首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 203 毫秒
1.
生化反应中一类三次系统的极限环   总被引:1,自引:0,他引:1  
研究生化反应中一类三次系统:dx/dt=-x-Ф1(x)+yФ2(x),dy/dt=a0+Ф1(x)-yФ2(x)其中Ф1(x)=Ax^3+ax^2+bx+B,Ф2(x)=cx^2+dx+e.较完整地解决了该系统极限环的存在性,唯一性与不存在性等问题.  相似文献   

2.
一类KOLMOGOROV系统的极限环   总被引:7,自引:0,他引:7  
关于两种群互相作用的Kolmogorov模型 x=xF_1(x,y), y=yF_2(x,y),文〔1〕根据生态意义对F_1、F_2给出较多限制条件下作过研究,由于现实中总结出的模型归结到F_1、F_2为x和y的多项式的形式不少〔2,3〕,本文讨论一类Kolmogorov系统x=x(a_0+a_1x-a_3x~2+a_2y+a_4xy),y=y(x-1) (1)极限环的存在性和唯一性,其中x和y分别表示两种群的密度,参数a_0>o,a_3>o,a_1、a_2、a_4不定号,它们各表示一定的生态意义,随不同的取值范围而反映两种群的不同作用〔1〕。  相似文献   

3.
以x(m/n)为功能性反应函数的食饵-捕食系统的定性分析   总被引:1,自引:0,他引:1  
研究了功能性反应函数ψ(x)为x(m/n)(0<m/n<1)的食饵-捕食系统dx/dt=ax-bψ(x)y-cx2,dy/dt=-dy+eψ(x)y-fy2.证明了此系统当1/2≤m/n<1时至多存在唯一正平衡点;当0<m/n<1/2时必有出现三个正平衡点的可能.并讨论了此系统的拓扑结构,给出了数值例子.  相似文献   

4.
一类含单奇点的极限环的三次系统   总被引:1,自引:0,他引:1  
盖平 《生物数学学报》2003,18(4):445-447
证明具体三次系统x=y-εy~3,y=x(1-x~2)+(α-x~2)y,当α≥1或0<α≤1/3时,在区域|y|<1/ε~(1/2)内无含单奇点的极限环,这里ε>0.  相似文献   

5.
用定性分析的方法对一类Kolmogorov系统(dx)/(dt)=x(a_0-a_11x a_2x~(n-1)-a3x~n a_4xy~m),(dy)/(dt)=y(b_1x~n-b_2),进行了研究.讨论了系统平衡点的性态,给出了系统无闭轨的充分条件以及存在唯一稳定极限环的条件.包含并推广了文献[3]的相关结果.  相似文献   

6.
本文运用Liapunov第二方法,论证了功能反应函数为x~(1/x)的食饵-捕食系统x=x-ax-2~3-x~(1/x)y,βy=-sy βx~(1/x)y-εy~2唯一正平衡点的稳定性.其次将该系统化为二次微分系统Ⅲ类方程的标准形式,进而研究了极限环的存在唯一性问题.  相似文献   

7.
一类三次Kolmogorov系统的极限环存在性和唯一性   总被引:6,自引:0,他引:6  
研究一类三次Kolmogorov系统:x=x(A0+A1x-A3x2+A2y+A4xy),y=y(-1+x2-y)(*).当A1>0,A2<0,A4<0时得到:当A0-A2>A02.x*>x*时,系统(*)在第一象限内存在极限环;当A0>(A1A2)/A4,A3>A3时,系统(*)在第一象限内存在唯一的极限环.  相似文献   

8.
一类具功能反应的食饵-捕食者两种群模型的定性分析   总被引:32,自引:4,他引:28  
对具功能反应的食饵-捕食者两种群模型x=xg(x)-y( )(x),y=y(-d+e( )(x)).在g(x)=α-baα,( )(x)=cxα(a,b,c>0,1/2≤α<1)且α使函数f(x)=x1/a在(-∞,+∞)上为偶函数时进行了研究,讨论了该系统平衡点的稳定性态,系统无环的充分条件以及在正平衡点外围存在惟一稳定极限环的条件.  相似文献   

9.
一类具功能反应的食饵-捕食者两种群模型的定性分析   总被引:66,自引:5,他引:61  
研究了具功能反应的食饵-捕食者两种群模型:x=xg(x)-yф(x),y=y(-d eф(x))。在g(x)和ф(x)都是非线性情形下,讨论了该系统的平衡点的性态,并证明了极限环的存在性与唯一性及其全局稳定性。  相似文献   

