Применение метода контрольных возмущений для определения характерных узлов присоединения комплексной нагрузки при расчетах динамической устойчивости

Рассматривается влияние способа замещения комплексной нагрузки на характер электромеханических переходных процессов в электрических системах (ЭС) от действия больших возмущений. Показано, что установить общие рекомендации относительно способа замещения нагрузки в сложных ЭС затруднительно. Предлагается для опреде­ления характерных узлов нагрузки, оказывающих существенное влияние на характер динамического перехода, применять известный метод контрольных возмущений. Приводятся результаты сравнительных расчетов с использованием предлагаемой методики

Spiders do not escape reproductive manipulations by Wolbachia

<p>Abstract</p> <p>Background</p> <p>Maternally inherited bacteria that reside obligatorily or facultatively in arthropods can increase their prevalence in the population by altering their hosts' reproduction. Such reproductive manipulations have been reported from the major arthropod groups such as insects (in particular hymenopterans, butterflies, dipterans and beetles), crustaceans (isopods) and mites. Despite the observation that endosymbiont bacteria are frequently encountered in spiders and that the sex ratio of particular spider species is strongly female biased, a direct relationship between bacterial infection and sex ratio variation has not yet been demonstrated for this arthropod order.</p> <p>Results</p> <p>Females of the dwarf spider <it>Oedothorax gibbosus </it>exhibit considerable variation in the sex ratio of their clutches and were infected with at least three different endosymbiont bacteria capable of altering host reproduction i.e. <it>Wolbachia</it>, <it>Rickettsia </it>and <it>Cardinium</it>. Breeding experiments show that sex ratio variation in this species is primarily maternally inherited and that removal of the bacteria by antibiotics restores an unbiased sex ratio. Moreover, clutches of females infected with <it>Wolbachia </it>were significantly female biased while uninfected females showed an even sex ratio. As female biased clutches were of significantly smaller size compared to non-distorted clutches, killing of male embryos appears to be the most likely manipulative effect.</p> <p>Conclusions</p> <p>This represents to our knowledge the first direct evidence that endosymbiont bacteria, and in particular <it>Wolbachia</it>, might induce sex ratio variation in spiders. These findings are pivotal to further understand the diversity of reproductive phenotypes observed in this arthropod order.</p

Geophila erythrocarpa (Rubiaceae), a new species from D.R.Congo and Zambia

The species Geophila erythrocarpa (Rubiaceae) is described and illustrated. The new species is restricted to dry, dense forests of the Katanga province in D.R.Congo and the adjoining Copperbelt province in Zambia. The species is similar to and in the herbarium easily confused with G. obvallata from which it most clearly differs in having red instead of blue or black fruits. In flowering state, the two species can be separated by differences in calyx morphology. The new species shares the red-coloured fruits with G. afzelii, but differs from this species in the undivided stipules, the fewer-flowered inflorescences with smaller bracts, and details of the leaf coloration. The new species is further compared with all other Geophila species reported from Zambia and D.R.Congo whereby G. obtusifolia is reduced to synonymy under G. renaris and G. aschersoniana is reduced to synonymy under G. obvallata. An IUCN conservation assessment has been made and the species is provisionally assessed as Endangered, based on its restricted area of occupancy, the small number of known locations, and the continuing decline in extent and quality of its habitat. © 2011 Nationaal Herbarium Nederland.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Comparative genomic study of arachnid immune systems indicates loss of beta-1,3-glucanase-related proteins and the immune deficiency pathway

Analyses of arthropod genomes have shown that the genes in the different innate humoral immune responses are conserved. These genes encode proteins that are involved in immune signalling pathways that recognize pathogens and activate immune responses. These immune responses include phagocytosis, encapsulation of the pathogen and production of effector molecules for pathogen elimination. So far, most studies have focused on insects leaving other major arthropod groups largely unexplored. Here, we annotate the immune-related genes of six arachnid genomes and present evidence for a conserved pattern of some immune genes, but also evolutionary changes in the arachnid immune system. Specifically, our results suggest that the family of recognition molecules of beta-1,3-glucanase-related proteins (GRPs) and the genes from the immune deficiency (IMD) signalling pathway have been lost in a common ancestor of arachnids. These findings are consistent with previous work suggesting that the humoral immune effector proteins are constitutively produced in arachnids in contrast to insects, where these have to be induced. Further functional studies are needed to verify this. We further show that the full haemolymph clotting cascade found in the horseshoe crab is retrieved in most arachnid genomes. Tetranychus lacks at least one major component, although it is possible that this cascade could still function through recruitment of a different protein. The gel-forming protein in horseshoe crabs, coagulogen, was not recovered in any of the arachnid genomes; however, it is possible that the arachnid clot consists of a related protein, spatzle, that is present in all of the genomes

Gender differences and game-based learning in secondary education

In the Netherlands, differences in school motivation and performance between boys and girls are a major issue in political debates. In the first years of secondary education in the Netherlands, boys tend to underachieve and to be disengaged from school. Game-based learning might improve the school motivation and performance of both boys and girls. In two studies with game-based learning, gender differences were examined in students' school motivation and learning outcomes. Both boys and girls showed an increase in motivation and learning outcomes. Only in the second study about a digital role-play citizenship game, boys additionally showed a larger increase in media literacy than girls. This means that game-based learning showed potential to solve the so-called boys problem in Dutch secondary education