| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Chen, Kaixuan, et al.
(author)
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Mapping formation mechanisms and transformation regimes of multiple Fe precipitates in Cu-Fe-Co alloy during casting process
- 2024
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In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 246
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Journal article (peer-reviewed)abstract
- Precipitate features including size, morphology, crystal structure, etc., are important parameters determining the performance of precipitate-strengthened alloys. Multiple Fe precipitates were identified in as-cast Cu alloys exhibiting the distinct features, which dramatically influence mechanical properties. However, a complete understanding of precipitation behaviors of Fe particles during casting, in terms of both microscopic kinetics and thermodynamics, remains experimentally challenging. Here, we report the combined implementation of transmission electron microscopy, Thermo-Calc calculations and First-principles calculations to map mechanisms and growth regimes of Fe precipitation in a Cu-Fe-Co system. Our analyses support the idea that to understand the microstructural evolution in the system, both thermodynamic and kinetic arguments must be taken into account. Then, using our multi-approach strategy, the complete picture of the formation and transformation of Fe precipitates is proposed. This work is vital to promote microstructural design for Cu-Fe(-Co) systems, and sheds new insights into understanding of intricate precipitation in alloys.
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| 3. |
- Wen, Chenyu, 1990-, et al.
(author)
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Generalized Noise Study of Solid-State Nanopores at Low Frequencies
- 2017
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In: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 2:2, s. 300-307
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Journal article (peer-reviewed)abstract
- Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study lowfrequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.
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| 4. |
- Wen, Qin, et al.
(author)
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Separating Direct Heat Flux Forcing and Freshwater Feedback on AMOC Change Under Global Warming
- 2023
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 50:22
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Journal article (peer-reviewed)abstract
- The Atlantic meridional overturning circulation (AMOC) is predicted to weaken under global warming. Whether it is caused by heat flux or freshwater flux is under debate. Here we separate these two processes in changing the AMOC under global warming. The simulated AMOC is weakened during the first 600years and then gradually recovered to its initial state, with heat flux and freshwater feedback dominating at different timescales. Global warming immediately puts freshwater into the Southern Ocean, which triggers the initial AMOC weakening via altering surface temperature. Concurrently, the extensive heat into the ocean surface increases the temperature over the subpolar North Atlantic, reducing the deep convection and thus the AMOC in the subsequent 50–150years. Meanwhile, the Arctic sea ice melt leads to the AMOC shutdown. Subsequently, the salinity accumulation in the subtropical North Atlantic propagating northward to restart the North Atlantic deep convection is responsible for the AMOC recovery.
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