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1. Cell cycle control and environmental response by second messengers in Caulobacter crescentus

   https://doi.org/10.1186/s12859-020-03687-z  

   Xu, Chunrui ; Weston, Bronson R. ; Tyson, John J. ; Cao, Yang ( September 2020 , BMC Bioinformatics)

   null (Ed.)

   Abstract Background Second messengers, c-di-GMP and (p)ppGpp, are vital regulatory molecules in bacteria, influencing cellular processes such as biofilm formation, transcription, virulence, quorum sensing, and proliferation. While c-di-GMP and (p)ppGpp are both synthesized from GTP molecules, they play antagonistic roles in regulating the cell cycle. In C. crescentus , c-di-GMP works as a major regulator of pole morphogenesis and cell development. It inhibits cell motility and promotes S-phase entry by inhibiting the activity of the master regulator, CtrA. Intracellular (p)ppGpp accumulates under starvation, which helps bacteria to survive under stressful conditions through regulating nucleotide levels and halting proliferation. (p)ppGpp responds to nitrogen levels through RelA-SpoT homolog enzymes, detecting glutamine concentration using a nitrogen phosphotransferase system (PTS Ntr ). This work relates the guanine nucleotide-based second messenger regulatory network with the bacterial PTS Ntr system and investigates how bacteria respond to nutrient availability. Results We propose a mathematical model for the dynamics of c-di-GMP and (p)ppGpp in C. crescentus and analyze how the guanine nucleotide-based second messenger system responds to certain environmental changes communicated through the PTS Ntr system. Our mathematical model consists of seven ODEs describing the dynamics of nucleotides and PTS Ntr enzymes. Our simulations are consistent with experimental observations and suggest, among other predictions, that SpoT can effectively decrease c-di-GMP levels in response to nitrogen starvation just as well as it increases (p)ppGpp levels. Thus, the activity of SpoT (or its homologues in other bacterial species) can likely influence the cell cycle by influencing both c-di-GMP and (p)ppGpp. Conclusions In this work, we integrate current knowledge and experimental observations from the literature to formulate a novel mathematical model. We analyze the model and demonstrate how the PTS Ntr system influences (p)ppGpp, c-di-GMP, GMP and GTP concentrations. While this model does not consider all aspects of PTS Ntr signaling, such as cross-talk with the carbon PTS system, here we present our first effort to develop a model of nutrient signaling in C. crescentus . 

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2. Hecate: Abuse Reporting in Secure Messengers with Sealed Sender

   Issa, Rawane ; Alhaddad, Nicolas ; Varia, Mayank ( August 2022 , 31st USENIX Security Symposium)

   End-to-end encryption provides strong privacy protections to billions of people, but it also complicates efforts to moderate content that can seriously harm people. To address this concern, Tyagi et al. [CRYPTO 2019] introduced the concept of asymmetric message franking (AMF) so that people can report abusive content to a moderator, while otherwise retaining end-to-end privacy by default and compatibility with anonymous communication systems like Signal’s sealed sender. In this work, we provide a new construction for asymmetric message franking called Hecate that is faster, more secure, and introduces additional functionality compared to Tyagi et al. First, our construction uses fewer invocations of standardized crypto primitives and operates in the plain model. Second, on top of AMF’s accountability and deniability requirements, we also add forward and backward secrecy. Third, we combine AMF with source tracing, another approach to content moderation that has previously been considered only in the setting of non-anonymous networks. Source tracing allows for messages to be forwarded, and a report only identifies the original source who created a message. To provide anonymity for senders and forwarders, we introduce a model of AMF with preprocessing whereby every client authenticates with the moderator out-of-band to receive a token that they later consume when sending a message anonymously. 

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3. Messengers from the Early Universe: Cosmic Neutrinos and Other Light Relics

   Green, Daniel and ( May 2019 , Bulletin of the American Astronomical Society)

   The hot dense environment of the early universe is known to have produced large numbers of baryons, photons, and neutrinos. These extreme conditions may have also produced other long-lived species, including new light particles (such as axions or sterile neutrinos) or gravitational waves. The gravitational effects of any such light relics can be observed through their unique imprint in the cosmic microwave background (CMB), the large-scale structure, and the primordial light element abundances, and are important in determining the initial conditions of the universe. We argue that future cosmological observations, in particular improved maps of the CMB on small angular scales, can be orders of magnitude more sensitive for probing the thermal history of the early universe than current experiments. These observations offer a unique and broad discovery space for new physics in the dark sector and beyond, even when its effects would not be visible in terrestrial experiments or in astrophysical environments. A detection of an excess light relic abundance would be a clear indication of new physics and would provide the first direct information about the universe between the times of reheating and neutrino decoupling one second later. 

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4. Youth as Climate Change Messengers: A Picture Is Worth a Thousand Words

   https://doi.org/10.1177/10755470211044825  

   Hendrickson Lohmeier, Jill ; Thompson, Shanna Rose ; Chen, Robert F. ; Mishol, Stephen ( December 2021 , Science Communication)

   Artwork created by children can effectively communicate science content, especially for topics that are of universal concern for the public but may cause apprehension, like climate change. This commentary describes artwork from a youth art contest about climate change in which the winning art was displayed on public buses. Young artists learned about climate science while creating images that adults and youth easily engaged with in public spaces. Thus, we suggest that connecting youth with science through art, and then using youth-generated art to engage the general public in science learning can be an effective vehicle for science communication. 

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5. Messengers from the Early Universe: Cosmic Neutrinos and Other Light Relics

   Green, Daniel ; Amin, Mustafa A. ; Meyers, Joel ; Wallisch, Benjamin ; Abazajian, Kevork N. ; Abidi, Muntazir ; Adshead, Peter ; Ahmed, Zeeshan ; Ansarinejad, Behzad ; Armstrong, Robert ; et al ( March 2019 , ArXiv.org)