Influence Of Dispersion Effects Research Articles

Conformational preferences and intramolecular hydrogen bonding patterns of tetraflavaspidic acid BBBB – a tetrameric acylphloroglucinol

Abstract Tetraflavaspidic acid BBBB is a tetrameric acylphloroglucinol of natural origin isolated from Dryopteris aitoniana. Its molecule consists of four acylphloroglucinol units linked by methylene bridges and having the same R = propyl in their R−C=O groups. In one of the terminal monomers, one of the OHs ortho to R−C=O is replaced by a keto O. The paper reports the results of a conformational study performed at the HF/6-31G(d,p) and DFT/B3LYP/6-31+G(d,p) levels; two options are utilised for the latter, without and with the inclusion of the Grimme’s dispersion correction. Given the importance of intramolecular hydrogen bonds (IHBs) for the stabilisation of acylphloroglucinol conformers, only conformers containing the maximum IHBs’ number were calculated. The IHBs comprise an IHB between the sp2 O of R−C=O and a neighbouring OH in each monomeric unit and two inter-monomer IHBs between each pair of units. The single C−C bonds of the methylene bridges enable a variety of mutual orientations of the monomeric units, giving rise to a variety of conformations and IHB patterns. The results indicate greater stability for conformers in which individual monomers take lower energy conformations, and significant influence of the dispersion correction on the estimation of the energetics and of other molecular properties. The inclusion of the dispersion correction also strongly limits the number of low energy conformers. The influence of dispersion effects is consistent with the presence of four aromatic rings.

Explicit Weierstrass $$\wp $$ Traveling Wave Solution and Stability of Dispersive Solutions to the Kadomtsev–Petviashvili Equation with Competing Dispersion Effect

In this article, we address the Kadomtsev–Petviashvili (KP) equation in which a small competing dispersion effect is present. We examine the nature of solutions under the influence of dispersion effect by exploiting dynamical system theory and Lyapunov function. We prove the existence of bounded traveling wave solutions when KP equation has external dispersion effect. The retrieved traveling wave solutions are in the form of solitary waves, periodic and elliptic functions. We obtain the general solution of the equation in presence and absence of the dispersion effect in terms of Weirstrass $$\wp $$ functions and Jacobi elliptic functions. Furthermore, we apply a new method which is based on factorization method, use of functional transformation and the Abel’s first order nonlinear equation and obtain a new form of kink-type solutions. Finally, we analyze the stability analysis of the dispersive solutions explicitly by using dynamical system theory. We show that the traveling wave velocity behaves like a bifurcation parameter which classifies different classes of waves. Moreover, we also obtain a transcritical bifurcation which occurs at a critical velocity.

Synthesis of Li2FeSiO4/C composite cathode material for Li-ion batteries and influence of dispersion effect on electrochemical characteristics

In this work, a next generation of perspective cathode material for Li-ion batteries Li2FeSiO4/C composite was synthesized by the sol-gel method, followed by heat treatment. Glucose monohydrate was used as a reducing agent and a soot-forming additive. The influence of morphology and particle size on the electrochemical characteristics of the cathode material after grinding in a bead attritor are shown. Discharge capacity at current 0.1 C was equaled 137 mAhg−1, after 100 charge-discharge cycles the capacity was 112 mAhg−1. Cyclic voltamperometry was demonstrated better electrochemical reactions in Li2FeSiO4/C after additional shredding of initial materials, the specific capacitance of a sample during a discharge with currents of 0.5C, 1C, and 2C was also demonstrated.

All-optical or logic gate based on a photonic crystal fiber Michelson interferometer operating with pulse-position modulation

We present a numerical investigation of the study of the Michelson interferometer by exploring the potential of such a device to act as an all-optical logic gate when excited with ultrashort pulses of 100 fs. The input pulse is controlled by a pulse-position modulation (PPM) modulator, which has the role of controlling the value and direction of the temporal displacement from the variation of the PPM modulating factor. We present the study on the signal-to-noise ratio (SNR), which served as the basis for constructing a merit figure of the studied logic gates in order to verify their performance. We considered pulse propagation under the influence of dispersive effects, as well as the nonlinear effects in the propagation regime with no loss for the input pulses. It was possible to implement the OR logic operation in at least one interval of the modulation adjustment parameter in each of the distinct pumping power regimes, thus obtaining a total of nine intervals of OR logic gate. The situation with the best SNR = 29.36 dB, for the suggested logic gate operation, was found at the power of 150 kW with the modulation adjustment parameter e = 43 fs. Numerical studies were done from the coupled–coupled equations solved using the fourth-order Runge–Kutta method. The implementation of fully optical logic gates tends to revolutionize digital systems in the field of data storage, such as optical memory, “replacement” of electronic circuits among other applications.

