BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satel...BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.展开更多
The development of efficient and cost-effective catalysts to catalyze a wide variety of electrochemical reactions is key to realize the large-scale applicati on of ren ewable and clean en ergy tech no logies.Owing to ...The development of efficient and cost-effective catalysts to catalyze a wide variety of electrochemical reactions is key to realize the large-scale applicati on of ren ewable and clean en ergy tech no logies.Owing to the maximum atom-utilization efficie ncy and unique electronic and geometric structures,single atom catalysts(SACs)have exhibited superior performance in various catalytic systems.Recently,assembled from the function alized orga nic lin kers and metal no des,metal-organic frameworks(MOFs)with ultrafi ne porosity have received treme ndous attention as precursors or self-sacrificing templates for preparing porous SACs.Here,the recent advances toward the synthesis strategies for using MOF precursors/templates to con struct SACs are systematically summarized with special emphasis on the types of central metal sites.The electrochemical applications of these recently emerged MOF-derived SACs for various energy-conversion processes,such as oxygen reduction/evolution reaction(ORR/OER),hydrogen evolution reaction(HER),and CO2 reduction reaction(CO2RR),are also discussed and reviewed.Fin ally,the curre nt challe nges and prospects regardi ng the developme nt of MOF-derived SACs are proposed.展开更多
The climatic and environmental effects of atmospheric aerosols are a hot topic in global science community, and radiative properties of the aerosols are one of the important parameters in assessing climatic change. He...The climatic and environmental effects of atmospheric aerosols are a hot topic in global science community, and radiative properties of the aerosols are one of the important parameters in assessing climatic change. Here we studied the black carbon concentration and absorption coefficient measured with aethalometers, scattering coefficient measured with nephelometers, and single scattering albedo derived at an atmospheric composition watch station in Guangzhou from 2004 to 2007. Our main results are as follows. The data of black carbon concentration and absorption coefficients measured with instruments cannot be directly used until they are measured in parallel with internationally accepted instruments for comparison, calibration, and reduction. After evaluation of the data, the result shows that the monthly mean of BC concentration varies 3.1―14.8 μg·m-3 and the concentration decreases by about 1 μg·m-3 in average over the four years; It is higher in the dry season with a multi-year mean of 8.9 μg/m3 and lower in the rainy season with a multi-year mean of 8.0 μg·m-3; The extreme maximum of monthly mean concentration occurred in December 2004 and extreme minimum in July 2007, and a 4-year mean is 8.4 μg·m-3. It is also shown that monthly mean scattering coefficient derived varies 129 -565 Mm-1, monthly mean absorption coefficient 32-139 Mm-1, and monthly mean single scattering albedo 0.71-0.91, with annual mean values of 0.80, 0.82, 0.79 and 0.84 for 2004, 2005, 2006 and 2007, respectively. Three instruments were used to take simultaneous measurements of BC in PM10, PM2.5, and PM1 and the results showed that PM2.5 took up about 90% of PM10 and PM1 accounted for about 68% of PM2.5, and BC aerosols are mainly present in fine particulates. The variability of BC concentrations is quite consistent between the Nancun station (141 m above sea level) and the Panyu station (13 m above sea level), which are 8 km apart from each other. The concentration in higher altitude station (Panyu) is consistently lower than展开更多
There is a rapidly rising trend in the development and application of molecular marker assays for gene map- ping and discovery in field crops and trees. Thus far, more than 50 SNP arrays and 15 different types of geno...There is a rapidly rising trend in the development and application of molecular marker assays for gene map- ping and discovery in field crops and trees. Thus far, more than 50 SNP arrays and 15 different types of genotyping-by-sequencing （GBS） platforms have been developed in over 25 crop species and perennial trees. However, much less effort has been made on developing ultra-high-throughput and cost-effective genotyping platforms for applied breeding programs. In this review, we discuss the scientific bottlenecks in existing SNP arrays and GBS technologies and the strategies to develop targeted platforms for crop mo- lecular breeding. We propose that future practical breeding platforms should adopt automated genotyping technologies, either array or sequencing based, target functional polymorphisms underpinning economic traits, and provide desirable prediction accuracy for quantitative traits, with universal applications under wide genetic backgrounds in crops. The development of such platforms faces serious challenges at both the technological level due to cost ineffectiveness, and the knowledge level due to large genotype- phenotype gaps in crop plants. It is expected that such genotyping platforms will be achieved in the next ten years in major crops in consideration of （a） rapid development in gene discovery of important traits, （b） deepened understanding of quantitative traits through new analytical models and population designs, （c） integration of multi-layer -omics data leading to identification of genes and pathways responsible for important breeding traits, and （d） improvement in cost effectiveness of large-scale genotyping. Crop breeding chips and genotyping platforms will provide unprecedented opportunities to accelerate the development of cultivars with desired yield potential, quality, and enhanced adaptation to mitigate the effects of climate change.展开更多
