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1. Near-Infrared Ratiometric Hemicyanine Fluorescent Probes for Monitoring Mitochondrial pH Dynamics in Live Cells during Oxidative Stress and Hypoxia

   https://doi.org/10.1021/acsomega.4c07303  

   Dwivedi, Sushil K; Arachchige, Dilka Liyana; Olowolagba, Adenike Mary; Mahmoud, Mohamed; Pandey, Subash; Vohs, Tara; Liu, Haiying; Luck, Rudy L (October 2024, ACS Omega)

   Novel near-infrared ratiometric molecules (probes A and B) produced by linking formyl-functionalized xanthene and methoxybenzene moieties, respectively, onto a xanthene-hemicyanine framework are detailed. Probe A exhibited a primary absorption peak at 780 nm and a shoulder peak at 730 nm and exhibited fluorescence at 740 nm↓ (signifies a downward shift in intensity upon acidification) in a pH 9.3 buffer and 780 nm↑ at pH 2.8 under excitation at 700 nm. Probe B featured absorptions at 618 and 668 nm at pH 3.2 and at 717 nm at pH 8.6, and fluorescence at 693 nm↑ at pH 3.2 and at 739 nm↓ at pH 8.6, in mostly the red to near-IR region. The ratiometric changes in the intensity of the fluorescent absorptions were reversed between A and B upon acidification as indicated by the arrows. Theoretical calculations confirmed that there were slight changes in conformation between probes and the protonated molecules, suggesting that the changes in emission spectra were due mostly to conjugation effects. Calculations at the APFD/6-311+g(d,p) level with a solvent described by the polarizable continuum model resulted in pKa values for A at 6.33 and B at 6.41, in good agreement with the experimentally determined value of 6.97 and an average of 6.40, respectively. The versatilities of the probes were demonstrated in various experimental contexts, including the effective detection of mitochondrial pH fluctuations. Live cell experiments involving exposure to different pH buffers in the presence of H+ ionophores, monitoring mitophagy processes during cell starvation, studying hypoxia induced by CoCl2 treatment, and investigating responses to various oxidative stresses are detailed. Our findings highlight the potential of attaching xanthene and methoxybenzaldehyde groups onto xanthene-hemicyanine structures as versatile tools for monitoring pH changes in a variety of cellular environments and processes. 

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2. Forbidden hugs in pandemic times: IV. Panchromatic evolution of three luminous red novae

   https://doi.org/10.1051/0004-6361/202244684  

   Pastorello, A.; Valerin, G.; Fraser, M.; Reguitti, A.; Elias-Rosa, N.; Filippenko, A. V.; Rojas-Bravo, C.; Tartaglia, L.; Reynolds, T. M.; Valenti, S.; et al (March 2023, Astronomy & Astrophysics)

   We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe): AT 2018bwo , AT 2021afy , and AT 2021blu . AT 2018bwo was discovered in NGC 45 (at about 6.8 Mpc) a few weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 10 40 erg s −1 . AT 2021afy , hosted by UGC 10043 (∼49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(±0.6)×10 41 erg s −1 . Finally, for AT 2021blu in UGC 5829 (∼8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of AT 2021blu was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of LRN AT 2021blu shows a double peak, with a prominent early maximum reaching a luminosity of 6.5 × 10 40 erg s −1 , which is half of that of AT 2021afy . The spectra of AT 2021afy and AT 2021blu display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of AT 2018bwo are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak, AT 2018bwo was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from about 13 M ⊙ for AT 2018bwo , to 14 −1 +4 M ⊙ for AT 2021blu , and over 40 M ⊙ for AT 2021afy . 

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3. Phase Relations of a Depleted Peridotite Fluxed by a CO ₂ ‐H ₂ O Fluid—Implications for the Stability of Partial Melts Versus Volatile‐Bearing Mineral Phases in the Cratonic Mantle

   https://doi.org/10.1029/2019JB017653  

   Saha, Sriparna; Dasgupta, Rajdeep (October 2019, Journal of Geophysical Research: Solid Earth)