Theoretical study on the initial reaction mechanisms of ansa-metallocene zirconium precursor on hydroxylated Si(1 0 0) surface.

The initial reaction mechanisms for depositing ZrO2 thin films using ansa-metallocene zirconium (Cp2CMe2)ZrMe2 precursor were studied by density functional theory (DFT) calculations. The (Cp2CMe2)ZrMe2 precursor could be absorbed on the hydroxylated Si(1 0 0) surface via physisorption. Possible reaction pathways of (Cp2CMe2)ZrMe2 were proposed. For each reaction, the activation energies and reaction energies were compared, and stationary points along the reaction pathways were shown. In addition, the influence of dispersion effects on the reactions was evaluated by non-local dispersion corrected DFT calculations.

Maslov’s canonical operator, Hörmander’s formula, and localization of the Berry-Balazs solution in the theory of wave beams

For three-dimensional Schrodinger equations, we study how to localize exact solutions represented as the product of an Airy function (Berry-Balazs solutions) and a Bessel function and known as Airy-Bessel beams in the paraxial approximation in optics. For this, we represent such solutions in the form of Maslov’s canonical operator acting on compactly supported functions on special Lagrangian manifolds. We then use a result due to Hormander, which permits using the formula for the commutation of a pseudodifferential operator with Maslov’s canonical operator to “move” the compactly supported amplitudes outside the canonical operator and thus obtain effective formulas preserving the structure based on the Airy and Bessel functions. We discuss the influence of dispersion effects on the obtained solutions.

Numerical study of the influence of dispersion effects on properties of filtration combustion waves with complex chemical kinetics

A one-dimensional, two-temperature stationary model of filtration combustion with complex chemical kinetics has been developed. The influence of the phenomena of gas diffusion and heat conduction on the properties of the filtration combustion wave has been investigated.

Modification of Engineering Return-Stroke Models to Include Dispersion Effects

Recently, Baba and Ishii (see ibid., vol.44, p.476-7, Aug. 2002) have presented a method to modify the transmission-line (TL) type model to incorporate current distortion. In this brief, we generalize their method, as well as an exponential decay return stroke speed model, to simple engineering return-stroke models, and investigate the influence of dispersion effects on associated electromagnetic fields. Results show that the proposed modification to the models eliminates the inherent discontinuity in the traveling current source (TCS) model and the Bruce-Golde (BG) model at the upward-moving front. In addition, it turns out that an increase in the current risetime with height does not have significant effect on magnetic hump, electric ramp, and distant zero crossing, while a rapid decrease in return stroke speed with height could affect these features.

Frequency-tunable supercontinuum generation in photonic-crystal fibers by femtosecond pulses of an optical parametric amplifier

Supercontinuum emission is generated by the propagation of frequency-tunable femtosecond pulses of 1.1–1.5-µm radiation of an optical parametric amplifier through a photonic-crystal fiber. Nearly an octave’s spectral broadening was observed when laser pulses with a duration of 80–100 fs and an energy of several nanojoules per pulse were coupled into a photonic-crystal fiber with a core radius of 1.5–3 µm. The spectral broadening of femtosecond pulses at 1.1–1.5 µm is shown to be much more efficient than the spectral broadening of femtosecond pulses of 800-nm Ti:sapphire laser radiation. The role of dispersion in spectral broadening and supercontinuum generation is discussed. In experiments on supercontinuum generation with an optical parametric amplifier, the influence of dispersion effects was reduced by decreasing the size of the fiber core, which allowed the efficiency of supercontinuum generation to be improved without increasing the laser intensity.

Design of Simulated Moving Bed Units under Nonideal Conditions

The influence of dispersive effects (axial mixing and mass-transport resistance) on the performance of simulated moving bed (SMB) units is studied through detailed modeling. The results are represe...