Indoline spiropyran containing an σ-acceptor chlorine atom in 6′ position of the 2
H
-chromene part of the molecule was synthesized and studied. The use of 1,2,3,3-tetramethyl-3
H
-indolium ...perchlorate as a starting compound made it possible to achieve higher product yields as compared to previous studies. The molecular structure of the compound was established by single crystal X-ray diffraction analysis. The features of the crystal structure and intermolecular interactions were investigated using CrystalExplorer17 software package. The photochromic behavior in acetonitrile solution was studied for the first time. It was found that the merocyanine form of spiropyran is characterized by an absorption maximum at 592 nm, which is 37 nm closer to the range of the “biological window” in comparison with the nitro-substituted analog.
•Dynamics of generator of quasiperiodic oscillations forced by periodic sequence pulses is considered.•Small- and large-scale structures for non-autonomous generator were observed.•Three-frequency ...quasiperiodic oscillations are demonstrated.•Arnold resonance web was shown.
A model of a generator of quasiperiodic oscillations forced by a periodic pulse sequence is studied. We analyze synchronization when the autonomous generator demonstrates periodic, quasiperiodic, respective weakly chaotic oscillations. For the forced quasiperiodic oscillations a picture of synchronization, consisting of small-scale and large-scale structures was uncovered. It even includes the existence of stable the three-frequency tori. For the regime of weak chaos a partial destruction of this features and of the regime of three-frequency tori are found.
Display omitted
•PLLA fibers were non-covalently coated with gelatin via toluene/ethanol treatment.•Gelatin immobilization enhanced PLLA hydrophilicity, strength and biocompatibility.•Thickness of ...gelatin-containing coating was found at ≈400 nm.•Optimal time of gelatin immobilization was found at 5 min.•Suggested method doesn't require special equipment or high-cost reagents.
In the present study, we report a simple and efficient method of gelatin immobilization on the surface of PLA electrospun fibers using pre-treatment with a mixture of toluene and ethanol allowing to form swelled surface layer followed by gelatin adsorption from its solution in PBS. Our results demonstrate that gelatin immobilization leads to a decrease in the water contact angle from 120° to 0°, enhances scaffold strength up to 50%, and doubles the number of adhered cells and their average area. We observed that the maximum amount of gelatin (0.07 ± 0.01 mg per cm3 of the scaffold) was immobilized during the first five minutes of exposure to the gelatin solution. Modified scaffolds demonstrated increased strength.
Synchronization in the system of coupled non-identical non-isochronous van der Pol–Duffing oscillators with inertial and dissipative coupling is discussed. Generalized Adler’s equation is obtained ...and investigated in the presence of all relevant factors affecting the synchronization (non-isochronism of the oscillators, their non-identity, coupling of the dissipative and inertial types). Characteristic symmetries are revealed for the Adler’s equation responsible for equivalence of some of the factors. Numerical study of the parameters space of the initial differential equations is carried out using the method of charts of dynamic regimes in the parameter planes. Results obtained by both these approaches are compared and discussed.
We study numerically the dynamics of low–dimensional ensembles of discrete neuron models - Chialvo maps. We are focused on choosing the autonomous map parameters corresponding to the invariant curve. ...We consider two cases of coupling organization: (i) via a nonlinear function of models; (ii) linear coupling, which is an analog of electrical neuron interaction. For the first case, the possibility of invariant curve doublings and the emergence of quasi-periodicity within Arnold tongues as a result of the secondary Neimark-Sacker bifurcation are found. For the second case, we discover an area of three-frequency quasi-periodicity for the case of two neurons. It arises softly as a result of quasi-periodic Hopf bifurcation. We demonstrate a set of resonant two-frequency regimes tongues embedded in this area and bounded by lines of saddle-node bifurcations of invariant curves. For ensemble of three linearly coupled maps, four-frequency quasi-periodicity becomes possible with a built-in system of tongues of three-frequency regimes (tori). We discuss the effect of noise and the evolution of “noise quasi-periodic” regimes, resonant regimes of this type and bifurcations of invariant tori with increasing of noise intensity.
