The Study of Nanostructured Solar Selective Coatings

In this thesis, nanostructured solar selective coatings used in solar thermal collectors are explored. The nanostructured stainless steel-aluminum nitride (SS-AlN) solar selective coating, a typical solar absorber, has been studied in terms of surface morphology, optical characterization, heat treatment and calculation optimization. Additionally, the potential of using the Fe3O4 nanoparticles coating as a solar absorber has been investigated. A green chemical method of co-precipitation is employed to prepare the Fe3O4 nanoparticles. The coating of Fe3O4 nanoparticles is formed on the copper substrate using dip-coating process. The effects of the thickness, substrate roughness and heat treatment on the performance of the Fe3O4 nanoparticles coating have been then analyzed. The nanostructured SS-AlN solar selective coatings were deposited by sputtering on the glass substrates. The detailed structure of the sample as confirmed by the TEM images is as follows: AlN (73nm)/ SS-AlN (LMVF) (20nm)/ SS-AlN (HMVF) (30nm)/ AlN (8nm)/ Cu. The absorptance denoted by a and the emittance denoted by ε are 0.9033 and 0.1317, respectively, as measured by spectrometers. After being annealed below 500°C for 1 hour, the SS-AlN solar selective coating has a higher absorptance and a lower emittance compared to the unannealed sample. Especially when annealed between 200°C and 300°C，its absorptance increases while the emittance decreases, as a result a is 0.9378 and ε is 0.11. However, an annealing process above 500°C was found to cause considerable damage on the SS-AlN samples. By using Matlab’s simulation tool, the structure of SS-AlN solar selective coating is optimized as: SiO2 (40nm)/AlN (30nm)/SS-AlN (f2=0.25, d2=30nm)/SS- AlN (f3=0.33, d3=50nm)/AlN (8nm)/Cu. We found that a double antireflective layer helps to improve the absorptance. The Fe3O4 nanoparticles prepared by co-precipitation are needle-like with an average size estimated around 20 nanometers. With the number of dip times increasing, the thickness of Fe3O4 nanoparticles coating is enhanced which, however, leads to an unfavorable detach of the film. In terms of the effects of substrate roughness, we found that: 1) the Fe3O4 nanoparticles coating bonded better with rough copper substrate; 2) the coating on a polished copper substrate has higher reflectance in infrared region than that on a rough copper substrate, which contributes to reduce thermal emittance. The thermal emittance of the Fe3O4 nanoparticles coating reduces after the heat treatment at 100°C, 200°C, and 300°C. We found that the optical properties of coating have been significantly improved when annealed at 100°C, i.e. a=0.926, ε=0.378. Annealed above 200°C, however, the absorptance of the coating decreases

Benzyldimethyldodecyl ammonium chloride shifts the proliferation of functional genes and microbial community in natural water from eutrophic lake

Benzylalkyldimethylethyl ammonium compounds are pervasive in natural environments and toxic at high concentrations. The changes in functional genes and microbial diversity in eutrophic lake samples exposed to benzyldimethyldodecyl ammonium chloride (BAC) were assessed. BAC exerted negative effects on bacteria abundance, particularly at concentrations of 100 mu g L-1 and higher. A significant increase in the number of the quaternary ammonium compound-resistant gene qacA/B was recorded within the 10 mu g L-1 treatment after the first day of exposure. Not all antibiotic resistance genes increased in abundance as the concentrations of BAC increased; rather, gene abundances were dependent on the gene type, concentrations of BAC, and contact time. The nitrogen fixation-related gene nifH and ammonia monooxygenase gene amoA were inhibited by high concentrations of BAC after the first day, whereas an increase of the nitrite reductase gene nirK was stimulated by exposure. Microbial communities within higher treatment levels (1000 and 10 000 mu g L-1 ) exhibited significantly different community composition compared to other treatment levels and the control. Selective enrichment of Rheinheimera, Pseudomonas, and Vogesella were found in the higher treatment levels, suggesting that these bacteria have some resistance or degradation capacity to BAC. Genes related with RNA processing and modification, transcription, lipid transport and metabolism, amino acid transport and metabolism, and cell motility of microbial community function were involved in the process exposed to the BAC stress. (C) 2018 Elsevier Ltd. All rights reserved.</p

The roles of environmental variation and spatial distance in explaining diversity and biogeography of soil denitrifying communities in remote Tibetan wetlands

