Frequencies of wave packets of whistler-mode chorus inside its source region: a case study

Whistler-mode chorus is a structured wave emission observed in the Earth's magnetosphere in a frequency range from a few hundreds of Hz to several kHz. We investigate wave packets of chorus using high-resolution measurements recorded by the WBD instrument on board the four Cluster spacecraft. A night-side chorus event observed during geomagnetically disturbed conditions is analyzed. We identify lower and upper frequencies for a large number of individual chorus wave packets inside the chorus source region. We investigate how these observations are related to the central position of the chorus source which has been previously estimated from the Poynting flux measurements. We observe typical frequency bandwidths of chorus of approximately 10% of the local electron cyclotron frequency. Observed time scales are around 0.1 s for the individual wave packets. Our results indicate a lower occurrence probability for lower frequencies in the vicinity of the central position of the source compared to measurements recorded closer to the outer boundaries of the source. This is in agreement with recent research based on the backward wave oscillator theory

Structure and properties of the intercalation compound FexTiTe2

The FexTiTe2 system, which belongs to the class of materials with the electronic spectrum containing below the Fermi level the band of localized states with a strong temperature dependence of the band width, has been investigated experimentally. Heating of the material leads to a broadening of the band of localized states. When the top of this band crosses with the Fermi level, the effect of retrograde solubility is observed in the system; i. e., the metal precipitates to the composition ensuring the absence of increase in the Fermi energy during heating. The influence of the band of localized states on the structure of the material and its magnetic and electrical properties has been analyzed. © 2013 Pleiades Publishing, Ltd

Native and Activated Hepatic Stellate Cells Stimulate Liver Regeneration in Rats After Partial Hepatectomy and 2-Acetylaminofluorene Injection

© 2016, Springer Science+Business Media New York.One the current challenges of modern hepatology is to find new approaches to stimulate liver regeneration and to find new methods for liver disease treatment. Cell therapies, which are based on using regional stem cells for disease treatment, are under active development. However, studies, devoted to their transplantation, are currently scarce. In recent years, hepatic stellate cells are considered to be hepatic stem cells. It is known that activated hepatic stellate cells can transdifferentiate into myofibroblasts and lead to liver fibrosis. The aim of our work was to study the influence of native and activated hepatic stellate cells in vivo by lead nitrate injection after transplantation into partial hepatectomized rats, which is considered to be a classical model to study liver regeneration. Injection of 2-acetylaminofluorene (AAF), which selectively eliminates hepatocyte proliferation, was used to understand the hepatic stellate cells role in liver regeneration process better. Our results suggest that transplanted native and activated hepatic stellate cells can differentiate into hepatocyte-like cells and positively influence liver regeneration without inducing liver fibrosis

Observations of the relationship between frequency sweep rates of chorus wave packets and plasma density

International audience[1] Chorus emissions are generated by a nonlinear mechanism involving wave‐particle interactions with energetic electrons. Discrete chorus wave packets are narrowband tones usually rising (sometimes falling) in frequency. We investigate frequency sweep rates of chorus wave packets measured by the Wideband data (WBD) instrument onboard the Cluster spacecraft. In particular, we study the relationship between the sweep rates and the plasma density measured by the WHISPER active sounder. We have observed increasing values of the sweep rate for decreasing plasma densities. We have compared our results with results of simulations of triggered emissions as well as with estimates based on the backward wave oscillator model for chorus emissions. We demonstrate a reasonable agreement of our experimental results with theoretical ones. Citation: Macúšová, E., et al. (2010), Observations of the relationship between frequency sweep rates of chorus wave packets and plasma density

Potential Distribution of the Invasive Species Metcalfa pruinosa (Hemiptera, Flatidae) and Perspectives of its Classical Biocontrol in Ukraine

The study used GIS software and climate projections to assess the distribution potential of the citrus planthopper Metcalfa pruinosa (Say, 1830) in Ukraine, taking into account global climate change. The model showed that climatic conditions in Ukraine meet the requirements of the species in the European part of its range, considering various indicators such as the sum of active temperatures, mean annual temperature and precipitation. The whole territory of Ukraine could potentially be a range for M. pruinosa due to suitable climatic conditions and the presence of host plants, with Zakarpattia, Crimea and the forest and woodland and steppe zones of Ukraine being the most favourable. Current phytosanitary measures are not sufficient to prevent its spread and a pest management system is needed to reduce the damage. The parasitoid Neodryinus typhlocybae (Ashmead, 1893) (Hymenoptera, Dryinidae) from North America could serve as a classical biological control agent, and suitable areas in southern Ukraine have been identified using GIS modelling. To manage the risk effectively, it is recommended that M. pruinosa be added to the list of regulated, non-quarantined pests in Ukraine