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Seizure activity leads to increases in extracellular potassium concentration ([K${}^{+}$]o), which can result in changes in neuronal passive and active membrane properties as well as in population activities. In this study, we examined how extracellular potassium modulates seizure activities using an acute 4-AP induced seizure model in the neocortex, both in vivo and in vitro. Moderately elevated [K${}^{+}$]o up to 9mM prolonged seizure durations and shortened interictal intervals as well as depolarized the neuronal resting membrane potential (RMP). However, when [K${}^{+}$]o reached higher than 9mM, seizure like events (SLEs) were blocked and neurons went into a depolarization-blocked state. Spreading depression was never observed as the blockade of ictal events could be reversed within 1–2min after the raised [K${}^{+}$]o was changed back to control levels. This concentration-dependent dual effect of [K${}^{+}$]o was observed using in vivo and in vitro mouse brain preparations as well as in human neocortical tissue resected during epilepsy surgery. Blocking the Ih current, mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, modulated the elevated [K${}^{+}$]o influence on SLEs by promoting the high [K${}^{+}$]o inhibitory actions. These results demonstrate biphasic actions of raised [K${}^{+}$]o on neuronal excitability and seizure activity.

To enable an accurate recognition of neuronal excitability in an epileptic brain for modeling or localization of epileptic zone, here the brain response to single-pulse electrical stimulation (SPES) has been decomposed into its constituent components using adaptive singular spectrum analysis (SSA). Given the response at neuronal level, these components are expected to be the inhibitory and excitatory components. The prime objective is to thoroughly investigate the nature of delayed responses (elicited between 100ms–1 s after SPES) for localization of the epileptic zone. SSA is a powerful subspace signal analysis method for separation of single channel signals into their constituent uncorrelated components. The consistency in the results for both early and delayed brain responses verifies the usability of the approach.

Time-dependent approach has been applied to positron–hydrogen scattering. The initial wavefunction of the system in this approach is expanded in terms of three-dimensional dynamical wavefunctions to include all higher angular momenta by solving a set of three coupled differential equations. The entire contributing scattering channels are automatically included in this approach. Therefore, it resolves the problems at the intermediate energies where the positronium-formation is important. The visualization of the two-particle correlated (angular dependent) wavefunction of the system as it evolves has been presented and provides quantitative analysis of the positronium-formation and ionization processes as they occur. The positron impact transfer (combined positronium-formation and ionization) probabilities obtained from the final wavefunction compares very well with those of time-dependent converged close-coupling calculations.

Excitable cellular automata with dynamical excitation interval exhibit a wide range of space-time dynamics based on an interplay between propagating excitation patterns which modify excitability of the automaton cells. Such interactions leads to formation of standing domains of excitation, stationary waves and localized excitations. We analyzed morphological and generative diversities of the functions studied and characterized the functions with highest values of the diversities. Amongst other intriguing discoveries we found that upper boundary of excitation interval more significantly affects morphological diversity of configurations generated than lower boundary of the interval does and there is no match between functions which produce configurations of excitation with highest morphological diversity and configurations of interval boundaries with highest morphological diversity. Potential directions of future studies of excitable media with dynamically changing excitability may focus on relations of the automaton model with living excitable media, e.g. neural tissue and muscles, novel materials with memristive properties and networks of conductive polymers.

Phyllosilicate is a sheet of silicate tetrahedra bound by basal oxygens. A phyllosilicate excitable automaton is a regular network of finite state machines, which mimics structure of a silicate sheet. A node of the silicate sheet is an automaton, which takes resting, excited and refractory states, and updates its state in discrete time depending on a sum of excited states of its three (silicon automata) or six (oxygen automata) closest neighbors. Oscillator is a localized compact configuration of nonquiescent states which undergoes finite growth and modification but returns to its original state in a finite number of steps. We show that phyllosilicate excitable automata exhibit waves and oscillating localizations (oscillators) dynamics. Basic types of oscillators are classified and characterized.

Motion of an electron is much different from that of a kind of matter in classical mechanics. Although it is impossible to directly observe the configuration of a bare electron, it is never as simple as to treat it as a three-dimensional (3D) particle in the microscopic world because the electron itself certainly has its own topological configuration, so that it presents a field of a unit charge and a spin, etc. An electron produces a magnetic field in motion and also can radiate or absorb an electromagnetic field in its accelerating motions. Thus, the topological configuration of an electron must be related or similar to the configurations of the magnetic field and electromagnetic wave. Starting from the topological configuration of a single electromagnetic wave, it is possible to derive that an electron is a quantized left-hand Möbius strip, on the center of which there exists an anti-neutrino. The Möbius strip excites a $2\pi$ circumference of a unit negative charge and a linear electric field of a $\pi$ torsion and can explain the wave feature of the electron and the essential cause of producing a magnetic field and radiating an electromagnetic wave as well as predict that the second-order tensor field among the three quarks in a proton has a topological configuration of right-hand three-leaf knot and can excite a $2\pi$ circumference of a unit positive charge and a linear electric field of a $\pi$ torsion, which is just allelomorphic to an electron.

