193 research outputs found
The European and Slovenian transport market of oil and oil derivatives during the Coronavirus and the war in Ukraine
No full textNonlinear stability of soliton solutions for massive tensor-multiscalar theories
No full textThe aim of this paper is to study the stability of solitonlike static solutions via nonlinear simulations in the context of a special class of massive tensor-multiscalar theories of gravity whose target space metric admits Killing field(s) with a periodic flow. We focused on the case with two scalar fields and maximally symmetric target space metric, as the simplest configuration where solitonic solutions can exist. In the limit of zero curvature of the target space κ=0 these solutions reduce to the standard boson stars, while for κ≠0 significant deviations can be observed; both qualitative and quantitative. By evolving these solitonic solutions in time, we show that they are stable for low values of the central scalar field ψc while instability kicks in with the increase of ψc. As expected from the study of the equilibrium models, the change of stability occurs exactly at the maximum mass point, which was checked numerically with a very good accuracy. Moreover, different scenarios for unstable solutions - i.e., collapse or expansion of unstable initial configurations - have been investigated by assuming different perturbations around equilibrium
Rapidly spinning dark matter-admixed neutron stars
No full textMillisecond pulsars, representing the older neutron star population, are believed to have undergone a prolonged period of dark matter accumulation, resulting in a higher dark matter content. Their extreme rotation makes them unique laboratories for studying rapidly rotating neutron stars admixed with dark matter. In this work, we model uniformly rotating neutron stars with a dark matter component that rotates independently from the baryon matter, allowing for the investigation of both corotating and counterrotating scenarios. We examine the impact of dark matter rotation on the macroscopic properties of neutron stars, including the mass-radius relation, the mass-shedding Keplerian limit, and moments of inertia, for various dark matter particle masses and total fractions, considering both core and halo distributions. Our findings provide a more comprehensive understanding of how dark matter influences the equilibrium properties of rotating neutron stars, offering new insights into the astrophysical implications of self-interacting dark matter
The role of isoprene emission in two Arundineae species exposed to progressive drought stress
No full textIsoprene is the most abundant biogenic volatile organic compound emitted
from vegetation and has been suggested to have protective role in plants under
different kinds of stress. In this study we compared the responses to drought
stress of two Arundineae species which differ in their ability to emit isoprene –
Arundo donax, a promising biofuel crop and isoprene emitter, and Hakonechloa
macra, a non-emitting ornamental plant. Our results showed better recovery
of photosynthesis in A. donax after rehydration in comparison to H. macra.
H. macra had lower photosystem II (PSII) photochemical efficiency, increased
non-photochemical quenching (NPQ) and high levels of leaf malondialdehyde
(MDA) and proline content when exposed to drought stress. The isoprene emitting
species A. donax showed enhanced drought tolerance and better recovery
after rewatering than the non-emitting H. macra. Our results confirm the idea
that in isoprene emitting species, the function of isoprene is closely associated
with functioning of the photosynthetic apparatus
In vitro cytotoxicity evaluation of functional PEG-PDMA block copolymer in liver HEPG2 cells
No full textThe development of matrices to control the release of drugs into specific sites in the human body is a perspective biomedical application of polymeric materials. The aim of this work was to evaluate the cytotoxicity of a newly synthesized functional block copolymer of composition PEO-b-PDMA for application in nanosized drug delivery systems.
