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In this paper, we investigate the impact of an external magnetic field on the Weibel instability driven by temperature anisotropy in a magnetized plasma. The study provides the influence of electron temperature anisotropy, considering both cold as well as warm ions. We derive expressions for the growth rate Γ (s−1) in each case to quantify the effect of some specific parameters on the instability. For example, the growth rate is plotted against the magnetic field for three distinct cases: considering only electrons, including cold ions, and incorporating warm ions. It is observed that the growth rate decreases as the applied magnetic field increases. Furthermore, the addition of both cold and warm ions to the plasma significantly influences the observed effects. It can be explained as follows: in the presence of cold ions, the growth rate is decreased with an increase in the wave number kz (cm−1). In addition, a decrease in the growth rate is observed with an increasing wave number in the case of warm ions. Therefore, it can be seen that the Weibel instability, propelled by thermal anisotropy, holds significant implications owing to its prevalence in both astrophysical and laboratory plasmas. The findings presented here are expected to contribute to the advancements in magnetic field generation and particle acceleration in various astrophysical phenomena, including gamma-ray bursts, relativistic collisionless shock fronts, radio supernovae, and pulsar winds. [ABSTRACT FROM AUTHOR]

The Weibel instability due to temperature anisotropy of electrons and ions in a plasma in the presence of cold and warm ions is reported. Numerical calculations of the normalized growth rate are carried out when the frequency of electromagnetic waves is greater than or less than the thermal velocity of electrons for typical existing plasma parameters. The normalized growth rate increases with an increasing normalized wave number, and after attaining maxima, it decreases due to thermal effects. Therefore, a parabolic plot is obtained for the growth rate. The threshold values of the growth rate depend on the anisotropy parameters. On increasing the value of the temperature anisotropy ratio of either plasma component, the observed growth rate increases. There is a considerable and contrasting effect of the presence of cold and warm ions on the growth rate of the Weibel instability in the plasma. The addition of cold ions stabilizes the instability and reduces the maximum growth rate values, while the addition of warm ions to the plasma increases the instability with a considerable decrease in the domain of instability. Our theoretical investigations of the effect of temperature anisotropy on the growth rate of the Weibel instability are in good agreement with the existing experimental results. [ABSTRACT FROM AUTHOR]

In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here. [ABSTRACT FROM AUTHOR]

The effect of fluctuations of dust grains on the parametric up conversion of lower hybrid waves into a whistler wave in a complex plasma is studied. In a complex plasma, which contains ambient magnetic field, the lower hybrid pump possessing a large amplitude decays into two modes: a whistler wave mode and a lower hybrid wave mode having low frequency. Furthermore, a ponderomotive force is exerted by the lower hybrid pump and whistler side bands on the existing electrons, which drives the lower hybrid decay mode. Furthermore, the coupling of v ⃗ 1 , the oscillatory velocity of low-frequency lower hybrid waves, along with the density perturbations, produces a nonlinear current, which drives the whistler mode. The growth rate Γ (sec−1) of lower hybrid waves scales linearly with the amplitude of the pump waves, and it increases as the amplitude of the lower hybrid pump waves increase. Moreover, the dust grain charges influence the instability appreciably. Our theoretically observed growth rate decreases with the increase in the relative density d = n 0 i / n 0 e of negatively charged dust grains, while it decreases with the size of dust grains a (μm). The growth rate varies inversely to the electron cyclotron frequency ωce, and it decreases as ωce increases. The results presented in the article are efficiently able to elaborate the basics of the whistler wave excitation in complex plasmas, space plasmas, processing in solid state plasmas, fusion plasmas, and laboratory plasmas as well as industrial plasmas. [ABSTRACT FROM AUTHOR]

We have investigated the structural and magnetization properties of the nanocrystalline Pr0.7Ba0.2Ca0.1MnO3 sample, synthesized using the sol–gel method. The Rietveld refinement of the X-ray diffraction pattern of the nanocrystalline sample (recorded at room temperature) confirmed the formation of the orthorhombic crystal structure with Pnma space group. The temperature dependent magnetization M(T) measurements suggested that the present sample undergoes a paramagnetic to ferromagnetic phase transition and the Curie temperature was found to be ∼ 126 K. The positive slopes observed from the Arrott plots for the present sample indicate the second order of magnetic phase transition, as per the Banerjee's criterion. The maximum value of magnetic entropy change | Δ S M m a x | and relative cooling power (RCP) were found to be ∼ 2.2 J kg-1K-1 and 261 Jkg-1 for a magnetic field change of 5 T. The phenomenological universal curve was constructed for the present sample and ΔSM curves were found to collapse into one, and the universal curve confirmed the second order of magnetic phase transition. The relatively large values of |ΔSM| and RCP make the present nanocrystalline compound promising for the magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