The influence of erbium on physical and optical properties of calcium sulfate ultra-phosphate glass was investigated using conventional melt quench process. Selected samples of composition 20CaSO₄ (80 – x) P₂O₅– xEr₂O₃ with 0.1 $\le$x$\le$ 0.9 mol.% were prepared and assessed. X-ray diffraction (XRD) techniques were used to confirm the amorphous nature of the said samples. The structural units of phosphate-based glass were assessed from Raman spectra as ultra-(Q³), meta-(Q²), pyro-(Q¹) and orthophosphate (Q⁰) units. Depolymerization process of the glasses was testified for higher calcium oxide content and UV-visible for optical measurement. Thermal analysis have been investigated by means of thermogravimetric analysis. The results show the decomposition of materials in the temperature range of 25${}^{\circ }$C–1000${}^{\circ }$C. Er${}^{3+}$ absorption spectra were measured in the range of 400–1800nm. PL measurement was carried out in order to obtain the excitation and emission spectra of the samples. The emission spectra excited at 779nm comprises of 518nm, 550nm and 649nm of transition ⁴F${}_{9/2}$, ⁴S${}_{3/2}$ and ²H${}_{11/2}$ excited states to ⁴I${}_{15/2}$ ground state. In physical properties, the density calculated using Archimedes method is inversely proportional to molar volume with increase in Er${}^{3+}$ ions. Optical bandgap (E${}_g$) were determined using Tauc’s plots for direct transitions where E${}_g$ (direct) decreases with increase in erbium content. The refractive index increases with decreasing molar volume; this may have a tendency for larger optical bandgap. The result obtained from the glass matrix indicates that erbium oxide-doped calcium sulfate ultra-phosphate may give important information for wider development of functional glasses.

In the development of most phenomenological models used to explain the infrared excited luminescence, a major assumption is usually made in the degree of freedom the excited charge has. One of the two extremes is normally assumed: charge is free to move anywhere over the whole crystal, or it is confined close to the trap and the centers immediately adjacent to it. Determining which of these extremes is more reasonable is difficult to do on the basis of the temporal behavior of the luminescence intensity alone. However, this assumption has important consequences for the understanding of the dynamics of the luminescence process because of the difference in the number of recombination and trapping centers available to the excited charge. Additional experimental evidence was thus sought on this aspect of charge movement. One such experiment is the detection of photoconductivity in which an electrical current is measured during optical excitation or shortly there-after. In this paper, the details of photoconductivity experiments on K crystal are presented.

Photoconductivity measurements were inconclusive as to whether or not there was a current flowing during the 850 nm excitation of a feldspar sample. However, there was a clear current when exciting the same sample with 515 nm light, but there was a complex relationship between the magnitude of the current and the number of emission photons counted. A model was developed to explain the photoconductivity results where electrons migrate through the conduction band aided by thermal excitation and tunneling.

This paper investigates the effects of external excitation on the mixing performance of the micromixer with curved bluff-body structure. The micromixer was fabricated by the MEMS process of polydimethylsiloxane (PDMS). The mixing process and mixing efficiency were evaluated with a high speed camera. Results showed that the finger-spiked type flow patterns were generated in the mixing chamber under an excitation frequency of 5Hz. It turns out that the mixing efficiency as high as 85.6% is achieved at Re=0.25 with a single bluff-body structure. It demonstrates that the new design can be used to achieve complete mixing within ultra short length at mciroscale.

Photoluminescence (PL) spectra, light flux, color temperatures and color coordinates of white light emitting diodes that are based on CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution and industrial phosphor were analyzed. The study was carried out continuously for a 1000 h with two white LEDs which based on an exciting InGaN wavelength of 450 nm with a power of 10 W. Luminous flux and color temperatures were investigated during 200, 400, 600, 800 and 1000 h. All experiments were carried out for both CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ and industrial phosphor and comparatively analyzed. Consequently, the application perspectives of CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution in the white LEDs technologies are presented.

In a two-dimensional cellular automaton model of retained excitation every excited cell stays excited if the number of excited neighbors belong to some interval, the cell takes refractory state otherwise. Every resting cell is excited if the number of excited cells in its neighborhood belong to some other interval; cell-state transition from refractory to resting state is unconditional. We classify 1296 rules of retained excitation based on how dynamics of excitable lattices develop after initial stimulation. Several modes of space-time activity dynamics are discovered: not growing but persistent domains of activity, domains with rectangular, octagonal and almost circular growth, amoeba-like growing patterns, mobile and still localizations.

Commonly studied cellular automata are memoryless and have fixed topology of connections between cells. However by allowing updates of links and short-term memory in cells we may potentially discover novel complex regimes of spatio-temporal dynamics. Moreover, by adding memory and dynamical topology to state update rules we somehow forge elementary but nontraditional models of neurons networks (aka neuron layers in frontal parts). In the present paper, we demonstrate how this can be done on a self-inhibitory excitable cellular automata. These automata imitate a phenomenon of inhibition caused by hight-strength stimulus: a resting cell excites if there are one or two excited neighbors, the cell remains resting otherwise. We modify the automaton by allowing cells to have few-steps memories, and create links between neighboring cells removed or generated depending on the states of the cells.

