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利用化石群分异度探讨古水深 被引量:15
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作者 郭秋麟 倪丙荣 《石油大学学报(自然科学版)》 CSCD 1990年第2期1-7,共7页
古水深的确定是长期未解决的难题,同时也是急需解决的问题。化石群分异度的研究为确定古水深提供了一种新方法。本文通过多方面研究,证实了信息函数与优势度两种分异度与水深之间存在着密切的关系,并利用该关系估算出东营盆地沙三晚期... 古水深的确定是长期未解决的难题,同时也是急需解决的问题。化石群分异度的研究为确定古水深提供了一种新方法。本文通过多方面研究,证实了信息函数与优势度两种分异度与水深之间存在着密切的关系,并利用该关系估算出东营盆地沙三晚期的水体深度范围。 展开更多
关键词 化石群 分异变 古水深 盆地
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解单调异变分不等式的预测校正法 被引量:1
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作者 韩乔明 何炳生 《科学通报》 EI CAS CSCD 北大核心 1998年第9期921-924,共4页
给出了解异变分不等式的预测校正投影法 ,它收敛条件弱 ,工作量少 ,克服了显式方法和隐式方法的弱点 ,保留了优点 .
关键词 不等式 预测校正投影法 非线性规划
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On Spatial Variability and Distribution of Soil Nutrients in Different Nitraria tangutorum Bobr.Populations in Tsaidam Basin 被引量:1
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作者 苏艳 邱权 +5 位作者 何茜 李吉跃 王军辉 王宁 孙奎 贾子瑞 《Agricultural Science & Technology》 CAS 2015年第2期285-291,共7页
In this paper,six important distribution areas of Nitraria tangutorum Bobr.in Tsaidam Basin were selected as research objects,to study spatial variability and distribution of soil nutrients in different N.tangutorum p... In this paper,six important distribution areas of Nitraria tangutorum Bobr.in Tsaidam Basin were selected as research objects,to study spatial variability and distribution of soil nutrients in different N.tangutorum populations and analyze the relationship between soil nutrient contents and geographical location,by measuring soil pH and the contents of organic matter(OM),total nitrogen(N),total phosphorus(P),total potassium(K),hydrolysis N,available P and available K in soils.Results showed that:(1) soil nutrient contents among different populations showed significant spatial variability,and soil depth had a significant effect on soil nutrients contents,but the variation rules were not obvious.(2)Average pH and average contents of OM,total N,total P,total K,hydrolysis N,available P and available K in soils with different depths(0-15,15-30,30-45 cm) varied in the range of 8.37-9.21,3.34-20.68,0.18-1.21,0.35-0.75,16.12-22.04,5.13-553.28,1.10-52.54 and 103.83-562.28 mg/kg,respectively.(3) The analysis results of correlation between average values of pH and contents of nutrient indexes in soils with different depths(0-15,15-30,30-45 cm) showed that the correlation of these indexes were different.(4)OM and total N contents in soils with different depths(0-15,15-30,30-45 cm) all had a significant positive correlation with latitude and negative correlation with longitude and altitude,and the correlation of available P and available K contents in surface soils(0-15 cm) with latitude,longitude and altitude were significant positive,significant negative and significant negative,respectively;moreover,longitude and latitude also showed a significant impact on soil available K contents with the depth of 30-45 cm.In addition,comprehensive analysis result of nutrient contents showed that N.tangutorum populations in Huaitou Tala Town had the highest fertility,and the fertility levels of N.tangutorum populations in Chaka Town and Wulan Keke Town were relatively lower. 展开更多
关键词 Soil nutrients Spatial variability Geographical location Nitraria tangutorum Bobr. Tsaidam Basin
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Variation and Cluster Analysis on Leaf Characters from Different Provenance Sources of Polygonum multiflorum Thunb 被引量:2
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作者 韦艳梅 王凌晖 +2 位作者 曹福亮 韦山青 梁耀丹 《Agricultural Science & Technology》 CAS 2010年第6期94-98,共5页
[Objective] The aim was to study the variation of leaf characters from different provenance sources of Polygonum multiflorum Thunb,as well as to carry out cluster analysis on P.multiflorum from different provenance so... [Objective] The aim was to study the variation of leaf characters from different provenance sources of Polygonum multiflorum Thunb,as well as to carry out cluster analysis on P.multiflorum from different provenance sources to provide basis for the classification,identification,breeding and improved variety selection of P.multiflorum.[Method] Leaf shape characters of 31 copies of germplasm resources in the major distribution region of the whole country were determined,and the genetic variation of P.multiflorum leaves from different producing areas was analyzed.