1. Heterogeneous Chemistry of CaCO3 Aerosols with HNO3 and HCl
Han N Huynh, V Faye McNeill J Phys Chem A. 2020 May 14;124(19):3886-3895. doi: 10.1021/acs.jpca.9b11691. Epub 2020 May 1.
Calcite (CaCO3) aerosols often serve as an idealized proxy for calcium-rich mineral dust. Their use has also previously been proposed for stratospheric solar radiation management (SSRM). Little is known about the heterogeneous chemistry of calcite aerosols with trace gases HNO3 and HCl and therefore their potential impact on stratospheric ozone (O3). Here we report the results of an experimental study of the uptake of HNO3 and HCl onto submicron CaCO3 particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO3 onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO3) termination layer was detected in the form of a HCO3- peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO3 with Ca(OH)(HCO3) to produce Ca(NO3)2, water, and CO2. HCl reacted with Ca(OH)(HCO3) to produce CaCl2 and also water and CO2. The depletion of the Ca(OH)(HCO3)/Ca(CO3) signal due to reaction with HNO3 or HCl followed pseudo-first-order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO3 was determined to be in the range of 0.013 ≤ γHNO3 ≤ 0.14, and that for HCl was 0.0011 ≤ γHCl ≤ 0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO3 aerosols was also studied in an aerosol flow tube coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γHCl was determined to be 0.013 ± 0.001. Following previous modeling studies, these results suggest that the reactions of HCl and HNO3 with calcite in the stratosphere could ameliorate the potential for stratospheric solar radiation management to lead to stratospheric ozone depletion.
2. Standardized Hybrid Closed-Loop System Reporting
Viral N Shah, Satish K Garg Diabetes Technol Ther. 2021 May;23(5):323-331. doi: 10.1089/dia.2020.0622. Epub 2020 Nov 25.
The hybrid closed-loop (HCL) system has been shown to improve glycemic control and reduce hypoglycemia. Optimization of HCL settings requires interpretation of the glucose, insulin, and factors affecting glucose such as food intake and exercise. To the best of our knowledge, there is no published guidance on the standardized reporting of HCL systems. Standardization of HCL reporting would make interpretation of data easy across different systems. We reviewed the literature on patient and provider perspectives on downloading and reporting glucose metric preferences. We also incorporated international consensus on standardized reporting for glucose metrics. We describe a single-page HCL data reporting, referred to here as "artificial pancreas (AP) Dashboard." We propose seven components in the AP Dashboard that can provide detailed information and visualization of glucose, insulin, and HCL-specific metrics. The seven components include (A) glucose metrics, (B) hypoglycemia, (C) insulin, (D) user experience, (E) hyperglycemia, (F) glucose modal-day profile, and (G) insight. A single-page report similar to an electrocardiogram can help providers and patients interpret HCL data easily and take the necessary steps to improve glycemic outcomes. We also describe the optimal sampling duration for HCL data download and color coding for visualization ease. We believe that this is a first step in creating a standardized HCL reporting, which may result in better uptake of the systems. For increased adoption, standardized reporting will require input from providers, patients, diabetes device manufacturers, and regulators.
