共查询到20条相似文献，搜索用时 19 毫秒
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采用局部喷、吸、喷和吸组合来模拟局部粗糙壁面,数值计算获得稳定的三维边界层的基本流.在此基础上研究了三维扰动波在该基本流中的空间演化问题,讨论了局部粗糙的形式、分布结构对三维扰动波的幅值增长率及流动稳定性影响.计算结果表明:三维局部粗糙对三维扰动波的增长、涡的形成都起着激励的作用.扰动波演化产生的平均流修正及局部粗糙诱导展向速度的存在,影响着流体运动稳定性.与光滑壁面相比,三维局部粗糙作用下扰动波的传播角度与相位角发生明显变化,而不同形式的二维局部粗糙壁面边界层显示出不同的稳定特性. 相似文献
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Protein modification by amino acid addition is increased in crushed sciatic but not optic nerves 总被引：3，自引：0，他引：3
S Shyne-Athwal R V Riccio G Chakraborty N A Ingoglia 《Science (New York, N.Y.)》1986,231(4738):603-605
Rat optic and sciatic nerves were crushed, and 10 minutes to 3 days later nerve segments between the crushed site and the cell body were removed and assayed for posttranslational protein modification by amino acid addition. Protein modification was comparable in intact optic and sciatic nerves, but in sciatic nerves increased to 1.6 times control levels 10 minutes after crushing and reached a maximum of ten times control levels by 2 hours. In optic nerves activity was decreased throughout the time course studied. The results indicate that, in a nerve which is capable of regeneration (sciatic), protein modification by the addition of amino acids increases immediately after injury, but a nerve incapable of regeneration (optic) is incapable of activating the modification reaction. These findings may be important in understanding the reasons for the lack of a regenerative response after injury to central mammalian nerves. 相似文献
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R A Gillis 《Science (New York, N.Y.)》1969,166(904):508-510
A study of the effects of ouabain and propranolol on the spontaneous activity in the preganglionic sympathetic nerves to the cat heart showed that ouabain can produce both an inhibition and a stimulation of the spontaneous activity in sympathetic nerves. The inhibition appears to be reflex in nature and is not present when the buffer nerves are sectioned. The stimulation is correlated with the development of cardiac arrhythmias and is antagonized by propranolol. 相似文献
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Skeletal muscles lose acetylcholinesterase in culture as a result of denervation. A protein fraction isolated from peripheral nerves maintained the level of acetylcholinesterase in cultures of aneural embryonic muscle or denervated adult chicken muscle. These results indicate that trophic regulation of muscle acetylcholinesterase might be mediated by a protein produced by nerves. 相似文献
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为获得白皮大蒜组培繁殖体系,以其茎尖为材料,通过BA和NAA不同激素配比试验研究,结果表明:诱导愈伤组织的最适培养基为:MS BA0.2mg/L NAA0.5mg/L,诱导率达60%;诱导不定芽的最适培养基为:MS BA1.0mg/L NAA0.1mg/L,丛生芽繁殖系数高达80%。同时,为建立扩繁最佳体系,分别研究了激素、pH、谷氨酸钠三因素对不定芽增殖系数的调节效果,研究表明:添加0.5mg/L的GA3使增值系数提高到13.8;pH5.8最利于不定芽增值;添加10mg/L谷氨酸钠能在多次继代培养中保持较高的增值系数。 相似文献
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银露梅离体繁殖 总被引：1，自引：1，他引：1
任继文 《甘肃农业大学学报》2003,38(2):231-233
银露梅嫩茎切段诱导簇生芽时,以MS+BA 2 mg/L+NAA 0. 2 mg/L效果最好,分化率达100 %;继代培养时以MS+BA 1 mg/L+KT 0.5 mg/L+NAA 0.1 mg/L增殖率最高,达11.71倍;再生苗在1/2 MS+NAA 0.1 mg/L的培养基上生根效果最好。 相似文献
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人工神经网络在恶性肿瘤诊断中的应用 总被引：4，自引：0，他引：4
本研究将人工神经网络方法用于人血清荧光光谱法诊断癌症，采用反向传播神经网络方法，建立识别人血清荧光光谱的网络模型，参数经过训练，平均识别率高达94％。 相似文献
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芦荟离体快速高效增殖技术的研究 总被引：1，自引：0，他引：1
以美国大叶芦荟为材料，就激素配比和接种方式进行芦荟离体快速增殖技术的研究，结果表明，细胞分裂素配合低浓度的生长素可使芦荟的增殖系数净增的60％，最佳增殖培养基为MS＋4．0mg/L BA 0.2mg/L IAA，研究采用的4种接种方式增殖系数跨度在11．2－17．5之间，其中方式3和方式4为理想的接种方式，增殖系数是已有报道水平的3－4倍，最佳的生根培养基为1／2MS＋0．5－1．0mg/L NAA或1／2MS＋0．5－1．0mg/L IAA，另外，就如何降低组培苗的生产成本提出了建议。 相似文献
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A rapid laser scanning system was developed to map the spread of excitation in amphibian and mammalian hearts stained with fluorescent dye. Isochronic maps of conduction were constructed by timing the upstroke of the optical action potential; 128 sites could be scanned in 4 milliseconds. The accuracy of this technique was verified by recording simultaneously from 16 unipolar electrodes placed in different areas of the heart. Conducted action potentials in normal frog heart propagated at 0.1 meter per second. Propagation of action potentials was also monitored in ischemic cat heart, in which both driven and arrhythmic action potential upstrokes could be tracked. The results suggest that this system is capable of scanning the normal and abnormal spread of electrical activity in the heart. 相似文献
