冷链物流过程中温度和时间对冰鲜带鱼品质的影响

为了解冷链物流过程中水产品品质与温度-时间的关联性,该文以冰鲜带鱼为研究对象,对其冷链物流过程进行模拟试验,对冷链物流各环节温度进行实时监测,并对冰鲜带鱼物流过程中冰的融化情况进行考察。同时通过感官评分、K值、细菌总数、肠杆菌数、挥发性盐基氮（total volatile basic nitrogen, TVB-N）、三甲胺氮（trimethylamine nitrogen, TMA-N）、pH值及硫代巴比妥酸值（2-thiobarbituric acid,TBA）的检测,研究了冷链物流各环节冰鲜带鱼品质变化。结果表明,在20℃冷链断链流通条件下经搬运2 h及运输24 h后,泡沫箱内的碎冰融化较快,其融化成水的平均速度为56.54 mL/h,冰融化的体积约占总体积的25.79%;由于冰水浸泡,冰鲜带鱼感官品质下降较明显,腹部出现破裂,微生物数量急剧上升,达到5.64 lg (CFU/g),约是同期2℃冷链流通组带鱼的13倍。由于模拟冷链物流过程中的搬运、运输、配送3个环节的断链是在20℃环境下,断链流通中的冰鲜带鱼K值、TVB-N、TMA-N等反映带鱼新鲜程度的理化指标均高于同期2℃冷链流通下的带鱼,且在随后4℃铺冰上销售的货架期比2℃冷链流通带鱼短2～3 d。     

植物叶面积无损测量方法及仪器开发

为了快速、无损、准确地测量植物叶面积,设计了一种利用多晶硅光电感应板与平板均匀发光光源照射系统构成的叶面积测量装置。通过试验,建立了植物叶片叶面积与光源光强、光源对叶片透射率、环境温度、光电感应板的光电感应电压值间的BP神经网络关系。结果表明：该仪器可测量不同形状、厚度、软硬程度、叶片大小的植物叶片面积,模型预测值与实际值决定系数R2为0.98,测量精度为94.8%,为叶片叶面积测量提供了一种新的测量方法和装置。     

基于卡尔曼滤波的车辆侧偏角软测量

针对车辆稳定性控制过程中难以在线测得车辆侧偏角的问题,该文基于参数软测量理论和离散信号滤波理论,并结合卡尔曼滤波和驾驶员—车辆闭环系统模型建立车辆侧偏角软测量模型。该方法通过易测变量横摆角速度和侧向加速度估算车辆侧偏角,以实现车辆侧偏角的状态估计。基于预瞄最优曲率控制理论和预测—跟随理论所建立的二自由度驾驶员—车辆闭环系统建立了软测量模型,并建立其状态方程和观测方程。为进行状态估计,对模型的状态方程和观测方程进行连续系统离散化,得到以横摆角速度和侧向加速度为观测量的系统离散观测方程。通过双移线试验与蛇形试验进行场地试验获取纵向速度、侧向速度、横摆角速度、侧向加速度及车辆侧偏角等试验数据。估计值和试验值比较显示,两者变化趋势一致,误差均值在试验值幅值的10%以内,试验表明,软测量算法能准确估算出车辆侧偏角是可行的。研究结果可为软测量技术在车辆稳定性控制系统上的应用提供参考。     

成都─西北蔬菜安全运输气象条件及其用冰量模式分析

通过大量的蔬菜运输个例的气象条件分析，建立了成都—西北蔬菜运输的用冰量物理模型，并进行了理论分析和个例计算，得到蔬菜运输的气象条件，及满足气象条件的蔬菜安全运输的用冰量计算模式的研究结果，具有一定的理论和实际应用价值。     

成都—西北蔬菜安全运输气象条件及其用冰量模式分析

通过大量的蔬菜运输个例的气象条件分析，建立了成都－西北蔬菜运输的用冰量物理模型，并进行了理论分析和个例计算，得到蔬菜运输的气象条件，及满足气象条件的蔬菜安全运输的用冰量计算模式的研究结果，具有一定的理论和实际应用价值。     

云南省Ångström-prescott辐射模型的参数化研究

现行的太阳辐射通常采用常规数据进行估算。其中,基于日照的ngstrm-prescott公式的估算精度最高、应用最广。但模型应用的关键是如何获得适宜的模型参数。该文采用FAO和Liu等推荐的6种参数化方法,在云南省3个站点应用ngstrm-prescott公式计算太阳辐射值,并与实测值进行比较。结果表明,Liu等的2种方法太阳辐射值的估算效果最好,精度与校正参数相当。二者在昆明和丽江的平均偏差(MBE)、均方根误差(RMSE)及相对均方根误差(PRMSE)分别在-0.28～0.50、2.09～2.39MJ/(m2·d)及12.4%～15.8%之间。相比之下,FAO推荐值在这两地点预测的MBE、RMSE及PRMSE分别为-0.43～0.84、2.61～5.37MJ/(m2·d)及17.2%～31.7%,估算精度远低于前两种参数化方法。鉴于目前国内直接使用FAO推荐值的做法还相当普遍,该文结果有助于加深人们对ngstrm-prescott模型参数选择的重要性的认识,进而实际应用中更多地使用校正值或估算值。     