[Result] The leaf characters of single plant of the same experimental provenance source of P.multiflorum were relatively stable,the variation was mainly found on the single leaf area,1/2 leaf width,leaf width and other indicators;the variation of each leaf character among different provenance sources was obvious,and the variation was mainly found on the single leaf weight,leaf area,1/2 leaf width,leaf length and other indicators.The correlation analysis of each leaf character in P.multiflorum suggested that the single leaf area and single leaf weight showed extremely significant positive correlation with leaf length,1/2 leaf width,leaf width,leaf thickness and leaf stem length,while the single leaf area and single leaf weight showed significant negative correlation with WWR(leaf width/1/2 leaf width)and LWR(leaf length/1/2 leaf length),in addition,several macroscopic leaf characters such as leaf length,1/2 leaf width,leaf width,leaf stem length showed extremely positive correlation.The main component analysis result suggested that the contribution rate of accumulation variance of the front three main components was up to 97.4%,which could better reflect the comprehensive performance of leaf characters of different provenance sources of P.multiflorum.The cluster analysis showed that the experimental 31 copies of P.multiflorum provenance sources should be divided into three classes,the first class was distributed in the Middle,Western of Guizhou,northwestern of Guangxi and western areas with higher altitude;the second class was distributed in Hunan,Hubei,Sichuan,Guangdong and the most area of Guangxi;the third class was distributed in Anhui,Jiangsu and Henan and Shandong.[Conclusion] Cluster analysis of leaf characters indicated that the kinds of provenance sources which the geographical position was closer could be got together.The study had provided a certain basis for the classification of P.multiflorum. 展开更多
关键词 Polygonum multiflorum Thunb Leaf characters VARIATION Cluster analysis
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A Preliminary Study on Genetic Variation of g E Gene of an Epidemic Pseudorabies Virus Strain and Its Pathogenicity to Piglets 被引量:3
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作者 郭容利 王继春 +4 位作者 茅爱华 温立斌 李彬 倪艳秀 何孔旺 《Agricultural Science & Technology》 CAS 2015年第5期926-930,共5页
[Objective] This study aimed to investigate the genetic variation of g E gene of an epidemic pseudorabies virus(PRV) strain and its pathogenicity to piglets. [Method] By serial passage in Vero cells, a PRV strain wa... [Objective] This study aimed to investigate the genetic variation of g E gene of an epidemic pseudorabies virus(PRV) strain and its pathogenicity to piglets. [Method] By serial passage in Vero cells, a PRV strain was isolated from the brain tissues of stillborn fetuses delivered by sows with suspected PRV infection and preliminarily identified by PCR. g E gene of the isolated PRV strain was amplified and sequenced for phylogenetic analysis. In addition, the pathogenicity of the isolated PRV strain to 6-week-old piglets was evaluated. [Result] A PRV strain was successfully isolated and named PRV N5 B strain, which could proliferate in Vero cells and TCID50 of the 15 thgeneration virus liquid reached 10^7.125/0.1 ml. Specific bands could be amplified by PCR. g E gene in the isolated PRV strain was 1 740 bp in length. A phylogenetic tree was constructed based on full-length g E sequences, which showed that PRV N5 B strain and PRV strains isolated since 2012 were clustered into the same independent category and shared 99.7%-100% homology of nucleotide sequences. Compared with related sequences published previously, there were insertions of three consecutive bases at two loci. Animal experiments showed that intranasal inoculation of 6-week-old piglets with 2 ml of PRV N5 B strain(10^6/0.1 ml) led to a mortality rate of 100%. [Conclusion] In this study,genetic variability of g E gene in PRV N5 B isolate and its pathogenicity to piglets were analyzed, which provided a theoretical basis for the development of new vaccines to prevent and control porcine pseudorabies. 展开更多
关键词 Pseudorabies virus ISOLATION Identification Genetic variation PATHOGENICITY
