| 61. |
- Li, Kunyang, et al.
(författare)
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Concentrations, Possible Sources and Health Risk of Heavy Metals in Multi-Media Environment of the Songhua River, China
- 2020
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metal pollution in the river environment has been a source of widespread interest due to potential threats to human health and ecosystem security. Many studies have looked at heavy metal pollution in the context of single source-pathway-receptor relationships, however few have sought to understand pollution from a more wholistic multi-media perspective. To investigate potential risks in a more wholistic way, concentrations of six heavy metals (Cd, Cr, Ni, Cu, Zn and Pb) were detected in multi-media (water, sediment and riparian soil) collected from 14 sampling sites in the main stream of the Songhua River. Chemical analyses indicated that the average concentration of heavy metals in water followed: Zn > Cr > Cu > Pb > Ni > Cd, with a different trend observed in sediments and riparian soil: Zn > Cr > Ni > Pb > Cu > Cd. The potential risk was evaluated using the heavy metal pollution index (HPI), Nemerow pollution index (P-N), hazard index (HI) and carcinogenic risk (CR) metrics. Results showed that all HPI values were lower than the critical level of 100 indicating that the levels of these targeted heavy metals were within drinking water safety limits. The P-N indicated that both sediment (2.64) and soil (2.95) could be considered "moderately polluted", with Cd and Zn providing the most significant contributions. A human health risk assessment suggested that the non-carcinogenic risks were within acceptable levels (HI < 1), as was the cancer risk associated with dermal adsorption (CR <10(-6)). However, the CR associated with ingestion exposure (4.58 x 10(-6)) exceeded the cancer risk threshold (10(-6)) indicative of elevated cancer incidence in exposed populations. Health-risk estimates were primarily associated with Cd in the Songhua River. Source apportionment was informed by Pearson correlation analysis coupled with principal component analysis (PCA) which indicated that Cu was mainly derived from natural (geogenic) sources; Cr and Ni were associated with industrial emissions; Pb might be derived from agricultural and transportation sources; Zn might be from industrial, agricultural activities and transportation; while Cd is likely from industrial and agricultural emissions. The source apportionment information could provide the basis for a risk-management strategy focused on reducing Cd and Zn emissions to the riverine environment. Results from this study will provide the scientific knowledge that is needed for measuring and controlling heavy metals sources and pollution characteristics, and identifying the potential cancer risk with different exposure pathways, as well as making effective environmental management policies at catchment or regional scales.
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| 62. |
- Li, Qiang, et al.
(författare)
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Microbial Necromass, Lignin, and Glycoproteins for Determining and Optimizing Blue Carbon Formation
- 2024
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 58, s. 468-479
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Tidskriftsartikel (refereegranskat)abstract
- Coastal wetlands contribute to the mitigation of climate change through the sequestration of “blue carbon”. Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (FeSRO). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.
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| 63. |
- Liu, Qiang, et al.
(författare)
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Effect of cooling rate and Ti addition on the microstructure and mechanical properties in as-cast condition of hypereutectic high chromium cast irons
- 2012
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 52:12, s. 2210-2219
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Tidskriftsartikel (refereegranskat)abstract
- The effect of cooling rate and Ti additions on the mechanical properties and carbides characteristics such as morphology, size distribution and composition was studied in high-chromium cast irons containing Fe-17 mass%Cr-4 mass%C. Based on the size distribution, composition and morphology, M 7C3 type carbides were roughly classified into "primary M7C3 carbides" and "eutectic M7C3 carbides" with a 11.2μ m border size. Thereafter, the change of the solidification structure and especially the refinement of carbides size were determined. It was found that both the size and number values should be summarized systematically for primary M 7C3 carbides and eutectic M7C3 carbides, respectively. Also, TiC carbides with a high formation temperature can not only act as a nuclei of M7C3 carbides, but they also contain a Ti(C, N) core. In the as-cast condition, the bulk hardness of the cast irons increases with an increased Ti content. In addition, the wear loss increases with an increased Ti content. Neither the bulk hardness nor the wear loss did change too much with an increased cooling rate.
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| 64. |
- Liu, Qiang, et al.
(författare)
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Effect of heat treatment on microstructure and mechanical properties of Ti-alloyed hypereutectic high chromium cast iron
- 2012
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 52:12, s. 2288-2294
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Tidskriftsartikel (refereegranskat)abstract
- The effect of heat treatment on the microstructure and mechanical properties of Ti-alloyed hypereutectic High Chromium Cast Iron (HCCI) containing Fe-17 mass%Cr-4 mass%C-1.5 mass%Ti was investigated. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It was found that the number of fine secondary M7C3 carbides with a size below 1 μm increases with lower holding temperatures and shorter holding times during heat treatment. The number of coarse primary M7C 3 carbides with a size above 11.2 μm increases with increasing holding temperatures and longer holding times. In addition, the number of TiC carbides increases with increasing holding times, and martensite units are more refined at longer holding times and lower holding temperatures, respectively. Moreover, the volume fraction of martensite increases with increased holding times. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.
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| 65. |
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| 66. |
- Liu, Shuyu, et al.
