Gastrointestinal stromal tumors(GISTs) are the most common malignant subepithelial lesions(SELs) of the gastrointestinal tract. They originate from the interstitial cells of Cajal located within the muscle layer and a...Gastrointestinal stromal tumors(GISTs) are the most common malignant subepithelial lesions(SELs) of the gastrointestinal tract. They originate from the interstitial cells of Cajal located within the muscle layer and are characterized by over-expression of the tyrosine kinase receptor KIT. Pathologically, diagnosis of a GIST relies on morphology and immunohistochemistry [KIT and/or discovered on gastrointestinal stromal tumor 1(DOG1) is generally positive]. The prognosis of this disease is associated with the tumor size and mitotic index. The standard treatment of a GIST without metastasis is surgical resection. A GIST with metastasis is usually only treated by tyrosine kinase inhibitors without radical cure; thus, early diagnosis is the only way to improve its prognosis. However, a GIST is usually detected as a SEL during endoscopy, and many benign and malignant conditions may manifest as SELs. Conventional endoscopic biopsy is difficult for tumors without ulceration. Most SELs have therefore been managed without a histological diagnosis. However, a favorable prognosis of a GIST is associated with early histological diagnosis and R0 resection. Endoscopic ultrasonography(EUS) and EUS-guided fine needle aspiration(EUSFNA) are critical for an accurate diagnosis of SELs. EUSFNA is safe and effective in enabling an early histological diagnosis and adequate treatment. This review outlines the current evidence for the diagnosis and management of GISTs, with an emphasis on early management of small SELs.展开更多
A thorough understanding of the genetic basis of rice grain traits is critical for the improvement of rice （Oryza sativa L.） varieties. In this study, we generated an F2 population by crossing the large-grain japoni...A thorough understanding of the genetic basis of rice grain traits is critical for the improvement of rice （Oryza sativa L.） varieties. In this study, we generated an F2 population by crossing the large-grain japonica cultivar CW23 with Peiai 64 （PA64）, an elite indica small-grain cultivar. Using QTL analysis, 17 QTLs for five grain traits were detected on four different chromosomes. Eight of the QTLs were newly-identified in this study. In particular, qGL3-1, a newly-identified grain length QTL with the highest LOD value and largest phenotypic variation, was fine-mapped to the 17 kb region of chromosome 3. A serine/threonine protein phosphatase gene encoding a repeat domain containing two Kelch motifs was identified as the unique candidate gene corresponding to this QTL. A comparison of PA64 and CW23 sequences revealed a single nucleotide substitution （C→A） at position 1092 in exon 10, resulting in replacement of Asp （D） in PA64 with Glu （E） in CW23 for the 364th amino acid. This variation is located at the D position of the conserved sequence motif AVLDT of the Kelch repeat. Genetic analysis of a near-isogenic line （NIL） for qGL3-1 revealed that the allele qGL3-1 from CW23 has an additive or partly dominant effect, and is suitable for use in molecular marker-assisted selection.展开更多
Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecos...Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine （Pinus resinosa） plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature （Tsoil） and soil moisture （Msoil） were higher in the thinning plots than those in the controls. Litter fall removal had significant effects on Tsoil and Msoil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.展开更多
Disparity in the root morphology of six rice(Oryza sativa L.) genotypes varying in potassium(K) efficiency was studied with three K levels:5 mg/L(low),10 mg/L(moderate) and 40 mg/L(adequate) in hydroponic culture. Mor...Disparity in the root morphology of six rice(Oryza sativa L.) genotypes varying in potassium(K) efficiency was studied with three K levels:5 mg/L(low),10 mg/L(moderate) and 40 mg/L(adequate) in hydroponic culture. Morphological parameters included root length,surface area,volume and count of lateral roots,as well as fine(diameter<0.2 mm) and thick(diameter>0.2 mm) roots. The results indicate that the root growth of all genotypes was reduced under low K,but moderate K deficiency increased the root length of the efficient genotypes. At deficient and moderate K levels,all the efficient rice genotypes developed more fine roots(diameter<0.2 mm) than the inefficient ones. Both fine root count and root surface area were found to be the best parameters to portray K stress in rice. In accordance with the root morphology,higher K concentrations were noted in shoots of the efficient genotypes when grown at moderate and deficient K levels,indicating that root morphology parameters are involved in root uptake for K and in the translocation of K up to shoots. K deficiency affected not only the root morphology,but also the root ultra-structure. The roots of high-efficient genotypes had stronger tolerance to K deficient stress for root membrane damage,and could maintain the developed root architecture to adapt to the low K growth medium.展开更多
