主拟-Baer模

In this paper, we give the equivalent characterizations of principally quasi-Baer modules, and show that any direct summand of a principally quasi-Baer module inherits the property and any finite direct sum of mutually subisomorphic principally quasi-Baer modules is also principally quasi-Baer. Moreover, we prove that left principally quasi-Baer rings have Morita invariant property. Connections between Richart modules and principally quasi-Baer modules are investigated.     

Qualitative analysis of a SIR epidemic model with saturated treatment rate

On account of the effect of limited treatment resources on the control of epidemic disease, a saturated removal rate is incorporated into Hethcote’s SIR epidemiological model (Hethcote, SIAM Rev. 42:599–653, 2000). Unlike the original model, the model has two endemic equilibria when R ₀<1. Furthermore, under some conditions, both the disease free equilibrium and one of the two endemic equilibria are asymptotically stable, i.e., the model has bistable equilibria. Therefore, disease eradication not only depends on R ₀ but also on the initial sizes of all sub-populations. By the Poincaré-Bendixson theorem, Poincaré index, center manifold theorem, Hopf bifurcation theorem and Lyapunov-Lasalle theorem, etc., the existence and asymptotical stability of the equilibria, the existence, stability and direction of Hopf bifurcation are discussed, respectively.     

Optimal Production Planning in a Stochastic Manufacturing System with Long-Run Average Cost

This paper is concerned with the optimal production planning in a dynamic stochastic manufacturing system consisting of a single machine that is failure prone and facing a constant demand. The objective is to choose the rate of production over time in order to minimize the long-run average cost of production and surplus. The analysis proceeds with a study of the corresponding problem with a discounted cost. It is shown using the vanishing discount approach that the Hamilton–Jacobi–Bellman equation for the average cost problem has a solution giving rise to the minimal average cost and the so-called potential function. The result helps in establishing a verification theorem. Finally, the optimal control policy is specified in terms of the potential function.     

线性不确定系统的稳定控制鲁棒界和多级稳定鲁棒控制

利用李雅普诺夫稳定性理论研究了线性不确定系统的稳定鲁棒控制问题,得到结果“任何一个稳定控制都是具有一定稳定鲁棒界的稳定控制”.进一步地,根据系统的不确定量的范围,设计了多级稳定鲁棒控制策略.最后给出一个例子说明设计步骤的可行性.     

Oldhamine A, a novel alkaloid from Daphniphyllum oldhami

Oldhamine A, a novel alkaloid with an unusual cyclopentadienyl anion in the fused-pentacyclic skeleton was isolated from the twigs of Daphniphyllum oldhami. The structure of oldhamine A was elucidated based on the spectroscopic data and the single-crystal X-ray diffraction crystallography. It is the first X-ray diffraction of the Daphniphyllum alkaloids with nitrogen-containing two pentacyclic rings. The inter-conversion between cyclopentadienyl anion and conjugated enolic unit was also conducted.     

Construction of Multi-ribozyme Expression System and Its Characterization of Cleavage on the MDR1/MRP1 Double Target Substrate in vitro

To improve catalytic activity of ribozyme on its substrate,the multi-ribozyme expression system was designed and constructed from 20 cis-acting hammerhead ribozymes undergoing self-cleavage with 10 trans-acting hammerhead ribozymes inserted altematively regularly and the plasmid of pGEM-MDRI/MRPI used to transcribe the M DRI/MRPI(196/210) substrate containing double target sites was also constructed by DNA recombination.Endonuclease digestion analysis and DNA sequencing indicate all the recombinant plasmids were correct.The cleavage activities were evaluated for the multi-ribozyme expression system on the MDR1/MRP1 substrate in the cell free system.The results demonstrate that the cis-acting hammerhead ribozymes in the multi-ribozyme expression system were able to cleave themselves and the 72 nt of 196Rz and the 71 nt of 210Rz trans-acting hammerhead ribozymes were liberated effectively,and the trans-acting hammerhead ribozymes released were able to act on the MDR1/MRP1 double target RNA substrate and cleave the target RNA at specific sites effectively.The multiribozyme expression system of the [Coat'A196Rz/Coat'B210Rz]5 is more significantly superior to that of the [Coat'A 196Rz/Coat'B210Rz]1 in cleavage of RNA substrate.The fractions cleaved by [Coat'A196Rz/Coat'B210Rz]5 on the MDR1/MRP1 substrate for 8 h at observed temperatures showed no marked difference.The studies of Mg2+ on cleavage efficiency indicate that cleavage reaction is dependent on Mg2+ ions concentration.The plot of Ig(kobs) vs.Igc(Mg2+) displays a linear relationship between 2.5 mmol/L and 20 mmol/L Mg2..It suggests that Mg2+ ions play a crucial role in multi-ribozyme cleavage on the substrate.     

催化极谱法测定产妇、新生儿全血和胎盘中的微量钼

在０－２２５ ｍｏｌ／ＬＨ２ＳＯ４ － ０－２５ ％ 苯羟乙酸－ ３ ％ ＫＣ１Ｏ３ 底液体系中, 钼有一个灵敏的极谱催化波, 用于测定临床样品中的Ｍｏ , 其峰电位－ ０－３０ Ｖ（ 对Ｓ－Ｃ－Ｅ） 。２３ 种共存离子的含量低于允许存在量, 不干扰测定。方法的检出限１－４ ×１０ － １０ ｇ／ｍＬ, 线性范围０－００１ ～０－５００ ｍｇ／Ｌ, １１ 次测定的相对标准偏差为１－８９ ％ ～３－４２ ％ , 标准回收率９７－２ ％ ～１０２－８ ％ 。方法简便、快速。测定了西宁市３５ 例分娩孕妇全血、新生儿脐血和胎盘中的钼, 获得了理想的结果。     

Study on the Activity and Kinetic Characteristics of Glucoamylase in W/O Microemulsion Systems

The activity and kinetic characteristics of glucoamylase has been investigated in W/0 microemulsion systems of AOT/isooctane/buffer, CTAB/isooctane/l-pentanol/buffer and TX-100/ibooctane/I-pentanol/buffer, and compared with that in aquous solution. The effect of various parameters, such as pH optimum, To ptimum and water content, on the activity of the enzyme in microemulsion was determined. The results obtained show that the structure of the microemulsion has strong effect on enzyme activity compared to the k_cat, in aquous solution, the apparent turnover number k'_cat values were decreased in AOT, TX- 100 based system, and in creased in CTAB based system.     

Use of Capillary Electrophoresis in the Study of Interaction between dsDNA and Drug Molecules

The advantages of berberine such as the anticancer1, antiinflammatory2 and no side effects of camptothecin1, have promoted the research in the mechanism of berberine with macrobiomolecules. In general, three different points of view have been presented on…     

Multiplicity of Positive Solutions for Critical Fractional Equation Involving Concave–Convex Nonlinearities and Sign-Changing Weight Functions

Mediterranean Journal of Mathematics - This paper is devoted to study a class of fractional equations with critical exponent, concave nonlinearity and sign-changing weight functions. By means of...