A high-density single nucleotide polymorphism （SNP） array is critically important for geneticists and molecu- lar breeders. With the accumulation of huge amounts of genomic re-sequencing data and available technolog...A high-density single nucleotide polymorphism （SNP） array is critically important for geneticists and molecu- lar breeders. With the accumulation of huge amounts of genomic re-sequencing data and available technologies for accurate SNP detection, it is possible to design high-density and high-quality rice SNP arrays. Here we report the devel- opment of a high-density rice SNP array and its utility. SNP probes were designed by screening more than 10 000 000 SNP loci extracted from the re-sequencing data of 801 rice varieties and an array named RiceSNP50 was produced on the Illumina Infinium platform. The array contained 51 478 evenly distributed markers, 68% of which were within genic regions. Several hundred rice plants with parent/F1 relationships were used to generate a high-quality cluster file for accurate SNP calling. Application tests showed that this array had high genotyping accuracy, and could be used for dif- ferent objectives. For example, a core collection of elite rice varieties was clustered with fine resolution. Genome-wide association studies （GWAS） analysis correctly identified a characterized QTL. Further, this array was successfully used for variety verification and trait introgression. As an accurate high-throughput genotyping tool, RiceSNP50 will play an important role in both functional genomics studies and molecular breeding.展开更多
Hepatocellular carcinoma(HCC) is the fourth cause of cancer related mortality, and its incidence is rapidly increasing. Viral hepatitis, alcohol abuse, and exposure to hepatotoxins are major risk factors, but nonalcoh...Hepatocellular carcinoma(HCC) is the fourth cause of cancer related mortality, and its incidence is rapidly increasing. Viral hepatitis, alcohol abuse, and exposure to hepatotoxins are major risk factors, but nonalcoholic fatty liver disease(NAFLD) associated with obesity, insulin resistance, and type 2 diabetes, is an increasingly recognized trigger, especially in developed countries. Older age, severity of insulin resistance and diabetes, and iron overload have been reported to predispose to HCC in this context. Remarkably, HCCs have been reported in non-cirrhotic livers in a higher proportion of cases in NAFLD patients than in other etiologies. Inherited factors have also been implicated to explain the different individual susceptibility to develop HCC, and their role seems magnified in fatty liver, where only a minority of affected subjects progresses to cancer. In particular, the common I148 M variant of the PNPLA3 gene influencing hepatic lipid metabolism influences HCC risk independently of its effect on the progression of liver fibrosis. Recently, rare loss-of-function mutations in Apolipoprotein B resulting in very low density lipoproteins hepatic retention and in Telomerase reverse transcriptase influencing cellular senescence have also been linked to HCC in NAFLD. Indeed, hepatic stellate cells senescence has been suggested to bridge tissue aging with alterations of the intestinal microbiota in the pathogenesis of obesity-related HCC. A deeper understanding of the mechanisms mediating hepatic carcinogenesis during insulin resistance, and the identification of its genetic determinants will hopefully provide new diagnostic and therapeutic tools.展开更多
Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study,...Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study, fourteen surface sediment samples were taken in the middle reach of the Yellow River. Contents of Zn, Pb, Ni, Cu, Cr, Cd, As were measured, and the pollution status was assessed using three widely used pollution assessment methods, including the single factor index method, Nemerow pollution index method and potential ecological risk index. The concentrations of the studied heavy metals followed the order： Zn 〉 Cr 〉 Cu 〉 Ni 〉 Pb 〉 As 〉 Cd. Nearly 50% of sites had Cu and Cr accumulation. The concentration of Cu at the Yiluo River exceeded the secondary standard value of the Environmental quality standard for soils. Comparison of heavy metal concentrations between this study and other selected rivers indicated that Cu and Cr may be the major pollutants in our case. The single factor index indicated that many samples were at high levels of pollution for Cu and Cd; the Nemerow pollution index indicated that the Yihe River, Luohe River, Yiluo River and Huayuankou were polluted. According to the results of potential ecological risk assessment, Cd in the tributaries of Luo River, Yihe River,and Yiluo River showed high risk toward the ecosystem and human health, Cd in Huanyuankou and Cu in Yiluo River showed a middle level of risk and other samples were at a low level of risk.展开更多
The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we s...The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we successfully synthesized cobalt single atom site catalysts(Co SACs)with high metal loading of 23.58 wt.%supported on carbon nitride(CN),which showed excellent catalytic properties for oxidation of ethylbenzene in air.Moreover,Co SACs show a much higher turn-over frequency(19.6 h^(−1))than other reported non-noble catalysts under the same condition.Comparatively,the as-obtained nanosized or homogenous Co catalysts are inert to this reaction.Co SACs also exhibit high selectivity(97%)and stability(unchanged after five runs)in this reaction.DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water,which result in the robust catalytic performance for this reaction.展开更多
The introduction of laparoscopy is an example of surgical innovation with a rapid implementation in many areas of surgery. A large number of controlled studiesand meta-analyses have shown that laparoscopic colorectal ...The introduction of laparoscopy is an example of surgical innovation with a rapid implementation in many areas of surgery. A large number of controlled studiesand meta-analyses have shown that laparoscopic colorectal surgery is associated with the same benefits than other minimally invasive procedures, including lesser pain, earlier recovery of bowel transit and shorter hospital stay. On the other hand, despite initial concerns about oncological safety, well-designed prospective randomized multicentre trials have demonstrated that oncological outcomes of laparoscopy and open surgery are similar. Although the use of laparoscopy in colorectal surgery has increased in recent years, the percentages of patients treated with surgery using