AIM： to evaluate the role of endoscopic ultrasonographyguided fine needle aspiration （EUS-FNA） in the preoperative diagnosis of gastrointestinal stromal tumor （GIST）.METHODS： From September 2002 to June 2006, Fi...AIM： to evaluate the role of endoscopic ultrasonographyguided fine needle aspiration （EUS-FNA） in the preoperative diagnosis of gastrointestinal stromal tumor （GIST）.METHODS： From September 2002 to June 2006, Fiftythree consecutive EUS-FNAs of GI tract subepithelial hypoechoic tumors with continuity to proper muscle layer suspected as GIST by standard EUS were evaluated prospectively. The reference standards for the final diagnosis were surgery （n = 31）, or clinical follow-up （n = 22）. Additionally, immunophenotyping of specimens obtained by EUS-FNA and surgical resection specimens were compared.RESULTS： In 2 cases puncture was not performed because of anatomical problems. The collection rate of adequate specimens from the GI tract subepithelial hypoechoic tumor with continuity to proper muscle layer was 82% （42/51）. The diagnostic rate for the tumor less than 2 cm, 2 to 4 cm, and 4 cm or more were 71% （15/21）, 86% （18/21）, and 100% （9/9）,respectively. In 29 surgically resected cases, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of EUS-FNA using immunohistochemical analysis of GIST were 100%（24/24）, 80% （4/5）, 96% （24/25）, 100% （4/4）, and 97% （28/29）, respectively. No major complications were encountered.CONCLUSION： EUS-FNA with immunohistochemical analysis is a safe and accurate method in the pretherapeutic diagnosis of GIST. It should be taken into consideration in decision making, especially in early diagnosis following minimal invasive surgery for GIST.展开更多
Green-revertible albino is a novel type of chlorophyll deficiency in rice （Oryza sativa L.）, which is helpful for further research in chlorophyll synthesis and chloroplast development to illuminate their molecular m...Green-revertible albino is a novel type of chlorophyll deficiency in rice （Oryza sativa L.）, which is helpful for further research in chlorophyll synthesis and chloroplast development to illuminate their molecular mechanism. In the previous study, we had reported a single recessive gene, gra（t）, controlling this trait on the long arm of chromosome 2. In this paper, we mapped the gra（t） gene using 1,936 recessive individuals with albino phenotype in the F2 population derived from the cross between themo-photoperiod-sensitive genic male-sterile （T/PGMS） line Pei＇ai 64S and the spontaneous mutant Qiufeng M. Eventually, it was located to a confined region of 42.4 kb flanked by two microsatellite markers RM2-97 and RM13553. Based on the annotation results of RiceGAAS system, 11 open reading frames （ORFs） were predicted in this region. Among them, ORF6 was the most possible gene related to chloroplast development, which encoded the chloroplast protein synthesis elongation factor Tu in rice. Therefore, we designated it as the candidate gene of gra（t）. Sequence analysis indicated that only one base substitution C to T occurred in the coding region, which caused a missense mutation （Thr to Ile） in gra（t） mutant. These results are very valuable for further study on gra（t） gene.展开更多
The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine parti...The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particleaccumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.展开更多
Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes...Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes of fine particles （PM2.5） and their carbonaceous fractions are scarce. In this article, abundance, sources, seasonal and spatial variations, distribution of organic carbon （OC） and elemental carbon （EC） in PM2.5, were studied at suburban, urban and industrial sites in Xiamen during four season-representative months in 2009-2010. PM2.5 samples were collected with middle volume sampler and were analyzed for OC and EC with thermal optical transmittance （TOT） method. Results showed that the annual average PM2.5 concentrations were 63.88-74.80 Ixg/m3 at three sites. While OC and EC concentrations were in the range of 15.81-19.73 [xg/m3 and 2.74-3.49 ~tg/m3, respectively, and clearly presented the summer minima and winter maxima in this study. The carbonaceous aerosol accounted for 42.8%-47.3% of the mass of PMzs. The annual average of secondary organic carbon （SOC） concentrations in Xiamen were 9.23-11.36 ~g/m3, accounting for approximately 56% of OC. Strong correlations between OC and EC was found in spring （R2 = 0.50） and autumn （R2 = 0.73）, suggesting that there were similar emission and transport processes for carbonaceous aerosols in these two seasons, while weak correlations were found in summer （R2 = 0.33） and winter （R2 = 0.41）. The OCI＇EC ratios in PM2.5 varied from 2.1 to 8.7 with an annual average of 5.7, indicating that vehicle exhaust, coal smoke and biomass burning were main source apportionments of carbonaceous fractions in Xiamen.展开更多
