最新刊期
卷 55 ， 期 1 ， 2016
- 摘要：In recent years, a disease outbreak occurred in >50 percent of Litopenaeus vannamei farms at about 30 days after frys are released into the ponds in southern China. About 80% culture shrimps were dead in culture period. The clinical symptoms of the diseased shrimps include atrophy and necrosis of the hepatopancreas, weakened activity, and shrimp found dead in the bottom of the pond. The farmers in China usually called this symptom as “hidden death disease”. Since hepatopancreas atrophy and necrosis are the main symptoms of the disease, so we called this disease as hepatopancreas necrosis syndrome (HPNS). In March 2012 to October 2013, we have collected the diseased L. vannamei with the symptoms of HPNS in 12 farms from Guangdong, Hainan and Guangxi provinces, China. Histopathology showed necrosis of hepatopancreas of the diseased shrimps, disappearance of some hepatopancreatic epidermal cells, and connective tissue. We used PCR to detect the presence of 11 viruses in 305 HPNS shrimps and performed artificial viral infection to healthy shrimps. The artificially infected shrimps did not show symptoms of HPNS. A total of 383 bacteria strains were identified from hepatopancreas, hemolymph and intestine of 63 diseased shrimps. These bacteria belong to 10 genera, 49 species. We isolated Vibrio parahaemolyticus from 38 shrimps, Bacillus cereus from 34 shrimps, B. thuringiensis from 20 shrimps and V. cholera from 19 shrimps. Injection and immersion of V. parahaemolyticus and B. thuringiensis can cause symptoms of HPNS. The results suggest that multiple bacteria were involved in HPNS of L. vannamei.关键词：Litopenaeus vannamei;hepatopancreas necrosis syndrome (HPNS);bacterium;virus
- 867
- |
- 3789
- |
- 9
发布时间：2023-12-11 - 摘要：The purpose of this study was to investigate the therapeutic effects of total flavonoids of Hypericum japonicum against liver fibrosis induced by bile duct ligation in rats. Liver fibrosis model was established by bile duct ligation. After bile duct ligation, the treatment groups orally received total flavonoids of Hypericum japonicum(9,18,36 mg·kg-1·d-1) daily for 4 weeks. Then, rats were all executed. Serum and liver tissues were obtained. Serum levels of TBIL, DBIL, ALT, AST, HA, LN, PCⅢ, TNF-α and the activities of SOD, GSH-Px and the contents of MDA, Hyp, MMP-1 and TIMP-1 in liver tissues were detected. Results showed that total flavonoids of Hypericum japonicum could significantly alleviate liver fibrosis, as indicated by decreasing levels of TBIL, DBIL, ALT, AST, HA, LN, PCⅢ, TNF-α, Hyp and TIMP-1. Moreover, total flavonoids of Hypericum japonicum could effectively enhance the activities of SOD, GSH-Px and decrease the content of MDA. Our results show that total flavonoids of Hypericum japonicum is effective in attenuating liver fibrosis induced by bile duct ligation in rats, at least partly, via enhancing the activation of antioxidant enzymes and inhibiting release of TNF-α.关键词：total flavonoids of Hypericum japonicum;liver fibrosis;bile duct ligation
- 338
- |
- 483
- |
- 2
发布时间：2023-12-11 - 摘要：Genetic diversity of Scaevola hainanensis Hance is estimated based on the sequences of nuclear ribosomal internal transcribed spacer region (ITS) from five populations distributed in China. Further, phylogenetic analysis of the S. hainanensis is performed based on combined ITS sequences data with other species of Scaevola and outgroups available from GenBank. The results shows that the genetic diversity of S. hainanensis is very low, implying that it is at risk of extinction at the genetic level as a rare plant. In the phylogenetic tree , S. hainanensis is located in the Northern Hemisphere lineage and closest to the clade consisting of local species in Hawaii with high support value, which imply the progenitor-derivative dispersal pattern of Scaevola species between Asia and Hawaii. The results did not support the monophyly of S. sect Scaevola and the hypothesis that S. hainanensis is derived from a widespread and sympatric species S. taccada is rejected based on the present result.
