新时期中国农地流转问题探析     

庞丽铷  王文昌 《勤云标准版测试》2007,(5)

对新时期中国农地流转过程中出现的主要问题——流转混乱和买卖土地进行了论述,分析了问题产生的根源,提出了解决问题的对策:规范政府行为、建立流转机制、加强相关立法、保护农民权益、鼓励农村人口向城市转移。  相似文献   

Multicolor observations of phobos with the viking lander cameras: evidence for a carbonaceous chondritic composition     

Pollack JB  Veverka J  Pang K  Colburn D  Lane AL  Ajello JM 《Science (New York, N.Y.)》1978,199(4324):66-69

The reflectivity of Phobos has been determined in the spectral region from 0.4 to 1.1 micrometers from images taken with a Viking lander camera. The reflectivity curve is flat in this spectral interval and the geometric albedo equals 0.05 +/- 0.01. These results, together with Phobos's reflectivity spectrum in the ultraviolet, are compared with laboratory spectra of carbonaceous chondrites and basalts. The spectra of carbonaceous chondrites are consistent with the observations, whereas the basalt spectra are not. These findings raise the possibility that Phobos may be a captured object rather than a natural satellite of Mars.  相似文献   

桔全爪螨自然种群生命表及其分析的改进   总被引：3，自引：0，他引：3  

田明义  梁广文 《华南农业大学学报》1994,15(3):39-44

通过系统调查和室内观察，采用平均历期法，组建以作用因子组配的桔全爪螨自然种群生命表。组配自然种群生殖力表，以内禀增长率（ｒｍ）等作为判断桔全爪螨种群数量发展趋势的指标。分析结果表明，在春季天敌对桔全爪螨种群数量的控制作用是明显的，但天敌作用不足以控制桔全爪螨种数量的增长，需辅助以其他措施进行控制。  相似文献   

Application of comptuter technology in fruit science     

Pang Xiaoming  Wan Shuyuan  Hu Chungen 《农业科学与技术》2003,4(2)

This paper summarized the application of computer technology in fruit science, including crop modelling,expert system, decision support system (DSS), computer vision (CV), the Internet, 3 "S" technology, etc. The existingproblems and prospects are also discussed in the paper.  相似文献   

Cleavage of proBDNF by tPA/plasmin is essential for long-term hippocampal plasticity     

Pang PT  Teng HK  Zaitsev E  Woo NT  Sakata K  Zhen S  Teng KK  Yung WH  Hempstead BL  Lu B 《Science (New York, N.Y.)》2004,306(5695):487-491

Long-term memory is thought to be mediated by protein synthesis-dependent, late-phase long-term potentiation (L-LTP). Two secretory proteins, tissue plasminogen activator (tPA) and brain-derived neurotrophic factor (BDNF), have been implicated in this process, but their relationship is unclear. Here we report that tPA, by activating the extracellular protease plasmin, converts the precursor proBDNF to the mature BDNF (mBDNF), and that such conversion is critical for L-LTP expression in mouse hippocampus. Moreover, application of mBDNF is sufficient to rescue L-LTP when protein synthesis is inhibited, which suggests that mBDNF is a key protein synthesis product for L-LTP expression.  相似文献   

The ecoresponsive genome of Daphnia pulex     

Colbourne JK  Pfrender ME  Gilbert D  Thomas WK  Tucker A  Oakley TH  Tokishita S  Aerts A  Arnold GJ  Basu MK  Bauer DJ  Cáceres CE  Carmel L  Casola C  Choi JH  Detter JC  Dong Q  Dusheyko S  Eads BD  Fröhlich T  Geiler-Samerotte KA  Gerlach D  Hatcher P  Jogdeo S  Krijgsveld J  Kriventseva EV  Kültz D  Laforsch C  Lindquist E  Lopez J  Manak JR  Muller J  Pangilinan J  Patwardhan RP  Pitluck S  Pritham EJ  Rechtsteiner A  Rho M  Rogozin IB  Sakarya O  Salamov A  Schaack S  Shapiro H  Shiga Y  Skalitzky C  Smith Z  Souvorov A  Sung W 《Science (New York, N.Y.)》2011,331(6017):555-561

We describe the draft genome of the microcrustacean Daphnia pulex, which is only 200 megabases and contains at least 30,907 genes. The high gene count is a consequence of an elevated rate of gene duplication resulting in tandem gene clusters. More than a third of Daphnia's genes have no detectable homologs in any other available proteome, and the most amplified gene families are specific to the Daphnia lineage. The coexpansion of gene families interacting within metabolic pathways suggests that the maintenance of duplicated genes is not random, and the analysis of gene expression under different environmental conditions reveals that numerous paralogs acquire divergent expression patterns soon after duplication. Daphnia-specific genes, including many additional loci within sequenced regions that are otherwise devoid of annotations, are the most responsive genes to ecological challenges.  相似文献   

