Obliqueness

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A A Mamun - One of the best experts on this subject based on the ideXlab platform.

  • Three-dimensional Nonlinear Structures in Magnetized Complex Plasmas
    Plasma Physics Reports, 2019
    Co-Authors: M. N. Haque, A. Mannan, A A Mamun
    Abstract:

    — A three-dimensional multi-component magneto-plasma system consisting of hybrid nonextensive-nonthermal-distributed electrons, positive ions, and immobile negatively charged dust grains is considered to examine the modulational instability (MI) of dust ion-acoustic waves (DIAWs). The reductive perturbation method, which is valid for small but finite amplitude DIAWs, is employed to derive the (3 + 1)-dimensional nonlinear Schrödinger equation (NLSE). The NLSE leads to the MI of DIAWs as well as the formation of dust ion-acoustic rogue waves (DIARWs), which are formed due to the effects of nonlinearity in the propagation of DIAWs. It is found that the basic features (viz. amplitude and width) of the DIAWs and DIARWs (which is formed in the unstable region) are significantly modified by the various plasma parameters such as non-extensive (non-thermal) parameter q (α), number densities of plasma species, threshold modulational Obliqueness ( $${{\theta }_{c}}$$ ), etc. The application of the results in space and laboratory magneto-plasma system is briefly discussed.

  • Ion-Acoustic Solitary Waves and Double Layers in a Magnetized Degenerate Quantum Plasma
    IEEE Transactions on Plasma Science, 2017
    Co-Authors: B. Hosen, M. G. Shah, M. R. Hossen, A A Mamun
    Abstract:

    The properties of ion-acoustic (IA) solitary waves (SWs) and double layers (DLs) in a four-component magnetized degenerate quantum plasma system (containing nondegenerate inertial light ion, both nonrelativistically and ultrarelativistically degenerate electrons and positrons, and immobile heavy ion) are theoretically investigated by the reductive perturbation method. The Korteweg-de Vries (K-dV), the modified K-dV, and the Gardner equations are derived to examine the basic features (viz. amplitude, speed, and width) of IA SWs and DLs. It is found that the effects of the ultrarelativistically degenerate electrons and positrons, stationary heavy ion, external magnetic field (Obliqueness), and so on, significantly modify the basic features of the IA SWs and DLs. The basic features and the underlying physics of IA SWs and DLs, which are relevant to some astrophysical compact objects including white dwarfs and neutron stars, are pinpointed.

  • Korteweg-de Vries-Burgers equation in a multi-component magnetized plasma with nuclei of heavy elements
    Journal of the Korean Physical Society, 2016
    Co-Authors: B. Hosen, A A Mamun, M. Amina, M. R. Hossen
    Abstract:

    The nonlinear properties of ion-acoustic (IA) waves are investigated in a relativistically degenerate magnetized quantum plasma, whose constituents are non-degenerate inertial ions, degenerate electrons and immobile positively-charged heavy elements. For nonlinear studies, the well-known reductive perturbation technique is employed to derive the Korteweg-de Vries-Burger equation in the presence of relativistically degenerate electrons. Numerically, the amplitude, width, and phase speed are shown to be associated with the localized IA solitons, and shocks are shown to be significantly influenced by the various intrinsic parameters relevant to our model. The solitary and the shock wave properties have been to be influenced in the non-relativistic, as well as the ultrarelativistic, limits. The effects of the external magnetic field and the Obliqueness are found to change the basic properties of IA waves significantly. The present analysis can be useful in understanding the collective process in dense astrophysical environments, like there of non-rotating white dwarfs, neutron stars, etc .

