| 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. |
- Liu, Kun, et al.
(författare)
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A study of intrinsic amorphous silicon thin film deposited on flexible polymer substrates by magnetron sputtering
- 2016
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 449, s. 125-132
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous silicon (a-Si) has gained its popularity in thin film Solar cell fabrication for its high absorption coefficient, high applicability on flexible substrates and practical feasibility for low-cost roll-to-roll mass fabrication. Working as the intrinsic layer, the optical-electrical characteristics of amorphous silicon film is crucial to the cell performance. In this work, the amorphous silicon film has been fabricated on PET substrate by magnetron sputtering method. The main optical-electrical characteristics have been systematically investigated under different fabrication conditions (sputtering power, working pressure, working temperature). The results indicate that the deposition rate increases remarkably from 1.88 to 834 nm/min with the sputtering power increasing from 60 W to 120 W, while the light transmission rate decreases from 86% to 46% in the visible spectrum range (390 nm to 780 nm). Theoretical calculations have been carried out, showing a decreasing deposition rate under an increasing working pressure. A rising temperature provides a higher deposition rate and lower trans-mittance in the certain range. The optimized processing parameters in the fabrication of amorphous silicon thin film are obtained for high photoelectric property on flexible substrates.
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| 3. |
- Liu, Kun, et al.
(författare)
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B-Doped Amorphous Silicon Thin Films Deposited on Flexible PET Substrate by Magnetron Sputtering
- 2015
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Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 12:9, s. 2931-2936
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Tidskriftsartikel (refereegranskat)abstract
- Depositing amorphous silicon doped with different elements on flexible substrates offers a large potential for the roll-to-roll processes lowering the manufacturing cost of solar cells. Unique magnetron sputtering method was adopted to deposit B-doped amorphous silicon thin film on flexible PET substrate instead of solid substrate materials like glass, metal and silicon. Effects of different substrates were investigated, as well as the processing parameters including sputtering power and working pressure. The structure and performance of the samples were characterized with SEM, XRD, surface profile meter and UV-spectrophotometer. The comparison between PET and glass shows that the alternative of PET substrate significantly improved the deposition rate. Optimal results were obtained as pressure of 0.2 Pa and RF power of 120 W, which showed the lowest transmittance as well as a minimum optical band gap, both are of great significance to photovoltaic conversion. Theoretical justification and experimental data including the feasible magnetron sputtering way, PET flexible substrate and optimized process parameters to the mass production of cheap and high performance heterojunction thin film solar cells were achieved.
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| 4. |
- Felix, Roberto, et al.
(författare)
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Photoinduced phase segregation and degradation of perovskites revealed by x-ray photoelectron spectroscopy
- 2019
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Ingår i: 2019 IEEE 46th Photovoltaic Specialists Conference, PVSC 2019. - 0160-8371. - 9781728104942 ; , s. 2362-2367
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Konferensbidrag (refereegranskat)abstract
- Pb-based perovskite absorbers with organic (i.e., CH3NH3+) and inorganic (i.e., Cs+) cations and a halide composition of 75% Br and 25% I are investigated with x-ray photoelectron spectroscopy while submitted to environmental stress factors to study their stability. Changes in chemical properties of the absorbers were monitored in ultra-high vacuum and under simulated solar, as well as, x-ray irradiation. Although changes are detected for both types of perovskite absorbers, the organic cation perovskite exhibits a more pronounced tendency to photodegrade.
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| 5. |
- Jiang, Sheng, et al.
(författare)
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In Situ Reconstruction of Hole-Selective Perovskite Heterojunction with Graded Energetics Toward Highly Efficient and Stable Solar Cells
- 2023
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 13:27
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite solar cells (PSCs) have demonstrated a high power conversion efficiency, however, the large energy loss due to non-radiative recombination is the main challenge for further performance enhancement. Here, a surface treatment strategy is developed by heat-induced decomposition of a thin interlayer 2,7-Naphthaleneditriflate (NAP) to in situ reconstruct perovskite energetics. It is verified that the reconstructed perovskite surface energetics match better with the upper hole transport layer compared to the intrinsic condition. Spontaneous generation of n/n(-) homojunctions between the perovskite film bulk and the surface region promotes hole extraction, enhancing built-in electric field, and thus significantly suppresses charge recombination at such perovskite hole-selective heterojunctions. Moreover, the surface decomposed fluorine-rich complexes passivate the defects and improve the crystallinity of the perovskite film. These advantages are confirmed by a remarkably improved efficiency from 20.52% for the control device to 23.37% for the treated one with excellent stability. The work provides a promising approach of in situ reconstructing perovskite surface and interface for the design of highly efficient and stable PSCs.
