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1. Cl-bearing fluorcalciobritholite in high-Ti basalts from Apollo 11 and 17: Implications for volatile histories of late-stage lunar magmas.

   https://doi.org/10.2138/am-2020-7180  

   Greenwood, James P.; Abe, Kenichi; McKeeby, Benjamin (February 2020, American Mineralogist)

   Abstract We report the occurrence of a previously unidentified mineral in lunar samples: a Cl-,F-,REE-rich silico-phosphate identified as Cl-bearing fluorcalciobritholite. This mineral is found in late-stage crystallization assemblages of slowly cooled high-Ti basalts 10044, 10047, 75035, and 75055. It occurs as rims on fluorapatite or as a solid-solution between fluorapatite and Cl-fluorcalciobritholite. The Cl-fluorcalciobritholite appears to be nominally anhydrous. The Cl and Fe2+ of the lunar Cl fluorcalciobritholite distinguishes it from its terrestrial analog. The textures and chemistry of the Clfluorcalciobritholite argue for growth during the last stages of igneous crystallization, rather than by later alteration/replacement by Cl-, REE-bearing metasomatic agents in the lunar crust. The igneous growth of this Cl- and F-bearing and OH-poor mineral after apatite in the samples we have studied suggests that the Lunar Apatite Paradox model (Boyce et al. 2014) may be inapplicable for high-Ti lunar magmas. This new volatile-bearing mineral has important potential as a geochemical tool for understanding Cl isotopes and REE chemistry of lunar samples. 

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2. The reactivity of experimentally reduced lunar regolith simulants: Health implications for future crewed missions to the lunar surface

   https://doi.org/10.1111/maps.14228  

   Hendrix, Donald A; Catalano, Tristan; Nekvasil, Hanna; Glotch, Timothy D; Legett, Carey; Hurowitz, Joel A (June 2024, Meteoritics & Planetary Science)

   Abstract Crewed missions to the Moon may resume as early as 2026 with NASA's Artemis III mission, and lunar dust exposure/inhalation is a potentially serious health hazard that requires detailed study. Current dust exposure limits are based on Apollo‐era samples that spent decades in long‐term storage on Earth; their diminished reactivity may lead to underestimation of potential harm that could be caused by lunar dust exposure. In particular, lunar dust contains nanophase metallic iron grains, produced by “space weathering”; the reactivity of this unique component of lunar dust is not well understood. Herein, we employ a chemical reduction technique that exposes lunar simulants to heat and hydrogen gas to produce metallic iron particles on grain surfaces. We assess the capacity of these reduced lunar simulants to generate hydroxyl radical (OH*) when immersed in deionized (DI) water, simulated lung fluid (SLF), and artificial lysosomal fluid (ALF). Lunar simulant reduction produces surface‐adhered metallic iron “blebs” that resemble nanophase metallic iron particles found in lunar dust grains. Reduced samples generate ~5–100× greater concentrations of the oxidative OH* in DI water versus non‐reduced simulants, which we attribute to metallic iron. SLF and ALF appear to reduce measured OH*. The increase in observed OH* generation for reduced simulants implies high oxidative damage upon exposure to lunar dust. Low levels of OH* measured in SLF and ALF imply potential damage to proteins or quenching of OH* generation, respectively. Reduction of lunar dust simulants provides a quick cost‐effective approach to study dusty materials analogous to authentic lunar dust. 

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3. Single-shot visualization of the optical Kerr effect, ionization, and rotational Raman effect during laser matter interactions via frequency-domain holography

   Dempsey, Dennis; Nagar, Garima; Agnes, Jack; Berger, Russell; Shim, Bonggu (June 2021, APS Division of Atomic, Molecular and Optical Physics Meeting 2021)