  • Instability Analysis of Obliquely Propagating Positron-Acoustic Solitary Waves in Superthermal Plasmas
    IEEE Transactions on Plasma Science, 2015
    Co-Authors: Josim Uddin, Sahadat Alam, Mehdi Masud, Gaji Mazharul Anowar, A A Mamun
    Abstract:

    The basic properties of the obliquely propagating positron-acoustic solitary waves (PASWs) and their multidimensional instability in magnetized electron-positron-ion plasmas consisting of immobile positive ions, mobile cold positrons, and superthermal (κ-distributed) hot positrons and electrons are investigated both numerically and analytically. By employing the reductive perturbation technique, the Zakharov-Kuznetsov equation is derived, which admits the solution of solitary waves. The fundamental features of PASWs are remarkably changed by the Obliqueness, external magnetic field, superthermal parameter of electrons (κe), superthermal parameter of hot positrons (κp), ratio of the electron temperature to hot positron temperature (σ), ratio of the electron number density to cold positron number density (μe), and ratio of the hot positron number density to cold positron number density (μph). It is also found that the instability criterion and the growth rate are significantly modified by the external magnetic field and the propagation directions of both the nonlinear waves and their perturbation modes. This paper can be useful to understand the nonlinear electromagnetic perturbations in space and laboratory plasmas.

  • effects of Obliqueness and strong electrostatic interaction on linear and nonlinear propagation of dust acoustic waves in a magnetized strongly coupled dusty plasma
    Physics of Plasmas, 2014
    Co-Authors: M Shahmansouri, A A Mamun
    Abstract:

    Linear and nonlinear propagation of dust-acoustic waves in a magnetized strongly coupled dusty plasma is theoretically investigated. The normal mode analysis (reductive perturbation method) is employed to investigate the role of ambient/external magnetic field, Obliqueness, and effective electrostatic dust-temperature in modifying the properties of linear (nonlinear) dust-acoustic waves propagating in such a strongly coupled dusty plasma. The effective electrostatic dust-temperature, which arises from strong electrostatic interactions among highly charged dust, is considered as a dynamical variable. The linear dispersion relation (describing the linear propagation characteristics) for the obliquely propagating dust-acoustic waves is derived and analyzed. On the other hand, the Korteweg-de Vries equation describing the nonlinear propagation of the dust-acoustic waves (particularly, propagation of dust-acoustic solitary waves) is derived and solved. It is shown that the combined effects of Obliqueness, magnitude of the ambient/external magnetic field, and effective electrostatic dust-temperature significantly modify the basic properties of linear and nonlinear dust-acoustic waves. The results of this work are compared with those observed by some laboratory experiments.

Christian Y Mardin - One of the best experts on this subject based on the ideXlab platform.

  • oct detected optic nerve head neural canal direction Obliqueness and minimum cross sectional area in healthy eyes
    American Journal of Ophthalmology, 2019
    Co-Authors: Seung Woo Hong, Stuart K. Gardiner, Christy Hardin, Glen P. Sharpe, Shaban Demirel, Christopher A. Girkin, Joseph Caprioli, Hongli Yang, Jeffrey M Liebmann, Christian Y Mardin
    Abstract:

    PURPOSE: To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, Obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. DESIGN: Cross-sectional study. METHODS: After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal Obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. RESULTS: Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P < .001, R2 = 0.158). Neural canal direction was most commonly superior-nasal (55%). Mean neural canal Obliqueness was 39.4° (17.3°). The angular distance between superior and inferior peak RNFLT correlated to neural canal direction (P ≤ .008, R2 = 0.093). CONCLUSIONS: ASCO/BMO offset underlies neural canal direction, Obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

Seung Woo Hong - One of the best experts on this subject based on the ideXlab platform.

  • oct detected optic nerve head neural canal direction Obliqueness and minimum cross sectional area in healthy eyes
    American Journal of Ophthalmology, 2019
    Co-Authors: Seung Woo Hong, Stuart K. Gardiner, Christy Hardin, Glen P. Sharpe, Shaban Demirel, Christopher A. Girkin, Joseph Caprioli, Hongli Yang, Jeffrey M Liebmann, Christian Y Mardin
    Abstract:

