农田生态系统中氮循环模型研究进展   总被引：1，自引：1，他引：1  

张俊  徐绍辉  刘建立  张佳宝 《灌溉排水学报》2006,25(3):85-88

农田生态系统中的氮循环是影响农业生产力的主要因素之一,同时也会对环境产生影响。在农田生态系统氮循环的研究中模型已成为重要的工具而受到人们关注。在介绍国际上发表的模型基础上,阐述了目前一些比较成功的模型的研究进展,并指出了今后模型发展的趋势。  相似文献   

扭振减振器对曲轴弯曲和纵向振动的影响研究     

段秀兵  郝志勇 《拖拉机与农用运输车》2005,(5):32-34

以一台多缸柴油机为例,采用结合有限元法(FEM)的多体系统仿真(MSS)方法,研究了扭转振动减振器振动对曲轴弯曲、纵向振动的影响;实验测量了有无扭振减振器时的曲轴自由端的弯曲和纵向振动,其与计算结果吻合得较好。  相似文献   

Expression of cathepsin C and tumor necrosis factor-α in human coronary artery and their relationships with coronary heart disease     

ZHANG Qiong  WAN Chang-wu  YU Yan-ni  XIA-Bing  LIU Jiang-jin  ZHANG Qiao-jun  LI Zhu  WANG Cheng-fei  DAI Jia-lin  WANG Jie 《园艺学报》2021,36(12):2133-2138

AIM To explore the possible mechanism of cathepsin C （CTSC） and tumor necrosis factor-α （TNF-α） in coronary heart disease （CHD） by detecting the protein expression of CTSC and TNF-α in human coronary artery tissue. METHODS The coronary artery tissues from 52 cases of CHD and 25 cases of accidental death without any heart disease in the Forensic Judicial Expertise Center of Guizhou Medical University from October 2018 to December 2019 were collected as CHD group and control group, respectively. The coronary artery stenosis and intimal plaque formation were examined by histopathology, the protein expression of CTSC and TNF-α was determined by Western blot, and the intracellular expression of CTSC and TNF-α was analyzed by immunohistochemical staining. RESULTS The results of HE staining showed that the intima of coronary artery in control group was smooth, and no thickening or stenosis was observed. In CHD group, the intima thickened irregularly, atherosclerotic plaques formed, the intima became thinner and the lumen showed eccentric stenosis in varying degrees （P<0.05）. The results of Western blot showed that the expression of CTSC and TNF-α in CHD group was significantly higher than that in control group （P<0.05）. Immunohistochemical staining showed that both CTSC and TNF-α were expressed in the cytoplasm of foam cells, and their positive expression was significantly higher than that in control group （P<0.05）. The results of Pearson moment correlation analysis showed that there was positive correlation between the expression of CTSC and TNF-α in CHD （r²=0.743, P<0.05）. CONCLUSION The up-regulated expression of CTSC in coronary artery tissue may promote the expression of TNF-α and affect the occurrence and development of CHD.  相似文献   

灰斑病菌对大豆叶片总多酚和总黄酮的诱导研究     

徐兆飞  刘亚光 《大豆科学》2006,25(3):234-238

利用大豆灰斑病菌不同致病力的生理小种接种抗感不同的大豆品种,结果表明:大豆叶片内总黄酮类物质的含量与品种的抗病性呈明显正相关;感病品种叶片内总多酚含量变化显著降低,抗病品种总体变化不大.接种致病力强的生理小种能够大幅度提高抗病品种体内总黄酮含量,这一结果可以作为筛选和鉴定抗病品种的一种生化指标;大豆灰斑病菌弱毒菌株能够诱导感病品种体内总黄酮含量提高,进而提高大豆的抗病性,这一结果为大豆灰斑病的生物防治提供了依据.  相似文献   

利杂犊牛小肠各段长度与黏膜结构的发育学变化   总被引：5，自引：0，他引：5  

宋恩亮  陈耀星  王子旭  巢国正  万发春  吴乃科 《动物医学进展》2006,27(5):66-70

利用图像分析法研究1月龄,4月龄和6月龄健康利杂犊牛小肠结构的发育形态变化。结果显示,犊牛小肠各段在不同的月龄,其长度变化差异显著(P<0.05);不同月龄犊牛的十二指肠、空肠、回肠的黏膜厚度、肌层厚度不同程度的增加且差异极显著(P<0.01);从1月龄至6月龄,十二指肠、回肠绒毛长度分别增加45.7%和8.0%;而空肠的绒毛以4月龄最长(392.48μm),绒毛高度/隐窝深度(V/C)值以4月龄的最大(2.63),且与1月龄和6月龄时比较差异极显著(P<0.01),但1月龄与6月龄相比较差异不显著(P>0.05)。结果提示,6月龄前犊牛小肠黏膜结构变化较大,犊牛断奶合理日龄应进一步研究。  相似文献   

