130,530 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
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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
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