Shabbir Ahmad Khan - Academia.edu (original) (raw)
Papers by Shabbir Ahmad Khan
Chinese Journal of Physics
Astrophysics and Space Science, 2014
ABSTRACT In this paper we study the coexisting low frequency oscillations in strongly degenerate,... more ABSTRACT In this paper we study the coexisting low frequency oscillations in strongly degenerate, magnetized, (electron-positron) pair and warm pair-ion plasma. The dispersion relations are obtained for both the cases in macroscopic quantum hydrodynamics approximation. In pair-ion case, the dispersion equation shows coupling of electrostatic and (shear) electromagnetic modes under certain circumstances with important role of ion temperature. Domain of existence of such waves and their relevance to dense degenerate astrophysical plasmas is pointed out. Results are analyzed numerically for typical systems with variation of ion concentration and ion temperature.
Physics of Plasmas, 2008
The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum ele... more The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum electron-ion plasma are studied. The effect of stationary dust on an electrostatic mode is also investigated. The quantum corrections in the linear dispersion relations of a cold dense plasma are presented with possible applications.
Physics of Plasmas, 2008
The obliquely propagating two-dimensional quantum dust ion-acoustic solitary waves in a magnetize... more The obliquely propagating two-dimensional quantum dust ion-acoustic solitary waves in a magnetized quantum dusty plasma are studied by using the quantum hydrodynamic model. A linear dispersion relation is obtained using the Fourier analysis, and a nonlinear quantum Zakharov-Kuznetsov equation is derived for small-amplitude perturbations. A stationary solution of this equation is obtained to investigate the effects of quantum corrections, concentration of dust particles, and the angle of propagation on the amplitude, width, and energy of the soliton. The relevance of the present investigation to the astrophysical dusty plasmas is discussed.
Physics of Plasmas, 2007
We present for the first time fully analytic results for multi-loop equal-mass ice cone graphs in... more We present for the first time fully analytic results for multi-loop equal-mass ice cone graphs in two dimensions. By analysing the leading singularities of these integrals, we find that the maximal cuts in two dimensions can be organised into two copies of the same periods that describe the Calabi-Yau varieties for the equal-mass banana integrals. We obtain a conjectural basis of master integrals at an arbitrary number of loops, and we solve the system of differential equations satisfied by the master integrals in terms of the same class of iterated integrals that have appeared earlier in the context of equal-mass banana integrals. We then go on and show that, when expressed in terms of the canonical coordinate on the moduli space, our results can naturally be written as iterated integrals involving the geometrical invariants of the Calabi-Yau varieties. Our results indicate how the concept of pure functions and transcendental weight can be extended to the case of Calabi-Yau varieties. Finally, we also obtain a novel representation of the periods of the Calabi-Yau varieties in terms of the same class of iterated integrals, and we show that the well-known quadratic relations among the periods reduce to simple shuffle relations among these iterated integrals.
Physics of Plasmas, 2007
The characteristics and stability of ion acoustic solitary wave with transverse perturbations are... more The characteristics and stability of ion acoustic solitary wave with transverse perturbations are examined in ultracold quantum magnetospheric plasma consisting of electrons, positrons, and ions. Using the quantum hydrodynamic model, a dispersion relation in the linear regime, and the Kadomtsev-Petviashvili equation in the nonlinear regime are derived. The quantum corrections are studied through quantum statistics and diffraction effects. It is found that compressive solitary wave can propagate in this system. The quantum effects are also studied graphically for both linear and nonlinear profiles of ion acoustic wave. Using energy consideration method, conditions for existence of stable solitary waves are obtained. It is found that stable solitary waves depend on quantum corrections, positron concentration, and direction cosine of the wave vector k along the x axis.
Physics of Plasmas, 2012
Low frequency electrostatic and electromagnetic waves are investigated in ultra-dense quantum mag... more Low frequency electrostatic and electromagnetic waves are investigated in ultra-dense quantum magnetoplasma with relativistic-degenerate electron and non-degenerate ion fluids. The dispersion relation is derived for mobile as well as immobile ions by employing hydrodynamic equations for such plasma under the influence of electromagnetic forces and pressure gradient of relativistic-degenerate Fermi gas of electrons. The result shows the coexistence of shear Alfven and ion modes with relativistically modified dispersive properties. The relevance of results to the dense degenerate plasmas of astrophysical origin (for instance, white dwarf stars) is pointed out with brief discussion on ultra-relativistic and non-relativistic limits.
