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Cloud processing of dimethyl sulfide production in the eastern North Atlantic marine boundary layer
Dimethyl sulfide (DMS) is the major sulfur species emitted from the ocean. The gas-phase oxidation of DMS by hydroxyl radicals proceeds through the stable, soluble intermediate hydroperoxymethyl thioformate (HPMTF), eventually forming carbonyl sulfide (OCS) and sulfur dioxide (SO.sub.2). Recent work has shown that HPMTF is efficiently lost to marine boundary layer (MBL) clouds, thus arresting OCS and SO.sub.2 production and their contributions to new-particle formation and growth events. To date, no long-term field studies exist to assess the extent to which frequent cloud processing impacts the fate of HPMTF. Here, we present 6 weeks of measurements of the cloud fraction and the marine sulfur species methanethiol, DMS, and HPMTF made at the Atmospheric Radiation Measurement (ARM) research facility on Graciosa Island, Azores, Portugal. Using an observationally constrained chemical box model, we determine that cloud loss is the dominant sink of HPMTF in this region of the MBL during the study, accounting for 79 %-91 % of HPMTF loss on average. When accounting for HPMTF uptake to clouds, we calculate campaign average reductions in DMS-derived MBL SO.sub.2 and OCS of 52 %-60 % and 80 %-92 % for the study period. Using yearly measurements of the site- and satellite-measured 3D cloud fraction and DMS climatology, we infer that HPMTF cloud loss is the dominant sink of HPMTF in the eastern North Atlantic during all seasons and occurs on timescales faster than what is prescribed in global chemical transport models. Accurately resolving this rapid loss of HPMTF to clouds has important implications for constraining drivers of MBL new-particle formation.
Journal Article
Multi-representation dynamics of SU(4) composite Higgs models: chiral limit and spectral reconstructions
We present a lattice study of the
SU
(4) gauge theory with two Dirac fermions in the fundamental and two in the two-index antisymmetric representation, a model close to a theory of partial compositeness proposed by G. Ferretti. Focus of this work are the methodologies behind the computation of the spectrum and the extrapolation of the chiral point for a theory with matter in multiple representations. While being still technical, this study provides important steps towards a non-perturbative understanding of the spectrum of theories of partial compositeness, which present a richer dynamics compared to single-representation theories. The multi-representation features are studied first in perturbation theory, and then non-perturbatively by adopting a dual outlook on lattice data through a joint analysis of time-momentum correlation functions and smeared spectral densities.
Journal Article
Factors Contributing to Lower the Biological Risk for Atlantic Salmon in Well-Boat Operations: A Qualitative Study
The Atlantic salmon aquaculture industry in Norway is frequently confronted by the biological risks associated with the transport, handling, and treatment of live fish in well-boats. The aim of this study was to collect experience-based knowledge from the aquaculture industry about well-boat operations, to make recommendations to lower the biological risk in well-boat operations. Well-boat crew, salmon farmers, fish health personnel, and workers in other relevant professions in the industry participated in semi-structured individual interviews, followed by group interviews and a survey. This study clearly revealed that even though operational/technical factors are critical for lowering the biological risk in well-boat operations, their successful implementation hinges on three fundamental human factors: (1) experienced personnel in key positions having correct focus, (2) communication, and (3) planning/risk assessment. Those factors deserve greater attention, as the present study highlights that they are not always sufficiently taken into account. An array of recommendations to lower the biological risk for Atlantic salmon in well-boat operations is identified and summarized based on the findings from the study and literature. Keywords: communication, experienced personnel, lowering of biological risk, planning, salmon aquaculture, well-boat
Journal Article
Buying a superyacht? A Monaco boat show has you covered
London bureau chief William Booth visited Monaco on Sept. 28, where the world's superyachts are bought and sold for hundreds of millions of dollars.
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