   We visualize the ultrafast dynamics caused by intense femtosecond laser pulses in both thin flexible glass as well as gaseous atoms and molecules using single-shot Frequency Domain Holography (FDH) [1-3]. FDH is a robust, single-shot, time-resolved visualization technique that employs chirped pulses. Femtosecond laser micromachining of glass materials relies critically on the Kerr effect and ionization, thus direct observation of their dynamics can help produce optical devices such as waveguides. For gases, single-shot visualization of laser-matter interactions will allow for a better understanding of nonlinear optical phenomena such as filamentation [4] and Raman-induced extreme spectral broadening [5]. Using FDH, we have previously observed the ionization dynamics of thin, flexible glass and measured its nonlinear index [3], and are currently investigating the ultrafast dynamics of gases under intense laser fields. [1] S. P. Le Blanc et al., Opt. Lett. 56, 764-766 (2000). [2] K. Y. Kim et al., APL, 88 4124-4126 (2002). [3] S. Huang et. al., OFC 1-3 (2014). [4] A. Couairon et al., Phys. Rep. 441, 47 (2007). [5] D. Dempsey et al. Opt. Lett. 45, 1252-1255 (2020). 

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4. An L2 to L∞ Framework for the Landau Equation

   Jinoh Kim, Yan Guo (January 2020, Peking mathematical journal)

   Consider the Landau equation with Coulomb potential in a periodic box. We develop a new L2 to L∞ framework to construct global unique solutions near Maxwellian with small L∞ norm. The first step is to establish global L2 estimates with strong velocity weight and time decay, under the assumption of L∞ bound, which is further controlled by such L2 estimates via De Giorgi’s method (Golse et al. in Ann. Sc. Norm. Super. Pisa Cl. Sci. (5) 19(1), 253–295 (2019), Imbert and Mouhot in arXiv :1505.04608 (2015)). The second step is to employ estimates in Sp spaces to control velocity derivatives to ensure uniqueness, which is based on Hölder estimates via De Giorgi’s method (Golse et al. in Ann. Sc. Norm. Super. Pisa Cl. Sci. (5) 19(1), 253–295 (2019), Golse and Vasseur in arXiv :1506.01908 (2015), Imbert and Mouhot in arXiv :1505.04608 (2015)). 

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5. The stochastic self-organization of serotonergic densities

   Janusonis, Skirmantas; Metzler, Ralf; Vojta, Thomas (July 2023, NSF CRCNS PI Meeting)

   Neural networks in adult vertebrate brains are physically embedded in meshworks of thin, functionally active axons (fibers) that originate in the brainstem. As these fibers weave through neural tissue, releasing serotonin (5-HT) with glutamate and other neurotransmitters, they produce a dense matrix macroscopically described by regional fiber densities. This matrix is fundamentally associated with neuroplasticity, with implications for mental disorders and artificial neural networks. We have recently shown that its self-organization strongly depends on the stochastic properties of single fibers and their interaction with the three-dimensional (3D) geometry of the brain. Specifically, the trajectories of individual fibers can be described as paths of reflected fractional Brownian motion (FBM) [1, 2]. We are currently using transgenic, in vitro [3], and other experimental approaches to guide further modeling efforts and to motivate the development of the FBM theory itself [4]. In a major extension of our previous studies, we used supercomputing to simulate 960 fibers in a complex, 3D-dimensional shape constructed from serial sections of the late-embryonic mouse brain (at E17.5) [5]. The fibers were modeled as paths of reflected FBM (H = 0.8) which interacted with pial and ventricular borders. The simulated densities were compared to the actual regional fiber densities in a recently published comprehensive map. Strong similarities were found in the forebrain and midbrain. This study demonstrates that regional “serotonergic” fiber densities can achieve a substantial degree of self-organization with no biological guiding signals, with implications for neurodevelopment, neuroplasticity, and brain evolution. Support: NSF-BMBF CRCNS (NSF #2112862 to SJ & TV; BMBF #STAXS to RM). References: [1] Janušonis et al. (2020) Front. Comput. Neurosci. 14: 56; [2] Vojta et al. (2020) Phys. Rev. E 102: 032108; [3] Hingorani et al. (2022) Front. Neurosci. 16: 994735; [4] Wang et al. (2023) arXiv 2303.01551; [5] Janušonis et al. (2023) bioRxiv 10.1101/2023.03.19.533385. 

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