Physics of Plasmas, 2014
In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution f... more In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution function (Lorentzian or kappa), it is shown that a kinetic instability of dust-acoustic mode exists. The instability threshold is affected when such (quasineutral) plasma permeates through another static plasma. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust. In the limits of phase velocity of the waves larger and smaller than the thermal velocity of dust particles, the dispersion properties and growth rate of dust-acoustic mode are investigated analytically with validation via numerical analysis.
Astrophysics and Space Science, 2013
Theoretical investigation is carried out to understand the dynamics and stability of three dimens... more Theoretical investigation is carried out to understand the dynamics and stability of three dimensional ion solitary waves propagating in dense plasma comprising of ultra-relativistic degenerate electrons and positrons and warm ions. A linear dispersion relation is derived which shows a strong dependence of wave on positron concentration (through the change of density balance) and ion-to-degenerate electron temperature ratio. A nonlinear Kadomtsev-Petviashvili equation is derived by employing the reductive perturbation technique and solved analytically and the conditions for existence of stable solitary waves are found. The analysis reveals that only compressive solitary waves exist in the system. Effects of the change of density balance and Fermi temperature ratios are studied in detail, both analytically and numerically. Furthermore, the conditions for stable solitary waves are discussed by using energy consideration method. The numerical results are also presented by using the parameters consistent with the degenerate and ultrarelativistic astrophysical plasmas.
Plasma and Fusion Research, 2016
By employing the integral formulation of dielectric tensor, we have introduced the kinetic full w... more By employing the integral formulation of dielectric tensor, we have introduced the kinetic full wave analysis of ordinary-extraordinary-Bernstein (O-X-B) mode conversion in tokamak plasma in one dimension on the basis of TASK/W1 code using the finite element method. The boundary value problem of Maxwell's equation is solved and the finite Larmor radius effects are represented by integral formulation. The OX -B mode conversion and the absorption near the cyclotron harmonic resonance are successfully described.
Indian Journal of Physics, 2013
ABSTRACT By employing quantum hydrodynamic formulation, oblique propagation of electrostatic ion ... more ABSTRACT By employing quantum hydrodynamic formulation, oblique propagation of electrostatic ion waves and nonlinear structures are investigated in a magnetized dense Fermi plasma. Constituents are quantum (degenerate) electrons and non-degenerate mobile ions in presence of stationary massive ions (either positive or negative) in background. To reveal features of low frequency ion waves, where effects of Fermi degeneracy and quantum diffraction are significant, linear dispersion equation is derived by Fourier analysis of model equations. Nonlinear solitary pulse solution in low-amplitude limit is obtained via Korteweg de Vries equation. It is shown that wave dispersion due to electron Fermi pressure is important at very short wavelength regime. Effects of concentration of heavy ions and angle of propagation on wave are also studied. Results are discussed numerically with relevance of superdense plasmas mainly found in astrophysical regimes.
ABSTRACT Low frequency electrostatic and electromagnetic waves in a dense magnetoplasma are studi... more ABSTRACT Low frequency electrostatic and electromagnetic waves in a dense magnetoplasma are studied. The dispersive contribution of electron quantum effects in an electron-ion plasma in the presence of positively or negatively charged dust particles in the background is emphasized. By employing the quantum hydrodynamic model, a linear dispersion relation is derived which shows coupling of electrostatic and shear Alfven modes which shows influence of electron quantum effects and dust density.
Physics of Plasmas, 2009
The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized... more The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized dense electron-positron-ion plasma. For this purpose, the quantum hydrodynamic model is employed to derive a deformed Korteweg-de Vries (dKdV) equation. The steady state double layer solution of dKdV equation is obtained and its dependence on various parameters is discussed. It is found that only compressive double layers can exist in such plasmas. The analytical and numerical studies reveal that the quantum ion-acoustic double layer structures strongly depend on quantum diffraction effects and positron number density.