养殖鱼类货架期预测系统的设计与评估

以自然污染养殖罗非鱼贮藏在0℃、5℃、10℃、15℃过程中的特定腐败菌-假单胞菌生长动态数据,建立假单胞菌在0～15℃温度范围的生长动力学模型,选用Visual Basic为程序编写工具,建立了用于罗非鱼冷却链鲜品流通品质监控和剩余货架期预测的专家系统(FSLP)。剩余货架期预测值与实测值的可靠性评估表明,相对误差在±10%以内,显示建立的预测系统可以快速可靠地实时预测养殖罗非鱼的鲜度和剩余货架期。该研究采用以自然污染鱼得到试验数据建立特定腐败菌生长动力学模型的方法,增加了预测的准确度,并较好地解决了在波动温度下预测微生物生长相对困难的难题,提高了预报系统的实际应用价值。该预测系统为设计和评估生鲜鱼品冷却链的技术参数,预测和监控冷却链生鲜鱼的鲜度品质提供一种迅速而有效的工具。     

基于改进卡尔曼滤波算法的雷达定量降雨估算

针对雷达定量降雨估算误差较大的问题,本文提出一种使用改进卡尔曼滤波对雷达估算值进行校准的方法。先确立G/R(自动气象站测量值/天气雷达估算值)校准因子模型,并应用普通卡尔曼滤波方法对G/R校准因子建立预测系统和测量系统,同时引入系统参数的校准过程和系统误差的自适应估计过程,动态调整卡尔曼滤波中各项参数值;最后将滤波后的G/R因子用于校正雷达定量降雨估算,得到较准确的降雨估算值。利用长春市天气雷达2015年8月19-20日和2016年月8月6-7日两次降雨过程的雷达产品和加密自动站逐小时的降雨资料,对卡尔曼滤波方法进行检验分析。结果表明:改进卡尔曼滤波和普通卡尔曼滤波校准后雷达降雨估算结果优于未校准的降雨估算结果,普通卡尔曼滤波方法和改进卡尔曼滤波方法的平均相对误差分别从0.6047减至0.3557和0.2645,从0.8052减至0.3096和0.1715,且改进算法效果优于普通卡尔曼滤波算法,校准后雷达降雨估算准确度明显提高。     

饮用水源区小流域氮素污染负荷估算方法比较

采用输出系数法、通用土壤流失方程估算法、径流试验场法和相关关系法4种方法对密云土门西沟小流域非点源氮污染负荷进行估算。结果表明：输出系数法中的Johnes模型和考虑降雨影响的输出系数模型计算值相对误差比较大,考虑流域损失的输出系数模型计算结果与实测结果相对误差仅为5%;输出系数方法适用于资料比较缺乏的地区,输出系数的确定是提高估算精度的关键。对流域非点源污染发生类型区和类型单元进行详细划分,并将对各类型采用径流试验场法的监测结果推算到小流域就能减小估算相对误差;采用径流试验场法推算密云土门西沟小流域非点源氮污染负荷相对误差仅为8%;相关关系法通过建立降雨和污染负荷的关系,其估算值相对误差达到4%,此方法需要长期的降雨-水质监测数据;通用土壤流失方程估算法主要估算流域土壤侵蚀量,没有考虑径流对污染物输移过程中的沉积、起动和交换等问题,估算值会偏大。     

全国农作物叶面积指数遥感估算方法

目前对农作物叶面积指数LAI的遥感估算研究多是针对单一作物或是作物种植结构单一的区域,该文运用大尺度农作物叶面积指数的遥感估算方法,在像元尺度上对4个代表性实验站的LAI与归一化植被指数(NDVI)的相互关系进行了回归分析后,得到4种代表性作物种植结构的LAI估算模型,然后结合全国农作物种植结构数据对模型外推,建立了一个全国尺度的遥感模型,并估算了全国作物LAI。该文使用“863”项目山东遥感应用综合试验中的作物LAI观测数据进行了验证,结果表明该模型较其它估算模型达到了较高的精度,最大相对误差为39%,平均的相对误差为19%。该模型的计算结果已经在“中国农情遥感速报”系统中得到了广泛的应用。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.