The toxicological effect of the copolymer was studied by in vitro exposure of human liver HepG2 cell line. Toxicity was examined by two methods - MTT test and Neutral red assay following the exposure to the copolymer in the concentration range from 1 - 1000 mu g/ml for 24 and 48 h. It was shown that no toxic outcome was observed in the concentration range from 1 - 1000 mu g/ml, even after 48h of incubation. The results from the study demonstrated a good safety profile for the investigated hydrophilic PEO-PDMA block copolymer
Radial perturbations of the scalarized Einstein-Gauss-Bonnet black holes
No full textRecently a new class of scalarized black holes in Einstein-Gauss-Bonnet (EGB) theories was discovered. What is special for these black hole solutions is that the scalarization is not due to the presence of matter, but it is induced by the curvature of spacetime itself. Moreover, more than one branch of scalarized solutions can bifurcate from the Schwarzschild branch, and these scalarized branches are characterized by the number of nodes of the scalar field. The next step is to consider the linear stability of these solutions, which is particularly important due to the fact that the Schwarzschild black holes lose stability at the first point of bifurcation. Therefore we here study in detail the radial perturbations of the scalarized EGB black holes. The results show that all branches with a nontrivial scalar field with one or more nodes are unstable. The stability of the solutions on the fundamental branch, whose scalar field has no radial nodes, depends on the particular choice of the coupling function between the scalar field and the Gauss-Bonnet invariant. We consider two particular cases based on the previous studies of the background solutions. If this coupling has the form used in [D. D. Doneva and S. S. Yazadjiev, Phys. Rev. Lett. 120, 131103 (2018)] the fundamental branch of solutions is stable, except for very small masses. In the case of a coupling function quadratic in the scalar field [H. O. Silva, J. Sakstein, L. Gualtieri, T. P. Sotiriou, and E. Berti, Phys. Rev. Lett. 120, 131104 (2018)], though, the whole fundamental branch is unstable.Deutsche ForschungsgemeinschaftEuropean CommissionSofia UniversityMinisterium für Wissenschaft, Forschung und Kunst (Baden-Württemberg)Baden-Wurttemberg StiftungDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu
Shadows of rotating hairy Kerr black holes coupled to time periodic scalar fields with a nonflat target space
No full textWe study the shadows cast by rotating hairy black holes with two nontrivial time-periodic scalar fields having a nonflat Gaussian curvature of the target space spanned by the scalar fields. Such black holes are a viable alternative to the Kerr black hole, having a much more complicated geodesic structure and resulting shadows. We investigate how a nontrivial Gauss curvature alters the pictures for different amounts of scalar hair around the black holes, quantified by a normalized charge. Our results show that for high values of this charge, close to a boson star limit, chaotic shadows are observed with multiple small disconnected components for all considered Gaussian curvatures. For moderately large amounts of scalar hair and corresponding normalized charge, although the shadows still exhibit chaotic behavior, a dominant shadow component emerges, the size and shape of which are substantially influenced by the Gaussian curvature. For instance, highly chaotic shadows for flat target space, start developing a large central shadow region with the increase of the Gauss curvature even for black holes with substantially heavy scalar hair. For lower values of the normalized charge, the shadows resemble qualitatively the Kerr black hole while the Gaussian curvature has a small impact on their properties.</p
Tradeoffs between isoprene emission, carbon gain and water use among different genera of Arundineae
No full textThere is a growing interest for the application of biofuels in different parts of the world. It is assumed that the cultivation land for biofuel crops will reach up to 752Mha in 2050. However, a large number of biofuel crops are emitting isoprene, which is highly reactive VOCs and affects the oxidative capacity of the atmosphere. In addition, the large-scale cultivation of biofuel crops will affect the water and nutrient resources of land. Therefore, the evaluation of biofuel crops with regard to their environmental effects and searching for new crops with less environmental impacts is highly beneficial. During this work, we screened 6 different species of Arundineae, a tribe from Poaceae, in terms of their photosynthesis, isoprene emission, water use efficiency (WUE), chlorophyll fluorescence, leaf anatomy and biomass development. Based on our results, A.donax showed the highest biomass increase and WUE and lowest fraction of assimilated carbon lost as isoprene, which highlights its capacity as a biofuel crop with low negative environmental effects compared with other genera of the Arundineae. The investigated species had different capacities for isoprene emission and there was a positive correlation between isoprene emission and photosynthesis within the tribe. Non-isoprene emitter species had much higher non-photochemical quenching (NPQ) compared with isoprene emitters, which confirms the photo-protective role of isoprene. There were simillarities in leaf anatomy of some species while the chloroplast shape was specificit for each specie
Isoprene emission in the monocot Arundineae tribe in relation to functional and structural organization of the photosynthetic apparatus
No full textSeveral plant species emit isoprene, a compound able to protect plants against high temperatures and oxidative stresses, and to affect the oxidative capacity of the atmosphere. The emission of isoprene in monocots is much less investigated than in dicots. We explored the emission of isoprene among members of the Poaceae tribe Arundineae, and its potential impact on plant performance. Our results confirm, also in monocots, the existence of a significant correlation between photosynthesis and isoprene emission and further suggest that isoprene inversely correlates to habitat xericity in unstressed Arundineae. Isoprene emission capacity developed rapidly in unfolding leaves, implying some developmental differences in the control of this biosynthetic pathway with respect to dicots. Among Arundineae, marked species-specific differences in several parameters related to plant productivity (photosynthesis, carbon lost as isoprene, water use efficiency, biomass and chloroplast ulrastructure) were observed. Isoprene presence improved structural organization of thylakoid membrane system and decreased the heat dissipation at physiological temperature. Our results demonstrate that, as in dicots, also in monocots isoprene could contribute to improve photosynthesis performance, although this was not necessarily reflected in higher yields, at least in unstressed condition
- …