The relative importance of local environments and dispersal limitation in shaping denitrifier community structure remains elusive. Here, we collected soils from 36 riverine, lacustrine and palustrine wetland sites on the remote Tibetan Plateau and characterized the soil denitrifier communities using high-throughput amplicon sequencing of the nirS and nirK genes. Results showed that the richness of nirS-type denitrifiers in riverine wetlands was significantly higher than that in lacustrine wetlands but not significantly different from that in palustrine wetlands. There was no clear distinction in nir community composition among the three kinds of wetlands. Irrespective of wetland type, the soil denitrification rate was positively related to the abundance, but not the α-diversity, of denitrifying communities. Soil moisture, carbon availability and soil temperature were the main determinants of diversity [operational taxonomic unit (OTU) number] and abundance of thenirS-type denitrifier community, while water total organic carbon, soil NO3- and soil moisture were important in controlling nirK-type denitrifier diversity and abundance. The nirS community composition was influenced by water electrical conductivity, soil temperature and water depth, while the nirK community composition was affected by soil electrical conductivity. Spatial distance explained more variation in the nirS community composition than in the nirK community composition. Our findings highlight the importance of both environmental filtering and spatial distance in explaining diversity and biogeography of soil nir communities in remote and relatively undisturbed wetlands.</p

Chinese herbal medicine Guizhi Fuling Formula for treatment of uterine fibroids : a systematic review of randomized clinical trials

Background: Guizhi Fuling Formula is widely applied for uterine fibroids in China. Many clinical trials are reported. This study assessed the efficacy and safety of Guizhi Fuling Formula for the treatment of uterine fibroids. Methods: PubMed, Cochrane CENTRAL, EMBASE, and four Chinese databases were searched through May 2013. We included randomised controlled trials (RCTs) that tested Guizhi Fuling Formula for uterine fibroids, compared with no intervention, placebo, pharmaceutical medication, or other Chinese patent medicines approved by the State Food and Drug Administration of China. Authors extracted data and assessed the quality independently. We applied RevMan 5.2.0 software to analyse data of included randomised trials. Results: A total of 38 RCTs involving 3816 participants were identified. The methodological quality of the included trials was generally poor. Meta-analyses demonstrated that Guizhi Fuling Formula plus mifepristone were more effective than mifepristone alone in reducing the volume of fibroids (in total volume of multiple fibroids, MD −19.41 cm3, 95% CI −28.68 to −10.14; in average volume of multiple fibroids, MD −1.00 cm3, 95% CI −1.23 to −0.76; in average volume of maximum fibroids, MD −3.35 cm3, 95% CI −4.84 to −1.87, I2 = 93%, random effects model). Guizhi Fuling Formula significantly improved symptoms of dysmenorrhea either when it was used alone (RR 2.27, 95% CI 1.04 to 4.97) or in combination with mifepristone (RR 2.35, 95% CI 1.15 to 4.82). No serious adverse events were reported. Conclusions: Guizhi Fuling Formula appears to have additional benefit based on mifepristone treatment in reducing volume of fibroids. However, due to high risk of bias of the trials, we could not draw confirmative conclusions on its benefit. Future clinical trials should be well-designed and avoid the issues that are identified in this study

Microplastics provide new microbial niches in aquatic environments

Microplastics in the biosphere are currently of great environmental concern because of their potential toxicity for aquatic biota and human health and association with pathogenic microbiota. Microplastics can occur in high abundance in all aquatic environments, including oceans, rivers and lakes. Recent findings have highlighted the role of microplastics as important vectors for microorganisms, which can form fully developed biofilms on this artificial substrate. Microplastics therefore provide new microbial niches in the aquatic environment, and the developing biofilms may significantly differ in microbial composition compared to natural free-living or particle-associated microbial populations in the surrounding water. In this article, we discuss the composition and ecological function of the microbial communities found in microplastic biofilms. The potential factors that influence the richness and diversity of such microbial microplastic communities are also evaluated. Microbe-microbe and microbe-substrate interactions in microplastic biofilms have been little studied and are not well understood. Multiomics tools together with morphological, physiological and biochemical analyses should be combined to provide a more comprehensive overview on the ecological role of microplastic biofilms. These new microbial niches have so far unknown consequences for microbial ecology and environmental processes in aquatic ecosystems. More knowledge is required on the microbial community composition of microplastic biofilms and their ecological functions in order to better evaluate consequences for the environment and animal health, including humans, especially since the worldwide abundance of microplastics is predicted to dramatically increase

Fate of tetracycline and sulfonamide resistance genes in a grassland soil amended with different organic fertilizers