- 312
- |
- 578
- |
- 2
发布时间：2023-12-11 - 摘要：Pinus elliottii is commonly considered to be one of the most important pioneer tree species for forest restoration and reconstruction in subtropical degraded red soil area of China, due to its high productivity and leannessresistance. However, they also consume certain amount of water during the course of growing and maintaining ecological balance. Therefore, quantitative research on tree water consumption by transpiration has become a hotspot in the field of tree physiological ecology in recent years. In order to provide an effective way for conducting sustainable management of Pinus elliottii plantation and associated water resource of similar condition, in this study, we chose the Pinus elliottii plantation in degraded red soil area of Jiangxi province as the research object, and the log-sigmoid type function (i.e. tansig) of MATLAB software was selected as the action function of neurons. Based on the correlation analysis between sap flow velocity and meteorological factors, air temperature, relative air humidity, average net radiation and vapor pressure deficit were chosen as the input variables and sap flow velocity as the output variable. Then the optimum 3-layer BP artificial network model of individual sap flow velocity was established with the topological structure of 4-10-1. Nineteen hundreds groups of individual tree data were used to train the very neutral network both with Bayesian regularization algorithm and Levenberg-Marquardt algorithm, while the remaining nineteen hundreds groups were used to test the model. Good fitting results were obtained for linear regression between predictive and measured values under two algorithm model, with the R higher as 0.98. The results showed that fitting accuracy of training samples was 88.12% and 88.11%, respectively, and the simulating accuracy of testing samples was 88.11% and 87.98%, respectively. This model can well reflect the non-linear relationship between sap flow velocity and meteorological factors owing to its higher accuracy and fine generalization than linear regression model, which indicated the availability of BP neutral network for the analysis, simulation and prediction of sap flow velocity.关键词：Pinus elliottii;sap flow;BP neural network;Bayesian regularization algorithm;Levenberg-Marquardt algorithm
- 272
- |
- 493
- |
- 1
发布时间：2023-12-11 - 摘要：With the general spectral decomposition techniques and by means of the linear operator semigroups theory, the existence and uniqueness of uniformly continuous mild solutions to the functional differential equations of neutral type in Banach space X are studied. The spectrum conditions which imply the existence and uniqueness of almost periodic mild solutions to the equations are obtained when X has no subspace isomorphic to c0. The results extend recent results of the linear differential equations.关键词：almost periodicity;Carleman spectrum;linear operator semigroups;functional differential equations of neutral type
- 265
- |
- 445
- |
- 0
发布时间：2023-12-11 - 摘要：A computer virus model with density-dependent and limited anti-virus ability is studied. The existence of equilibria is given and the local stability is established under the threshold value condition. After some mathematical analyses, it is showed that the forward and backward bifurcations occur and alsos proved that there is no limit cycle for system. Finally, the results are confirmed by numerical simulation.关键词：anti-virus ability;stability;forward bifurcation;backward bifurcation
- 302
- |
- 458
- |
- 0
发布时间：2023-12-11 - 摘要：Let Γ(M) be the commuting graph of 2×2 matrix ring over a finite field. The compressed graph of Γ(M) is constructed and the relationship of the automorphism groups of these two graphs is studied, then all the automorphisms of Γ(M) are determined.关键词：matrix rings;noncommutative rings;commuting graphs;automorphisms
- 365
- |
- 445
- |
- 0
发布时间：2023-12-11 - 摘要：Let D be the open unit disk in the complex plane C , H(D) the class of all holomorphic functions on D. The products of integral-type operator Igand composition operator CΦare defined by CΦIgf(z)=∫Φ(z)0f ′(ξ)g(ξ)dξ，IgCΦf(z) = ∫z0f ′((ξ))g(ξ)dξ, where φ be an analytic self-map of D and g∈H(D). By using analysis methods and constructing test functions, the sufficient and necessary conditions of the continuity, boundedness from below and compactness of the products of CΦIgand IgCΦon Bloch-Orlicz type spaces are obtained.关键词：Bloch type space;Orlicz space;composition operator;integral type operator
- 277
- |
- 450
- |
- 1
