Search

The response of the hydrological cycle to anthropogenic climate change, especially across the tropical oceans, remains poorly understood due to the scarcity of long instrumental temperature and hydrological records. Massive shallow-water corals are ideally suited to reconstructing past oceanic variability as they are widely distributed across the tropics, rapidly deposit calcium carbonate skeletons that continuously record ambient environmental conditions, and can be sampled at monthly to annual resolution. Climate reconstructions based on corals primarily use the stable oxygen isotope composition (δ18 O), which acts as a proxy for sea surface temperature (SST), and the oxygen isotope composition of seawater (δ18 O sw), a measure of hydrological variability. Increasingly, coral δ18 O time series are paired with time series of strontium-to-calcium ratios (Sr/Ca), a proxy for SST, from the same coral to quantify temperature and δ18 O sw variability through time. To increase the utility of such reconstructions, we present the CoralHydro2k database, a compilation of published, peer-reviewed coral Sr/Ca and δ18 O records from the Common Era (CE). The database contains 54 paired Sr/Ca – δ18 O records and 125 unpaired Sr/Ca or δ18 O records, with 88 % of these records providing data coverage from 1800 CE to the present. A quality-controlled set of metadata with standardized vocabulary and units accompanies each record, informing the use of the database. The CoralHydro2k database tracks large-scale temperature and hydrological variability. As such, it is well-suited for investigations of past climate variability, comparisons with climate model simulations including isotope-enabled models, and application in paleodata-assimilation projects. The CoralHydro2k database is available in Linked Paleo Data (LiPD) format with serializations in MATLAB, R, and Python and can be downloaded from the NOAA National Center for Environmental Information's Paleoclimate Data Archive at 10.25921/yp94-v135 (Walter et al., 2022). [ABSTRACT FROM AUTHOR]

Quality in carburizing can often be enhanced by adopting the highly accurate - and much improved - multigas infrared (IR) method of carbon potential control. The theoretical benefits of using […]

Infrared atmosphere analysis/control systems based on off-the-shelf hardware have benefits in sintering and other heat processing applications. Accurate control of the entire heat treating process is needed to meet increased […]

A synthesis of [7,10-mu-H-7-CO-7, 7-(PPh3) 2-isonido-7,8,9-Re[C.sub.2][B.sub.2][H.sub.9]] complex by treatment of the complex salt [NHMe3][3,3-Cl2-3,3-([CO.sub.2])-closo-3,1,2-Re[C.sub.2][B.sub.9][H.sub.11]] with PPh3 in refluxing tetrahydrofuran and isolated as intensely colored orange-red microcrystals is described. Spectroscopic NMR and IR data suggest that the product has a highly asymmetric structure with two inequivalent PPh3 ligands and a single CO ligand.

The complex [7,10-μ-H-7-CO-7,7-(PPh3)2-isonido-7,8,9-ReC2B7H9] has been synthesized by treatment of the complex salt [NHMe3][3,3-Cl2-3,3-(CO)2-closo-3,1,2-ReC2B9H11] with PPh3 in refluxing THF (tetrahydrofuran) and isolated as intensely colored orange-red microcrystals. Spectroscopic NMR and IR data have suggested that the product has a highly asymmetric structure with two inequivalent PPh3 ligands and a single CO ligand. Measurement of 11B NMR spectra in particular have indicated seven distinct boron vertexes, although the resulting cage degradation by removal of two BH vertexes was confirmed only following X-ray crystallographic analysis, which revealed the pentadecahedral isonido-7,8,9-ReC2B7 architecture. The 11B NMR resonances span an enormous chemical shift range (Δδ = 113), and this appears to be a direct consequence of the deshielding of the boron vertex directly II opposite the quadrilateral ReCCB aperture. The new complex has been shown by electrochemical measurements to undergo a reversible one-electron oxidation. Digitally simulated cyclic voltammograms support a proposed square scheme (E1/2 = 0.58, 0.69 V vs ferrocene) involving a reversible isonido-closo transition of the metallacarborane cage. Most unusually for a metallacarborane complex, ambient temperature solutions in CH2CI2 and DMF have been shown to be intensely turquoise-blue fluorescent λem = 442 nm, Φ = 0.012). Fluorescence spectroscopy measurements in MeTHF (2-methyltetrahydrofuran) glass at 77 K have indicated that the likely cause of such a broad emission is dual fluorescence λem = 404, 505 nm), with both emissions displaying vibronic structure. Following excited-state lifetime decay analysis, the emissive behavior has been accredited to metal-perturbed ¹IL states, with the lower energy emission arising from a slight geometric distortion of the initially excited complex. [ABSTRACT FROM AUTHOR]