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1. Star cluster formation in Orion A

   https://doi.org/10.1093/pasj/psaa035  

   Lim, Wanggi; Nakamura, Fumitaka; Wu, Benjamin; Bisbas, Thomas G; Tan, Jonathan C; Chambers, Edward; Bally, John; Kong, Shuo; McGehee, Peregrine; Lis, Dariusz C; et al (May 2020, Publications of the Astronomical Society of Japan)

   null (Ed.)

   Abstract We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining the scenario of a cloud–cloud collision. We utilize the CARMA–NRO Orion survey 13CO (1–0) data to compare molecular gas to the properties of young stellar objects from the SDSS III IN-SYNC survey. We show that the increase of $$v_{\rm {}^{13}CO} - v_{\rm YSO}$$ and Σ scatter of older YSOs can be signals of cloud–cloud collision. SOFIA-upGREAT 158 μm [C ii] archival data toward the northern part of Orion A are also compared to the 13CO data to test whether the position and velocity offsets between the emission from these two transitions resemble those predicted by a cloud–cloud collision model. We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3, and OMC-4, shows qualitative agreements with the cloud–cloud collision scenario, while in one of the southern regions, NGC 1999, there is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster, L 1641 N, shows slight tendencies of cloud–cloud collision. Overall, our results support the cloud–cloud collision process as being an important mechanism for star cluster formation in Orion A. 

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2. A biophysical threshold for biofilm formation

   https://doi.org/10.7554/eLife.76380  

   Moore-Ott, Jenna A; Chiu, Selena; Amchin, Daniel B; Bhattacharjee, Tapomoy; Datta, Sujit S (June 2022, eLife)

   Bacteria are ubiquitous in our daily lives, either as motile planktonic cells or as immobilized surface-attached biofilms. These different phenotypic states play key roles in agriculture, environment, industry, and medicine; hence, it is critically important to be able to predict the conditions under which bacteria transition from one state to the other. Unfortunately, these transitions depend on a dizzyingly complex array of factors that are determined by the intrinsic properties of the individual cells as well as those of their surrounding environments, and are thus challenging to describe. To address this issue, here, we develop a generally-applicable biophysical model of the interplay between motility-mediated dispersal and biofilm formation under positive quorum sensing control. Using this model, we establish a universal rule predicting how the onset and extent of biofilm formation depend collectively on cell concentration and motility, nutrient diffusion and consumption, chemotactic sensing, and autoinducer production. Our work thus provides a key step toward quantitatively predicting and controlling biofilm formation in diverse and complex settings. 

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3. Formation of a falling particle curtain

   Vorobieff, P; Wayne, P; Reddy Lingampally, S.; Vigil, G.; Ludwigsen, J.; Freelong, D.; Truman, C.R.; Jacobs, G. (January 2020, International journal of computational methods and experimental measurements)

   Falling particle curtains are important in many engineering applications, including receivers for concentrating solar power (CSP) facilities. During the formation of such a curtain, we observe a multiphase analog of Rayleigh-Taylor instability. It was originally described in 2011 for a situation when air sparsely seeded with glycol droplets was placed above a volume of unseeded air, producing an unstably stratified average density distribution that was characterized by an effective Atwood number 0.03. In that case, the evolution of the instability was indistinguishable from single-phase Rayleigh-Taylor instability with the same Atwood number, as the presence of the droplets largely acted as an additional contribution to the mean density of the gaseous medium. Here we present experiments where the volume (and mass) fraction of the seeding particles in gas is considerably higher, and the gravity-driven flow is dominated by the particle movement. In this case, the evolution of the observed instability appears significantly different. 

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4. Nitrite Formation at a Diiron Dinitrosyl Complex

   https://doi.org/10.1021/jacs.3c05155  

   Poptic, Anna L.; Klinger, Jeffrey K.; Carter, Samantha L.; Moore, Curtis E.; Zhang, Shiyu (October 2023, Journal of the American Chemical Society)
5. Robust communication network formation: a decentralized approach

   https://doi.org/10.1186/s40649-019-0072-3  

   Diaz, Christopher; Nikolaev, Alexander; Perla, Abhinav; Veremyev, Alexander; Pasiliao, Eduardo (December 2019, Computational Social Networks)