| 751. |
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| 752. |
- Shi, Qi, et al.
(författare)
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Variation in the Photocurrent Response Due to Different Emissive States in Methylammonium Lead Bromide Perovskites
- 2018
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:7, s. 3818-3823
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Tidskriftsartikel (refereegranskat)abstract
- Thin films and crystals of methylammonium lead bromide (MAPbBr3) perovskites have strong photoluminescence (PL). Previous studies have shown that the emission arises from different states. However, the role of these states in the performance of a solar cell has not been reported. We have used photocurrent and photoluminescence microscopies (PCM and PLM) to investigate the correlation between the photocurrent (PC) and the PL behavior in the different regions of MAPbBr3 thin film solar cells. Our results show that the PC and the PL responses from the different regions in the thin film show poor correlation compared to the correlation between those of a high efficiency GaAs solar cell. Furthermore, we establish a relationship between the different emissive states and the PC and the PL responses. Out of the two emissive states at 2.34 and 2.28 eV that have been reported, only the state at 2.34 eV has a dominant contribution to the PC. Our results suggest that the emission at 2.28 eV is related to traps, which can lower the performance of the solar cells. Finally, the correlation analysis of the PC and the PL responses we have presented can be used in any solar cell made from direct band gap semiconductor to identify the loss channels in the device.
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| 753. |
- Shi, R. H., et al.
(författare)
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Metagenomic next-generation sequencing for detecting lower respiratory tract infections in sputum and bronchoalveolar lavage fluid samples from children
- 2023
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Ingår i: Frontiers in Cellular and Infection Microbiology. - 2235-2988. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Lower respiratory tract infections are common in children. Bronchoalveolar lavage fluid has long been established as the best biological sample for detecting respiratory tract infections; however, it is not easily collected in children. Sputum may be used as an alternative yet its diagnostic accuracy remains controversial. Therefore, this study sought to evaluate the diagnostic accuracy of sputum for detecting lower respiratory tract infections using metagenomic next-generation sequencing. Paired sputum and bronchoalveolar lavage fluid samples were obtained from 68 patients; pathogens were detected in 67 sputum samples and 64 bronchoalveolar lavage fluid samples by metagenomic next-generation sequencing, respectively. The combined pathogen-detection rates in the sputum and bronchoalveolar lavage fluid samples were 80.90% and 66.2%, respectively. For sputum, the positive predictive values (PPVs) and negative predictive values (NPVs) for detecting bacteria were 0.72 and 0.73, respectively, with poor Kappa agreement (0.30; 95% confidence interval: 0.218-0.578, P < 0.001). However, viral detection in sputum had good sensitivity (0.87), fair specificity (0.57), and moderate Kappa agreement (0.46; 95% confidence interval: 0.231-0.693, P < 0.001). The PPVs and NPVs for viral detection in sputum were 0.82 and 0.67, respectively. The consistency between the sputum and bronchoalveolar lavage fluid was poor for bacterial detection yet moderate for viral detection. Thus, clinicians should be cautious when interpreting the results of sputum in suspected cases of lower respiratory tract infections, particularly with regards to bacterial detection in sputum. Viral detection in sputum appears to be more reliable; however, clinicians must still use comprehensive clinical judgment.
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| 754. |
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| 755. |
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| 756. |
- Shi, Shuai, et al.
(författare)
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On Q-Factor Bounds for a Given Front-to-Back Ratio
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 151-152
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Konferensbidrag (refereegranskat)abstract
- In this paper, the goal is to solve an antenna current optimization problem minimizing the stored energy with a desired front-to-back ratio. This minimization problem is non-convex, and we use semidefinite relaxation techniques to find the solution. An initial study on the front-to-back ratio of a dipole shape is presented here.
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| 757. |
- Shi, Wenming, et al.
(författare)
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Ambient PM2.5 and its chemical constituents on lifetime-ever pneumonia in Chinese children : A multi-center study
- 2021
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- The long-term effects of ambient PM2.5 and chemical constituents on childhood pneumonia were still unknown. A cross-sectional study was conducted in 30,315 children in the China Children, Homes, Health (CCHH) project, involving 205 preschools in six cities in China, to investigate the long-term effects of PM2.5 constituents on lifetime-ever diagnosed pneumonia. Information on the lifetime-ever pneumonia and demographics were collected by validated questionnaires. The lifetime annual average ambient PM2.5, ozone and five main PM2.5 constituents, including SO42-, NO3-, NH4+, organic matter (OM) and black carbon (BC), were estimated according to preschool addresses by a combination of satellite remote sensing, chemical transport modeling and ground-based monitors. The prevalence of lifetime-ever diagnosed pneumonia was 34.5% across six cities and differed significantly among cities (p = 0.004). The two-level logistic regression models showed that the adjusted odds ratio for PM2.5 (per 10 µg/m3) and its constituents (per 1 µg/m3)-SO42-, NO3-, NH4+, and OM were 1.12 (95% CI:1.07-1.18), 1.02 (1.00-1.04), 1.06 (1.04-1.09), 1.05 (1.03-1.07) and 1.09 (1.06-1.12), respectively. Children in urban area, aged < 5 years and breastfeeding time < 6 months enhanced the risks of pneumonia. Our study provided robust results that long-term levels of ambient PM2.5 and its constituents increased the risk of childhood pneumonia, especially NH4+, NO3- and OM.
