RESUMEN

The defluoroborylation of fluoroarenes by chromium-catalyzed cleavage of unactivated C-F bonds is described. The reaction uses HBpin as the boron source, low-cost and commercially available chromium salt as the precatalyst, and terpyridine as a crucial ligand, providing a protocol with atom-efficient benefits and a wide range of applicable substrates for the functionalization of aryl C-F bonds. Preliminary mechanistic studies indicate that an unprecedented Cr-catalyzed magnesiation of the unactivated C-F bond occurred. The generated arylmagnesium intermediates then participated in the subsequent borylation reaction. The application of the strategy in the preparation of valuable derivatives is demonstrated by the late-stage functionalization of boronate ester groups.

RESUMEN

BACKGROUND: Frogs are critical economic animals essential to agricultural ecosystem equilibrium. However, Meningitis-like Infectious Disease (MID) often affects them in agricultural settings. While frog-associated microbiota contribute to elemental cycling and immunity, the effects of frog sex and health on gut bacteria remain understudied, and the relationship between frog habitat and soil microbes is unclear. We aimed to determine how frog sex, health status and habitat influence symbiotic bacteria and community assembly mechanism to provide guidance for sustainable frog farming and conservation. RESULTS: We employed 16S rRNA sequencing to investigate gut microbiota differences in relation to frog sex and health status. We also compared symbiotic communities in frog-aggregation, native and soybean soil on the farm. Results showed that gut bacterial ß-diversity and taxonomy were markedly influenced by frog sex and health. Healthy frogs had more robust gut bacterial metabolism than frogs infected with MID. Cooccurrence network analysis revealed that healthy female frogs had more complex microbial network structure than males; however, diseased males showed the greatest network complexity. The assembly mechanism of gut bacteria in male frogs was dominated by deterministic processes, whereas in female frogs it was dominated by stochastic processes. Among symbiotic bacteria in frog habitat soils, deterministic processes predominantly shaped the community assembly of soybean soil. In particular, soybean soil was enriched in pathogens and nitrogen functions, whereas frog-aggregation soil was markedly increased in sulphur respiration and hydrocarbon degradation. CONCLUSION: Our study reveals that sex mainly alters the interaction network and assembly mechanism of frog intestinal bacteria; MID infection significantly inhibits the metabolic functions of intestinal bacteria. Furthermore, diverse frog habitat soils could shape more symbiotic bacteria to benefit frog farming. Our findings provide new horizons for symbiotic bacteria among frogs, which could contribute to sustainable agriculture and ecological balance.

Asunto(s)

RESUMEN

For the purpose of obtaining the smaller uncertainties for Hp(3) and Dp lens in 90Sr/90Y beta reference fields, a new dose determination method based on the Monte-Carlo simulation was proposed. The conversion coefficients from the absorbed dose in air, at the reference point of the extrapolation ionisation chamber, Dair, det to Hp(3; α) and the conversion factors from Dair, det to Dp lens(α) were calculated with EGSnrc, respectively, for the irradiation angles from 0° to 60°. Compared with the dose determination method in International Organization for Standardization (ISO) 6980 standard, the uncertainty reductions of 7.7-52.8% for Hp(3; α) and 7.9-55.0% for Dp lens(α) were achieved, respectively. In addition, for the conversion coefficients from the reference absorbed dose DR to Hp(3; α), the calculations were performed for more irradiation conditions, which are not included in the current ISO 6980 standard. For the calculations of the conversion factors from DR to Dp lens(α), the eye and head phantoms with Chinese characteristics were utilised, which makes the conversion factors more suitable for use in China.