粗糙集神经网络在昆虫总科阶元分类学上的应用   总被引：2，自引：0，他引：2  

杜瑞卿  褚学英  王庆林  赵秋红  庞发虎 《中国农业大学学报》2007,12(1):33-38

为研究粗糙集和神经网络相结合方法的实践性,以及昆虫的数学形态特征在总科阶元上作为分类特征的可行性、可靠性和重要性。从总科角度对鳞翅目(Lepidoptera)和鞘翅目(Coleoptera)5个总科23种虫体图像中提取的昆虫面积、周长等11项数学形态特征进行粗糙集神经网络分析。结果表明:在总科阶元上,11项特征的可靠性大小为,面积、亮斑数>周长、横轴长、形状参数、圆形性、似圆度、偏心率>纵轴长、叶状性、球状性,与赵汗青等的统计分析结果中属性特征的重要性大多数一致;神经网络模式识别结果与传统分类结果完全一致。应用粗糙集理论进行昆虫数学形态特征分类结果准确;在昆虫总科阶元分类上粗糙集神经网络较统计学方法具有优势。  相似文献   

Combining ability among male sterile two-type and restorer lines of Zinnia elegans and implications for the breeding of this ornamental species     

XueYuan Lou  TingTing Lu  MaoJuan Li  RuiHua Pang  YaoMei Ye  ManZhu Bao 《Scientia Horticulturae》2011,129(4):862-868

Nineteen parental lines including five male sterile A-lines (AH002A, AH003A, AH209A, S5001A, J16A) and fourteen restorers (A1-GH, A3, S5, J6, J7N, J7J, J8, J9, J10, J11, J12, J13, J14, J17) were crossed using the North Carolina II statistical method. Studies of combining ability and heritability were conducted on selected parents along with their seventy F₁ hybrids for main ornamental traits. Plant height, crown size and length of node had obvious additive genetic effects, high (>0.50) broad sense heritability and high narrow sense heritability (length of node was medium). Pedicel length showed approximately equivalent maternal and paternal additive genetic effects, high broad sense heritability and medium (0.30–0.50) narrow sense heritability. Number of whorls of ray florets across capitulum and number of branches were able to take advantage of heterosis. The relationship between general combining ability and specific combining ability in Zinnia elegans depended on materials and traits. Male sterile two-type line was pivotal in the hybridization breeding of Z. elegans. S5001A, AH002A and A1-GH, A3, J14 which performed high negative GCA effects in PH, PL, LN and type I in PH, PL, NW, LN were ideal female and male parents of potted flowering plants; AH209A, J16A and S5, J10, J17 which displayed positive GCA effects and almost type I in PH, PL, LN were ideal female and male parents of cut flowers, respectively. For potted flowering plants, AH002A × J17, AH209A × A1-GH and S5001A × J6 with high negative SCA effects in PH, PL and LN were the most promising combinations, AH002A × S5, AH003A × A3 and J16A × J6 were the subprime combinations; for cut flowers, AH209A × S5, AH209A × J17 and J16A × J17 with high positive SCA effects in PH, PL and LN were the primary combinations, AH209A × J9 and S5001A × J10 were the secondary combinations.  相似文献   

Comparison of metabolic profiling of cyanidin-3-O-galactoside and extracts from blueberry in aged mice     

Yang H  Pang W  Lu H  Cheng D  Yan X  Cheng Y  Jiang Y 《Journal of agricultural and food chemistry》2011,59(5):2069-2076

The metabonomics changes of plasma and brain tissue after dietary supplementation with blueberry extracts (BBE) and cyanidin-3-O-galactoside from blueberry (BBM) in aged mice were investigated by (1)H NMR technique. The mice received intragastric administration of BBE (200 mg/kg/day), BBM (50 mg/kg/day), and saline water (0.9%) for 6 weeks, respectively, in the BBE, BBM, and control groups. At the end of the experiment, plasma and brain samples were collected for NMR analysis. The results demonstrated that the level of choline in plasma from BBE and BBM groups were obviously elevated relative to the control group, whereas the levels of lactate and phosphocholine in plasma were remarkably reduced. Compared with those in the control group, the levels of choline and GABA in the brain from the BBE group were obviously increased, whereas glutamate and phosphocholine in the BBE group were significantly decreased. The level of taurine in the brain from the BBM group was particularly higher than that in the control group. These results indicated supplementation with BBE or BBM might induce similar changes of endogenous plasma and brain metabolic profiles in aged mice.  相似文献   

动物及动物产品公路运输监督现状与对策   总被引：1，自引：0，他引：1  

逄永奎  臧力铭  陈春艳 《中国动物检疫》2011,28(9):8-9

公路是动物及动物产品运输的一条重要途径,我国在一些主要公路干线上设立了临时公路运输检疫监督站(点),对运输动物及其产品的过往车辆进行查证验物、消毒等检疫监督。但随着公路运营能力的日益增强和各地对公路运输监督检查站管理上的差异,在公路运输监督检查中存在的问题也日益复杂。  相似文献