We study the synchronization of bursting cells that are coupled through both excitatory and inhibitory connections. We extend our recent results on networks of Hindmarsh–Rose bursting neurons [Belykh et al., 2014] to coupled Sherman β-cell models and show that the addition of repulsive inhibition to an excitatory network can induce synchronization. We discuss the mechanism of this purely synergenic phenomenon and demonstrate that the inhibition leads to the disappearance of a homoclinic bifurcation that governs the type of synchronized bursting. As a result, the inhibition causes the transition from square-wave to easier-to-synchronize plateau bursting, so that weaker excitation is sufficient to induce bursting synchrony. We dedicate this paper to the memory of Leonid P. Shilnikov, the pioneer of homoclinic bifurcation theory, and emphasize the importance of homoclinic bifurcations for understanding the emergence of synchronized rhythms in bursting networks.

The continuous increment in the performance of classical computers has been driven to its limit. New ways are studied to avoid this oncoming bottleneck and many answers can be found. An example is the Belousov–Zhabotinsky (BZ) reaction which includes some fundamental and essential characteristics that attract chemists, biologists, and computer scientists. Interaction of excitation wave-fronts in BZ system, can be interpreted in terms of logical gates and applied in the design of unconventional hardware components. Logic gates and other more complicated components have been already proposed using different topologies and particular characteristics. In this study, the inherent parallelism and simplicity of Cellular Automata (CAs) modeling is combined with an Oregonator model of light-sensitive version of BZ reaction. The resulting parallel and computationally-inexpensive model has the ability to simulate a topology that can be considered as a one-bit full adder digital component towards the design of an Arithmetic Logic Unit (ALU).

The elastic and inelastic scatterings of deuterons from ${}^{13}$C are registered in a wide range of angles at the laboratory energy of 14.5MeV. Data on the differential cross-sections are treated within both the optical model and coupled-channels method. A new set of optical potential parameters is found. Analyses of the $d{+}^{13}{\mathrm{\text{C}}}^{\ast }$ nuclear reactions are carried out for the levels of excitation 3.089, 8.86 and 9.87MeV. The single particle ${}^{12}\mathrm{\text{C}}+n$, and cluster ${}^9\mathrm{\text{Be}}+\alpha$ models are applied in calculations of differential cross-sections. The calculations show that the state 3.089MeV is populated with the single particle configuration, while the latter bands 8.86MeV and 9.87MeV mainly have the cluster ${}^9\mathrm{\text{Be}}+\alpha$ excitation. The major contribution of the Hoyle state of the core ${}^{12}\mathrm{\text{C}}$ is not observed, but the cluster ${}^9\mathrm{\text{Be}}+\alpha$ configuration is ascertained to be the main contributor to the state 8.86MeV.

Nonlinear energy harvesters were found to be sensitive to excitation conditions. In order to reveal the influence mechanism of the excitation condition on the energy harvesting performance, this paper presents an uncertainty analysis for nonlinear monostable energy harvesters (NMEHs). An improved interval extension based on the second-order Taylor’s series is presented as a new uncertainty analysis method. A mathematic example is used to demonstrate that the bounds of responses based on this method are more accurate than the classic interval extension when the dependence of the response on the uncertain variable is nonlinear. Meanwhile, the results from the Monte Carlo simulation are used to verify the accuracy of the proposed method. It is confirmed that the proposed method is suitable for quantifying the propagation of the uncertain level and frequency of the excitation for the NMEH. The results show that the output voltage of the NMEH is more sensitive to the frequency than the level of excitation, for which the influence mechanism is revealed.

Considering the exciton effect, the polarizability and second polarizability spectra of semiconducting single-wall carbon nanotubes (S-SWCNTs) have been calculated by PPP (Pariser, Parr, and Pople) approximation and the single-excitation configuration interaction (single-CI) method and sum-over-state method. We have studied the nonlinear optical (NLO) properties of the S-SWCNTs with different lengths and diameters. The highest and first peak positions, bandgap, and the spectra shape of the polarizability and second hyperpolarizability change as N (the number of atoms) increases. Also, the peak values of γ_zzzz are very bigger than that for γ_xxxx. Our results indicate that the nonlinear optical properties of fullerenes are similar to S-SWCNTs.

In the visual cortex some neurons respond more strongly to short stimuli than to long ones. This is referred to as "end-stopping" and has been generally attributed to inhibition. The role of inhibition, however, has been difficult to demonstrate. Moreover, modeling has shown that end-stopping can be created solely from excitation. The roles of excitation and inhibition were investigated using intracellular recordings (Anderson et al., 2001, J. Neurosci. 21: 2104–2112). The results of that study were interpreted in favor of inhibition. The present report re-examines these results and finds that they may be in good, perhaps even better, agreement with an excitation model of end-stopping.