Asunto(s)

RESUMEN

Advances in DNA sequencing technologies have drastically changed our perception of the structure and complexity of the plant microbiome. By comparison, our ability to accurately identify the metabolically active fraction of soil microbiota and its specific functional role in augmenting plant health is relatively limited. Important ecological interactions being performed by microbes can be investigated by analyzing the extracellular protein fraction. Here, we combined a unique protein extraction method and an iterative bioinformatics pipeline to capture and identify extracellular proteins (metaexoproteomics) synthesized in the rhizosphere of Brassica spp. We first validated our method in the laboratory by successfully identifying proteins related to a host plant (Brassica rapa) and its bacterial inoculant, Pseudomonas putida BIRD-1. This identified numerous rhizosphere specific proteins linked to the acquisition of plant-derived nutrients in P. putida. Next, we analyzed natural field-soil microbial communities associated with Brassica napus L. (oilseed rape). By combining metagenomics with metaexoproteomics, 1,885 plant, insect, and microbial proteins were identified across bulk and rhizosphere samples. Metaexoproteomics identified a significant shift in the metabolically active fraction of the soil microbiota responding to the presence of B. napus roots that was not apparent in the composition of the total microbial community (metagenome). This included stimulation of rhizosphere-specialized bacteria, such as Gammaproteobacteria, Betaproteobacteria, and Flavobacteriia, and the upregulation of plant beneficial functions related to phosphorus and nitrogen mineralization. Our metaproteomic assessment of the "active" plant microbiome at the field-scale demonstrates the importance of moving beyond metagenomics to determine ecologically important plant-microbe interactions underpinning plant health. IMPORTANCE Plant-microbe interactions are critical to ecosystem function and crop production. While significant advances have been made toward understanding the structure of the plant microbiome, learning about its full functional role is still in its infancy. This is primarily due to an incomplete ability to determine in situ plant-microbe interactions actively operating under field conditions. Proteins are the functional entities of the cell. Therefore, their identification and relative quantification within a microbial community provide the best proxy for which microbes are the most metabolically active and which are driving important plant-microbe interactions. Here, we provide the first metaexoproteomics assessment of the plant microbiome using field-grown oilseed rape as the model crop species, identifying key taxa responsible for specific ecological interactions. Gaining a mechanistic understanding of the plant microbiome is central to developing engineered plant microbiomes to improve sustainable agricultural approaches and reduce our reliance on nonrenewable resources.

Asunto(s)

RESUMEN

The use of pinacolborane to borylate abundant vinyl triflates and unactivated aryl carboxylic esters was enabled by chromium catalysis via the selective formation of vinyl and aryl boronate esters. The competing hydrided reduction or allylic borylation proceeds sluggishly or does not occur, therefore providing a selective strategy for the incorporation of boronate into olefins and arenes. Mechanistic studies indicate that the σ-bond metathesis or oxidative addition mechanism may be considered to be responsible for the cleavage of ester scaffolds.

RESUMEN

The exploitation of mineral resources may cause the environmental release of radionuclides and their introduction in the human trophic chain, affecting public health in the short and long term. A case study of the environmental radiation impact from coal mining and germanium processing was carried out in southwest China. The coal mines contain germanium and uranium and have been exploited for more than 40 years. The farmlands around the site of the coal mining and germanium processing have been contaminated by the solid waste and mine water to some extent since then. Samples of crops were collected from contaminated farmlands in the research area. The research area covers a radius of 5 km, in which there are two coal mines. 210Pb and 210Po were analyzed as the key radionuclides during the monitoring program. The average activity concentrations of 210Pb and 210Po in the crops were 1.38 and 1.32 Bq/kg in cereals, 4.07 and 2.19 Bq/kg in leafy vegetables and 1.63 and 1.32 Bq/kg in root vegetables. The annual effective doses due to the ingestion of 210Pb and 210Po in consumed crops were estimated for adult residents living in the research area. The average annual effective dose was 0.336 mSv/a, the minimum was 0.171 mSv/a and the maximum was 0.948 mSv/a. The results show that the crops grown on contaminated farmland contained an enhanced level of radioactivity concentration. The ingestion doses of local residents in the research area were significantly higher than the average level of 0.112 mSv/a in China, and the world average level of 0.042 mSv/a through 210Pb and 210Po in crop intake, respectively.