Acoustic Waves, 2010
Contrary to classical plasmas, the number density of degenerate electrons, positrons/holes in qua... more Contrary to classical plasmas, the number density of degenerate electrons, positrons/holes in quantum plasmas is extremely high and they obey Fermi-Dirac statistics whereas the temperature is very low. Plasma and quantum mechanical effects co-exist in such systems and many unusual effects like tunneling of electrons, quantum destabilization, pressure ionization, Bose-Einstein condensation and crystallization etc. may be equally important (Bonitz et al., 2009). Their properties in equilibrium and nonequilibrium are governed by many-body effects (collective and correlation effects) which require quantum statistical theories and versatile computational techniques. The average inter-particle distance n-1/3 (where n is the particle density) is comparable with electron thermal de Broglie wavelength
Indian Journal of Physics, 2014
In this study, a potentiometric urea biosensor has been fabricated on glass filter paper through ... more In this study, a potentiometric urea biosensor has been fabricated on glass filter paper through the immobilization of urease enzyme onto chitosan/cobalt oxide (CS/Co 3 O 4) nanocomposite. A copper wire with diameter of 500 lm is attached with nanoparticles to extract the voltage output signal. The shape and dimensions of Co 3 O 4 magnetic nanoparticles are investigated by scanning electron microscopy and the average diameter is approximately 80-100 nm. Structural quality of Co 3 O 4 nanoparticles is confirmed from X-ray powder diffraction measurements, while the Raman spectroscopy has been used to understand the chemical bonding between different atoms. The magnetic measurement has confirmed that Co 3 O 4 nanoparticles show ferromagnetic behavior, which could be attributed to the uncompensated surface spins and/or finite size effects. The ferromagnetic order of Co 3 O 4 nanoparticles is raised with increasing the decomposition temperature. A physical adsorption method is adopted to immobilize the surface of CS/Co 3 O 4 nanocomposite. Potentiometric sensitivity curve has been measured over the concentration range between 1 9 10-4 and 8 9 10-2 M of urea electrolyte solution revealing that the fabricated biosensor holds good sensing ability with a linear slope curve of *45 mV/ decade. In addition, the presented biosensor shows good reusability, selectivity, reproducibility and resistance against interferers along with the stable output response of *12 s.
Physics of Plasmas, 2014
ABSTRACT The kinetic theory of electron plasma waves with finite orbital angular momentum has rec... more ABSTRACT The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.
Springer Series on Atomic, Optical, and Plasma Physics, 2014
Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope ... more Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope of potential applications, ranging from nano-scale science in condensed matter to the vast scales of astrophysical objects. The theoretical description of quantum plasmas relies on various approaches, microscopic or macroscopic, some of which have obvious relation to classical plasma models. The appropriate model should, in principle, incorporate the quantum mechanical effects such as diffraction, spin statistics and correlations, operative on the relevant scales. However, first-principle approaches such as quantum Monte Carlo and density functional theory or quantum-statistical methods such as quantum kinetic theory or nonequilibrium Green's functions require substantial theoretical and computational efforts. Therefore, for selected problems, alternative simpler methods have been put forward. In particular, the collective behavior of many-body systems is usually described within a self-consistent scheme of particles and fields on the mean-field level. In classical plasmas, further simplifications are achieved by a transition to hydrodynamic equations. Similar fluid-type descriptions for quantum plasmas have been proposed and widely used in the recent decade. This chapter is devoted to an overview of the main concepts of quantum hydrodynamics (QHD), thereby critically analyzing its validity range and its main limitations. Furthermore, the results of the linearized QHD in unmagnetized and magnetized plasmas and a few nonlinear solutions are examined with illustrations. The basic concepts and formulation of particle-particle interactions are also reviewed at the end, indicating their possible consequences in quantum many-body problems.
Physics of Plasmas, 2010
The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron pla... more The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron plasmas in the presence of stationary ions. The quantum hydrodynamic model is employed and reductive perturbation method is used to derive the Korteweg-de Vries (KdV) and extended KdV equations for solitons and double layers, respectively. It is found that in the linear limit both slow acoustic and fast Langmuir waves can propagate in such type of quantum plasmas like in classical pair-ion or pair plasmas. The amplitude and width of the electrostatic solitons are found to be decreasing with the increase in concentration of positrons (or decrease in the concentration of ions) in degenerate electron-positron-ion plasmas. It is found that only rarefactive double layer can exist in such plasmas which depend on various parameters. The dependence of double layer structure on ion concentration and quantum diffraction effects of electrons and positrons are also discussed. The results are also elaborated graphically by considering dense plasma parameters in the outer layers of astrophysical objects such as white dwarfs and neutron stars.
