3,078 research outputs found
Socio-Economic Impact of the Creation and Operation of Mega-Science Projects
Challenges of development facing society and states require efforts consolidation, in the research field in particular. Therefore, to organize international cooperation and to conduct basic and applied research, mega-science infrastructures are being created and implemented all over the world. Currently, research facilities of the mega-science class are being created in the Russian Federation. They play an important role in the development of science and the innovation process. The competitiveness of Russian science is a determining factor for ensuring the safety and technological independence of Russia. Therefore, the Federal program for the development of Synchrotron and Neutron research and research infrastructure for 2019-2027 was approved in March 2020.
In the present article, the concept of the socio-economic impact of the operation of large-scale research infrastructure is revealed. The authors refer to the materials on the socio-economic impact analysis, which was based on the data on the Swedish neutron source (European Spallation Source). The article provides a generalized idea of the main indicators for assessing the potential of the research infrastructure as well as their application to characterize the research facilities in the Russian Federation. It is worth highlighting that each large research facility is unique and it is not possible to unify the analysis of the socio-economic impact. However, the obtained results can be used for a similar analysis of research infrastructures, based on the same physical principles and created to solve general scientific problems
Statistics of low-energy levels of a one-dimensional weakly localized Frenkel exciton: A numerical study
Numerical study of the one-dimensional Frenkel Hamiltonian with on-site
randomness is carried out. We focus on the statistics of the energy levels near
the lower exciton band edge, i. e. those determining optical response. We found
that the distribution of the energy spacing between the states that are well
localized at the same segment is characterized by non-zero mean, i.e. these
states undergo repulsion. This repulsion results in a local discrete energy
structure of a localized Frenkel exciton. On the contrary, the energy spacing
distribution for weakly overlapping local ground states (the states with no
nodes within their localization segments) that are localized at different
segments has zero mean and shows almost no repulsion. The typical width of the
latter distribution is of the same order as the typical spacing in the local
discrete energy structure, so that this local structure is hidden; it does not
reveal itself neither in the density of states nor in the linear absorption
spectra. However, this structure affects the two-exciton transitions involving
the states of the same segment and can be observed by the pump-probe
spectroscopy. We analyze also the disorder degree scaling of the first and
second momenta of the distributions.Comment: 10 pages, 6 figure
Isotope shifts of the 2-2 transition in B-like ions
Isotope shifts of the 2-2 transition in B-like ions are
evaluated for a wide range of the nuclear charge number: Z=8-92. The
calculations of the relativistic nuclear recoil and nuclear size effects are
performed using a large scale configuration-interaction Dirac-Fock-Sturm
method. The corresponding QED corrections are also taken into account. The
results of the calculations are compared with the theoretical values obtained
with other methods. The accuracy of the isotope shifts of the
2-2 transition in B-like ions is significantly improved.Comment: arXiv admin note: text overlap with arXiv:1410.707
Simulation of interaction of oriented J aggregates with resonance laser radiation
The interaction of laser radiation with single J aggregates of cyanine dyes
is theoretically analyzed and numerically simulated. The quantum mechanical
calculations of the equilibrium geometry and the energies and intensities of
the lowest singlet electronic transitions in pseudoisocyanine chloride and its
linear (chain) oligomers are fulfilled. The data of these calculations can
serve as parameters of the analyzed model of interaction of J aggregates with
radiation in the oneparticle density matrix approximation. This model takes
into account relaxation processes, the annihilation of excitations at
neighboring molecules, and inho mogeneous broadening. Assuming that the
inhomogeneous broadening is absent, calculations demonstrate the existence of
spatial bistability, molecular switching waves, and dissipative solitons. The
effect of the inhomogeneous broadening and the radiation intensity on the
effective coherence length in linear (chain) J aggregates is analyzedComment: 8 pages, 8 figure
Giant negative magnetoresistance in semiconductors doped by multiply charged deep impurities
A giant negative magnetoresistance has been observed in bulk germanium doped
with multiply charged deep impurities. Applying a magnetic field the resistance
may decrease exponentially at any orientation of the field. A drop of the
resistance as much as about 10000% has been measured at 6 T. The effect is
attributed to the spin splitting of impurity ground state with a very large
g-factor in the order of several tens depending on impurity.Comment: 4 pages, 4 figure
Cooperative Emission from an Ensemble of Three-Level Λ Radiators in a Cavity:An Insight from the Viewpoint of Dynamics of Nonlinear Systems
Cooperative radiation emitted by an ensemble of three-level optical systems with a doublet in the ground state (Λ scheme), which is placed into a cyclic cavity, is studied theoretically. In contrast to the twolevel model of emitters, this process with such a configuration of operating transitions may occur without population inversion in the whole, if the doublet is prepared at the initial instant in a superposition (coherent) state. In the ideal case of a Hamilton system, in which the cavity losses and relaxation in the radiator ensemble are disregarded, the conservation laws are derived, which allow a substantial reduction of the dimension of the phase space of the model (ℝ11 → ℝ5) and the application of methods of dynamics of nonlinear systems for analyzing the three-level superradiance under these conditions. The possibility of different (both quasiperiodic and chaotic) scenarios of the three-level superradiance is demonstrated on the basis of Poincaré’s mappings. Global bifurcation of the system upon a transition from the conventional superradiance regime to inversionless one is revealed. The effects of cavity losses, as well as homogeneous and inhomogeneous broadening in the system of radiators on the regularities found are also discussed
Effects of turbulent mixing on critical behaviour in the presence of compressibility: Renormalization group analysis of two models
Critical behaviour of two systems, subjected to the turbulent mixing, is
studied by means of the field theoretic renormalization group. The first
system, described by the equilibrium model A, corresponds to relaxational
dynamics of a non-conserved order parameter. The second one is the strongly
non-equilibrium reaction-diffusion system, known as Gribov process and
equivalent to the Reggeon field theory. The turbulent mixing is modelled by the
Kazantsev-Kraichnan "rapid-change" ensemble: time-decorrelated Gaussian
velocity field with the power-like spectrum k^{-d-\xi}. Effects of
compressibility of the fluid are studied. It is shown that, depending on the
relation between the exponent \xi and the spatial dimension d, the both systems
exhibit four different types of critical behaviour, associated with four
possible fixed points of the renormalization group equations. The most
interesting point corresponds to a new type of critical behaviour, in which the
nonlinearity and turbulent mixing are both relevant, and the critical exponents
depend on d, \xi and the degree of compressibility. For the both models,
compressibility enhances the role of the nonlinear terms in the dynamical
equations: the region in the d-\xi plane, where the new nontrivial regime is
stable, is getting much wider as the degree of compressibility increases. In
its turn, turbulent transfer becomes more efficient due to combined effects of
the mixing and the nonlinear terms.Comment: 25 pages, 4 figure
First Results of Magnetic Field Penetration Measurements of Multilayer SIS Structures
The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of Bp ≈200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the first results of our measurements of field penetration in Nb thin films and Nb-AlN-Nb multilayer samples at 4.2 K using the magnetic field penetration facility designed, built and tested in ASTeC
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