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1. Detection of small drizzle droplets in a large cloud chamber using ultrahigh-resolution radar

   https://doi.org/10.5194/amt-17-1133-2024  

   Zhu, Zeen; Yang, Fan; Kollias, Pavlos; Shaw, Raymond A; Kostinski, Alex B; Krueger, Steve; Lamer, Katia; Allwayin, Nithin; Oue, Mariko (January 2024, Atmospheric Measurement Techniques)

   Abstract. A large convection–cloud chamber has the potential to produce drizzle-sized droplets, thus offering a new opportunity to investigate aerosol–cloud–drizzle interactions at a fundamental level under controlled environmental conditions. One key measurement requirement is the development of methods to detect the low-concentration drizzle drops in such a large cloud chamber. In particular, remote sensing methods may overcome some limitations of in situ methods. Here, the potential of an ultrahigh-resolution radar to detect the radar return signal of a small drizzle droplet against the cloud droplet background signal is investigated. It is found that using a small sampling volume is critical to drizzle detection in a cloud chamber to allow a drizzle drop in the radar sampling volume to dominate over the background cloud droplet signal. For instance, a radar volume of 1 cubic centimeter (cm3) would enable the detection of drizzle embryos with diameter larger than 40 µm. However, the probability of drizzle sampling also decreases as the sample volume reduces, leading to a longer observation time. Thus, the selection of radar volume should consider both the signal power and the drizzle occurrence probability. Finally, observations from the Pi Convection–Cloud Chamber are used to demonstrate the single-drizzle-particle detection concept using small radar volume. The results presented in this study also suggest new applications of ultrahigh-resolution cloud radar for atmospheric sensing. 

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2. Accurate Measurement of Small Features in X‐Ray CT Data Volumes, Demonstrated Using Gold Grains

   https://doi.org/10.1029/2018JB017083  

   Ketcham, R. A.; Mote, A. S. (April 2019, Journal of Geophysical Research: Solid Earth)

   Abstract We present a method for measuring small, discrete features near the resolution limit of X‐ray computed tomography (CT) data volumes with the aim of providing consistent answers across instruments and data resolutions. The appearances of small features are impacted by the partial volume effect and blurring due to the data point‐spread function, and we call our approach the partial‐volume and blurring (PVB) method. Features are segmented to encompass their total attenuation signal, which is then converted to a volume, in turn allowing a subset of voxels to be used to measure shape and orientation. We demonstrate the method on a set of gold grains, scanned with two instruments at a range of resolutions and with various surrounding media. We recover volume accurately over a factor of 27 range in grain volume and factor of 5 range in data resolution, successfully characterizing particles as small as 5.4 voxels in true volume. Shape metrics are affected variably by resolution effects and are more reliable when based on image‐based caliper measurements than perimeter length or surface area. Orientations are reproducible when maximum or minimum axis lengths are sufficiently different from the intermediate axis. Calibration requires end‐member CT numbers for the materials of interest, which we obtained empirically; we describe a first‐principles calculation and discuss its challenges. The PVB method is accurate, reproducible, resolution invariant, and objective, all important improvements over any method based on global thresholds. 

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3. Diversity – volume relationships: adding structural arrangement and volume to species – area relationships across forest macrosystems

   https://doi.org/10.1111/ecog.06723  

   LaRue, Elizabeth A.; Downing, Anna G.; Saucedo, Sheila; Rocha, Arturo; Zesati, Sergio A.; Mata‐Silva, Vicente; Harvey, Michael G. (October 2023, Ecography)