As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to ...As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to improve flotation performance of fine and ultrafine particles, there is still much more to be done. In this paper, the effects of nano-microbubbles （nanobuhbles and microbubbles） on the flotation of fine （-38 ＋ 14.36 μm） and ultrafine （-14.36 ＋ 5μm） chalcopyrite particles were investigated in a laboratory scale Denver flotation cell. Nano-microbubbles were generated using a specially-designed nano- microbubble generator based on the cavitation phenomenon in Venturi tubes. In order to better under- stand the mechanisms of nano-microbubble enhanced froth flotation of fine and ultrafine chalcopyrite particles, the nano-microbubble size distribution, stability and the effect of frother concentration on nano- bubble size were also studied by a laser diffraction method. Comparative flotation tests were performed in the presence and absence of nano-microbubbles to evaluate their impact on the fine and ultrafine chalcopyrite particle flotation recovery. According to the results, the mean size of nano-microbubbles increased over time, and decreased with increase of frother concentration. The laboratory-scale flotation test results indicated that flotation recovery of chalcopyrite fine and ultrafine particles increased by approximately 16-21% in the presence of nano-microbubbles, depending on operating conditions of the process. The presence of nano-microbubbles increased the recovery of ultrafine particles （-14.36 ＋ 5 μm） more than that of fine particles （-38 ＋ 14.36 μm）. Another major advantage is that the use of nano-microbubbles reduced the collector and frother consumptions by up to 75% and 50%, respectively.展开更多
During November–December 2010 aerosol scattering coefficients were monitored using a single-waved （525 nm） Nephelometer at a regional monitoring station in the central Pearl River Delta region and 24-hr fine partic...During November–December 2010 aerosol scattering coefficients were monitored using a single-waved （525 nm） Nephelometer at a regional monitoring station in the central Pearl River Delta region and 24-hr fine particle （PM 2.5） samples were also collected during the period using quartz filters for the analysis of major chemical components including organic carbon （OC）,elemental carbon （EC）,sulfate,nitrate and ammonium.In average,these five components accounted for about 85% of PM 2.5 mass and contributed 42% （OC）,19% （SO 4 2 -）,12% （NO 3 -）,8.4% （NH 4＋） and 3.7% （EC）,to PM 2.5 mass.A relatively higher mass scattering efficiency of 5.3 m 2/g was obtained for fine particles based on the linear regression between scattering coefficients and PM 2.5 mass concentrations.Chemical extinction budget based on IMPROVE approach revealed that ammonium sulfate,particulate organic matter,ammonium nitrate and EC in average contributed about 32%,28%,20% and 6% to the light extinction coefficients,respectively.展开更多
文摘Gastrointestinal stromal tumors(GISTs) are the most common malignant subepithelial lesions(SELs) of the gastrointestinal tract. They originate from the interstitial cells of Cajal located within the muscle layer and are characterized by over-expression of the tyrosine kinase receptor KIT. Pathologically, diagnosis of a GIST relies on morphology and immunohistochemistry [KIT and/or discovered on gastrointestinal stromal tumor 1(DOG1) is generally positive]. The prognosis of this disease is associated with the tumor size and mitotic index. The standard treatment of a GIST without metastasis is surgical resection. A GIST with metastasis is usually only treated by tyrosine kinase inhibitors without radical cure; thus, early diagnosis is the only way to improve its prognosis. However, a GIST is usually detected as a SEL during endoscopy, and many benign and malignant conditions may manifest as SELs. Conventional endoscopic biopsy is difficult for tumors without ulceration. Most SELs have therefore been managed without a histological diagnosis. However, a favorable prognosis of a GIST is associated with early histological diagnosis and R0 resection. Endoscopic ultrasonography(EUS) and EUS-guided fine needle aspiration(EUSFNA) are critical for an accurate diagnosis of SELs. EUSFNA is safe and effective in enabling an early histological diagnosis and adequate treatment. This review outlines the current evidence for the diagnosis and management of GISTs, with an emphasis on early management of small SELs.