Asunto(s)

RESUMEN

Conservation tillage is an advanced agricultural technology that seeks to minimize soil disturbance by reducing, or even eliminating tillage. Straw or stubble mulching in conservation tillage systems help to increase crop yield, maintain biodiversity and increase levels of exogenous nutrients, all of which may influence the structure of fungal communities in the soil. Currently, however, the assembly processes and co-occurrence patterns of fungal sub-communities remain unknown. In this paper, we investigated the effects of no-tillage and straw mulching on the composition, assembly process, and co-occurrence patterns of soil fungal sub-communities in a long-term experimental plot (15 years). The results revealed that combine straw mulching with no-tillage significantly increased the richness of fungi but not their diversity. Differential abundance analysis and principal component analysis (PCA) indicated that tillage management had a greater effect on the fungal communities of abundant and intermediate taxa than on the rare taxa. Available phosphorus (AP) and total nitrogen (TN) were the major determinants of fungal sub-communities in NT treatment. The abundant fungal sub-communities were assembled by deterministic processes under medium strength selection, while strong conservation tillage strength shifts the abundant sub-community assembly process from deterministic to stochastic. Overall, the investigation of the ecological network indicated that no-tillage and straw mulching practices decreased the complexity of the abundant and intermediate fungal networks, while not significantly influencing rare fungal networks. These findings refine our knowledge of the response of fungal sub-communities to conservation tillage management techniques and provide new insights into understanding fungal sub-community assembly.

RESUMEN

Iron is among the most abundant elements in the soil of paddy fields, and its valence state and partitioning can be transformed by flooding and drainage alternations. However, little is known about the function of soil microbes that interact with Fe(II). In this study, sandy and loamy soils originating from rice fields were treated with Fe(II) at low and high concentrations. The findings demonstrate that additional Fe(II) has various effects on the soil's microbial community structure and metabolic pathways. We conclude that Fe(II) at high concentrations reduced bacterial abundance and diversity in two textured paddy soils, yet the abundance in loamy soils was higher than it was in sandy soil. Additionally, in environments with high Fe(II) levels, the relative abundance of both anaerobic and chemoautotrophic bacteria increased. The Fe(II) concentration was positively correlated with total reduced substances but negatively correlated with redox potential and pH. Co-occurrence networks revealed that Fe(II) significantly promoted interactions with the most anaerobic and chemoautotrophic bacteria. In addition, adding Fe(II) greatly increased the number of more complex bacterial networks, and an increase in the number of mutually beneficial taxa occurred. We found that Fe(II) promoted the methane pathway, the Calvin cycle, and nitrate reduction to small but significant extents. These pathways involve the growth and interrelation of autotrophic and anaerobic bacteria. These results suggest that changes in the bacterial community structure occur in many dry-wet alternating environments.

RESUMEN

In soil ecosystems, fungi exhibit diverse biodiversity and play an essential role in soil biogeochemical cycling. Fungal diversity and assembly processes across soil strata along altitudinal gradients are still unclear. In this study, we investigated the structure and abundance of soil fungal communities among soil strata and elevational gradients on the Tibetan Plateau using Illumina MiSeq sequencing of internal transcribed spacer1 (ITS1). The contribution of neutral and niche ecological processes were quantified using a neutral community model and a null model-based methodology. Our results showed that fungal gene abundance increased along altitudinal gradients, while decreasing across soil strata. Along with altitudinal gradients, fungal α-diversity (richness) decreased from surface to deeper soil layers, while ß-diversity showed weak correlations with elevations. The neutral community model showed an excellent fit for neutral processes and the lowest migration rate (R2 = 0.75). The null model showed that stochastic processes dominate in all samples (95.55%), dispersal limitations were dominated at the surface layer and decreased significantly with soil strata, while undominated processes (ecological drift) show a contrary trend. The log-normal model and the null model (ßNTI) correlation analysis also neglect the role of niche-based processes. We conclude that stochastic dispersal limitations, together with ecological drifts, drive fungal communities.