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An oxygen-binding hemoglobin localized in the nerves of Tellina alternata (Bivalvia) required 30 minutes to unload oxygen when excised nerves were exposed to pure nitrogen. Neural excitability under these conditions could be sustained only until deoxygenation of the hemoglobin was complete. When the oxygen-combining function of the hemoglobin was abolished with carbon monoxide, the neural excitability ceased within a few minutes of oxygen removal, a response identical to that of hemoglobinless homologous nerves of other bivalves. These results demonstrate that aerobic activity can be supported by the oxygen stored on hemoglobin in microscopic tissues for a considerable time under anoxic conditions. 相似文献
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Transneuronal transfer of herpes virus from peripheral nerves to cortex and brainstem 总被引：13，自引：0，他引：13
The transneuronal transfer of neurotropic viruses may represent an effective tool for tracing chains of connected neurons because replication of virus in the recipient neurons after transfer amplifies the "tracer signal." Herpes simplex virus type 1 was transferred transneuronally from forelimb and hindlimb nerves of rats to the cortical and brainstem neurons that project to the spinal enlargements to which the nerves receiving injections are connected. This transneuronal transfer of herpes simplex virus type 1 from peripheral nerves has the potential to be used to identify neurons in the brain that are related transsynaptically to different nerves and muscles. 相似文献
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土壤含盐量BP神经网络反演模型 总被引：2，自引：0，他引：2
运用Hyperion数据,以黑龙江省大庆市某一实验区为例,通过对图像预处理、特征提取、土壤含盐量、波段与土壤含盐量的相关性分析,建立BP神经网络模型(Back Propagation Network)、经验统计模型等进行研究,并开展了对土壤含盐量的定量提取研究,探讨Hyperion数据反演土壤含盐量的方法.结果表明:与传统的经验统计模型相比,BP神经网络模型具有不可比拟的优越性;同时,Hyperion数据为建立土壤含盐量模型提供了高维的输入样本,大大提高了反演的精度;土壤含盐量的反演模型的研究还有待于进一步深入. 相似文献
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Metabolic dependence of fast axoplasmic transport in nerve 总被引：4，自引：0，他引：4
Fast axoplasmic transport, shown in cat sciatic nerves by a crest of labeled activity after injection of the L7 ganglion with [(3)H]-leucine or [ (3)H]-lysine, was stopped within 15 minutes after death of the animals by bleeding. If the sciatic nerves were removed from the animals and placed in a chamber supplied with oxygen at 38 degrees centigrade, fast transport was sustained. Transport was rapidly blocked in similar in vitro preparations when the nerves were kept in a nitrogen environment. Fast axoplasmic transport is closely dependent upon oxibdative metabolism. 相似文献
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对四川省稻飞虱常发区的灯下，田间稻飞虱资料及４－６月各旬的温度，降水量，相对湿度等因子，用神经网络的Ｂａｃｋ Ｐｒｏｐａｇａｔｉｏｎ算法进行分析，并对发生程度试报，效果较好。 相似文献
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Acetylcholine responses in L cells 总被引：3，自引：0，他引：3
L cells, a family of continuous cell lines of mouse fibroblastic origin, generate a prolonged active membrane hyperpolarization (the hyperpolarizing activation response) when stimulated mechanically or electrically. lontophoretically applied acetylcholine elicits a similar response; atropine blocks the acetylcholine but not the electrically or mechanically elicited responses. The hyperpolarizing activation response can also be elicited by electrical, mechanical, or acetylcholine stimulation of cells adjacent to the recorded cell. Propagation of the response from one cell to another is not dependent on direct electrical coupling between cells and is not blocked by application of a bath containing atropine or curare. These results show that L cells are capable of generating an active electrical response. that they are sensitive to at least one neurotransmitter (acetylcholine), and that humorally mediated interaction (probably noncholinergic) between L cells occurs. 相似文献
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郑志勇 《北京农业职业学院学报》2021,35(1):37-42
以中华秋海棠为研究材料,分别采用自然播种、扦插、分株、珠芽繁殖等方法进行繁殖试验,其中种子繁殖做了种子催芽对比试验,旨在找出适宜的繁殖方法。试验结果表明:常温清水浸泡催芽后播种是中华秋海棠理想的繁殖方法,具有较高的发芽率,可以在生产中推广应用。扦插、分株、珠芽繁殖均有较高的成活率(95%~100%),差异不显著,繁殖效率较低。对比中华秋海棠原生地和引种地的形态表现,应加强中华秋海棠物种保护工作,加强中华秋海棠育种工作,加速中华秋海棠的园林绿化应用。 相似文献