Low collateral damage weapons achieve controlled personnel injury through the coupling of shock waves and particle swarms,where the particle swarms arise from the high-explosive dispersion of compacted metal particle ...Low collateral damage weapons achieve controlled personnel injury through the coupling of shock waves and particle swarms,where the particle swarms arise from the high-explosive dispersion of compacted metal particle ring.To investigate the dynamic response of the human target under combined shock waves and particle swarms loading,a physical human surrogate torso model(HSTM)was developed,and the dynamic response test experiment was conducted under the combined loading.The effects of particle size on the loading parameters,the damage patterns of the ballistic plate and HSTM,and the dynamic response parameters of the HSTM with and without protection are mainly analyzed.Our findings revealed that particle swarms can effectively delay the shock wave attenuation,especially the best effect when the particle size was 0.28–0.45 mm.The ballistic plate mainly exhibited dense perforation of the outer fabric and impacted crater damage of ceramic plates,whereas the unprotected HSTM was mainly dominated by high-density and small-size ballistic cavity group damage.The peak values of the dynamic response parameters for the HSTM under combined loading were significantly larger than those under bare charge loading,with multiple peaks observed.Under unprotected conditions,the peak acceleration of skeletons and peak pressure of organs increased with the particle size.Under protected conditions,the particle size,the number of particles hit,and the fit of the ballistic plate to the HSTM together affected the dynamic response parameters of the HSTM.展开更多
Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale applica...Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale application.However,their practical implementation is hindered by the rapid voltage/capacity decay during cycling and the long-standing problem of redox kinetics due to their poor ionic conductivity based on the ordered honeycomb structure.In this study,the kinetic and thermodynamic properties of intralayer disordered and ordered Li-rich full-Mn-based cathode materials were compared,demonstrating that the disordered R3m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(D-LMO)delivers a significant advantage of rate capability over the ordered C2/m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(O-LMO).Meanwhile,the D-LMO keeps superior capacity retention of up to 99%after 50 cycles under 25 mAg^(-1).In comparsion,the capacity retention of the O-LMO drops to just 70%,and its average discharge voltage is 0.2 V lower than that of the D-LMO.Herein,we conducted systematic density functional theory(DFT)simulations,focusing on the electronic structure modulation governing the voltage platform between the ordered and disordered phases.The ab initio molecular dynamics(AIMD)results indicated that the energy of the intralayer disordered structure fluctuates around the equilibrium position without any abrupt drops,demonstrating excellent stability.This study enhances the understanding of intralayer disordered full-Mn Li-rich material and provides insights into the design of low-cost,high-performance cathode materials for Li-ion batteries.展开更多
AIM:To investigate the expression of co-stimulatorymolecule B7-H3 in gastric carcinoma and adenomatissue as well as normal gastric tissue and to explore therelationship between B7-H3 expression and pathologicalfeature...AIM:To investigate the expression of co-stimulatorymolecule B7-H3 in gastric carcinoma and adenomatissue as well as normal gastric tissue and to explore therelationship between B7-H3 expression and pathologicalfeatures and prognosis of gastric carcinoma.METHODS:B7-H3 expression was detected in 102samples of human gastric carcinoma and 10 samples ofgastric adenoma and 10 samples of normal gastric tissueby immunohistochemical assay.Correlation betweenthe expression of B7-H3 and the patients'age,sex,gastric carcinoma locus,tumor size,tissue type,tumorinfiltration depth,differentiation degree,lymph nodemetastasis,and survival time was analyzed.RESULTS:B7-H3 was expressed in all gastric adenomasamples and in 58.8% samples of gastric carcinoma.B7-H3 expression in gastric carcinoma samples wasnot related with the patients'age,sex,lymph nodemetastasis,and tumor size(P>0.05),but with thesurvival time,infiltration depth of tumor and tissue type.CONCLUSION:Detection of B7-H3 expression in gastriccarcinoma tissue is beneficial to the judgment of theprognosis of gastric carcinoma patients and the choice oftreatment.展开更多
Pure red cell aplasia （PRCA） due to parvovirus B19 （PVB19） infectiori after solid organ transplantation has been rarely reported and most of the cases were renal transplant recipients, Few have been described afte...Pure red cell aplasia （PRCA） due to parvovirus B19 （PVB19） infectiori after solid organ transplantation has been rarely reported and most of the cases were renal transplant recipients, Few have been described after liver transplantation. Moreover, little information on the management of this easily recurring disease is available at present. We describe the first case of a Chinese liver transplant recipient with PVB19-induced PRCA during immunosuppressive therapy. The patient suffered from progressive anemia with the lowest hemoglobin level of 21 g/L. Bone marrow biopsy showed selectively inhibited erythropoiesis with giant pronormoblasts. Detection of PVB19-DNA in serum with quantitative polymerase chain reaction （PCR） revealed a high level of viral load. After 2 courses of intravenous immunoglobulin （IVIG） therapy, bone marrow erythropoiesis recovered with his hemoglobin level increased to 123 g/L. He had a lowlevel PVB19 load for a 5-too follow-up period without recurrence of PRCA, and finally the virus was cleared. Our case indicates that clearance of PVB19 by IVIG in transplant recipients might be delayed after recovery of anemia.展开更多
AIM： To establish a rapid and convenient animal model with hepatitis B virus （HBV） replication.METHODS： A naked DNA solution of HBV-replicationcompetent plasmid was transferred to BALB/C mice via the tail vein, us...AIM： To establish a rapid and convenient animal model with hepatitis B virus （HBV） replication.METHODS： A naked DNA solution of HBV-replicationcompetent plasmid was transferred to BALB/C mice via the tail vein, using a hydrodynamic in vivo transfection procedure. After injection, these mice were sacrificed on d 1, 3, 4, 5, 7 and 10. HBV DNA replication intermediates in the liver were analyzed by Southern blot hybridization. The expression of hepatitis B core antigen （HBcAg） and hepatitis B surface antigen （HBsAg） in the liver was checked by immunohistochemistry. Serum HBsAg and hepatitis B e antigen （HBeAg） was detected by enzyme- linked immunosorbent assay （ELISA）. Inhibition of HBV replication was compared in HBV replication model mice treated intraperitoneally with polyinosinic-polytidylin acid （polyIC） or phosphate-buffered saline （PBS）.RESULTS： After hydrodynamic in vivo transfection, HBV DNA replication intermediates in the mouse liver were detectable on d 1 and abundant on d 3 and 4, the levels were slightly decreased and remained relatively stable between d 5 and 7, and were almost undetectable on d 10. The expression patterns of HBcAg and HBsAg were similar to that of HBV replication intermediate DNA, except that they reached a peak on d 1 after injection. No obvious differences in HBV DNA replication intermediates were observed in the left, right and middle lobes of the liver. After treatment with polyIC, the level of HBV intermediate DNA in the liver was lower than that in the control mice injected with PBS.CONCLUSION： A rapid and convenient mouse model with a high level of HBV replication was developed and used to investigate the inhibitory effect of polyIC on HBV replication, which provides a useful tool for future functional studies of the HBV genome.展开更多
