Multivariate relative rate measurements of reactions between volatile organic compounds (VOCs) and atmospheric radicals

Knowledge of the reactions between VOCs and atmospheric radicals and oxidants is fundamental to understanding atmospheric chemistry and the formation of air pollution in urban environments. This work describes the development of a new experimental technique for the simultaneous measurement of gas-phase rate coefficients for reactions between multiple VOCs and different atmospheric radicals. The technique is based on the traditional relative rate approach and succeeds in markedly increasing the rate of throughput of target reactions; an improvement necessary when considering the vast number of organic compounds observed in the atmosphere for which experimental oxidation data are not available. New rate coefficients are derived using a suite of the available kinetic literature as reference reactions to calibrate the results over a range of reactivity, thereby reducing the reliance on any single rate coefficient value. This new multivariate method was applied to mixtures containing multiple VOCs with a range in functionalities and under different experimental conditions. Two different atmospherically relevant radicals were tested (OH and Cl) and the technique was adapted to allow for temperature controlled measurements. Rate coefficients for the reactions of eight VOCs (1,2-, 1,3- and 1,4-diethylbenzene, n-pentylbenzene, 2-methylheptane, 2-methylnonane, ethylcyclohexane and 2,3-dimethylpent-1-ene) with OH at room temperature were derived for the first time. Rate coefficients for the reactions of 44 other VOCs with OH were also assessed concurrently with the derivation of these eight new results. A rate coefficient for the reaction between 2-methylheptane and Cl was measured for the first time, alongside the measurement of rate coefficients for the reactions of seven other VOCs with Cl

Methods for quantifying methane emissions using unmanned aerial vehicles: a review

From The Royal Society via Jisc Publications RouterHistory: accepted 2021-05-12, pub-electronic 2021-09-27, pub-print 2021-11-15Article version: VoRPublication status: PublishedFunder: Natural Environment Research Council; Id: http://dx.doi.org/10.13039/501100000270; Grant(s): NE/N015835/1, NE/P003737/1, NE/R01809X/1Methane is an important greenhouse gas, emissions of which have vital consequences for global climate change. Understanding and quantifying the sources (and sinks) of atmospheric methane is integral for climate change mitigation and emission reduction strategies, such as those outlined in the 2015 UN Paris Agreement on Climate Change. There are ongoing international efforts to constrain the global methane budget, using a wide variety of measurement platforms across a range of spatial and temporal scales. The advancements in unmanned aerial vehicle (UAV) technology over the past decade have opened up a new avenue for methane emission quantification. UAVs can be uniquely equipped to monitor natural and anthropogenic emissions at local scales, displaying clear advantages in versatility and manoeuvrability relative to other platforms. Their use is not without challenge, however: further miniaturization of high-performance methane instrumentation is needed to fully use the benefits UAVs afford. Developments in the models used to simulate atmospheric transport and dispersion across small, local scales are also crucial to improved flux accuracy and precision. This paper aims to provide an overview of currently available UAV-based technologies and sampling methodologies which can be used to quantify methane emission fluxes at local scales. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'

Space Mobile Network (SMN) User Demonstration Satellite (SUDS) for a Practical On-Orbit Demonstration of User Initiated Services (UIS)

This paper will discuss the various aspects of implementation of the Space Mobile Network (SMN) architecture framework within the context of operations of various nodes equipped with the User Initiated Services (UIS) protocol. These aspects include development of a Client-Server architecture in which space based Clients can create links with ground based Servers to negotiate passes with ground stations or contacts with the Tracking and Data Relay Satellite (TDRS) fleet. A key feature of this concept is that Users may require a mix of low data rate continuous contacts with one or more of the TDRS fleet and sporadic contacts with ground stations as passes become available. SUDS (SMN User Demonstration Satellite) will have the availability of TDRS contacts, the U.S. Naval Academy's ground station, NASA Near Earth Network ground sites and others. This mode of operations must be integrated within the traditional mode of scheduling contacts and passes. Thus, SUDS fits into a heterogeneous network operations concept of operations

A case study application of machine-learning for the detection of greenhouse gas emission sources

Conclusively linking local, episodic enhancements in greenhouse gas concentrations to a specific emission source can be challenging, particularly when faced with multiple proximal sources of emissions and variable meteorology, and in the absence of co-emitted tracer gases. This study demonstrates and evaluates the efficacy of using machine-learning tools to detect episodic emissions of methane (CH4) from a shale gas extraction facility in Lancashire (United Kingdom). Two machine-learning tools (rmweather and Prophet) were trained using a two-year climatological baseline dataset collected prior to gas extraction operations at the facility. The baseline dataset consisted of high-precision trace gas concentrations and meteorological data, sampled at 1 Hz continuously between 2016 and 2019. The models showed good overall predictive capacity for baseline CH4 concentrations, with R2 values of 0.85 and 0.76 under optimised training conditions for rmweather and Prophet, respectively. CH4 concentrations were then forecast for an 18-month period from the onset of operations at the shale gas facility (in 2018). Forecast values were compared with true measurements to detect anomalous deviations that may indicate the presence of new emission events associated with the operational facility. Both models successfully detected two periods in which CH4 emissions were known to have occurred (December 2018 and January 2019) via anomalous deviations between modelled and measured concentrations. This work demonstrates the application of machine-learning models for the detection of CH4 emission events from newly built industrial sources, when used in combination with real-time atmospheric monitoring and a baseline dataset collected prior to installation

