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The use of a laser to cut or drill ice has been proposed and demonstrated multiple times in previous decades as a novel, but never adopted, machining tool in glaciology and paleoclimate studies. However, with the rapid development of high power fiber-laser technology over the past few decades, it is timely to perform further studies using this new tool. An investigation is made herein on the cutting of ice using a Yb-doped fiber laser emitting at a wavelength of 1070 nm, the most extensively developed and highest power fiber laser technology, in pulsed and continuous-wave operation. Visible-light observations of clear tap water ice samples, moving at a constant velocity relative to a pulsed laser beam, demonstrate a linear relationship between the duration of a millisecond-range laser pulse and the depth of the meltwater-free cut formed in response. Thermal imaging of the irradiated face shows that peripheral heating trends linearly for pulse lengths greater than 5 ms. A comparison of pulse trains with a constant time-averaged power suggests that shorter pulses are advantageous in slot-cutting efficiency and in minimizing visible alterations in the surrounding ice. These results demonstrate the viability of powerful fiber-compatible lasers as a tool for ice sample retrieval and processing. 

Biopyrrin pigments, which result from the degradation of heme in biological settings, feature three or two pyrrole rings and characteristic pyrrolin-2-one termini. These scaffolds serve as redox-active ligands and electron reservoirs in coordination compounds. Tripyrrin-1,14-dione coordinates divalent transition metals as a dianionic ligand hosting a delocalized radical. Herein, we report the synthesis and characterization of palladium(II) and platinum(II) tripyrrindione complexes featuring a primary amine (i.e., aniline, tert-butylamine, 1,2-ethylenediamine) at the fourth coordination site within square planar geometries. Interligand hydrogen-bonding interactions are observed between the coordinated amine and the carbonyl groups on the tripyrrindione scaffold. Notably, 1,2-ethylenediamine is employed to link two Pt(II) tripyrrindione complexes. As revealed by optical absorption and electron paramagnetic resonance (EPR) spectroscopy, all resulting complexes present ligand-based radicals that are stable at room temperature and when exposed to air. Spin pairing through multicenter interactions leads to [Formula: see text]-dimerization of the tripyrrindione radicals and a decrease in the EPR signal at low temperatures. Electrochemical measurements indicate that the ligand system undergoes quasi-reversible one-electron oxidation and reduction, thus confirming the ability of tripyrrindione to form square planar complexes in three different redox states. 

We report the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ 287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The firstI-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in theR-band. There is a big change in theR–Ispectral index by 1.0 ± 0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ 287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ 287 as well as the dense monitoring sample of Krakow.

 

The tripyrrin-1,14-dione biopyrrin, which shares the scaffold of several naturally occurring heme metabolites, is a redox-active platform for metal coordination. We report the synthesis of square planar platinum( ii ) tripyrrindiones, in which the biopyrrin binds as a tridentate radical and the fourth coordination position is occupied by either aqua or tert -butyl isocyanide ligands. These complexes are stable through chromatographic purification and exposure to air. Electron paramagnetic resonance (EPR) data and density functional theory (DFT) analysis confirm that the spin density is located predominantly on the tripyrrindione ligand. Pancake bonding in solution between the Pt( ii ) tripyrrindione radicals leads to the formation of diamagnetic π dimers at low temperatures. The identity of the monodentate ligand ( i.e. , aqua vs . isocyanide) affects both the thermodynamic parameters of dimerization and the tripyrrindione-based redox processes in these complexes. Isolation and structural characterization of the oxidized complexes revealed stacking of the diamagnetic tripyrrindiones in the solid state as well as a metallophilic Pt( ii )−Pt( ii ) contact in the case of the aqua complex. Overall, the properties of Pt( ii ) tripyrrindiones, including redox potentials and intermolecular interactions in solution and in the solid state, are modulated through easily accessible changes in the redox state of the biopyrrin ligand or the nature of the monodentate ligand. 

Chemical anomalies in polar ice core records are frequently linked to volcanism; however, without the presence of (crypto)tephra particles, links to specific eruptions remain speculative. Correlating tephras yields estimates of eruption timing and potential source volcano, offers refinement of ice core chronologies, and provides insights into volcanic impacts. Here, we report on sparse rhyolitic glass shards detected in the Roosevelt Island Climate Evolution (RICE) ice core (West Antarctica), attributed to the 1.8 ka Taupō eruption (New Zealand)—one of the largest and most energetic Holocene eruptions globally. Six shards of a distinctive geochemical composition, identical within analytical uncertainties to proximal Taupō glass, are accompanied by a single shard indistinguishable from glass of the ~25.5 ka Ōruanui supereruption, also from Taupō volcano. This double fingerprint uniquely identifies the source volcano and helps link the shards to the climactic phase of the Taupō eruption. The englacial Taupō-derived glass shards coincide with a particle spike and conductivity anomaly at 278.84 m core depth, along with trachytic glass from a local Antarctic eruption of Mt. Melbourne. The assessed age of the sampled ice is 230 ± 19 CE (95% confidence), confirming that the published radiocarbon wiggle-match date of 232 ± 10 CE (2 SD) for the Taupō eruption is robust.

 

Abstract Tephra is a unique volcanic product with an unparalleled role in understanding past eruptions, long-term behavior of volcanoes, and the effects of volcanism on climate and the environment. Tephra deposits also provide spatially widespread, high-resolution time-stratigraphic markers across a range of sedimentary settings and thus are used in numerous disciplines (e.g., volcanology, climate science, archaeology). Nonetheless, the study of tephra deposits is challenged by a lack of standardization that inhibits data integration across geographic regions and disciplines. We present comprehensive recommendations for tephra data gathering and reporting that were developed by the tephra science community to guide future investigators and to ensure that sufficient data are gathered for interoperability. Recommendations include standardized field and laboratory data collection, reporting and correlation guidance. These are organized as tabulated lists of key metadata with their definition and purpose. They are system independent and usable for template, tool, and database development. This standardized framework promotes consistent documentation and archiving, fosters interdisciplinary communication, and improves effectiveness of data sharing among diverse communities of researchers.