   The species – area relationship (SAR) is a common pattern in which diversity increases with the area sampled, but ecosystems are three‐dimensional (3D) and diversity – volume relationships (DVRs) may exist in ecosystems that vary substantially in their vegetation volume. We tested whether forest vegetation volume, as a 3D extension of area in SARs, was a significant predictor of taxonomic (species) and structural (arrangement) diversity in five groups of organisms across the National Ecological Observatory Network (NEON). Vegetation volume and four structural arrangement metrics within the area of NEON plots were measured using NEON's discrete return lidar. Species richness was measured as the number of species within the respective NEON plot sampling area for understory plants, trees, breeding land birds, small mammals, and ground beetles. We found that volume negatively predicted understory plants and positively predicted tree and beetle species richness across the USA forest macrosystem, but not bird and small mammal species richness. Furthermore, volume was a significant predictor of several metrics that describe the internal and external heterogeneity of vegetation in forests (structural arrangement) within the ecosystem across the USA forest macrosystem. There were several significant within site‐level relationships, but not at all sites, between volume and species richness or structural arrangement in organism groups. Our study indicates that previous work that has focused on a 2D conceptualization of habitat can be expanded to 3D habitat space, but that the strength and the positive or negative direction of DVRs may vary taxonomically or geographically. 

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4. Nanoconfinement and Crowding Enhanced Single-Molecule Detection of Small Molecules with Nanopipettes

   https://doi.org/10.1021/jacs.3c09311  

   Khatri, Santosh; Pandey, Popular; Mejia, German; Ghimire, Govinda; Leng, Fenfei; He, Jin (December 2023, Journal of the American Chemical Society)

   Glass nanopipette has gained widespread use as a versatile single-entity detector in chemical and biological sensing, analysis, and imaging. Its advantages include low cost, easy accessibility, simplicity of use, and high versatility. However, conventional nanopipettes based on the volume exclusion mechanism have limitations in detecting small biomolecules due to their small volume and high mobility in aqueous solution. To overcome this challenge, we have employed a novel approach by capitalizing on the strong nanoconfinement effect of nanopipette. This is achieved by utilizing both the hard confinement provided by the long taper nanopipette tip at the cis side and the soft confinement offered by the hydrogel at the trans side. Through this approach we have effectively slowed down the exit motion of small molecules, allowing us to enrich and jam them at the nanopipette tip. Consequently, we have achieved high throughput detection of small biomolecules with sizes as small as 1 nm, including nucleoside triphosphates, short peptides, and small proteins with excellent signal-to-noise ratios. Furthermore, molecular complex formation through specific intermolecular interactions, such as hydrogen bonding between closely spaced nucleotides in the jam-packed nanopipette tip, have been detected based on the unique ionic current changes. 

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5. A preliminary assessment of olivine phenocrysts from the monogenetic basalt of the McCartys Flow, Zuni-Bandera Volcanic Field, New Mexico

   Gary S. Michelfelder, Lawrence K. (October 2021, New Mexico Geological Society 72nd Annual Fall Field Conference Guidebook)

   Frey, Bonnie A.; Kelley, Shari A.; Zeigler, Kate E.; McLemore, Virginia T.; Goff, Fraser; Ulmer-Scholle, Dana S. (Ed.)

   Monogenetic small-volume basaltic volcanoes are the most abundant subaerial volcanic landforms on Earth but are some of the most poorly understood systems. Their short durations, small volumes, and lack of recurrence make monitoring and hazard assessment difficult. The Zuni-Bandera volcanic field in western New Mexico contains small-volume basaltic centers erupting tholeiitic to alkalic basalts. Evidence shows no correlation of magma composition with eruption age, location, or volumetric output, prompting questions about the influence of magma ascent rates, magma storage conditions, and mantle source characteristics on lava compositions. Here, we present olivine major and minor element mineral chemistry from the 3200-year-old McCartys Flow, the youngest tholeiite basalt in the volcanic field. Olivine displays four phenocryst types with unique textures and major and minor element compositions. Multiple olivine types co-exist at the thin section scale. Major and minor element diffusion at frozen melt–phenocryst interfaces was modeled, revealing magma residence times ranging from 3–9 months. Type 3 olivine phenocrysts require step function initial conditions and record diffusion re-equilibration followed by magma mixing. These profiles indicate the magma resided in the reservoir for 10–15 years and accumulated from multiple batches of mixed magmas less than 10 days before the eruption. Our results show that primitive magmas in small-volume monogenetic volcanoes have complex lithospheric magmatic histories and stored in magma bodies influenced by an open system to develop different local chemical environments. 

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