Composite poly-L-lactide acid-based scaffolds with hydroxyapatite (HAp) content up to 75 wt.% were fabricated via solution blow spinning. The influence of HAp concentration on structure, wettability, ...mechanical properties and chemical and phase composition of the produced materials was examined. It was found that with an increase of HAp content the average fiber diameter was increased, the uniaxial strength and relative elongation were reduced, while the phase composition and surface wettability did not change. The performance of the scaffolds during implantation in the parietal bone of a rat skull for a period from 15 to 90 days was studied. The materials have shown high ability to integrate with both soft and hard tissues. It was found that scaffolds with 25 wt.% HAp content significantly enhance osteogenesis during scarification (damage) of the periosteum. Overall, the fabricated scaffolds proved to be highly efficient for replacing bone defects in long tubular bones.
Solid-state photochromic indoline spiropyrans bearing a formyl group at the 6′ and 8′ positions of the 2
H
-chromene moiety of the molecules were characterized. The molecular structures of ...spiropyrans were established by single-crystal X-ray diffraction. Intermolecular interactions and voids in the crystals were investigated using the CrystalExplorer17 software package. Further studies of photochromism and mechanochromism of these spiropyrans in the crystalline state are shown to be promising.
We study complex dynamics of the Chialvo model that is the simplest neuron-type model in form of a four-parameter family of two-dimensional noninvertible maps (endomorphisms). Main elements of ...bifurcation diagram in the plane of two parameters have been constructed in which regions corresponding to both quasi-periodic and chaotic oscillations are selected. We also indicate special regions corresponding to singular discrete chaotic Shilnikov attractors that we consider as a new type of the so-called snap-back repellers (over an unstable focus). The study of time series was carried out in which there were classified patterns of specific oscillatory activities in the cases when homoclinic orbits to the unstable focus exists and, when such orbits were not yet formed but a strange attractor already exists. New dynamical characteristics are proposed, with the help of which it is possible to assess the level of distinctness of atypical oscillatory activity.
•the simplest neuron model in form map is studied including detailed parametric bifurcation analysis;•special regions in parameter space corresponding to singular discrete chaotic Shilnikov attractors are localized;•a new type of the so-called snap-back repellers is shown;•a specific oscillatory activity associated with Shilnikov attractor is observed;•new dynamical characteristics are proposed for detection atypical oscillatory activity.
A problem of synchronization of quasiperiodic oscillations is discussed in application to an example of coupled systems with autonomous quasiperiodic dynamics. Charts of Lyapunov exponents are ...presented that reveal characteristic domains on the parameter plane such as oscillator death, complete synchronization, phase synchronization of quasiperiodic oscillations, broadband synchronization, broadband quasiperiodicity. Features of each kind of dynamical behavior are discussed. Analysis of corresponding bifurcations is presented, including quasiperiodic Hopf bifurcations, saddle–node bifurcations of invariant tori of different dimensions, and bifurcations of torus doublings. Both the case of dominance of quasiperiodic oscillations in one of the generators and the case of pronounced periodic resonances embedded in the region of quasiperiodicity are considered.
•Dynamics of coupled generators of quasiperiodic oscillations is investigated.•Different types of synchronization are observed: complete, phase and broadband synchronization.•The complex picture of the multi-frequency quasiperiodic oscillations including the Arnold resonance web is revealed.
•Dynamics of a non-autonomous oscillator with adaptive properties, when the phase and frequency of the external force depend on the dynamical variable is studied.•Occurrence of chaotic dynamics in ...both models is observed.•Investigation of various parameter plane of external forcing was carried out.•Features of chaotic signal generating by the non-autonomous oscillator with analysis of Fourier spectra and phase portraits is studied.•Comparative analysis numerical results and physical experiment is presented.
The dynamics of a non-autonomous oscillator in which the phase and frequency of the external force depend on the dynamical variable is studied. Such a control of the phase and frequency of the external force leads to the appearance of complex chaotic dynamics in the behavior of oscillator. A hierarchy of various periodic and chaotic oscillations is observed. The structure of the space of control parameters is studied. It is shown there are oscillatory modes similar to those of a non-autonomous oscillator with a potential in the form of a periodic function in the system dynamics, but there are also significant differences. Physical experiments of such systems are implemented.
PDF