Possible origins of macroscopic left-right asymmetry in organisms

I consider the microscopic mechanisms by which a particular left-right (L/R) asymmetry is generated at the organism level from the microscopic handedness of cytoskeletal molecules. In light of a fundamental symmetry principle, the typical pattern-formation mechanisms of diffusion plus regulation cannot implement the "right-hand rule"; at the microscopic level, the cell's cytoskeleton of chiral filaments seems always to be involved, usually in collective states driven by polymerization forces or molecular motors. It seems particularly easy for handedness to emerge in a shear or rotation in the background of an effectively two-dimensional system, such as the cell membrane or a layer of cells, as this requires no pre-existing axis apart from the layer normal. I detail a scenario involving actin/myosin layers in snails and in C. elegans, and also one about the microtubule layer in plant cells. I also survey the other examples that I am aware of, such as the emergence of handedness such as the emergence of handedness in neurons, in eukaryote cell motility, and in non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue. Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec

‘Sell[ing] what hasn’t got a name’: An exploration of the different understandings and definitions of ‘community engagement’ work in the performing arts

Widely known to promote broader involvement in the processes which define the arts and culture (Webster, 1997), community engagement work in the performing arts — despite employing a set of commonly recognised norms — has tended to be conceptualised differently both historically and contemporarily. Drawing on ethnographic research — particularly semi-structured qualitative interview accounts of numerous British practitioners with a track record of work in the sector, the article explores these different conceptualisations. The article finds that it is the actual ‘work that matters’ and not what it is named, and that the diversity of understandings and definitions among sectoral practitioners is reflective of evolving thinking, values and practice, something that may be destabilising for better or worse

Is early center-based child care associated with tantrums and unmanageable behavior over time up to school entry?

Background. Existing research suggests that there is a relationship between greater exposure to center-based child care and child behavioral problems though the mechanism for the impact is unclear. However the measure used to document child care has usually been average hours, which may be particularly unreliable in the early months when fewer children are in center care. In addition individual trajectories for behavior difficulties have not been studied. Objective. The purpose of the current study was to examine whether the extent of exposure to center-based child care before two years predicted the trajectory of children’s difficult behavior (i.e., tantrums and unmanageable behavior) from 30 to 51 months controlling for child and maternal characteristics. Method. Data were drawn from UK-based Families, Children and Child Care (FCCC) study (n=1201). Individual growth models were fitted to test the relation between early center-based child care experiences and subsequent difficult behavior. Results. Children with more exposure to center-based care before two had less difficult behavior at 30 months, but more increase over time. Initial levels were predicted by higher difficult temperament and lower verbal ability. Higher difficult temperament and lower family socio-economic status predicted its change over time. Conclusion. Findings suggest that early exposure to center-based care before two years old is a risk factor for subsequent behavior problems especially when children have a longer period of exposure. A possible explanatory process is that child coping strategies to manage frustration are less well developed in a group context, especially when they lag behind in expressive language

The Expression and Localization of N-Myc Downstream-Regulated Gene 1 in Human Trophoblasts

The protein N-Myc downstream-regulated gene 1 (NDRG1) is implicated in the regulation of cell proliferation, differentiation, and cellular stress response. NDRG1 is expressed in primary human trophoblasts, where it promotes cell viability and resistance to hypoxic injury. The mechanism of action of NDRG1 remains unknown. To gain further insight into the intracellular action of NDRG1, we analyzed the expression pattern and cellular localization of endogenous NDRG1 and transfected Myc-tagged NDRG1 in human trophoblasts exposed to diverse injuries. In standard conditions, NDRG1 was diffusely expressed in the cytoplasm at a low level. Hypoxia or the hypoxia mimetic cobalt chloride, but not serum deprivation, ultraviolet (UV) light, or ionizing radiation, induced the expression of NDRG1 in human trophoblasts and the redistribution of NDRG1 into the nucleus and cytoplasmic membranes associated with the endoplasmic reticulum (ER) and microtubules. Mutation of the phosphopantetheine attachment site (PPAS) within NDRG1 abrogated this pattern of redistribution. Our results shed new light on the impact of cell injury on NDRG1 expression patterns, and suggest that the PPAS domain plays a key role in NDRG1's subcellular distribution. © 2013 Shi et al