| 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. |
- Chen, Yuqian, et al.
(författare)
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Experimental and numerical study of flow and ignition and lean blowout characteristics of jet-cooled wall flameholder in a dual-mode combustor
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- The wall flameholder is one of the credible alternatives to realize pilot ignition in augmented/ramjet combustors. To overcome the ablation for a long-term operation, two types of jet cooling, external-inhaled air and pressure-driven jet cooling, are proposed for the wall flameholder. In this work, the flow and combustion process in a laboratory scale rig is studied for different cooling schemes and cooling conditions using experimental and numerical methods. Flow analysis in pressure-driven jet cooling scheme shows that the flow field of flameholder is influenced significantly by the cooling hole angle on the oblique plate α and on the rear plate β. In particular, the cooling jet angle combinations (α=30o, β=30o) and (α=90o, β=150o) are the two schemes with the most different characteristics. To investigate the effects of jet cooling type and cooling jet angle on the flow, ignition, and lean blowout (LBO) characteristics, the two distinctively different angle combinations are applied to form two kinds of jet cooling schemes mentioned above. Results suggest that the jet cooling type has less impact on the flow field but more influence on the flow loss than the cooling jet angle. The ignition performance of cooling schemes with α=30o and β=30o is better than that of those with α=90o and β=150o, but it has a more significant flow loss. The LBO limits of external-inhaled air cooling are lower than that of pressure-driven jet cooling. Moreover, the ignition and LBO limits decrease gradually with the increased mainstream temperature and they are only slightly affected by the mainstream velocity. Notably, the pressure-driven jet cooling scheme can slightly reduce the flow loss but it leads to a deteriorated ignition and LBO performance. The external-inhaled air cooling scheme with α=30o and β=30o has an excellent ignition and LBO performance, and the ignition and LBO limits increase with the increasing cooling air flow rate and the decreasing cooling air temperature.
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| 3. |
- Chen, Yuqian, et al.
(författare)
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Experimental study on combustion and flow resistance characteristics of an afterburner with air-cooled bluff-body flameholder
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- In the afterburner assembled with an air-cooled bluff-body flameholder, cooling air is directly injected into the recirculation zone behind the bluff-body, which can reduce the local temperature and increase the oxygen concentration of the gas mixture in the wake of the bluff-body, thereby affecting the total pressure loss and combustion characteristics. To better understand the flow and combustion process of the system, the exhaust gas temperature, cold and hot total pressure losses in a rectangular premixed combustor are investigated under different cooling air jet conditions. Experimental results show that the added cooling air could improve the combustion efficiency and widen the blowout limit, whereas it could also give rise to an extra total pressure loss. However, when the cooling air flow rate was higher than a critical value, i.e., after the blowing ratio reached 2.5, the recirculation zone could be blown away, resulting in a failed ignition in the afterburner. Notably, the decreased temperature difference between the mainstream and the cooling air could improve the combustion efficiency and reduce the thermal resistance loss but enlarge the cold flow loss and hot total pressure loss. Moreover, since the oxygen content declined and autoignition appeared after the mainstream temperature reached 1100 K, the exhaust gas temperature and combustion efficiency declined rapidly, and the hot total pressure loss also decreased. In addition, with the fuel-gas ratio increasing, the combustion efficiency significantly dropped, the exhaust gas temperature and thermal resistance loss firstly increased to a peak value (at the equivalence ratio of 1.14) and then decreased for excessively fuel-rich combustion.
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| 4. |
- Chen, Yuqian, et al.
(författare)
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Investigation of flame characteristics and cooling effectiveness of jet-cooled wall flameholders in vitiated flow
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Experimental and numerical studies were performed to understand the flame characteristics and cooling effect of jet-cooled wall flameholders in a simplified augmented combustor. The time-averaged flame structure and wall temperature were investigated employing an instantaneous flame capturing system with image processing technology and a wall temperature measurement system, respectively. Flow and fuel distribution simulations were carried out to analyze the flame structure and cooling effect of the jet-cooled flameholders in high-temperature and high-velocity vitiated flows. It was found that the jet cooling type and the cooling jet angle on the oblique plate α and on the rear plate β greatly affect the flame features and cooling effect of the flameholder. The external-inhaled air cooling schemes can increase the flame luminosity and temperature and create a flame hollowed-out zone in the near-wall region to reduce flame radiation and heat convection, thereby achieving an excellent cooling effect. The pressure-driven gas jet cooling schemes yielded a weaker flame luminosity and its flame structure in the cavity more sensitive to the cooling jet angle than external-inhaled air cooling schemes. Moreover, the external-inhaled air cooling schemes have significantly better cooling effects than the pressure-driven gas jet cooling schemes under different mainstream conditions and fuel flow rates. Notably, the cooling schemes with α=30∘ and β=30∘ have more uniform wall temperature than that of α=90∘ and β=150∘ on the above two plates. Furthermore, the external-inhaled air cooling scheme with α=90∘ and β=150∘ has the best cooling performance under different mainstream and cooling air conditions and presents great cooling effectiveness in the case of enhancing cooling air temperature.
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| 5. |
- Chen, Yuqian, et al.
