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1. The role of water mobility on water-responsive actuation of silk

   https://doi.org/10.1038/s41467-024-52715-6  

   Podbevšek, Darjan; Jung, Yeojin; Khan, Maheen_K; Yu, Honghui; Tu, Raymond_S; Chen, Xi (September 2024, Nature Communications)

   Abstract Biological water-responsive materials that deform with changes in relative humidity have recently demonstrated record-high actuation energy densities, showing promise as high-performance actuators for various engineering applications. However, there is a lack of theories capable of explaining or predicting the stress generated during water-responsiveness. Here, we show that the nanoscale confinement of water dominates the macroscopic dehydration-induced stress of the regenerated silk fibroin. We modified silk fibroin’s secondary structure, which leads to various distributions of bulk-like mobile and tightly bound water populations. Interestingly, despite these structure variations, all silk samples start to exert force when the bound-to-mobile (B/M) ratio of confined water reaches the same level. This critical B/M water ratio suggests a common threshold above which the chemical potential of water instigates the actuation. Our findings serve as guidelines for predicting and engineering silk’s WR behavior and suggest the potential of describing the WR behavior of biopolymers through confined water. 

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2. Vibrational predissociation of the phenol–water dimer: a view from the water

   https://doi.org/10.1039/C8CP06581K  

   Kwasniewski, Daniel; Butler, Mitchell; Reisler, Hanna (January 2019, Physical Chemistry Chemical Physics)

   The vibrational predissociation (VP) dynamics of the phenol–water (PhOH–H 2 O) dimer were studied by detecting H 2 O fragments and using velocity map imaging (VMI) to infer the internal energy distributions of PhOH cofragments, pair-correlated with selected rotational levels of the H 2 O fragments. Following infrared (IR) laser excitation of the hydrogen-bonded OH stretch fundamental of PhOH (Pathway 1) or the asymmetric OH stretch localized on H 2 O (Pathway 2), dissociation to H 2 O + PhOH was observed. H 2 O fragments were monitored state-selectively by using 2+1 Resonance-Enhanced Multiphoton Ionization (REMPI) combined with time-of-flight mass spectrometry (TOF-MS). VMI of H 2 O in selected rotational levels was used to derive center-of-mass (c.m.) translational energy ( E T ) distributions. The pair-correlated internal energy distributions of the PhOH cofragments derived via Pathway 1 were well described by a statistical prior distribution. On the other hand, the corresponding distributions obtained via Pathway 2 show a propensity to populate higher-energy rovibrational levels of PhOH than expected from a statistical distribution and agree better with an energy-gap model. The REMPI spectra of the H 2 O fragments from both pathways could be fit by Boltzmann plots truncated at the maximum allowed energy, with a higher temperature for Pathway 2 than that for Pathway 1. We conclude that the VP dynamics depends on the OH stretch level initially excited. 

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3. The economic anthropology of water

   https://doi.org/10.1002/sea2.12153  

   Wutich, Amber; Beresford, Melissa (June 2019, Economic Anthropology)
4. The future of piped water

   https://doi.org/10.1080/02508060.2021.1995169  

   Milman, Anita; Kumpel, Emily; Lane, Kaycie (November 2021, Water International)
5. The Water Footprint of the United States

   https://doi.org/10.3390/w12113286  

   Konar, Megan; Marston, Landon (November 2020, Water)

   null (Ed.)

   This paper commemorates the influence of Arjen Y. Hoekstra on water footprint research of the United States. It is part of the Special Issue “In Memory of Prof. Arjen Y. Hoekstra”. Arjen Y. Hoekstra both inspired and enabled a community of scholars to work on understanding the water footprint of the United States. He did this by comprehensively establishing the terminology and methodology that serves as the foundation for water footprint research. His work on the water footprint of humanity at the global scale highlighted the key role of a few nations in the global water footprint of production, consumption, and virtual water trade. This research inspired water scholars to focus on the United States by highlighting its key role amongst world nations. Importantly, he enabled the research of many others by making water footprint estimates freely available. We review the state of the literature on water footprints of the United States, including its water footprint of production, consumption, and virtual water flows. Additionally, we highlight metrics that have been developed to assess the vulnerability, resiliency, sustainability, and equity of sub-national water footprints and domestic virtual water flows. We highlight opportunities for future research. 

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