10.
功能反应函数为kxθ的食饵-捕食系统的定性分析   总被引:1,自引:0,他引:1  
杨柳 《生物数学学报》2007,22(3):441-446
研究了具功能反应的一类食饵-捕食系统:x=x(a—bx^m-h(x))(z))-kx^θY,y=Y(-e+dkx^θ)(0〈θ≤1)并得到了系统在正平衡点外围的极限环的不存在性与存在唯一性的相关条件.  相似文献   

11.
目的:探讨标本溶血对生化项目检测结果的影响,并使用溶血指数对影响程度进行量化,并探讨其临床意义。方法:总蛋白(TP)、尿酸(UA)、肌酸激酶(CK)、乳酸脱氢酶(LDH)、总胆红素(TBIL)均参考美国临床实验室标准化委员会(CLSI)制定的评价方案EP7-A2文件的标准程序,每个项目收集20份新鲜混合血清(TBIL<17.1μmol/L和TBIL>150μmol/L分别收集),包括参考值范围内的10份、低值和高值各5份,每份新鲜混合血清用3~4份入选血样混合成约8 mL。每份新鲜混合血清分成若干份,分别与洗涤好红细胞配制的溶血液制成5个不同浓度的溶血模型(试验组)及与之配对的无溶血模型(对照组),然后分别测定试验组、对照组及分出的1份混合血清原样的血红蛋白浓度,并在罗氏cobasC501全自动生化分析仪上测定3次所需项目和溶血指数,计算血红蛋白浓度与溶血指数之间的关系,以及溶血对TP、UA、CK、LDH、TBIL检测结果影响的大小。参考EP7-A2文件的统计方法,计算最大允许偏差对应的干扰物浓度,以每份测试混合血清的溶血指数为x轴、其对应的检测项目变化值(干扰值)为y轴绘制干扰曲线。结果:对每项目20份混合血清的660个测试、5个项目3960检测结果用假设检验统计,TP、CK、LDH、TBIL(<17.1μmol/L和>150μmol/L)的μ值分别为4.42、2.34、2.20、2.76、2.93,P值均小于0.05,说明溶血对TP、UA、CK、LDH、TBIL均存在显著干扰。通过回归分析统计出不同溶血程度的溶血指数值对应的干扰变化值的干扰剂量反应曲线。TP、CK、LDH、TBIL的干扰剂量回归方程分别为y=0.0099x-0.065、y=0.1001x-2.42、y=1.1406x-1.3303、y=1.78×10-5x2-0.011x-0.235、y=1.88×10-5x2-0.048x-4.169。从干扰剂量反应曲线可看出溶血对LDH、CK、TP检测产生正干扰,对TBIL检测产生负干扰。同时发现溶血对UA结果的干扰很不稳定,即溶血对尿酸检测结果存在正干扰及负干扰,这一结果得到相关文献印证。结论:溶血指数可作为标本是否合格的客观指标,避免主观判断的误差;利用测得的溶血指数,可从干扰剂量曲线或回归方程求出检测结果的变化值,使临床通过干扰曲线判断溶血对检测项目产生的影响,从而做出准确客观的判断。  相似文献   

