58 research outputs found
Nonlocal vs local vortex dynamics in the transversal flux transformer effect
In this follow-up to our recent Letter [F. Otto et al., Phys. Rev. Lett. 104,
027005 (2010)], we present a more detailed account of the superconducting
transversal flux transformer effect (TFTE) in amorphous (a-)NbGe nanostructures
in the regime of strong nonequilibrium in local vortex motion. Emphasis is put
on the relation between the TFTE and local vortex dynamics, as the former turns
out to be a reliable tool for determining the microscopic mechanisms behind the
latter. By this method, a progression from electron heating at low temperatures
T to the Larkin-Ovchinnikov effect close to the transition temperature Tc is
traced over a range 0.26 < T/Tc < 0.95. This is represented by a number of
relevant parameters such as the vortex transport entropy related to the
Nernst-like effect at low T, and a nonequilibrium magnetization enhancement
close to Tc. At intermediate T, the Larkin-Ovchinnikov effect is at high
currents modified by electron heating, which is clearly observed only in the
TFTE
Delocalized nonlinear vibrational modes in graphene: second harmonic generation and negative pressure
With the help of molecular dynamics simulations, delocalized nonlinear vibrational modes (DNVM) in graphene are analyzed. Such modes are dictated by the lattice symmetry, they are exact solutions to the atomic equations of motion, regardless the employed interatomic potential and for any mode amplitude (though for large amplitudes they are typically unstable). In this study, only one‐ and two‐component DNVM are analyzed, they are reducible to the dynamical systems with one and two degrees of freedom, respectively. There exist 4 one‐component and 12 two‐component DNVM with in‐plane atomic displacements. Any two‐component mode includes one of the one‐component modes. If the amplitudes of the modes constituting a two‐component mode are properly chosen, periodic in time vibrations are observed for the two degrees of freedom at frequencies ω and 2ω, that is, second harmonic generation takes place. For particular DNVM, the higher harmonic can have frequency nearly two times larger than the maximal frequency of the phonon spectrum of graphene. Excitation of some of DNVM results in the appearance of negative in‐plane pressure in graphene. This counterintuitive result is explained by the rotational motion of carbon hexagons. Our results contribute to the understanding of nonlinear dynamics of the graphene lattice
Multiparametric optical bioimaging reveals the fate of epoxy crosslinked biomeshes in the mouse subcutaneous implantation model
Biomeshes based on decellularized bovine pericardium (DBP) are widely used in reconstructive surgery due to their wide availability and the attractive biomechanical properties. However, their efficacy in clinical applications is often affected by the uncontrolled immunogenicity and proteolytic degradation. To address this issue, we present here in vivo multiparametric imaging analysis of epoxy crosslinked DBPs to reveal their fate after implantation. We first analyzed the structure of the crosslinked DBP using scanning electron microscopy and evaluated proteolytic stability and cytotoxicity. Next, using combination of fluorescence and hypoxia imaging, X-ray computed microtomography and histology techniques we studied the fate of DBPs after subcutaneous implantation in animals. Our approach revealed high resistance to biodegradation, gradual remodeling of a surrounding tissue forming the connective tissue capsule and calcification of crosslinked DBPs. These changes were concomitant to the development of hypoxia in the samples within 3 weeks after implantation and subsequent induction of angiogenesis and vascularization. Collectively, presented approach provides new insights on the transplantation of the epoxy crosslinked biomeshes, the risks associated with its applications in soft-tissue reconstruction and can be transferred to studies of other types of implants
Imaging the nanoscale organization of peptidoglycan in living Lactococcus lactis cells
Peptidoglycans provide bacterial cell walls with
mechanical strength. The spatial organization of peptidoglycan has previously been difficult
to study. Here, atomic force microscopy, together with cells carrying mutations in cell-wall
polysaccharides, has allowed an in-depth study of these molecules
Observation of gravitational waves from the coalescence of a 2.5−4.5 M⊙ compact object and a neutron star
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