| 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. |
- Niu, Li-Ping, et al.
(författare)
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Mechanism of fluidized chlorination reaction of Kenya natural rutile ore
- 2014
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Ingår i: Rare Metals. - : Springer Science and Business Media LLC. - 1001-0521 .- 1867-7185. ; 33:4, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the thermodynamics and kinetics of nature rutile carbochlorination in a fluidized-bed were investigated. The thermodynamic calculations of TiO2-C-Cl-2 system show that when C is excess in the solid phase, titanium tetrachloride and carbon monoxide can exist stably. At high temperature, the reaction with CO as the product is the dominant reaction. The appropriate reaction conditions are as follows: reaction temperature of 950 A degrees C, reaction time of 40 min, carbon ratio of 30 wt% of rutile, natural rutile particle size of -96 mu m, petroleum coke size of -150 mu m, and chlorine flow of 0.036 m(3)center dot h(-1). Under the above conditions, the reaction conversion rate of TiO2 can reach about 95 %. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is generally consistent with the experimental data. For the TiO2-C-Cl-2 system, the reaction rate is dependent on the initial radius of rutile particle, density, and the partial pressures of Cl-2. From 900 to 1,000 A degrees C, the apparent activation energy is 10.569 kJ center dot mol(-1), and the mass diffusion is found to be the main reaction-controlling step. The expression for the chlorine reaction rate in the C-Cl-2 system is obtained, and it depends on the degree of reaction, the partial pressure of Cl-2, and the size of rutile particle.
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| 3. |
- Zhang, Yue-Jiao, et al.
(författare)
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Probing the Electronic Structure of Heterogeneous Metal Interfaces by Transition Metal Shelled Gold Nanoparticle-Enhanced Raman Spectroscopy
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:37, s. 20684-20691
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Tidskriftsartikel (refereegranskat)abstract
- In heterogeneous catalysis, characterization of heterogeneous metal interfaces of bimetallic catalysts is a crucial step to elucidate the catalytic performance and is a key to develop advanced catalysts. However, analytical techniques such as X-ray photoelectron spectroscopy can only work in vacuum conditions and are difficult to use for in situ analysis. Here, we present efficient and convenient core-shell nano particle-enhanced Raman spectroscopy to explore the in situ electronic structures of heterogeneous interfaces (Au@Pd and Au@Pt core-shell NPs) by varying the shell thickness. The experimental observations reported here clearly show that Pd donates electrons to Au, while Pt accepts electrons from Au at the heterogeneous interfaces. This conclusion gains further support from ex situ X-ray photoelectron spectroscopy results. The Au core greatly affects the electronic structures of both the Pd and Pt shells as well as catalytic behaviors. Finally, the as prepared core-shell nanoparticles were used to demonstrate their improved catalytic properties in real electrocatalytic systems such as methanol oxidation and oxygen reduction reactions.
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| 4. |
- An, Junxue, et al.
(författare)
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Temperature-Dependent Adsorption and Adsorption Hysteresis of a Thermoresponsive Diblock Copolymer
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:15, s. 4333-4341
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Tidskriftsartikel (refereegranskat)abstract
- A nonionic-cationic diblock copolymer, poly(2-isopropyl-2-oxazoline)(60)-b-poly((3-acrylamidopropyl)- trimethylammonium chloride)(17), (PIPOZ(60)-b-PAMPTMA(17)), was utilized to electrostatically tether temperature-responsive PIPOZ chains to silica surfaces by physisorption. The effects of polymer concentration, pH, and temperature on adsorption were investigated using quartz crystal microbalance with dissipation monitoring and ellipsometry. The combination of these two techniques allows thorough characterization of the adsorbed layer in terms of surface excess, thickness, and water content. The high affinity of the cationic PAMPTMA(17) block to the negatively charged silica surface gives rise to a high affinity adsorption isotherm, leading to (nearly) irreversible adsorption with respect to dilution. An increase in solution pH lowers the affinity of PIPOZ to silica but enhances the adsorption of the cationic block due to increasing silica surface charge density, which leads to higher adsorption of the cationic diblock copolymer. Higher surface excess is also achieved at higher temperatures due to the worsening of the solvent quality of water for the PIPOZ block. Interestingly, a large hysteresis in adsorbed mass and other layer properties was observed when the temperature was cycled from 25 to 45 degrees C and then back to 25 degrees C. Possible causes for this temperature hysteresis are discussed.
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| 5. |
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| 6. |
- An, Wei, et al.
(författare)
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Mechanistic Study of CO Titration on CuxO/Cu(111) (x <= 2) Surfaces
- 2014
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Ingår i: ChemCatChem. - : Wiley-VCH Verlagsgesellschaft. - 1867-3880 .- 1867-3899. ; 6:8, s. 2364-2372
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Tidskriftsartikel (refereegranskat)abstract
- The reducibility of metal oxides is of great importance to their catalytic behavior. Herein, we combined ambient-pressure scanning tunneling microscopy (AP-STM), X-ray photoemission spectroscopy (AP-XPS), and DFT calculations to study the CO titration of CuxO thin films supported on Cu(111) (CuxO/Cu(111)) aiming to gain a better understanding of the roles that the Cu(111) support and surface defects play in tuning catalytic performances. Different conformations have been observed during the reduction, namely, the 44 structure and a recently identified (5-7-7-5) Stone-Wales defects (5-7 structure). The DFT calculations revealed that the Cu(111) support is important to the reducibility of supported CuxO thin films. Compared with the case for the Cu2O(111) bulk surface, at the initial stage CO titration is less favorable on both the 44 and 5-7 structures. The strong CuxO <-> Cu interaction accompanied with the charge transfer from Cu to CuxO is able to stabilize the oxide film and hinder the removal of O. However, with the formation of more oxygen vacancies, the binding between CuxO and Cu(111) is weakened and the oxide film is destabilized, and Cu2O(111) is likely to become the most stable system under the reaction conditions. In addition, the surface defects also play an essential role. With the proceeding of the CO titration reaction, the 5-7 structure displays the highest activity among all three systems. Stone-Wales defects on the surface of the 5-7 structure exhibit a large difference from the 44 structure and Cu2O(111) in CO binding energy, stability of lattice oxygen, and, therefore, the reduction activity. The DFT results agree well with the experimental measurements, demonstrating that by adopting the unique conformation, the 5-7 structure is the active phase of CuxO, which is able to facilitate the redox reaction and the Cu2O/Cu(111)<-> Cu transition.
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