12.
The expression of neutral glycosphingolipids and gangliosides has been studied in human skeletal and heart muscle using indirect immunofluorescence microscopy. Transversal and longitudinal cryosections were immunostained with specific monoclonal and polyclonal antibodies against the neutral glycosphingolipids lactosylceramide, globoside, Forssman glycosphingolipid, gangliotetraosylceramide, lacto-N-neotetraosylceramide and against the gangliosides GM3(Neu5Ac) and GM1(Neu5Ac). To confirm the lipid nature of positive staining, control sections were treated with methanol and chloroform:methanol (1:1) before immunostaining. These controls were found to be either negative or strongly reduced in fluorescence intensity, suggesting that lipid bound oligosaccharides were detected. In human skeletal muscle, lactosylceramide was found to be the main neutral glycosphinogolipid. Globoside was moderately expressed, lacto-N-neotetraosylceramide and gangliotetraosylceramide were minimally expressed and Forssman glycosphingolipid was not detected in human skeletal muscle. The intensities of the immunohistological stains of GM3 and GM1 correlated to the fact that GM3 is the major ganglioside in skeletal muscle whereas GM1 is expressed only weakly. In human heart muscle globoside was the major neutral glycosphingolipid. Lactosylceramide and lacto-N-neotetraosylceramide were moderately expressed, gangliotetraosylceramide was weakly expressed and the Forssman glycosphingolipid was not expressed at all in cardiac muscle. GM3 and GM1 were detected with almost identical intensity. All glycosphingolipids were present in plasma membranes as well as at the intracellular level. Abbreviations used: BSA, bovine serum albumin; DAPI, 4,6-diamidine-2-phenylindole-dihydrochloride; DTAF, fluorescein isothiocyanate derivative; GSL(s), glycosphingolipid(s); Neu5Ac,N-acetylneuraminic acid [50]; PBS, phosphate buffered saline. The designation of the following glycosphingolipids follows the IUPAC-IUB recommendations [51] and the nomenclature of Svennerholm [52]. Lactosylceramide or LacCer, Gal1-4Glc1-1Cer; gangliotriaosylceramide or GgOse3Cer, GalNAc1-4Gal1-4Glc1-1Cer; globotriaosylceramide or GbOse3Cer, Gall-4Gall-4Glcl-1Cer; gangliotetraosylceramide or GgOse4Cer, Gal1-3GalNAc1-4Gal1-4Glc1-1Cer; globotetraosylceramide or GbOse4Cer, GalNAc1-3Gal1-4Gal1-4Glc1-1Cer; lacto-N-neotetraosylceramide or nLcOse4Cer, Gal1-4GlcNAc1-3Gal1-4Glc1-1Cer; Forssman GSL or GbOse3Cer, GalNAc1-3GalNAc1-3Gal1-4Gal1-4Gle1-1Cer; GM3, II3Neu5Ac-LacCer; GM2, II3Neu5Ac-GgOse3Cer; GM1, II3Neu5Ac-GgOse4Cer; GD3 II3(Neu5Ac)2-LacCer; GD2, II3(Neu5Ac)2-GgOse3Cer; GD1a, IV3Neu5Ac, II3Neu5Ac-GgOse4Cer; GD1b, II3(Neu5Ac)2-GgOse4Cer.  相似文献   

13.
We study a system of ODE's modelling the interaction of one predator and one prey dx/dt = xg(x) - yp(x), dy/dt = gamma y[- delta - nu y - alpha y2 + h(x)]. This system defines a two-species community which incorporates competition among prey in the absence of any predators as well as a density-dependent predator specific death rate. This system is investigated under ecologically natural regularity conditions and assumptions on g, p and h to ensure the existence and uniqueness of limit cycles. The proof uses the standard Hopf-Andronov bifurcation theory and the technique of Liénard's equation.  相似文献   

14.
李肖叶甲成虫数量及三维空间格局动态   总被引:1,自引:0,他引:1  
对合肥地区李肖叶甲成虫数量动态及三维空间格局进行研究,结果表明该成虫5月下旬初见,6月4日至7月16日为发生高峰期,9月上旬仍有零星虫口。6月4日至9月10日种群增长模型为y=1692.2258e-0.0545t,6月4日至8月27日树冠上部部位增长模型为y=205.60e-0.0523t,树冠西部部位的增长模型为y=257.13e-0.0505t。样地中的李肖叶甲5月21日至8月13日半变异函数方程是y=0.0709x3-10.479x2+391.67x-300.71、y=-0.0122x3+1.1201x2-19.781x+317.84、y=-0.0013x3+0.1613x2-4.4862x+67.363、y=-0.0016x3+0.9177x2-11.495x+551.94、y=-0.0029x3+0.3034x2-7.5906x+103.37和y=-0.0002x3+0.0172x2-0.4975x+13.691,变程在20.3938—65.0289之间,均为聚集格局,聚集强度指标表明也均为聚集格局;树冠东、西、南、北方位的水平分布5月21日至8月13日的C值均大于1,I值均大于0,CA值均大于0,Iw值均大于1,为聚集格局;树冠上、中、下方位的垂直分布6月4日至8月13日的C值均大于1,I值均大于0,CA值均大于0,Iw值均大于1,为聚集格局;5月21日至8月13日的树冠东、南、西、北、上、中、下部位的C值均大于1,I值均大于0,CA值均大于0,Iw值均大于1,三维分布均为聚集格局。用Iwao公式计算的结果与聚集强度指标分析的结果一致。6月4日—8月13日林间李肖叶甲的种群聚集均数λ值均大于2,聚集是李肖叶甲本身的行为所致。  相似文献   