This study provided an assessment of the environmental fate of antibiotic resistance genes (ARGs) in a Scottish grassland field repeatedly treated with different organic fertilizers. The impacts of manure, biosolids and municipal food-derived compost on the relative abundances of tetracycline ARGs (tetA, tetB, tetC, tetG and tetW), sulfonamide ARGs (sul1 and sul2) and class 1 integron-integrase gene (IntI1) in soils were investigated, with inorganic fertilizer (NPK) as a comparison. The background soil with a history of low intensity farming showed a higher total relative abundance of tet ARGs over sul ARGs, with tetracycline efflux genes occurring in a higher frequency. In all treatments, the relative abundances of most ARGs detected in soils decreased over time, especially IntI1 and tet ARGs. This general attenuation of soil ARGs is a reflection of changes in the soil microbial community, which is supported by the result that almost all the soils at the end of the experiment had different bacterial communities from the untreated soil at the beginning of the experiment. Multiple applications of organic fertilizers to some extent counteracted the decreasing trend of soil ARGs relative abundances, which resulted in higher ARGs relative abundances in comparison to NPK, either by a lesser decrease of IntI1 and tet ARGs or an increase of sul ARGs. The enhancement of existing soil ARG prevalence by organic fertilizers was strongly dependent on the organic fertilizer type and the particular ARG. Compost contained the lowest relative abundance of inherent ARGs and had the least effect on the soil ARG decrease after application. The relative increase of tet ARGs caused by biosolids was larger than that of sul ARGs, while manure caused the opposite effect. Fertilization practices did not exert effective impacts on the soil bacterial community, although it caused significant changes in the profile of the ARG pool. Organic fertilization may thus accelerate the dissemination of ARGs in soil mainly through horizontal gene transfer (HGT), consistent with the enrichment of IntI1 in organic fertilized soils

Water Vapor Near-UV Absorption: Laboratory Spectrum, Field Evidence, and Atmospheric Impacts

Absorption of solar radiation by water vapor in the near-UV region is a poorly-understood but important issue in atmospheric science. To better understand water vapor near-UV absorption, we constructed a cavity ring-down spectrometer with bandwidth of 5 cm-1 (~0.05 nm) and obtained water vapor absorption cross-sections at 1 nm increments in the 290-350 nm region. Water vapor displays structured absorption over this range with maximum and minimum cross-sections of 8.4×10-25 and 1.6×10-25 cm2/molecule. Major water vapor absorption bands were observed at 293-295, 307-313, 319, 321-322, and 325 nm, with cross-section values higher than 4.0×10-25 cm2/molecule. To obtain further insight into major water vapor absorption bands, we measured water vapor absorption cross-sections at 0.05 nm intervals in the 292-296, 306-314, and 317-326 nm region. Field UV residual spectra not only exhibited increased attenuation at higher atmospheric water vapor loadings but also showed structures suggested by the laboratory water vapor absorption spectrum. Spaceborne UV radiance spectra have spectral structures resembling the differential cross-section spectrum constructed from the laboratory wavelength-dependent water vapor absorption cross-sections presented here. Incorporating water vapor absorption cross-section data into a radiative transfer model yielded an estimated energy budget of 0.26 W/m2 for the standard U.S. atmosphere and 0.76 W/m2 for the tropics. This shows that water vapor near-UV absorption is an important contributor for climate simulation and ozone retrievals

Health risk ranking of antibiotic resistance genes in the Yangtze River

Antibiotic resistance is an escalating global health concern, exacerbated by the pervasive presence of antibiotic resistance genes (ARGs) in natural environments. The Yangtze River, the world's third-longest river, traversing areas with intense human activities, presents a unique ecosystem for studying the impact of these genes on human health. Here, we explored ARGs in the Yangtze River, examining 204 samples from six distinct habitats of approximately 6000 km of the river, including free-living and particle-associated settings, surface and bottom sediments, and surface and bottom bank soils. Employing shotgun sequencing, we generated an average of 13.69 Gb reads per sample. Our findings revealed a significantly higher abundance and diversity of ARGs in water-borne bacteria compared to other habitats. A notable pattern of resistome coalescence was observed within similar habitat types. In addition, we developed a framework for ranking the risk of ARG and a corresponding method for calculating the risk index. Applying them, we identified water-borne bacteria as the highest contributors to health risks, and noted an increase in ARG risks in particle-associated bacteria correlating with heightened anthropogenic activities. Further analysis using a weighted ARG risk index pinpointed the Chengdu–Chongqing and Yangtze River Delta urban agglomerations as regions of elevated health risk. These insights provide a critical new perspective on ARG health risk assessment, highlighting the urgent need for strategies to mitigate the impact of ARGs on human health and to preserve the ecological and economic sustainability of the Yangtze River for future human use.</p