葛藤根区AM真菌定殖率及孢子密度周年性变化初探

2004.7~2005.6在陕西省武功县以粉葛与药葛为调查对象,对葛藤根际AM真菌的定殖率和根际土壤的孢子数量进行了周年性调查。调查结果初步表明：不同品种间葛藤根区AM真菌定殖率不同,且随植物的生长周期呈现不同的变化趋势。粉葛的泡囊定殖率和总定殖率最高值出现在3月份, 4月份降至最低,药葛的总定殖率和泡囊定殖率最高出现在1月份而最低值出现在6月份。菌丝与丛枝定殖率在两品种间变化规律基本一致,高峰期都出现在冬季,低峰期则出现在春末夏初,夏季为葛藤根区AM 真菌的产孢高峰期,孢子密度与丛枝定殖率呈正相关,最低值出现在冬季,最高值出现在夏季,与葛藤的生长旺季相一致。     

银杏愈伤组织诱导与生长的优化试验

采用正交试验研究了四种外植体、基本培养基、萘乙酸（NAA）、6-苄基嘌呤（6-BA）4因素4水平及银杏幼叶汁和胚乳汁对银杏愈伤组织诱导及生长的影响。结果表明：银杏愈伤组织诱导和生长的最佳组合均是以子叶为最佳外植体,而培养基最佳组合分别是MS+ NAA 3.0 mg／L + BA 2.0 mg／L和SH+ NAA 3.0 mg／L + BA 1.5 mg／L;四种因子影响次序是外植体 ＞基本培养基＞NAA ＞ 6-BA;银杏胚乳汁促进愈伤组织生长,而银杏叶汁却抑制愈伤组织生长。     

Analysis of the Optimal Effect Radius of Regulator Station in Urban Gas Distribution Network with Medium Pressure

In urban gas network with multiple pressure ranges, there is an optimal effect radius, for which the annual calculating cost is minimal. According to the analysis of technology and economy about the gas supply with the medium pressure in urban gas transmission and distribution system, the optimal effect radius of regulator station in medium pressure gas network has been obtained.     

芥末精油对果蔬采后病原菌抑制效果的研究

研究了芥末精油对果蔬采后病原菌灰霉菌、链格孢、青霉菌和炭疽病菌的抑制效应,以确定其最低抑菌浓度与最低杀菌浓度。研究结果表明,芥末精油对供试的病原菌有较强的抑制效果,当芥末精油空间浓度达到2μL/L时,对4种病原菌的抑制作用均达到100％。相同浓度的芥末精油对不同的病原菌的抑制率均不同。     

Influence of Seed-Bed Preparation and Straw Utilization on Root Growth of Barley in Monoculture

Root system size of spring barley as measured by means of its electrical capacity was evaluated in the 12th till 14th year of monoculture. It was significantly greater in variants with burnt straw in situ or with turned under straw than in variant with straw cleared away. The kind of seed-bed preparation did not influenced root system size significantly, but its interaction with straw utilization and with term of measurement was significant. The larges root sytem was found in combination with minimal seed-bed preparation and burnt straw (relatively 100) and the smallest in combination with minimal seed-bed preparation and straw cleared away (relatively 62).     

Effects of minimal temperatures on low-linolenic rapeseed oil fatty-acid composition

