| 1. |
- 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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| 2. |
- Schweinsberg, Martin, et al.
(författare)
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Same data, different conclusions : Radical dispersion in empirical results when independent analysts operationalize and test the same hypothesis
- 2021
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Ingår i: Organizational Behavior and Human Decision Processes. - : Elsevier BV. - 0749-5978 .- 1095-9920. ; 165, s. 228-249
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Tidskriftsartikel (refereegranskat)abstract
- In this crowdsourced initiative, independent analysts used the same dataset to test two hypotheses regarding the effects of scientists' gender and professional status on verbosity during group meetings. Not only the analytic approach but also the operationalizations of key variables were left unconstrained and up to individual analysts. For instance, analysts could choose to operationalize status as job title, institutional ranking, citation counts, or some combination. To maximize transparency regarding the process by which analytic choices are made, the analysts used a platform we developed called DataExplained to justify both preferred and rejected analytic paths in real time. Analyses lacking sufficient detail, reproducible code, or with statistical errors were excluded, resulting in 29 analyses in the final sample. Researchers reported radically different analyses and dispersed empirical outcomes, in a number of cases obtaining significant effects in opposite directions for the same research question. A Boba multiverse analysis demonstrates that decisions about how to operationalize variables explain variability in outcomes above and beyond statistical choices (e.g., covariates). Subjective researcher decisions play a critical role in driving the reported empirical results, underscoring the need for open data, systematic robustness checks, and transparency regarding both analytic paths taken and not taken. Implications for orga-nizations and leaders, whose decision making relies in part on scientific findings, consulting reports, and internal analyses by data scientists, are discussed.
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| 3. |
- Ayedh, H. M., et al.
(författare)
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Carbon vacancy control in p(+)-n silicon carbide diodes for high voltage bipolar applications
- 2021
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 54:45
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Tidskriftsartikel (refereegranskat)abstract
- Controlling the carbon vacancy (V-C) in silicon carbide (SiC) is one of the major remaining bottleneck in manufacturing of high voltage SiC bipolar devices, because V-C provokes recombination levels in the bandgap, offensively reducing the charge carrier lifetime. In literature, prominent V-C evolutions have been measured by capacitance spectroscopy employing Schottky diodes, however the trade-offs occurring in the p(+)-n diodes received much less attention. In the present work, applying similar methodology, we showed that V-C is re-generated to its unacceptably high equilibrium level at similar to 2 x10(13) V-C cm(-3) by 1800 degrees C anneals required for the implanted acceptor activation in the p(+)-n components. Nevertheless, we have also demonstrated that the V-C eliminating by thermodynamic equilibrium anneals at 1500 degrees C employing carbon-cap can be readily integrated into the p(+)-n components fabrication resulting in <= 10(11) V-C cm(-3), potentially paving the way towards the realization of the high voltage SiC bipolar devices.
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| 4. |
- Springell, R., et al.
(författare)
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Elemental engineering : Epitaxial uranium thin films
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:19
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial films of the well-known alpha (orthorhombic) structure and an unusual hcp form of uranium have been grown on Nb and Gd buffers, respectively, by sputtering techniques. In a 5000 A film of alpha-U a charge-density wave has been observed, and its properties are different from those found in the bulk. The 500 A hcp-U film has a c/a ratio of 1.90(1), which is unusually large for the hcp structure. Theoretical calculations show that this hcp form is metastable and predict that it orders magnetically.
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| 5. |
- Wåhlin, Anna, 1970, et al.
(författare)
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Swirls and scoops : Ice base melt revealed by multibeam imagery of an Antarctic ice shelf
- 2024
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 10:31
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge gaps about how the ocean melts Antarctica's ice shelves, borne from a lack of observations, lead to large uncertainties in sea level predictions. Using high-resolution maps of the underside of Dotson Ice Shelf, West Antarctica, we reveal the imprint that ice shelf basal melting leaves on the ice. Convection and intermittent warm water intrusions form widespread terraced features through slow melting in quiescent areas, while shear-driven turbulence rapidly melts smooth, eroded topographies in outflow areas, as well as enigmatic teardrop-shaped indentations that result from boundary-layer flow rotation. Full-thickness ice fractures, with bases modified by basal melting and convective processes, are observed throughout the area. This new wealth of processes, all active under a single ice shelf, must be considered to accurately predict future Antarctic ice shelf melt.
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| 6. |
- Hagberg, Erik C., et al.
(författare)
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Effects of modulus and surface chemistry of thiol-ene photopolymers in nanoimprinting
- 2007
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7:2, s. 233-237
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Tidskriftsartikel (refereegranskat)abstract
- Thiol-ene photopolymers were studied as patternable resins for nanocontact molding imprint lithography. Photopolymerizable thiol and ene monomer mixtures were used, and after molding, patterned thiol-ene polymer features the size and shape of the original molds were replicated. Adhesion and release were examined and controlled by manipulating the surface chemistry of the substrate and mold. A direct correlation between cured thiol-ene polymer modulus and pattern fidelity was observed.
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| 7. |
- Ling, G., et al.
(författare)
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PATCHED and p53 gene alterations in sporadic and hereditary basal cell cancer
- 2001
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Ingår i: Oncogene. - : Springer. - 0950-9232 .- 1476-5594. ; 20:53, s. 7770-7778
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Tidskriftsartikel (refereegranskat)abstract
- It is widely accepted that disruption of the hedgehog-patched pathway is a key event in development of basal cell cancer. In addition to patched gene alterations, p53 gene mutations are also frequent in basal cell cancer. We determined loss of heterozygosity in the patched and p53 loci as well as sequencing the p53 gene in tumors both from sporadic and hereditary cases. A total of 70 microdissected samples from tumor and adjacent skin were subjected to PCR followed by fragment analysis and DNA sequencing. We found allelic loss in the patched locus in 6/8 sporadic basal cell cancer and 17/19 hereditary tumors. All sporadic and 7/20 hereditary tumors showed p53 gene mutations. Loss of heterozygosity in the p53 locus was rare in both groups. The p53 mutations detected in hereditary tumors included rare single nucleotide deletions and unusual double-base substitutions compared to the typical ultraviolet light induced missense mutations found in sporadic tumors. Careful microdissection of individual tumors revealed genetically linked subclones with different p53 and/or patched genotype providing an insight on time sequence of genetic events. The high frequency and co-existence of genetic alterations in the patched and p53 genes suggest that both these genes are important in the development of basal cell cancer.
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| 8. |
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| 9. |
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| 10. |
- Persson, A. E., et al.
(författare)
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Analysis of p53 mutations in single cells obtained from histological tissue sections
- 2000
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 287:1, s. 25-31
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Tidskriftsartikel (refereegranskat)abstract
- We have previously reported on direct sequence analysis of the p53 gene in laser-dissected single cells from tissue sections, where each allele of two fragments (exons 7 and 8) could be accurately analyzed in only 14% of the cells due to the high frequency of exon and allele dropout. Here in an effort to minimize this problem, we have investigated various approaches for sample preparation and gene amplification. By pinpointing some critical steps in the procedure, we could increase the number of investigated exons and substantially improve the genetic analysis of single cells obtained from histochemically stained frozen tissue sections. The biggest improvement was achieved by minimizing DNA degradation using EDTA as a nuclease inhibitor in all sample preparation steps. Efforts to increase primer annealing, by increasing the concentration of template and primers, in addition to prolonging the annealing and extension times, also improved the amplification efficiency. With these measures we can now amplify six individual exons of the p53 gene (exons 4-9) in 70% of the cells and in 50% of these cells both alleles are amplified. This allows application of the method in various investigations such as within the held of tumor pathology.
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