| 93981. |
- Shi, Yali, et al.
(författare)
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Human Exposure and Elimination Kinetics of Chlorinated Polyfluoroalkyl Ether Sulfonic Acids (Cl-PFESAs)
- 2016
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 50:5, s. 2396-2404
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Tidskriftsartikel (refereegranskat)abstract
- The incomplete mass-balance of organic fluorine in human serum indicates the existence of unknown per- and polyfluoroalkyl substances (PFASs) with persistent and bioaccumulative properties. Here we characterized human exposure and elimination kinetics of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in metal plating workers (n = 19), high fish consumers (n = 45), and background controls (n = 8). Cl-PFESAs were detected in >98% of the sampled individuals with serum concentrations ranging <0.019-5040 ng/mL. Statistically higher median serum levels were observed in high fish consumers (93.7 ng/mL) and metal plating workers (51.5 ng/mL) compared to the background control group (4.78 ng/mL) (Kruskal Wallis rank sum test, p < 0.01). Cl-PFESAs could account for 0.269 to 93.3% of Sigma PFASs in human serum indicating that this compound class may explain a substantial fraction of previously unidentified organic fluorine in the Chinese population. Estimated half-lives for renal clearance (median 280 years; range 7.1-4230 years) and total elimination (median 15.3 years; range 10.1-56.4 years) for the eight carbon Cl-PFESA suggest that this is the most biopersistent PFAS in humans reported to date. The apparent ubiquitous distribution and slow elimination kinetics in humans underscore the need for more research and regulatory actions on Cl-PFESAs and PFAS alternatives with similar chemical structures.
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| 93982. |
- Shi, Yali, et al.
(författare)
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Probing the Differential Tissue Distribution and Bioaccumulation Behavior of Per- and Polyfluoroalkyl Substances of Varying Chain-Lengths, Isomeric Structures and Functional Groups in Crucian Carp
- 2018
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:8, s. 4592-4600
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the bioaccumulation mechanisms of per- and polyfluoroalkyl substances (PFASs) across different chain-lengths, isomers and functional groups represents a monumental scientific challenge with implications for chemical regulation. Here, we investigate how the differential tissue distribution and bioaccumulation behavior of 25 PFASs in crucian carp from two field sites impacted by point sources can provide information about the processes governing uptake, distribution and elimination of PFASs. Median tissue/blood ratios (TBRs) were consistently <1 for all PFASs and tissues except bile which displayed a distinct distribution pattern and enrichment of several perfluoroalkyl sulfonic acids. Transformation of concentration data into relative body burdens (RBBs) demonstrated that blood, gonads, and muscle together accounted for >90% of the amount of PFASs in the organism. Principal component analyses of TBRs and RBBs showed that the functional group was a relatively more important predictor of internal distribution than chain length for PFASs. Whole body bioaccumulation factors (BAFs) for short-chain PFASs deviated from the positive relationship with hydrophobicity observed for longer-chain homologues. Overall, our results suggest that TBR, RBB, and BAF patterns were most consistent with protein binding mechanisms although partitioning to phospholipids may contribute to the accumulation of long-chain PFASs in specific tissues.
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| 93983. |
- Shi, Yali, et al.
(författare)
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Tissue Distribution and Whole Body Burden of the Chlorinated Polyfluoroalkyl Ether Sulfonic Acid F-53B in Crucian Carp (Carassius carassius) : Evidence for a Highly Bioaccumulative Contaminant of Emerging Concern
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:24, s. 14156-14165
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Tidskriftsartikel (refereegranskat)abstract
- Following the global actions to phase out perfluoroctanesulfonic acid (PFOS) a large number of alternative per- and polyfluoroalkyl substances, with poorly defined hazard properties, are being used in increasing quantities. Here, we report on the first detection of the chlorinated polyfluoroalkyl ether sulfonic acid F-53B in biological samples and determine the tissue distribution and whole body bioaccumulation factors (BAF(whole body)) in crucian carp (Carassius carassius). Analysis of fish samples from Xiaoqing River (XR) and Tangxun Lake (TL) demonstrated a similar level of F-53B contamination with median concentrations in blood of 41.9 and 20.9 ng/g, respectively. Tissue/blood ratios showed that distribution of F-53B primarily occurs to the kidney (TL: 0.48, XR: 0.54), gonad (TL: 0.36, XR: 0.54), liver (TL: 0.38, XR: 0.53), and heart (TL: 0.47, XR: 0.47). Median Log BAF(whole body) values for F-53B (XR: 4.124, TL: 4.322) exceeded regulatory bio accumulation criterion and were significantly higher than those of PFOS in the same data sets (XR: 3.430, TL: 3.279). On the basis of its apparent omnipresence and strong bioaccumulation propensity, it is hypothesized that F-53B could explain a significant fraction of previously unidentified organofluorine in biological samples from China, and regulatory actions for this compound are encouraged.