(författare)
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Demographic History and Natural Selection Shape Patterns of Deleterious Mutation Load and Barriers to Introgression across Populus Genome
- 2022
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Ingår i: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 39:2
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Tidskriftsartikel (refereegranskat)abstract
- Hybridization and resulting introgression are important processes shaping the tree of life and appear to be far more common than previously thought. However, how the genome evolution was shaped by various genetic and evolutionary forces after hybridization remains unresolved. Here we used whole-genome resequencing data of 227 individuals from multiple widespread Populus species to characterize their contemporary patterns of hybridization and to quantify genomic signatures of past introgression. We observe a high frequency of contemporary hybridization and confirm that multiple previously ambiguous species are in fact F1 hybrids. Seven species were identified, which experienced different demographic histories that resulted in strikingly varied efficacy of selection and burdens of deleterious mutations. Frequent past introgression has been found to be a pervasive feature throughout the speciation of these Populus species. The retained introgressed regions, more generally, tend to contain reduced genetic load and to be located in regions of high recombination. We also find that in pairs of species with substantial differences in effective population size, introgressed regions are inferred to have undergone selective sweeps at greater than expected frequencies in the species with lower effective population size, suggesting that introgression likely have higher potential to provide beneficial variation for species with small populations. Our results, therefore, illustrate that demography and recombination have interplayed with both positive and negative selection in determining the genomic evolution after hybridization.
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| 67. |
- Liu, Zhiying, et al.
(författare)
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Solution-Processable Nanotube/Polymer Composite for High-Performance TFTs
- 2011
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:9, s. 1299-1301
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Tidskriftsartikel (refereegranskat)abstract
- Thin-film field-effect transistors (TFTs) are readily fabricated using a semiconductor composite that is solution processed under ambient conditions for the conduction channel. The composite comprises single-walled carbon nanotubes (SWCNTs) embedded in poly-9,9' dioctyl-fluorene-co-bithiophene. Carrier mobility values approaching 10 cm(2)V(-1)s(-1) are obtained for the composite with relatively high SWCNT concentrations. When the SWCNT concentration is reduced for a large ON/OFF current ratio > 10(6), the mobility remains decent around 0.3 cm(2)V(-1)s(-1). The resultant TFTs display remarkable environmental and operational reliability. Nanotube-based composites are therefore of significance in printed electronics owing to their simplicity in device fabrication and competitiveness in device performance.
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| 68. |
- Lopez Cabezas, Ana, 1980-, et al.
(författare)
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Influence of Carbon Nanotubes on Thermal Stability of Water-Dispersible Nanofibrillar Polyaniline/Nanotube Composite
- 2012
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Ingår i: Materials. - Basel, Switzerland : MDPI AG. - 1996-1944. ; 5:2, s. 327-335
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Tidskriftsartikel (refereegranskat)abstract
- Significant influence on the thermal stability of polyaniline (PANI) in the presence of multi-walled carbon nanotubes (MWCNTs) is reported. By means of in-situ rapid mixing approach, water-dispersible nanofibrillar PANI and composites, consisting of MWCNTs uniformly coated with PANI in the state of emeraldine salt, with a well-defined core-shell heterogeneous structure, were prepared. The de-protonation process in PANI occurs at a lower temperature under the presence of MWCNTs on the polyaniline composite upon thermal treatment. However, it is found that the presence of MWCNTs significantly enhances the thermal stability of PANI's backbone upon exposure to laser irradiation, which can be ascribed to the core-shell heterogeneous structure of the composite of MWCNTs and PANI, and the high thermal conductivity of MWCNTs.
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| 69. |
- Lu, Zhengyao, et al.
(författare)
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Impacts of Large-Scale Sahara Solar Farms on Global Climate and Vegetation Cover
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 48:2
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale photovoltaic solar farms envisioned over the Sahara desert can meet the world's energy demand while increasing regional rainfall and vegetation cover. However, adverse remote effects resulting from atmospheric teleconnections could offset such regional benefits. We use state-of-the-art Earth-system model simulations to evaluate the global impacts of Sahara solar farms. Our results indicate a redistribution of precipitation causing Amazon droughts and forest degradation, and global surface temperature rise and sea-ice loss, particularly over the Arctic due to increased polarward heat transport, and northward expansion of deciduous forests in the Northern Hemisphere. We also identify reduced El Niño-Southern Oscillation and Atlantic Niño variability and enhanced tropical cyclone activity. Comparison to proxy inferences for a wetter and greener Sahara ∼6,000 years ago appears to substantiate these results. Understanding these responses within the Earth system provides insights into the site selection concerning any massive deployment of solar energy in the world's deserts.
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| 70. |
- Makafe, Gaelle G., et al.
(författare)
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Quinoline Derivatives Kill Mycobacterium tuberculosis by Activating Glutamate Kinase
- 2019
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Ingår i: Cell Chemical Biology. - : CELL PRESS. - 2451-9456 .- 2451-9448. ; 26:8, s. 1187-
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Tidskriftsartikel (refereegranskat)abstract
- There is a great need for identification and development of new anti-tuberculosis drugs with novel targets. Recent drug-discovery efforts typically focus on identifying inhibitors but not activators that perturb metabolic enzymes' functions as a means to kill Mycobacterium tuberculosis (Mtb). Here, we describe a class of quinoline compounds, Z0933/Z0930, which kill Mtb by acting as activators of glutamate kinase (GK), a previously untargeted enzyme catalyzing the first step of proline biosynthesis. We further show that Z0933/Z0930 augment proline production and induce Mtb killing via proline-derived redox imbalance and production of reactive oxygen species. This work highlights the effectiveness of gain-of-function probes against Mtb and provides a framework for the discovery of next-generation allosteric activators of GK.
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