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1. Agreement of rebound and applanation tonometry intraocular pressure measurements during atmospheric pressure change

   https://doi.org/10.1371/journal.pone.0259143  

   Vercellin, Alice Verticchio; Harris, Alon; Siesky, Brent; Zukerman, Ryan; Tanga, Lucia; Carnevale, Carmela; Scarinci, Fabio; Oddone, Francesco (October 2021, PLOS ONE)

   Grzybowski, Andrzej (Ed.)

   This study investigated the agreement of intraocular pressure measurements using rebound tonometry and applanation tonometry in response to atmospheric changes in a hyperbaric chamber. Twelve eyes of 12 healthy subjects were included in this prospective, comparative, single-masked study. Intraocular pressure measurements were performed by rebound tonometry followed by applanation tonometry in a multiplace hyperbaric chamber at 1 Bar, followed by 2, 3 and 4 Bar during compression and again at 3 and 2 Bar during decompression. Mean differences between rebound and applanation intraocular pressure measurements were 1.6, 1.7, and 2.1 mmHg at 2, 3, and 4 Bar respectively during compression and 2.6 and 2.2 mmHg at 3 and 2 Bar during decompression. Lower limits of agreement ranged from -3.7 to -5.9 mmHg and upper limits ranged from -0.3 to 1.9 mmHg. Multivariate analysis showed that the differences between rebound and applanation intraocular pressure measurements were independent of atmospheric pressure changes (p = 0.79). Intraocular pressure measured by rebound tonometry shows a systematic difference compared to intraocular measured by applanation tonometry, but this difference is not influenced by changes of atmospheric pressure up to 4 Bar in a hyperbaric chamber. Agreement in magnitude of change between devices suggests rebound tonometry is viable for assessing intraocular pressure during atmospheric changes. Future studies should be designed in consideration of expected differences in IOP values provided by the two devices. 

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2. A Chemical Pump that Generates High‐Pressure Gas by Transmitting Liquid Fuel against Pressure Gradient

   https://doi.org/10.1002/aisy.202100246  

   Kim, Junsoo; Luo, Kai; Suo, Zhigang (May 2022, Advanced Intelligent Systems)

   A pneumatic soft robot can be made autonomous by carrying a liquid chemical fuel. In the existing design, to transmit the fuel, the pressure of the fuel tank must exceed that of the actuator. Consequently, the fuel tank must be sufficiently stiff, which hardens the robot. Herein, inspired by pit membranes in trees, a chemical pump is developed, which is consisting of a nanoporous membrane between the fuel tank and the actuator, and coated with a catalyst on the side of the actuator. The fuel in the fuel tank migrates across the membrane and, on meeting the catalyst, decomposes into a pressurized gas and inflates the actuator. The chemical pump is driven by the free energy of reaction, against the difference in pressure. The pores in the membrane are large enough for the fuel molecules to migrate through, but small enough to block the pressurized gas to tunnel back. In a demonstration, the fuel tank has ambient pressure, and the actuator has a pressure of 350 kPa, comparable to the pressure in a car tire. The chemical pump enables pneumatic robots to be autonomous, powerful, and soft. 

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3. Magnetic compressibility of layered ferromagnet under pressure

   https://doi.org/10.1063/5.0253878  

   Boswell, Matt; Peng, Cheng; Bi, Wenli; Moreira_dos_Santos, Antonio_F; Xie, Weiwei (March 2025, Journal of Applied Physics)

   This study systematically investigates the magnetic properties of the layered ferromagnet MnPt5As under pressure through a combination of experimental measurements and theoretical simulations. MnPt5As exhibits a ferromagnetic transition at approximately 301 K. Neutron diffraction measurements under applied pressures up to ∼4.9 GPa were performed over a temperature range from 320 to 100 K to probe its magnetic behavior. The results confirm that the Mn atoms maintain a ferromagnetic order under applied pressures, consistent with the ambient-pressure findings. However, magnetic anisotropy is notably suppressed. To further elucidate the compressibility of magnetic anisotropy in MnPt5As, x-ray diffraction under pressure was conducted. The results reveal that the c-axis undergoes a greater and more rapid compression compared to the ab-plane, which may contribute to the observed suppression of Mn ferromagnetic ordering along the c-axis. Additionally, theoretical calculations indicate that magnetic ordering exhibits a similar pressure-induced trend under applied pressure, supporting the experimental observations. These findings offer insights into the pressure-dependent magnetic properties and anisotropy of MnPt5As, with potential implications for strain engineering in Mn-based magnetic devices. 

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4. Enhanced Néel temperature in EuSnP under pressure

   https://doi.org/10.1039/c9dt00449a  

   Gui, Xin; Finkelstein, Gregory J.; Graf, David E.; Wei, Kaya; Zhang, Dongzhou; Baumbach, Ryan E.; Dera, Przemyslaw; Xie, Weiwei (April 2019, Dalton Transactions)

   We present the combined results of single crystal X-ray diffraction, physical properties characterization, and theoretical assessment of EuSnP under high pressure. Single crystals of EuSnP prepared using Sn self-flux crystallize in the tetragonal NbCrN-type crystal structure (S.G. P 4/ nmm ) at ambient pressure. Previous studies have shown that for Eu ions, seven unpaired electrons impart a 2+ oxidation state. Assuming the oxidation states of Eu to be +2 and P to be −3, each Sn will donate one electron, with one p valence electron left for forming a weak Sn–Sn bond. According to the high-pressure single crystal X-ray diffraction measurements, no structural phase transition was observed up to ∼6.2 GPa. Temperature-dependent resistivity measurements up to 2.15 GPa on single crystals indicate that the phase-transition temperature occurring at the Néel temperature ( T N ) is significantly enhanced under high pressure. The robust crystallography and enhanced antiferromagnetic transition temperatures can be rationalized by the electronic structure calculations and chemical bonding analysis. The increasing Eu–P bonding interaction is consistent with the lattice parameter changing and enhanced T N . Moreover, the molecular orbital diagram shows that the weak Sn–Sn bond can be squeezed under pressure, acting as a compression buffer to stabilize the structure. 

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5. High-pressure minerals

   https://doi.org/10.2138/am-2019-6594  

   Tschauner, Oliver (December 2019, American Mineralogist)

   Abstract This article is dedicated to the occurrence, relevance, and structure of minerals whose formation involves high pressure. This includes minerals that occur in the interior of the Earth as well as minerals that are found in shock-metamorphized meteorites and terrestrial impactites. I discuss the chemical and physical reasons that render the definition of high-pressure minerals meaningful, in distinction from minerals that occur under surface-near conditions on Earth or at high temperatures in space or on Earth. Pressure-induced structural transformations in rock-forming minerals define the basic divisions of Earth's mantle in the upper mantle, transition zone, and lower mantle. Moreover, the solubility of minor chemical components in these minerals and the occurrence of accessory phases are influential in mixing and segregating chemical elements in Earth as an evolving planet. Brief descriptions of the currently known high-pressure minerals are presented. Over the past 10 years more high-pressure minerals have been discovered than during the previous 50 years, based on the list of minerals accepted by the IMA. The previously unexpected richness in distinct high-pressure mineral species allows for assessment of differentiation processes in the deep Earth. 

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