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1. Ion Diffusive Transport Across the Separatrix Between the Low‐Latitude Mantle and the Plasma Sheet by Kinetic Alfvén Waves: MMS Observation

   https://doi.org/10.1029/2024JA032719  

   Wang, Chih‐Ping; Johnson, Jay R; Xing, Xiaoyan; Avanov, Levon A; Wei, H Y; Ahmadi, Narges (October 2024, Journal of Geophysical Research: Space Physics)

   Abstract To understand the entry of the cool low‐latitude mantle ions into the tail plasma sheet near the flanks under persistent interplanetary magnetic field B_y, we evaluate the role of the cross‐field diffusive transport by kinetic Alfvén waves (KAWs) by investigating two events observed by multiscale (MMS) spacecraft. Around the separatrix between the open and closed field‐line regions, a two‐component mixing of hot plasma sheet ions of a few keV with cool mantle ions of a few hundred eV was observed, indicating transport across the separatrix. The waves observed between 0.01 and 10 Hz around the separatrix had characteristics consistent with those of KAWs. The consistency allowed us to estimate the wave vectors as a function of frequency by fitting KAW dispersion to the observations. Using the observed wave powers, plasma moments, and the estimated wave vectors, we computed the cross‐field diffusion rates associated with KAWs. The diffusion rates were found to be comparable to or larger than the Bohm diffusion rates during the intervals when the two‐component mixing was observed, indicating that the KAW diffusive transport can play a role in the entry of low‐latitude mantle ions into the plasma sheet. 

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2. Two-component relativistic equation-of-motion coupled cluster for electron ionization

   https://doi.org/10.1063/5.0248535  

   Yuwono, Stephen H; Li, Run R; Zhang, Tianyuan; Li, Xiaosong; DePrince, A Eugene (February 2025, The Journal of Chemical Physics)

   We present an implementation of the relativistic ionization-potential (IP) equation-of-motion coupled-cluster (EOMCC) with up to 3-hole–2-particle (3h2p) excitations that makes use of the molecular mean-field exact two-component framework and the full Dirac–Coulomb–Breit Hamiltonian. The closed-shell nature of the reference state in an X2C-IP-EOMCC calculation allows for accurate predictions of spin–orbit splittings in open-shell molecules without breaking degeneracies, as would occur in an excitation-energy EOMCC calculation carried out directly on an unrestricted open-shell reference. We apply X2C-IP-EOMCC to the ground and first excited states of the HCCX+ (X = Cl, Br, I) cations, where it is demonstrated that a large basis set (i.e., quadruple-zeta quality) and 3h2p correlation effects are necessary for accurate absolute energetics. The maximum error in calculated adiabatic IPs is on the order of 0.1 eV, whereas spin–orbit splittings themselves are accurate to ≈0.01 eV, as compared to experimentally obtained values. 

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3. Artificial neural network aided vapor–liquid equilibrium model for multi-component high-pressure transcritical flows with phase change

   https://doi.org/10.1063/5.0219323  

   Srinivasan, Navneeth; Yang, Suo (August 2024, Physics of Fluids)

   In this work, an artificial neural network (ANN) aided vapor–liquid equilibrium (VLE) model is developed and coupled with a fully compressible computational fluid dynamics (CFD) solver to simulate the transcritical processes occurring in high-pressure liquid-fueled propulsion systems. The ANN is trained in Python using TensorFlow, optimized for inference using Open Neural Network Exchange Runtime, and coupled with a C++ based CFD solver. This plug-and-play model/methodology can be used to convert any multi-component CFD solver to simulate transcritical processes using only open-source packages, without the need of in-house VLE model development. The solver is then used to study high-pressure transcritical shock-droplet interaction in both two- and four-component systems and a turbulent temporal mixing layer (TML), where both qualitative and quantitative agreement (maximum relative error less than 5%) is shown with respect to results based on both direct evaluation and the state-of-the-art in situ adaptive tabulation (ISAT) method. The ANN method showed a 6 times speed-up over the direct evaluation and a 2.2-time speed-up over the ISAT method for the two-component shock-droplet interaction case. The ANN method is faster than the ISAT method by 12 times for the four-component shock-droplet interaction. A 7 times speed-up is observed for the TML case for the ANN method compared to the ISAT method while achieving a data compression factor of 2881. The ANN method also shows intrinsic load balancing, unlike traditional VLE solvers. A strong parallel scalability of this ANN method with the number of processors was observed for all the three test cases. Code repository for 0D VLE solvers, and C++ ANN interface—https://github.com/UMN-CRFEL/ANN_VLE.git. 

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4. Ni- and Pd-Catalyzed Enantioselective 1,2-Dicarbofunctionalization of Alkenes

   https://doi.org/10.1055/a-2108-9549  

   Kang, Taeho; Apolinar, Omar; Engle, Keary M (December 2023, Synthesis)

   Abstract Catalytic enantioselective 1,2-dicarbofunctionalization (1,2-DCF) of alkenes is a powerful transformation of growing importance in organic synthesis for constructing chiral building blocks, bioactive molecules, and agrochemicals. Both in a two- and three-component context, this family of reactions generates densely functionalized, structurally complex products in a single step. Across several distinct mechanistic pathways at play in these transformations with nickel or palladium catalysts, stereocontrol can be obtained through tailored chiral ligands. In this Review we discuss the various strategies, mechanisms, and catalysts that have been applied to achieve enantioinduction in alkene 1,2-DCF. 1 Introduction 2 Two-Component Enantioselective 1,2-DCF via Migratory Insertion 3 Two-Component Enantioselective 1,2-DCF via Radical Capture 4 Three-Component Enantioselective 1,2-DCF via Radical Capture 5 Three-Component Enantioselective 1,2-DCF via Migratory Insertion 6 Miscellaneous Mechanisms 7 Conclusion 

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5. The unusual structural properties and potential biological relevance of switchback DNA

   https://doi.org/10.1038/s41467-024-50348-3  

   Madhanagopal, Bharath Raj; Talbot, Hannah; Rodriguez, Arlin; Louis, Jiss Maria; Zeghal, Hana; Vangaveti, Sweta; Reddy, Kaalak; Chandrasekaran, Arun Richard (December 2024, Nature Communications)

   Abstract Synthetic DNA motifs form the basis of nucleic acid nanotechnology. The biochemical and biophysical properties of these motifs determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology. 

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