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Soil aggregate (SA) can be formed and stabilized when soil organic matter (SOM) is decomposed in the soil. However, the relationships between the SA dynamics and SOM with different decomposition rates have not been clarified. Therefore, this study examined the effects of the addition of polysaccharides to soil on SA formation and stability. A Japanese tropical soil was incubated for 99 d at 30 °C in a dark environment following the addition of 0.5% (w/w) starch or cellulose. The decomposition rates of the amendments, and SA formation and stability were evaluated by measuring soil respiration rates, and distribution fractions of soil aggregate sizes and mean weight diameter (MWD) of SA, respectively. The cumulative soil respirations with all treatments rapidly increased until Day 12 of the incubation. The initial slope of the cumulative soil respiration in the soil with starch was significantly higher than that in the soil with cellulose. In either soil with starch or cellulose, the fractions of macro-aggregates (>1000 μm in diameter) significantly increased, respectively, compared with control soil. However, the fractions of meso-aggregates (250–1000 μm) and nano-aggregate (<20 μm) in the soil with starch significantly decreased, while those fractions in the soil with cellulose fluctuated until Day 6. The MWDs reached the maximum on Day 6, indicating the SA formation in the soils with starch or cellulose. The increasing rate of the SA formation in the starch-amended soil was greatly higher than that in the cellulose-amended soil. After Day 6, the MWDs in the soils with either polysaccharide decreased with similar trends with no significant differences between treatments, indicating similar stability of the SA in both treatments. This study showed that the different decomposability of the organic amendments might influence the SA formation differently, but not the SA stability. 相似文献
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把仿射约化变换应用于基本模型的割线法中,在近似海色阵修正时采用秩1修正,得到一种求解无约束最优化问题的算法,从理论上证明了算法的二次终止性. 相似文献
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Individual and combined effects of salinity and B toxicity on growth, the major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX) activities, ascorbic acid, proline, and H2O2 accumulation, and stomatal resistance (SR), malondialdehyde (MDA), membrane permeability (MP) and the concentrations of sodium (Na), chloride (Cl) and boron (B) of lettuce were investigated. Boron toxicity and salinity reduced growth of lettuce plants. Under B toxicity, B concentration of the plants was increased, but in the presence of NaCl, the concentration of B was significantly reduced. Sodium and Cl concentrations were increased in B + NaCl and NaCl treatments. Membrane damage was more pronounced in NaCl and B + NaCl treatments. Stomatal resistance of the plants was significantly increased by salinity treatments. The accumulation of proline and ascorbic acid was the highest in the B + NaCl treatment. In general, stress conditions significantly increased H2O2 and antioxidant enzyme (SOD, CAT and APX) activities. The present results indicate that stomatal closure is an important response of lettuce against NaCl and B + NaCl stress. Furthermore NaCl and B + NaCl toxicity-induced oxidative stress in lettuce resulting in lipid peroxidation and membrane damage. Increased antioxidant enzyme activities and also accumulation of ascorbic acid and proline are involved in order to overcome B- and NaCl-induced oxidative stress. 相似文献
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Shuang-Huang-Lian (SHL), a traditional Chinese formula containing Lonicerae japonicae flos (LJF), Scutellariae radix (SR) and Forsythiae fructus (FF), is commonly used to treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. Forsythoside A is one of the main active ingredients in Forsythiae fructus, a key herb in SHL. In the present study, effects of different compositions in SHL on the intestinal absorption of forsythoside A were investigated. The observations from in situ intestinal circulation model showed that A/%(h− 1) of forsythoside A in FF + LSF, FF + SR and SHL were all reduced greatly compared with that in FF. However, in pharmacokinetics study, Cmax and AUC0 → 1440 of forsythoside A all increased and T1/2 prolonged in SHL, FF + LJF and FF + SR compared with FF. The results indicated that the different compositions of SHL decreased absorption but increased bioavailability of forsythoside A, which may be related to its metabolism inhibited in intestine or liver. 相似文献