发布时间：2023-12-11 - 摘要：Totally edge-growing network models are defined. Two algorithms for finding Maximum Leaf Spanning trees (MLS-trees)of the totally edge-growing models is shown. The small world property of MLS-trees is analysised, and the scale-free with MLS-trees is verified. An application of MLS-trees to determine balanced sets and smallest dominating sets of totally edge-growing network models is given.关键词：scale-free network;spanning tree;network models
- 300
- |
- 428
- |
- 3
发布时间：2023-12-11 - 摘要：Based on the secondary development in Fluent, the study built a 2D numerical wave tank by the method of momentum source. Firstly, the established wave tank was used to simulate the resonance phenomenon between the waves and multi-floating bodies, and the numerical results were in good agreement with the experimental data. The results showed that the horizontal force acting on the last body was the largest. Subsequently, the influences of draft on resonance phenomenon were analyzed, indicating that the horizontal force acting on each body was, on the whole, correlated with its draft while the relation between vertical force and draft varied with the body. In the end, the influence of the addition of third body on resonance phenomenon in the gap was discussed, showing that resonance frequency would move to lower and the second resonance frequency would probably appear when the third body was added into the floating system.关键词：resonance;floating bodies;wave generation;draft
- 314
- |
- 444
- |
- 2
发布时间：2023-12-11 - 摘要：A novel approach of constructing time-invariant LDPC convolutional codes is proposed. The matrix of an LDPC (Low-Density Parity-Check) convolutional code with a given rate is generated according to the original matrix generated by Tanner etc. Then, the matrix with maximum given encoding memory and fast encoding property is obtained by modifying the above-mentioned matrix. The fast encoding property of the proposed matrix can reduce the encoding complexity. And the maximum given encoding memory of the proposed LDPC convolutional code can improve the decoding performance. The characteristic parameters and simulation results show that the proposed LDPC convolutional codes are excellent .关键词：LDPC convolutional codes;time-invariant;given rate;given memory;fast encoding
- 283
- |
- 433
- |
- 0
发布时间：2023-12-11 - 摘要：Combining techniques of mobile computing, image retrieval, wireless communications and Internet, Mobile Visual Search (MVS) aims to provide a mobile image retrieval services for mobile terminal user. Limited bandwidth in wireless network is the key factor to affect the MVS technical development and application. The key technical of limited bandwidth in wireless network including low bit rate feature code and transmission strategy was analyzed, specially for the Compact Descriptor for Visual Search of MPEG-7. Moreover, future research direction and challenges of MVS are presented.关键词：mobile visual search (MVS);limited bandwidth in wireless network;low bit rate code;compact descriptors for visual search (CDVS)
- 286
- |
- 436
- |
- 0
发布时间：2023-12-11 - 摘要：The calculation of ripple current in input capacitor and the resonant voltage of output LC filter in high power buck converter is described. In regard to input capacitor, an accurate formula of calculating ripple current is derived through simulation and deduction, and the maximum ripple current point is stated. Theoretical analysis of the resonant voltage problem occurring in experiments is conducted using certain parameters in a LC filter model, such as inductor equivalent resistance and capacitor ESR. Also a Matlab simulation is conducted to observe its output response characteristics and a damper is added to eliminate resonance. This simple and effective method is verified by simulation and experiment.关键词：Buck converter;input capacitor;LC filter;Matlab simulation;resonant voltage
- 299
- |
- 545
- |
- 1
发布时间：2023-12-11 - 摘要：The strata settlement caused by shield construction in crossing tunnels has influence on the deformation or even damage of the existing tunnel. Therefore, the stochastic medium theory is presented to calculate the existing tunnel settlement caused by shield construction in crossing tunnels, and to analyze the principles. The fundamental equations of the stochastic medium theory is applied to the crossing tunnels engineering. The stochastic medium model of the settlement of the existing tunnel resulting from shield construction in crossing tunnels is established, and the choice of parameters for calculating was discussed. The analysis for engineering example showed that it is very effective to calculate the settlement of existing tunnel caused by the shield construction in the crossing tunnels with the stochastic medium theory. The research has certain guiding significance to the shield safety construction in crossing tunnels.关键词：crossing tunnels;shield construction;passing through;stochastic medium model;settlement