基金supported by grants from the Geneti-cally Modified Organisms Breeding Major Projects of China(2011ZX08001-004-009)the National Natural Science Foun-dation of China(30900881)+2 种基金the Jiangxi Province Major Science and Technology Projects and Super Hybrid Rice BreedingDemonstration and Dissemination Projects(20114ABF03105)the Natural Science Foundation of Shandong Province(Y2006D22)
文摘A thorough understanding of the genetic basis of rice grain traits is critical for the improvement of rice （Oryza sativa L.） varieties. In this study, we generated an F2 population by crossing the large-grain japonica cultivar CW23 with Peiai 64 （PA64）, an elite indica small-grain cultivar. Using QTL analysis, 17 QTLs for five grain traits were detected on four different chromosomes. Eight of the QTLs were newly-identified in this study. In particular, qGL3-1, a newly-identified grain length QTL with the highest LOD value and largest phenotypic variation, was fine-mapped to the 17 kb region of chromosome 3. A serine/threonine protein phosphatase gene encoding a repeat domain containing two Kelch motifs was identified as the unique candidate gene corresponding to this QTL. A comparison of PA64 and CW23 sequences revealed a single nucleotide substitution （C→A） at position 1092 in exon 10, resulting in replacement of Asp （D） in PA64 with Glu （E） in CW23 for the 364th amino acid. This variation is located at the D position of the conserved sequence motif AVLDT of the Kelch repeat. Genetic analysis of a near-isogenic line （NIL） for qGL3-1 revealed that the allele qGL3-1 from CW23 has an additive or partly dominant effect, and is suitable for use in molecular marker-assisted selection.
基金Supported by the "948" Grant of the National Forestry Administration of China (No.2007-4-19)the Special Grantof Chinese Forestry Public Benefits (Nos.200804030 and 2007-4-15)the Provincial Fund for Distinguished Young Scholars of Hunan, China (No.07JJ1004)
文摘Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine （Pinus resinosa） plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature （Tsoil） and soil moisture （Msoil） were higher in the thinning plots than those in the controls. Litter fall removal had significant effects on Tsoil and Msoil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.
基金Project supported by the Program for Changjiang Scholars andInnovative Research Team in University of China (No. IRT0536)the National Basic Research Program (973) of China (No. 30740011)
文摘Disparity in the root morphology of six rice(Oryza sativa L.) genotypes varying in potassium(K) efficiency was studied with three K levels:5 mg/L(low),10 mg/L(moderate) and 40 mg/L(adequate) in hydroponic culture. Morphological parameters included root length,surface area,volume and count of lateral roots,as well as fine(diameter<0.2 mm) and thick(diameter>0.2 mm) roots. The results indicate that the root growth of all genotypes was reduced under low K,but moderate K deficiency increased the root length of the efficient genotypes. At deficient and moderate K levels,all the efficient rice genotypes developed more fine roots(diameter<0.2 mm) than the inefficient ones. Both fine root count and root surface area were found to be the best parameters to portray K stress in rice. In accordance with the root morphology,higher K concentrations were noted in shoots of the efficient genotypes when grown at moderate and deficient K levels,indicating that root morphology parameters are involved in root uptake for K and in the translocation of K up to shoots. K deficiency affected not only the root morphology,but also the root ultra-structure. The roots of high-efficient genotypes had stronger tolerance to K deficient stress for root membrane damage,and could maintain the developed root architecture to adapt to the low K growth medium.
