7 research outputs found
Glycolaldehyde Monomer and Oligomer Equilibra in Aqueous Solution: Comparing Computational Chemistry and NMR Data
A computational protocol utilizing density functional theory calculations, including Poisson–Boltzmann implicit solvent and free energy corrections, is applied to study the thermodynamic and kinetic energy landscape of glycolaldehyde in solution. Comparison is made to NMR measurements of dissolved glycolaldehyde, where the initial dimeric ring structure interconverts among several species before reaching equilibrium where the hydrated monomer is dominant. There is good agreement between computation and experiment for the concentrations of all species in solution at equilibrium, that is, the calculated relative free energies represent the system well. There is also relatively good agreement between the calculated activation barriers and the estimated rate constants for the hydration reaction. The computational approach also predicted that two of the trimers would have a small but appreciable equilibrium concentration (\u3e0.005 M), and this was confirmed by NMR measurements. Our results suggest that while our computational protocol is reasonable and may be applied to quickly map the energy landscape of more complex reactions, knowledge of the caveats and potential errors in this approach need to be taken into account
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Self-financed marine protected areas
Marine protected areas (MPAs) are an important tool for conservation but can be victims of their own success—higher fish biomass within MPAs create incentives to poach. This insight underpins the finding that fishing persists in most MPAs worldwide, and it raises questions about MPA monitoring and enforcement. We propose a novel institution to enhance MPA design—a ‘Conservation Finance Area (CFA)’—that utilizes leased fishing zones inside of MPAs, fed by spillover, to finance monitoring and enforcement and achieve greater conservation success. Using a bioeconomic model we show that CFAs can fully finance enforcement, deter illegal fishing, and ultimately maximize fish biomass. Moreover, we show that unless a large, exogenous, and perpetual enforcement budget is available, implementing a CFA in a no-take MPA would always result in higher biomass than without. We also explore real-world enabling conditions, providing a plausible funding pathway to improve outcomes for existing and future MPAs
Glycolaldehyde Monomer and Oligomer Equilibria in Aqueous Solution: Comparing Computational Chemistry and NMR Data
A computational
protocol utilizing density functional theory calculations,
including Poisson–Boltzmann implicit solvent and free energy
corrections, is applied to study the thermodynamic and kinetic energy
landscape of glycolaldehyde in solution. Comparison is made to NMR
measurements of dissolved glycolaldehyde, where the initial dimeric
ring structure interconverts among several species before reaching
equilibrium where the hydrated monomer is dominant. There is good
agreement between computation and experiment for the concentrations
of all species in solution at equilibrium, that is, the calculated
relative free energies represent the system well. There is also relatively
good agreement between the calculated activation barriers and the
estimated rate constants for the hydration reaction. The computational
approach also predicted that two of the trimers would have a small
but appreciable equilibrium concentration (>0.005 M), and this
was
confirmed by NMR measurements. Our results suggest that while our
computational protocol is reasonable and may be applied to quickly
map the energy landscape of more complex reactions, knowledge of the
caveats and potential errors in this approach need to be taken into
account
Secondary Organic Aerosol Formation During Evaporation of Droplets Containing Atmospheric Aldehydes, Amines, and Ammounium Sulfate
Reactions of carbonyl compounds in cloudwater produce organic aerosol mass through in-cloud oxidation and during postcloud evaporation. In this work, postcloud evaporation was simulated in laboratory experiments on evaporating droplets that contain mixtures of common atmospheric aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol diameters were measured during monodisperse droplet drying experiments and during polydisperse droplet equilibration experiments at 75% relative humidity, and condensed-phase mass was measured in bulk thermogravimetric experiments. The evaporation of water from a droplet was found to trigger aldehyde reactions that increased residual particle volumes by a similar extent in room-temperature experiments, regardless of whether AS, methylamine, or glycine was present. The production of organic aerosol volume was highest from droplets containing glyoxal, followed by similar production from methylglyoxal or hydroxyacetone. Significant organic aerosol production was observed for glycolaldehyde, acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric experiments. In many experiments, the amount of aerosol produced was greater than the sum of all solutes plus nonvolatile solvent impurities, indicating the additional presence of trapped water, likely caused by increasing aerosol-phase viscosity due to oligomer formation
Secondary Organic Aerosol Formation during Evaporation of Droplets Containing Atmospheric Aldehydes, Amines, and Ammonium Sulfate
Reactions of carbonyl compounds in
cloudwater produce organic aerosol
mass through in-cloud oxidation and during postcloud evaporation.
In this work, postcloud evaporation was simulated in laboratory experiments
on evaporating droplets that contain mixtures of common atmospheric
aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol
diameters were measured during monodisperse droplet drying experiments
and during polydisperse droplet equilibration experiments at 75% relative
humidity, and condensed-phase mass was measured in bulk thermogravimetric
experiments. The evaporation of water from a droplet was found to
trigger aldehyde reactions that increased residual particle volumes
by a similar extent in room-temperature experiments, regardless of
whether AS, methylamine, or glycine was present. The production of
organic aerosol volume was highest from droplets containing glyoxal,
followed by similar production from methylglyoxal or hydroxyacetone.
Significant organic aerosol production was observed for glycolaldehyde,
acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric
experiments. In many experiments, the amount of aerosol produced was
greater than the sum of all solutes plus nonvolatile solvent impurities,
indicating the additional presence of trapped water, likely caused
by increasing aerosol-phase viscosity due to oligomer formation
WTO must ban harmful fisheries subsidies
Sustainably managed wild fisheries support food and nutritional security, livelihoods, and cultures (1). Harmful fisheries subsidies—government payments that incentivize overcapacity and lead to overfishing—undermine these benefits yet are increasing globally (2). World Trade Organization (WTO) members have a unique opportunity at their ministerial meeting in November to reach an agreement that eliminates harmful subsidies (3). We—a group of scientists spanning 46 countries and 6 continents—urge the WTO to make this commitment..