An empirical approach to target DNA quantification in environmental samples using real-time polymerase chain reactions

Recent advances in molecular techniques have allowed for the routine examination of nucleic acids in environmental samples. Although current methodologies are very sensitive, accurate target DNA quantification from environmental samples remains challenging. To facilitate high-throughput DNA quantification from environmental samples, we developed a novel DNA quantification method based on a non-linear curve-fitting approach to extract additional information from quantitative PCR amplification curves and used the fitted parameters to develop multiple regression standard equations for target DNA quantification. A 3-parameter sigmoidal function performed superior to a 4-parameter Weibull function for generating the multiple regression standard equations. In a verification experiment, target DNA was quantified in a series of ‘unknown’ samples in three soils using this approach and the results were compared to target DNA values determined using corrected and uncorrected Ct-based (threshold cycle) methods. For each method, the deviations from the expected target DNA content were determined. Results clearly showed that over all DNA concentrations, target DNA content determined by the non-linear curve-fitting method was more accurate and more precise than values predicted by all other methods. Analysis of variance conducted on the predicted DNA contents also revealed fewer statistical artifacts with the non-linear curve fitting method compared to the conventional Ct-based methods. The novel approach described here is accurate, inexpensive, and very amenable for automation and high-throughput applications.     

Optimizing nitrogen management strategy under wheat straw incorporation for higher rice production and nitrogen use efficiency

Nitrogen (N) application plays an important role in rice production. Limited attention has already been paid to optimizing N fertilizer management strategy for higher grain yield and nitrogen use efficiency (NUE) of rice with crop residue incorporation. Field experiments were conducted with the objective to determine the response of several N application methods to rice production and to evaluate their NUE. Three N fertilizer application methods, i.e., local farmers' N fertilizer practice (FNP), modified farmers' N fertilizer practice (MNP), and increased the amount of N fertilizer practice (INP), were adopted with zero N application as control (CK). The results showed that, compared with that under FNP, grain yield was significantly higher under MFP, owing to signficantly enhanced total spikelets as a result of more panicles per unit area. Relative to FNP, MNP markedly increased nitrogen agronomic efficiency (AE_N), nitrogen recovery efficiency (RE_N), nitrogen physiological efficiency (PE_N) and nitrogen partial factor productivity (PFP_N), but AE_N, PE_N and PFP_N of INP were significantly lower. Further analysis showed that the number of tiller, leaf area index, aboveground biomass, SPAD value, plant N content and N uptake at the early vegetative stage were improved significantly under MNP compared to those under FNP, contributing to higher total aboveground biomass and total N uptake.     

ASSESSING LAND DEGRADATION RISK THROUGH THE LONG‐TERM ANALYSIS OF EROSIVITY: A CASE STUDY IN SOUTHERN SPAIN

Despite the high variability of the precipitation regime characterizing the Mediterranean area, the records of rainfall depth are usually not appropriate for long‐term calculations of erosivity and soil losses, because they do not reveal details of short lengths or long durations (daily, monthly). In this work, we present a simple approach to calculate annual erosivity through monthly precipitation records. The study area (olive groves on steep slopes) has a high erosion risk associated to the main soil land use, combined with an irregular and erosive rainfall regime. The relationships between rainfall data at intervals of 10 min for a period of 3 years, daily rainfall records over 10 years and a long‐term monthly dataset of 60 years were checked to calculate the annual erosivity values through daily data, Fourier's index and modified Fourier's index values. A good, adjusted linear relationship between modified Fourier's index and the erosivity was found, which allowed us to optimize the use of the 60‐year monthly data series and to carry out a long‐term analysis of the erosivity quantiles in the study area. The estimated mean erosivity showed a return period of between 2 and 5 years and a variation coefficient of over 50 per cent, which illustrate its high variability and frequency. This approach to calculate erosivity and the use of quantiles could be applied in other areas with month‐long data series in order to study and model the erosion risk using suitable temporal periods. Copyright © 2011 John Wiley & Sons, Ltd.     

自发气调（MA）结合高效乙烯去除剂对黑宝石李贮藏效果的研究

以黑宝石李为试材,研究MA（0．03mm厚PVC保鲜袋包装）结合高效乙烯去除剂对0-1℃条件下黑宝石李果实贮藏效果的影响。结果表明,MA结合高效乙烯去除剂处理的贮藏效果好于单纯MA处理和0．02mm厚PE打孔袋包装处理,贮藏92d时好果率〉90％,果实硬度〉6kg·cm-2,果肉黄绿色,无明显冷害症状,果实失重率〈1．0％,袋内的乙烯浓度〈O．1μL·L-1,O2浓度为9．84％,C02浓度为5．17％,接近黑宝石李标准气调要求的气体指标。     

On C60 Hlgh-performance Concrete of Modified Extra Fine Sand and lts Application

Utilizing the local materials in Chongqing,employing the techniques concrete of modified extra fine sand with three additives, we have conducted a cross experiment design test on multi-factors.ln addition, in combination with the routine production procedures in ready-mixed pumping concrete, C60 high-performance concrete has been produced.Through the practical application in engineering projects,a conclusion canbe drawn that C60 high-performance concrete consisting of modified extra fine sand is of great value in its spreading and popularization.     