Rapeseed oil is rich in alpha-linolenic acid (C18:3) and has a low content in saturated fatty acids. It is therefore considered as a very healthy edible oil. However, its high polyunsaturated fatty acid content makes it sensitive to temperature oxidation and therefore not suitable for deep-frying. Low-linolenic varieties with C18:3 content lower than 3.5% have been bred, but a large variability of alpha-linolenic acid content has been often observed in agricultural production of these new lines. Identifying factors affecting the fatty acid profile of oilseed rape should make it possible to produce rapeseed with alpha-linolenic acid content lower than 2.5% and therefore more suitable for frying and other uses in the food industry.Fatty acid composition is affected by environmental conditions, temperature being the main factor. Previous works showed that for conventional double-low rapeseed varieties, low minimal temperatures during the 60 days following the onset of flowering were related to higher alpha-linolenic acid contents.Monitoring the fatty acid profile in low-linolenic varieties from the beginning of seed filling to full maturity showed that alpha-linolenic acid synthesis occurred mainly between 550 and 850 degree-days (base 0 °C) after the onset of flowering, that is during the 20 first days of seed filling in Swiss conditions, i.e. 41–60 days after the onset of flowering. During this period, the determination coefficient of a second order regression between final alpha-linolenic acid (C18:3) content and minimal daily temperature was even better, with R² = 0.87. A significant positive relation was also found for the regression between minimal temperature and oleic acid (C18:1) content for the cultivar Splendor (R² = 0.77) but no correlation could evidence a relation between temperature and linoleic acid (C18:2) content.An easier way to show the relationship between linolenic acid content and minimal temperatures is based on the assumption that fatty acid desaturases regulated by temperature are active at low temperatures only. It consists in counting how many times during this period daily minimal temperature reaches a minimal threshold temperature of 13 °C. The relationship between final alpha-linolenic acid content and the number of days with minimal temperature below 13 °C is as good as the one presented before, i.e. with a determination coefficient, R² = 0.85. This simple model could be used to determine the growing areas with low linolenic acid content.     

峨嵋双蝴蝶提取物抑菌作用的研究

为解决峨眉双蝴蝶抑菌作用原理问题,运用滤纸片扩散法研究峨嵋双蝴蝶提取物对致病菌的抑菌作用。结果表明：峨嵋双蝴蝶提取物对金黄色葡萄球菌的抑制作用较强。不同方法提取的提取物中水提取物的抑菌效果最好。峨嵋双蝴蝶提取物对金黄色葡萄球菌的最低抑菌浓度(MIC)为3.125%。与青霉素溶液标准曲线对照,测得峨嵋双蝴蝶提取物的抑菌效价相当于0.77 U/mL,即61.72 U/mg。     

Minimal Periodic Solutions of SuperquadraticFirst Order Convex Hamiltonian Systems

This paper generalizes all known results on Rabinowitz's minimal periodic solution conjecture under the assumption that Hamiltonian function is C2 strictly convex.     

半夏乙醇提取物体外抑菌实验的初步研究

探讨半夏乙醇提取物对常见微生物（细菌、酵母菌、霉菌）的抑菌效果,以得出抑菌谱。分别用75%、95%乙醇对生半夏进行回流提取并用琼脂扩散法和液体混合法测定了半夏提取液对一系列供试细菌和真菌的最低抑菌浓度（MIC）。75%乙醇提取半夏的提取率为5.24%,而95%乙醇提取半夏的提取率为2.73%;75%乙醇半夏提取液对供试细菌和真菌存在一定的抑制作用,对各种菌的最低抑菌浓度分别为：大肠杆菌25 mg/mL,恶臭假单胞菌12.5 mg/mL,藤黄微球菌12.5 mg/mL,金黄色葡萄球菌12.5 mg/mL,枯草芽孢杆菌10 mg/mL,酿酒酵母10 mg/mL,裂殖酵母20 mg/mL,黑曲霉菌12.5 mg/mL,甜瓜枯萎霉菌25 mg/mL。半夏醇提液具有广谱的抗菌活性,可以有效的抑制革兰氏阳性和革兰氏阴性菌,对真菌的抑菌作用也有一定的效果。     

THE K-WEAK MINIMAL CUT SET OF NETWORKS AND FAST SEARCHING ALGORITHM

A new concept dafincd as k-weak minimal cut set, which, is used to characterize the weakness of the weak link set, is established in this paper. Based on this concept, a fast algcrithm or searching k-weak minimal cut set in large scale networks is proposed. From the analysis of computation complexity, it is shown that the frequency count of the algorithm is much lower and the algorithm is powerful to adequacy evaluation of the transmission capacity in large scale networks.     

