沼气中CO2化学吸收传质性能分析与传质系数建模

以气相总体积传质系数为指标,在乱堆鲍尔环填料吸收塔内研究了乙醇胺(MEA)、二乙醇胺(DEA)、三乙醇胺(TEA)和哌嗪(PZ)4种典型吸收剂对模拟沼气中CO_2的吸收传质性能,考察了吸收剂浓度、吸收剂温度、吸收剂体积流量、CO_2负荷、气体流量与CO_2分压的影响,并建立了MEA、DEA和PZ的气相总体积传质系数的计算经验模型。结果表明,相同吸收剂浓度条件下,PZ具有最优的CO_2传质性能,MEA和DEA次之,TEA最差。随着吸收剂浓度的增加,除TEA外,其他3种吸收剂的气相总体积传质系数均大幅增加,填料塔出口CO_2体积分数大幅下降,且MEA在3.27 mol/L时可获得最高的气相总体积传质系数(1.37 kmol/(m~3·h·k Pa));提升吸收剂体积流量、吸收剂温度、气体流量及降低吸收剂初始CO_2负荷均可有效增加吸收剂的气相总体积传质系数,但CO_2分压变化对气相总体积传质系数影响不显著。最后,建立了MEA、DEA和PZ吸收剂的气相总体积传质系数的计算经验公式,且气相总体积传质系数的试验值与计算值之间的绝对平均误差均小于14%。     

Influence of long-term fertilization with farmyard manure on soil organic matter: Characteristics of particle-size fractions

Summary The influence of more than 100 years of fertilization with farmyard manure on soil organic matter in comparison to unfertilized soil was studied in particle-size fractions using elemental (C and N) analyses and pyrolysis-field ionization mass spectrometry. Distinct differences in C and N concentrations and distribution and in the quality of organic matter between the size fractions and the fertilization treatments were observed. Clay-associated C and N were relatively higher in the unfertilized treatment, whereas the application of farmyard manure preferentially increased soil organic matter associated with the fine and medium silt fractions. Pyrolysis-field ionization mass spectrometry of soil fractions <20 m showed increasing values for lignin monomers and dimers and fatty acids with larger equivalent diameters, whereas the proportion of N compounds, mono- and polysaccharides and phenolics decreased in the larger size fractions. Sand fractions were particularly rich in lignin fragments, mono- and polysaccharides, and alkanes/alkenes. These relationships seemed to be independent of management practices. In the same size fractions of the different treatments, however, a higher relative abundance of N-compounds, mono- and polysaccharides, phenolics, lignin monomers, and alkanes/alkenes was observed in the unfertilized variant. Lignin dimers and fatty acids were more abundant in the farmyard manure treatment. Both trends together imply that soil enrichment in organic matter due to the application of farmyard manure largely reflects an increase in lignin building blocks and partly reflects an increase in lipids such as fatty acids in the silt fractions. Therefore these constituents are of particular importance in assessing the positive effects of farmyard manure on soil fertility.     

球形食品真空冷却过程中参数分析

建立了描述球形食品在真空冷却中传热、传质的数学模型。通过数值求解得到真空压力、产品质量、产品温度(表面温度、中心温度、质量平均温度)随时间的变化曲线。实验装置中高精度的数据采集系统能够在线测定和记录真空室压力、产品质量、产品不同位置的温度随时间的变化。在春收甘蓝的真空冷却实验中，模拟的压力和实测的压力在10000～600 Pa的降压过程中最大相差100 Pa；模拟值和实测值间温度的最大差值小于1℃；真空冷却中，模拟的甘蓝的水分损失率是3.32%，实测的甘蓝水分损失率是2.97%，相差0.35%。研究结果对     

生态输水后塔里木河下游合理水位探讨

塔里木河下游应急生态输水工程改善了该区水资源匮乏的现状,地下水的平均水位从输水前的8.25m升至输水后的4.13m。相应地,地表植被也出现明显的响应。但是,在不同河段由于过水时间、耗水量等因素的差异,造成输水后水位差异较大。以既能减少地下水强烈蒸发返盐,又不造成土壤干旱而影响植物生长的合理生态水位作为评价标准,对输水后不同河段的地下水位进行分析。结果显示,目前英苏—阿拉干段的地下水位2.97～4.8m是比较理想的水位;大西海子—英苏段水位较高,可能出现次生盐渍化;阿拉干—台特玛湖段地下水位太低,不利于植被的自然恢复。     

