赤霉酸降解菌的筛选及其适宜降解条件的确定

[目的]筛选一株赤霉酸(GA3)降解菌并探讨其适宜的降解条件。[方法]利用仅含赤霉酸为唯一碳源的基础盐培养基,对前期驯化得到的对GA3具有较强耐受性的微生物进行筛选,获得了具有较强降解GA3能力的菌株G-6;采用单因素试验系统考察了不同因素对菌株G-6降解GA3效果的影响,确定了其适宜的降解条件。[结果]在培养时间为120 h、培养温度为30℃、初始pH为7.0、接种量(菌悬液OD600=1.000)为5.0%(V/V)、培养基中赤霉酸浓度为200 mg/L、摇床转速为140 r/min、250 ml锥形瓶培养基装量为40 ml的条件下,GA3降解率达到60.62%。[结论]为深入探讨GA3的生物降解途径提供了参考。     

中国东北粮食安全评价及政策模拟

系统评价东北地区粮食生产能力,阐释其作为粮食主产区对国家粮食安全的保障能力。通过对粮食供给、结构以及耕地压力的研究,得出结论东北地区保障国家粮食安全能力增强且增产潜力较大,但基于消费结构视角,粮食种植结构面临调整压力;近25年来最小人均耕地面积与耕地压力指数均下降1/2,现有单产水平下的耕地资源能够对国家粮食安全提供有效保障。此外,基于粮食生产能力评价角度选取相应情景,应用系统动力学模型模拟2010-2030年粮食产出状况,根据模拟结果,提出粮食总量安全与结构安全的相关建议。     

Chemical conversions of salvianolic acid B by decoction in aqueous solution

Salvianolic acid B (Sal B) is the most abundant phenolic compound in Salvia miltiorrhiza, which has been widely used for the treatment of cardiovascular diseases in Oriental medicine. To elucidate structure of the converted compounds of Sal B by decoction in aqueous solution, Sal B (200mg) was decocted in an aqueous solution (200mL) at pH 4.9 and the decocted solution was purified by Sephadex LH-20 column chromatography and preparative HPLC. The 13 converted compounds were isolated and the chemical structures were determined by NMR and MS. In addition to the 4 compounds previously reported as conversion products of Sal B by decoction, 9 compounds were first reported with the complete structure of compounds isolated from decocted Sal B solution and three of the compounds were determined to be novel compounds. In addition, a conversion mechanism of compounds converted by decoction was proposed on the basis of kinetics studies, which reasonably supported the conversion mechanism of Sal B. The 13 compounds seemed to be produced by the hydrolysis of an ester bond, decarboxylation, retro oxa-Michael reaction, hydration, and radical reaction during decoction in aqueous solution.     

Biomass carbon pools of Cunninghamia lanceolata (Lamb.) Hook. forests in subtropical China: Characteristics and potential

Abstract

Swedish forestry has successfully developed systems for sustained yield production of wood. Silvicultural techniques are today completely dominated (96%) by clear-felling methods. By contrast, Swedish natural forests and preindustrial cultural woodlands were ecologically and culturally diverse, with a substantial proportion having a continuous tree cover as a response to natural disturbance dynamics and preindustrial agricultural land management. If forest management systems do not mimic this diversity of disturbance regimes sufficiently well, the scope of sustainable forest management to include biodiversity and sociocultural values will not be met. This study estimated the past and present amount of one cultural and two natural disturbance regimes known to deliver continuous tree cover in two study areas located around two important biophysical and sociocultural transition zones in northern and southern Sweden, respectively. Several approaches were used to estimate the amount of remaining continuous tree cover forests. The results indicate that 9–10% of the study areas is made up by site types that historically would have held a large proportion of continuous tree cover forests. Estimates for productive site types show that only 1–2% of these sites remain in southern Sweden and 10–20% in northern Sweden. The data indicate that present management in both study areas is similar. Thus, these differences between the regions will disappear in a few decades. To achieve the aim of Swedish forest and environmental policies there is a clear need to develop and use alternative forest management methods on appropriate sites.     