AIM: Clinical therapy and prognosis in HCV infections are not good, and mix-infections with different HCV genotypes or quasispecies and mix-infections with HCV plus other hepatitis viruses are important concerns world...AIM: Clinical therapy and prognosis in HCV infections are not good, and mix-infections with different HCV genotypes or quasispecies and mix-infections with HCV plus other hepatitis viruses are important concerns worldwide. The present report describes the sequence diversity and genotying of the 5'NCR of HCV isolates from hepatitis patients mix-infected with different HCV genotypes or variants, and the conditions of mix-infections with HCV plus other hepatitis viruses, providing important diagnostic and prognostic information for more effective treatment of HCV infections.METHODS: The 5' non-coding region (5'NCR) of HCV was isolated from the patients sera and sequenced, and sequence variability and genotypes of HCV were defined by nucleotide sequence alignment and phylogenetic analysis, and the patients mix-infected with HCV plus other hepatitis viruses were analyzed. The conditions and clinical significance of mix-infections with HCV plus other hepatitis viruses were further studied.RESULTS: Twenty-four out of 43 patients with chronic hepatitis C were defined as mix-infected with different genotypes of HCV. Among these 24 patients, 9 were mixinfected with genotype 1 and 3, 7 with different variants of genotype 1, 2 with different variants of genotype 2, 6with different variants of genotype 3. No patients were found mix-infected with genotype 1 and 2 or with genotype 2 and 3. The clinical virological analysis of 60 patients mixinfected with HCV plus other hepatitis viruses showed that 45.0 % of the patients were mix-infected with HCV plus HAV, 61.7 % with HCV plus HBV, 6.7 % with HCV plus HDV/HBV, 8.4 % with HCV plus HEV, 3.3 % with HCV plus HGV. Infections with HCV plus other hepatitis viruses may exacerbate the pathological lesion of the liver.CONCLUSION: The findings in the present study imply that mix-infections with different HCV genotypes and mixinfections with HCV plus other hepatitis viruses were relatively high in Yunnan, China, providing important diagnostic and prognostic information for more effective treatment of HCV infections.展开更多
The Songnen Plain in Northeast China,one of the key national bases of agricultural production,went through remarkable land use/cover changes in recent years.This study aimed to explore the long-term land use/cover cha...The Songnen Plain in Northeast China,one of the key national bases of agricultural production,went through remarkable land use/cover changes in recent years.This study aimed to explore the long-term land use/cover changes and the effects of these changes on the environment.The Landsat-based analysis showed that,during 1986-2000,cropland,built-up land and barren land had increased,among which cropland had the largest increase of 9,198km2 with an increase rate of 7.5%.Woodland,grassland,water body and swampland had decreased correspondingly,among which grassland had the most dramatic decrease of 6,127km2 with a decrease rate of 25.6%.The transition matrix results revealed that grassland,woodland and swampland were the three main land use types converted to cropland.Climate warming created the potential environment for the conversion of grassland and swampland into cropland.Land resources policy made by central and provincial governments of China affected the pattern and intensity of land use.Land use/cover changes accompanied by climatic variation brought out a series of environmental consequences,such as sand desertification of land,land salinization and alkalinization,grassland degradation,and more frequent floods.Under this circumstance,optimized land use structure and restoration measures are needed.展开更多
Objective To study the effect of Simulated Microgravity and its Associated Mechanism on Pulmonary Circulation in Rats. Methods Rat tail-suspension model was used to simulate the physiological effects of microgravity a...Objective To study the effect of Simulated Microgravity and its Associated Mechanism on Pulmonary Circulation in Rats. Methods Rat tail-suspension model was used to simulate the physiological effects of microgravity and changes in pulmonary blood vessel morphology, pulmonary arterial and venous blood pressure, pulmonary vascular resistance, pulmonary vasomotoricity, as well as the regulation of pulmonary circulation by cytokines produced and released by the lung of rats were measured. Results The walls of pulmonary blood vessels of rats were thickened, and the pulmonary artery was reconstructed with increased pulmonary vascular resistance. The pulmonary blood vessels of rats became more prone to dilation as contractions increased. Rat epithelial Adrenomedulin gene transcription and protein expression were upregulated. The level of basic fibroblast growth Factor of rat was also elevated. Conclusion Findings from the present study on rats revealed that the microgravity can affect pulmonary blood vessel structure, pulmonary arterial pressure, and pulmonary blood vessel self-regulation and cytokine production.展开更多
AIM: To evaluate the effect of combined antisense oligonucleotides targeting midkine (MK-AS) and chemotherapeutic drugs [cisplatin(DDP), 5-fluorouracil (5-FU) and adriamycin (ADM)] on inhibition of HepG2 cell prolifer...AIM: To evaluate the effect of combined antisense oligonucleotides targeting midkine (MK-AS) and chemotherapeutic drugs [cisplatin(DDP), 5-fluorouracil (5-FU) and adriamycin (ADM)] on inhibition of HepG2 cell proliferation, and to analyze the efficacy of MK-AS used in combined ADM in in situ human hepatocellular carcinoma (HCC) model. METHODS: HepG2 cells were treated with MK-AS and/or chemotherapeutic drugs mediated by Lipofectin, and cell growth activity was determined by MTS assay. An in situ HCC model was used in this experiment. MK- AS, ADM and MK-AS + ADM were given intravenously for 20 d, respectively. The animal body weight and their tumor weight were measured to assess the effect of the combined therapy in vivo. RESULTS: Combined treatment with MK-AS reduced the IC50 of DDP, 5-FU and ADM in HepG2 cells. MK-AS significantly increased the inhibition rate of DDP, 5-FU and ADM. Additionally, synergism (Q 1.15) occurred at a lower concentration of ADM, 5-FU and DDP with combined MK-AS. Combined treatment with MK-AS and ADM resulted in the more growth inhibition on in situ human HCC model compared with treatment with chemotherapeutic drugs alone. CONCLUSION: MK-AS increases the chemosensitivity in HepG2 cells and in situ human HCC model, and thecombination of MK-AS and ADM has a much better in vitro and in vivo synergism.展开更多
