| 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. |
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| 3. |
- Rehnlund, David, et al.
(författare)
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Improved cycling stability of conversion and alloying anodes through the use of nanomaterials
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In order to meet the growing need for portable energy storage future batteries need to provide improved energydensities. One major problem lies in the current use of intercalation based electrode materials which are typicallylimited to storing one lithium ion per formula unit. Improved energy storage can be achieved through the use ofconversion and alloying reactions where it is possible to store multiple lithium ions per formula unit. Eventhough impressive energy densities can be obtained through the use of conversion and alloying anode materials,only surpassed by the use of lithium metal itself, these systems are typically plagued by capacity fading duringcycling. The origin is generally ascribed to irreversible reactions with the electrolyte amplified by major volumeexpansion, causing the growth of a solid electrolyte interphase (i.e. SEI). One promising strategy to address thisissue is through the use of nanosized electrode materials (e.g. Si nanoparticles), as it has been shown thatnanoparticles and nanowires show better cycling stability than their bulk counterparts [1, 2]. Large particles (i.emicrometer sized) form cracks during cycling as opposed to smaller particles (i.e. < 150 nm) [3]. Even thoughthe use of nanoparticles can reduce crack formation and the accompanied SEI growth, capacity fading is stillobserved for these systems. Our work has focused on studying freestanding nanostructured conversion materials(e.g. Cu2O nanowires), which offer in depth analyses of the conversion reactions without disturbance frombinders or conducting additives. Contrary to previous understanding nanosized Cu2O thin films and multilayerednanostructures show an increase in capacity during cycling [4, 5]. This behaviour is caused by improvedaccess to the entire material when using the nanomaterials. The system has also shown improved performanceduring cycling likely caused by electrochemical milling of the particles thereby consistently reducing the particlesize and thus allowing more of the material to be accessible. With the successful use of nanosized conversionmaterials our research is now focused on addressing the stability problems of alloying materials by studying theeffect of nanomaterials.References1. A. Magasinski, et al.. Nat. Mater., 2010. 22: p. 353-3582.2 C.K. Chan, et al.. Nat. Nanotechnol., 2008. 3: p. 31-353.3 X. H. Liu, et al.. Adv. En. Mater., 2012. 2: p. 722-7414.4 D. Rehnlund, et al.. J. Mat. Chem. A., 2014. 2: p. 9574-95865.5 D. Rehnlund, et al.. Nanoscale, 2015. 7: p. 13591-13604
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| 4. |
- Rehnlund, David, 1986-, et al.
(författare)
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Lithium trapping in alloy forming electrodes and current collectors for lithium based batteries
- 2017
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 10:6, s. 1350-1357
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Tidskriftsartikel (refereegranskat)abstract
- Significant capacity losses are generally seen for batteries containing high-capacity lithium alloy forming anode materials such as silicon, tin and aluminium. These losses are generally ascribed to a combination of volume expansion effects and irreversible electrolyte reduction reactions. Here, it is shown, based on e.g. elemental analyses of cycled electrodes, that the capacity losses for tin nanorod and silicon composite electrodes in fact involve diffusion controlled trapping of lithium in the electrodes. While an analogous effect is also demonstrated for copper, nickel and titanium current collectors, boron-doped diamond is shown to function as an effective lithium diffusion barrier. The present findings indicate that the durability of lithium based batteries can be improved significantly via proper electrode design or regeneration of the used electrodes. © The Royal Society of Chemistry 2017.
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| 5. |
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| 6. |
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| 7. |
- Tsigkourakos, Menelaos, et al.
(författare)
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Suppression of boron incorporation at the early growth phases of boron-doped diamond thin films
- 2015
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 212:11, s. 2595-2599
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Tidskriftsartikel (refereegranskat)abstract
- The presence of O during the chemical vapour deposition (CVD) of B-doped diamond results in the suppression of B incorporation into the diamond film. In this study, we demonstrate that the amount of residual O within the chamber is higher at the beginning of the diamond growth due to the O-contaminated chamber walls, and is decreased after a certain time period. This leads to a gradual increase of the B incorporation by more than one order of magnitude during the early growth phases of nanocrystalline diamond (NCD). We further show that this suppression of B incorporation at the early growth phases of B-doped diamond is influenced by the growth rate of the film. This is attributed to the constant time period whereby most of the residual O interacts with the B-precursors in the gas phase by forming stable B-O species, which are flushed out from the chamber exhaust. Furthermore, the constant B profile of an NCD film grown in a loadlock hot-filament CVD (HFCVD) system reveals that the amount of residual O is constant and minimal during the growth process. Therefore, our work proves that the use of a loadlock overcomes the B-suppression problem at the early growth phases of diamond, making it the optimal solution for the growth of highly conductive thin diamond films.
