| 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. |
- Chong, Hui, et al.
(författare)
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Organo-ptii complexes for potent photodynamic inactivation of multi-drug resistant bacteria and the influence of configuration
- 2024
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Ingår i: Advanced Science. - : John Wiley & Sons. - 2198-3844.
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Tidskriftsartikel (refereegranskat)abstract
- PtII based organometallic photosensitizers (PSs) have emerged as novel potent photodynamic inactivation (PDI) reagents through their enhanced intersystem crossing (ISC) processes. Currently, few PtII PSs have been investigated as antibacterial materials, with relatively poor performances reported and with structure-activity relationships not well described. Herein, a pair of configurational isomers are reported of Bis-BODIPY (4,4-difluoro-boradizaindacene) embedded PtII PSs. The cis-isomer (cis-BBP) displayed enhanced 1O2 generation and better bacterial membrane anchoring capability as compared to the trans-isomer (trans-BBP). The effective PDI concentrations (efficiency > 99.9%) for cis-BBP in Acinetobacter baumannii (multi-drug resistant (MDR)) and Staphylococcus aureus are 400 nM (12 J cm−2) and 100 nM (18 J cm−2), respectively; corresponding concentrations and light doses for trans-BBP in the two bacteria are 2.50 µM (30 J cm−2) and 1.50 µM (18 J cm−2), respectively. The 50% and 90% minimum inhibitory concentration (MIC50 and MIC90) ratio of trans-BBP to cis-BBP is 22.22 and 24.02 in A. baumannii (MDR); 21.29 and 22.36 in methicillin resistant S. aureus (MRSA), respectively. Furthermore, cis-BBP displays superior in vivo antibacterial performance, with acceptable dark and photoinduced cytotoxicity. These results demonstrate cis-BBP is a robust light-assisted antibacterial reagent at sub-micromolecular concentrations. More importantly, configuration of PtII PSs should be an important issue to be considered in further PDI reagents design.
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| 3. |
- Wang, Qi, 1993-, et al.
(författare)
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Oysters for legacy and emerging per- and polyfluoroalkyl substances (PFASs) monitoring in estuarine and coastal waters : Phase distribution and bioconcentration profile.
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 846
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Tidskriftsartikel (refereegranskat)abstract
- Per- and polyfluoroalkyl substances (PFASs) are a diverse group of widely used anthropogenic chemicals that are environmentally persistent and bioaccumulative, especially in aquatic ecosystem. The heavily industrialized and urbanized Greater Bay Area in China represents a notable contamination source for PFASs, which may potentially influence the health of local oysters as a keystone species in local ecosystems and a popular seafood. In this study, samples of oysters and their surrounding waters were collected from the littoral zones of the Pearl River Estuary (PRE), China during winter 2020, where 44 PFASs, including 19 perfluoroalkyl acids (PFAAs), 8 emerging PFASs, and 17 PFAA precursors (or intermediates), were analyzed. Total PFAS concentrations ranged 13.8-58.8 ng/L in the dissolved phase, 3.60-11.2 ng/g dry weight (dw) in the suspended particulate matter (SPM), and 0.969-1.98 ng/g dw in the oysters. Most short-chain PFASs were present in the dissolved phase (>95%), while long-chain PFASs generally showed higher concentrations in the SPM. Log field-based bioconcentration factors (BCFs) of long-chain PFASs increased linearly (r = 0.95, p < 0.01) with increasing estimated log membrane-water (Dmw) and protein-water (Dpw) distribution coefficients. Perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA) exhibited higher measured BCFs than those estimated by their Dmw and Dpw. Considering the widespread occurrence of their precursors, the contribution of precursor transformation was likely to be a significant source of PFHxA and PFHpA. Oysters from the PRE littoral zones posed low risks to human health associated with PFAS consumption, which might be underestimated due to limited toxicity data available for PFAA precursors and emerging PFASs. This study sheds light on the practicality of applying oysters as biomonitors for timely PFAS monitoring in coastal environments.
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| 4. |
- Durand, Fabien, et al.
(författare)
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Vladimir Sergeevich Anashin
- 2011
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Ingår i: P-Adic Numbers, Ultrametric Analysis, and Applications. - 2070-0466 .- 2070-0474. ; 3:4, s. 359-362
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Wang, Qi, et al.
(författare)
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Legacy and Emerging Per- and Polyfluoroalkyl Substances in a Subtropical Marine Food Web : Suspect Screening, Isomer Profile, and Identification of Analytical Interference
- 2023
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:22, s. 8355-8364
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Tidskriftsartikel (refereegranskat)abstract
- The ban/elimination of legacy per- and polyfluoroalkyl substances (PFASs) has led to a dramatic increase in the production and use of various emerging PFASs over the past decade. However, trophodynamics of many emerging PFASs in aquatic food webs remain poorly understood. In this study, samples of seawaters and marine organisms including 15 fish species, 21 crustacean species, and two cetacean species were collected from the northern South China Sea (SCS) to investigate the trophic biomagnification potential of legacy and emerging PFASs. Bis(trifluoromethylsulfonyl)imide was found in seawater via suspect screening (concentration up to 1.50 ng/L) but not in the biota, indicating its negligible bioaccumulation potential. A chlorinated perfluorooctane sulfonate (PFOS) analytical interfering compound was identified with a predicted formula of C14H23O5SCl6- (most abundant at m/z = 514.9373). Significant trophic magnification was observed for 22 PFASs, and the trophic magnification factors of cis- and trans-perfluoroethylcyclohexane sulfonate isomers (1.92 and 2.25, respectively) were reported for the first time. Perfluorohexanoic acid was trophic-magnified, possibly attributed to the PFAS precursor degradation. The hazard index of PFOS was close to 1, implying a potential human health risk via dietary exposure to PFASs in seafood on the premise of continuous PFAS discharge to the SCS.