Capillarin was isolated from Artemisia Ordosica Kraschen and characterized by IR, 1H-NMR, 13C-NMR, 1H-1HCOSY, HMQC, HMBC and EIMS, and its crystal structure was determined by single-crystal X-ray diffraction analysis ...Capillarin was isolated from Artemisia Ordosica Kraschen and characterized by IR, 1H-NMR, 13C-NMR, 1H-1HCOSY, HMQC, HMBC and EIMS, and its crystal structure was determined by single-crystal X-ray diffraction analysis with the following data: triclinic, space group P1, Z = 2, a = 7.226(6), b = 7.297(6), c = 11.042(8) ?, α = 74.695(12), β = 78.479(12), γ = 62.063(10)°, V = 494.2(6) ?3, Mr = 198.21, Dc = 1.332 g/cm3, F(000) = 208, μ = 0.089 mm-1, S = 1.023, (?/σ)max = 0.000, the final R = 0.0408 and wR = 0.1110. The largest peak and deepest hole on the final difference Fourier map are 0.219 and –0.161 e/?3, respectively. The bond lengths and bond angles of the molecule are also given.展开更多
AIM:To identify and assess mutations in the K-ras and BRAF genes in a cohort of Chinese patients with colorectal cancer (CRC) for their association with various clinicopathological parameters and prognosis.METHODS:Gen...AIM:To identify and assess mutations in the K-ras and BRAF genes in a cohort of Chinese patients with colorectal cancer (CRC) for their association with various clinicopathological parameters and prognosis.METHODS:Genomic DNA was isolated from frozen tissues.Pyrosequencing analysis was conducted to detect mutations in the K-ras (codons 12,13,and 61) and BRAF genes (codon 600).Statistical analysis was carried out using SPSS-15.0 software.RESULTS:Among the 118 colorectal cancer patients,we detected 41 (34.7%) mutations in the K-ras gene.Mutation frequencies at codon 12 and codon 13 were 23.7% (28/118) and 10.2% (12/118),respectively.Only one patient harbored a point mutation at codon 61 (0.8%,1/118).Gender was the only factor that showed an obvious relationship with K-ras gene mutation (female 44.7% vs male 28.2%,P=0.037).Other clinicopathological features,such as age,location of the tumor,tumor differentiation,Tumor,Node and Metastases classification,and the Union for International Cancer Control staging,showed no positive relationship with K-ras gene mutations.No significant correlation was observed between the presence of K-ras mutations (codons 12,13,and 61) and the survival of the patients.BRAF mutations were rare,and only two patients (1.7%) harbored a detectable mutation at codon 600.CONCLUSION:K-ras gene mutation is a common event in our 118 Chinese CRC patients,with an obvious relationship with gender.However,it seems not to be an independent prognostic factor in CRC patients.The BRAF gene is rarely mutated in Chinese CRC patients.展开更多
The increasing demand for fresh sweet maize （Zea mays L. saccharata） in southern China has prioritized the need to find solutions to the environmental pollution caused by its continuous production and high inputs of...The increasing demand for fresh sweet maize （Zea mays L. saccharata） in southern China has prioritized the need to find solutions to the environmental pollution caused by its continuous production and high inputs of chemical nitrogen fertilizers. A promising method for improving crop production and environmental conditions is to intercrop sweet maize with legumes. Here, a three-year field experiment was conducted to assess the influence of four different cropping systems （sole sweet maize （SS）, sole soybean （SB）, two rows sweet maize-three rows soybean （S2B3） intercropping, and two rows sweet maize-four rows soybean （S2B4） intercropping）, together with two rates of N fertilizer application （300 and 360 kg N ha-1） on grain yield, residual soil mineral N, and soil N2O emissions in southern China. Results showed that in most case, inter- cropping achieved yield advantages （total land equivalent ratio （TLER=0.87-1.25） was above one）. Moreover, intercropping resulted in 39.8% less soil mineral N than SS at the time of crop harvest, averaged over six seasons （spring and autumn in each of the three years of the field experiment）. Generally, intercropping and reduced-N application （300 kg N ha-1） produced lower cumulative soil N20 and yield-scaled soil N20 emissions than SS and conventionaI-N application （360 kg N ha-l）, respectively. $2B4 intercropping with reduced-N rate （300 kg N ha-~） showed the lowest cumulative soil N20 （mean value=0.61 kg ha-1） and yield-scaled soil N20 （mean value=0.04 kg t-1） emissions. Overall, intercropping with reduced-N rate maintained sweet maize production, while also reducing environmental impacts. The system of S2B4 intercropping with reduced-N rate may be the most sustainable and environmentally friendly cropping system.展开更多
Sulfur flow for new generation steel manufacturing process is analyzed by the method of material flow analysis, and measures for SO2 emission reduction are put forward as assessment and target intervention of the resu...Sulfur flow for new generation steel manufacturing process is analyzed by the method of material flow analysis, and measures for SO2 emission reduction are put forward as assessment and target intervention of the results. The results of sulfur flow analysis indicate that 90 % of sulfur comes from fuels. Sulfur finally discharges from the steel manufacturing route in various steps, and the main point is BF and BOF slag desulfurization. In sintering process, the sulfur is removed by gasification, and sintering process is the main source of SO2 emission. The sulfur content of coke oven gas （COG） is an important factor affecting SO2 emission. Therefore, SO2 emission reduction should be started from the optimization and integration of steel manufacturing route, sulfur burden should be reduced through energy saving and consumption reduction, and the sulfur content of fuel should be controlled. At the same time, BF and BOF slag desulfurization should be optimized further and coke oven gas and sintering exhausted gas desulfurization should be adopted for SO2 emission reduction and reuse of resource, to achieve harmonic coordination of economic, social, and environmental effects for sustainable development.展开更多