Physics of Plasmas, 2008
... H. Ur-Rehman, SA Khan, W. Masood, M. Siddiq. ... A variety of modes have been discussed in du... more ... H. Ur-Rehman, SA Khan, W. Masood, M. Siddiq. ... A variety of modes have been discussed in dusty plasmas, such as dust ion acoustic (DIA) waves, dust acoustic (DA) waves, and dust lattice (DL) waves in unmagnetized dusty plasmas, whereas dust drift (DD) modes, Shukla ...
Physics of Plasmas, 2008
ABSTRACT Obliquely propagating linear and weakly nonlinear ion-acoustic waves in a magnetized qua... more ABSTRACT Obliquely propagating linear and weakly nonlinear ion-acoustic waves in a magnetized quantum plasma are investigated by employing the quantum hydrodynamic formulation. A linear dispersion relation is presented and the nonlinear Korteweg–de Vries equation is derived using the reductive perturbative method. The dispersion caused by the quantum diffraction effects is possible only in a very short wavelength regime. The amplitude and width of the solitons formed by the ion-acoustic waves propagating in a magnetized plasma depend upon various parameters. Possible applications of the results to dense plasmas are discussed.
Chinese Journal of Physics
Astrophysics and Space Science, 2014
ABSTRACT In this paper we study the coexisting low frequency oscillations in strongly degenerate,... more ABSTRACT In this paper we study the coexisting low frequency oscillations in strongly degenerate, magnetized, (electron-positron) pair and warm pair-ion plasma. The dispersion relations are obtained for both the cases in macroscopic quantum hydrodynamics approximation. In pair-ion case, the dispersion equation shows coupling of electrostatic and (shear) electromagnetic modes under certain circumstances with important role of ion temperature. Domain of existence of such waves and their relevance to dense degenerate astrophysical plasmas is pointed out. Results are analyzed numerically for typical systems with variation of ion concentration and ion temperature.
Physics of Plasmas, 2008
The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum ele... more The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum electron-ion plasma are studied. The effect of stationary dust on an electrostatic mode is also investigated. The quantum corrections in the linear dispersion relations of a cold dense plasma are presented with possible applications.
Physics of Plasmas, 2008
The obliquely propagating two-dimensional quantum dust ion-acoustic solitary waves in a magnetize... more The obliquely propagating two-dimensional quantum dust ion-acoustic solitary waves in a magnetized quantum dusty plasma are studied by using the quantum hydrodynamic model. A linear dispersion relation is obtained using the Fourier analysis, and a nonlinear quantum Zakharov-Kuznetsov equation is derived for small-amplitude perturbations. A stationary solution of this equation is obtained to investigate the effects of quantum corrections, concentration of dust particles, and the angle of propagation on the amplitude, width, and energy of the soliton. The relevance of the present investigation to the astrophysical dusty plasmas is discussed.
Physics of Plasmas, 2007
We present for the first time fully analytic results for multi-loop equal-mass ice cone graphs in... more We present for the first time fully analytic results for multi-loop equal-mass ice cone graphs in two dimensions. By analysing the leading singularities of these integrals, we find that the maximal cuts in two dimensions can be organised into two copies of the same periods that describe the Calabi-Yau varieties for the equal-mass banana integrals. We obtain a conjectural basis of master integrals at an arbitrary number of loops, and we solve the system of differential equations satisfied by the master integrals in terms of the same class of iterated integrals that have appeared earlier in the context of equal-mass banana integrals. We then go on and show that, when expressed in terms of the canonical coordinate on the moduli space, our results can naturally be written as iterated integrals involving the geometrical invariants of the Calabi-Yau varieties. Our results indicate how the concept of pure functions and transcendental weight can be extended to the case of Calabi-Yau varieties. Finally, we also obtain a novel representation of the periods of the Calabi-Yau varieties in terms of the same class of iterated integrals, and we show that the well-known quadratic relations among the periods reduce to simple shuffle relations among these iterated integrals.
Physics of Plasmas, 2007
The characteristics and stability of ion acoustic solitary wave with transverse perturbations are... more The characteristics and stability of ion acoustic solitary wave with transverse perturbations are examined in ultracold quantum magnetospheric plasma consisting of electrons, positrons, and ions. Using the quantum hydrodynamic model, a dispersion relation in the linear regime, and the Kadomtsev-Petviashvili equation in the nonlinear regime are derived. The quantum corrections are studied through quantum statistics and diffraction effects. It is found that compressive solitary wave can propagate in this system. The quantum effects are also studied graphically for both linear and nonlinear profiles of ion acoustic wave. Using energy consideration method, conditions for existence of stable solitary waves are obtained. It is found that stable solitary waves depend on quantum corrections, positron concentration, and direction cosine of the wave vector k along the x axis.
