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991.
Fullerenes are of tremendous interest from fundamental researches to applied perspectives in the past decades. However, their application in supercapacitors has been underdeveloped for a long time. Here, the KOH activation of C70 microtubes is reported at high temperatures, which provides activated samples exhibiting excellent capacitive properties. The improved capacitive performance can be attributed to three aspects: the generation of macropores and micropores, the introduction of oxygen functionalities, and the formation of graphitic carbons from ellipsoidal fullerenes. The optimum activated state for supercapacitor application is achieved at 600 °C, at which the product exhibits the best electrochemical behavior with a gravimetric capacitance of 362.0 F g?1 at 0.1 A g?1 and excellent cycling stability with capacitance retention of 92.5% over 5000 cycles at 1 A g?1.  相似文献   
992.
Particle size of lignocellulose materials is an important factor for enzymatic hydrolysis efficiency. In this study, corn stover was milled and sieved into different size fractions from 1.42, 0.69, 0.34, to 0.21 mm, and the corresponding enzymatic hydrolysis yields were 24.69, 23.96, 25.34, and 26.97 %, respectively. The results indicate that the hydrolysis yield is approximately constant with changing corn stover particle sizes in the experimental range. The overall surface area and the inner pore size measurement show that the overall specific surface area was less than 2 % with the half reduction of particle size due to the greater inner pore surface area. The scanning electron microscope photographs gave direct evidence of the much greater inner pore surface area of corn stover particles. This result provided a reference when a proper size reduction of lignocellulose materials is considered in biorefining operations.  相似文献   
993.
994.
995.
In flowering plants, the male and female gametogenesis is a crucial step of sexual reproduction. Although many genes have been identi fied as being involved in the gametogenesis process, the genetic mechanisms underlying gametogenesis remains poorly understood. We reported here characterization of the gene, ABORTED GAMETOPHYTE 1(AOG1) that is newly identi fied as essential for gametogenesis in Arabidopsis thaliana. AOG1 is expressed predominantly in reproductive tissues including the developing pollen grains and ovules. The AOG1 protein shares no signi ficant amino acid sequence similarity with other documented proteins and is located mainly in nuclei of the cells. Mutation in AOG1 caused degeneration of pollen at the uninucleate microspore stage and severe defect in embryo sacs, leading to a signi ficant reduction in male and female fertility.Furthermore, the molecular analyses showed that the aog1 mutant signi ficantly affected the expression of several genes, which are required for gametogenesis. Our results suggest that AOG1 plays important roles in gameto genesis at the stage prior to pollen mitosis I(PMI)in Arabidopsis, possibly through collaboration with other genes.  相似文献   
996.
Exploitation of heterosis in rice(Oryza sativa L.) has contributed greatly to global food security.In this study,we generated three sets of reciprocal F1 hybrids of indica and japonica subspecies to evaluate the relationship between yield heterosis and the circadian clock.There were no differences in trait performance or heterosis between the reciprocal hybrids,indicating no maternal effects on heterosis.The indica-indica and indica-japonica reciprocal F1 hybrids exhibited pronounced heterosis for chlorophyll and starch content in leaves and for grain yield/biomass.In contrast,the japonica-japonica F1 hybrids showed low heterosis.The three circadian clock genes investigated expressed in an above-high-parent pattern(AHP)at seedling stage in all the hybrids.The five genes downstream of the circadian clock,and involved in chlorophyll and starch metabolic pathways,were expressed in AHP in hybrids with strong better-parent heterosis(BPH).Similarly,three of these Research Arfive genes in the japonica-japonica F1 hybrids showing low BPH were expressed in positive overdominance,but the other two genes were expressed in additive or negative overdominance.These results indicated that the expression patterns of circadian clock genes and their downstream genes are associated with heterosis,which suggests that the circadian rhythm pathway may be related to heterosis in rice.  相似文献   
997.
目的:评估窝沟封闭对预防第一磨牙窝沟龋的2年临床疗效。方法:选择贵阳市花溪区200名7-9岁经家长同意并签署窝沟封闭知情同意书的学生为实验组,进行第一磨牙窝沟封闭;因家长不同意而未进行窝沟封闭的200名同龄学生为对照组,两年内复查两组的龋病发病率和封闭剂的保留情况。结果:实验组窝沟封闭后第一年、第二年第一磨牙龋病的发生率分别为1.50%和1.01%,而对照组分别为4.00%和6.57%,第二年实验组的第一磨牙龋病发病率显著低于对照组,差异有统计学意义(P0.05)。实验组第一年、第二年的封闭剂完全保留率分别是85.5%和80.4%。结论:窝沟封闭作为一项健康干预措施,能有效降低学生的龋病发病率。  相似文献   
998.
动脉粥样硬化既是胆固醇在血管壁聚集的疾病,也是发生在动脉壁的一种低强度慢性炎症形式。近年来有研究证实胆固醇结晶在动脉粥样硬化发生发展中具有重要作用。新的显微技术证实,胆固醇结晶在动脉粥样硬化斑块形成的早期即已出现,并与早期炎症有关。胆固醇结晶通过诱发局部炎症,促进大的脂质核心形成;刺破纤维帽,导致斑块破裂进而促进动脉粥样硬化斑块的进展。在影响斑块进程中,NLRP3炎症体的激活对此发挥了重要的作用。NLRP3炎症体是研究最多最明确的炎症体,其与非炎症性疾病的发生发展密切相关。以胆固醇结晶激活NLRP3炎症体的途径作为研究靶点,为动脉粥样硬化的诊断和治疗提供了新的思路和方法。该文就胆固醇结晶在动脉粥样硬化斑块中激活巨噬细胞NLRP3炎症体的两种途径做一综述。  相似文献   
999.
1000.
以食用菌重要害虫-厉眼蕈蚊属的Lycoriella ingenua为研究对象,研究了不同逆境温度下各虫态存活率的差异。结果表明温度对不同虫态存活率的影响存在显著性差异。成虫和蛹对高温具有一定适应性,卵对高温的适应性最低但具有一定的低温耐受力。在35-40℃高温下,相同暴露时间,各虫态的存活率随温度的升高而降低,但成虫的存活率均高于其它虫态。38℃下全部死亡的暴露时间分别为:成虫48 h,蛹24 h,幼虫12 h,卵2h。在40℃达到全部死亡的暴露时间分别为:成虫24 h、蛹12 h、卵和幼虫0.5 h。低温处理下,各虫态随着暴露时间的延长存活率逐渐降低。5℃低温下,相同暴露时间,成虫存活率均高于其它虫态,但在0℃低温下暴露24 h后全部死亡,显著高于其它虫态;幼虫在低温下取食活动减弱,5℃下暴露24 h后停止取食,相同暴露时间下随着温度的降低存活率下降;蛹对0℃的耐受力高于成虫和幼虫,暴露4 h后可以正常羽化,48 h后全部死亡;卵对短时间的低温具有一定耐受力,但随着暴露时间的延长存活率降低幅度大。  相似文献   
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