文摘AIM： to evaluate the role of endoscopic ultrasonographyguided fine needle aspiration （EUS-FNA） in the preoperative diagnosis of gastrointestinal stromal tumor （GIST）.METHODS： From September 2002 to June 2006, Fiftythree consecutive EUS-FNAs of GI tract subepithelial hypoechoic tumors with continuity to proper muscle layer suspected as GIST by standard EUS were evaluated prospectively. The reference standards for the final diagnosis were surgery （n = 31）, or clinical follow-up （n = 22）. Additionally, immunophenotyping of specimens obtained by EUS-FNA and surgical resection specimens were compared.RESULTS： In 2 cases puncture was not performed because of anatomical problems. The collection rate of adequate specimens from the GI tract subepithelial hypoechoic tumor with continuity to proper muscle layer was 82% （42/51）. The diagnostic rate for the tumor less than 2 cm, 2 to 4 cm, and 4 cm or more were 71% （15/21）, 86% （18/21）, and 100% （9/9）,respectively. In 29 surgically resected cases, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of EUS-FNA using immunohistochemical analysis of GIST were 100%（24/24）, 80% （4/5）, 96% （24/25）, 100% （4/4）, and 97% （28/29）, respectively. No major complications were encountered.CONCLUSION： EUS-FNA with immunohistochemical analysis is a safe and accurate method in the pretherapeutic diagnosis of GIST. It should be taken into consideration in decision making, especially in early diagnosis following minimal invasive surgery for GIST.
基金supported by the National High-tech Research and Development Program of China (863 Program) (No. 2006AA100101)the National Science and Technology Support Program (No. 2006BAD01A01-5)+1 种基金Special Program for Rice Scientific Research of Ministry of Agriculture (No. nyhyzx 07-001-006)Super Rice Breeding and Demonstration Program of Ministry of Agriculture, and Jiangsu Selfinnovation Fund for Agricultural Science and Technology (No. CX[08]603).
文摘Green-revertible albino is a novel type of chlorophyll deficiency in rice （Oryza sativa L.）, which is helpful for further research in chlorophyll synthesis and chloroplast development to illuminate their molecular mechanism. In the previous study, we had reported a single recessive gene, gra（t）, controlling this trait on the long arm of chromosome 2. In this paper, we mapped the gra（t） gene using 1,936 recessive individuals with albino phenotype in the F2 population derived from the cross between themo-photoperiod-sensitive genic male-sterile （T/PGMS） line Pei＇ai 64S and the spontaneous mutant Qiufeng M. Eventually, it was located to a confined region of 42.4 kb flanked by two microsatellite markers RM2-97 and RM13553. Based on the annotation results of RiceGAAS system, 11 open reading frames （ORFs） were predicted in this region. Among them, ORF6 was the most possible gene related to chloroplast development, which encoded the chloroplast protein synthesis elongation factor Tu in rice. Therefore, we designated it as the candidate gene of gra（t）. Sequence analysis indicated that only one base substitution C to T occurred in the coding region, which caused a missense mutation （Thr to Ile） in gra（t） mutant. These results are very valuable for further study on gra（t） gene.
