| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)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. |
- Li, Wei, et al.
(author)
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Non-lab and semi-lab algorithms for screening undiagnosed diabetes : A cross-sectional study
- 2018
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In: EBioMedicine. - : ELSEVIER SCIENCE BV. - 2352-3964. ; 35, s. 307-316
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Journal article (peer-reviewed)abstract
- Background: The terrifying undiagnosed rate and high prevalence of diabetes have become a public emergency. A high efficiency and cost-effective early recognition method is urgently needed. We aimed to generate innovative, user-friendly nomograms that can be applied for diabetes screening in different ethnic groups in China using the non-lab or noninvasive semi-lab data. Methods: This multicenter, multi-ethnic, population-based, cross-sectional study was conducted in eight sites in China by enrolling subjects aged 20-70. Sociodemographic and anthropometric characteristics were collected. Blood and urine samples were obtained 2 h following a standard 75 g glucose solution. In the final analysis, 10,794 participants were included and randomized into model development (n - 8096) and model validation (n = 2698) group with a ratio of 3:1. Nomograms were developed by the stepwise binary logistic regression. The nomograms were validated internally by a bootstrap sampling method in the model development set and externally in the model validation set. The area under the receiver operating characteristic curve (AUC) was used to assess the screening performance of the nomograms. Decision curve analysis was applied to calculate the net benefit of the screening model. Results: The overall prevalence of undiagnosed diabetes was 9.8% (1059/10794) according to ADA criteria. The non-lab model revealed that gender, age, body mass index, waist circumference, hypertension, ethnicities, vegetable daily consumption and family history of diabetes were independent risk factors for diabetes. By adding 2 h post meal glycosuria qualitative to the non-lab model, the semi-lab model showed an improved Akaike information criterion (AIC: 4506 to 3580). The AUC of the semi-lab model was statistically larger than the non-lab model (0.868 vs 0.763, P < 0.001). The optimal cutoff probability in semi-lab and non-lab nomograms were 0.088 and 0.098, respectively. The sensitivity and specificity were 76.3% and 81.6%, respectively in semi-lab nomogram, and 72.1% and 673% in non-lab nomogram at the optimal cut off point. The decision curve analysis also revealed a bigger decrease of avoidable OGTT test (52 per 100 subjects) in the semi-lab model compared to the non-lab model (36 per 100 subjects) and the existed New Chinese Diabetes Risk Score (NCDRS, 35 per 100 subjects). Conclusion: The non-lab and semi-lab nomograms appear to be reliable tools for diabetes screening, especially in developing countries. However, the semi-lab model outperformed the non-lab model and NCDRS prediction systems and might be worth being adopted as decision support in diabetes screening in China.
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| 3. |
- Chen, Wei, et al.
(author)
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Colloidal PbS quantum dot stacking kinetics during deposition via printing
- 2020
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In: Nanoscale Horizons. - : Royal Society of Chemistry (RSC). - 2055-6764 .- 2055-6756. ; 5:5, s. 880-885
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Journal article (peer-reviewed)abstract
- Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 +/- 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.
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| 4. |
- Guo, Renjun, et al.
(author)
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Degradation mechanisms of perovskite solar cells under vacuum and one atmosphere of nitrogen
- 2021
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In: Nature Energy. - : Springer Nature. - 2058-7546. ; 6:10, s. 977-
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Journal article (peer-reviewed)abstract
- Extensive studies have focused on improving the operational stability of perovskite solar cells, but few have surveyed the fundamental degradation mechanisms. One aspect overlooked in earlier works is the effect of the atmosphere on device performance during operation. Here we investigate the degradation mechanisms of perovskite solar cells operated under vacuum and under a nitrogen atmosphere using synchrotron radiation-based operando grazing-incidence X-ray scattering methods. Unlike the observations described in previous reports, we find that light-induced phase segregation, lattice shrinkage and morphology deformation occur under vacuum. Under nitrogen, only lattice shrinkage appears during the operation of solar cells, resulting in better device stability. The different behaviour under nitrogen is attributed to a larger energy barrier for lattice distortion and phase segregation. Finally, we find that the migration of excessive PbI2 to the interface between the perovskite and the hole transport layer degrades the performance of devices under vacuum or under nitrogen. Understanding degradation mechanisms in perovskite solar cells is key to their development. Now, Guo et al. show a greater degradation of the perovskite structure and morphology for devices operated under vacuum than under nitrogen.
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| 5. |
- Li, B., et al.
(author)
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Perspectives of energy transitions in East and Southeast Asia
- 2020
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In: Wiley Interdisciplinary Reviews. - : John Wiley and Sons Ltd. - 2041-8396 .- 2041-840X. ; 9:1
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Journal article (peer-reviewed)abstract
- Energy transitions are designed to improve the resilience, sustainability, and productivity of a country's energy system, and are the key instruments to mitigating the warming climate. Countries and regions have unique circumstances when projecting energy transition pathways. Nonetheless, East Asian economies have shared opportunities and challenges. From the perspective of fuel mix, East Asia had some initial success in renewable energy development accompanied by energy efficiency improvements. Nuclear energy, although controversial, has been well developed and is continuing its advancement in East Asia. However, the dominance of coal in the energy mix has not been sufficiently addressed, mostly because of legacy issues. The region's renewable energy potential is also underdeveloped due to a mismatch between resources and energy demand. Since the region as whole is well endowed with renewable energy resources, the region's advancement in regional energy connectivity presents a valuable institutional asset to further decarbonize East Asian energy sector beyond individual nation's efforts. This article is categorized under: Energy and Climate > Economics and Policy Energy Policy and Planning > Economics and Policy Energy and Development > Economics and Policy.