用核基质结合区(SAR)序列提高小麦最小表达框转基因表达的稳定性

采用最小表达框技术转化植物可以规避由骨架序列引起的安全风险。核基质结合区序列SAR (scaffold attachment region)可作为边界元件与核基质结合阻挡转基因片段邻近染色质区的作用与影响, 提高外源基因稳定性。本研究在最小表达框序列两端添加SAR序列, 提高小麦最小表达框转基因表达的稳定性, 提高转化基因的表达效率。首先, 以GUS为目的基因构建带有SAR序列的最小表达框, 以科农199为受体进行基因枪转化, 同时以不加SAR序列的最小表达框片段为对照。带有SAR序列的最小表达框片段共轰击857个幼胚, T₀代获得40株再生植株, PCR检测到16株阳性植株, 转化效率为1.87%; 对这16个阳性单株进行GUS染色, 15株显色; 从来自4个T₀阳性植株的18个T₁代植株中随机选取18株进行PCR和GUS染色检测, 有15株表现为阳性。不带SAR序列的对照片段轰击1012个幼胚, 获得31株再生植株, 其中5株PCR阳性, 转化效率0.49%, 这5个阳性植株中仅2株为GUS染色阳性; 来自于5个T₀代PCR阳性株系的10个T₁代单株中没有发现PCR和GUS染色阳性株。表明SAR序列可以提高基因枪转基因效率和目的基因表达稳定性。为了创制抗旱转基因小麦, 以来自大豆的抗旱相关转录因子基因GmDREB3为目的基因, Bar基因为筛选标记基因, 转化受体小麦济麦22, 共轰击6045个幼胚, 获得再生植株130株, PCR检测阳性植株30株, 转化效率为0.50%; 随机选取6株PCR阳性植株进行RT-PCR分析, 其中5株可检测到外源基因的转录。进一步对这5株RT-PCR阳性植株插入片段完整性进行分析, 其中4株插入片段基本完整。通过real-time PCR分析, 发现T₀代6个RT-PCR阳性植株的外源GmDREB3的拷贝数为1~3个。以上结果证明, 在最小表达框两端加上SAR序列后可以提高小麦最小表达框转基因表达的稳定性。     

鼠尾藻多酚提取纯化及其抗菌活性研究

为了获得具有抗菌活性的天然海洋生物活性物质,利用褐藻门马尾藻属的鼠尾藻(Sargassum thunbeergiiKuntze)乙醇提取物,通过对靶菌Escherichia coli,Pseudomonas aeruginosa,Bacillus subtilis,Staphylococcus aureus,Botrytis cinerea和Penicillium expansum的抑制率来评价其抗菌活性。结果表明,鼠尾藻提取物有很强的抗细菌和抗真菌活性,抑制Escherichia coli,Pseudomonas aeruginosa,Bacillus subtilis和Staphylococcus aureus生长的最小抑菌浓度(MIC)为5￣12mg·mL-1,抑制Botrytis cinerea和Penicillium expansum真菌生长的MIC为12￣16mg·mL-1。采用10mg·mL-1的多酚处理草莓,其发病率和病斑直径分别比对照低28.4%和47.6%。     

Bi-level Programming Model and Genetic Algorithms for the Selection of Vendors

The traditional vendor selection model often pay attention to the profit of the buyers and the selection behavior of vendor is ignored,but the vendors only trade with the buyers according with their rational selection,so the vendors selection bi-level programming model is presented with constraint of minimal batches,the ability of supply,product matching etc.A solution of the model based on genetic algorithm is proposed.The buyers' vendor selection of minimum cost is realized in the upper programming and the allocation of requirements is proposed in the lower programming.The application of the model and its algorithm are illustrated with a practical example.     

Potential of Azolla pinnata R. Br. green manure for boosting soil fertility and yield of terrestrial crops in Uganda: a case study of Eleusine coracana (L.) Gaertn

Journal of Crop Science and Biotechnology - Azolla fern has traditionally been used over centuries as a source of nutrients for rice grown in paddies with minimal attention on crops grown...     

Effects of Stitcing on the Buckling Strength of Stitched Composite Laminates

A theoretic model is proposed based on the mechanism of the buckling failure of the stitched composite laminates containing delaminations. The buckling strength of the stitched composite laminates under the in-plane compressive load is predicted. The critical percentage elongation of the stitching thread is taken into account as a control parameter of the buckling failure. The energy method is used to calculate the buckling strength of the stitched composite laminates, and the minimal potential energy is used to calculate that of the unstitched composite laminates. The result shows that the buckling strength of the stitched composite laminates is larger than that of the unstitched composite laminates. The effects of stitching technical parameters such as the stitch thread diameter, stitch step and stitch space on the stitched composite laminates are also analyzed.     