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| 8. |
- Yan, Yinglin, et al.
(författare)
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Waste Office Paper Derived Cellulose-Based Carbon Host in Freestanding Cathodes for Lithium-Sulfur Batteries
- 2022
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Ingår i: ChemElectroChem. - : John Wiley & Sons. - 2196-0216. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Due to large sulfur (S) content and simple manufacturing techniques, free-standing cathodes for lithium-sulfur (Li−S) batteries are gaining a lot of attention recently. Waste office paper, which is consumed in large quantities annually, was used to make a free-standing paper-based carbon (FPC) substrate, which inherited fiber-like morphology. In addition, reduced graphene oxide (rGO) nanosheets modified FPC (rGO@FPC) host was also prepared by a vacuum filtration method. After S impregnation, the FPC/S and rGO@FPC/S free-standing cathodes were employed in Li−S batteries. The rGO@FPC/S free-standing cathode exhibited extremely competitive electrochemical performance, including a reversible discharge capacity of 315 mAh g−1 at 0.5 C after 500 cycles. This is due to the uniform S distribution, which boosts the utilization ratio, and the significant blocking action for polysulfide ions, which prevents the redox shuttle effect.
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| 9. |
- Zou, Yiming, 1985-, et al.
(författare)
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Effect of Boron Doping on the CVD Growth Rate of Diamond
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:19, s. 10658-10666
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Tidskriftsartikel (refereegranskat)abstract
- The purpose with the present study has been to theoretically investigate the effect of boron doping on the diamond growth rate. The most frequently observed diamond surface planes (100), (111) and (110) were thereby carefully investigated using density functional theory calculations under periodic boundary conditions. It was shown that both the thermodynamic and kinetic aspects of the diamond growth process will be severely affected by the B dopant (as compared with the non-doped situations). More specifically, the results showed that B (positioned within the 2nd atomic C layer) will cause an enhancement in the growth rate. On the other hand, the effect of B positioned in the other atomic C layers showed a decreased growth rate. These observations did not only correlate with experimental results but did also explain the anomalous variations in the diamond growth rate (i.e., either increase or decrease) with B doping.
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| 10. |
- Zou, Yiming, et al.
(författare)
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Effect of CVD diamond growth by doping with nitrogen
- 2013
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Ingår i: Theoretical Chemistry accounts. - : Springer Science and Business Media LLC. - 1432-881X .- 1432-2234. ; 133:2, s. 1432-
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Tidskriftsartikel (refereegranskat)abstract
- The purpose with the present investigation has been to support and explain the experimental observation made regarding the enhancing effect by N doping on especially the diamond (100)-2 x 1 growth rate. Within the present study, also the commonly observed diamond (111) and (110) surfaces were included, all assumed to be H-terminated. Density functional theory calculations were used, based on a plane wave approach under periodic boundary conditions. It was shown that the surface H abstraction reaction is most probably the rate-limiting step during diamond growth. In addition, the results showed that it is N, substitutionally positioned within the upper diamond surface, that will cause the growth rate improvement, and not nitrogen chemisorbed onto the growing surface in the form of either NH (or NH2). The here presented numerical value for the growth rate enhancement for the diamond (100)-2 x 1 surface is almost identical with the experimentally obtained one (3.7 vs. 3.6). In addition, the (111) and (110) surfaces were shown to undergo a different growth rate enhancement, with about half as much for the (111) and (110) surfaces as compared to the diamond (100)-2 x 1 surface (1.9, 1.7 vs. 3.7). Despite the rate improvement for all surface planes, this difference will bring about a preferred diamond (100) surface texture.
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