minimally invasive techniques are still reduced and there are also substantial differences among centres. It has been argued that the limiting factor for the use of laparoscopic procedures is the number of surgeons with adequate skills to perform a laparoscopic colectomy rather than the tumour of patients' characteristics. In this regard, future efforts to increase the use of laparoscopic techniques in colorectal surgery will necessarily require more efforts in teaching surgeons. We here present a review of recent controversies of the use of laparoscopy in colorectal surgery, such as in rectal cancer operations, the possibility of reproducing complete mesocolon excision, and the benefits of intracorporeal anastomosis after right hemicolectomy. We also describe the results of latest innovations such as single incision laparoscopic surgery, robotic surgery and natural orifice transluminal endoscopic surgery for colon and rectal diseases.展开更多
This paper was to explore the mechanism of single basal application of controlled-release fertilizers for increasing yield of rice （Oryza sativa L.）. Pot trials and cylinder trials were carried out from 2002 to 2005...This paper was to explore the mechanism of single basal application of controlled-release fertilizers for increasing yield of rice （Oryza sativa L.）. Pot trials and cylinder trials were carried out from 2002 to 2005 to study the influences of single basal application of 3 controlled-release fertilizers on the changes of soil available N, root development, senescence and lodging resistance at late growth stages. Results showed that at 30 days after fertilization, single basal application of controlled-release fertilizers coated with vegetal-substance （CRF1） and polymer materials （CRF3） increased soil available N to 12.0 and 147.9%, respectively, in comparison to split fertilization of rice-specific fertilizer （RSF1）. Treatments of the two CRFs obviously benefited the development of root system, resulting in greater rice root weights with extensive distribution and higher root activity. In addition, the two CRF treatments, in comparison to RSF1, enhanced chlorophyll consents of the flag leaves to 9.5 and 15.5%, and soluble protein up to 89.7 and 108.0% respectively. Application of the two CRFs also made the base of rice stems strong and large, declined the proportion of shoot and root, increased root depth index. Though relatively low K rate, single basal application of the CRF3 coated with NH4MgPO4 could also promote the development of root system, enhance root activity and some physiological functions of flag leaves. Based on these results, it was concluded that major mechanisms for increasing rice yield by single basal application of the CRFs should be attributed to grater soil available N supply, superior development of root systems, better nutrient absorption capacity, slower senescence and enhancement of lodging resistance at late stages.展开更多
The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior.The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has...The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior.The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has been greatly concerned in the fields of geotechnical,mining,geological,and petroleum engineering.In order to probe the mechanism of fluid flow and the effects of rough structures,we conducted a few laboratory tests of fluid flow through single rough fractures,in which the Weierstrass-Mandelbrot fractal function and PMMA material were employed to produce the fracture models with various fractal roughnesses.A high-speed video camera was employed to record the fluid flow through the entire single rough fracture with a constant hydraulic pressure.The properties of fluid flow varying with the fracture roughness and the influences of the rough structure were analyzed.The components of flow resistance of a single rough fracture were discussed.A fractal model was proposed to relate the fluid resistance to the fracture roughness.A fractal equivalent permeability coefficient of a single rough fracture was formulated.This study aims to provide an experimental basis and reference for better understanding and quantitatively relating the fluid flow properties to the structures of rock fractures.展开更多
AIM： To study the alterations in p53 gene among Indian gastric cancer patients and to correlate them with the various clinicopathological parameters. METHODS： A total of 103 gastric cancer patients were included in ...AIM： To study the alterations in p53 gene among Indian gastric cancer patients and to correlate them with the various clinicopathological parameters. METHODS： A total of 103 gastric cancer patients were included in this study. The p53 alterations were studied by both immunohistochemical method as well as polymerase chain reaction （PCR）-single strand conformation polymorphism （SSCP） analysis. We only studied four （exon 5, 6, 7, and 8） of the 11 ,p53 exons. The alterations in p53 were also correlated with respect to various clinicopathological parameters. RESULTS： Among 103 cases, p53 over-expression and alteration were detected in 37 （35.92%） and 19 （18.44%） cases, respectively. Most of the ,p53 alterations were found at exon 5 （31.54%）, followed by exon 6 （26.31%）, exon 7 （21.04%） and exon 8 （21.04%）. A significant correlation of p53 overexpression was found with p53 alteration （P = 0.000）. Concordance between ,p53 alteration （as detected by SSCP） and over-expression [as detected by immunohistochemistry （IHC）] was found in 75% cases. We found that IHC-positive/SSCP-negative cases accounted for 21% of cases and IHC-negative/SSCP- positive cases accounted for remaining 4% cases. CONCLUSION： Our results show that p53 gene mutations are significantly correlated with p53 protein over-expression, with 75% concordance in over-expression and alteration in the p53 gene, but 25% disconcordance also cautions against the assumption that p53 over-expression is always associated with a gene mutation. There may be other mechanisms responsible for stabilization and accumulation of p53 protein with no evidence of gene mutation that reflect an accumulation of a non-mutated protein, or a false negative SSCP result.展开更多