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| 6. |
- Li, Y., et al.
(author)
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A life cycle analysis techno-economic assessment framework for evaluating future technology pathways – The residential air-conditioning example
- 2021
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In: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 291
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Journal article (peer-reviewed)abstract
- Clarity on cost and environmental benefits of individual technologies evaluated in a systemic and systematic manner is necessary in communicating the results at the policy level so as to enable effective decisions. Yet, the highly complex nature of many energy modelling tools makes it difficult for non-specialists to interpret and make sense of their results. An integrated life cycle analysis and techno-economic assessment framework is proposed in this study, as a first step towards developing an alternative and potentially more intuitive energy systems modelling tool. The residential air-conditioning sector in the Southeast Asian context is used as an example to demonstrate the advantages of the modelling methodology in profiling future technology pathways. The use of best available R32 technology can lead to cumulative savings of 2195 million tonnes of greenhouse gas emissions in the region by 2050; while the best available R407C technology has an average cost of $40.85 per tonne of greenhouse gas abatement. In addition, our modelling tool is capable of profiling energy outlooks for emerging economies and will be further integrated with hourly energy analysis frameworks in the next steps of development.
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| 7. |
- Liu, S., et al.
(author)
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Performance analysis of two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit
- 2019
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In: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 189
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Journal article (peer-reviewed)abstract
- The use of carbon dioxide (CO2) as refrigerant is driven by the need to phase down the traditional synthetic refrigerant so as to mitigate the warming climate. In this study, the thermal performance of a two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit is conducted. The goal is to obtain the maximum coefficient of performance (COP) of five different mechanical subcooling systems under the optimal subcooling temperature and compressor discharge pressure. The two-throttling and two-stage compression high-pressure mechanical subcooling system is found to have a higher COP. When the evaporation temperature is −30 °C, the COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is improved by 76.74%. The COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is 1.52 at an ambient temperature of 40 °C, which is 21.87% higher than that of the two-throttling and two-stage compression low-pressure mechanical subcooling system. The power consumption ratio of one-throttling and two-stage compression low-pressure mechanical subcooling system is significantly higher than that of other systems. From a comprehensive analysis of the proposed four systems, the two-throttling and two-stage compression high-pressure mechanical subcooling system has the best performance over all other systems.
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| 8. |
- Yang, S., et al.
(author)
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Economics of marinised offshore charging stations for electrifying the maritime sector
- 2022
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In: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 322
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Journal article (peer-reviewed)abstract
- Electrification of international maritime transport, despite rapidly falling battery prices and improvements in battery technologies, remains constrained by midway charging, as the range of electric ocean-going vehicles is limited on a full charge. Before countries pour trillions of dollars of investment, this study is commissioned as the first attempt to investigate the economics of offshore marinised charging stations for enabling long-distance shipping by full-electric vessels. Three offshore power generation technologies, namely, wind, solar, and floating nuclear power plants, are compared to demonstrate the economics of offshore charging stations. Compared to conventional vessels using bunker fuels, full-electric vessels are cost competitive even under the assumed first-of-a-kind costs. Among the three offshore power sources compared in this study, a marinised charging station with floating nuclear power plant is shown to be the most cost-competitive. Despite the absence of a pilot project, the technoeconomic parameters as assumed in this study serve as important reference indicators for decision makers to consider when building an ecosystem for sustainable international shipping. © 2022 Elsevier Ltd
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| 9. |
- Chen, Wei, et al.
(author)
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In situ Grazing-Incidence Small-Angle X-ray Scattering Observation of Gold Sputter Deposition on a PbS Quantum Dot Solid
- 2020
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In: ACS Applied Materials and Interfaces. - : NLM (Medline). - 1944-8244 .- 1944-8252. ; 12:41, s. 46942-46952
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Journal article (peer-reviewed)abstract
- For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9-2.4 nm) are influenced by the QDs' templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs' boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD-gold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes.
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| 10. |
- Gensch, Marc, et al.
(author)
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Correlating Optical Reflectance with the Topology of Aluminum Nanocluster Layers Growing on Partially Conjugated Diblock Copolymer Templates
- 2021
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:47, s. 56663-56673
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Journal article (peer-reviewed)abstract
- Large-scale fabrication of metal cluster layers for usage in sensor applications and photovoltaics is a huge challenge. Physical vapor deposition offers large-scale fabrication of metal cluster layers on templates and polymer surfaces. In the case of aluminum (Al), only little is known about the formation and interaction of Al clusters during sputter deposition. Complex polymer surface morphologies can tailor the deposited Al cluster layer. Here, a poly(methyl methacrylate)-block-poly(3-hexylthiophen-2,5-diyl) (PMMA-b-P3HT) diblock copolymer template is used to investigate the nanostructure formation of Al cluster layers on the different polymer domains and to compare it with the respective homopolymers PMMA and P3HT. The optical properties relevant for sensor applications are monitored with ultraviolet-visible (UV-vis) measurements during the sputter deposition. The formation of Al clusters is followed in situ with grazing-incidence small-angle X-ray scattering (GISAXS), and the chemical interaction is revealed by X-ray photoelectron spectroscopy (XPS). Furthermore, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) yield topographical information about selective wetting of Al on the P3HT domains and embedding in the PMMA domains in the early stages, followed by four distinct growth stages describing the Al nanostructure formation.
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