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Graft-induced Inheritable Variation in Mungbean and Its Application in Mungbean Breeding 被引量:23
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作者 张丹华 孟昭璜 +2 位作者 肖卫民 王学臣 苏都莫日根 《Acta Botanica Sinica》 CSCD 2002年第7期832-837,共6页
Graft can induce inheritable variations in the progenies of the scion plants. Seedling of mungbean ( Vigna radiata (L.) Wilczek) was grafted onto the stem of sweet potato ( Ipomoea batatas (L.) Lam.). The growth... Graft can induce inheritable variations in the progenies of the scion plants. Seedling of mungbean ( Vigna radiata (L.) Wilczek) was grafted onto the stem of sweet potato ( Ipomoea batatas (L.) Lam.). The growth of the scion was maintained until the scion produced selfed seeds. We sowed the seeds for several generations under normal conditions. Distinct genetic variations appeared in the progenies. Similar variations did not appear in the generations of the scion sowed normally without graft. The variations seemed to be induced by the graft and they inherited steadily. For understanding the possible mechanism of the phenomenon (graft_induced inheritable variation), we analyzed the cytoplasmic and genomic DNA of the variations. The results showed that there was no restriction fragment length polymorphism (RFLP) in the cytoplasmic DNA between the original scion and the variation. However, significant difference between the scion and variation was recognized by random amplified polymorphic DNA (RAPD) analysis. In addition, there was no evidence that indicated the gene transformation from stock to scion. Our results suggest that the non_specific grafting has a pragmatic potential for plant breeding and crop improvement and, the genetic variation seems not to be caused simply by DNA transformation but most likely the stress induced mutation. 展开更多
关键词 GRAFT genetic variation MUNGBEAN sweet potato RAPD analysis crop improvement
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The analysis on IP signals in TEM response based on SVD 被引量:4
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作者 余传涛 刘鸿福 +2 位作者 张新军 杨德义 李自红 《Applied Geophysics》 SCIE CSCD 2013年第1期79-87,119,共10页
During transient electromagnetic method (TEM) exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon (a voltage change from positive to negative) caused by the influence of the i... During transient electromagnetic method (TEM) exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon (a voltage change from positive to negative) caused by the influence of the induced polarization (IP) effect, which affects the depth and precision of the TEM detection. The conventional inversion method is inefficient because it is difficult to process the data. In this paper, the Cole-Cole model is adopted to analyze the effect of Dc resistivity, chargeability, time constant, and frequency exponent on the TEM response in an homogeneous half space model. Singular Value Decomposition (SVD) is used to invert the measured TEM data, and the Dc resistivity, chargeability, time constant and frequency exponent were extracted from the measured TEM data in the mine area. The extracted parameters are used for interpreting the detection result as a supplement. This reveals why the TEM data acquired in the area has a low resolution. It was found that the DC resistivity and time constant do not significantly change the results, however, the chargeability and frequency exponent have a significant effect. Because of these influences, the SVD method is more accurate than the conventional method in the apparent resistivity profile. The area of the copper mine is confined accurately based on the SVD inverted data. The conclusion has been verified by drill and is identical to the practical geological situation. 展开更多
关键词 SVD method TEM response IP effects Cole-Cole models
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Variation of Water-Use Efficiency of Leymus chinensis and Cleistogenes squarrosa in Different Plant Communities in Xilin River Basin, Nei Mongol 被引量:6
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作者 陈世苹 白永飞 韩兴国 《Acta Botanica Sinica》 CSCD 2002年第12期1484-1490,共7页
Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon d... Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon dioxide concentration and thus of water-use efficiency (WUE) in plants, were measured on Leymus chinensis (Trin.) Tzvel. and Cleistogenes squarrosa (Trin.) Keng. in six communities of different habitats in die Xilin River Basin. The foliar delta C-13 values of both species tended to increase with decreasing soil water content (SWC) and a significant negative correlation was found between foliar delta C-13 Values and SWC in different soil layers, indicating that the two species could change WUE according to water availability. We also found relatively constant leaf water contents (LWC) of the two species in different habitats. Our results implied that the two steppe species might have adapted to different soil water regimes either through adjusting stomatal conductance to get a proper WUE, or through enhancing the osmosis-regulating ability to keep a relatively stable LWC. Our findings could partially explain why the two plant species have a wide distribution range and become dominant in the Xilin River Basin. 展开更多
关键词 Xilin River Basin Leymus chinensis Cleistogenes squarrosa water-use efficiency delta C-13 value
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Contourlet watermarking algorithm based on Arnold scrambling and singular value decomposition 被引量:3
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作者 陈立全 孙晓燕 +1 位作者 卢苗 邵辰 《Journal of Southeast University(English Edition)》 EI CAS 2012年第4期386-391,共6页
A new digital watermarking algorithm based on the contourlet transform is proposed to improve the robustness and anti-attack performances of digital watermarking. The algorithm uses the Arnold scrambling technique and... A new digital watermarking algorithm based on the contourlet transform is proposed to improve the robustness and anti-attack performances of digital watermarking. The algorithm uses the Arnold scrambling technique and the singular value decomposition (SVD) scheme. The Arnold scrambling technique is used to preprocess the watermark, and the SVD scheme is used to find the best suitable hiding points. After the contourlet transform of the carrier image, intermediate frequency sub-bands are decomposed to obtain the singularity values. Then the watermark bits scrambled in the Arnold rules are dispersedly embedded into the selected SVD points. Finally, the inverse contourlet transform is applied to obtain the carrier image with the watermark. In the extraction part, the watermark can be extracted by the semi-blind watermark extracting algorithm. Simulation results show that the proposed algorithm has better hiding and robustness performances than the traditional contourlet watermarking algorithm and the contourlet watermarking algorithm with SVD. Meanwhile, it has good robustness performances when the embedded watermark is attacked by Gaussian noise, salt- and-pepper noise, multiplicative noise, image scaling and image cutting attacks, etc. while security is ensured. 展开更多
关键词 digital watermarking contourlet transform Arnold scrambling singular value decomposition (SVD)
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Genetic Variation Analysis of 3D Gene and Molecular Detection of Porcine Kobuvirus in 2013-2014
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作者 倪艳秀 何孔旺 +10 位作者 茅爱华 俞正玉 李彬 郭容利 吕立新 祝昊丹 周俊明 温立斌 张雪寒 王小敏 汪伟 《Agricultural Science & Technology》 CAS 2015年第3期442-446,共5页
[Objective] This study aimed to investigate the prevalence and variation of porcine kobuvirus (PKV) in suckling piglets in China. [Method] In 2013-2014, 224 feces samples from suckling piglets with diarrhea in 27 pi... [Objective] This study aimed to investigate the prevalence and variation of porcine kobuvirus (PKV) in suckling piglets in China. [Method] In 2013-2014, 224 feces samples from suckling piglets with diarrhea in 27 pig farms of five provinces in China were collected to detect 3D genes of PKV with RT-PCR method; the sequences and genetic variation of 29 PKV 3D genes were analyzed. [Result] Total positive rate of PKV in feces samples from suckling piglets with diarrhea was 65.18% (146/224); total positive rate of PKV in pig farms was 85,2% (23/27); nucleotide sequences and the deduced amino acid sequences of 29 PKV 3D genes shared 87.0%-100% and 92.7%-100% homologies with six PKV-related 3D sequences, respectively. [Conclusion] PKV infection is prevalent in suckling piglets in China; PKV 3D genes exhibit high diversity. 展开更多