In the eastern Nanling Range there exists the early Yanshanian syenite-granite assemblage. A representative example is the Pitou-Tabei complex composed of the Tabei syenite pluton and the Pitou syenogranite pluton in ...In the eastern Nanling Range there exists the early Yanshanian syenite-granite assemblage. A representative example is the Pitou-Tabei complex composed of the Tabei syenite pluton and the Pitou syenogranite pluton in southern Jiangxi Province. U-Pb zircon dating yields ages of 188.6±2.2 Ma for the Tabei pluton and 186.3±1.1 Ma for the Pitou pluton. The Tabei syenite is characterized by relatively low SiO2 content (62.40% - 68.75%), high alkalis (K2O+Na2O = 10.56%-11.96%), low percent K2O/Na2O ratios (0.56-0.93), metaluminous fea- ture (A/CNK = 0.80-1.00), enrichment in LILE (Rb, Ba, K) and HFSE (Th, U, Nb, Ta, Zr, and so on), weakly negative to positive Eu anomalies (δ Eu = 0.63-1.82), relatively low (87Sr/86Sr)i (0.70412-0.70543), and relatively high ε Nd(t) (3.14-3.52). The Pitou syenogranite is charac- terized by high silicon content (SiO2 = 71.06%-76.28%), relatively low alkalis (K2O+Na2O = 8.10%-9.80%), high percent K2O/Na2O ratios (1.22-1.94), metaluminous feature (A/CNK = 0.94-1.07), enrichment in Rb, Th (U), K, depletion in Ba, Nb, Ta, Sr, P , Zr, Ti, high ΣREE (av- eraging 451.03 μg/g), strong negative Eu anomalies (δ Eu = 0.27-0.33), relatively high (87Sr/86Sr)i (0.70805-0.70912), and relatively low ε Nd( t ) (?5.35-?6.29). The Tabei syenite and Pitou syenogranite both have the characteristics of A-type granites. The former is considered to be from the asthenosphere mantle, and the latter was the product of the crust-mantle mixture. They both were probably formed in a rifting setting.展开更多
Background Genetic factors are believed to play a role in the individual susceptibility to chronic obstructive pulmonary disease (COPD). A single nucleotide polymorphism (SNP) of tumour necrosis factor-α (TNF-α) has...Background Genetic factors are believed to play a role in the individual susceptibility to chronic obstructive pulmonary disease (COPD). A single nucleotide polymorphism (SNP) of tumour necrosis factor-α (TNF-α) has been reported but inconsistent results may arise from different populations and phenotypes of COPD. There are only a few published studies of interleukin-13 (IL-13) SNPs on COPD. The SNPs of TNF-α and IL-13 have not been studied in the Chinese population. This research was conducted to study the frequencies of IL-13 gene promoter 1055 (IL-13-1055) and TNF-α gene-308 polymorphisms in the patients with COPD and to investigate the effect of those genetic polymorphisms on COPD in the Chinese population.Methods A cohort of COPD patients and age matched controls were recruited from an inpatient hospital service in Beijing. Venous blood was obtained and genomic DNA was extracted from peripheral blood monocytes using standard method. Genomic DNA was used as a template for amplification by polymerase chain reaction (PCR) to determine the polymorphism at -1055 in the IL-13 gene promoter region. PCR restriction fragment length polymorphism (RFLP) was used to determine polymorphisms in the TNF-α gene-308 position. The products were investigated by sequence analysis also. Results One hundred and eleven COPD patients and 97 controls were studied. Seventy-five cases were current smokers in COPD patients and 36 were current smokers in controls. The frequencies of TT genotype in the IL-13 gene promoter region were 11.7% (13/111) in the COPD group and 13.4% (13/97) in the controls (P=0.713). However, the OR value of TT genotype was significantly increased to 6.4 (95% CI 1.62-25.39) in the smokers with COPD. TT genotype was also positively related to family history of COPD, OR=7.7 (95% CI 1.37-43.80). The frequencies of A allele in the TNF-α gene were 5.9% in COPD and 3.1% in controls (P=0.131). The OR value of A allele was 5.0 (95% CI 1.011 to 25.059) in smokers with COPD. Conclusions There is no significant diff展开更多
Background Ossification of the posterior longitudinal ligament （OPLL） has a strong genetic background. Previous studies have shown that bone morphogenetic protein-2 （BMP2） and BMP2 mRNA are expressed in ossifying ...Background Ossification of the posterior longitudinal ligament （OPLL） has a strong genetic background. Previous studies have shown that bone morphogenetic protein-2 （BMP2） and BMP2 mRNA are expressed in ossifying matrix and chondrocytes adjacent to cartilaginous areas of OPLL tissues and mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas. It is suggested that BMP2 plays different roles in the different stages of development of OPLL. However, it remains unknown which factors induce ligament cells to produce BMP2. Methods OPLL patients （n=-192） and non-OPLL controls （n=304） were studied. Radiographs of the cervical spine were analyzed for extent of OPLL. We investigated whether single nucleotide polymorphisms of exons 3（-726） T/C and 3（-583） NG in the BMP2 gene are statistically associated with genetic susceptibility to OPLL in Chinese Han subjects. Results There was no statistical difference between the occurrence of exons 3（-726） T/C and 3（-583） NG and the occurrence of OPLL in the cervical spine. However, there was a significant association between occurrence of exon 3（-726） T/C polymorphism and occurrence of OPLL in males of cases and controls in the cervical spine. In addition, no significant association was found between the exons 3（-726） T/C and 3（-583） A/G with number of ossified cervical vertebrae in OPLL patients. Conclusions Exon 3（-583） A/G polymorphism in BMP2 gene is not associated with the occurrence and the extent of OPLL in the cervical spine. Chinese Han male patients with TC and CC genotypes in exon 3（-726） T/C have genetic susceptibility to OPLL but not to more extensive OPLL in the cervical spine.展开更多
基金sponsored by the National Natural Science Foundation of China(Grant Nos.41020144004,41374019,41104022)the National High Technology Research and Development Program of China(Grant No.2013AA122501)
文摘BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.
基金This work was supported by the National Key R&D Program of China(No.2016YFA0202801)the National Natural Science Foundation of China(Nos.21671117,21871159,21890383,and 21676018)and the China Postdoctoral Science Foundation(No.2017M610864).
