Characterisation and airborne deployment of a new counterflow virtual impactor inlet

A new counterflow virtual impactor (CVI) inlet is introduced with details of its design, laboratory characterisation tests and deployment on an aircraft during the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE). The CVI inlet addresses three key issues in previous designs; in particular, the inlet operates with: (i) negligible organic contamination; (ii) a significant sample flow rate to downstream instruments (∼15 l min^(−1)) that reduces the need for dilution; and (iii) a high level of accessibility to the probe interior for cleaning. Wind tunnel experiments characterised the cut size of sampled droplets and the particle size-dependent transmission efficiency in various parts of the probe. For a range of counter-flow rates and air velocities, the measured cut size was between 8.7–13.1 μm. The mean percentage error between cut size measurements and predictions from aerodynamic drag theory is 1.7%. The CVI was deployed on the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter for thirty flights during E-PEACE to study aerosol-cloud-radiation interactions off the central coast of California in July and August 2011. Results are reported to assess the performance of the inlet including comparisons of particle number concentration downstream of the CVI and cloud drop number concentration measured by two independent aircraft probes. Measurements downstream of the CVI are also examined from one representative case flight coordinated with shipboard-emitted smoke that was intercepted in cloud by the Twin Otter

Studying Public Health Law::Principles, Politics, and Populations as Patients

Public health law is firmly establishing itself as a crucial area of scholarly inquiry. Its vital importance has been sharply underscored following the outbreak of COVID-19, in response to which we have seen the institution of extreme legal measures—suchas the UK’s Coronavirus Act 2020—in efforts to control and contain the spread ofthe disease. The pandemic has also starkly exposed the complex nature of the regulatory challenges, nationally, internationally, and globally, to which such public health problems give rise. In approaching these, and other questions concerning the public’s health, such as non-communicable disease, public health law, as a field, brings notable distinctive features: these include a practical focus on populations, institutions, the prevention of ill health, protection of good health, and thepromotion of positive states of well-being; and concomitant critical approaches rooted in theories of social justice as contrasted with more narrow biomedical ethics. Such features make it in some senses atypical territory within the field of health law. Furthermore, the inherent role of political institutions places law conceptually within public health in a way that may be seen as distinguishable from law’s relationship with clinical medicine. This chapter explains how the broad reach and distinct features of public health require a commensurately broad approach to conceptualising public health law, and how distinct practical and theoretical features may be integrated into academic public health law. It also shows how public health law, with its distinct conceptualisations concerning ‘the body’ of medical jurisprudence, can both challenge and enrich medico-legal studies, and bring important perspectives within the broader field of health law

From best interest to better interests? Values, unwisdom, and objectivity in mental capacity law

The Mental Capacity Act 2005 governs personal decision-makingfor adults. It incorporates five overarching principles, including that incapacity may not be inferredmerelyfrom a person’s unwise decisions, andthat where a person lackscapacity decisions must be made in her best interests. Through analysis of judicial treatment of unwisdom, best interests, subjectivity, and objectivity, considered against Parliamentary debates on the Mental Capacity Bill and philosophical critique of ideas of (un)wisdom, we argue that these principles are problematically irreconcilable. The Act’s radical under-specificity means, paradoxically, that these come to be resolved through abstracted values, rather than the centricity of the person herself

Vapor wall deposition in Teflon chambers

Teflon chambers are ubiquitous in studies of atmospheric chemistry. Secondary organic aerosol (SOA) formation can be underestimated, owing to deposition of SOA-forming vapors to the chamber wall. We present here an experimental protocol and a model framework to constrain the vapor–wall interactions in Teflon chambers. We measured the wall deposition rates of 25 oxidized organic compounds generated from the photooxidation of isoprene, toluene, α-pinene, and dodecane in two chambers that had been extensively used and in two new unused chambers. We found that the extent of prior use of the chamber did not significantly affect the sorption behavior of the Teflon films. Among the 25 compounds studied, the maximum wall deposition rate is exhibited by the most highly oxygenated and least volatile compounds. By optimizing the model output to the observed vapor decay profiles, we identified that the dominant parameter governing the extent of wall deposition of a compound is its wall accommodation coefficient (α_(wi)), which can be correlated through its volatility with the number of carbons and oxygens in the molecule. By doing so, the wall-induced deposition rate of intermediate/semi-volatile organic vapors can be reasonably predicted based on their molecular constituency. The extent to which vapor wall deposition impacts measured SOA yields depends on the competition between uptake of organic vapors by suspended particles and the chamber wall. The timescale associated with vapor wall deposition can vary from minutes to hours depending on the value of α_(w,i). For volatile and intermediate volatility organic compounds (small α_(w,i)), gas-particle partitioning will dominate wall deposition for typical particle number concentrations in chamber experiments. For compounds characterized by relatively large α_(w,i), vapor transport to particles is suppressed by competition with the chamber wall even with perfect particle accommodation

Observed aerosol effects on marine cloud nucleation and supersaturation

Aerosol particles in the marine boundary layer include primary organic and salt particles from sea spray and combustion-derived particles from ships and coastal cities. These particle types serve as nuclei for marine cloud droplet activation, although the particles that activate depend on the particle size and composition as well as the supersaturation that results from cloud updraft velocities. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) 2011 was a targeted aircraft campaign to assess how different particle types nucleate cloud droplets. As part of E-PEACE 2011, we studied the role of marine particles as cloud droplet nuclei and used emitted particle sources to separate particle-induced feedbacks from dynamical variability. The emitted particle sources included shipboard smoke-generated particles with 0.05-1 μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke) and combustion particles from container ships with 0.05-0.2 μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components) [1]. Three central aspects of the collaborative E-PEACE results are: (1) the size and chemical composition of the emitted smoke particles compared to ship-track-forming cargo ship emissions as well as background marine particles, with particular attention to the role of organic particles, (2) the characteristics of cloud track formation for smoke and cargo ships, as well as the role of multi-layered low clouds, and (3) the implications of these findings for quantifying aerosol indirect effects. For comparison with the E-PEACE results, the preliminary results of the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) 2012 provided evidence of the cloud-nucleating roles of both marine organic particles and coastal urban pollution, with simultaneous measurements of the effective supersaturations of the clouds in the California coastal region

Observations of continental biogenic impacts on marine aerosol and clouds off the coast of California

During the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and 2013 Nucleation in California Experiment (NiCE) field campaigns, a predominantly organic aerosol (> 85% by mass) was observed in the free troposphere over marine stratocumulus off the coast of California. These particles originated from a densely forested region in the Northwestern United States. The organic mass spectrum resolved by positive matrix factorization is consistent with the mass spectra of previously measured biogenic organic aerosol. Particulate organic mass exhibits a latitudinal gradient that corresponds to the geographical distribution of vegetation density and composition, with the highest concentration over regions impacted by densely populated monoterpene sources. Due to meteorological conditions during summer months, cloud-clearing events transport aerosol from the Northwestern United States into the free troposphere above marine stratocumulus. Based on the variation of meteorological variables with altitude, dry air containing enhanced biogenic organic aerosol is shown to entrain into the marine boundary layer. Fresh impacts on cloud water composition are observed north of San Francisco, CA which is consistent with fresh continental impacts on the marine atmosphere at higher latitudes. Continental aerosol size distributions are bimodal. Particles in the 100 nm mode are impacted by biogenic sources, while particles in the ∼ 30 nm mode may originate from fresh biogenic emissions. Continental aerosol in the 100 nm mode is cloud condensation nuclei active and may play a role in modulating marine stratocumulus microphysics