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  1. Abstract

    A dust nucleating agent may be present in interstellar or circumstellar media that has gone seemingly undetected and unstudied for decades. Some analyses of the Murchison CM2 meteorite suggest that at least some of the aluminum present within condensed as aluminum nitrides instead of the long-studied, but heretofore undetected suite of aluminum oxides. The present theoretical study utilizes explicitly correlated coupled cluster theory and density functional theory to provide a formation pathway from alane (AlH3) and ammonia to the cyclic structure Al2N2H4, which has the proper Al/N ratio expected of bulk aluminum nitrides. Novel rovibrational spectroscopic constants are computed for alane and the first two formed structures, AlNH6and AlNH4, along the reaction pathway for use as reference in possible laboratory or observational studies. Theν8bending frequency for AlNH6at 755.7 cm−1(13.23μm) presents a vibrational transition intensity of 515 km mol−1, more intense than the antisymmetric C−O stretch of carbon dioxide, and contains a dipole moment of 5.40 D, which is ∼3× larger than that of water. Thus, the present reaction pathway and rovibrational spectroscopic analysis may potentially assist in the astrophysical detection of novel, inorganic species which may be indicative of larger dust grain nucleation.

     
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  2. Undergraduate research experiences (UREs) have been shown to improve both persistence and graduation rates for women and students of color (Alquicira et al. 2022). Although these effects are observed broadly across higher education, they are especially pronounced in the context of the STEM fields (National Academies of Sciences, Engineering, and Medicine 2017). Although community colleges disproportionately enroll students who can most benefit from UREs, structural barriers make UREs rare at community colleges (Hewlett 2018). This change project, based at a mid-sized community college in Washington State, is part of the state’s Consortium for Undergraduate Research and Equity (CURE) and aspires to address the paucity of community college research opportunities in STEM through the design and implementation of a year-long research project for students enrolled in the primary course sequence for biology majors (approximately 50-100 annually). The project’s underlying theory of change is twofold. First, two local community partners and four science faculty use backward design to create a research project that embeds laboratory skills and learning outcomes in a year-long URE. Second, participating faculty replace the entire lab curriculum in the college’s three-course biology sequence with this applied year-long research project. Incorporating applied research into the college’s biology curriculum demystifies and democratizes inquiry-based research for first-generation, underrepresented, and/or academically underprepared students, who also may not have the financial privilege to participate in an unpaid internship that affords them such an experience. Preliminary findings from this change initiative will focus on project goals related to creating equitable access across a range of outcomes including demographic participation rates, the development of professional STEM research skills, and the extent to which UREs enhance a community college student’s sense of belonging among a larger scientific community. 
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  3. Rovibrational spectral data for several tetra-atomic silicon carbide clusters (TASCCs) are computed in this work using a CCSD(T)-F12b/cc-pCVTZ-F12 quartic force field. Accurate theoretical spectroscopic data may facilitate the observation of TASCCs in the interstellar medium which may lead to a more complete understanding of how the smallest silicon carbide (SiC) solids are formed. Such processes are essential for understanding SiC dust grain formation. Due to SiC dust prevalence in the interstellar medium, this may also shed light on subsequent planetary formation. Rhomboidal Si2C2is shown here to have a notably intense (247 km mol−1) anharmonic vibrational frequency at 988.1 cm−1(10.1 μm) forν2, falling into one of the spectral emission features typically associated with unknown infrared bands of various astronomical regions. Notable intensities are also present for several of the computed anharmonic vibrational frequencies including the cyclic forms of C4, SiC3, Si3C, and Si4. These features in the 6–10 μm range are natural targets for infrared observation with theJames Webb Space Telescope(JWST)’s MIRI instrument. Additionally,t-Si2C2,d-Si3C, andr-SiC3each possess dipole moments of greater than 2.0 D making them interesting targets for radioastronomical searches especially sinced-SiC3is already known in astrophysical media.

     
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  4. It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous, asymmetric, weakly magnetized, laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism, provided the magnetic Reynolds number of the plasma is sufficiently large. In this paper, we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator. We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic, x-ray self-emission imaging, and proton radiography. The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment. Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field, the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable. We conclude that, for turbulent laser-plasmas with supercritical magnetic Reynolds numbers, the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma, a finding consistent with theoretical expectations and simulations of turbulent dynamos. 
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  5. It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous, asymmetric, weakly magnetized, laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism, provided the magnetic Reynolds number of the plasma is sufficiently large. In this paper, we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator. We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic, x-ray selfemission imaging, and proton radiography. The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment. Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field, the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable. We conclude that, for turbulent laser-plasmas with supercritical magnetic Reynolds numbers, the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma, a finding consistent with theoretical expectations and simulations of turbulent dynamos. https://doi.org/10.1063/5.0084345 
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  6. Palmer SSSA 2019 
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