Search

Over the past decades, the Magpie, which has ecological and behavioral flexibility, has colonized many cities. In this study, we examine the effect of urban disturbance on nesting density of the Magpie and nest height in a city in the south-eastern Baltic region. The studies were carried out in Kaliningrad (54°43’N, 20°30’E) during the leafless period in 2018–2021 in green residential areas with a predominance of 5-storey buildings (“residential area”) and low-rise individual housing areas (“individual houses”). In the residential area, nest counts were carried out separately in the central part of the city and outside the city center. Based on literature data on urban populations of the Magpie in other cities, we predict that: (1) in the central part of the city there will be a higher nesting density of magpies and (2) in the central part of the city, nests will be located higher than outside the central part of the city. The results obtained did not confirm these assumptions. The average nesting density in residential areas in the city center and outside the city center was virtually the same. And, in addition, in the residential area in the city center, nests were on average located lower than in the residential area outside the central part of the city, but the differences were not statistically significant and the median values of these city zones coincide. The work also provides data on the placement of nests on various types of trees and shrubs. The Hooded crow, being the main predator and competitor of the Magpie, shares the same habitats in Kaliningrad. This coexistence could potentially slow down the increase in Magpie nesting density, especially in the residential area of the city centre, where the nesting density of the Hooded crow is significantly higher than outside the city centre. [ABSTRACT FROM AUTHOR]

The restart of the Transient Reactor Test facility (TREAT) will once again provide the capability for rapid transient testing of fuel concepts. Under the auspices of the U.S. Department of Energy's Office of Material Management and Minimization, research is underway to assess the feasibility of converting the current high-enriched uranium (HEU) fuel in TREAT to low-enriched uranium (LEU) fuel. The LEU concept retains the fuel process that results in micrometer-sized UO2 fuel grains dispersed in a graphite moderator matrix. The LEU fuel design includes more 238U, which fundamentally changes the feedback mechanisms in the fuel. To explore the effects of conversion on a pulse transient, a simplified semi-infinite TREAT fuel element model of both the HEU and proposed LEU configurations was simulated using MAMMOTH with the requisite multiscale and multiphysics coupling. The developed method incorporates fission energy deposition at microscale locations from the Mesoscale Atomistic Glue Program for Integrated Execution (Magpie), heterogeneity effects from the microscale model in the form of time lag, and independent feedback temperature sources from the microscale fuel grain model and surrounding moderator. The fuel grain size was varied along with temperature feedback sources to explore the feedback mechanisms. Significant differences between fuel and graphite temperatures were found to develop for transients with large energy depositions, for large fuel grains, and for fission-fragment irradiated graphite. These differences in temperature do not influence the feedback for HEU fuel but have a significant effect on LEU fuel. The difference between HEU and LEU fuel is caused by the fuel temperature feedback coefficient for LEU fuel that is roughly 20% of the graphite temperature feedback coefficient. The immediate equilibrium assumption is invalid for LEU fuel in certain TREAT operating regimes. As the conversion of TREAT to LEU fuel aims to conserve HEU capabilities, MAMMOTH simulations of the LEU model explore the effects of matching the same period, peak power density, and deposited energy of the HEU model. The same pulse shape was not achievable due to the feedback mechanism changes. [ABSTRACT FROM AUTHOR]

Size and structure of birds’ nests can arise from evolutionary trade-offs between benefits, such as insulation from unfavourable conditions, maintenance of eggs or chicks, security against predation, and costs, such as energy spent in construction of the nest and the risk of predation in more visible nests. The relationships between nest characteristics and breeding success and survival probabilities of Eurasian magpie (Pica pica) eggs and nestlings were studied in Baghbadaran, central Iran during the 2008 and 2010 breeding seasons. Nesting success was modelled to assess the relationships between nest parameters and the probability of daily nest survival. Mean clutch and brood size, hatching, fledging and breeding success did not vary significantly between the two years. Mean internal diameter, external diameter, distance to feeding location and distance to open areas varied significantly between the two study years. Daily nest survival rate for both years (2008 and 2010) was 0.98 ± 0.002. Nest size and status of nests, defined as old or newly established nests, were the best factors predicting probabilities of nest survival. Nests with small internal diameters had higher overall nest productivity. Nest height was positively correlated with both fledging success and breeding success. Our results agree with previous findings that have shown that magpie pairs with large nests provided their nestlings with higher quality food compared with pairs with smaller nests and so nest size was an indicator of parental ability. Nest height is also recognized as an important determinant of nest predation, mostly because it may affect nest detectability and accessibility. [ABSTRACT FROM AUTHOR]