RESUMEN

In this work, the conversion coefficients from air kerma to the eye lens dose were calculated for photon exposures using the detailed eye and head Monte-Carlo (MC) model with the Chinese adult parameters. To verify the MC model and the simulation method, the conversion coefficients from fluence to the eye lens dose for mono-energy electrons (0.7-12 MeV) were calculated and compared with other studies. Then the conversion coefficients from air kerma to the doses in the entire lens and in the sensitive volume were calculated, respectively, for mono-energy photons (0.01-50 MeV) at different incidence angles (0-90°, in step of 15°). A small difference was found between the calculated conversion coefficient and the ICRP recommended value. The difference could be mainly due to the difference in their geometry characteristic of the eye and head models. In addition, the uncertainty analysis of the calculated conversion coefficients was performed in detail. The calculated dose conversion coefficient of the eye lens can be used to evaluate the eye lens dose for Chinese occupational staffs in external photon fields. And it can be used to determine the personal absorbed dose in the eye lens Dp lens in photon reference radiation fields.

Asunto(s)

RESUMEN

With the constant surge of strawberry cultivation and human demand, widespread concern has been expressed about the severe soil and plant health problems caused by continuous strawberry cropping, particularly monocropping in greenhouses. Effective microorganisms (EM) and Bacillus subtilis (BS) have been extensively commercialized as biological control agents (BCAs) to promote plant growth and yield enhancement. However, their effects on soil microbes are obscure. To regulate the microbial community in continuous cropping strawberry soils, we developed four soil amendments based on these two BCAs by adding low and high contents of compost. The amplicon sequencing of bacterial and fungal ribosomal markers was applied to study the response of the soil microbiome structure. We noticed a sharp increase in bacterial diversity after adding EM-treated high compost and BS-treated low compost, while there was no significant change in fungal diversity among treatments. Through taxonomic classification and FUNGuild analysis, we found that the application of soil amendments resulted in a significant decline in the relative abundance of fungal plant pathogens (Rhizopus, Penicillium and Fusarium) in the soils; accordingly, the metabolic functions of a range of detrimental fungi were inhibited. Correlation analysis indicated that soil microbial community was indirectly driven by soil physicochemical properties. Co-occurrence networks revealed that soil amendments contributed to the connectivity of bacterial network, and EM-treated with high compost was the most complex and balanced. Collectively, EM-treated high compost and BS-treated low compost can well regulate the microbial community structure and thus maintain soil health.

Asunto(s)

RESUMEN

Radon, known to be a human carcinogen, is one of the most concerned radionuclides in uranium mining which need to be monitored and controlled. A large amount of radon is discharged to the atmosphere mainly through underground ventilation shafts for underground uranium mining. There are many studies on radon release of uranium mine, but the differences of the measured radon results are very big. In this paper, a typical underground uranium mine in China is chosen as a case study. This study finds that distribution of radon concentration and airflow speed inside the ventilation shaft are extremely uneven, but the distributions are respectively stable and regular for a fixed cross-section at the wellhead depth of 0-1 m. There is also a stable numerical relationship between the radon release rate and the product of radon concentration and airflow speed at the center for any cross-section in the shaft. Based on this regulation, a multipoint interpolation-integration method and a one-point method for calculating radon release from underground ventilation shaft are proposed in this paper. The results show that the difference between these two methods is 2-10%, the one-point method is more suitable and convenient to be applied for the long-term monitoring radon release rate from uranium mine ventilation. The research results in this paper can be applied in the estimation of radon release rate for other underground uranium ventilation shafts.

Asunto(s)

RESUMEN

Crude steel production in China made up the majority of the global output, at 49.5% in 2014. High temperature smelting processes result in the release of natural radionuclides, including radon gas and other air pollutants into the atmosphere. This paper conducts an analysis of the raw materials, end products and flue gas sampled from an integrated steel plant from within China's Jiangxi Province, with annual production of 8.50 Mt of crude steel. Normalized stack emissions factors of radionuclides from steel production were first reported in China. The results showed that sintering was the main process that released natural radionuclides, and the main radionuclides released into the atmosphere were 222Rn (86.4 GBq/Mt), 210Pb (13.4 GBq/Mt), and 210Po (1.71 GBq/Mt). The results provided essential basic data for radiological impact assessment of steel production, as well as that of nuclear energy chain, coal chain and other electricity sources.

