6,549 research outputs found
Spin disorder scattering in a ferromagnetic insulator-on-graphene structure
We theoretically study the transport properties of a single graphene layer between two insulating materials, i.e., a ferromagnetic EuO thin film and a nonmagnetic SiC substrate. An exchange interaction between the charge carrier spins in graphene and the localized magnetic moments in the ferromagnetic insulator is assumed. This proximity effect and the large spin fluctuations at temperatures close to the ferromagnetic transition temperature TC lead to spin disorder scattering, which is calculated using a Green's function technique. Numerical results indicate that at temperatures close to TC the contribution of the spin disorder scattering to the total electron mobility is clearly observable even in the case of a weak exchange interaction and a low background mobility of the graphene layer. This enables the experimental determination of the exchange interaction parameter using the present model and a simple resistivity measurement.Peer reviewe
Recommended Thermal Rate Coefficients for the C + H Reaction and Some Astrochemical Implications
We have incorporated our experimentally derived thermal rate coefficients for
C + H forming CH and CH into a commonly used astrochemical
model. We find that the Arrhenius-Kooij equation typically used in chemical
models does not accurately fit our data and use instead a more versatile
fitting formula. At a temperature of 10 K and a density of 10 cm, we
find no significant differences in the predicted chemical abundances, but at
higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes.
Additionally, we find that the relatively small error on our thermal rate
coefficients, , significantly reduces the uncertainties on the
predicted abundances compared to those obtained using the currently implemented
Langevin rate coefficient with its estimated factor of 2 uncertainty.Comment: 19 pages, 5 figures. Accepted for publication in Ap
Merged-beams Reaction Studies of O + H_3^+
We have measured the reaction of O + H3+ forming OH+ and H2O+. This is one of
the key gas-phase astrochemical processes initiating the formation of water
molecules in dense molecular clouds. For this work, we have used a novel merged
fast-beams apparatus which overlaps a beam of H3+ onto a beam of ground-term
neutral O. Here, we present cross section data for forming OH+ and H2O+ at
relative energies from \approx 3.5 meV to \approx 15.5 and 0.13 eV,
respectively. Measurements were performed for statistically populated O(3PJ) in
the ground term reacting with hot H3+ (with an internal temperature of \approx
2500-3000 K). From these data, we have derived rate coefficients for
translational temperatures from \approx 25 K to \approx 10^5 and 10^3 K,
respectively. Using state-of-the-art theoretical methods as a guide, we have
converted these results to a thermal rate coefficient for forming either OH+ or
H2O+, thereby accounting for the temperature dependence of the O fine-structure
levels. Our results are in good agreement with two independent flowing
afterglow measurements at a temperature of \approx 300 K, and with a
corresponding level of H3+ internal excitation. This good agreement strongly
suggests that the internal excitation of the H3+ does not play a significant
role in this reaction. The Langevin rate coefficient is in reasonable agreement
with the experimental results at 10 K but a factor of \approx 2 larger at 300
K. The two published classical trajectory studies using quantum mechanical
potential energy surfaces lie a factor of \approx 1.5 above our experimental
results over this 10-300 K range.Comment: 43 pages, 11 figures. Submitted to the Astrophysical Journa
Manipulation and Generation of Supercurrent in Out-of-Equilibrium Josephson Tunnel Nanojunctions
We demonstrate experimentally manipulation of supercurrent in Al-AlO_x-Ti
Josephson tunnel junctions by injecting quasiparticles in a Ti island from two
additional tunnel-coupled Al superconducting reservoirs. Both supercurrent
enhancement and quenching with respect to equilibrium are achieved. We
demonstrate cooling of the Ti line by quasiparticle injection from the normal
state deep into the superconducting phase. A model based on heat transport and
non-monotonic current-voltage characteristic of a Josephson junction
satisfactorily accounts for our findings.Comment: 4 pages, 4 colour figures, published versio
Simple model of the static exchange-correlation kernel of a uniform electron gas with long-range electron-electron interaction
A simple approximate expression in real and reciprocal spaces is given for
the static exchange-correlation kernel of a uniform electron gas interacting
with the long-range part only of the Coulomb interaction. This expression
interpolates between the exact asymptotic behaviors of this kernel at small and
large wave vectors which in turn requires, among other thing, information from
the momentum distribution of the uniform electron gas with the same interaction
that have been calculated in the G0W0 approximation. This exchange-correlation
kernel as well as its complement analogue associated to the short-range part of
the Coulomb interaction are more local than the Coulombic exchange-correlation
kernel and constitute potential ingredients in approximations for recent
adiabatic connection fluctuation-dissipation and/or density functional theory
approaches of the electronic correlation problem based on a separate treatment
of long-range and short-range interaction effects.Comment: 14 pages, 14 figures, to be published in Phys. Rev.
