| 1. |
- Beal, Jacob, et al.
(författare)
-
Robust estimation of bacterial cell count from optical density
- 2020
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
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.
|
|
| 2. |
- Yang, Weijia, 1989-, et al.
(författare)
-
Experimental investigation of theoretical stability regions for ultra-low frequency oscillations of hydropower generating systems
- 2019
-
Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- With the increasing momentum towards flexible power systems based on renewables, the role of hydropower has great importance, especially for providing balancing power. In this paper, a fundamental study on the operating stability of hydropower generating systems is conducted to reveal the practical characteristics for the newly emergent issue of ultra-low frequency oscillations. A unique study methodology is adapted by combing the theoretical analysis and the physical model experiment. In this paper, first, the set-up of the integral experiment platform for the transient processes of the pumped storage plants is presented. Second, a mathematical model of hydropower generating systems is built, and the theoretical stability analysis is conducted based on the Routh-Hurwitz criterion and the stability margin region. The model experiments related to the frequency stability of hydropower generating systems were conducted with reference to the stability region from theoretical analysis. The results demonstrate the sustained ultra-low frequency oscillations and frequency instability of hydropower units in experiments for the first time. Attenuation characteristics of the oscillations are theoretically derived based on the stability margin region, and then quantitatively identified by experiments. The experiment accorded with theoretical stability region within a reasonable tolerance that corresponded to the +/- 0.1 stability margin. (C) 2019 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Yang, Weijia, 1989-, et al.
(författare)
-
Model experiments and study on regulating stability of isolated hydropower plants
- 2019
-
Ingår i: 29th IAHR symposium on hydraulic machinery and systems. - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- Hydropower shoulders a large portion of the regulation and balancing duty in many power systems all over the world. The stable regulation of hydropower plants (HPPs) is a conventional and crucial research topic, and many meaningful studies have been carried out by theoretical analysis and numerical simulations; however seldom experimental works on this issue are reported. This paper investigates stability of isolated HPPs based on model experiments on an integral experiment platform for transient processes of pumped storage plants in Wuhan University. Theoretical stability analysis is conducted based on Routh Hurwitz stability criterion, and the stability region of the model power plant is obtained. The experiment results validate the theoretical analysis on the system stability, and the instability of the hydropower system due to poor settings of speed governor parameters are captured and demonstrated. This work presents initial results of experimental study on oscillation characteristics and regulation performance of HPPs for power system stability.
|
|