Azoospermia is of great importance to male infertility. Obstructive azoospermia （OA） due to infection is the most prevalent form of OA in China and has been less studied. We aim to observe the treatment outcome of m...Azoospermia is of great importance to male infertility. Obstructive azoospermia （OA） due to infection is the most prevalent form of OA in China and has been less studied. We aim to observe the treatment outcome of microsurgical vasoepididymostomy （VE） and also to identify the factors relative to the result after reconstructive surgery. Two hundred and eight men presenting with OA due to infection during the study period from July 2010 to July 2013 were prospectively evaluated. Clinical examination, semen analysis, serum follicle stimulating hormone （FSH）, and scrotal ultrasound were done before surgical exploration. Among the 198 men who were selected for surgical procedures, 159 candidates underwent microsurgical VE with sperm detected in the epididymal fluid. As for the other 39 cases, reconstruction was not feasible. The average age was 28.5 ＋ 3.9 years （range 22-38）, with average follow-up being 16.5 ~ 5.9 months （range 4-28）. According to the 150 cases being followed after VE procedures, the total patency rate was 72% （108/150）. During follow-up, 38.7% （58/150） natural pregnancies occurred, with overall live birth rate being 32.7% （49/150）. Our data suggested that microsurgical VE is an effective therapy for postinfectious epididymal OA. Individualized counseling with prognosis based on etiology should be offered to patients to select optical therapy.展开更多
Paint baking treatment was carried out in a silicon oil bath at 170℃ for 20 min for Si-Al-Mn TRIP Steel sheet with different prestrains, and effect of prestrain on microstructures and properties was studied before an...Paint baking treatment was carried out in a silicon oil bath at 170℃ for 20 min for Si-Al-Mn TRIP Steel sheet with different prestrains, and effect of prestrain on microstructures and properties was studied before and after baking. The results show that with the increasing of prestrain amount during prestraining and baking, the volume fraction of retained austenite decreases, and the volume fraction of martensite and bainite increases as well as yield strength increases; as prestrain ranges from 0 to 4%, the baking-hardening （BH） value increases; while the prestrain ranges from 4% to 16%, the BH value decreases; when the prestrain amount is 4%, the highest BH value is about 70 MPa for Si-Al-Mn TRIP steel sheet with niobium, which displays excellent baking-hardening behavior.展开更多
This paper presents the microwave dielectric properties of reaction bonded porous silicon nitride ceramics with variant porosity and pore size, which were prepared by adding pore-forming agent grains into the silicon ...This paper presents the microwave dielectric properties of reaction bonded porous silicon nitride ceramics with variant porosity and pore size, which were prepared by adding pore-forming agent grains into the silicon powders. The experimental results show that the dielectric constant and the dielectric loss of the samples reduce evidently with increasing porosity in the sample. When the porosity is constant, the dielectric constant and the dielectric loss of the ceramics decrease visibly as the pore size increases. Among all the obtained samples, the minimum dielectric constant is about 2.4.展开更多
The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Re...The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Reservoir.This study aims to characterize the spatial distribution,inter-annual variation of runoff and sediment load in the Jinsha River Basin,and to analyze the contribution of rainfall and human activities to the runoff and sediment load changes.The monitoring data on runoff,sediment load and precipitation were collected from 11hydrological stations in the Jinsha River Basin from1966 to 2016.The data observed at the outlet of the basin showed that 71.4%of the runoff is from the upper reaches of the Jinsha River Basin and the Yalong River,while 63.3%of the sediment is from the lower reaches(excluding the Yalong River).There is no significant increase in runoff on temporal scale in the Jinsha River Basin,while it has an abrupt change in runoff in both upstream and midstream in 1985,and an abrupt change in downstream in 1980 and2013.The sediment load demonstrated a significantincreasing trend in the upstream,no significant reducing trend in the midstream,but significant reducing trend in the downstream.The sediment load in upstream showed abrupt change in 1987,in midstream in 1978 and 2014,in downstream in 2012.Rainfall dominated runoff variation,contributing more than 59.0%of the total variation,while human activity,including reservoirs construction,the implementation of soil and water conservation projects,is the major factor to sediment load variation,contributing more than 87.0%of the total variation.展开更多
The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic ...The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.展开更多
To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were ad...To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were adopted in the meshing stage.The racing rotating speed of the brake wheels was calculated by computational fluid dynamics（CFD） calculation and interpolation,and then accurate boundary condition was applied to the CFD simulation to study the pressure and velocity distribution of internal flow field in hydrodynamic tractor-retarder assembly.Finally,the original characteristics were calculated by CFD post-processing analysis.Comparison of experimental data and flow field analysis results showed that the calculation tolerance of the torque ratio K and the efficiency η was less than 5%,and the calculation tolerance of the pump torque coefficient λ was less than 10%.展开更多
文摘Low collateral damage weapons achieve controlled personnel injury through the coupling of shock waves and particle swarms,where the particle swarms arise from the high-explosive dispersion of compacted metal particle ring.To investigate the dynamic response of the human target under combined shock waves and particle swarms loading,a physical human surrogate torso model(HSTM)was developed,and the dynamic response test experiment was conducted under the combined loading.The effects of particle size on the loading parameters,the damage patterns of the ballistic plate and HSTM,and the dynamic response parameters of the HSTM with and without protection are mainly analyzed.Our findings revealed that particle swarms can effectively delay the shock wave attenuation,especially the best effect when the particle size was 0.28–0.45 mm.The ballistic plate mainly exhibited dense perforation of the outer fabric and impacted crater damage of ceramic plates,whereas the unprotected HSTM was mainly dominated by high-density and small-size ballistic cavity group damage.The peak values of the dynamic response parameters for the HSTM under combined loading were significantly larger than those under bare charge loading,with multiple peaks observed.Under unprotected conditions,the peak acceleration of skeletons and peak pressure of organs increased with the particle size.Under protected conditions,the particle size,the number of particles hit,and the fit of the ballistic plate to the HSTM together affected the dynamic response parameters of the HSTM.