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| 6. |
- Wang, Qi, et al.
(författare)
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Tracing per- and polyfluoroalkyl substances (PFASs) in the aquatic environment : Target analysis and beyond
- 2023
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Ingår i: TrAC. Trends in analytical chemistry. - : Elsevier. - 0165-9936 .- 1879-3142. ; 169
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Forskningsöversikt (refereegranskat)abstract
- Per-and polyfluoroalkyl substances (PFASs) have been manufactured and used for decades. The aquatic envi-ronment is a critical transportation and transformation compartment for PFASs. Target analysis is the most used method of tracing PFASs in the aquatic environment but is powerless for the large amounts of unknown PFASs. This review summarizes the advantages of three target analysis supplementary approaches, including extractable organofluorine (EOF) analysis, high-resolution mass spectrometry (HRMS) screening, and PFAS precursor oxidative conversion. For known PFASs, more targets, including emerging PFASs, PFAS isomers, ultrashort-chain PFASs, and cationic/zwitterionic PFASs, should be considered. For unknown PFASs and organofluorines, developing comprehensive and low-contaminated sample treatment strategies is essential yet challenging. We propose including PFASs screened via HRMS at confidence level (CL) 3 and above in EOF mass balance analysis and CL 4 for samples collected from a "known source". Appropriate approaches should be applied to investigate unknown PFASs beyond target analysis comprehensively.
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| 7. |
- Xu, Yuefei, et al.
(författare)
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Distributed Device Networks With Security Constraints
- 2005
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Ingår i: IEEE Transactions on Industrial Informatics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1551-3203 .- 1941-0050. ; 1:4, s. 217-225
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Tidskriftsartikel (refereegranskat)abstract
- In today's globalized business world, outsourcing, joint ventures, mobile and cross-border collaborations have led to work environments distributed across multiple organizational and geographical boundaries. The new requirements of portability, configurability and interoperability of distributed device networks put forward new challenges and security risks to the system's design and implementation. There are critical demands on highly secured collaborative control environments and security enhancing mechanisms for distributed device control, configuration, monitoring, and interoperation. This paper addresses the collaborative control issues of distributed device networks under open and dynamic environments. The security challenges of authenticity, integrity, confidentiality, and execution safety are considered as primary design constraints. By adopting policy-based network security technologies and XML processing technologies, two new modules of Secure Device Control Gateway and Security Agent are introduced into regular distributed device control networks to provide security and safety enhancing mechanisms. The core architectures, applied mechanisms, and implementation considerations are presented in detail in this paper.
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| 8. |
- Zhou, Sha, et al.
(författare)
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Sources of uncertainty in modeled land carbon storage within and across three MIPs : Diagnosis with three new techniques
- 2018
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Ingår i: Journal of Climate. - 0894-8755. ; 31:7, s. 2833-2851
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial carbon cycle models have incorporated increasingly more processes as a means to achieve more-realistic representations of ecosystem carbon cycling. Despite this, there are large across-model variations in the simulation and projection of carbon cycling. Several model intercomparison projects (MIPs), for example, the fifth phase of the Coupled Model Intercomparison Project (CMIP5) (historical simulations), Trends in Net Land-Atmosphere Carbon Exchange (TRENDY), and Multiscale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP), have sought to understand intermodel differences. In this study, the authors developed a suite of new techniques to conduct post-MIP analysis to gain insights into uncertainty sources across 25 models in the three MIPs. First, terrestrial carbon storage dynamics were characterized by a three-dimensional (3D) model output space with coordinates of carbon residence time, net primary productivity (NPP), and carbon storage potential. The latter represents the potential of an ecosystem to lose or gain carbon. This space can be used to measure how and why model output differs. Models with a nitrogen cycle generally exhibit lower annual NPP in comparison with other models, and mostly negative carbon storage potential. Second, a transient traceability framework was used to decompose any given carbon cycle model into traceable components and identify the sources of model differences. The carbon residence time (or NPP) was traced to baseline carbon residence time (or baseline NPP related to the maximum carbon input), environmental scalars, and climate forcing. Third, by applying a variance decomposition method, the authors show that the intermodel differences in carbon storage can be mainly attributed to the baseline carbon residence time and baseline NPP (>90% in the three MIPs). The three techniques developed in this study offer a novel approach to gain more insight from existing MIPs and can point out directions for future MIPs. Since this study is conducted at the global scale for an overview on intermodel differences, future studies should focus more on regional analysis to identify the sources of uncertainties and improve models at the specified mechanism level.
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