关键词 Porcine kobuvirus Molecular detection 3D gene Genetic variation analysis
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Physiological Analysis of Two Arabidopsis thaliana Mutants in Response to CO2 被引量:11
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作者 宋玉伟 陈家宝 刘宗才 《Agricultural Science & Technology》 CAS 2009年第2期12-14,共3页
[Objective] The 15urpose was to seek for the different phenotypes between wild type and Arabidopsis Mutants in response to CO2. [Method] The epidermis bioassays and seed germination test were carried out to analyze th... [Objective] The 15urpose was to seek for the different phenotypes between wild type and Arabidopsis Mutants in response to CO2. [Method] The epidermis bioassays and seed germination test were carried out to analyze the physiological characteristics of two Arabidopsis mu- tants and their wild type. [Result] There existed distinct differences in stomata apertures, water loss and leaf temperature compared with wild type except for stomata density. In addition, seed germination test on the medium indicated that cdfl was insensitive to ABA, mannitol and NaCI, but cdsl performed contrary to cdil. [ Conclusion] There are some different physiological characteristics between wild type and mutants. 展开更多
关键词 Arabidopsis thaliana CO2 MUTANT
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Description of a new parthenogenetic species of Thalassaphorura (Collembola: Onychiuridae) from East China, with DNA barcoding analyses
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作者 高艳 卜云 《Entomotaxonomia》 CSCD 北大核心 2014年第1期1-7,共7页
Thalassaphorura houtanensis sp. nov. from Shanghai, East China is described. It is similar to T. encarpata (Denis, 1931) in having labial palp of type A and the same pseudocelli formula on the body. It can be distin... Thalassaphorura houtanensis sp. nov. from Shanghai, East China is described. It is similar to T. encarpata (Denis, 1931) in having labial palp of type A and the same pseudocelli formula on the body. It can be distinguished by the shape of unguis, chaetotaxy of labium, maxillary out lobe and ventral tube. It was confirmed as an absolutely parthenogenetic species after a reproduction test in the lab. In addition, the DNA barcoding sequences of this new species were sequenced and analyzed. The intraspecific genetic divergence is 0.18% on average and ranges from zero to 0.46%. 展开更多
关键词 Arthropleona SPRINGTAIL taxonomy genetic divergence REPRODUCTION
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A Broadband Long-Wavelength Superluminescent Diode Based on Graded Composition Bulk InGaAs
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作者 丁颖 王圩 +2 位作者 阚强 王宝军 周帆 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2005年第12期2309-2314,共6页
A novel unselective regrowth buried heterostructure long-wavelength superluminescent diode (SLD) with a graded composition bulk InGaAs active region is developed by metalorganic vapor phase epitaxy (MOVPE). At a 1... A novel unselective regrowth buried heterostructure long-wavelength superluminescent diode (SLD) with a graded composition bulk InGaAs active region is developed by metalorganic vapor phase epitaxy (MOVPE). At a 150mA injection current, the full width at half maximum of the emission spectrum of the SLD is about 72nm, ranging from 1602 to 1674nm. The emission spectrum is smooth and flat. The ripple of the spectrum is less than 0.3dB at any wavelength from 1550 to 1700nm. An output power of 4.3mW is obtained at a 200mA injection current under continuous-wave operation at room temperature. This device is suitable for the applications of light sources for gas detectors and L-band optical fiber communications. 展开更多
关键词 BROADBAND superluminescent diodes graded composition buried hetero-structure
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Study on the Variation in Growth Traits of Cupressus funebris
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作者 谭小梅 周益权 《Agricultural Science & Technology》 CAS 2015年第3期558-561,共4页