黄河小浪底水库蓄水前后库周土地覆被变化研究

选取黄河小浪底水库库周1993年和2000年TM遥感影像进行土地覆被变化分析,绘制出蓄水前后的土地利用现状图,计算出土地覆被变化的转移矩阵和景观结构的控制指标,分别从土地利用类型、空间景观结构特征及土地变化过程等方面进行了研究.研究结果表明:小浪底水库的施工和蓄水对库周的土地利用变化和空间景观结构的改变没有太大影响;由于林地向耕地和其它土地覆被类型转变,使得1993～2000年的模地类型由有林地向耕地转化     

硒从土壤向食物链的迁移

硒是生物必需的微量营养元素 ,已经得到公认 ,硒从土壤向食物链的迁移状况直接关系到动物和人的健康。通过食物链 ,动物和人获得适合于健康需求的硒是最为安全和可行的     

水稻多组分双向反射模型的建立

在作物多组分双向反射模型的基础上，基于辐射传输原理和水稻群丛结构特征，特别是考虑水稻不同生长时期的特点，建立了水稻的多组分双向反射模型。模拟与实测结果的比较表明：模型基本上能反映水稻多组分反射光谱的角度分布特征，特别是较准确地模拟水稻不同生长期，不同太阳天顶角下，“热点”的右移和乳熟期前向反射中的反射高峰点。分蘖期和抽穗期，水稻冠层“热点”效应在水稻各组分的平均倾角约37°左右时达到最大，然后随平均倾角的增大，“热点”效应明显减弱。从数学的角度，模型计算值与实测值通过了t-检验，证明模拟值是可接受的。     

化学去核卵母细胞为受体的小鼠体细胞核移植

卵母细胞的化学去核是采用干扰染色体分离或纺锤体正常功能的化学试剂,使其所有染色质通过纺锤丝牢固结合,并借助极体排出的惯性将所有染色质全部带出胞外,达到去核目的。目前以化学去核处理的MⅡ期卵母细胞为受体,已获得克隆小鼠。然而,第一次减数分裂期的小鼠卵母细胞经化学去核后,进行核移植还未见报道。与传统的机械去核相比,该方法对卵母细胞无机械损伤,完全是极体的自然排放;同时细胞质及其中核重编程相关因子损失量小;而且高效、省时,程序简单,所得的卵胞质或许更适合于供体细胞核的重编程。剪取超排小鼠的卵巢,以注射器刺破有腔卵泡后获得卵母细胞和卵丘细胞复合体,进行体外成熟培养。成熟培养5 h后去除卵丘细胞,挑选生发泡破裂的细胞顺序移入含脱羰秋水仙碱(DC,0.4μg/mL,2 h)和DC(0.4μg/L) 放线菌酮(CHX,50μg/mL)的M16培养液中继续培养,直到第一极体排出。去核卵胞质与胎儿成纤维细胞用植物凝集素(PHA,200μg/mL)粘合后,转入电击槽;施加1个5 V/mm、3μs交流电脉冲和2个92 V/mm、70μs直流电脉冲进行电融合。3 h后,以SrCl2激活6h,于四孔培养皿中制作的“孔中孔”(well of well)体外培养重构胚。试验重复3次,共计698个卵母细胞,获得的重构胚融合率和激活率分别为84.8%和93.6%;胚胎2-细胞发育率为24.7%,4-细胞率为6.74%;2-细胞期克隆胚移植假孕受体后,没有获得怀孕受体。试验分别以“血清饥饿”胎儿成纤维细胞、新鲜细胞和冷冻保存细胞为供体作核移植,结果表明,冷冻保存细胞的融合率(69.3%)与其余两组(80.6%和84.8%)呈显著差异(P<0.05);激活率、2-细胞和4-细胞发育率,则三组间差异不显著(P>0.05)。本研究将化学去核与无透明带技术相结合,完全丢弃了传统核移植的显微操作及其繁琐程序,属手工克隆,它的成功将会大大简化核移植程序,同时提高了核移植的生产力,最终提高核移植总效率。     

