secondary production can fit the observed AMS-02 data. Our results show that a small number of nearby, middle-aged pulsars, particularly B1055-52, Geminga (J0633+1746), and Monogem (B0656+14), dominate the positron emission, contributing up to 80% of the flux at energies above 100 GeV. From the fit to the data, we obtain a list of the most important sources for which we recommend multi-wavelength follow-up observations, particularly in theγ-ray and X-ray bands, to further constrain the injection and diffusion properties of positrons. 

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