The Similar dual of a Subnormal Operator

The problems of similar dual of subuormal operators are discussed.The symmetry of similar dual of the pure subnormal operator are proved and necessary and sufficient conditions that the similar pure subnonmal operatorha similar minimal normal extention are given and meanwhile the subnormal weighted shift of operators also discussed.     

Prospects for ecological intensification of Australian agriculture

World population growth, changing diets and limited opportunities to expand agricultural lands will drive agricultural intensification in the decades ahead. Concerns about the reliance of past agricultural intensification on non-renewable resources, about its negative impacts on natural resources both on and off farm and on greenhouse gas emissions, provide an imperative for future agricultural intensification to become ecologically efficient. We define ecological intensification of agriculture (EIA) as: producing more food per unit resource use while minimising the impact of food production on the environment. Achieving it will require increased precision in the use of inputs and reduction in inefficiencies and losses. It will also require a more holistic view of farming, going beyond efficiencies of single inputs into a single field in a single season to consideration of efficiencies of whole systems over decades. This paper explores the ecological intensification issues facing agricultural production in Australia where opportunities for agricultural intensification are centred on more efficient use of limited and unreliable water resources in both dryland and irrigated agriculture. Ecological efficiencies can be achieved by better matching the supply of nutrients to crops’ requirements both temporally and spatially. This has the added benefit of minimising the opportunities for excessive nutrients to impact on soil health (acidity and dryland salinity) and water quality (pollution of groundwater and eutrophication of lakes and rivers). Opportunities for ecologically efficient intensification are also identified through better integration of crop and livestock enterprises on mixed crop–livestock farms. We define nine desirable attributes of an EIA system: (1) increased agricultural production; (2) efficient use of limited resources; (3) minimal impact on global warming; (4) minimal negative on-site impacts; (5) minimal negative off-site impacts; (6) minimal risk and maximum resilience; (7) preservation of biodiversity in agriculture; (8) preservation of biodiversity in nature and; (9) positive social outcomes. We focus on four technologies and production systems emerging in Australian agriculture: climate risk management; precision agriculture; crop–livestock integration and deficit irrigation. For each of these systems we identify how well they are likely to match the nine desirable attributes of an EIA system. While it seems unlikely that any single technology can satisfy all nine desirable attributes, there is hope that in combination emerging and future technologies will progress Australian agriculture towards greater productivity and ecological efficiency.     

THE MINIMAL PERIODIC SOLUTIONS OF SYMMETRICAL AUTONOMOUS SUBQUADRATIC CONSERVATIVE SYSTEMS

The existence of the minimal periodic solutions of the non-constant of a class of symmetrical autonomous subquadratic second order Hamiltonian systems is studied with minimization.     

Influence of growing periods on the quality of baby spinach leaves at harvest and during storage as minimally processed produce

The influence of different growing periods on quality and decay of fresh-cut baby spinach leaves during chilling storage was assessed. Three different spinach crops were sown on October, December and January, respectively. On January–March the vegetable leaves were harvested, analysed for nitrate, oxalate, vitamin C and chlorophyll content and, after the minimal processing operations, the leaves were packaged and stored at 5 °C. During storage, respiration rate, microbiological quality, dry matter, chlorophyll content and colour parameters were monitored. The results show that for all harvests, the initial quality of leaves was acceptable, although slight changes may be due to variability in climatic conditions.     

An Alternative View of the Convergence Issue of Growth Empirics

In this paper, we study the dynamics of economic growth for 140 countries during the period 1951–2003. The variables representing economic performance are levels and growth rates of per capita gross domestic product. Using the concept of economic regime, we introduce a notion of distance between the dynamical paths of different countries. Then, a minimal spanning tree and a hierarchical tree are constructed from time series to help detect the existence of groups of countries sharing similar economic performance. The two main clusters that are identified over the whole‐time interval can be interpreted as two groups of countries with high and low performance, respectively. The evolution of such clusters shows three main stylised facts: Certain countries move across clusters; the high‐performance cluster tends to span, while the low‐performance one tends to be (more) compact; and the distance between the two groups increases in time.