    PURPOSE: To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, Obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. DESIGN: Cross-sectional study. METHODS: After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal Obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. RESULTS: Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P < .001, R2 = 0.158). Neural canal direction was most commonly superior-nasal (55%). Mean neural canal Obliqueness was 39.4° (17.3°). The angular distance between superior and inferior peak RNFLT correlated to neural canal direction (P ≤ .008, R2 = 0.093). CONCLUSIONS: ASCO/BMO offset underlies neural canal direction, Obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

  • OCT-Detected Optic Nerve Head Neural Canal Direction, Obliqueness, and Minimum Cross-Sectional Area in Healthy Eyes
    American Journal of Ophthalmology, 2019
    Co-Authors: Seung Woo Hong, Stuart K. Gardiner, Christy Hardin, Glen P. Sharpe, Shaban Demirel, Christopher A. Girkin, Joseph Caprioli, Hongli Yang, Jeffrey M Liebmann
    Abstract:

    Purpose To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, Obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. Design Cross-sectional study. Methods After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal Obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. Results Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P Conclusions ASCO/BMO offset underlies neural canal direction, Obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

Jeffrey M Liebmann - One of the best experts on this subject based on the ideXlab platform.

  • oct detected optic nerve head neural canal direction Obliqueness and minimum cross sectional area in healthy eyes
    American Journal of Ophthalmology, 2019
    Co-Authors: Seung Woo Hong, Stuart K. Gardiner, Christy Hardin, Glen P. Sharpe, Shaban Demirel, Christopher A. Girkin, Joseph Caprioli, Hongli Yang, Jeffrey M Liebmann, Christian Y Mardin
    Abstract:

    PURPOSE: To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, Obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. DESIGN: Cross-sectional study. METHODS: After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal Obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. RESULTS: Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P < .001, R2 = 0.158). Neural canal direction was most commonly superior-nasal (55%). Mean neural canal Obliqueness was 39.4° (17.3°). The angular distance between superior and inferior peak RNFLT correlated to neural canal direction (P ≤ .008, R2 = 0.093). CONCLUSIONS: ASCO/BMO offset underlies neural canal direction, Obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

  • OCT-Detected Optic Nerve Head Neural Canal Direction, Obliqueness, and Minimum Cross-Sectional Area in Healthy Eyes
    American Journal of Ophthalmology, 2019
    Co-Authors: Seung Woo Hong, Stuart K. Gardiner, Christy Hardin, Glen P. Sharpe, Shaban Demirel, Christopher A. Girkin, Joseph Caprioli, Hongli Yang, Jeffrey M Liebmann
    Abstract:

    Purpose To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, Obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. Design Cross-sectional study. Methods After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal Obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. Results Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P Conclusions ASCO/BMO offset underlies neural canal direction, Obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

N. S. Saini - One of the best experts on this subject based on the ideXlab platform.

  • Heavy Nucleus Acoustic Periodic Waves in a Degenerate Relativistic Quantum Plasma
    2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019
    Co-Authors: Manveet Kaur, Kuldeep Singh, N. S. Saini
    Abstract:

    There has been a great interest in studying the relativistic degenerate dense plasmas due to its existence in interstellar compact objects (white dwarfs [1], neutron stars [2] etc.). It is notable that the basic constituents of white dwarfs are mainly positively and negatively charged heavy elements like carbon, oxygen, helium with an envelope of hydrogen gas. The existence of heavy elements (positively and negatively) is found to form in a prestellar stage of the evolution of the universe, when whole matter was compressed to extremely high densities. The degeneracy of the plasma species arises due to Heisenberg's uncertainty principle, and that the uncertainty in the momenta of highly compressed plasma species (which are confined in an extremely small space) is infinitely large. This means that the degenerate plasma species (even though they are extremely cold) must move very fast yielding to a very high pressure, called “degenerate pressure”. It is observed that the degenerate pressure exerted by electrons (light nuclei/ions) depends only on the electron (light nucleus/ion) number density, but not on the electron (light nucleus/ion) temperature. The inter-particle distance in such space and laboratory degenerate relativistic quantum plasma (DRQP) systems is of the order of (or smaller than) the de Broglie wavelength of light plasma particle species, and the relativistic parameters of the light plasma particle species acquire very large values. This means that the quantum as well as relativistic effects become important. We have investigated heavy nucleus-acoustic (HNA) periodic and solitary waves in a degenerate relativistic magneto-rotating quantum plasma (DRMQP) system containing relativistically degenerate electrons and light nuclei, and non-degenerate mobile heavy nuclei. Only positive potential HNA periodic waves and solitons have been found in consonance with the satellite observations [3]. It is shown that the combined effects of external magnetic field strength, rotational frequency and Obliqueness significantly modify the propagation properties of the HNA periodic waves and solitons. The results of this investigation may be useful in understanding the shock waves and solitons in astrophysical compact objects especially white dwarfs and neutron stars.

