Effect of AVR and PSS on Power System Transient Stability with Different Wind Generation Technologies

In the last decade, wind generation has been the fastest growing energy source globally. However, higher penetration of wind energy into existing power networks raises concern for power system operators and regulators. In this paper, we investigate the effect of wind farms employing doubly-fed induction generators (DFIGs) on the transient stability of power systems. We carried out simulations to demonstrate and compare the transient performance of the standard 3-machine 9-bus system with and without wind power integration during a fault. We analyzed the generator technology mentioned, replacing one synchronous generator in the system. We also analyzed the mentioned system after introducing the automatic voltage regulators (AVR) and power system stabilizers (PSS) into the system. We simulated the system using DIgSILENT PowerFactory. Our results show that a better transient performance is achieved with the inclusion of DFIGs in the system. There is also a further improvement of the transient stability after including both the AVR and PSS in the simulations. Keywords: Squirrel cage induction generators, Doubly-fed induction generators, Transient stability, Automatic Voltage Regulator, Power System Stabilizer

Effect of Aflatoxin B-1 on Course of Infection of Trypanosoma congolense in Mice

Mycotoxins as secondary metabolites are known to be common contaminants of both human food and animal feed. If ingested in minute but regular doses, they are known to cause suppression of the immune system and therefore, alter pathogenesis of many infectious diseases. Trypanosoma congolense an intravascular parasite is the most important cause of African animal trypanosomosis. The aim of this work was to investigate the effect of aflatoxin B-1, a common mycotoxin on progression and response of T. congolense to chemotherapy. Female Swiss white mice were intra-peritoneally injected with 0.05mg/kg body weight aflatoxin B-1 every after 3 days upto 10 times and on the 21st day were infected with T. congolense. Parasitological parameters including weight, packed cell volume and parasitaemia levels of aflatoxin B-1-injected-T. congolense-infected mice were compared with those of T. congolense-infected mice. ANOVA and mean separation were used to determine differences between the test and control mice. It was observed that there was significant difference (p?0.05) in body weight and mean death time but no significant difference in packed cell volume. It was concluded that aflatoxin B-1 has an effect on pathogenesis of T. congolense. Key words: Trypanosoma congolense, Aflatoxin B-1, progression, chemotherap

Cattle genome-wide analysis reveals genetic signatures in trypanotolerant N'Dama

Abstract Background Indigenous cattle in Africa have adapted to various local environments to acquire superior phenotypes that enhance their survival under harsh conditions. While many studies investigated the adaptation of overall African cattle, genetic characteristics of each breed have been poorly studied. Results We performed the comparative genome-wide analysis to assess evidence for subspeciation within species at the genetic level in trypanotolerant N’Dama cattle. We analysed genetic variation patterns in N’Dama from the genomes of 101 cattle breeds including 48 samples of five indigenous African cattle breeds and 53 samples of various commercial breeds. Analysis of SNP variances between cattle breeds using wMI, XP-CLR, and XP-EHH detected genes containing N’Dama-specific genetic variants and their potential associations. Functional annotation analysis revealed that these genes are associated with ossification, neurological and immune system. Particularly, the genes involved in bone formation indicate that local adaptation of N’Dama may engage in skeletal growth as well as immune systems. Conclusions Our results imply that N’Dama might have acquired distinct genotypes associated with growth and regulation of regional diseases including trypanosomiasis. Moreover, this study offers significant insights into identifying genetic signatures for natural and artificial selection of diverse African cattle breeds