Asunto(s)

RESUMEN

Lifetime risks of radon induced lung cancer were assessed based on epidemiological approaches for Canadian, Swiss and Chinese populations, using the most recent vital statistic data and radon distribution characteristics available for each country. In the risk calculation, the North America residential radon risk model was used for the Canadian population, the European residential radon risk model for the Swiss population, the Chinese residential radon risk model for the Chinese population, and the EPA/BEIR-VI radon risk model for all three populations. The results were compared with the risk calculated from the International Commission on Radiological Protection (ICRP)'s exposure-to-risk conversion coefficients. In view of the fact that the ICRP coefficients were recommended for radiation protection of all populations, it was concluded that, generally speaking, lifetime absolute risks calculated with ICRP-recommended coefficients agree reasonably well with the range of radon induced lung cancer risk predicted by risk models derived from epidemiological pooling analyses.

Asunto(s)

RESUMEN

BACKGROUND AND AIMS: Abdominal cocoon (AC) is a rare abdominal disease with nonspecific clinical features, and it is difficult to be diagnosed before operation and hard to be treated in clinical practice. The aim of this study is to investigate the diagnosis and treatment of AC. METHODS: The clinical manifestations, findings during surgery, treatments, and follow-up results of 26 cases of AC were retrospectively studied from January 2001 to January 2015. RESULTS: All of 26 cases were diagnosed as AC definitely by laparotomy or laparoscopic surgery. Their clinical findings were various, with 7 intestines obstructed with bezoars and 4 intestines perforated by spiny material. Based on the existence of the second enterocoelia, all cases were categorized into 2 types: type I is absent of second enterocoelia (18 cases, 69.23%), while type II shows second enterocoelia (8 cases, 30.77%). Twenty cases (12 were type I and 8 were type II) underwent membrane excision and careful enterodialysis to release the small intestine entirely or partially, while the other 6 cases (all were type I) did not. In addition, all patients were treated with medical treatment and healthy diet and lifestyle. Finally, most of the patients recovered smoothly. CONCLUSIONS: AC can be categorized into two types; surgery is recommended for type II and part of type I with severe complications, but sometimes conservative therapy might be appropriate for type I. Laparoscopic surgery plays an important role in the diagnosis and treatment of AC. Furthermore, favorite health education, healthy diet and lifestyle are of significance in patients' recovery.

Asunto(s)

RESUMEN

Due to the improvement of production technology and the adjustment of energy structure, as well as the town-ownership and private-ownership coal mines (TPCM) were closed or merged by national policy, the number of underground miner has changed comparing with 2004 in China, so collective dose and normalization collective dose in different type of coal mine should be changed at the same time. In this paper, according to radiation exposure by different ventilation condition and the annual output, the coal mines in China are divided into three types, which are named as national key coal mines (NKCM), station-owned local coal mines (SLCM) and TPCM. The number of underground coal miner, collective dose and normalization collective dose are estimated at present base on surveying annual output and production efficiency of raw coal in 2005-2014. The typical total value of the underground coal miners recommended in China is 5.1 million in 2005-2009, and in which there are respectively included 1 million, 0.9 million and 3.2 million for NKCM, SLCM and TPCM. There are total of 4.7 million underground coal miner in 2010-2014, and the respectively number for NKCM, SLCM and TPCM are 1.4 million, 1.2 million and 2.1 million. The collective dose in 2005-2009 is 11 335 man·Sv·y-1, and in which there are respectively included 280, 495 and 10 560 man·Sv·y-1 for NKCM, SLCM and TPCM. As far as 2010-2014, there are total of 7982 man·Sv·y-1, and 392, 660 and 6930 man·Sv·y-1 for each type of coal mines. Therefore, the main contributor of collective dose is from TPCM. The normalization collective dose in 2005-2009 is 0.0025, 0.015 and 0.117 man·Sv per 10 kt for NKCM, SLCM and TPCM, respectively. As far as 2010-2014, there are 0.0018, 0.010 and 0.107 man·Sv per 10 kt for each type of coal mines. The trend of normalization collective dose is decreased year by year.