Application of CAD Techniques for Design of Packaging Paper Box

CAD techniques were applied to automated design of packaging paper box such as the performance and selection of box pattern, the structure computation, the art design(including sample design, the box sample unfolding and craft drawing), input and edition of Chinese characters and foreign words, and output of the drawings. A packaging paper box system is developed to automate the packaging paper box design processes.     

生菜切块充气贮藏条件的研究

用23种不同的充气条件研究生菜切块的贮藏效果,通过感官质量评价和化学分析,观察颜色的变化、褐变程度及维生素C和叶绿素含量的差异,结果表明,采用O_2 20％+CO_240％+N_2 40％的贮藏条件是比较合适的.在上述条件及5℃的情况下,生菜切块的有效贮藏期大约在12～15d之间,这一结果在商业上有一定的实用价值.     

充氮储藏对大豆老化劣变影响的研究

研究了充氮气调储藏对大豆老化的影响。控制氮气体积分数分别为98%和78%,比较了水分含量,储藏温度和储藏时间对大豆发芽率、浸出液电导率、丙二醛(MDA)含量和过氧化物酶(POD)活性的影响。结果表明,充氮储藏和普通储藏的大豆种子在储藏过程中发芽率会逐渐下降,水分12.2%的大豆在20℃储藏180d时发芽率保持在85%以上,而高温(30℃)高水分(14.9%)储藏大豆储藏至90d时,发芽率已降至零,种子完全丧失活力;充氮储藏的大豆浸出液电导率和丙二醛含量均比普通储藏的对照组大豆低,根据相关性分析,发芽率、电导率、丙二醛(MDA)和过氧化物酶(POD)存在极显著或显著相关性。充氮气调储藏能在一定程度上延缓大豆在储藏过程中的老化。     

国内外果蔬鲜切加工及保鲜技术研究现状

随着工作节奏的加快,方便快捷食品需求的增强,鲜切加工产品越来越受到关注。阐述了鲜切产品的加工过程、原料来源及选择,清洗、去皮、切分、护色、包装和贮藏等各项技术,论述和比较了鲜切产品的保鲜技术包括冷藏保鲜、保鲜剂保鲜、MAP保鲜及冷杀菌保鲜等,分析了加工过程中需要注意的问题,最后对鲜切加工技术的发展提出了展望。     

Estimation of phenotypic variability in symbiotic nitrogen fixation ability of common bean under drought stress using 15N natural abundance in grain

Common bean (Phaseolus vulgaris L.) is the most important food legume, cultivated by small farmers and is usually exposed to unfavorable conditions with minimum use of inputs. Drought and low soil fertility, especially phosphorus and nitrogen (N) deficiencies, are major limitations to bean yield in smallholder systems. Beans can derive part of their required N from the atmosphere through symbiotic nitrogen fixation (SNF). Drought stress severely limits SNF ability of plants. The main objectives of this study were to: (i) test and validate the use of ¹⁵N natural abundance in grain to quantify phenotypic differences in SNF ability for its implementation in breeding programs of common bean with bush growth habit aiming to improve SNF, and (ii) quantify phenotypic differences in SNF under drought to identify superior genotypes that could serve as parents. Field studies were conducted at CIAT-Palmira, Colombia using a set of 36 bean genotypes belonging to the Middle American gene pool for evaluation in two seasons with two levels of water supply (irrigated and drought stress). We used ¹⁵N natural abundance method to compare SNF ability estimated from shoot tissue sampled at mid-pod filling growth stage vs. grain tissue sampled at harvest. Our results showed positive and significant correlation between nitrogen derived from the atmosphere (%Ndfa) estimated using shoot tissue at mid-pod filling and %Ndfa estimated using grain tissue at harvest. Both methods showed phenotypic variability in SNF ability under both drought and irrigated conditions and a significant reduction in SNF ability was observed under drought stress. We suggest that the method of estimating Ndfa using grain tissue (Ndfa-G) could be applied in bean breeding programs to improve SNF ability. Using this method of Ndfa-G, we identified four bean lines (RCB 593, SEA 15, NCB 226 and BFS 29) that combine greater SNF ability with greater grain yield under drought stress and these could serve as potential parents to further improve SNF ability of common bean.