   Abstract We present phase‐equilibria experiments of a K‐bearing, depleted peridotite (Mg# 92) fluxed with a mixed CO₂‐H₂O fluid (0.5 wt.% CO₂and 0.94 wt.% H₂O in the bulk) to gain insight into the stability of volatile‐bearing partial melts versus volatile‐bearing mineral phases in a depleted peridotite system. Experiments were performed at 850–1150 °C and 2–4 GPa using a piston‐cylinder and a multianvil apparatus. Olivine, orthopyroxene, clinopyroxene, and spinel/garnet are present at all experimental conditions. Textural confirmation of partial melt is made at temperatures as low as 1000 °C at 2 GPa, 950 °C at 3 GPa, and 1000 °C at 4 GPa marking the onset of melting at 900–1000 °C at 2 GPa, 850–950 °C at 3 GPa, and 950–1000 °C at 3 GPa. Phlogopite and magnesite breakdown at 900–1000 °C at 2 GPa, 950–1000 °C at 3 GPa, and 1000–1050 °C at 4 GPa. Comparison with previously published experiments in depleted peridotite system with identical CO₂‐H₂O content introduced via a silicic melt show that introduction of CO₂‐H₂O as fluid lowers the temperature of phlogopite breakdown by 150–200 °C at 2–4 GPa and stabilizes partial melts at lower temperatures. Our study thus, shows that the volatile‐bearing phase present in the cratonic mantle is controlled by bulk composition and is affected by the process of volatile addition during craton formation in a subduction zone. In addition, volatile introduction via melt versus aqueous fluid, leads to different proportion of anhydrous phases such as olivine and orthopyroxene. Considering the agent of metasomatism is thus critical to evaluate how the bulk composition of depleted peridotite is modified, leading to potential stability of volatile‐bearing phases as the cause of anomalously low shear wave velocity in mantle domains such as mid lithospheric discontinuities beneath continents. 

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4. South Pole Station Ground‐Based and Cluster Satellite Measurements of Leaked and Escaping Auroral Kilometric Radiation

   https://doi.org/10.1029/2021JA029399  

   LaBelle, James; Yearby, Keith; Pickett, Jolene S. (February 2022, Journal of Geophysical Research: Space Physics)

   Abstract Previous work suggests that Auroral Kilometric Radiation (AKR) leaks to low altitudes. To investigate this phenomenon, wideband wave measurements have been conducted simultaneously at South Pole, Antarctica, and at the Cluster satellites, during 35 intervals in 2018–2020. Leaked AKR is observed ∼5% of the time at South Pole and escaping AKR ∼31% of the time at Cluster satellites. Both types of AKR are composed of fine structure, and similar fine structure is often observed simultaneously in the AKR at the different locations. Around 0317 UT on 29 June 2020, identical features were observed simultaneously. Cluster interferometry shows that the footprint of the source field line during this event lies within a few hundred kilometers of South Pole. The estimated emitted power of the escaping AKR observed at Cluster in this event exceeds that of the leaked AKR observed at South Pole by many orders of magnitude, suggesting that mode conversion involved in generating leaked AKR is relatively inefficient. AKR fine structure which is identical at the two locations comprises ∼0.1%–0.3% of AKR observed at Cluster when the South Pole receiver operates, and ∼2% of AKR observed at South Pole when at least one Cluster satellite is tuned to the appropriate frequency range. The relatively low occurrence rates of coincident fine structure may be attributed partly to geometric and beaming considerations but also suggest that processes involved in generating leaked AKR at levels detectable at ground level have lower probability than those generating escaping AKR at levels detectable by distant spacecraft. 

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5. FOCUSING ON INDIVIDUAL WOODEN BUILDINGS REVEALS CHANGES IN THE LATE TO TERMINAL CLASSIC ECONOMY AT THE PAYNES CREEK SALT WORKS

   McKillop, Heather; Sills, E Cory (June 2023, Research Reports in Belizean Archaeology)

   Preservation of wooden building posts in red mangrove (Rhizophora mangle) peat below the sea floor at the Paynes Creek Salt Works in southern Belize provides a rare opportunity to study pole and thatch buildings that were likely the dominant construction in the Maya area in prehistory. In 2020 and 2021, when field research at the salt works was not possible due to the covid pandemic, individual wooden buildings at two of the largest sites, Ek Way Nal and Ta’ab Nuk Na, were radiocarbon dated. The dates indicate that the buildings were constructed at different times. Associated artifacts reveal both residences and salt kitchens at both sites and that production began earlier at Ta’ab Nuk Na and ended later at Ek Way Nal. Identification of tree species used in building construction at Ek Way Nal indicates the salt workers selected useful trees and did not overuse the environment. 

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