Understanding the arrow of time across scales and complexity

Review written by Qiwei Yu (G2, Biophysics)

The stream of time flows inevitably forward and stops for no one. This one-way direction defines an “arrow of time”, which we perceive through the lens of irreversible processes that occur in both inanimate and living worlds. Irreversibility is manifested at both microscopic and macroscopic scales, ranging from the dissolution of an ink droplet in water to the concerted flight of large flocks of birds.

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Proton Outflow Associated With Jupiter’s Auroral Processes

Review written by Cecilia Panfil (CHM, 2022) and Alexandra Libby (PNI, GS)

Abstract

Despite Jupiter’s aurora being the brightest in the solar system, the mechanism of its occurrence is not well understood. One peculiar phenomenon on Jupiter is the large quantities of protons in its magnetosphere. Recently, Dr. Jamey Szalay and his team were able to use data from the Juno spaceship to observe the protons flying away from Jupiter. This provides evidence that the protons are coming from Jupiter itself. The electric fields which drive protons away from Jupiter are likely intimately related to Jupiter’s auroral fields. With their novel observation, Szalay et al. provide a clue towards Jupiter’s complex auroral interactions. 

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Topology helps slime bacteria form fruiting bodies

Review written by Qiwei Yu (G1, QCB)

Nature never ceases to amaze us, particularly when it comes to how biological organisms develop sophisticated and diverse strategies to survive dynamic and oftentimes hostile environments. Myxobacteria (also known as “slime bacteria”), for example, have evolved a specialized life cycle to cope with the possibility of unreliable nutrient supply. While nutrient abundance enables the bacteria to grow and proliferate, nutrient scarcity can conversely trigger a transition to a more dormant state. In response to nutrient depletion, myxobacteria cells can aggregate into fruiting bodies, three-dimensional multicellular structures of diverse colors and shapes. A subset of the cells within the fruiting bodies develop into rounded myxospores with thick cell walls, waiting for a more favorable environment to resume growth. It is truly amazing how the behavior of a large number of cells can be coordinated to achieve the rapid and dynamic process of fruiting body formation.

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New mathematical insights into fusion equilibria

Review written by Jaydeep Singh (MATH, G2)

Princeton scientists have long been at the forefront of research into nuclear fusion, a challenging process in which light atomic nuclei—hydrogen, for example—are chemically fused together to form heavier elements. The process releases immense amounts of energy, and is a promising approach for meeting the world’s energy needs. Early research dating from the post-war period explored designs for fusion-based weapons, but quickly interest turned to the process of harnessing fusion to generate usable electricity. Fusion research is a vast field encompassing both theoretical and experimental work, and it is not hard to see why controlled fusion remains a difficult problem after almost a century of progress: a prerequisite to achieving the fusion of light ions is the ability to super-heat the ions, in the form of a plasma, up to temperatures of 108 Kelvin within large reactors. To do this, all while maintaining the ability to confine and control the plasma, is no easy engineering feat.

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Biophysical modeling of liquid-liquid interactions helps scientists understand cell division

Review written by Alexandra Libby (PNI)

Cell division is one of the most important and well-studied biological processes. Organisms generate new cells in order to grow and reproduce (Figure 1); the types of cell division responsible for each of these goals are called mitosis and meiosis, respectively. Like many biological processes, cell division involves a well-timed, complex coordination of proteins and cellular machinery. Disrupted division can lead to a multitude of problems including genetic mutations, cell death, and cancer (Zhivotovsky and Orrenius, 2010). 

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