[Objective] This study aimed to investigate the variation in growth traits of Cupressus funebris in Chongqing Municipality, thus laying the foundation for further breeding and improvement of fine varieties. [Method] G... [Objective] This study aimed to investigate the variation in growth traits of Cupressus funebris in Chongqing Municipality, thus laying the foundation for further breeding and improvement of fine varieties. [Method] Growth traits of three fine stands of C. funebris in Qijiang, Pengshui and Youyang of Chongqing Municipality were investigated. [Result] The results showed that C. funebris stand in Pengshui exhibited the best growth performance, followed by C. funebris stand in Qijiang; C. funebris stand in Youyang exhibited the poorest growth performance. The average volume growth of C. funebris in Pengshui, Qijiang and Youyang was 0.14, 0.11 and 0.06 m^3, respectively. Among different stands, variation coefficients of major growth traits were above 11.31%, and the maximum variation coefficient of the volume was 39.11%; within the stands, variation coefficients of plant height were basically the same (about 20%). The variation coefficient of diameter at breast height in Qijiang reached the maximum of 42.42%, followed by that in Youyang. The variation coeffi- cients of volume and diameter at breast height were consistent; seed bearing coefficient (SBC) of C. funebris stand in Pengshui exhibited the maximum variation, which indicated that C. funebris stand in Pengshui was conducive to establishing seed stands and constructing seed orchard by using the selected stands. [Conclusion] It is necessary to conduct provenance selection. 展开更多
关键词 Cupressus funebris Growth traits VARIATION PROVENANCE STAND
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Seed Morphology and Seedling Variation of Four Ornamental Lupin Pedigrees
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作者 高柱 王小玲 +3 位作者 刘腾云 高松金 喻琼 余发新 《Agricultural Science & Technology》 CAS 2015年第1期57-62,67,共7页
[Objective] This study was conducted to reveal seed characteristics, variation and their effects on seedling growth of ornamental lupins. [Method] The phenotypic characteristics and germination rate of the seeds of fo... [Objective] This study was conducted to reveal seed characteristics, variation and their effects on seedling growth of ornamental lupins. [Method] The phenotypic characteristics and germination rate of the seeds of four excellent lupin pedigrees were measured, and then their correlations with seeding growth were analyzed. [Result] There were abundant variations among the four ornamental lupin pedigrees. Pink seeds had the largest volume and red seeds had the largest 1 000seed weight. The variation coefficients for the seed morphological traits among the four pedigrees ranged from 2.97% to 14.34%. Seed specific weight and 1 000-seed weight could be used as important indicators for selection in breeding because of their higher variability. Seed weight variation of ornamental lupin was mainly depen- dent on seed width variation. There was small variation in seed length. The seeds of the four ornamental lupin pedigrees started to germinate one day after sowing, and the germination period was 5 d. Germination rate coefficient and germination index of pink and red seeds were higher than those of blue seeds, but blue seeds had the largest germination rate. 1 000-seed weight shared significantly positive correlations with seed germination rate, germination potential and seedling retention rate. Round and large seeds had some advantages in germination. Full seeds had higher germination rate and speed, and seedling retention rate. There was a significant relationship between seed length-width ratio and the number of leaflets of seedlings. [Conclusion] The results provided references for the evaluation of seed phenotypic diversity and breeding research of ornamental lupins. 展开更多
关键词 Ornamental lupin PEDIGREE Seed morphology Seedling variation Correlation analysis
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Genetic Variation of Porcine Circovirus Type 2 Isolate 201105ZJ
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作者 王小敏 何孔旺 +5 位作者 汪伟 周忠涛 杨光远 茅爱华 俞正玉 倪艳秀 《Agricultural Science & Technology》 CAS 2014年第11期1860-1864,1887,共6页
