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[en] In this paper we solve the Einsteins' field equations for a spherically symmetric anisotropic fluid, with kinematic self-similarity of the first kind, in spacetimes (2+1)-dimensional. Considering a null radial pressure we show that the fluid collapses forming a black hole in the end, even if it is constituted by phantom energy. (author)

[en] During the Fukushima Daiichi nuclear accident in 2011, hydrogen explosions occurred in all units from Unit 1 to Unit 3. Consequently, one of the lessons learned from the Fukushima Daiichi accident is the necessity of implementing hydrogen control and mitigation strategies for most Nuclear Power Plants (NPPs). This paper focuses on the incorporation of Passive Autocatalytic Recombiners (PARs) during the design phase of a small modular Pressurized Water Reactor (SMR-PWR) project. The numerical analyses are conducted using the MELCOR v. 2.2 code. Two scenarios are compared: the Total Loss of Feed Water (TLOFW) severe accident with and without PARs. Saphiro’s diagram is utilized to investigate whether the mixture's composition (hydrogen, air, steam) is flammable for both scenarios. It has been observed that the inclusion of PARs leads to a reduction in hydrogen risk (detonative or deflagrative) as the final hydrogen concentration values fall below the flammability limit. This study is preliminary, and further research is required. (author)

[en] Recently Moffat showed that the Szafron inhomogeneous cosmological solution can lead to an accelerating in stationary period without a large initial vacuum energy and with Λ = 0 in the early universe near the Planck time, combined with an accelerating universe at late times, in the nonlinear regime with galaxy structure and voids, without need to introduce negative pressures or a cosmological constant. Here we present an inhomogeneous and anisotropic cosmological model, in 2+1 gravity, which satisfy all the energy conditions, although it generates an accelerated universe. We work in a 2+1 gravity scenario in order to simplify the equations system and to allow us to find analytical and simple solutions. Our propose is basically to improve our understanding on the role of inhomogeneities on the acceleration of the universe. (author)

[en] Published in summary form only

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[en] Urea fertiliser accounts for >50% of the total world N consumption; however, urea has been shown to have lower N use efficiency in many cropping and pasture systems compared to other N fertilizers, meaning that a large percentage of the applied fertilizer N is not being used for productive purposes and is essentially lost (Blennerhassett et al. 2006; Zaman et al., 2008;). After surface application, urea fertiliser or urea in animal manure, is quickly converted to ammonium (NH₄⁺) within 1 to 2 days of their application leading to a high pH and very high concentrations of NH₄⁺ around the urea granule or manure. The sharp rise in soil pH and NH₄⁺ concentration around urea granule/manure increases the likelihood of gaseous ammonia (NH₃) losses to the atmosphere. A wide range of NH₃ losses (10% to 56% of the applied N) have been reported under different agroecosystems (Zaman et al., 2013). Such heavy NH₃ losses have both environmental and economic implications. For example, emitted NH₃ causes environmental problems like eutrophication and soil acidification upon deposition on water and soil, respectively. Additionally, NH₃ acts as a secondary source of a powerful greenhouse gas nitrous oxide (N₂O) and thus contributes indirectly to global warming. Limited field studies have been conducted to measure NH₃ losses worldwide due to the lack of inexpensive and lowtech measuring technique. Many sophisticated methods, such as wind tunnels, cavity ring down spectroscopy and micrometeorological techniques, are already available, but these are expensive and require highly-skilled field technicians to operate. This makes them inaccessible for many developing countries and institutions that want to measure and know the level of NH₃ losses under different agricultural systems.