L-半胱氨酸处理对采后青脆李果实苯丙烷代谢的影响

L-半胱氨酸(L-cysteine)作为生物体中的常见氨基酸,已有研究发现其能有效延缓青脆李果实的衰老和品质的下降。然而,L-半胱氨酸处理对李果实中苯丙烷代谢途径合成酚类物质的影响尚不清楚。因此,该研究以青脆李果实为试材,采用1 g/L L-半胱氨酸浸泡处理后于(20±1)℃贮藏,研究贮藏期间苯丙烷代谢途径中关键酶活性以及总酚、总黄酮等相关代谢产物的变化规律,同时测定果实中糖酸含量和抗氧化活性的变化。结果表明,李果实在贮藏过程中可溶性固形物(Total soluble solids,TSS)含量和可滴定酸(Titratable acid,TA)呈逐渐降低的趋势,L-半胱氨酸处理显著延缓了李果实TSS和TA的下降(P0.05)。在贮藏期间,苯丙烷代谢途径中关键酶活性均呈逐渐上升的趋势,与对照组相比,处理组中苯丙氨酸解氨酶、4-香豆酸辅酶A连接酶活性更高。果实中总酚、总黄酮含量在贮藏期间先降低后上升,在贮藏前三天,处理组中总酚、总黄酮含量显著高于对照组(P0.05)。对酚类物质单体含量的测定发现,处理后的果实中绿原酸、咖啡酸、丁香酸、芦丁等酚类物质单体含量显著高于对照组(P0.05)。抗氧化活性与总酚、总黄酮的变化趋势一致,经L-半胱氨酸处理后的果实保持了较高的抗氧化活性。相关性分析结果表明,果实中苯丙氨酸解氨酶、肉桂酸-4-羟基化酶和4-香豆酸辅酶A连接酶与果实酚类物质含量及抗氧化活性显著相关(P0.05)。总体来说,1 g/L L-半胱氨酸浸泡处理能够延缓青脆李果实贮藏品质下降,同时能够激活苯丙烷代谢途径关键酶,促进果实中酚类物质的积累。     

一种小量程适用型传感器的设计

对耕作土壤和农业物料的物理机械性质进行测试和研究,找出其内在联系和规律,能够为设计新的农机具和合理配置机组提供较为完整可靠的依据。为此,针对农机实验的特殊情况,设计了一种小量程适用型压力传感器,以满足某些物理量的动态测试和零部件的强度分析。经理论设计计算和静态特性实验,该传感器具有结构简单、使用方便,工作可靠的特点,且具有足够的精度和灵敏度,各项性能指标均能满足使用要求。     

The effect of peatland drainage and rewetting (ditch blocking) on extracellular enzyme activities and water chemistry

Extensive areas of European peatlands have been drained by digging ditches in an attempt to improve the land, resulting in increased carbon dioxide fluxes to the atmosphere and enhanced fluvial dissolved organic carbon (DOC) concentrations. Numerous peatland restoration projects have been initiated which aim to raise water tables by ditch blocking, thus reversing drainage‐induced carbon losses. It has been suggested that extracellular hydrolase and phenol oxidase enzymes are partly responsible for controlling peatland carbon dynamics and that these enzymes are affected by environmental change. The aim of this study was to investigate how drainage and ditch blocking affect enzyme activities and water chemistry in a Welsh blanket bog, and to study the relationship between enzyme activity and water chemistry. A comparison of a drained and undrained site showed that the drained site had higher phenol oxidase and hydrolase activities, and lower concentrations of phenolic compounds which inhibit hydrolase enzymes. Ditch blocking had little impact upon enzyme activities; although hydrolase activities were lowered 4–9 months after restoration, the only significant difference was for arylsulphatase. Finally, we noted a negative correlation between β‐glucosidase activity and DOC concentrations, and a positive correlation between arylsulphatase activity and sulphate concentration. Phenol oxidase activity was negatively correlated with DOC concentrations in pore water, but for ditch water phenol oxidase correlated negatively with the ratio of phenolics to DOC. Our results imply that drainage could exacerbate gaseous and fluvial carbon losses and that peatland restoration may not reverse the effects, at least in the short term.     

