Modeling the OH-Initiated Oxidation of Mercury in the Global Atmosphere Without Violating Physical Laws

In 2005, Calvert and Lindberg wrote that the use of laboratory-derived rate constants for OH + Hg(0) “…to determine the extent of Hg removal by OH in the troposphere will greatly over-estimate the importance of Hg removal by this reaction.” The HOHg• intermediate formed from OH + Hg will mostly fall apart in the atmosphere before it can react. By contrast, in laboratory experiments, Calvert and Lindberg expected HOHg• to react with radicals (whose concentrations are much higher than in the atmosphere). Yet almost all models of oxidation of Hg(0) ignore the argument of Calvert and Lindberg. We present a way for modelers to include the OH + Hg reaction while accounting quantitatively for the dissociation of HOHg•. We use high levels of quantum chemistry to establish the HO-Hg bond energy as 11.0 kcal/mole, and calculate the equilibrium constant for OH + Hg = HOHg•. Using the measured rate constant for association of OH with Hg, we determine the rate constant for HOHg• dissociation. Theory is also used to demonstrate that HOHg• forms stable compounds, HOHgY, with atmospheric radicals (Y = NO2, HOO•, CH3OO•, and BrO). We then present rate constants for use in in modeling OH-initiated oxidation of Hg(0). We use this mechanism to model the global oxidation of Hg(0) in the period 2013-2015 using the GEOS-Chem 3D model of atmospheric chemistry. Because of the rapid dissociation of HOHg•, OH accounts fo

Review of juxtaglomerular cell tumor with focus on pathobiological aspect

Juxtaglomerular cell tumor (JGCT) generally affects adolescents and young adults. The patients experience symptoms related to hypertension and hypokalemia due to renin-secretion by the tumor. Grossly, the tumor is well circumscribed with fibrous capsule and the cut surface shows yellow or gray-tan color with frequent hemorrhage. Histologically, the tumor is composed of monotonous polygonal cells with entrapped normal tubules. Immunohistochemically, tumor cells exhibit a positive reactivity for renin, vimentin and CD34. Ultrastructurally, neoplastic cells contain rhomboid-shaped renin protogranules. Genetically, losses of chromosomes 9 and 11 were frequently observed. Clinically, the majority of tumors showed a benign course, but rare tumors with vascular invasion or metastasis were reported. JGCT is a curable cause of hypertensive disease if it is discovered early and surgically removed, but may cause a fatal outcome usually by a cerebrovascular attack or may cause fetal demise in pregnancy. Additionally, pathologists and urologists need to recognize that this neoplasm in most cases pursues a benign course, but aggressive forms may develop in some cases

Persistent Luminescence Nanosensors: A Generalized Optode-based Platform for Autofluorescence-free Sensing in Biological Systems

Fluorescent nanosensors have drastically progressed our ability to accelerate diagnostics and quantify cellular dynamics in real time. Their modular assembly allows for facile sensor tuning, leading to a large expansion of analytes and systems that can be analyzed. Still, separating sensor signals from background optical signatures remains a major hurdle in the field. Exploiting this modular synthesis, we merged optode-based sensing with near-infrared emitting ZnGa2O4:Cr3+ persistent luminescence nanoparticles (PLNPs) to create functional nanocompo- sites for autofluorescence-free “glow-in-the-dark” sensing. We hydrophobically modified the PLNP surface with covalently bound ligands and incorporated the PLNPs into the polymeric core of optode-based nanoparticles. We demonstrate persistent luminescence nanosensors (PLNs) for five different analytes (K+, Na+, Ca2+, pH, and O2) based on two different sensing mechanisms. The PLNs allowed us to achieve autofluorescence-free quantification of K+ in fetal bovine serum and ratiometric metabolic monitoring of microbial samples with time-resolved luminescence acquisition. We foresee that this approach will allow for high signal-to-noise ratios while sensing in optically challenging samples