- 287
- |
- 464
- |
- 0
发布时间：2023-12-11 - 摘要：The initiation time for reinforced concrete (RC) members were researched along coast under chlorine salt erosion and climate. Based existing chlorine erosion life model, as temperature and relative humidity were considered, the initiation time for RC members were calculated. Then the probability distribution of the initiation time was given for RC members along coast in southeast china by using simplified probability analysis. The results showed:① The effect on initiation time from relative humidity should not be ignored; ② The factors, such as relative humidity influence coefficient f ( h ) , chloride ion diffusion delay coefficient m , chloride ion diffusion reference coefficient Dref, and concrete cover thickness X , had more obvious influence on initiation time. This would be useful for structure strengthening, maintenance, and remaining life prediction.关键词：chlorine salt erosion;concrete structures;temperature;relative humidity;initiation time
- 263
- |
- 445
- |
- 0
发布时间：2023-12-11 - 摘要：To study the secondary metabolites of Alternaria sp. XZSBG1 from Tibet. The chemical compounds were isolated and purified by silica gel, Sephadex LH-20, ODS-18 column chromatography, and HPLC. Their structures were characterized by NMR and MS analyses. The antitumor and enzyme inhibitory activities were investigated using MTT and colourimetry methods, respectively. Eight tetrahydroanthraquinone derivatives were isolated from the extract of the fungal strain Alternaria sp. XZSBG-1, and their structures were determined to be Alterporriol F’ (1),Alterporriol G (2), Alterporriol F (3), Alterporriol G (4), Altersolanol A (5), Altersolanol F (6), Tetrahydroaltersolanol B (7) and Tetrahydroaltersolanol D (8) Only the compound 6 showed obvious inhibitory activity against HCT-116 and HeLa cell lines with the IC50values 3.026 and 8.094 μmol/L, respectively.关键词：Alternaria sp.;secondary metabolites;tetrahydroanthraquinones;antitumor activity
- 347
- |
- 440
- |
- 2
发布时间：2023-12-11 - 摘要：In order to study the secondary metabolites from the coralderived symbiotic fungi NG15-3 of South China Sea, the compounds were isolated by silica gel column chromatography and HPLC. Their structures were identified on the basis of spectral data and physical constant comparison. Four anthraquinones and six nitrogen compounds were isolated as preechinulin (1),emodin (2),1-O-methyl emodin(3),physcion (4),carviolin (5),cyclo-(Phe-Gly) (6),cyclo-(Gly-Pro) (7),3H-imidazole-4-carboxylic acid (8),2-methyl-3H-imidazole-4-carboxylic acid (9) and 1H-pyrrole-2-carboxylic acid (10). All the secondary metabolites were firstly acquired from the coralderived symbiotic fungi NG-15-3 of South China Sea and compound 1 was a precursors of the monodehydro-2,5diketopiperazines,which showed varied biological activity.关键词：coral-derived symbiotic fungi;NG-15-3;anthraquinones;nitrogen compounds;structural identification
- 410
- |
- 692
- |
- 4
发布时间：2023-12-11 - 摘要：In this paper a rapid and simple method using pyrolysis High Frequency Modulated light polarization coupled with Zeeman Atomic Absorption Spectrometry (ZAAS-HFM) was employed for the analysis of total mercury in fly ash samples. The factors those influence the experiment results, such as the sample matrix, quantity of samples, gas flow, memory effect, were studied. Under optimum conditions, the reproducibility of the method was within the range of 3.2%~3.8% for peak area and 5.2%~6.9% for peak height. The detection limit (3 σ ) was 0.002 0 μg·g-1 and the recoveries were within the range of 94.2%~98.5%. Three fly ash samples and three standard reference materials were analyzed. These results were consistent with those obtained by the Cold Vapor Atomic Absorption mercury analyzer (CVAAS), as shown by the result of t -test, no significant difference was found between these two methods. The method was simple，efficient and suitable for high throughput determination of total mercury in fly ash samples.关键词：pyrolysis;atomic absorption spectrometry;fly ash;mercury;fast determination
- 286
- |
- 435
- |
- 0
