87 research outputs found
Автономизация вузов в Украине как драйвер перехода к образовательной модели медицинского предпринимательского университета
УНИВЕРСИТЕТ 3.0ПРЕДПРИНИМАТЕЛЬСКИЕ КОМПЕТЕНЦИИОБРАЗОВАНИЕ МЕДИЦИНСКОЕСТУДЕНТЫ МЕДИЦИНСКИХ УЧЕБНЫХ ЗАВЕДЕНИЙОБРАЗОВАТЕЛЬНЫЕ МОДЕЛИПРЕДПРИНИМАТЕЛЬСКИЕ УНИВЕРСИТЕТЫУКРАИН
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary
The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6&deg; cgmLat) and Longyearbyen (75.2&deg; cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5&deg; cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. <br><br> During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 <I>R<sub>E</sub></I> mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H<sup>+</sup> and O<sup>+</sup> ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. <br><br> The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2&deg; during ~5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse
IMF effect on the polar cap contraction and expansion during a period of substorms
Peer reviewe
Island properties dominate species traits in determining plant colonizations in an archipelago system
The extrinsic determinants hypothesis emphasizes the essential role of environmental heterogeneity in species' colonization. Consequently, high resident species diversity can increase community susceptibility to colonizations because good habitats may support more species that are functionally similar to colonizers. On the other hand, colonization success is also likely to depend on species traits. We tested the relative importance of environmental characteristics and species traits in determining colonization success using census data of 587 vascular plant species collected about 70 yr apart from 471 islands in the archipelago of SW Finland. More specifically, we explored potential new colonization as a function of island properties (e.g. location, area, habitat diversity, number of resident species per unit area), species traits (e.g. plant height, life-form, dispersal vector, Ellenberg indicator values, association with human impact), and species' historical distributions (number of inhabited islands, nearest occurrence). Island properties and species' historical distributions were more effective than plant traits in explaining colonization outcomes. Contrary to the extrinsic determinants hypothesis, colonization success was neither associated with resident species diversity nor habitat diversity per se, although colonization was lowest on sparsely vegetated islands. Our findings lead us to propose that while plant traits related to dispersal and establishment may enhance colonization, predictions of plant colonizations primarily require understanding of habitat properties and species' historical distributions.Peer reviewe
Observations of an auroral streamer in a double oval configuration
During the late evening and night of 14 September 2004, the nightside
auroral oval shows a distinct double oval configuration for several hours
after a substorm onset at ~18:45 UT. This structure is observed both
by the IMAGE satellite optical instruments focusing on the Southern
Hemisphere, and by the MIRACLE ground-based instrument network in
Scandinavia. At ~21:17 UT during the recovery phase of the substorm,
an auroral streamer is detected by these instruments and the EISCAT radar,
while simultaneously the Cluster satellites observe a bursty bulk flow in
the conjugate portion of the plasma sheet in the magnetotail. Our combined
data analysis reveals significant differences between the ionospheric
equivalent current signature of this streamer within a double oval
configuration, as compared to previously studied streamer events without
such a configuration. We attribute these differences to the presence of an
additional poleward polarization electric field between the poleward and the
equatorward portions of the double oval, and show with a simple model that
such an assumption can conceptually explain the observations. Further, we
estimate the total current transferred in meridional direction by this
recovery phase streamer to ~80 kA, significantly less than for
previously analysed expansion phase streamer events. Both results indicate
that the development of auroral streamers is dependent on the ambient
background conditions in the magnetosphere-ionosphere system. The auroral
streamer event studied was simultaneously observed in the conjugate Northern
and Southern Hemisphere ionosphere
Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments
Bronchopulmonary dysplasia: clinical aspects and preventive and therapeutic strategies
Abstract Background Bronchopulmonary dysplasia (BPD) is the result of a complex process in which several prenatal and/or postnatal factors interfere with lower respiratory tract development, leading to a severe, lifelong disease. In this review, what is presently known regarding BPD pathogenesis, its impact on long-term pulmonary morbidity and mortality and the available preventive and therapeutic strategies are discussed. Main body Bronchopulmonary dysplasia is associated with persistent lung impairment later in life, significantly impacting health services because subjects with BPD have, in most cases, frequent respiratory diseases and reductions in quality of life and life expectancy. Prematurity per se is associated with an increased risk of long-term lung problems. However, in children with BPD, impairment of pulmonary structures and function is even greater, although the characterization of long-term outcomes of BPD is difficult because the adults presently available to study have received outdated treatment. Prenatal and postnatal preventive measures are extremely important to reduce the risk of BPD. Conclusion Bronchopulmonary dysplasia is a respiratory condition that presently occurs in preterm neonates and can lead to chronic respiratory problems. Although knowledge about BPD pathogenesis has significantly increased in recent years, not all of the mechanisms that lead to lung damage are completely understood, which explains why therapeutic approaches that are theoretically effective have been only partly satisfactory or useless and, in some cases, potentially negative. However, prevention of prematurity, systematic use of nonaggressive ventilator measures, avoiding supraphysiologic oxygen exposure and administration of surfactant, caffeine and vitamin A can significantly reduce the risk of BPD development. Cell therapy is the most fascinating new measure to address the lung damage due to BPD. It is desirable that ongoing studies yield positive results to definitively solve a major clinical, social and economic problem
Dynamic Phenotypic Clustering in Noisy Ecosystems
In natural ecosystems, hundreds of species typically share the same environment and are connected by a dense network of interactions such as predation or competition for resources. Much is known about how fixed ecological niches can determine species abundances in such systems, but far less attention has been paid to patterns of abundances in randomly varying environments. Here, we study this question in a simple model of competition between many species in a patchy ecosystem with randomly fluctuating environmental conditions. Paradoxically, we find that introducing noise can actually induce ordered patterns of abundance-fluctuations, leading to a distinct periodic variation in the correlations between species as a function of the phenotypic distance between them; here, difference in growth rate. This is further accompanied by the formation of discrete, dynamic clusters of abundant species along this otherwise continuous phenotypic axis. These ordered patterns depend on the collective behavior of many species; they disappear when only individual or pairs of species are considered in isolation. We show that they arise from a balance between the tendency of shared environmental noise to synchronize species abundances and the tendency for competition among species to make them fluctuate out of step. Our results demonstrate that in highly interconnected ecosystems, noise can act as an ordering force, dynamically generating ecological patterns even in environments lacking explicit niches
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