| 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. |
- Wang, Mingyi, et al.
(författare)
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Rapid growth of new atmospheric particles by nitric acid and ammonia condensation
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 581:7807, s. 184-
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Tidskriftsartikel (refereegranskat)abstract
- A list of authors and their affiliations appears at the end of the paper New-particle formation is a major contributor to urban smog(1,2), but how it occurs in cities is often puzzling(3). If the growth rates of urban particles are similar to those found in cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new urban particles should be rapidly scavenged by the high concentration of pre-existing particles. Here we show, through experiments performed under atmospheric conditions in the CLOUD chamber at CERN, that below about +5 degrees Celsius, nitric acid and ammonia vapours can condense onto freshly nucleated particles as small as a few nanometres in diameter. Moreover, when it is cold enough (below -15 degrees Celsius), nitric acid and ammonia can nucleate directly through an acid-base stabilization mechanism to form ammonium nitrate particles. Given that these vapours are often one thousand times more abundant than sulfuric acid, the resulting particle growth rates can be extremely high, reaching well above 100 nanometres per hour. However, these high growth rates require the gas-particle ammonium nitrate system to be out of equilibrium in order to sustain gas-phase supersaturations. In view of the strong temperature dependence that we measure for the gas-phase supersaturations, we expect such transient conditions to occur in inhomogeneous urban settings, especially in wintertime, driven by vertical mixing and by strong local sources such as traffic. Even though rapid growth from nitric acid and ammonia condensation may last for only a few minutes, it is nonetheless fast enough to shepherd freshly nucleated particles through the smallest size range where they are most vulnerable to scavenging loss, thus greatly increasing their survival probability. We also expect nitric acid and ammonia nucleation and rapid growth to be important in the relatively clean and cold upper free troposphere, where ammonia can be convected from the continental boundary layer and nitric acid is abundant from electrical storms(4,5).
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| 3. |
- Wang, Mingyi, et al.
(författare)
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Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7910, s. 483-489
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
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| 4. |
- Wang, Lei, et al.
(författare)
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Air-Water Interface Assembly of Protein Nanofibrils Promoted by Hydrophobic Additives
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:28, s. 9289-9299
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Tidskriftsartikel (refereegranskat)abstract
- Herein we demonstrate a novel way of modifying the colloidal stability of proteins by the presence of hydrophobic molecules. A protein capable of self-assembly into protein nanofibrils (PNFs) is milled with a hydrophobic molecular material. Upon dissolution in acidic water followed by heating, the proteins are converted into PNFs containing hydrophobic dyes. When aqueous dispersions of such PNFs are heated, films are formed at the air-water interface. The films contain ordered, optically anisotropic domains, and the shape of the reaction vessel can influence the PNF packing. We demonstrate the generality of the process by employing PNFs derived from the three proteins bovine insulin (INS), beta-lactoglobulin (BLG), and hen egg white lysozyme (HEWL) in combination with the dyes alpha-sexithiophene (6T) and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). As individual dye molecules are oriented along the long PNF axis, whole ensembles of dyes become aligned and, as a result, display emission of polarized light. Moreover, in the case of PNFs stained with DCM, stimulated emission is demonstrated.
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| 5. |
- Wang, Xiaoning, et al.
(författare)
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Effectiveness of driver's bounded rationality and speed guidance on fuel-saving and emissions-reducing at a signalized intersection
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 325, s. 129343-
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Tidskriftsartikel (refereegranskat)abstract
- To reduce the fuel consumption and emissions of drivers passing through signalized intersections, this research proposes a fuel-saving and emissions-reducing strategy at a signalized intersection which takes into account driver's bounded rationality and speed guidance, including the theoretical basis of strategy, the scenario division of vehicle speed guidance, and the solution of vehicle optimal trajectory. Drivers are divided into three types: aggressive, normal, and conservative. Bounded rationality is divided into three levels: low, medium, and high. And the 3 x 3 x 3 numerical simulation experiments are carried out under low, medium, and high traffic flow. The results show that when the speed guidance is received, aggressive drivers have the greatest fuel-saving and emissions-reducing benefits, followed by conservative drivers. When the bounded rationality level changes under high traffic flow or the level of traffic flow and bounded rationality change concurrently, the benefits will be greatly affected. The driver's bounded rationality harms fuel consumption and emissions, and this negative effect increases with the increase of traffic flow. Providing corrected speed guidance can effectively reduce the negative effect. This study can provide more effective guidance information for drivers in a manual driving environment.
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| 6. |
- Yao, Nannan, et al.
(författare)
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In Situ Study the Dynamics of Blade-Coated All-Polymer Bulk Heterojunction Formation and Impact on Photovoltaic Performance of Solar Cells
- 2023
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; , s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- All-polymer solar cells (all-PSCs) have achieved impressive progress by employing acceptors polymerized from well performing small-molecule non-fullerene acceptors. Herein, the device performance and morphology evolution in blade-coated all-PSCs based on PBDBT:PF5–Y5 blends prepared from two different solvents, chlorobenzene (CB), and ortho-xylene (o-XY) are studied. The absorption spectra in CB solution indicate more ordered conformation for PF5–Y5. The drying process of PBDBT:PF5–Y5 blends is monitored by in situ multifunctional spectroscopy and the final film morphology is characterized with ex situ techniques. Finer-mixed donor/acceptor nanostructures are obtained in CB-cast film than that in o-XY-cast ones, corresponding to more efficient charge generation in the solar cells. More importantly, the conformation of polymers in solution determines the overall film morphology and the device performance. The relatively more ordered structure in CB-cast films is beneficial for charge transport and reduced non-radiative energy loss. Therefore, to achieve high-performance all-PSCs with small energy loss, it is crucial to gain favorable aggregation in the initial stage in solution.
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| 7. |
- Yuan, Yusheng, et al.
(författare)
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Mechanochemical Preparation of Protein : hydantoin Hybrids and Their Release Properties
- 2022
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Ingår i: ChemSusChem. - : Wiley-VCH Verlag GMBH. - 1864-5631 .- 1864-564X. ; 15:2
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Tidskriftsartikel (refereegranskat)abstract
- Mechanochemistry is a versatile methodology that can be employed both for covalent bond formation in organic synthesis as well as a mediator to allow preparation novel colloidal dispersions for drug delivery. Herein, ball-milling was employed for the solid-state preparation of fluorescent hydrophobic hydantoins, followed by the unprecedented mechanochemically-mediated complexation of hydrophobic hydantoins within hydrophilic protein beta-lactoglobulin (BLG) and BLG nanofibrils (BLGNFs). These hydantoin:protein materials were in turn incorporated into hydrogels. The effect of incorporation of hydantoins into proteins, as well as the effect of protein structure, on the release properties were then investigated. The conversion of BLG to BLGNFs led to a more sustained release demonstrating that heat treatment of BLG into BLGNFs could be employed to modify release properties. To the best of our knowledge, this is the first example where protein : hydantoin complexes were prepared by mechanochemical methodology and mechanochemistry was combined with self-assembly in order to prepare protein nanomaterials for drug-delivery applications. In addition, the use of the developed protein materials is not limited to delivery of drugs but can for example be employed as components of smart food (delivery of nutrients) or release systems of pesticides.
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