[Objective] This study aimed to investigate the genetic variation of porcine circovirus type 2 (PCV2) in China. [Method] The strain was isolated from infected samples by cel passage and preliminarily identified by P... [Objective] This study aimed to investigate the genetic variation of porcine circovirus type 2 (PCV2) in China. [Method] The strain was isolated from infected samples by cel passage and preliminarily identified by PCR and IFA. Ful-length genome of the isolated strain was obtained by specific amplification for homology and phylogenetic analysis. [Result] A PCV2 strain was successful y isolated and named 201105ZJ, which could proliferate in PK15 cel lines. Specific fragments could be amplified by specific PCR assay. According to results of IFA assay, specif-ic immunofluorescence was observed; the TCID50 was low (102.67); the ful-length genome sequence of the isolated strain was 1 768 bp, sharing 94.1%-96.8% ho-mology with 13 reference strains; to be specific, the isolated strain exhibited the highest homology of 96.8% with AF055392PCV2a; the isolated strain 201105ZJ and reference strain AF055392 belonged to genotype PCV2a, exhibiting a distant genetic relationship with genotype PCV2c. [Conclusion] Characteristics of genetic variation of PCV2 isolate 201105ZJ provided theoretical basis for vaccine development, investi-gation of PCV2 pathogenesis, and prevention and control of porcine circovirus-as-sociated diseases (PCVAD) in East China. 展开更多
关键词 Porcine circovirus type 2 Isolation Identification Genetic variation
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A comparison analysis of multipath extract methods in short-baseline applications of GPS
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作者 崔冰波 陈熙源 《Journal of Southeast University(English Edition)》 EI CAS 2014年第3期315-317,共3页
In order to eliminate the multipath errors existing in static short-baseline applications, a novel de-noising method based on a singular spectrum analysis (named as DSSA) is introduced to extract multipath signals. ... In order to eliminate the multipath errors existing in static short-baseline applications, a novel de-noising method based on a singular spectrum analysis (named as DSSA) is introduced to extract multipath signals. The multipath error is extracted from the double difference (DD) residuals by DSSA and then applied to the correct multipath error in subsequent measurements based on the correlation among adjacent epochs. Methods based on discrete wavelet transform (DWT) and stationary wavelet transform (SWT) are introduced as comparisons of DSSA based on analysis of a simulated signal. Real baseline residuals are tested to verify different extract methods. Results show that compared with the SWT, the DSSA improves the root mean square (RMS) of the residual by 48.6% and achieves a time reduction of 75.3%. 展开更多
关键词 multipath extraction singular spectrum analysis stationary wavelet transform
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Method of variation of parameters for solving a constrained Birkhoffian system
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作者 张毅 《Journal of Southeast University(English Edition)》 EI CAS 2013年第3期342-345,共4页
For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for s... For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for solving the dynamical equations of the constrained Birkhoffian system is provided.First the differential equations of motion for the constrained Birkhoffian system as well as for the corresponding free Birkhoffian system are established.Secondly a system of auxiliary equations is constructed and the general solution of the equations is found.Finally by varying the parameters and utilizing the properties of the generalized canonical transformation of the Birkhoffian system the solution of the problem can be obtained.The proposed method reveals the inherent relationship between the solution of a free Birkhoffian system and that of a constrained Birkhoffian system. The research results are of universal significance which can be further used in a variety of constrained mechanical systems such as non-conservative systems and nonholonomic systems etc. 展开更多
关键词 Birkhoffian mechanics method of integration method of variation of parameter constrained Birkhoffian system
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Molecular characteristics and stages of chronic hepatitis B virus infection 被引量:33
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作者 Ying-Hui Shi Chang-He Shi 《World Journal of Gastroenterology》 SCIE CAS CSCD 2009年第25期3099-3105,共7页
