Dynamics of Vortex Shells in Mesoscopic Superconducting Corbino Disks

In mesoscopic superconducting disks vortices form shell structures as recently observed in Nb disks. We study the dynamics of such vortices, driven by an external current I_0, in a Corbino setup. At very low I_0, the system exhibits rigid body rotation while at some critical current I_c,i vortex shells rotate separately with angular velocities omega_i. This critical current I_c,i has a remarkable non-monotonous dependence on the applied magnetic field which is due to a dynamically-induced structural transition with a rearrangement of vortices over the shells similar to the Coster-Kronig transition in hollow atoms. Thermally-activated externally-driven flux motion in a disk with pinning centers explains experimentally observed omega_i as a function of I_0 and T and the dynamically-induced melting transition.Comment: 5 pages, 5 figure

Nucleation of superconductivity in mesoscopic star-shaped superconductors

We study the phase transition of a star-shaped superconductor, which covers smoothly the range from zero to two dimensions with respect to the superconducting coherence length. Detailed measurements and numerical calculations show that the nucleation of superconductivity in this device is very inhomogeneous, resulting in rich structure in the superconducting transition as a function of temperature and magnetic field. The superconducting order parameter is strongly enhanced and mostly robust in regions close to multiple boundaries.Comment: 4 pages, 5 figures, E-mail addresses: [email protected] (V. Chandrasekhar), [email protected] (J. T. Devreese

Geometry-induced localization of thermal fluctuations in ultrathin superconducting structures

Thermal fluctuations of the order parameter in an ultrathin triangular shaped superconducting structure are studied near $T_{c}$, in zero applied field. We find that the order parameter is prone to much larger fluctuations in the corners of the structure as compared to its interior. This geometry-induced localization of thermal fluctuations is attributed to the fact that condensate confinement in the corners is characterised by a lower effective dimensionality, which favors stronger fluctuations.Comment: 9 pages, 5 figure

Training the Next Generation of Translational Scientists: The Case Western Reserve University Translational Fellows Program

Background: An important part of biomedical research is the translation of discoveries into clinical or community applications that impact patient health. For a vast majority of clinical applications and sustainable community interventions, a time-tested way to get innovations to patients is through licensing of the technology and commercial development, often through startups. While biomedical scientists and trainees are schooled in discovery research, the processes of commercialization are foreign or intimidating. Further, many trainees will not aspire to a faculty position, and other avenues of advancement are desirable. Methods: At Case Western Reserve University, we developed and launched a Translational Fellows Program to provide such training for the community, focusing specifically on graduate students and postdoctoral fellows. The goals of this program include familiarizing our trainees with the principles of entrepreneurship, product development, and startups. This is accomplished through study of their laboratory\u27s technology to identify points of translational focus and to increase awareness to potentially move ideas and products toward societal impact. This program leverages much of our existing infrastructure and provides a mechanism for the prioritization of the translation of the technology as well as release-time to promote effort. Results: Launched in summer 2020, our first cohort had 3 of the 12 fellows launching startups based on their technology and submitting an National Institutes of Health Small Business Innovation Research (SBIR) proposal. At least 80% reported increased knowledge and confidence in five of six key translational competencies. Conclusion: We are now continuing and improving the program and searching for sustainable support to stabilize the program for a long-term productive future

Transition from single-file to two-dimensional diffusion of interacting particles in a quasi-one-dimensional channel

Diffusive properties of a monodisperse system of interacting particles confined to a \textit{quasi}-one-dimensional (Q1D) channel are studied using molecular dynamics (MD) simulations. We calculate numerically the mean-squared displacement (MSD) and investigate the influence of the width of the channel (or the strength of the confinement potential) on diffusion in finite-size channels of different shapes (i.e., straight and circular). The transition from single-file diffusion (SFD) to the two-dimensional diffusion regime is investigated. This transition (regarding the calculation of the scaling exponent ($\alpha$) of the MSD $$ $\propto t^{\alpha}$) as a function of the width of the channel, is shown to change depending on the channel's confinement profile. In particular the transition can be either smooth (i.e., for a parabolic confinement potential) or rather sharp/stepwise (i.e., for a hard-wall potential), as distinct from infinite channels where this transition is abrupt. This result can be explained by qualitatively different distributions of the particle density for the different confinement potentials.Comment: 13 pages, 11 figure