(författare)
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Study on ignition process and flame expansion and propagation characteristics in jet-cooled pilot flameholders using image processing techniques
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 129
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Tidskriftsartikel (refereegranskat)abstract
- Wall-type pilot flameholder has been used in aero-engines to effectively create a stable ignition source and achieve an excellent ignition performance in high-velocity flows. The ignition delay, flame propagation, and flame boundary are crucial characteristics to evaluate the performance of pilot flameholders. Previous work displayed the significantly changed ignition performance and flow features of the wall flameholder when jet cooling schemes were adopted, indicating that the ignition process and the flame features strongly depend on the cooling jet and the optimal design of jet cooling schemes needs further investigation. Therefore, in this study, two practical image processing algorithms are developed to characterize the flame development of the ignition process, reveal the effect of cooling schemes on the ignition delay time, and quantitatively analyze the flame area and expansion ratio of the wall flameholder during stable combustion. Two image processing methods proposed based on MATLAB algorithms exhibit effectiveness in studying the ignition process and flame expansion characteristics. The ignition process is divided into four phases: kernel generation, kernel propagation, flame growth, and stable combustion. Meanwhile, the ignition delay time is identified by counting the total pixels of the flame projected region during the ignition process. The edge detection and pixel statistics of the flame projected region in the binary luminosity image show the flame boundary and expansion ratio under various working conditions. It was found that the cooling jet angle has a significant impact on the ignition process, ignition delay time, flame propagation, and steady flame features. The pressure-driven gas jet cooling scheme with a smaller jet angle and the external-inhaled air cooling scheme with a larger jet angle present a better capability of ignition and flame expansion and propagation.
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| 6. |
- Fan, Qunping, 1989, et al.
(författare)
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Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation
- 2020
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027
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Tidskriftsartikel (refereegranskat)abstract
- Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
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| 7. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 8. |
- Pan, Wenwu, et al.
(författare)
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Photoluminescence of InGaAs/GaAsBi/InGaAs type-II quantum wells grown by gas source molecular beam epitaxy
- 2017
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 32:1
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Tidskriftsartikel (refereegranskat)abstract
- InxGa1-xAs/GaAs1-yBiy/InxGa1-xAs (0.20 ≤x ≤0.22, 0.035 ≤y ≤0.045) quantum wells (QWs) were grown on GaAs substrates by gas source molecular beam epitaxy for realizing the type-II band edge line-up. Both type-I and type-II transitions were observed in the Bi containing W QWs and the photoluminescence intensity was enhanced in the sample with a high Bi content, which is mainly due to the improvement of carrier confinement. The 8 band k • p model was used to analyze the electronic properties in the QWs and the calculated transition energies fit well with the experiment results. Our study shows that the proposed type-II QW is a promising candidate for realizing GaAs-based near infrared light emitting devices near 1.3 μm
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| 9. |
- Shin, Jung-Ho, et al.
(författare)
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Structural basis of peptidoglycan endopeptidase regulation
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:21, s. 11692-11702
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Tidskriftsartikel (refereegranskat)abstract
- Most bacteria surround themselves with a cell wall, a strong meshwork consisting primarily of the polymerized aminosugar peptidoglycan (PG). PG is essential for structural maintenance of bacterial cells, and thus for viability. PG is also constantly synthesized and turned over; the latter process is mediated by PG cleavage enzymes, for example, the endopeptidases (EPs). EPs themselves are essential for growth but also promote lethal cell wall degradation after exposure to antibiotics that inhibit PG synthases (e.g., beta-lactams). Thus, EPs are attractive targets for novel antibiotics and their adjuvants. However, we have a poor understanding of how these enzymes are regulated in vivo, depriving us of novel pathways for the development of such antibiotics. Here, we have solved crystal structures of the LysM/M23 family peptidase ShyA, the primary EP of the cholera pathogen Vibrio cholerae. Our data suggest that ShyA assumes two drastically different conformations: a more open form that allows for substrate binding and a closed form, which we predicted to be catalytically inactive. Mutations expected to promote the open conformation caused enhanced activity in vitro and in vivo, and these results were recapitulated in EPs from the divergent pathogens Neisseria gonorrheae and Escherichia coli. Our results suggest that LysM/M23 EPs are regulated via release of the inhibitory Domain 1 from the M23 active site, likely through conformational rearrangement in vivo.
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| 10. |
- Xing, Yuxin, et al.
(författare)
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FireNose on Mobile Robot in Harsh Environments
- 2019
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Ingår i: IEEE Sensors Journal. - : IEEE. - 1530-437X .- 1558-1748. ; 19:24, s. 12418-12431
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a novel multi-sensor unit, a.k.a. FireNose, to detect and discriminate both known and unknown gases in uncontrolled conditions to aid firefighters under harsh conditions. The unit includes three metal oxide (MOX) gas sensors with CMOS micro heaters, a plasmonic enhanced non-dispersive infrared (NDIR) sensor optimized for the detection of CO2, a commercial temperature humidity sensor, and a flow sensor. We developed custom film coatings for the MOX sensors (SnO2, WO3 and NiO) which greatly improved the gas sensitivity, response time and lifetime of the miniature devices. Our proposed system exhibits promising performance for gas sensing in harsh environments, in terms of power consumption (∼ 35 mW at 350°C per MOX sensor), response time (<10 s), robustness and physical size. The sensing unit was evaluated with plumes of gases in both, a laboratory setup on a gas testing rig and on-board a mobile robot operating indoors. These high sensitivity, high-bandwidth sensors, together with online unsupervised gas discrimination algorithms, are able to detect and generate their spatial distribution maps accordingly. In the robotic experiments, the resulting gas distribution maps corresponded well to the actual location of the sources. Therefore, we verified its ability to differentiate gases and generate gas maps in real-world experiments.
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