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| 758. |
- Shi, WF, et al.
(författare)
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Inhibitory effects of reserpine and carbonyl cyanide m-chloro-phenylhydrazone on fluoroquinolone resistance of Acinetobacter baumannii
- 2005
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Ingår i: Chinese Medical Journal. - 0366-6999. ; 118:4, s. 340-343
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms of bacterial resistance to fluoroquinolones may be grouped into three principal categories: gene mutations of DNA topoisomerase II (GyrA or GyrB), DNA topoisomerase IV (ParC or ParE), decrease of outer membrane permeation and upregulation of multi-drug efflux pump (active efflux system).(1) Efflux pumps are transport proteins removing toxic substrates ( including virtually all classes of clinically relevant antibiotics) from cells to the external environment. These proteins exist in both Gram positive bacteria and Gram negative bacteria as well as in fungi and mammalian (tumour) cells.(2-4) It has been reported that alkaloid reserpine and carbonyl cyanide m-chlorophenylhydrazone (CCCP) can inhibit NorA multi-drug efflux.(5,6) In order to explore the universality of drug efflux in microorganisms, 85 strains of Acinetobacter baumannii (A. baumannii) were tested using reserpine and CCCP. The quinolone-resistant-determining region (QRDR) of gyrA and parC genes in 35 isolates of A. baumannii were amplified by polymerase chain reaction (PCR) and sequenced by DNA sequencer. The correlation between resistant mutation regularity and bacterial drug efflux were analysed.
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| 759. |
- Shi, Wangqing, et al.
(författare)
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Modelling of impact sound insulation of lightweight steel framing floors
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- It is valuable for the house designer to be aware of a structure's acoustic performance from its material properties at the design stage. A simplified calculation procedure is necessary for this purpose. This report concerns the application of a homogeneous plate prediction model in determining the impact sound insulation for the lightweight steel framing floors. The method is a further development of a prediction method for timber floors. In order to calculate driving point impedance of the lightweight steel framing floor, an equivalent method is used in this study to obtain the parameters of the composite lightweight steel framing floor, e.g. floor height, material density and elasticity to replace a composite floor with a homogeneous single plate. The main advantages of this method will be its simplicity and improve the understanding of the impact sound insulation of the lightweight steel framing floors. This method can also give brief information about the acoustic performance of the structure at an earlier design stage.
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| 760. |
- Shi, Wei, et al.
(författare)
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Pause-melting misalignment: a novel model for the birth and motif indel of tandem repeats in the mitochondrial genome.
- 2013
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Ingår i: BMC genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: Tandem repeats (TRs) in the mitochondrial (mt) genome control region have been documented in a wide variety of vertebrate species. The mechanism by which repeated tracts originate and undergo duplication and deletion, however, remains unclear. RESULTS: We analyzed DNA sequences of mt genome TRs (mtTRs) in the ridged-eye flounder (Pleuronichthys cornutus), and characterized DNA sequences of mtTRs from other vertebrates using the data available in GenBank. Tandem repeats are concentrated in the control regions; however, we found approximately 16.6% of the TRs elsewhere in the mt genome. The flounder mtTRs possess three motif types with hypervariable characteristics at the 3[prime] end of the control region (CR). CONCLUSION: Based on our analysis of this larger dataset of mtTR sequences, we propose a novel model of Pause Melting Misalignment (PMM) to describe the birth and motif indel of tandem repeats. PMM is activated during a pause event in mitochondrial replication in which a dynamic competition between the nascent (N) heavy strand and the displaced (D) heavy strand may lead to the melting of the N-strand from the template (T) light strand. When mispairing occurs during rebinding of the N-strand, one or several motifs can be inserted or deleted in both strands during the next round of mt-replication or repair. This model can explain the characteristics of TRs in available vertebrate mt genomes.
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