Simultaneous Regeneration of Two 160 Gbit/s WDM Channels in a Single Highly Nonlinear Fiber

We experimentally demonstrate simultaneous all-optical regeneration of two 160-Gbit/s wavelength-division multiplexed (WDM) channels in a single highly nonlinear fiber (HNLF). The multi-channel regeneration performance is confirmed by bit-error rate (BER) measurements. The receiver powers at a BER of 10-9 are improved by about 4.9 dB and 2.1 dB for the two channels, respectively. The BER performance is not degraded by the presence of a second channel. Mitigation of the inter-channel nonlinearities is achieved through bidirectional propagation.</p

Pricing and Sales Effort Decisions in a Closed-Loop Supply Chain Considering the Network Externality of Remanufactured Product

Considering the network externality of remanufactured product, this paper develops the Stackelberg game models in a closed-loop supply chain (CLSC) consisting of an original equipment manufacturer (OEM) and a retailer with dual sales channel under three scenarios, i.e., no sales effort (Model N), the retailer exerting sales effort (Model R) and the OEM exerting sales effort (Model M). The study investigates the pricing and sales effort decisions for CLSC members. The results show that: (1) Compared with no sales effort, the sales effort behavior can always improve the profits of the OEM and entire CLSC. The retailer’s profit can be improved in Model R, so OEM exerting sales effort could cause a loss for the retailer and the sales effort behavior can promote the sales of remanufactured products and further cannibalize the new product market. (2) Model M is more favorable to improve the profits of the OEM and entire CLSC, while the retailer prefers Model R. Model M is more beneficial for boosting the sales of remanufactured products. (3) As the network externality/consumer’s sensitivity of sales effort becomes more obvious, CLSC members exert more sales effort, and the OEM exerts more sales effort compared to the retailer. (4) Only when the retailer’s sales effort cost is much lower than the OEM sales effort cost is it that OEM could obtain more profit when the retailer exerts sales effort; then, the win-win situation between OEM and the retailer is achieved

Catastrophic behavior of aphid population dynamics: An analysis of swallowtail model

Catastrophe phenomena are frequent in insect ecology, especially in aphid populations. Complexity of this phenomenon urges different modeling frameworks other than traditional methodologies to understand the trajectories of their behavior. Situations like this can be best handled using catastrophe theory. A few numbers of experiments have been conducted to develop catastrophe models in insect ecology, especially for aphids, and most of them are based on cusp catastrophe theory which is a lower dimensional model. However few attempts using higher dimensional models such as swallowtail or butterfly theory to analyze aphid population dynamics are also exist. In this paper we tried to analyze a recently developed higher dimensional catastrophe theory model (APHIDSim) in order to identify catastrophe regions, and used independent data to identify if catastrophic behavior is observed in the data and consequently to further verify the model. Here we found that identifying catastrophe regions is possible using catastrophe theory model, and it can be used to analyze catastrophes in insect ecology by graphically interpreting the simulated results. Increasing of insect population is intrinsically catastrophic and catastrophes (jumps) occur between states even if the driving variables still change smoothly. The results further verified the previously developed model, and we suggest that insect management program developers should consider this phenomenon when they design the management strategies for insect controlling

Effect of the endosymbiont Regiella insecticola on an aphid parasitoid

International audienceAbstract The importance of secondary endosymbionts on the resistance to parasitoids is increasingly recognized. Compared with Hamiltonella defensa, our understanding of the role of Regiella insecticola in protecting hosts against parasitic wasps is not well documented. In this study, we conducted experiments to determine whether R. insecticola in Sitobion avenae (the English grain aphid) could confer resistance to a parasitoid, Aphelinus asychis Walker, a major natural enemy in aphid field populations. With the genetic background controlled using clones, our results showed that infected aphids were more likely to be parasitized by A. asychis. However, compared with the uninfected controls, the weight of emerged wasps within 24 hours was significantly lower from infected aphids, suggesting that R. insecticola negatively affected the growth of the developing parasitoid larvae, although no difference in emergence rate between the treatments and the control was detected. These results will help to increase understanding of the dynamics of host-parasite-symbiont interactions

Ecological impact of a secondary bacterial symbiont on the clones of Sitobion avenae (Fabricius) (Hemiptera: Aphididae)