基金supported by the National Natural Science Foundation of China(52202266 and 52403379).
文摘Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale application.However,their practical implementation is hindered by the rapid voltage/capacity decay during cycling and the long-standing problem of redox kinetics due to their poor ionic conductivity based on the ordered honeycomb structure.In this study,the kinetic and thermodynamic properties of intralayer disordered and ordered Li-rich full-Mn-based cathode materials were compared,demonstrating that the disordered R3m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(D-LMO)delivers a significant advantage of rate capability over the ordered C2/m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(O-LMO).Meanwhile,the D-LMO keeps superior capacity retention of up to 99%after 50 cycles under 25 mAg^(-1).In comparsion,the capacity retention of the O-LMO drops to just 70%,and its average discharge voltage is 0.2 V lower than that of the D-LMO.Herein,we conducted systematic density functional theory(DFT)simulations,focusing on the electronic structure modulation governing the voltage platform between the ordered and disordered phases.The ab initio molecular dynamics(AIMD)results indicated that the energy of the intralayer disordered structure fluctuates around the equilibrium position without any abrupt drops,demonstrating excellent stability.This study enhances the understanding of intralayer disordered full-Mn Li-rich material and provides insights into the design of low-cost,high-performance cathode materials for Li-ion batteries.
基金Supported by the National Natural Science Foundation of China,No.300330540
文摘AIM:To investigate the expression of co-stimulatorymolecule B7-H3 in gastric carcinoma and adenomatissue as well as normal gastric tissue and to explore therelationship between B7-H3 expression and pathologicalfeatures and prognosis of gastric carcinoma.METHODS:B7-H3 expression was detected in 102samples of human gastric carcinoma and 10 samples ofgastric adenoma and 10 samples of normal gastric tissueby immunohistochemical assay.Correlation betweenthe expression of B7-H3 and the patients'age,sex,gastric carcinoma locus,tumor size,tissue type,tumorinfiltration depth,differentiation degree,lymph nodemetastasis,and survival time was analyzed.RESULTS:B7-H3 was expressed in all gastric adenomasamples and in 58.8% samples of gastric carcinoma.B7-H3 expression in gastric carcinoma samples wasnot related with the patients'age,sex,lymph nodemetastasis,and tumor size(P>0.05),but with thesurvival time,infiltration depth of tumor and tissue type.CONCLUSION:Detection of B7-H3 expression in gastriccarcinoma tissue is beneficial to the judgment of theprognosis of gastric carcinoma patients and the choice oftreatment.
文摘Pure red cell aplasia （PRCA） due to parvovirus B19 （PVB19） infectiori after solid organ transplantation has been rarely reported and most of the cases were renal transplant recipients, Few have been described after liver transplantation. Moreover, little information on the management of this easily recurring disease is available at present. We describe the first case of a Chinese liver transplant recipient with PVB19-induced PRCA during immunosuppressive therapy. The patient suffered from progressive anemia with the lowest hemoglobin level of 21 g/L. Bone marrow biopsy showed selectively inhibited erythropoiesis with giant pronormoblasts. Detection of PVB19-DNA in serum with quantitative polymerase chain reaction （PCR） revealed a high level of viral load. After 2 courses of intravenous immunoglobulin （IVIG） therapy, bone marrow erythropoiesis recovered with his hemoglobin level increased to 123 g/L. He had a lowlevel PVB19 load for a 5-too follow-up period without recurrence of PRCA, and finally the virus was cleared. Our case indicates that clearance of PVB19 by IVIG in transplant recipients might be delayed after recovery of anemia.
基金Supported by the National Science Fund for Distinguished Young Scholars from the National Natural Science Foundation of China,No.30325036a grant from the National Natural Science Foundation of China,No.30571640
文摘AIM： To establish a rapid and convenient animal model with hepatitis B virus （HBV） replication.METHODS： A naked DNA solution of HBV-replicationcompetent plasmid was transferred to BALB/C mice via the tail vein, using a hydrodynamic in vivo transfection procedure. After injection, these mice were sacrificed on d 1, 3, 4, 5, 7 and 10. HBV DNA replication intermediates in the liver were analyzed by Southern blot hybridization. The expression of hepatitis B core antigen （HBcAg） and hepatitis B surface antigen （HBsAg） in the liver was checked by immunohistochemistry. Serum HBsAg and hepatitis B e antigen （HBeAg） was detected by enzyme- linked immunosorbent assay （ELISA）. Inhibition of HBV replication was compared in HBV replication model mice treated intraperitoneally with polyinosinic-polytidylin acid （polyIC） or phosphate-buffered saline （PBS）.RESULTS： After hydrodynamic in vivo transfection, HBV DNA replication intermediates in the mouse liver were detectable on d 1 and abundant on d 3 and 4, the levels were slightly decreased and remained relatively stable between d 5 and 7, and were almost undetectable on d 10. The expression patterns of HBcAg and HBsAg were similar to that of HBV replication intermediate DNA, except that they reached a peak on d 1 after injection. No obvious differences in HBV DNA replication intermediates were observed in the left, right and middle lobes of the liver. After treatment with polyIC, the level of HBV intermediate DNA in the liver was lower than that in the control mice injected with PBS.CONCLUSION： A rapid and convenient mouse model with a high level of HBV replication was developed and used to investigate the inhibitory effect of polyIC on HBV replication, which provides a useful tool for future functional studies of the HBV genome.
