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Long-term measurements of the mass concentration of black carbon (BC) in the atmosphere (MBC) with well-constrained accuracy are indispensable to quantify its emission, transport, and deposition. The aerosol light absorption coefficient (babs), usually measured by a filter-based absorption photometer, including an Aethalometer (AE), is often used to estimate MBC. The measured babs is converted to MBC by assuming a value for the mass absorption cross section (MAC). Previously, we derived the MAC for AE (MAC (AE)) from measured babs and independently measured MBC values at two sites in the Arctic. MBC was measured with a filter-based absorption photometer with a heated inlet (COSMOS). The accuracy of the COSMOS-derived MBC (MBC (COSMOS)) was within about 15%. Here, we obtained additional MAC (AE) measurements to improve understanding of its variability and uncertainty. We measured babs (AE) and MBC (COSMOS) at Alert (2018–2020), Barrow (2012–2022), Ny-Ålesund (2012–2019), and Pallas (2019–2022). At Pallas, we also obtained four-wavelength photoacoustic aerosol absorption spectrometer (PAAS-4λ) measurements of babs. babs (AE) and MBC (COSMOS) were tightly correlated; the average MAC (AE) at the four sites was 11.4 ± 1.2 m2 g−1 (mean ± 1σ) at 590 nm and 7.76 ± 0.73 m2 g−1 at 880 nm. The spatial variability of MAC (AE) was about 11% (1σ), and its year-to-year variability was about 18%. We compared MAC (AE) in the Arctic with values at mid-latitudes, measured by previous studies, and with values obtained by using other types of filter-based absorption photometer, and PAAS-4λ. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Here, we used a modified single-particle soot photometer (SP2) coupled with a concentric pneumatic nebulizer to measure the size-resolved number and mass concentrations of light-absorbing iron oxide aerosols (FeOx) in liquid water (CNFeOx and CMFeOx, respectively). The SP2 could selectively detect individual FeOx particles in mixed wüstite–fullerene soot laboratory samples and melted Arctic snow samples. The nebulizer efficiency for FeOx particles was about 50% within the 70–650 nm diameter range, as derived from the ratio of the volume of ammonium sulfate before and after extraction by the nebulizer and the size-resolved transmission efficiency in the nebulizer–SP2 sampling line. Uncertainty from the boundary lines empirically drawn to discriminate the scatterplots of FeOx and black carbon in the mixed wüstite–fullerene soot suspensions and snow samples was approximately 3.0% and 10%, respectively. Overall uncertainty in total CNFeOx and CMFeOx (220–1400 nm) was approximately 19% and 18%, respectively. After storage at 4 °C for 16 months, the FeOx particle size distributions in melted Arctic snow had remained stable, and CNFeOx and CMFeOx had changed by less than 19% and 1.0%, on average, respectively. Most of the FeOx on dust particles measured by this system was estimated to be in the diameter range smaller than 1000 nm, considering the nebulizer efficiency for dust particles. The high accuracy of the CNFeOx and CMFeOx measurements will help to improve our quantitative understanding of the wet deposition of FeOx and provide more accurate estimates of the effects of FeOx on snow surface albedo. [ABSTRACT FROM AUTHOR]

The 2016 International Guidelines for the Management of Sepsis and Septic Shock recommend antibiotic therapy for 7–10 days for most patients with sepsis. However, evidence on critically ill patients is limited. Thus, we conducted the first systematic review and meta-analysis comparing the effectiveness and adverse events of shorter- (≤1 week) with longer-course antibiotics in adults with critical infections including sepsis. We searched the MEDLINE, Cochrane Central Register of Controlled Trials, and Igaku Chuo Zasshi databases for randomised controlled trials (RCTs) and observational studies (OSs) from inception to 31 March 2021. We included 6 of 3,766 identified articles, incorporating data from 4 RCTs and 2 OSs (1,721 patients) in meta-analyses. Three RCTs and one OS focussed on ventilator-associated pneumonia, and one RCT and one OS investigated intra-abdominal infections. The severity score levels were similar to that of sepsis, but no study comprehensively focussing on sepsis was found. There were no significant differences in mortality at a maximum follow-up of 30 days (RR 1.08, 95%CI 0.80–1.46); 28-day mortality, clinical cure, the occurrence of new events, and the emergence of resistant organisms between the groups in the RCTs. The OSs findings were consistent. The quality of evidence was assessed as very low to moderate using the GRADE approach, with no uniform description of severity scores, sepsis, or adverse events. Shorter, fixed-duration antibiotic therapy for clinically heterogeneous sepsis or severe infections was not associated with poorer outcomes, but the overall quality of evidence was poor. [ABSTRACT FROM AUTHOR]