文摘The development of efficient and cost-effective catalysts to catalyze a wide variety of electrochemical reactions is key to realize the large-scale applicati on of ren ewable and clean en ergy tech no logies.Owing to the maximum atom-utilization efficie ncy and unique electronic and geometric structures,single atom catalysts(SACs)have exhibited superior performance in various catalytic systems.Recently,assembled from the function alized orga nic lin kers and metal no des,metal-organic frameworks(MOFs)with ultrafi ne porosity have received treme ndous attention as precursors or self-sacrificing templates for preparing porous SACs.Here,the recent advances toward the synthesis strategies for using MOF precursors/templates to con struct SACs are systematically summarized with special emphasis on the types of central metal sites.The electrochemical applications of these recently emerged MOF-derived SACs for various energy-conversion processes,such as oxygen reduction/evolution reaction(ORR/OER),hydrogen evolution reaction(HER),and CO2 reduction reaction(CO2RR),are also discussed and reviewed.Fin ally,the curre nt challe nges and prospects regardi ng the developme nt of MOF-derived SACs are proposed.
基金Supported by Natural Science Foundation of China (Grant Nos. U0733004,40375002, 40418008, 40775011)National High Technology R & D Program of China (Grant Nos. 2006AA06A306 and 2006AA06A308)National Basic Research Program of China (Grant No. 2005CB422207)
文摘The climatic and environmental effects of atmospheric aerosols are a hot topic in global science community, and radiative properties of the aerosols are one of the important parameters in assessing climatic change. Here we studied the black carbon concentration and absorption coefficient measured with aethalometers, scattering coefficient measured with nephelometers, and single scattering albedo derived at an atmospheric composition watch station in Guangzhou from 2004 to 2007. Our main results are as follows. The data of black carbon concentration and absorption coefficients measured with instruments cannot be directly used until they are measured in parallel with internationally accepted instruments for comparison, calibration, and reduction. After evaluation of the data, the result shows that the monthly mean of BC concentration varies 3.1―14.8 μg·m-3 and the concentration decreases by about 1 μg·m-3 in average over the four years; It is higher in the dry season with a multi-year mean of 8.9 μg/m3 and lower in the rainy season with a multi-year mean of 8.0 μg·m-3; The extreme maximum of monthly mean concentration occurred in December 2004 and extreme minimum in July 2007, and a 4-year mean is 8.4 μg·m-3. It is also shown that monthly mean scattering coefficient derived varies 129 -565 Mm-1, monthly mean absorption coefficient 32-139 Mm-1, and monthly mean single scattering albedo 0.71-0.91, with annual mean values of 0.80, 0.82, 0.79 and 0.84 for 2004, 2005, 2006 and 2007, respectively. Three instruments were used to take simultaneous measurements of BC in PM10, PM2.5, and PM1 and the results showed that PM2.5 took up about 90% of PM10 and PM1 accounted for about 68% of PM2.5, and BC aerosols are mainly present in fine particulates. The variability of BC concentrations is quite consistent between the Nancun station (141 m above sea level) and the Panyu station (13 m above sea level), which are 8 km apart from each other. The concentration in higher altitude station (Panyu) is consistently lower than
基金This study was supported by the National Key Research and Development Program of China （2016YFD0101802 and 2016YFE0108600） and National Natural Science Foundation of China （31550110212）.
文摘There is a rapidly rising trend in the development and application of molecular marker assays for gene map- ping and discovery in field crops and trees. Thus far, more than 50 SNP arrays and 15 different types of genotyping-by-sequencing （GBS） platforms have been developed in over 25 crop species and perennial trees. However, much less effort has been made on developing ultra-high-throughput and cost-effective genotyping platforms for applied breeding programs. In this review, we discuss the scientific bottlenecks in existing SNP arrays and GBS technologies and the strategies to develop targeted platforms for crop mo- lecular breeding. We propose that future practical breeding platforms should adopt automated genotyping technologies, either array or sequencing based, target functional polymorphisms underpinning economic traits, and provide desirable prediction accuracy for quantitative traits, with universal applications under wide genetic backgrounds in crops. The development of such platforms faces serious challenges at both the technological level due to cost ineffectiveness, and the knowledge level due to large genotype- phenotype gaps in crop plants. It is expected that such genotyping platforms will be achieved in the next ten years in major crops in consideration of （a） rapid development in gene discovery of important traits, （b） deepened understanding of quantitative traits through new analytical models and population designs, （c） integration of multi-layer -omics data leading to identification of genes and pathways responsible for important breeding traits, and （d） improvement in cost effectiveness of large-scale genotyping. Crop breeding chips and genotyping platforms will provide unprecedented opportunities to accelerate the development of cultivars with desired yield potential, quality, and enhanced adaptation to mitigate the effects of climate change.
基金grants from the National High Technology Research and Development Program of China，the National Program on Key Basic Research Project of China，the National Natural Science Foundation of China，Guangdong Innovative Research Team Program，the Ministry of Agriculture of China
文摘A high-density single nucleotide polymorphism （SNP） array is critically important for geneticists and molecu- lar breeders. With the accumulation of huge amounts of genomic re-sequencing data and available technologies for accurate SNP detection, it is possible to design high-density and high-quality rice SNP arrays. Here we report the devel- opment of a high-density rice SNP array and its utility. SNP probes were designed by screening more than 10 000 000 SNP loci extracted from the re-sequencing data of 801 rice varieties and an array named RiceSNP50 was produced on the Illumina Infinium platform. The array contained 51 478 evenly distributed markers, 68% of which were within genic regions. Several hundred rice plants with parent/F1 relationships were used to generate a high-quality cluster file for accurate SNP calling. Application tests showed that this array had high genotyping accuracy, and could be used for dif- ferent objectives. For example, a core collection of elite rice varieties was clustered with fine resolution. Genome-wide association studies （GWAS） analysis correctly identified a characterized QTL. Further, this array was successfully used for variety verification and trait introgression. As an accurate high-throughput genotyping tool, RiceSNP50 will play an important role in both functional genomics studies and molecular breeding.