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脱落酸(Abscisic acid, ABA)对映异构体的生物活性比较 总被引：2，自引：0，他引：2
采用新方法精制脱落酸(ABA)异构体试样,改变以往靠光学离析法分离racemic型(SR)-(±)-ABA,提高了(S)-(+)-ABA与(R)-(-)-ABA两镜像体纯度。抑制生长试验和残留量分析结果表明:天然型(S)-(+)-ABA活性,显着高于非天然型(R)-(-)-ABA或(SR)-(±)-ABA活性。抑制莴苣种子发芽50%的活性强度(S)-(+)-ABA约是(R)-(-)-ABA的5倍,(SR)-(±)-ABA介于二者之间。抑制萝卜下胚轴生长试验,最显着有效期2～6天,(6天后差异渐小,8日甚微),生理作用期约为一周,(S)-(+)-ABA活性是(R)-(-)-ABA的3.6倍。差异原因可能是两异构体分子立体结构不同所致。 相似文献
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开关磁阻电机调速系统是一种新型机电能量转换装置, 具有结构简单坚固、成本低、高容错运行能力、低速高转矩能力和高温运行能力等突出优点。以TI公司的TMS320F2812 DSP为核心，运用光电编码其作为速度和位置传感器，采用霍尔传感器对电流进行采样，设计了全数字化水泵变频驱动系统，并在一台12/8极开关磁阻电机上得到了实现。实验表明与该系统硬件结构简单、实时性强、性价比高，开关磁阻电机的运行性得到提高。该系统应用于水泵具有高可靠性，且可以有效节能。 相似文献
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Brainard BM Epstein KL LoBato D Kwon S Papich MG Moore JN 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2011,25(1):116-122
Background: Critically ill horses are susceptible to thrombotic disease, which might be related to increased platelet reactivity and activation. Objectives: To compare the effect of oral clopidogrel and aspirin (ASA) on equine platelet function. Animals: Six healthy adult horses. Methods: Horses received clopidogrel (2 mg/kg PO q24h) or ASA (5 mg/kg PO q24h) for 5 days in a prospective randomized cross‐over design. Platelet aggregation responses to adenosine diphosphate (ADP) and collagen via optical aggregometry, and platelet secretion of serotonin (5HT) and production of thromboxane B2 (TXB2) by ELISA were evaluated. In horses receiving clopidogrel, high‐performance liquid chromatography analysis for clopidogrel and its carboxylic‐acid metabolite SR 26334 was performed. Results: SR 26334 was identified in all clopidogrel‐treated horses, although the parent compound was not detected. Clopidogrel resulted in decreases in ADP‐induced platelet aggregation persisting for 120 hours after the final dose. ADP‐induced platelet aggregation decreased from a baseline of 70.2 ± 14.7% to a minimum of 15.9 ± 7.7% 24 hours after the final dose (P < .001). Collagen‐induced aggregation decreased from a baseline of 93 ± 9.5% to a minimum of 70.8 ± 16.9% 48 hours after the final dose (P < .001). ASA did not decrease platelet aggregation with either agonist. ASA decreased serum TXB2 from a baseline value of 1310 ± 1045 to 128 ± 64 pg/mL within 24 hours (P < .01). Conclusions and Clinical Importance: Clopidogrel effectively decreases ADP‐induced platelet aggregation in horses, and could have therapeutic applications for equine diseases associated with platelet activation. 相似文献
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Ser/Arg-rich (SR) genes encode proteins that play pivotal roles in both constitutive and alternative splicing of pre-mRNA. However, not much effort has been made to investigate the alternative splicing of their own pre-mRNA. In this study, we conducted comprehensive analyses of pre-mRNA splicing for 22 SR genes in three rice (Oryza sativa L.) ecotypes indica, japonica and javanica. Using different ecotypes we characterized the variations in expression and splicing patterns of rice SR genes in different tissues and at different developmental stages. In addition, we compared the divergence in expression and splicing patterns of SR genes from seedlings of different rice ecotypes in response to hormones application and environmental stresses. Our results revealed the complexity of alternative splicing of SR genes in rice. The splicing varies in different tissues, in different ecotypes, in response to stresses and hormones. Thus, our study suggested that SR genes were subjected to sophisticated alternative splicing although their encoding proteins were involved in the splicing process. 相似文献
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