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| 6. |
- Liu, Sheng, et al.
(författare)
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An improved estimation of soil water and salt dynamics by considering soil bulk density changes under freeze/thaw conditions in arid areas with shallow groundwater tables
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 859
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Tidskriftsartikel (refereegranskat)abstract
- Soil bulk density (BD) is a parameter dependent on soil texture, compositions of soil minerals and organic matter and the extent of soil compaction. Seasonal freeze/thaw in arid areas with shallow groundwater tables (AASGT) may significantly change BD and hence soil hydrothermal properties and water holding capacity. Therefore, quantifying soil bulk density changes (BDC) under freeze/thaw conditions can improve estimates of soil water-salt dynamics in AASGT. In this study, we conducted field experiments to investigate the soil water-salt dynamics under freeze/thaw conditions from three typical land-use types (i.e., farmland, woodland, and natural land) in the upper Yellow River basin, China. We proposed a method to estimate BDC, which can better describe the soil water-salt dynamics during the freeze/thaw period. Our results showed marked BDC occurred in all layers within the 0–100 cm profile in natural land, while mainly at the 20–80 cm profile in farmland. During the freezing period, BD in farmland and natural land first decreased rapidly and then remained relatively stable until the thawing period started. After that, BD gradually increased during the thawing period. The largest BDC in farmland and natural land were 0.48 g cm−3 (occurring at the 30–40 cm layer) and 0.43 g cm−3 (occurring at the 80–90 cm layer), respectively, close to 30 % of their initial values. The differences in BDC between the three land-use types were mainly owing to their differences in groundwater table depth, initial soil salt concentration, soil texture, and surface coverage conditions. Moreover, in farmland and natural land, ignoring BDC resulted in different degrees of overestimation or underestimation in soil water content, water fluxes, and soil hydrothermal properties in the selected soil layers. This study demonstrates that considering BDC can improve the accuracy of soil water-salt dynamics estimation in AASGT under freeze/thaw conditions.
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| 7. |
- Liu, Sheng, et al.
(författare)
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Improving soil hydrological simulation under freeze–thaw conditions by considering soil deformation and its impact on soil hydrothermal properties
- 2023
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 619
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Tidskriftsartikel (refereegranskat)abstract
- Traditional agricultural or eco-hydrological models usually ignore soil deformation and its impact on hydrothermal properties when simulating soil water, heat, and salt transport under freeze–thaw conditions. As a result, significant errors may occur when these models are used in areas with considerable frost heave, such as arid areas with shallow groundwater tables. In this study, the simultaneous heat and water model (SHAW model) was modified with considering soil deformation and its impact on hydrothermal properties during the freeze–thaw period. The modified SHAW model was then validated using the experimental data collected at the Hetao Irrigation District, in the upper Yellow River basin. Comparison between the simulated and observed data showed that the modified SHAW model performed well and obviously better than the original SHAW model in simulating the soil water, heat, and salt transport. As compared with the SHAW model, the modified SHAW model averagely decreased the RMSE value by 37.5% and 23% for soil water content and soil temperature, respectively. The modified model can be used as a decision tool for water management and salinity control of farmland in cold areas with significant frost heave.
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| 8. |
- Yuan, Jianyu, et al.
(författare)
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Comparing the device physics, dynamics and morphology of polymer solar cells employing conventional PCBM and non-fullerene polymer acceptor N2200
- 2017
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Ingår i: Nano Energy. - : ELSEVIER SCIENCE BV. - 2211-2855 .- 2211-3282. ; 35, s. 251-262
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Tidskriftsartikel (refereegranskat)abstract
- Current all polymer solar cells still suffer from low fill factors (FF) and short-circuit current density (J(sc)) compared with the conventional polymer/fullerene system. Herein in this work, devices using PTP8 as the electron donor and [70]PCBM as well as widely used polymer N2200 as the electron acceptor were systematically studied and compared. The major loss mechanisms in the all polymer solar cells were investigated to understand their relatively lower performance than the PTP8/fullerene system. By performing in-depth analysis on ultrafast transient transmission spectroscopy results, we estimated that in PTP8/N2200 device nearly half of the charges recombine geminately, which is confirmed as the major factor hindering the device performance of all polymer solar cells compared with polymer/fullerene system. Through thorough morphology analysis, the low charge generation efficiency is attributed to the reduced crystallinity of N2200 in the blend film and the unfavorable face-to-edge orientation at the donor/acceptor heterojunction. Coupling these results with knowledge from efficient polymer/fullerene systems, the future design of new polymers can devote to increase the attraction between the pi face of donor and acceptor, leading to enhanced face-to-face orientation at the heterojunction, while maintaining a high pi-pi stacking order for each polymer.
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