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| 93984. |
- Shi, Yan-Yan, et al.
(författare)
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Crystalline Self-Assembly of a Bowl-Like Cyclotriguaiacylene Derivative with Alcohol/Phenols by Hydrogen Bonding and C-H center dot center dot center dot pi Interactions : The Self-Inclusion Extended Organic Frameworks
- 2010
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:1, s. 314-320
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Tidskriftsartikel (refereegranskat)abstract
- Bowl-like tris-[(N-methyl-2-imidazoyl)]methoxy]cyclotriguaiacyclene (TMIM-CTG) (1) was synthesized and cocrystallized with ethanol, resorcinol, and phloroglucinol to afford three molecular complexes (TMIM-CTG)-(ethanol)(3) (2), (TMIM-CTG)-(resorcinol)-(CH3CN)(2) (3), and (TMIM-CTG)-(phloroglucinol)center dot(CH3CN)(2) (4), whose Structures have been determined by X-ray single crystal analysis. Except for the hydrogen bonds between imidazole of 1 and the hydroxyl group of alcohol/phenols (O-H center dot center dot center dot N), all crystals contain self-inclusion motifs with cooperative C-H center dot center dot center dot pi, interactions which can be considered as the secondary way to extend the primary hydrogen-bonded networks to (lie frameworks with higher levels. In complex 2. two adjacent TMIM-CTGs form a self-clasping dimer by an edge-to-face C-H center dot center dot center dot pi interaction between the imidazole ring and the benzene ring of CTG, which is further extended to a one-dimensional chain by the pi-pi. interactions between adjacent imidazole rings. The ethanol molecules interact with TMIM-CTGs by hydrogen bonding and fill channels within these chains. In complex 3, the self-assembly of TMIG-CTG and resorcinol Molecules by hydrogen bonding affords the Zigzag chain, which is then extended to the (4.4) sheet by the self-inclusion between TMIG-CTGs. Complex 4 contains a two-dimensional 4.8(2) hydrogen-bonding network betweenTMIG-CTG and phloroglucinol molecules, and the self-inclusion Of TMIG-CTGs extends it to,I novel three-dimensional supramolecular framework. The acetonitrile molecules in two latter Crystals arc included within the extended organic framework.
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| 93985. |
- Shibanov, Yu. A., et al.
