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1. Final results for the neutron β -asymmetry parameter A 0 from the UCNA experiment

   https://doi.org/10.1051/epjconf/201921904004  

   Plaster, B. ; Adamek, E. ; Allgeier, B. ; Anaya, J. ; Back, H.O. ; Bagdasarova, Y. ; Berguno, D.B. ; Blatnik, M. ; Boissevain, J.G. ; Bowles, T.J. ; et al ( January 2019 , EPJ Web of Conferences)

   The UCNA experiment was designed to measure the neutron β-asymmetry parameter A 0 using polarized ultracold neutrons (UCN). UCN produced via downscattering in solid deuterium were polarized via transport through a 7 T magnetic field, and then directed to a 1 T solenoidal electron spectrometer, where the decay electrons were detected in electron detector packages located on the two ends of the spectrometer. A value for A 0 was then extracted from the asymmetry in the numbers of counts in the two detector packages. We summarize all of the results from the UCNA experiment, obtained during run periods in 2007, 2008–2009, 2010, and 2011–2013, which ultimately culminated in a 0.67% precision result for A 0 . 

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2. H β and H γ Absorption-line Profile Inconsistencies in Laboratory Experiments Performed at White Dwarf Photosphere Conditions

   https://doi.org/10.3847/1538-4357/ab479d  

   Schaeuble, M.-A. ; Nagayama, T. ; Bailey, J. E. ; Gomez, T. A. ; Montgomery, M. H. ; Winget, D. E. ( November 2019 , The Astrophysical Journal)
3. The Sloan Digital Sky Survey Reverberation Mapping Project: H α and H β Reverberation Measurements from First-year Spectroscopy and Photometry

   https://doi.org/10.3847/1538-4357/aa98dc  

   Grier, C. J. ; Trump, J. R. ; Shen, Yue ; Horne, Keith ; Kinemuchi, Karen ; McGreer, Ian D. ; Starkey, D. A. ; Brandt, W. N. ; Hall, P. B. ; Kochanek, C. S. ; et al ( December 2017 , The Astrophysical Journal)
4. Heterobimetallic Control of Regioselectivity in Alkyne Hydrostannylation: Divergent Syntheses of α- and ( E ) - β - Vinylstannanes via Cooperative Sn–H Bond Activation

   https://doi.org/10.1021/jacs.9b00068  

   Cheng, Li-Jie ; Mankad, Neal P. ( February 2019 , Journal of the American Chemical Society)
5. Cationic Co(I) Catalysts for Regiodivergent Hydroalkenylation of 1,6-Enynes: An Uncommon cis -β-C–H Activation Leads to Z -Selective Coupling of Acrylates

   https://doi.org/10.1021/acscatal.1c02530  

   Herbort, James H. ; Lalisse, Remy F. ; Hadad, Christopher M. ; RajanBabu, T. V. ( July 2021 , ACS Catalysis)

   null (Ed.)

   ABSTRACT Two intermolecular hydroalkenylation reactions of 1,6-enynes are presented which yield substituted 5-membered carbo- and -heterocycles. This reactivity is enabled by a cationic bis-diphenylphosphinopropane (DPPP)CoI species which forms a cobaltacyclopentene intermediate by oxidative cyclization of the enyne. This key species interacts with alkenes in distinct fashion, depending on the identity of the coupling partner to give regiodivergent products. Simple alkenes undergo insertion reactions to furnish 1,3-dienes whereby one of the alkenes is tetrasubstituted. When acrylates are employed as coupling partners, the site of intermolecular C-C formation shifts from the alkyne to the alkene motif of the enyne, yield-ing Z-substituted-acrylate derivatives. Computational studies provide support for our experimental observations and show that the turnover-limiting steps in both reactions are the interactions of the alkenes with the cobaltacyclopentene intermediate via either a 1,2-insertion in the case of ethylene, or an unexpected b-C-H activation in the case of most acrylates. Thus, the H syn to the ester is activated through the coordination of the acrylate carbonyl to the cobaltacycle intermediate, which explains the uncommon Z-selectivity and regiodivergence. Variable time normalization analysis (VTNA) of the kinetic data reveals a dependance upon the concentration of cobalt, acrylate, and activator. A KIE of 2.1 was observed with methyl methacrylate in separate flask experiments, indicating that C-H cleavage is the turnover-limiting step in the catalytic cycle. Lastly, a Hammett study of aryl-substituted enynes yields a rho- value of -0.4, indicating that more electron-rich substituents accelerate the rate of the reaction. 

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