Physiological basis of wood production: A review

The theoretical background to wood production is outlined and the factual background is given by reviewing measured rates of wood production. It is recommended that differences in wood production be analysed, not by statistical methods, traditional growth analysis or by comprehensive models, but by using a ‘light use analysis’, where wood production is determined by (1) the amount of light intercepted by the canopy, (2) the light use efficiency, net of respiration, (3) the proportion of assimilates partitioned to wood, and (4) mortality losses. These four components are discussed.     

纳米TiO2/丝素蛋白多孔膜的体外降解性能

为改善丝素蛋白膜的生物活性功能,通过冷冻干燥的方法制备了纳米TiO2/丝素蛋白多孔膜,并在人体模拟体液(simulated body fluid,SBF)中进行了体外降解试验。测试结果表明:纳米TiO2/丝素蛋白多孔膜具有较好的平均孔径和孔隙率,分别为22~53μm和86%~92%;降解20 d后,孔洞界限逐渐被破坏,复合多孔膜的失重率增大到35%以上;降解后多孔膜的结晶度有大于降解前的趋势;在多孔膜的内壁有羟基磷灰石的生成,具有很好的生物活性。据此认为,采用冷冻干燥法制备的纳米TiO2/丝素蛋白多孔膜,有望进一步开发成为软骨替代材料或创面涂敷材料。     

复合酶降解玉米秸秆工艺条件的研究

[目的]为了寻找玉米秸秆酶解的最佳工艺条件。[方法]采用5因素3水平的正交试验,利用复合酶进行玉米秸秆的酶解,研究降解玉米秸秆的最佳工艺条件,并利用扫描电镜观察秸秆在降解过程的形态结构变化。[结果]影响该复合酶降解玉米秸秆的因素为:pH值>底物浓度>反应时间>酶用量>反应温度。该复合酶降解玉米秸秆的最佳工艺条件为:酶用量0.20%,底物浓度5.0%,反应时间3.0 h,反应温度50℃,pH值5.0。此时,降解率最高(达27.6%)。电镜观察表明:玉米秸秆经酶解作用后表面蜡质结构被降解,内部的致密结构变得松散,出现空洞。[结论]该研究为玉米秸秆的生物利用提供了参考依据。     

动态调整粒子群-霍尔特模型在径流预测中的应用

为了提高水库和河流中长期径流预测精度,针对粒子群算法存在的缺陷,提出了动态调整粒子群算法（DAPSO）。借助霍尔特-温特斯线性季节性模型的预测功能,应用DAPSO算法求解和优化霍尔特-温特斯线性季节性模型组合参数,形成动态调整粒子群-霍尔特-温特斯线性季节性模型组合算法,对石泉水库进行中长期径流预测。仿真计算表明,动态调整粒子群-霍尔特-温特斯线性季节性模型算法收敛速度快于霍尔特-温特斯线性季节性模型算法、粒子群-霍尔特-温特斯线性季节性模型算法。该组合算法克服了按梯度试算法搜索质量差和精度不高的缺点,输出稳定性好,预报精度显著提高,置信度为95%时的预测相对误差小于6%。该算法可应用于水库和河川中长期径流预测。     

多级离心泵轴向力平衡装置的设计与分析

可靠的轴向力平衡装置是高压多级离心泵实现平稳可靠运行的重要机构。针对反渗透海水淡化高压泵对结构和运行可靠性的特殊要求,设计了一种用于节段式多级离心泵的新型轴向力平衡装置。基于计算流体力学（CFD）方法研究了平衡装置内部的流场结构及其轴向力平衡机理,分析了不同轴向间隙、径向间隙以及滑动轴承长径比条件下的轴向力平衡特性。结果表明,不同进出口压差条件下,滑动轴承间隙内流动结构存在明显区别,轴承支撑机理发生变化;平衡力和相对泄漏量随轴向、径向间隙的增大呈非线性增大,平衡力随长径比增大近似呈线性增大,相对泄漏量随长径比增大近似呈线性减小。对径向、轴向间隙和长径比进行各种组合分析计算,得到轴向间隙0.2 mm、径向间隙0.3 mm、长径比为1的结构优化的新型机构,该机构既可以很好地平衡轴向力,又提高了多级泵的可靠性。