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1. Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters

   https://doi.org/10.3390/environments7090065  

   Heltzel, Robert S.; Zaki, Mohammed T.; Gebreslase, Aron K.; Abdul-Aziz, Omar I.; Johnson, Derek R. (September 2020, Environments)

   null (Ed.)

   Other test method (OTM) 33A has been used to quantify emissions from natural gas sites since it was introduced by the Environmental Protection Agency (EPA). The method relies on point source Gaussian (PSG) assumptions to estimate emissions rates from a targeted site or source. However, the method often results in low accuracy (typically ±70%, even under conducive conditions). These accuracies were verified with controlled-release experiments. Typically, controlled releases were performed for short periods (15–20 min) under atmospheric conditions that were ideal for effective plume transport. We examined three methane release rates from three distances over various periods of time ranging from seven hours to seven days. Data were recorded continuously from a stationary tower. Atmospheric conditions were highly variable and not always conducive to conventional OTM 33A calculations. OTM 33A estimates were made for 20-min periods when the mean wind direction corresponded to ±90° of the direction from the controlled release to the tower. Further analyses were performed by varying the frequency of the data, the length of the individual OTM 33A periods and the size of the wind angle used to filter data. The results suggested that different (than conventionally used) period lengths, wind filters, data acquisition frequencies and data quality filters impacted the accuracy of OTM 33A when applied to long term measurements. 

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2. Opto-Thermomechanical Nanoprinting under ambient conditions

   https://doi.org/10.1364/OMA.2021.AW3D.3  

   Zhao, Chenglong (April 2021, Biophotonics Congress 2021)

   An opto-thermomechanical (OTM) nanoprinting method is demonstrated to not only additively print nanostructures with sub-100 nm accuracy but also to correct printing errors for nanorepairing under ambient conditions. 

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3. Additive Opto-Thermomechanical Nanoprinting and Nanorepairing under Ambient Conditions

   https://doi.org/10.1021/acs.nanolett.0c01261  

   Alam, Md Shah; Zhan, Qiwen; Zhao, Chenglong (June 2020, Nano Letters)

   We demonstrate an opto-thermomechanical (OTM) nanoprinting method that allows us not only to additively print nanostructures with sub-100 nm accuracy but also to correct printing errors for nanorepairing under ambient conditions. Different from other existing nanoprinting methods, this method works when a nanoparticle on the surface of a soft substrate is illuminated by a continuous-wave (cw) laser beam in a gaseous environment. The laser heats the nanoparticle and induces a rapid thermal expansion of the soft substrate. This thermal expansion can either release a nanoparticle from the soft surface for nanorepairing or transfer it additively to another surface in the presence of optical forces for nanoprinting with sub-100 nm accuracy. Details of the printing mechanism and parameters that affect the printing accuracy are investigated. This additive OTM nanoprinting technique paves the way for rapid and affordable additive manufacturing or 3D printing at the nanoscale under ambient conditions. 

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4. Understanding the Accuracy Limitations of Quantifying Methane Emissions Using Other Test Method 33A

   https://doi.org/10.3390/environments9040047  

   Heltzel, Robert; Johnson, Derek; Zaki, Mohammed; Gebreslase, Aron; Abdul-Aziz, Omar I. (April 2022, Environments)

   Researchers have utilized Other Test Method (OTM) 33A to quantify methane emissions from natural gas infrastructure. Historically, errors have been reported based on a population of measurements compared to known controlled releases of methane. These errors have been reported as 2σ errors of ±70%. However, little research has been performed on the minimum attainable uncertainty of any one measurement. We present two methods of uncertainty estimation. The first was the measurement uncertainty of the state-of-the-art equipment, which was determined to be ±3.8% of the estimate. This was determined from bootstrapped measurements compared to controlled releases. The second approach of uncertainty estimation was a modified Hollinger and Richardson (H&R) method which was developed for quantifying the uncertainty of eddy covariance measurements. Using a modified version of this method applied to OTM 33A measurements, it was determined that uncertainty of any given measurement was ±17%. Combining measurement uncertainty with that of stochasticity produced a total minimum uncertainty of 17.4%. Due to the current nature of stationary single-sensor measurements and the stochasticity of atmospheric data, such uncertainties will always be present. This is critical in understanding the transport of methane emissions and indirect measurements obtained from the natural gas industry. 

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5. 3D printed models are an accurate, cost-effective, and reproducible tool for quantifying terrestrial thermal environments

   https://doi.org/10.1016/j.jtherbio.2023.103762  

   Alujević, Karla; Bakewell, Leah; Clifton, Ian T; Cox, Christian L; Frishkoff, Luke O; Gangloff, Eric J; Garcia-Costoya, Guillermo; Gifford, Matthew E; Glenwinkel, Madison; Gulati, Samir AK; et al (December 2023, Journal of Thermal Biology)

   Predicting ecological responses to rapid environmental change has become one of the greatest challenges of modern biology. One of the major hurdles in forecasting these responses is accurately quantifying the thermal environments that organisms experience. The distribution of temperatures available within an organism's habitat is typically measured using data loggers called operative temperature models (OTMs) that are designed to mimic certain properties of heat exchange in the focal organism. The gold standard for OTM construction in studies of terrestrial ectotherms has been the use of copper electroforming which creates anatomically accurate models that equilibrate quickly to ambient thermal conditions. However, electroformed models require the use of caustic chemicals, are often brittle, and their production is expensive and time intensive. This has resulted in many researchers resorting to the use of simplified OTMs that can yield substantial measurement errors. 3D printing offers the prospect of robust, easily replicated, morphologically accurate, and cost-effective OTMs that capture the benefits but alleviate the problems associated with electroforming. Here, we validate the use of OTMs that were 3D printed using several materials across eight lizard species of different body sizes and living in habitats ranging from deserts to tropical forests. We show that 3D printed OTMs have low thermal inertia and predict the live animal's equilibration temperature with high accuracy across a wide range of body sizes and microhabitats. Finally, we developed a free online repository and database of 3D scans (https://www.3dotm.org/) to increase the accessibility of this tool to researchers around the world and facilitate ease of production of 3D printed models. 3D printing of OTMs is generalizable to taxa beyond lizards. If widely adopted, this approach promises greater accuracy and reproducibility in studies of terrestrial thermal ecology and should lead to improved forecasts of the biological impacts of climate change. 

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