基金the research grants from International Centre for Genetic Engineering and Biotechnology(ICGEB)Collaborative Research Program,CRP/CHN96-05from China Yunnan Provincial Science & Technology Commission International Collaborative Research Program,No.97C009
文摘AIM: Clinical therapy and prognosis in HCV infections are not good, and mix-infections with different HCV genotypes or quasispecies and mix-infections with HCV plus other hepatitis viruses are important concerns worldwide. The present report describes the sequence diversity and genotying of the 5'NCR of HCV isolates from hepatitis patients mix-infected with different HCV genotypes or variants, and the conditions of mix-infections with HCV plus other hepatitis viruses, providing important diagnostic and prognostic information for more effective treatment of HCV infections.METHODS: The 5' non-coding region (5'NCR) of HCV was isolated from the patients sera and sequenced, and sequence variability and genotypes of HCV were defined by nucleotide sequence alignment and phylogenetic analysis, and the patients mix-infected with HCV plus other hepatitis viruses were analyzed. The conditions and clinical significance of mix-infections with HCV plus other hepatitis viruses were further studied.RESULTS: Twenty-four out of 43 patients with chronic hepatitis C were defined as mix-infected with different genotypes of HCV. Among these 24 patients, 9 were mixinfected with genotype 1 and 3, 7 with different variants of genotype 1, 2 with different variants of genotype 2, 6with different variants of genotype 3. No patients were found mix-infected with genotype 1 and 2 or with genotype 2 and 3. The clinical virological analysis of 60 patients mixinfected with HCV plus other hepatitis viruses showed that 45.0 % of the patients were mix-infected with HCV plus HAV, 61.7 % with HCV plus HBV, 6.7 % with HCV plus HDV/HBV, 8.4 % with HCV plus HEV, 3.3 % with HCV plus HGV. Infections with HCV plus other hepatitis viruses may exacerbate the pathological lesion of the liver.CONCLUSION: The findings in the present study imply that mix-infections with different HCV genotypes and mixinfections with HCV plus other hepatitis viruses were relatively high in Yunnan, China, providing important diagnostic and prognostic information for more effective treatment of HCV infections.
基金Under the auspices of Knowledge Innovation Programs of Chinese Academy of Sciences (No KZCX2-YW-341)National Natural Science Foundation of China (No 40871187)
文摘The Songnen Plain in Northeast China,one of the key national bases of agricultural production,went through remarkable land use/cover changes in recent years.This study aimed to explore the long-term land use/cover changes and the effects of these changes on the environment.The Landsat-based analysis showed that,during 1986-2000,cropland,built-up land and barren land had increased,among which cropland had the largest increase of 9,198km2 with an increase rate of 7.5%.Woodland,grassland,water body and swampland had decreased correspondingly,among which grassland had the most dramatic decrease of 6,127km2 with a decrease rate of 25.6%.The transition matrix results revealed that grassland,woodland and swampland were the three main land use types converted to cropland.Climate warming created the potential environment for the conversion of grassland and swampland into cropland.Land resources policy made by central and provincial governments of China affected the pattern and intensity of land use.Land use/cover changes accompanied by climatic variation brought out a series of environmental consequences,such as sand desertification of land,land salinization and alkalinization,grassland degradation,and more frequent floods.Under this circumstance,optimized land use structure and restoration measures are needed.
基金supported by the Defense Medical Fund of China, 06Z048China Advanced Space Medico-engineering Research Project, 2011SY5406018 and SJ200801+2 种基金The State Key Laboratory of Space Medicine FundamentalsApplication of China Astronaut Research and Training CenterSMFA09A02, SMFA11A01 and SMFA12K04
文摘Objective To study the effect of Simulated Microgravity and its Associated Mechanism on Pulmonary Circulation in Rats. Methods Rat tail-suspension model was used to simulate the physiological effects of microgravity and changes in pulmonary blood vessel morphology, pulmonary arterial and venous blood pressure, pulmonary vascular resistance, pulmonary vasomotoricity, as well as the regulation of pulmonary circulation by cytokines produced and released by the lung of rats were measured. Results The walls of pulmonary blood vessels of rats were thickened, and the pulmonary artery was reconstructed with increased pulmonary vascular resistance. The pulmonary blood vessels of rats became more prone to dilation as contractions increased. Rat epithelial Adrenomedulin gene transcription and protein expression were upregulated. The level of basic fibroblast growth Factor of rat was also elevated. Conclusion Findings from the present study on rats revealed that the microgravity can affect pulmonary blood vessel structure, pulmonary arterial pressure, and pulmonary blood vessel self-regulation and cytokine production.