发布时间：2023-12-11 - 摘要：The aim of this work was to measure the concentrations of heavy metals in house dust and soil samples as well as study the characteristics and distribution of heavy metal pollution in the surrounding area of coal-fired power plant in Guangdong Province. The risk assessment of heavy metals in dust was also carried out using US EPA Health Risk Assessment Model. The results revealed that the order of concentrations of metals was Zn>Mn>Pb>Cu>Cr>As>Cd>Hg. The heavy metal pollution levels of dust were relatively high, which were higher than those in soil to varying degrees. The pollution of Zn, Pb, Cd and Cu in dust was likely to be anthropogenic, mainly due to industrial and traffic sources. However, the pollution of As, Hg and Mn in dust was not obviously anthropogenic. Spatial distribution of heavy metal in dust was clearly affected by soot emissions of power plant. Nemerow Indexes were significantly correlated with local wind direction and frequency, decreased with incremental distance from the power plant. It is evident that the concentrations of Pb, Zn and Hg also decreased with incremental distance from the power plant. Potential health risk for children was significantly higher than for adults. The non-cancer risk of metals was Pb>Mn>Cr>As>Zn>Cu>Hg>Cd, while the carcinogen risk of metals was As>Cr>Pb>Cd. In particular, the non-cancer risk of Pb for children was high, which required more attention. The non-cancer risks of other metals for children were low. Noncancer risks for adults were ignorable. Carcinogen risks of metals were in an acceptable range, indicating no carcinogenic hazard to children and adults.关键词：coal-fired power plant;dust;heavy metal;pollution characteristic;health risk
- 326
- |
- 459
- |
- 11
发布时间：2023-12-11 - 摘要：Based on the 5th and 6th Population Census, the spatial change and influence factors of population aging in Guangzhou City with street and town as the research unit were analyzed. The results indicate that: ① The population aging has been deepening with a decrease in regional differentiation and outward expansion in a circle direction. ② The population aging is going on most rapidly in the edge of the central urban area. ③ The tendency of spatial concentration of aged population and population aging has been weaken. Population aging continuously expands to the central city, and the north suburbs become the aggregation area of new streets and towns with stronger function of population concentration. ④ With regard of the influence factors to the spatial change of population aging, population movement plays a more important role compared to the natural growth of population. Economic development serves as the key factor stimulating aged people concentrated in the edge of central city, while educational level keeps positive impact on the regional differentiation of population aging.关键词：population aging;spatial and temporal characteristics;influence factors;Guangzhou
- 343
- |
- 533
- |
- 8
发布时间：2023-12-11 - 摘要：Based on monthly measured precipitation data of 60 meteorological stations over circumBohairegion from 1961 to 2013, the level and distribution years of the drought and flood were determined by using Z index. In order to explore the relative mechanism of the drought and flood over circumBohairegion, correlation analysis between the Sunspot activities and the drought and flood, and between ENSO events and the drought and flood was conducted, respectively, by using frequency analysis and Morlet wavelet method. The results showed that: ① The drought and flood occurred frequently, and the drought was slightly higher than the flood over circumBohairegion from 1961 to 2013. ② There was a significant negative correlation between relative Sunspot number and drought and flood index, and a significant positive correlation between relative Sunspot number and drought and flood level. The frequency of occurrence of the drought and flood in the Sunspot maximum years was higher than in the minimum years,and the drought was significantly more than the flood in the Sunspot maximum years. It was prone to the drought in singular cycle of Sunspot activity, while the drought and flood occurred alternately within dual period of Sunspot activity. ③ There was a significant negative correlation between ENSO events and drought and flood index,and a significant positive correlation between ENSO events and drought and flood level. The frequency of the drought and flood was the same in the EL Nino years and LA Nina years, and probability of the drought was significantly higher than the flood in the EL Nino years. ④ There was a good corresponding relationship between the Sunspot activities and small scale period of drought and flood index , namely, the quiet period of Sunspot corresponded to the abundant precipitation period and the active period of Sunspot corresponded to the less rainfall period, indicating that the Sunspot activities had a great influence on the alternating of drought and flood. The corresponding relationship was not consistent between ENSO events and small scale period of drought and flood index with the existence of staggered phenomenon, while ENSO events had great effect on the slipping of each scale period of drought and flood index.关键词：the drought and flood;Sunspot;the ENSO events;circum-Bohai-region