基金supported by the key international collaborative project of Natural Science Foundation of China(No.41520104002)
文摘The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particleaccumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-453,KZCX2-YW-JS404,KZCX2-EW-408)the Commonweal Program of Environment Protection Department of China (No. 201009004)the Program of Bureau of Science and Technology,Xiamen (No. 3502Z20081117,350205Z20095001)
文摘Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes of fine particles （PM2.5） and their carbonaceous fractions are scarce. In this article, abundance, sources, seasonal and spatial variations, distribution of organic carbon （OC） and elemental carbon （EC） in PM2.5, were studied at suburban, urban and industrial sites in Xiamen during four season-representative months in 2009-2010. PM2.5 samples were collected with middle volume sampler and were analyzed for OC and EC with thermal optical transmittance （TOT） method. Results showed that the annual average PM2.5 concentrations were 63.88-74.80 Ixg/m3 at three sites. While OC and EC concentrations were in the range of 15.81-19.73 [xg/m3 and 2.74-3.49 ~tg/m3, respectively, and clearly presented the summer minima and winter maxima in this study. The carbonaceous aerosol accounted for 42.8%-47.3% of the mass of PMzs. The annual average of secondary organic carbon （SOC） concentrations in Xiamen were 9.23-11.36 ~g/m3, accounting for approximately 56% of OC. Strong correlations between OC and EC was found in spring （R2 = 0.50） and autumn （R2 = 0.73）, suggesting that there were similar emission and transport processes for carbonaceous aerosols in these two seasons, while weak correlations were found in summer （R2 = 0.33） and winter （R2 = 0.41）. The OCI＇EC ratios in PM2.5 varied from 2.1 to 8.7 with an annual average of 5.7, indicating that vehicle exhaust, coal smoke and biomass burning were main source apportionments of carbonaceous fractions in Xiamen.
基金the Tarbiat Modares University (TMU), the Iran Mineral Processing Research Center (IMPRC) and the IMIDRO for the technical assistance and financial support
文摘As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to improve flotation performance of fine and ultrafine particles, there is still much more to be done. In this paper, the effects of nano-microbubbles （nanobuhbles and microbubbles） on the flotation of fine （-38 ＋ 14.36 μm） and ultrafine （-14.36 ＋ 5μm） chalcopyrite particles were investigated in a laboratory scale Denver flotation cell. Nano-microbubbles were generated using a specially-designed nano- microbubble generator based on the cavitation phenomenon in Venturi tubes. In order to better under- stand the mechanisms of nano-microbubble enhanced froth flotation of fine and ultrafine chalcopyrite particles, the nano-microbubble size distribution, stability and the effect of frother concentration on nano- bubble size were also studied by a laser diffraction method. Comparative flotation tests were performed in the presence and absence of nano-microbubbles to evaluate their impact on the fine and ultrafine chalcopyrite particle flotation recovery. According to the results, the mean size of nano-microbubbles increased over time, and decreased with increase of frother concentration. The laboratory-scale flotation test results indicated that flotation recovery of chalcopyrite fine and ultrafine particles increased by approximately 16-21% in the presence of nano-microbubbles, depending on operating conditions of the process. The presence of nano-microbubbles increased the recovery of ultrafine particles （-14.36 ＋ 5 μm） more than that of fine particles （-38 ＋ 14.36 μm）. Another major advantage is that the use of nano-microbubbles reduced the collector and frother consumptions by up to 75% and 50%, respectively.
基金supported by the National Natural Science Foundation of China (No. 40821003,41025012)NSFC-Guangdong Joint Funds (No. U0833003)+1 种基金the Natural Science Foundation of Guangdong (No. 7118013)the Bureau of Science,Technology and Information of Guangzhou (No. 2010U1-E00601-2)
文摘During November–December 2010 aerosol scattering coefficients were monitored using a single-waved （525 nm） Nephelometer at a regional monitoring station in the central Pearl River Delta region and 24-hr fine particle （PM 2.5） samples were also collected during the period using quartz filters for the analysis of major chemical components including organic carbon （OC）,elemental carbon （EC）,sulfate,nitrate and ammonium.In average,these five components accounted for about 85% of PM 2.5 mass and contributed 42% （OC）,19% （SO 4 2 -）,12% （NO 3 -）,8.4% （NH 4＋） and 3.7% （EC）,to PM 2.5 mass.A relatively higher mass scattering efficiency of 5.3 m 2/g was obtained for fine particles based on the linear regression between scattering coefficients and PM 2.5 mass concentrations.Chemical extinction budget based on IMPROVE approach revealed that ammonium sulfate,particulate organic matter,ammonium nitrate and EC in average contributed about 32%,28%,20% and 6% to the light extinction coefficients,respectively.