城市配网排管敷设三芯10kV电缆的温度场数值计算

研究了如何确定离散时间情况下再保险模型破产概率上界的问题.为了降低自身的破产风险,保险公司常常对部分乃至全部资产进行再保险.假定索赔间隔时间和索赔额具有一阶自回归结构,假定利率过程为取值于可数状态空间的Markov链.建立了其比例再保险模型,分别用递归更新技巧和鞅方法得到模型的破产概率上界.该破产概率上界作为评估再保险公司偿付能力和风险控制能力的重要指标,对于它的研究成果能为再保险人做出重大决策提供重要的依据,具有较为重要的理论和现实意义.     

Biochemical diversity in wild and cultivated pomegranate (Punica granatum L.) in Pakistan

The present study was conducted to screen out elite pomegranates through determination of biochemical diversity in wild and cultivated genotypes for a breeding program and for fresh/processed use in industry. The results showed high morphological diversity in accessions of wild pomegranate fruits as compared to cultivated genotypes. The first six principal components covered 80.75 and 75.49% diversity in 53 wild and 62 cultivated pomegranate genotypes, respectively. High values of the coefficient of variance (10.78–18.62%), and a high range of minimum to maximum values of total soluble solids, titratable acidity, ascorbic acid content, total soluble sugars, and total phenolic content (0.10–1.25, 5.88–29.96, 9.69–19.85 and 175.05–595.42), respectively, were recorded in the studied genotypes. Ascorbic acid content had a strong correlation with antioxidant activity (0.952%), super dismutase oxides (0.94%), catalase (0.921%), and titratable acidity (0.91%). Peroxides had a strong correlation (0.88%) with catalase, and 0.81% each with super dismutase oxides and antioxidant activity. Wild and cultivated pomegranates were clustered successfully in separate groups, based on biochemical traits. A variety improvement program and selection of high-quality pomegranate genotypes could help to reduce pomegranate-related malnutrition issues in the human diet.     

Total Phenolics Content,Antioxidant Capacity,Physicochemical Attributes,and Browning Susceptibility of Different Apple Cultivars for Minimal Processing

The total phenolics content, browning susceptibility, antioxidant capacity, and other physicochemical attributes of five cultivars of apple with different chilling hours requirements were studied to be minimally processed. Granny Smith (GS) and Red Delicious (RD) cultivars (high chill requirement), and Caricia (C), Eva (E), and Princesa (P) cultivars (low chill requirement) were studied. The flesh color, firmness, juiciness, pH, acidity, soluble solids, and flesh browning development, and total phenolics content and antioxidant capacity in flesh and peel were determined. All attributes were significantly different (p ≤ 0.001) among cultivars. RD showed the highest values of soluble solids and pH, and GS, the lowest. GS and P had the highest values of firmness and juiciness. GS, P, and E showed the lowest browning development. RD had the highest phenol content in flesh, followed by E and C. Phenolic content in peel was 2–5 times higher than in flesh for all varieties. The antioxidant capacity of RD flesh was higher than the other four apple cultivars. The antioxidant capacity of the apple peel was 2–4 times higher than the flesh, being RD the highest, followed by C, GS, and P with 50% less. Considering the lower browning development, and higher values of firmness and juiciness, GS and P would be the most suitable cultivars for minimal processing. If fresh-cut apples are not peeled, GS and P would increase their phenolic content in 28–56% and their antioxidant capacity in 65–78%.     

广义逆A（2）T,S在谱范数下的扰动界

利用广义逆A（2）T,S与Moore—Penrose逆的关系，给出广义逆A慰在谱范数下的扰动界，推广了广义Moore—Penrose逆在谱范数下的一些结果．     

基因专利法律保护相关问题研究

通过对基因的可专利性问题的探讨,阐明了科学发现和科学发明的区别,并结合我国现有专利法对基因专利的法律保护及基因的生物学特点,剖析了基因专利的新颖性、创造性和实用性要求,同时论述了基因专利的保护范围.     

土壤中结合残留农药的研究方法

有机农药或其代谢产物在进入土壤中后，可以与土壤有机质或矿质形成结合残留物。越来越多的证据表明，在涉及农药在土壤环境中归趋的研究中，有必要研究农药的结合残留。本文介绍了研究结合残留农药在土壤有机质中分布的方法及释放结合残留的方法，其中包括水解释放法、高温蒸馏法、超临界流体萃取法、化学释放法和微生物释放法。