Formation and Size-Dependence of Vortex Shells in Mesoscopic Superconducting Niobium Disks

Recent experiments [I.V. Grigorieva et al., Phys. Rev. Lett. 96, 077005 (2006)] on visualization of vortices using the Bitter decoration technique revealed vortex shells in mesoscopic superconducting Nb disks containing up to L=40 vortices. Some of the found configurations did not agree with those predicted theoretically. We show here that this discrepancy can be traced back to the larger disks with radii R ~ 1 to 2.5\mu m, i.e., R ~ 50-100\xi(0) used in the experiment, while in previous theoretical studies vortex states with vorticity L < 40 were analyzed for smaller disks with R ~ 5-20\xi(0). The present analysis is done for thin disks (mesoscopic regime) and for thick (macroscopic) disks where the London screening is taken into account. We found that the radius of the superconducting disk has a pronounced influence on the vortex configuration in contrast to, e.g., the case of parabolic confined charged particles. The missing vortex configurations and the region of their stability are found, which are in agreement with those observed in the experiment.Comment: 12 pages, 1 table, 12 figure

Nonuniform Self-Organized Dynamical States in Superconductors with Periodic Pinning

We consider magnetic flux moving in superconductors with periodic pinning arrays. We show that sample heating by moving vortices produces negative differential resistivity (NDR) of both N and S type (i.e., N- and S-shaped) in the voltage-current characteristic (VI curve). The uniform flux flow state is unstable in the NDR region of the VI curve. Domain structures appear during the NDR part of the VI curve of an N type, while a filamentary instability is observed for the NDR of an S type. The simultaneous existence of the NDR of both types gives rise to the appearance of striking self-organized (both stationary and non-stationary) two-dimensional dynamical structures.Comment: 4 pages, 2 figure

Russian-Egyptian Cooperation in the Context of the Prospects for the Great Eurasian Partnership

The article examines the development of economic cooperation and trade exchange between Russia and Egypt over the past ten years. The most important joint projects of Russia and Egypt at the level of the public and private sectors, as well as the most important obstacles to expanding the scope of economic cooperation and trade exchange at the private sector level between the Egyptian and Russian parties are analyzed.Aim. This study aims to monitor the various forms of economic cooperation between Egypt and Russia, since the history of these relations goes back more tha n two centuries, and currently Russia is considered one of the strongest economies in the world, one of the ten strongest economies in the world, according to the latest report from the International Monetary Fund, and is also the strongest economy in the Eurasian Union.Tasks. Analysis of the most important economic projects in various sectors such as the agriculture and food sector, transport, free zones, energy and military cooperation, tourism between Egypt and the Russian Federation in the period from 2014 to the present, determining the degree of effectiveness of these joint projects and factors contributing to increase in the efficiency of the efficiency of the implementation of these projects and increase economic feasibility. Explore cross-culture barriers that hinder the establishment of closer contacts between the private businesses of both sides.Methods. In this work, using the methods of logical and statistical analysis, factors were identified that contribute to the effectiveness of economic and investment interaction used in the implementation of projects aimed at bilateral development at the state level. The problems arising at the level of interaction between the private sectors of the economy of both countries were also noted.Results. The study showed that economic projects between Egypt and the Russian Federation at the governmental level (governments, agencies, companies and public institutions) can still be considered essential for the Egyptian economy in order to achieve sustainable development, to which it aspires, but, on the contrary, for the private sector it is s till unsatisfactory and very small due to a group of intercultural obstacles, which, in our opinion, are not difficult to overcome.Conclusions. It is advisable to consider aspects of cooperation between Egypt and Russia on a wider and more comprehensive scale than at present, and to use the opportunities available at the level of the public sector on a wider scale. With regard to trade cooperation at the private sector level, it is necessary to develop a plan to increase the volume of trade between the two countries, and it would be useful to enlist the support of the government authorities of the EEA countries