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991.
Delayed feedbacks are quite common in many physical and biological systems and in particular many physiological systems. Delay
can cause a stable system to become unstable and vice versa. One of the well-studied non-biological chemical oscillators is
the Belousov-Zhabotinskii (BZ) reaction. This gives relaxation oscillations for a considerable period of time under batch
conditions. This paper deals with the effect of perturbing the limit cycle oscillation of BZ reaction by employing a delayed
electrical feedback to the system under batch conditions. The parameters chosen to study are external resistance and delay.
For various resistances and delays the system was electrically perturbed and found to exhibit various complex mixed mode oscillations.
The dynamic features are accounted for by the Oregonator model, with time delay incorporated in one of the variables.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
992.
993.
G. R. Yurchenko A. K. Matkovsky A. P. Shimansky 《Reaction Kinetics and Catalysis Letters》1993,50(1-2):163-167
Differential isosteric adsorption heats and entropies of adsorption of both n-pentane and diethyl ether on hydrated and dehydrated surfaces of pyrogenic alumina (S=140 m2/g) in the coverage range of 0.15–1.0 have been calculated from the adsorption isotherms. 相似文献
994.
995.
996.
A method is presented for simultaneous separation of traces of toxic and essential elements from soils. The method is based on programmed vacuum-thermic extraction of the elements in an oxidation-reduction medium. Under optimal conditions of temperature and pressure Pb, Zn, Cd, Bi, Tl, As, Sb, Te, Mo, Hg and Re are distilled or sublimated in elementary state or as oxides. A simple quartz apparatus is proposed. The elements extracted from matrix are dissolved in nitric acid and determined by AAS or OES with ICP excitation. 相似文献
997.
在很高的温度和适宜的生长条件下,分别采用熔盐籽晶法和高温引上法生长了高质量的YAP、NAB、KTP、LN、BBO、SBN等多元氧化物单晶,它们具有优良的物理化学性能,严格的化学比,固定的组成与结构以及较好的化学均匀性和电子束轰击下的稳定性。广泛地用于激光和非线性光学领域。我们选用这些晶体为原材料研制电子探针定量分析的标准样品。经过测量和标定,这些单晶标样符合中华人民共和国国家标准GB 4930-85(电子探针显微分析标准样品通用技术条件)的规定。含有稀土元素的标样如NAB和YAP能发出绿色荧光,是电子显微术中理想的阴极发光材料。 相似文献
998.
999.
为了研究白血病骨髓移植病人全血微量元素铜的变化及其意义 ,用原子吸收光谱法检测了正常对照组与白血病骨髓移植患者预处理前及移植后骨髓空虚期全血微量元素铜的含量。结果表明 ,正常对照组全血铜浓度与白血病骨髓移植患者预处理前全血铜浓度差异无显著性 (P >0 0 5 ) ,而与骨髓空虚期全血铜浓度有显著性差异 (P <0 0 5 ) ,说明白血病缓解后血铜接近正常对照组水平 ,而白血病骨髓移植患者预处理后骨髓空虚期全血铜含量高于正常对照组 ,说明预处理影响微量元素铜的代谢 ,本文就其影响机理进行了研究 相似文献
1000.
The genesis and elimination of early afterdepolarizations (EADs) have been investigated in guinea pig cardiac ventricular fibers after a short period of cooling (5h, 2—4℃). After rewarming them to 37℃, EADs could be induced by K~+-free superfusion at an appropriate driving stimulation (0.2 Hz) in all preparations. A high level plateau, which linearly increases its duration with time, appears ahead of EADs. The critical point of the plateau occurred steadily at the level of -47±4 mV. Two types of triggered activity, all of which are the rhythmic activities in low level of membrane potential (-50 to -60 mV), appear on the platcau. There is no significant change after overdriving. Agonists of the Na-K pump (K~+ and Tl~+) could stop the rhythmic activity immediately and turn the low level of membrane potential to high one. The results showed that high level plateau is the basis of genesis of EADs, and the activation of Na-K pump plays an important part in stopping triggered rhythms arising from EADs. 相似文献