Research on the Properties of Periodic Solutions of Beverton⁃Holt Equation

Fractional linear maps have played a key role in mathematical biology,population dynamics,and other research areas.In this paper,a special kind of Ricatti map is studied in detail in order to determine the asymptotical behaviors of fixed points and periodic solutions.Making use of composition operation of maps and the methods of dynamical systems and qualitative theory,fixed points or periodic orbits are expressed precisely,average value of periodic solution is estimated concretely,and several different bounds are obtained for periodic solutions of the Beverton⁃Holt map when both intrinsic growth rate and carrying capacity change periodically.In addition,some sufficient conditions are given about the attenuation of periodic solution of the non⁃autonomous Beverton⁃Holt equation.Compared with present works in literature,our results about bounds of periodic solutions are more precise,and our proofs about the attenuation of periodic solution are more concise.

Effect and mechanism of high glucose on apoptosis and cell cycle arrest of islet β cells via p27 pathway

Objective:To study the effect of mechanism of high glucose on apoptosis and cell cycle arrest of isletβcells via p27 pathway.Methods:Islet INS-1 cells were cultured and divided into groups.The control group was treated with ordinary medium,the high glucose group was treated with high glucose medium containing 25mmol/L glucose,the high glucose+si-NC group was treated with high glucose medium and transfected with NC siRNA,and the high glucose+si-P27 group was treated with high glucose medium and transfected with p27 siRNA.After 24 hours treatment,MTS assay was used to detect the cell viability A490,TUNEL assay was used to detect apoptosis rate,flow cytometry was used to detect the cell cycle distribution and western blot was used to detect the expression levels of P27,caspase-8 and cyclinD1.Results:Compared with those in the control group,the A490,the ratio of S phase and G2/M phase as well as the expression level of CyclinD1 decreased,while the apoptosis rate,the ratio of G0/G1 phase as well as the expression levels of P27 and caspase-8 increased in the high glucose group(P<0.05);compared with those in the high glucose group,the A490,cell cycle as well as the expression levels of P27,caspase-8 and cyclinD1 were not different from those in the high glucose+si-NC group(P>0.05);compared with those in the high glucose group and high glucose+si-NC group,the A490,the ratio of S phase and G2/M phase as well as the expression levels of cyclinD1 increased,while the apoptosis rate,the ratio of G0/G1 phase as well as the expression levels of p27 and caspase-8 decreased in the high glucose+si-P27 group(P<0.05).Conclusion:The apoptosis and cell cycle arrest induced by high glucose are related to P27 pathway activation.

基于骨干网的数据中心网络服务规划设计

数据中心是云计算的核心,而当前基于电交换器、传统多级交换网络、集中放置与管理的数据中心架构无法满足未来云服务对高性能数据中心在可生存性、高可用性与设计灵活性等方面的要求。以网络可生存性和最小化网络代价为目标,针对数据中心的放置、服务路由及保护进行联合优化设计。首先通过设计ILP获取最优解。该ILP集成了p-cycle、服务量备份以及快速重路由等思想,分别针对单个链路或单个服务器损坏进行快速保护。然后进一步给出一种启发式算法,该算法包含数据中心的放置及服务路由和快速保护两大步骤。ILP和启发式两种方法最终都通过广泛的仿真实验进行了验证。

NAND flash service lifetime estimate with recovery effect and retention time relaxation

A service life model of NAND flash and threshold voltage shift process is proposed to calculate the service life and endurance.The relationships among achievable program/erase(P/E) cycles,recovery time,bad block rate and storage time are analyzed.The achievable endurance and service life of a NAND flash are evaluated based on a flash cell degradation and recovery model by varying recovery time,badblock rate,and storage time.It is proposed to improve the service lifetime of solid state disk by both relaxing the bad block rate limitation and retention time while extending the recovery time.The results indicate that endurance can be improved by 17 times if the storage time guarantee is reduced from 10 a to 1 a with 105 s recovery time inserted between cycles.