15.
The simultaneous equations
$$\begin{gathered} \frac{{dx}}{{dt}} = \frac{{a_x }}{{k_x }}[k_x - x - f_x (y)] x \hfill \\ \frac{{dy}}{{dt}} = \frac{{a_y }}{{k_y }}[k_y - y - f_y (x)] y \hfill \\ \end{gathered}$$  相似文献   

16.
The trisaccharide Gal13Gal14GlcNAc1O-(CH2)8COOCH3 was enzymatically synthesized, within situ UDP-Gal regeneration. By combination in one pot of only four enzymes, namely, sucrose synthase, UDP-Glc 4-epimerase, UDP-Gal:GlcNAc 4-galactosyltransferase and UDP-Gal:Gal14GlcNAc 3-galactosyltransferase, Gal13Gal14GlcNAc1O-(CH2)8COOCH3 was formed in a 2.2 µmol ml–1 yield starting from the acceptor GlcNAc1O-(CH2)8COOCH3. This is an efficient and convenient method for the synthesis of the Gal13Gal14GlcNAc epitope which plays an important role in various biological and immunological processes.  相似文献   

17.
The activity of UDP-Gal: LacCer galactosyltransferase in human placenta was studied by using crude homogenate and Triton CF-54 extract as the source of enzyme. Transfer of galactose to lactosylceramide was optimal in the presence of 0.1% Triton CF-54 and Mn2+ at pH 6.3, and the reaction product was susceptible to -galactosidase.Abbreviations LacCer lactosylceramide (Gal1-4Glc1-1Cer) - Gb3 globotriaosylceramide (Gal1-4Gal1-4Glc1-1Cer) - Gb4 globoside (GalNAc1-3Gal1-4Gal1-4Glc1-1Cer) - TLC thin-layer chromatography - GC/MS gas chromatography/mass spectrometry - NMR nuclear magnetic resonance - EDTA ethylenediamine tetraacetic acid - CHAPS 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate  相似文献   

18.
温度、盐度对强壮箭虫耗氧率和窒息点的影响   总被引:1,自引:0,他引:1  
Liu Q  Zhu HY  Liu F  Ding ZY 《应用生态学报》2011,22(11):3081-3086
研究了不同温度、盐度下强壮箭虫的耗氧率和窒息点.结果表明:温度和盐度均对强壮箭虫的耗氧率和比耗氧率有显著影响.试验温度在5℃-25℃,强壮箭虫个体耗氧率(IO)和比耗氧率(SO)开始随温度的升高而升高,之后呈明显下降趋势.其回归方程分别为y=0.0058x3 -0.2956x2+4.415x-8.7816(R2=0.99,P<0.05)和y=0.0011x3 -0.0546x2+0.8161x-1.6232(R2=0.99,P<0.05),数值分别为6.30~11.71μg·ind-1·h-1和1.22 ~2.16μg· mg-1·h-1,窒息点为4.18~6.87 mg·L-1.盐度10 ~40条件下,IO和SO随盐度的升高逐渐下降,回归方程分别为y=-0.0068x2 -0.1412x+21.702(R2=0.89,P<0.05)和y=-0.0013x2-0.0261x+4.0114( R2 =0.89,P<0.05),数值分别为4.98~17.73μg ·ind-1·h-1和0.92~3.56 μg·mg-1 ·h-1,窒息点为4.02~6.24 mg·L-1.对强壮箭虫与其他水生动物的耗氧率和窒息点进行比较得出,强壮箭虫是一种狭氧性浮游动物.  相似文献   

19.
In this study, we investigate the effects of endothelin-1 (ET-1) and insulin on the cellular activity of protein kinase FA/glycogen synthase kinase-3 (kinase FA/GSK-3) in rat adipocytes. The cellular activity of kinase FA/GSK-3 is inhibited to 50% of control within 30 min when cells are treated with 1 nM ET-1 at 37°C; in addition, significant inhibition to 60% of control is observed at as low as 1 pM ET-1. Conversely, ET-1 at concentrations up to 1 nM has no direct effect on purified kinase FA/GSK-3 in vitro. Immunoblotting analysis further reveals that the protein level of this kinase is not significantly changed when treated with 1 nM ET-1 for 30 min. Similar to ET-1, insulin as low as 10 nM can also induce inactivation of kinase FA/GSK-3 to 50% of control in adipocytes when processed under identical conditions. Most importantly, when treated with both insulin and ET-1, the activity of kinase FA/GSK-3 can be decreased only to 50% of control. Taken together, the results provide initial evidence that ET-1 and insulin may regulate this important multisubstrate/multifunctional protein kinase in a common signaling pathway in cells.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号