文摘Hepatocellular carcinoma(HCC) is the fourth cause of cancer related mortality, and its incidence is rapidly increasing. Viral hepatitis, alcohol abuse, and exposure to hepatotoxins are major risk factors, but nonalcoholic fatty liver disease(NAFLD) associated with obesity, insulin resistance, and type 2 diabetes, is an increasingly recognized trigger, especially in developed countries. Older age, severity of insulin resistance and diabetes, and iron overload have been reported to predispose to HCC in this context. Remarkably, HCCs have been reported in non-cirrhotic livers in a higher proportion of cases in NAFLD patients than in other etiologies. Inherited factors have also been implicated to explain the different individual susceptibility to develop HCC, and their role seems magnified in fatty liver, where only a minority of affected subjects progresses to cancer. In particular, the common I148 M variant of the PNPLA3 gene influencing hepatic lipid metabolism influences HCC risk independently of its effect on the progression of liver fibrosis. Recently, rare loss-of-function mutations in Apolipoprotein B resulting in very low density lipoproteins hepatic retention and in Telomerase reverse transcriptase influencing cellular senescence have also been linked to HCC in NAFLD. Indeed, hepatic stellate cells senescence has been suggested to bridge tissue aging with alterations of the intestinal microbiota in the pathogenesis of obesity-related HCC. A deeper understanding of the mechanisms mediating hepatic carcinogenesis during insulin resistance, and the identification of its genetic determinants will hopefully provide new diagnostic and therapeutic tools.
基金supported by the National Basic Research Program (973) of China (No. 2015CB453103)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB14020102)the National Natural Science Foundation of China (Nos. 21477150 and 21321004)
文摘Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study, fourteen surface sediment samples were taken in the middle reach of the Yellow River. Contents of Zn, Pb, Ni, Cu, Cr, Cd, As were measured, and the pollution status was assessed using three widely used pollution assessment methods, including the single factor index method, Nemerow pollution index method and potential ecological risk index. The concentrations of the studied heavy metals followed the order： Zn 〉 Cr 〉 Cu 〉 Ni 〉 Pb 〉 As 〉 Cd. Nearly 50% of sites had Cu and Cr accumulation. The concentration of Cu at the Yiluo River exceeded the secondary standard value of the Environmental quality standard for soils. Comparison of heavy metal concentrations between this study and other selected rivers indicated that Cu and Cr may be the major pollutants in our case. The single factor index indicated that many samples were at high levels of pollution for Cu and Cd; the Nemerow pollution index indicated that the Yihe River, Luohe River, Yiluo River and Huayuankou were polluted. According to the results of potential ecological risk assessment, Cd in the tributaries of Luo River, Yihe River,and Yiluo River showed high risk toward the ecosystem and human health, Cd in Huanyuankou and Cu in Yiluo River showed a middle level of risk and other samples were at a low level of risk.
基金This work was supported by the National Key R&D Program of China(Nos.2018YFA0702003 and 2016YFA0202801)the National Natural Science Foundation of China(Nos.21890383,21671117,21871159,and 21901135)+2 种基金Science and Technology Key Project of Guangdong Province of China(No.2020B010188002)Beijing Municipal Science&Technology Commission(No.Z191100007219003)China Postdoctoral Science Foundation(No.2018M640114).
文摘The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we successfully synthesized cobalt single atom site catalysts(Co SACs)with high metal loading of 23.58 wt.%supported on carbon nitride(CN),which showed excellent catalytic properties for oxidation of ethylbenzene in air.Moreover,Co SACs show a much higher turn-over frequency(19.6 h^(−1))than other reported non-noble catalysts under the same condition.Comparatively,the as-obtained nanosized or homogenous Co catalysts are inert to this reaction.Co SACs also exhibit high selectivity(97%)and stability(unchanged after five runs)in this reaction.DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water,which result in the robust catalytic performance for this reaction.
文摘The introduction of laparoscopy is an example of surgical innovation with a rapid implementation in many areas of surgery. A large number of controlled studiesand meta-analyses have shown that laparoscopic colorectal surgery is associated with the same benefits than other minimally invasive procedures, including lesser pain, earlier recovery of bowel transit and shorter hospital stay. On the other hand, despite initial concerns about oncological safety, well-designed prospective randomized multicentre trials have demonstrated that oncological outcomes of laparoscopy and open surgery are similar. Although the use of laparoscopy in colorectal surgery has increased in recent years, the percentages of patients treated with surgery using minimally invasive techniques are still reduced and there are also substantial differences among centres. It has been argued that the limiting factor for the use of laparoscopic procedures is the number of surgeons with adequate skills to perform a laparoscopic colectomy rather than the tumour of patients' characteristics. In this regard, future efforts to increase the use of laparoscopic techniques in colorectal surgery will necessarily require more efforts in teaching surgeons. We here present a review of recent controversies of the use of laparoscopy in colorectal surgery, such as in rectal cancer operations, the possibility of reproducing complete mesocolon excision, and the benefits of intracorporeal anastomosis after right hemicolectomy. We also describe the results of latest innovations such as single incision laparoscopic surgery, robotic surgery and natural orifice transluminal endoscopic surgery for colon and rectal diseases.