Astrophysical Relevance of Storage-Ring Electron-Ion Recombination Experiments
The relevance of storage-ring electron-ion recombination experiments for
astrophysics is outlined. In particular, the role of low-energy
dielectronic-recombination resonances is discussed. A bibliographic compilation
of electron-ion recombination measurements with cosmically abundant ions is
provided.Comment: 8 pages, 3 figures, 1 table, 77 references, Proceedings of the 14th
International Conference on the Physics of Highly Charged Ions, Cofu, Tokyo,
Septmber 1-5, 2008, to be published in J. Phys. Conf. Se
Применение компьютерной лингвистики для анализа основных направлений исследований в журнале «Экономика региона»
Over the past decades, the process of knowledge generation has accelerated, producing a lot of scientific publications, which makes reviewing even a relatively narrow subject area very demanding, if not impossible. However, recent text data mining tools can assist researchers in conducting such analysis in an objective and time-efficient way. We conduct such a literature review on 1307 articles published in the journal Economy of Regions from 2010 to 2021 using advanced topic modelling techniques. This analysis aims to describe the main research areas in the journal over time, the dynamics of their popularity and the relationship with key quantitative indicators. We identified 22 topics ranging from“Agriculture” and“Economic Geography” to“Fiscal Policy” and“Entrepreneurship”. We estimate how popularity of these topics was changing over time and find topics that gained the most popularity from 2010 to 2021 (+17.61 %,“Spatial Economics”) or lost it (-14.58 %,“Economics of Innovation”). The topic of environmental economics collects the largest number of citations per article (3.64, on average), and the topics on monetary policy and poverty are the most popular among manuscripts in English, which is also true for articles written by authors with foreign affiliation. Papers with third-party funding are concentrated the most in “Spatial Economics” (around 11 %), and the least — in “Agriculture”. Our results can help to understand the evolution in scope of research of Economy of Regions and serve researchers to find promising directions for future studies. © Savin, I. V., Teplyakov, N. S. Text. 2022.Russian Foundation for Basic Research, РФФИ; Russian Science Foundation, RSF: 19–18–00262; Kementerian Riset, Teknologi dan Pendidikan TinggiIt is also worth stressing that the covariates we use do not have high Pearson correlation coefficients, but those coefficients that we present below are significant at the 1 % level. The highest correlation is between year of publication and presence of third-party funding (0.5), which reveals the fact that studies published in ER in recent years have been supported by either Russian (Russian Science Foundation, Russian Foundation for Basic Research) or sometimes also foreign grants (e.g., Ministry of Education and Science of the Republic of Kazakhstan or National Science Centre Poland). Affiliation of one of the co-authors to a foreign university, contrary to our initial expectation, is not so strongly correlated with English language of the article (coefficient is 0.44, which is a moderate value). This can be explained by a considerable share of native Russian-speaking authors who went abroad but continue collaboration with their colleagues in Russia and publish in Russian. Finally, the share of articles with an author affiliated abroad has a slight tendency to increase in ER over time (Pearson correlation with year of publication is 0.12).The article has been prepared with the support from the Russian Science Foundation, conducted as part of the research project № 19–18–00262 “Modelling a balanced technological and socio-economic development of the Russian regions”.We proceed with exploring how papers are distributed by topic depending on whether they are supported by third-party funding or not. In other words, the topics most and least likely to have received third-party funding will be identified. The bottom panel in Figure 7 shows the result. The most supported topic by a wide margin is T13 on spatial economics, accounting for about 11 % of funded manuscripts. For example, the work of Karim et al.1 (belonging to 86.5 % to T13) on studying the spatial effect of transport infrastructure expansion on regional growth was funded by the Ministry of Research, Technology and Higher Education of Republic of Indonesia. The least funded topic is Agriculture (T4), although there is little difference from other less supported topics
Dielectronic Recombination of Fe XV forming Fe XIV: Laboratory Measurements and Theoretical Calculations
We have measured resonance strengths and energies for dielectronic
recombination (DR) of Mg-like Fe XV forming Al-like Fe XIV via N=3 -> N' = 3
core excitations in the electron-ion collision energy range 0-45 eV. All
measurements were carried out using the heavy-ion Test Storage Ring at the Max
Planck Institute for Nuclear Physics in Heidelberg, Germany. We have also
carried out new multiconfiguration Breit-Pauli (MCBP) calculations using the
AUTOSTRUCTURE code. For electron-ion collision energies < 25 eV we find poor
agreement between our experimental and theoretical resonance energies and
strengths. From 25 to 42 eV we find good agreement between the two for
resonance energies. But in this energy range the theoretical resonance
strengths are ~ 31% larger than the experimental results. This is larger than
our estimated total experimental uncertainty in this energy range of +/- 26%
(at a 90% confidence level). Above 42 eV the difference in the shape between
the calculated and measured 3s3p(^1P_1)nl DR series limit we attribute partly
to the nl dependence of the detection probabilities of high Rydberg states in
the experiment. We have used our measurements, supplemented by our
AUTOSTRUCTURE calculations, to produce a Maxwellian-averaged 3 -> 3 DR rate
coefficient for Fe XV forming Fe XIV. The resulting rate coefficient is
estimated to be accurate to better than +/- 29% (at a 90% confidence level) for
k_BT_e > 1 eV. At temperatures of k_BT_e ~ 2.5-15 eV, where Fe XV is predicted
to form in photoionized plasmas, significant discrepancies are found between
our experimentally-derived rate coefficient and previously published
theoretical results. Our new MCBP plasma rate coefficient is 19-28% smaller
than our experimental results over this temperature range
Learning at the Interstices; Locating Practical Philosophies for Understanding Physical/virtual Inter-spaces
Virtual worlds are relatively recent developments, and so it is tempting to believe that they need to be understood through newly developed theories and philosophies. However, humans have long thought about the nature of reality and what it means to be “real.” This paper examines the three persistent philosophical concepts of Metaxis, Liminality and Space that have evolved across more than 2000 years of meditation, contemplation and reflection. Our particular focus here is on the nature of the interface between the virtual and the physical: at the interstices, and how the nature of transactions and transitions across those interfaces may impact upon learning. This may, at first, appear to be an esoteric pursuit, but we ground our arguments in primary and secondary data from research studies in higher education
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