中华鲟幼鲟维生素C营养需要的研究   总被引：5，自引：0，他引：5  

高强  文华  李英文  雍文岳  刘伟  罗晓松  蒋明  丁诗华 《动物营养学报》2006,18(2):99-104

本研究旨在确定中华鲟幼鲟对维生素C(VC)的营养需要量。配制含VC分别为0.5、59.8、119.5、239.1、478.1和956.2 mg/kg饲料的6组日粮(分别编号为C0.5、C59.8、C119.5、C239.1、C478.1和C956.2),连续投喂中华鲟幼鲟8周后,以生长速度、组织VC含量和部分相关酶活性来确定中华鲟对VC的需求量。结果表明,C0.5和C59.8组鲟鱼的增重率、饲料效率、蛋白质效率都低于C119.5组,进一步提高饲料VC含量,也没有显著变化(P>0.05);C478.1组的肝脏和肌肉组织VC含量达最高水平;C239.1组血清溶菌酶活性最高;C239.1组SOD活性最低。根据平均增重率和饲料效率做折线法分析表明,维持中华鲟最佳生长的饲料VC含量为108.5 mg/kg;肝脏中VC含量达最大时饲料VC添加量为309.4 mg/kg;肌肉中VC含量达最大时饲料VC添加量为273.3 mg/kg。  相似文献   

川西北高寒沙化草地围栏禁牧时段和恢复过程的耦合机理研究     

黄怡  赵聪  杨洋  刘轲  牟秋雨  杨林  胡进耀 《四川林业科技》2021,(1):60-64

川西北沙化草地在围栏禁牧生态恢复过程中,土壤中有机质、全氮、水解性氮变化特征,研究对象为:未修复沙化草地、围栏禁牧生态恢复时间分别为5年、10年的沙化草地,研究其不同围栏禁牧时间沙化草地0～40 cm土层土壤中有机质、全氮、水解性氮的变化.其结果表明,随着围栏禁牧时间的增长,各土层土壤有机质、全氮含量均增加,植被盖度、...  相似文献   

余甘子果实维生素C动态积累规律研究     

王建超  郭林榕 《中国果业信息》2018,47(4)

为研究不同品种余甘子果实维生素C含量差异和余甘子果实维生素C积累规律,本研究以6个品种余甘子果实为试材,比较不同时期余甘子果实维生素C含量的差异,描绘维生素C积累动态曲线。结果表明,余甘子果实维生素C含量丰富,适宜作为食品加工和保健品的开发利用;其中秋白品种维生素C含量最高,适宜作为加工和遗传育种的原材料;余甘子果实作为加工原材料适宜采收期为10月20日左右;维生素C 的积累分为快速积累阶段,缓慢积累阶段,下降阶段,稳定阶段4个阶段。  相似文献   

爱媛28’香橙砧与枳砧在南平市引种表现与评价     

应薛养 《中国果业信息》2021,50(4)

2017年引进早熟杂柑品种‘爱媛28’香橙砧和枳砧苗分别在大棚设施和露天进行试种,栽培4年调查比较两个砧木组合的生长表现、丰产性与果实品质,结果表明：‘爱媛28’香橙砧树表现生长势强,冠幅、树高、茎粗、结果枝、秋梢等生长量指标显著大于枳砧树,3a树初产1436 kg/667㎡,4a树2523kg/667㎡,显著高于枳砧4a树初产1809kg/667㎡;大棚种植香橙砧4a树果实10月下旬TSS11-12%,12月中旬TSS可达15%,与枳砧相当,可滴定酸比枳砧略高,两者固酸比均达18以上,口感风味极佳,两者单果重、果形指数、果皮厚度、可食率无显著性差异;未密封大棚4a树体经受2020年寒冬极端低温考验无明显冻害,抗旱抗寒能力中等,易感黑点病和流胶病,大棚种植能很好预防黑点病。综合评价爱媛28枳砧和香橙砧均适合在南平市种植,香橙砧比枳砧早期丰产性稳产性好,收益更高,香橙砧‘爱媛28’设施种植较枳砧更具优势。  相似文献   

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea     

Marine Remize  Frdric Planchon  Matthieu Garnier  Ai Ning Loh  Fabienne Le Grand  Antoine Bideau  Christophe Lambert  Rudolph Corvaisier  Aswani Volety  Philippe Soudant 《Marine drugs》2022,20(1)

The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a ¹³C-enriched isotopic marker, ¹³CO₂, for 24 h during the exponential growth of the algae. The ¹³C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in ¹³C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in ¹³C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the ¹³C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis.  相似文献