(författare)
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Optical identification of the 3C 58 pulsar wind nebula
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 486:1, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Context: The Crab-like supernova remnant 3C 58 contains the young pulsar PSR J0295+6449, which powers a radio plerion and a compact torus-like pulsar wind nebula visible in X-rays. Aims: We have performed deep optical imaging of the 3C 58 field to detect the optical counterpart of the pulsar and its wind nebula. Methods: The imaging was carried out with the Nordic Optical Telescope. We also analyzed the archival images of the field obtained with the Chandra/ACIS-S and HRC-S in X-rays and with the Spitzer/IRAC in the mid-infrared. Results: We detect a faint extended elliptical optical object with B=24.06 m ± 0.08 and V=23.11 m ± 0.04, whose center and peak brightness position are consistent at the sub-arcsecond level with the position of the pulsar. The morphology of the object and the orientation of its major axis are in excellent agreement with the torus region of the pulsar wind nebula seen almost edge on in the X-rays, although its extension is only about a half of what is in X-rays. This suggests that in the optical we see only the brightest central part of the torus nebula with the pulsar. The position and morphology of the object are also practically identical to the counterpart of the torus region recently detected in the mid-infrared bands. We do not resolve any point-like source within the nebula that could be identified with the pulsar and estimate that the contribution of the pulsar to the observed optical flux is ⪉10%. Using the archival Chandra/ACIS-S data we analyzed the spectrum of the pulsar+nebula X-ray emission extracted from the spatial region constrained by the optical/infrared source position and extent and find that a single absorbed power law provides an acceptable spectral fit. Combining this fit with the optical and infrared fluxes of the detected candidate torus nebula counterpart, we compile a tentative multi-wavelength spectrum of the central part of the pulsar nebula. Within the uncertainties of the interstellar extinction towards 3C 58, it is reminiscent of either the Crab or PSR B0540-69 pulsar wind nebula spectra. Conclusions: The position, morphology, and spectral properties of the detected source strongly suggest that it is the optical/mid-infrared counterpart of the 3C 58 pulsar + its wind nebula system. This makes 3C 58 the third member, together with the Crab and PSR B0540-69, of such a system as identified in the optical and mid-infrared.
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| 93986. |
- Shibanov, Yu. A., et al.
(författare)
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The near-UV pulse profile and spectrum of the pulsar PSR B0656+14
- 2005
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 440, s. 693-700
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Tidskriftsartikel (refereegranskat)abstract
- We have observed the middle-aged pulsar PSR B0656+14 with the prism and the NUV MAMA detector of the Space Telescope Imaging Spectrograph (STIS) to measure the pulsar spectrum and periodic pulsations in the near-ultraviolet (NUV). The pulsations are clearly detected, double-peaked and very similar to the optical pulse profile. The NUV pulsed fraction is 70±12%. The spectral slope of the dereddened phase-integrated spectrum in the ~1800-3200 Å range is ~αν=0.35±0.5 which together with the high pulse fraction indicates a non-thermal origin for the NUV emission. The total flux in the range ~1700-3400 Å is estimated to be 3.4±0.3×10-15 erg s-1 cm-2 when corrected for E(B-V)=0.03 mag. At a distance of 288 pc this corresponds to a luminosity LNUV=3.4×1028 erg s-1 assuming isotropy of the emission. We compare the NUV pulse profile with observations from radio to gamma-rays. The first NUV sub-pulse is in phase with the gamma-ray pulse marginally detected with EGRET, while the second NUV sub-pulse is similar both in shape and in phase with the non-thermal pulse in hard X-rays. This indicates a single origin of the non-thermal emission in the optical-NUV and in the X-rays. This is also supported by the observed NUV spectral slope, which is compatible with a blackbody plus power-law fit extended from the X-ray range, but dominated by the power-law component in most of the NUV range.
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| 93987. |
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| 93988. |
- Shibley, Nicole C., et al.
(författare)
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Analysis of Acoustic Observations of Double-Diffusive Finestructure in the Arctic Ocean
- 2020
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 47:18
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Tidskriftsartikel (refereegranskat)abstract
- Double-diffusive convection may occur if both temperature and salinity increase with depth, as in the Arctic Ocean. The process is identifiable by a staircase structure, with mixed layers separated by high-gradient interfaces in temperature and salinity. These staircases, which persist if turbulence levels are weak, are widely present in the Arctic Ocean and responsible for transporting heat toward the overlying sea ice. Acoustic observations (reflection coefficients) from a broadband echo sounder are analyzed here to track the detailed evolution of interfaces in the Arctic's double-diffusive staircase. We infer interface thicknesses from reflection coefficient profiles and find that thicknesses appear to be related to water column displacements. Further, we relate reflection coefficients to interface stratification and interpret stratification changes in the context of turbulence acting to thicken interfaces. The high-resolution capabilities of the echo sounder allow for insights into how double-diffusive heat fluxes and inferred mixing levels may vary in space/time.
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| 93989. |
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| 93990. |
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