The quality performance analysis of any solar cell can only be predicted through the parameters extracted from its current-voltage characteristics. Herein, we demonstrate an efficient analytical method to calculate the series resistance of organic solar cells without any pre approximation. It has been shown that the inaccuracy in series resistance takes place due to the high ideality factor of the organic based solar cells, usually ranging from 2-5. Using a systemic approach, we solved the single diode solar cell model to determine the series resistance expression. The dependence of series resistance on ideality factor of the device and the reverse saturation current calculation through the illuminated current-voltage characteristics has been presented here for the first time. The entire method has been programmatically realized in MATLAB. The extracted parameters values have been compared to the other methods for the proof of validation and it shows good agreement where as some outputs are better resolved. Additionally, the effectiveness of the present method is also matched with NREL certified silicon solar cell (reference cell model 60623) parameter extracted from K24XX cell software provided with PET cell tester model, CT200AAA solar simulators. The present proposed method is not restricted to the organic solar cell only but it can also be applied for the other type of solar cell as well. Therefore, the proposed method shows the relevance in the present scenario of solar cell research and development. [ABSTRACT FROM AUTHOR]

Despite being of wide commercial use in devices, the orders of magnitude increase in resistance that can be seen in some semiconducting BaTiO3-based ceramics, on heating through the Curie temperature (TC), is far from well understood. Current understanding of the behavior hinges on the role of grain boundary resistance that can be modified by polarization discontinuities which develop in the ferroelectric state. However, direct nanoscale resistance mapping to verify this model has rarely been attempted, and the potential approach to engineer polarization states at the grain boundaries, that could lead to optimized positive temperature coefficient (PTC) behavior, is strongly underdeveloped. Here we present direct visualization and nanoscale mapping in a commercially optimized BaTiO3-PbTiO3-CaTiO3 PTC ceramic using Kelvin probe force microscopy, which shows that, even in the low resistance ferroelectric state, the potential drop at grain boundaries is significantly greater than in grain interiors. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy reveal new evidence of Pb-rich grain boundaries symptomatic of a higher net polarization normal to the grain boundaries compared to the purer grain interiors. These results validate the critical link between optimized PTC performance and higher local polarization at grain boundaries in this specific ceramic system and suggest a novel route towards engineering devices where an interface layer of higher spontaneous polarization could lead to enhanced PTC functionality. [ABSTRACT FROM AUTHOR]

The rheology of model dendrimers with excluded volume interactions is investigated within the framework of the Rouse-Zimm theory. Excluded volume between the nearest nonbonded monomers of dendrimers is evaluated within the mean-field approximation along the lines of Flory's theory. This theory also rationalizes the earlier developed geometric approach for determining the angular excluded volume parameters. This model captures the characteristic maxima of the intrinsic viscosity as a function of the generations of growth. The overall feature of the intrinsic viscosity of dendrimers with varying excluded volume parameters displays a good quantitative match with those reported in earlier theory, experiments, and simulations. The mechanical moduli of model dendrimers agree well with the Brownian dynamics simulation data. [ABSTRACT FROM AUTHOR]

Spatial variability of conductivity in ceria is explored using scanning probe microscopy with galvanostatic control. Ionically blocking electrodes are used to probe the conductivity under opposite polarities to reveal possible differences in the defect structure across a thin film of CeO2. Data suggest the existence of a large spatial inhomogeneity that could give rise to constant phase elements during standard electrochemical characterization, potentially affecting the overall conductivity of films on the macroscale. The approach discussed here can also be utilized for other mixed ionic electronic conductor systems including memristors and electroresistors, as well as physical systems such as ferroelectric tunneling barriers. [ABSTRACT FROM AUTHOR]

The resistive switching characteristics of TiO2 thin films were investigated using conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM). The as-prepared TiO2 thin films were modulated into higher and lower resistance states by applying a local electric field. We showed that the resistive switching results from charge injection and release assisted by electro-migration of oxygen ions. An integrated model combined with filamentary and interfacial effects was utilized to elucidate the experimentally observed phenomenon. [ABSTRACT FROM AUTHOR]

The orientation, microstructure, and rheology in non-Brownian shear flow were studied for suspensions of dicolloidal particles using a novel particle mesh Ewald Stokesian dynamics algorithm for anisotropic particles. Four different particle shapes were studied with dicolloids modeled as the union of two intersecting spheres. Dynamic simulations were conducted for periodic systems of 1000 particles for volume fractions [lowercase_phi_synonym]=0.05-0.55. The suspension microstructure was disordered for all particle shapes at 0≤[lowercase_phi_synonym]≤0.50, with some systems showing ordered microstructure at [lowercase_phi_synonym]=0.55. The viscosity in the disordered state was similar for all particle shapes at equal volume fraction. Negative first and second normal-stress differences were found for [lowercase_phi_synonym]≤0.5, but positive values were observed for certain ordered systems at [lowercase_phi_synonym]=0.55. Complex orientation behavior was observed as a function of volume fraction and particle shape. All particles showed an orientation shift toward the vorticity axis for [lowercase_phi_synonym]≥0.10. Certain shapes showed a shift away from the vorticity axis for [lowercase_phi_synonym]≤0.10. The high [lowercase_phi_synonym] orientation dynamics were consistent with predictions based on the mobility tensor MωS relating the angular velocity to particle stresslet. The orientation dynamics were dominated by the second normal-stress difference. The shift away from the vorticity axis for small [lowercase_phi_synonym] was induced by migration away from orientations with large orientation fluctuations. [ABSTRACT FROM AUTHOR]