Asunto(s)

RESUMEN

Haiyang Nuclear Power Plant to be built in China was selected as a case for the dose pre-assessment for marine biota in this study. The concentrations of Cs and Co in organisms (turbot, yellow croaker, swimming crab, abalone, sea cucumber, and sea lettuce), seawater, and bottom sediment sampled on-site were measured by neutron activation analysis, and the site-specific transfer parameters (concentration ratios and distribution coefficients) of Cs and Co were calculated. (134)Cs, (137)Cs, and (60)Co activity concentrations in the organisms and the sediment at the site were calculated with the site-specific transfer parameters and the anticipated activity concentrations in the liquid effluent of the nuclear power plant. The ERICA tool was used to estimate the dose rates of (134)Cs, (137)Cs, and (60)Co to the selected organisms based on the biological models developed. The total dose rates of (134)Cs, (137)Cs, and (60)Co to the six organisms were all <0.001 µGy h(-1).

Asunto(s)

RESUMEN

An effective approach to greatly enhancing the selective secretion and expression of recombinant cytoplasmic enzymes in Escherichia coli was successfully developed through the synergistic effect of ethylenediaminetetraacetate (EDTA) and lysozyme. The method was applied to two endoglucanases (EGs) and an amylase. The optimal culture conditions of temperature and concentration of isopropyl-ß-D: -1-thiogalactopyranoside (IPTG) were 23-30 °C and 0.2 mM, respectively, under which the three enzymes could be expressed in active form. Among all the chemicals tested, EDTA was found to be most suitable for enhancing the secretion of EG-I-1A into the medium. Addition of lysozyme alone had little influence on the secretion and expression. In contrast, on the basis of the addition of 5 g EDTA/L at the induction time of 12 h, the simultaneous addition of 0.15 g lysozyme/L further significantly increased the secretion and expression of the three enzymes, demonstrating the synergistic effect of EDTA and lysozyme. The production of EG-I-1A in the culture medium by adding 5 g EDTA/L and 0.15 g lysozyme/L under the optimal culture conditions of 23 °C and 0.2 mM IPTG was over 260-fold higher than that without EDTA and lysozyme under the standard conditions of 37 °C and 1 mM IPTG. In summary, the advantage of this novel cultivation approach for secretion was that not only did it selectively enhance the secretion of the proteins of interest, but also greatly increased the expression of the three enzymes by over 80 %.

Asunto(s)

RESUMEN

An endoglucanase from Bacillus akibai I-1 was successfully overexpressed in Bacillus subtilis 168 and the expression level of the recombinant enzyme was greatly enhanced by using the sucrose-inducible sacB promoter. The endoglucanase activity in the culture supernatant of recombinant B. subtilis by using itself promoter (HpaII) in plasmid pMA5 was 3U/ml. Interestingly, with the addition of sacB promoter at downstream from the HpaII promoter or the replacement of HpaII promoter by the sacB promoter, the endoglucanase activities reached 62 and 60U/ml, respectively, under the optimal culture conditions. These results demonstrated that the sacB promoter might be more efficient for the expression of the endoglucanase than the HpaII promoter. More interestingly, the purified native enzyme had broad pH stability, good thermostability and resistibility to various metal ions and chelating agents examined, while the recombinant enzyme had improved resistibility to SDS, which was stable in 0.2% (w/v) laundry detergent and thus showed great potential in detergents industry.

Asunto(s)

RESUMEN

An alkaline endoglucanase from Bacillus akibai III-3A was successfully expressed in Escherichia coli in active form, and secretion was greatly enhanced by addition of 5 g/l ethylenediamine tetraacetic acid (EDTA) to the culture medium at the induction time of 12 h. Under the optimal culture conditions, extracellular and total endoglucanase activities were 18.5 and 31.2 U/ml, respectively. Both the recombinant and native enzymes exhibited similar properties with respect to broad pH stability, good thermostability, and resistibility to various metal ions and reagents examined. However, unlike the native endoglucanase that was partly inhibited by sodium dodecyl sulfate (SDS), the recombinant enzyme had good resistibility to SDS, being very stable in the commercial detergents, and no decrease in residual activity was observed in 0.2% (w/v) laundry detergent, indicating that it was suitable for application in detergents industry.

Asunto(s)