- 293
- |
- 455
- |
- 3
发布时间：2023-12-11 - 摘要：Dading iron mine in Lianping, Guangdong province is well known as the largest iron ore deposit, and is also the most typical skarn type deposit in South China. The LA-ICP-MS zircon U-Pb age of coarsegrain porphyritic biotite granite and mediumgrain porphyritic biotite granite from Dading pluton, closely related to mineralization in Dading mining area, are (174.3±3.6) Ma (MSWD=1.6) and (176.9±4.3) Ma(MSWD=2.6)，respectively, and it shows the emplacement age of Shibei pluton belonged to the early Jurassicmiddle Jurassic, and it was the product of the first magma activity of yanshanian period. The Shibei pluton was formed in extrusion tectonic setting, in the process of subduction of the Pacific plate under Eurasian plate in the early Mesozoic. Its source mainly from crust, formed by crustal material melting and magma consolidation, similar to the Fogang pluton, is crustal transformation type(Stype) granite.关键词：LA-ICP-MS zircon U-Pb dating;geological significance;Dading iron mine;Shibei pluton
- 350
- |
- 469
- |
- 1
发布时间：2023-12-11 - 摘要：Based on shortterm (52 h in consecutive spring and neap tidal cycles) hourly water quality data and longterm hourly electrical conductivity monitoring data of coastal shallow groundwater in northeastern part of Hainan, shortterm and longterm water quality fluctuations are analyzed. The results indicate that: ① Na+and Cl-are chief ions in shallow groundwater in the research area and vary with quasi-synchronization, which bring about major changes of TDS. Extremely low amount of CO2-3can be found in shallow groundwater. Mutual relations of cation are all positive correlated with distinct intensity at different sites, and are apparently influenced by tidal cycles. Different types of tidal cycles also lead to interchange between positive and negative correlations among anion. ② Soil alkalization degree caused by shallow groundwater increases from the north to the east, from lowmedium level to mediumhigh level. Intensity of seawater intrusion keeps a medium-high level, especially at the spring tidal cycle. Results from water mineralization imply that water quality of the study area is classified between brackish water and salt water. ③ During study period, electrical conductivity vs. mineralization, and electrical conductivity vs.Na++Cl-both obey individual linear correlation rules and can be hardly affected in different tidal cycles, which means that long-term monitoring of water mineralization, Na+and Cl-can be possible. Also, it means a lot to longterm monitoring of water quality and seawater intrusion. ④ Long-term fluctuations and probability distributions of electrical conductivity follow respective rules which depend more on locations. ⑤ More sharper changes can exist in the amount of Na+and Cl-than in water mineralization from a long-term view. A great quantity of fresh water discharged from estuary of the Nandu River and occasional seawater intrusions may be the immediate causes for changes in the contents of Na+and Cl-in shallow groundwater of northern study area.关键词：Hainan;coastal area;shallow groundwater;water quality
- 266
- |
- 476
- |
- 2
发布时间：2023-12-11 - 摘要：The normalized difference water index (NDWI), normalized difference water index based on blue light (NDWIB) and combined index of NDVI and NIR were applied to water body identification (CIWI), and the discrimination to farmlands, roadways and settlement places was calculated using HJ1A/1B CCD date of 300 samples from the Hainan Island. The discrimination of CIWI water index model is the highest, with the comprehensive discrimination of 34.61% and it is the optimal model of water recognition in the Hainan Island. The best recognition threshold of CIWI water index model (168.54) was confirmed. It was used to extract water information on 24th of February and 24th of September, 2014 efficiently, with the total island water area of 677.41 km2and 698.62 km2respectively. The total accuracy of water extraction reaches 92.00%. The CIWI water index model has the advantages of large discrimination of land and water and high precision extraction of water area, which can be used to extract water information of Hainan Island. This paper provides reference for optimized allocation and management and dynamic monitoring of flood disaster for water resources in Hainan Island.关键词：HJ-1A/1B CCD;water index;water extraction;CIWI;Hainan Island
- 337
- |
- 453
- |
- 1
发布时间：2023-12-11
- Postal code：510275
- Tel：020-84112585，84113223 Email：xuebaozr@mail.sysu.edu.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0