基金Supported by grants from the Zhejiang Province Medicine and Health Research Fund, No. 2003A077Huzhou Natural Science Foundation, No. 2004SZX07-11, China
文摘AIM: To evaluate the effect of combined antisense oligonucleotides targeting midkine (MK-AS) and chemotherapeutic drugs [cisplatin(DDP), 5-fluorouracil (5-FU) and adriamycin (ADM)] on inhibition of HepG2 cell proliferation, and to analyze the efficacy of MK-AS used in combined ADM in in situ human hepatocellular carcinoma (HCC) model. METHODS: HepG2 cells were treated with MK-AS and/or chemotherapeutic drugs mediated by Lipofectin, and cell growth activity was determined by MTS assay. An in situ HCC model was used in this experiment. MK- AS, ADM and MK-AS + ADM were given intravenously for 20 d, respectively. The animal body weight and their tumor weight were measured to assess the effect of the combined therapy in vivo. RESULTS: Combined treatment with MK-AS reduced the IC50 of DDP, 5-FU and ADM in HepG2 cells. MK-AS significantly increased the inhibition rate of DDP, 5-FU and ADM. Additionally, synergism (Q 1.15) occurred at a lower concentration of ADM, 5-FU and DDP with combined MK-AS. Combined treatment with MK-AS and ADM resulted in the more growth inhibition on in situ human HCC model compared with treatment with chemotherapeutic drugs alone. CONCLUSION: MK-AS increases the chemosensitivity in HepG2 cells and in situ human HCC model, and thecombination of MK-AS and ADM has a much better in vitro and in vivo synergism.
基金The project was supported by Henan Innovation Project for University Prominent Research Talents (2004)
文摘Capillarin was isolated from Artemisia Ordosica Kraschen and characterized by IR, 1H-NMR, 13C-NMR, 1H-1HCOSY, HMQC, HMBC and EIMS, and its crystal structure was determined by single-crystal X-ray diffraction analysis with the following data: triclinic, space group P1, Z = 2, a = 7.226(6), b = 7.297(6), c = 11.042(8) ?, α = 74.695(12), β = 78.479(12), γ = 62.063(10)°, V = 494.2(6) ?3, Mr = 198.21, Dc = 1.332 g/cm3, F(000) = 208, μ = 0.089 mm-1, S = 1.023, (?/σ)max = 0.000, the final R = 0.0408 and wR = 0.1110. The largest peak and deepest hole on the final difference Fourier map are 0.219 and –0.161 e/?3, respectively. The bond lengths and bond angles of the molecule are also given.
基金Supported by National Natural Science Foundation of China（61105089） State Key Laboratory of Robotics and System（SKLRS-2013-ZD-03） Open Foundation of the State Key Laboratory of Fluid Power Transmission and Control（GZKF-201212）
基金Supported by The Department of Education of Zhejiang Province of China,grant No.Y200804314the Zhejiang Provincial Natural Science Foundation,grant No.R2090353+1 种基金the Department of Science and Technology of Zhejiang Province,grant No.2008C33039the Chinese Ministry of Health,grant No.N20100148
文摘AIM:To identify and assess mutations in the K-ras and BRAF genes in a cohort of Chinese patients with colorectal cancer (CRC) for their association with various clinicopathological parameters and prognosis.METHODS:Genomic DNA was isolated from frozen tissues.Pyrosequencing analysis was conducted to detect mutations in the K-ras (codons 12,13,and 61) and BRAF genes (codon 600).Statistical analysis was carried out using SPSS-15.0 software.RESULTS:Among the 118 colorectal cancer patients,we detected 41 (34.7%) mutations in the K-ras gene.Mutation frequencies at codon 12 and codon 13 were 23.7% (28/118) and 10.2% (12/118),respectively.Only one patient harbored a point mutation at codon 61 (0.8%,1/118).Gender was the only factor that showed an obvious relationship with K-ras gene mutation (female 44.7% vs male 28.2%,P=0.037).Other clinicopathological features,such as age,location of the tumor,tumor differentiation,Tumor,Node and Metastases classification,and the Union for International Cancer Control staging,showed no positive relationship with K-ras gene mutations.No significant correlation was observed between the presence of K-ras mutations (codons 12,13,and 61) and the survival of the patients.BRAF mutations were rare,and only two patients (1.7%) harbored a detectable mutation at codon 600.CONCLUSION:K-ras gene mutation is a common event in our 118 Chinese CRC patients,with an obvious relationship with gender.However,it seems not to be an independent prognostic factor in CRC patients.The BRAF gene is rarely mutated in Chinese CRC patients.
基金supported by the Key Technologies R&D Program of China during the 12th Five-year Plan period(2012BAD14B16-04)the Science and Technology Development Program of Guangdong,China(2012A020100003 and 2015B090903077)
文摘The increasing demand for fresh sweet maize （Zea mays L. saccharata） in southern China has prioritized the need to find solutions to the environmental pollution caused by its continuous production and high inputs of chemical nitrogen fertilizers. A promising method for improving crop production and environmental conditions is to intercrop sweet maize with legumes. Here, a three-year field experiment was conducted to assess the influence of four different cropping systems （sole sweet maize （SS）, sole soybean （SB）, two rows sweet maize-three rows soybean （S2B3） intercropping, and two rows sweet maize-four rows soybean （S2B4） intercropping）, together with two rates of N fertilizer application （300 and 360 kg N ha-1） on grain yield, residual soil mineral N, and soil N2O emissions in southern China. Results showed that in most case, inter- cropping achieved yield advantages （total land equivalent ratio （TLER=0.87-1.25） was above one）. Moreover, intercropping resulted in 39.8% less soil mineral N than SS at the time of crop harvest, averaged over six seasons （spring and autumn in each of the three years of the field experiment）. Generally, intercropping and reduced-N application （300 kg N ha-1） produced lower cumulative soil N20 and yield-scaled soil N20 emissions than SS and conventionaI-N application （360 kg N ha-l）, respectively. $2B4 intercropping with reduced-N rate （300 kg N ha-~） showed the lowest cumulative soil N20 （mean value=0.61 kg ha-1） and yield-scaled soil N20 （mean value=0.04 kg t-1） emissions. Overall, intercropping with reduced-N rate maintained sweet maize production, while also reducing environmental impacts. The system of S2B4 intercropping with reduced-N rate may be the most sustainable and environmentally friendly cropping system.