文摘This paper was to explore the mechanism of single basal application of controlled-release fertilizers for increasing yield of rice （Oryza sativa L.）. Pot trials and cylinder trials were carried out from 2002 to 2005 to study the influences of single basal application of 3 controlled-release fertilizers on the changes of soil available N, root development, senescence and lodging resistance at late growth stages. Results showed that at 30 days after fertilization, single basal application of controlled-release fertilizers coated with vegetal-substance （CRF1） and polymer materials （CRF3） increased soil available N to 12.0 and 147.9%, respectively, in comparison to split fertilization of rice-specific fertilizer （RSF1）. Treatments of the two CRFs obviously benefited the development of root system, resulting in greater rice root weights with extensive distribution and higher root activity. In addition, the two CRF treatments, in comparison to RSF1, enhanced chlorophyll consents of the flag leaves to 9.5 and 15.5%, and soluble protein up to 89.7 and 108.0% respectively. Application of the two CRFs also made the base of rice stems strong and large, declined the proportion of shoot and root, increased root depth index. Though relatively low K rate, single basal application of the CRF3 coated with NH4MgPO4 could also promote the development of root system, enhance root activity and some physiological functions of flag leaves. Based on these results, it was concluded that major mechanisms for increasing rice yield by single basal application of the CRFs should be attributed to grater soil available N supply, superior development of root systems, better nutrient absorption capacity, slower senescence and enhancement of lodging resistance at late stages.
基金supported by the National Science Funds for Distinguished Young Scholar of China (Grant No. 51125017)the National Basic Research Program of China (Grant Nos. 2010CB226804,2011CB201201)+2 种基金the National Natural Science Foundation of China (Grant No. 50974125)the International Cooperation Project of Ministry of Science & Technology of China (Grant No. 2012DFA60760-2)NSFC International Cooperation and Exchange Program (Grant No. 51120145001)
文摘The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior.The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has been greatly concerned in the fields of geotechnical,mining,geological,and petroleum engineering.In order to probe the mechanism of fluid flow and the effects of rough structures,we conducted a few laboratory tests of fluid flow through single rough fractures,in which the Weierstrass-Mandelbrot fractal function and PMMA material were employed to produce the fracture models with various fractal roughnesses.A high-speed video camera was employed to record the fluid flow through the entire single rough fracture with a constant hydraulic pressure.The properties of fluid flow varying with the fracture roughness and the influences of the rough structure were analyzed.The components of flow resistance of a single rough fracture were discussed.A fractal model was proposed to relate the fluid resistance to the fracture roughness.A fractal equivalent permeability coefficient of a single rough fracture was formulated.This study aims to provide an experimental basis and reference for better understanding and quantitatively relating the fluid flow properties to the structures of rock fractures.
文摘目的比较血液灌流(HP)次数对重度急性有机磷农药中毒患者的临床疗效。方法回顾性分析2014年1月-2018年7月安徽理工大学附属亳州市人民医院收治的86例急性重度有机磷农药中毒患者,根据HP治疗次数分为对照组(HP 0次,26例),HP单次组(HP 1次,31例),HP多次组(HP≥2次,29例)。比较3组患者长托宁和解磷定总用量,血清胆碱酯酶活性恢复80%时间(h1)、昏迷时间(h2)、住院时间(h3)、机械通气时间(h4)及中间综合征、中毒反跳、心律失常、多器官功能障碍综合征发生率、病死率。结果对照组、HP单次组、HP多次组长托宁总量[(38.28±11.33)mg、(25.62±9.57)mg、(16.54±9.45)mg]和解磷定总量[(22.35±5.45)mg、(16.53±3.64)mg、(10.22±2.45)mg]依次减少(均P<0.05),h1[(15.32±3.42)h,(10.26±2.04)h,(7.32±3.64)h],h2[(96.23±8.22)h,(46.28±7.69)h,(28.56±7.21)h],h3[(18.21±3.22)d,(13.52±3.64)d,(8.23±2.33)d]、h4[(136.42±18.68)h,(92.46±16.28)h,(47.28±15.42)h]依次缩短(均P<0.05),入院72 h APACHE-Ⅱ评分(18.23±4.12,15.25±3.06,12.52±2.08)依次降低(P<0.05)。HP多次组中间综合征、反跳、MODS发生例数少于对照组和HP单次组,差异具统计学意义(均P<0.05)。HP多次组和HP单次组心律失常例数均少于对照组(均P<0.05)。病死数构成3组间差异无统计学意义(P>0.05)。结论重度有机磷中毒患者多次行血液灌流临床治疗效果可,并发症少。
文摘AIM： To study the alterations in p53 gene among Indian gastric cancer patients and to correlate them with the various clinicopathological parameters. METHODS： A total of 103 gastric cancer patients were included in this study. The p53 alterations were studied by both immunohistochemical method as well as polymerase chain reaction （PCR）-single strand conformation polymorphism （SSCP） analysis. We only studied four （exon 5, 6, 7, and 8） of the 11 ,p53 exons. The alterations in p53 were also correlated with respect to various clinicopathological parameters. RESULTS： Among 103 cases, p53 over-expression and alteration were detected in 37 （35.92%） and 19 （18.44%） cases, respectively. Most of the ,p53 alterations were found at exon 5 （31.54%）, followed by exon 6 （26.31%）, exon 7 （21.04%） and exon 8 （21.04%）. A significant correlation of p53 overexpression was found with p53 alteration （P = 0.000）. Concordance between ,p53 alteration （as detected by SSCP） and over-expression [as detected by immunohistochemistry （IHC）] was found in 75% cases. We found that IHC-positive/SSCP-negative cases accounted for 21% of cases and IHC-negative/SSCP- positive cases accounted for remaining 4% cases. CONCLUSION： Our results show that p53 gene mutations are significantly correlated with p53 protein over-expression, with 75% concordance in over-expression and alteration in the p53 gene, but 25% disconcordance also cautions against the assumption that p53 over-expression is always associated with a gene mutation. There may be other mechanisms responsible for stabilization and accumulation of p53 protein with no evidence of gene mutation that reflect an accumulation of a non-mutated protein, or a false negative SSCP result.