中药有效成分对小鼠2-细胞胚胎体外发育的作用

如何获得更多具有活力的可操作的桑椹胚、囊胚一直是胚胎体外培养的研究热点。近二十年来,虽经采用改进培养液成分、改善培养条件、建立体细胞与胚胎共培养体系和添加生长因子、细胞因子等手段,胚胎质量有所提高,但体外受精卵的囊胚发育率仍远低于体内受精,与体内受精囊胚相比,体外受精囊胚的细胞总数和内细胞团细胞数量明显减少,胚胎移植妊娠率和产仔率较低,这些问题均严重影响了胚胎工厂化生产和胚胎产业化的发展,以及育种工作的进程。因此,探索开辟胚胎体外培养生长发育的新途径,提高其发育率和移植妊娠率显得尤为必要。目前,国内外有关中草药有效成分对体外胚胎发育作用的研究甚少。本研究以ICR小鼠2-细胞胚胎为试验材料,将中药有效成分黄芩苷(Baicalin,Bai)、川芎嗪(Ligustrazine,Lig)和小檗碱(Berberine,BR)添加于mCZB基础液中,并以添加双抗的mCZB基础液为试验对照组,比较其对胚胎体外发育的影响。结果表明,体外培养120 h的胚胎孵化率,Bai组(80.6%)、Lig组(78.3%)及BR组(75.9%)极显著高于对照组(51.8%)(P<0.01)。孵化胚胎细胞计数,BR组、Lig组和Bai组(分别为87.2±8.6、83.9±7.7和81.9±6.2),与对照组(77.4±5.6)差异极显著(P<0.01)。说明3种中药有效成分均能显著促进小鼠早期胚胎的体外发育及胚胎细胞增殖。为进一步探讨Bai、Lig、BR对胚胎体外培养发育的效果和验证其胚胎质量,将不同组别培养至桑椹、囊胚期的胚胎进行两种程序常规冷冻,解冻后继续培养,观察其冷冻效果,并将各组解冻后发育至囊胚期胚胎移植。结果表明:冷冻解冻桑椹胚体外培养8~14 h囊胚发育率,程序一中Bai组(65.8%)和Lig组(81.1%)分别显著(P<0.05)和极显著(P<0.01)地高于对照组(48.6%)和BR组(46.7%);程序二中Bai组(80.6%)、Lig组(78.3%)极显著高于对照组(55.2%)和BR组(47.6%)(P<0.01)。冷冻解冻囊胚体外培养6~8 h囊胚发育率,程序一中各组间无显著差异(P>0.05);程序二中,中药有效成分各组间差异不显著(P>0.05),但均显著高于对照组(P<0.05)。两种冷冻程序效果差异不显著(P>0.05)。移植妊娠率和产仔率,Bai组(56.3%,63.3%)、Lig组(52.6%,67.3%)和BR组(55.0%,60.5%)均高于对照组(46.2%,52.8%)。说明3种中药有效成分对于提高小鼠2-细胞胚胎体外发育质量具有一定促进作用,并有利于提高冷冻解冻后移植胚胎的发育潜力。     

Availability of Cadmium in some Phosphorus Fertilizers to Field-Grown Lettuce

Although evaluations of the availability of cadmium (Cd) contaminants in phosphate fertilizers have been made, few have examined the transfer efficiency of Cd from fertilizers to plants, especially under field conditions. This 2-year field study determined the transfer of added Cd to lettuce (Lactuca sativa L.) (Royal Green) from a western phosphate rock (PR) and a triple superphosphate (TSP) as affected by liming and rate of fertilizer (or Cd) input. A readily soluble Cd salt, CdCl₂, was included in the study for comparison. The cumulative amounts of Cd added from the fertilizers and CdCl₂ over the 2-year period ranged from 0 to 1440 g ha^–1. Lettuce yield increased with increasing TSP rates, but was unaffected by PR. Significant (P < 0.01) effects of Cd source and rate, lime, and year were found on Cd accumulation by lettuce. The transfer of the added Cd was consistently higher for CdCl₂ than for the fertilizers regardless of lime rate. A contrasting year effect was also found between the two P fertilizers. In the second year of application, the Cd transfer efficiency increased in the soil treated with the PR, but decreased in the soil treated with the TSP. The Cd transfer efficiency for the plant was better measured with DTPA–Cd (r ²= 0.78 – 0.80) or CaCl₂–Cd (r ²= 0.57 – 0.76) than with soil total Cd (r ²= 0.39 to 0.54) across all Cd sources and lime rates. This is because DTPA–Cd or CaCl₂–Cd reflected the influences of the amount of Cd added, Cd source, and lime rate on Cd accumulation by the plant better than did the soil total Cd. Of the amount of Cd added from the fertilizers an average of 1.0% or less was accumulated in the harvested lettuce tissue. Applications of the fertilizers at high rates could result in increased Cd accumulation in the soil over time.