  • Effect of anisotropic pressure on electron acoustic oscillatory and monotonic shocks in superthermal magnetoplasma
    Radio Science, 2019
    Co-Authors: Kuldeep Singh, N. S. Saini
    Abstract:

    Nonlinear oscillatory and monotonic electron acoustic shock waves in dissipative magnetorotating electron-positron-ion plasmas containing cold dynamical electrons, superthermal electrons, and positrons have been analyzed in the stationary background of massive positive ions. The Korteweg de-Vries-Burgers equation which describes the dynamics of the nonlinear shock structures is derived by using amplitude reductive perturbation technique. The quantitative analysis of impact of different physical parameters on the shock structures is presented here. The electron fluid viscosity plays a pivotal role for the transition of electron acoustic (EA) monotonic to oscillatory shocks and vice versa. It is remarkable that the shock structures are sensitive to the Coriolis force, Obliqueness, electron temperature, and the positrons concentration. The present work may be employed to explore and to understand the formation of electron acoustic shock structures in the space and laboratory plasmas with superthermal electrons and positrons under magnetorotating effects, especially in auroral zone, Van Allen radiation belts, planetary magnetospheres, pulsars, black-hole magnetospheres, etc.

  • Amplitude modulation of three-dimensional low-frequency solitary waves in a magnetized dusty superthermal plasma
    Journal of Theoretical and Applied Physics, 2017
    Co-Authors: A. P. Misra, N. S. Saini
    Abstract:

    The amplitude modulation of three-dimensional (3D) dust ion-acoustic wave (DIAW) packets is studied in a collisionless magnetized plasma with inertial positive ions, superthermal electrons and negatively charged immobile dust grains. By using the reductive perturbation technique, a 3D-nonlinear Schrödinger equation is derived, which governs the slow modulation of DIAW packets. The latter are found to be stable in the low-frequency $$(\omega \omega _{\text {c}}$$ ω > ω c , and the modulational instability is related to the modulational Obliqueness $$(\theta )$$ ( θ ) . Here, $$\omega ~(\omega _{\text {c}})$$ ω ( ω c ) is the nondimensional wave (ion-cyclotron) frequency. It is shown that the superthermal parameter $$\kappa$$ κ , the frequency $$\omega _{\text {c}}$$ ω c as well as the charged dust impurity $$(0

  • Low-frequency shock waves in a magnetized superthermal dusty plasma
    Journal of Theoretical and Applied Physics, 2017
    Co-Authors: B. S. Chahal, Yashika Ghai, N. S. Saini
    Abstract:

    The characteristics of low-frequency shocks in a magnetized dusty plasma comprising of negatively charged dust fluid, kappa-distributed electrons and ions have been investigated. Using the reductive perturbation method, the nonlinear Korteweg de–Vries–Burgers (KdV–B) equation which governs the dynamics of the dust acoustic (DA) shock waves is derived. The characteristics of shock structures are studied under the influence of various plasma parameters, viz. superthermality of ions, magnetic field, electron-to-dust-density ratio, kinematic viscosity, ion-to-electron-temperature ratio and Obliqueness. The combined effects of these physical parameters significantly influence the characteristics of DA shock structures. It is observed that only negative potential shocks exist in a plasma environment comprising of dust fluid and superthermal electrons and ions such as that of Saturn’s magnetosphere.