基金the NationalNatural Science Foundation of China(Grant Nos.40132010 ,40125007) the State Key Fundamental Research Project(Grant No.1999043209).
文摘In the eastern Nanling Range there exists the early Yanshanian syenite-granite assemblage. A representative example is the Pitou-Tabei complex composed of the Tabei syenite pluton and the Pitou syenogranite pluton in southern Jiangxi Province. U-Pb zircon dating yields ages of 188.6±2.2 Ma for the Tabei pluton and 186.3±1.1 Ma for the Pitou pluton. The Tabei syenite is characterized by relatively low SiO2 content (62.40% - 68.75%), high alkalis (K2O+Na2O = 10.56%-11.96%), low percent K2O/Na2O ratios (0.56-0.93), metaluminous fea- ture (A/CNK = 0.80-1.00), enrichment in LILE (Rb, Ba, K) and HFSE (Th, U, Nb, Ta, Zr, and so on), weakly negative to positive Eu anomalies (δ Eu = 0.63-1.82), relatively low (87Sr/86Sr)i (0.70412-0.70543), and relatively high ε Nd(t) (3.14-3.52). The Pitou syenogranite is charac- terized by high silicon content (SiO2 = 71.06%-76.28%), relatively low alkalis (K2O+Na2O = 8.10%-9.80%), high percent K2O/Na2O ratios (1.22-1.94), metaluminous feature (A/CNK = 0.94-1.07), enrichment in Rb, Th (U), K, depletion in Ba, Nb, Ta, Sr, P , Zr, Ti, high ΣREE (av- eraging 451.03 μg/g), strong negative Eu anomalies (δ Eu = 0.27-0.33), relatively high (87Sr/86Sr)i (0.70805-0.70912), and relatively low ε Nd( t ) (?5.35-?6.29). The Tabei syenite and Pitou syenogranite both have the characteristics of A-type granites. The former is considered to be from the asthenosphere mantle, and the latter was the product of the crust-mantle mixture. They both were probably formed in a rifting setting.
文摘Background Genetic factors are believed to play a role in the individual susceptibility to chronic obstructive pulmonary disease (COPD). A single nucleotide polymorphism (SNP) of tumour necrosis factor-α (TNF-α) has been reported but inconsistent results may arise from different populations and phenotypes of COPD. There are only a few published studies of interleukin-13 (IL-13) SNPs on COPD. The SNPs of TNF-α and IL-13 have not been studied in the Chinese population. This research was conducted to study the frequencies of IL-13 gene promoter 1055 (IL-13-1055) and TNF-α gene-308 polymorphisms in the patients with COPD and to investigate the effect of those genetic polymorphisms on COPD in the Chinese population.Methods A cohort of COPD patients and age matched controls were recruited from an inpatient hospital service in Beijing. Venous blood was obtained and genomic DNA was extracted from peripheral blood monocytes using standard method. Genomic DNA was used as a template for amplification by polymerase chain reaction (PCR) to determine the polymorphism at -1055 in the IL-13 gene promoter region. PCR restriction fragment length polymorphism (RFLP) was used to determine polymorphisms in the TNF-α gene-308 position. The products were investigated by sequence analysis also. Results One hundred and eleven COPD patients and 97 controls were studied. Seventy-five cases were current smokers in COPD patients and 36 were current smokers in controls. The frequencies of TT genotype in the IL-13 gene promoter region were 11.7% (13/111) in the COPD group and 13.4% (13/97) in the controls (P=0.713). However, the OR value of TT genotype was significantly increased to 6.4 (95% CI 1.62-25.39) in the smokers with COPD. TT genotype was also positively related to family history of COPD, OR=7.7 (95% CI 1.37-43.80). The frequencies of A allele in the TNF-α gene were 5.9% in COPD and 3.1% in controls (P=0.131). The OR value of A allele was 5.0 (95% CI 1.011 to 25.059) in smokers with COPD. Conclusions There is no significant diff
文摘Background Ossification of the posterior longitudinal ligament （OPLL） has a strong genetic background. Previous studies have shown that bone morphogenetic protein-2 （BMP2） and BMP2 mRNA are expressed in ossifying matrix and chondrocytes adjacent to cartilaginous areas of OPLL tissues and mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas. It is suggested that BMP2 plays different roles in the different stages of development of OPLL. However, it remains unknown which factors induce ligament cells to produce BMP2. Methods OPLL patients （n=-192） and non-OPLL controls （n=304） were studied. Radiographs of the cervical spine were analyzed for extent of OPLL. We investigated whether single nucleotide polymorphisms of exons 3（-726） T/C and 3（-583） NG in the BMP2 gene are statistically associated with genetic susceptibility to OPLL in Chinese Han subjects. Results There was no statistical difference between the occurrence of exons 3（-726） T/C and 3（-583） NG and the occurrence of OPLL in the cervical spine. However, there was a significant association between occurrence of exon 3（-726） T/C polymorphism and occurrence of OPLL in males of cases and controls in the cervical spine. In addition, no significant association was found between the exons 3（-726） T/C and 3（-583） A/G with number of ossified cervical vertebrae in OPLL patients. Conclusions Exon 3（-583） A/G polymorphism in BMP2 gene is not associated with the occurrence and the extent of OPLL in the cervical spine. Chinese Han male patients with TC and CC genotypes in exon 3（-726） T/C have genetic susceptibility to OPLL but not to more extensive OPLL in the cervical spine.