Many insects harbor heritable endosymbionts, whether obligatory or facultative, and the role of facultative endosymbionts in shaping the phenotype of these species has become increasingly important. However, little is known about whether micro-injected endosymbionts can have any effects on aphid clones, which was measured using various ecological parameters. We examined the effects between symbiotic treatments and the vital life history traits generated by Regiella insecticola on the life table parameters of Sitobion avenae. The results showed that R. insecticola can decrease the intrinsic rate of increase (r), the finite rate of increase (lambda) and birth rate and can increase the mean generation times (T) of S. avenae clones, suggesting that R. insecticola may decelerate the normal development of the hosts. No significant differences of these parameters were observed between the examined Sitobion avenae clones, and the symbiont treatment by genotype interaction affected only the net reproduction rate R-0, pre-adult duration and total longevity but not the other parameters. Additionally, a population projection showed that R. insecticola decelerated the growth of the S. avenae clones. The evocable effects of R. insecticola on the S. avenae clones may have significant ramifications for the control of S. avenae populations under field/natural conditions

Assessment of Non-Consumptive Predation Risk of Coccinella septempunctata (Coleoptera: Coccinellidae) on the Population Growth of Sitobion miscanthi (Hemiptera: Aphididae)

How the non-consumptive effects (NCEs) of predators influence the development, survival, fecundity, and population growth of prey has not been well documented, which is the primary consideration for the compatibility of prey with its natural enemies in agricultural ecosystems. We herein employed the age-stage, two-sex life table to examine the NCEs of the predator Coccinella septempunctata on the life-history traits and population growth of prey Sitobion miscanthi via caged predator (prey co-existing with caged predator) and caged prey (predator co-existing with caged prey) treatments with daily different exposure times (i.e., 0 h (control), 12 h, and 24 h). The results indicated that the predation risk of a caged predator could reduce the first nymphal duration and net reproductive rate (R0) of S. miscanthi at 12 h, and the first nymphal duration, preadult duration, and mean generation time (T) at 24 h. However, the predation risk of the caged prey resulted in the prolongation of the pre-adult development time and total pre-reproductive period (TPRP) as well as lowered the intrinsic rate of increase (r), finite rate of increase (&#120582;), R0, life expectancy, and reproductive value of S. miscanthi after both 12 h and 24 h. Furthermore, the predation risk of both the caged predator and caged prey could increase the percent of winged morph at 24 h. These findings indicate that S. miscanthi could respond to the predation risk of the caged predator by either accelerating the developmental rate or reducing the net reproductive rate, while S. miscanthi might reduce their fitness in response to the predation risk of caged prey. Furthermore, S. miscanthi might also alter to winged morphs for dispersal under both of the above treatments. The findings obtained have practical ramifications for managing this economically important pest in wheat production with reduced insecticide applications

Indirect and direct interactions between grain aphid and parasitoid in the presence of symbiont Regiella insecticola

Abstract Background Aphids often harbor bacterial symbionts that confer resistance to biotic and abiotic stress. Previous studies have primarily examined the direct effects of symbiont infection on parasitoid success but less on aphid population dynamics under indirect parasitic situations, for example when exposed to parasitoid wasp odor. Deciphering this type of indirect effect is essential for understanding dynamics of insect ecosystems and communities and to improve IPM success. Methods We generated Sitobion avenae aphid clonal lines that are genetically identical but differ in Regiella insecticola infection. Then, the indirect odor effect of female parasitoid wasp Aphidius gifuensis (Ashmaed), one of its major natural enemies in the fields, was examined on the aphid lines fitness using different parasitoid densities. With these lines we also tested the direct effect of symbiont presence on aphid resistance against different parasitoid densities. Results Our study found fitness costs for the aphid line hosting Regiella, mainly via an increase in the development time and a reduction in population increase rate. Some of these fitness traits were influenced by the indirect exposure to parasitoid wasp odor with a density effect. Presence of the symbiont also reduced A. gifuensis parasitic success, increased the wasp development time and decreased its emergence weight with low effect of the parasitoid density used for parasitism. Conclusions These results showed that aphid population dynamic was mainly affected by the symbiont presence, but not by parasitoid odor. Symbiont presence also protected aphid from parasitism and affected parasitoid offspring weight and hence their future individual fertility and fitness