Hepatitis B virus (HBV) is a common viral pathogen that causes a substantial health burden worldwide. Remarkable progress has been made in our understanding of the natural stages of chronic HBV infection. A dynamic ba... Hepatitis B virus (HBV) is a common viral pathogen that causes a substantial health burden worldwide. Remarkable progress has been made in our understanding of the natural stages of chronic HBV infection. A dynamic balance between viral replication and host immune response is pivotal to the pathogenesis of liver disease. Knowledge of the HBV genome organization and replication cycle can unravel HBV genotypes and molecular variants, which contribute to the heterogeneity in outcome of chronic HBV infection. Most HBV infections are spontaneously resolved in immunocompetent adults, whereas they become chronic in most neonates and infants at a great risk of developing complications such as cirrhosis and hepatocellular carcinoma (HCC). Those with chronic HBV infection may present in one of the four phases of infection: immune tolerance, immune clearance [hepatitis B eantigen (HBeAg)-positive chronic hepatitis B (CHB)], inactive carrier state, and reactivation (HBeAg-negative CHB). Understanding the dynamic nature of chronic HBV infection is crucial in the management of HBV carriers. Long-term monitoring and optimal timing of antiviral therapy for chronic HBV infection help to prevent progression of HBV-related liver disease to its later stage, particularly in patients with higher risk markers of HCC, such as serum DNA concentration, HBeAg status, serum aminotransferase, HBV genotypes, and pre-core or core mutants. 展开更多
关键词 Hepatitis B virus PATHOLOGY Immune tolerance Immune clearance Inactive hepatitis B surface antigen carriers REACTIVATION T-cell response CYTOKINES
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Small-Scale Spatial Variability of Soil Nutrients and Vegetation Properties in Semi-Arid Northern China 被引量:8
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作者 CHEN Fu-Sheng ZENG De-Hui HE Xing-Yuan 《Pedosphere》 SCIE CAS CSCD 2006年第6期778-787,共10页
A field experiment was conducted at Kezuohouqi County, Inner Mongolia Autonomous Region of China, which was located on the southeastern edge of the Horqin Sandy Land, to study the spatial variability of soil nutrients... A field experiment was conducted at Kezuohouqi County, Inner Mongolia Autonomous Region of China, which was located on the southeastern edge of the Horqin Sandy Land, to study the spatial variability of soil nutrients for a smallscale, nutrient-poor, sandy site in a semi-arid region of northern China; to investigate whether or not there were 'islands of fertility' at the experimental site; and to determine the key nutrient elements that sustained ecosystem stability. Results obtained from geostatistical analysis indicated that the spatial distribution pattern of soil total nitrogen (STN) was far different from those of soil organic matter (SOM), total phosphorus (STP), and total potassium (STK). Compared to SOM, STP, and STK, STN had a lower structural heterogeneity ratio and a longer range, while other elements were all similar. In addition, STN had an isotropic spatial structure, whereas the others had an anisotropic spatial structure. The spatial structure patterns of herbage species, cover,and height also differed, indicating that spatial variability was subjected to different ecological factors. Differences in the spatial variability patterns among soil nutrients and vegetation properties showed that soil nutrients for a small-scale were not the primary limiting factors that influenced herbage spatial distribution patterns. Incorporating spatial distribution patterns of tree species, namely, Pinus sylvestris var. mongolica Litv. and shrub Lespedeza bicolor Turcz. in a research plot and using fractal dimension,SOM, STP, and STK were shown to contribute to the 'islands of fertility' phenomenon, however STN was not, possibly meaning that nitrogen was a key limiting element. Therefore, during restoration of similar ecosystems more attention should be given to soil nitrogen. 展开更多
关键词 Pinus sylvestris war. mongolica Litv. semi-arid region soil nutrients spatial variability species richness
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