基金Item Sponsored by National Natural Science Foundation of China(50334020)
文摘Sulfur flow for new generation steel manufacturing process is analyzed by the method of material flow analysis, and measures for SO2 emission reduction are put forward as assessment and target intervention of the results. The results of sulfur flow analysis indicate that 90 % of sulfur comes from fuels. Sulfur finally discharges from the steel manufacturing route in various steps, and the main point is BF and BOF slag desulfurization. In sintering process, the sulfur is removed by gasification, and sintering process is the main source of SO2 emission. The sulfur content of coke oven gas （COG） is an important factor affecting SO2 emission. Therefore, SO2 emission reduction should be started from the optimization and integration of steel manufacturing route, sulfur burden should be reduced through energy saving and consumption reduction, and the sulfur content of fuel should be controlled. At the same time, BF and BOF slag desulfurization should be optimized further and coke oven gas and sintering exhausted gas desulfurization should be adopted for SO2 emission reduction and reuse of resource, to achieve harmonic coordination of economic, social, and environmental effects for sustainable development.
文摘Azoospermia is of great importance to male infertility. Obstructive azoospermia （OA） due to infection is the most prevalent form of OA in China and has been less studied. We aim to observe the treatment outcome of microsurgical vasoepididymostomy （VE） and also to identify the factors relative to the result after reconstructive surgery. Two hundred and eight men presenting with OA due to infection during the study period from July 2010 to July 2013 were prospectively evaluated. Clinical examination, semen analysis, serum follicle stimulating hormone （FSH）, and scrotal ultrasound were done before surgical exploration. Among the 198 men who were selected for surgical procedures, 159 candidates underwent microsurgical VE with sperm detected in the epididymal fluid. As for the other 39 cases, reconstruction was not feasible. The average age was 28.5 ＋ 3.9 years （range 22-38）, with average follow-up being 16.5 ~ 5.9 months （range 4-28）. According to the 150 cases being followed after VE procedures, the total patency rate was 72% （108/150）. During follow-up, 38.7% （58/150） natural pregnancies occurred, with overall live birth rate being 32.7% （49/150）. Our data suggested that microsurgical VE is an effective therapy for postinfectious epididymal OA. Individualized counseling with prognosis based on etiology should be offered to patients to select optical therapy.
基金Item Sponsored by National Natural Science Foundation of China(50527402)
文摘Paint baking treatment was carried out in a silicon oil bath at 170℃ for 20 min for Si-Al-Mn TRIP Steel sheet with different prestrains, and effect of prestrain on microstructures and properties was studied before and after baking. The results show that with the increasing of prestrain amount during prestraining and baking, the volume fraction of retained austenite decreases, and the volume fraction of martensite and bainite increases as well as yield strength increases; as prestrain ranges from 0 to 4%, the baking-hardening （BH） value increases; while the prestrain ranges from 4% to 16%, the BH value decreases; when the prestrain amount is 4%, the highest BH value is about 70 MPa for Si-Al-Mn TRIP steel sheet with niobium, which displays excellent baking-hardening behavior.
基金supported by the National Natural Science Foundation of China under grant No.90305016.
文摘This paper presents the microwave dielectric properties of reaction bonded porous silicon nitride ceramics with variant porosity and pore size, which were prepared by adding pore-forming agent grains into the silicon powders. The experimental results show that the dielectric constant and the dielectric loss of the samples reduce evidently with increasing porosity in the sample. When the porosity is constant, the dielectric constant and the dielectric loss of the ceramics decrease visibly as the pore size increases. Among all the obtained samples, the minimum dielectric constant is about 2.4.
基金supported by the “National Key R & D Plan Project of China (2018YFD0200502)the 135 Strategic Program of the Institute of Mountain Hazards and Environment, CAS (SDS135-1702)
文摘The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Reservoir.This study aims to characterize the spatial distribution,inter-annual variation of runoff and sediment load in the Jinsha River Basin,and to analyze the contribution of rainfall and human activities to the runoff and sediment load changes.The monitoring data on runoff,sediment load and precipitation were collected from 11hydrological stations in the Jinsha River Basin from1966 to 2016.The data observed at the outlet of the basin showed that 71.4%of the runoff is from the upper reaches of the Jinsha River Basin and the Yalong River,while 63.3%of the sediment is from the lower reaches(excluding the Yalong River).There is no significant increase in runoff on temporal scale in the Jinsha River Basin,while it has an abrupt change in runoff in both upstream and midstream in 1985,and an abrupt change in downstream in 1980 and2013.The sediment load demonstrated a significantincreasing trend in the upstream,no significant reducing trend in the midstream,but significant reducing trend in the downstream.The sediment load in upstream showed abrupt change in 1987,in midstream in 1978 and 2014,in downstream in 2012.Rainfall dominated runoff variation,contributing more than 59.0%of the total variation,while human activity,including reservoirs construction,the implementation of soil and water conservation projects,is the major factor to sediment load variation,contributing more than 87.0%of the total variation.
基金supported by the National Key Research and Development Program of China (2016YFC0500503)the Science and Technology Program of Inner Mongolia Autonomous Region of China (20140409, 201503001)
文摘The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.
基金Supported by the National Key Laboratory of Vehicular Transmission (9140C3405020905)the National Natural Science Foundation of China(50905016)
文摘To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were adopted in the meshing stage.The racing rotating speed of the brake wheels was calculated by computational fluid dynamics（CFD） calculation and interpolation,and then accurate boundary condition was applied to the CFD simulation to study the pressure and velocity distribution of internal flow field in hydrodynamic tractor-retarder assembly.Finally,the original characteristics were calculated by CFD post-processing analysis.Comparison of experimental data and flow field analysis results showed that the calculation tolerance of the torque ratio K and the efficiency η was less than 5%,and the calculation tolerance of the pump torque coefficient λ was less than 10%.
