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- 2019
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Tidskriftsartikel (refereegranskat)
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- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)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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- Jaiswal, Siddhartha, et al.
(författare)
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Age-Related Clonal Hematopoiesis Associated with Adverse Outcomes.
- 2014
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Ingår i: New England Journal of Medicine. - 0028-4793. ; 371:26, s. 2488-2498
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Tidskriftsartikel (refereegranskat)abstract
- Background The incidence of hematologic cancers increases with age. These cancers are associated with recurrent somatic mutations in specific genes. We hypothesized that such mutations would be detectable in the blood of some persons who are not known to have hematologic disorders. Methods We analyzed whole-exome sequencing data from DNA in the peripheral-blood cells of 17,182 persons who were unselected for hematologic phenotypes. We looked for somatic mutations by identifying previously characterized single-nucleotide variants and small insertions or deletions in 160 genes that are recurrently mutated in hematologic cancers. The presence of mutations was analyzed for an association with hematologic phenotypes, survival, and cardiovascular events. Results Detectable somatic mutations were rare in persons younger than 40 years of age but rose appreciably in frequency with age. Among persons 70 to 79 years of age, 80 to 89 years of age, and 90 to 108 years of age, these clonal mutations were observed in 9.5% (219 of 2300 persons), 11.7% (37 of 317), and 18.4% (19 of 103), respectively. The majority of the variants occurred in three genes: DNMT3A, TET2, and ASXL1. The presence of a somatic mutation was associated with an increase in the risk of hematologic cancer (hazard ratio, 11.1; 95% confidence interval [CI], 3.9 to 32.6), an increase in all-cause mortality (hazard ratio, 1.4; 95% CI, 1.1 to 1.8), and increases in the risks of incident coronary heart disease (hazard ratio, 2.0; 95% CI, 1.2 to 3.4) and ischemic stroke (hazard ratio, 2.6; 95% CI, 1.4 to 4.8). Conclusions Age-related clonal hematopoiesis is a common condition that is associated with increases in the risk of hematologic cancer and in all-cause mortality, with the latter possibly due to an increased risk of cardiovascular disease. (Funded by the National Institutes of Health and others.).
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- Maxwell, James L., et al.
(författare)
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On "how to start a fire'', or transverse forced-convection, hyperbaric laser chemical vapor deposition of fibers and textiles
- 2014
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Ingår i: Textile research journal. - : SAGE Publications. - 0040-5175 .- 1746-7748. ; 84:18, s. 1976-1986
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Tidskriftsartikel (refereegranskat)abstract
- This work explores the transverse forced flow of precursor gases during hyperbaric pressure laser chemical vapor deposition (HP-LCVD). Axial and mass growth rates of carbon fibers are measured experimentally, and a numerical model is developed that provides fiber growth rates in both the mass-transport-limited (MTL) and kinetically limited (KL) regimes. It is found that the fiber's transport-limited rate increases as the square root of the flow velocity, while simultaneously, the temperature drops with the inverse square root of the flow velocity. Growth is enhanced by forced flow so long as the reaction zone remains within the MTL regime; upon reaching a critical temperature and flow rate, however, fibers enter the KL regime, and the growth rate declines with rising flow rate. Molecular properties of the precursors employed and gas concentrations ultimately determine the range of the MTL and the locations of the critical temperature and flow rate. The growth rates of fibers can indeed be enhanced by transverse forced convection-to at least three times the zero-flow steady-state rate, provided an MTL regime exists. Complex three-dimensional structures may be grown from these fibers in a freeform manner, and the more rapidly such microstructures can be fabricated, the more practical HP-LCVD becomes for industrial use, including the fabrication of novel textiles.
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