Root Cluster Formation and Citrate Exudation of White Lupin （Lupinus albus L.） as Related to Phosphorus Availability

Abstract: A split-root system was used to investigate whether the external or internal P concentration controls root cluster formation and citrate exudation in white lupin (Lupinus albus L.) grown under controlled conditions. In spite of low P concentrations in the shoots and roots of the -P plant, its dry weight was not reduced compared with the +P plant. Supplying external P (0.25 mmol/L) to one root half resulted in an increase in P concentration not only in the shoot, but also in the P-deprived root half, indicating P cycling within the plants. Omitting P from both split-root pots stimulated root cluster formation in both root halves, whereas P supply to one root half stimulated root cluster formation at the beginning of the treatment. Neither P supply to just one root half continuously nor resupply of P to one root half after 19 d of P starvation inhibited root cluster formation on the P-deprived side, although the concentration of P in this root half and shoot increased markedly. The results indicate that root cluster formation in L. albus is controlled by both shoot and root P concentrations. The rates of citrate exudation by both root halves with P deficiency were higher than those of the one root half supplied with P only. In the treatment with one root half supplied with P, the rates of citrate exudation by either the P-supplied or -deprived root halves were almost the same, regardless of P concentration in the roots. The results suggest that internal P concentration controls root cluster formation and citrate exudation in white lupin, but these processes may be regulated by different mechanisms.

Soil Enzyme Activities on Eroded Slopes in the Sichuan Basin, China

Determining how soil erosion affects enzyme activity may enhance our understanding of soil degradation on eroded agricultural landscapes. This study assessed the changes in enzyme activity with slope position and erosion type by selecting water and tillage erosion-dominated slopes and performing analyses using the 1376s technique. The 137Cs data revealed that soil loss occurred in the upper section of the two eroded slope types, while soil accumulation occurred in the lower section. The invertase activity increased downslope and exhibited a pattern similar to the 137Cs data. The spatial patterns of urease and alkaline phosphatase activities were similar to the 137Cs inventories on the water and tillage erosion-dominated slopes, respectively. On both the eroded slope types, the invertase activity and soil organic carbon content were correlated, but no correlation was observed between the alkaline phosphatase activity and total phosphorus content. Nevertheless, the urease activity was correlated with the total nitrogen content only on the water erosion-dominated slopes. The enzyme activity-to-microbial biomass carbon ratios indicated high activities of invertase and urease but low activity of phosphatase on the water erosion-dominated slopes compared with the tillage erosion-dominated slopes. Both the invertase activity and the invertase activity-to-microbial biomass carbon ratio varied with the slope position. Changes in the urease activity-to-microbial biomass carbon ratio were significantly affected by the erosion type. These suggested that the dynamics of the invertase activity were linked to soil redistribution on the two eroded slope types, whereas the dynamics of the urease and alkaline phosphatase activities were associated with soil redistribution only on the water or tillage erosion-dominated slopes, respectively. The erosion type had an obvious effect on the activities of invertase, urease and alkaline phosphatase. Soil redistribution might influence the involvement of urease in the N cycle and alkaline phosphatase in the P cycle. Thus, enzyme activity-to-microbial biomass ratios may be used to better evaluate microbiological activity in eroded soils.

WDM网络中基于p-path和p-cycle的混合保护方案

为设计一种针对光网络中单链路失效的波长资源利用率高的快速保护算法,该文分析了完全预配置保护对预配置结构的约束,对比了预配置保护环(p-cycle)和预配置保护通道(p-path)保护性能,提出了p-cycle和p-path混合配置保护方案。该方案按比例选取p-cycle和p-path作为预配置结构,通过求解整数线性规划(ILP)方程得到优化配置方案。使用COST 239网络拓扑进行的仿真实验表明:相同网络负载和波长资源条件下,p-cycle和p-path混合保护方案比p-cycle独立保护方案的网络冗余度可以优化10%,同时保留了p-cycle快速保护的优点。