Physics of Plasmas, 2012
Low frequency electrostatic and electromagnetic waves are investigated in ultra-dense quantum mag... more Low frequency electrostatic and electromagnetic waves are investigated in ultra-dense quantum magnetoplasma with relativistic-degenerate electron and non-degenerate ion fluids. The dispersion relation is derived for mobile as well as immobile ions by employing hydrodynamic equations for such plasma under the influence of electromagnetic forces and pressure gradient of relativistic-degenerate Fermi gas of electrons. The result shows the coexistence of shear Alfven and ion modes with relativistically modified dispersive properties. The relevance of results to the dense degenerate plasmas of astrophysical origin (for instance, white dwarf stars) is pointed out with brief discussion on ultra-relativistic and non-relativistic limits.
Physics of Plasmas, 2014
In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution f... more In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution function (Lorentzian or kappa), it is shown that a kinetic instability of dust-acoustic mode exists. The instability threshold is affected when such (quasineutral) plasma permeates through another static plasma. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust. In the limits of phase velocity of the waves larger and smaller than the thermal velocity of dust particles, the dispersion properties and growth rate of dust-acoustic mode are investigated analytically with validation via numerical analysis.
Astrophysics and Space Science, 2013
Theoretical investigation is carried out to understand the dynamics and stability of three dimens... more Theoretical investigation is carried out to understand the dynamics and stability of three dimensional ion solitary waves propagating in dense plasma comprising of ultra-relativistic degenerate electrons and positrons and warm ions. A linear dispersion relation is derived which shows a strong dependence of wave on positron concentration (through the change of density balance) and ion-to-degenerate electron temperature ratio. A nonlinear Kadomtsev-Petviashvili equation is derived by employing the reductive perturbation technique and solved analytically and the conditions for existence of stable solitary waves are found. The analysis reveals that only compressive solitary waves exist in the system. Effects of the change of density balance and Fermi temperature ratios are studied in detail, both analytically and numerically. Furthermore, the conditions for stable solitary waves are discussed by using energy consideration method. The numerical results are also presented by using the parameters consistent with the degenerate and ultrarelativistic astrophysical plasmas.
Plasma and Fusion Research, 2016
By employing the integral formulation of dielectric tensor, we have introduced the kinetic full w... more By employing the integral formulation of dielectric tensor, we have introduced the kinetic full wave analysis of ordinary-extraordinary-Bernstein (O-X-B) mode conversion in tokamak plasma in one dimension on the basis of TASK/W1 code using the finite element method. The boundary value problem of Maxwell's equation is solved and the finite Larmor radius effects are represented by integral formulation. The OX -B mode conversion and the absorption near the cyclotron harmonic resonance are successfully described.
Indian Journal of Physics, 2013
ABSTRACT By employing quantum hydrodynamic formulation, oblique propagation of electrostatic ion ... more ABSTRACT By employing quantum hydrodynamic formulation, oblique propagation of electrostatic ion waves and nonlinear structures are investigated in a magnetized dense Fermi plasma. Constituents are quantum (degenerate) electrons and non-degenerate mobile ions in presence of stationary massive ions (either positive or negative) in background. To reveal features of low frequency ion waves, where effects of Fermi degeneracy and quantum diffraction are significant, linear dispersion equation is derived by Fourier analysis of model equations. Nonlinear solitary pulse solution in low-amplitude limit is obtained via Korteweg de Vries equation. It is shown that wave dispersion due to electron Fermi pressure is important at very short wavelength regime. Effects of concentration of heavy ions and angle of propagation on wave are also studied. Results are discussed numerically with relevance of superdense plasmas mainly found in astrophysical regimes.
ABSTRACT Low frequency electrostatic and electromagnetic waves in a dense magnetoplasma are studi... more ABSTRACT Low frequency electrostatic and electromagnetic waves in a dense magnetoplasma are studied. The dispersive contribution of electron quantum effects in an electron-ion plasma in the presence of positively or negatively charged dust particles in the background is emphasized. By employing the quantum hydrodynamic model, a linear dispersion relation is derived which shows coupling of electrostatic and shear Alfven modes which shows influence of electron quantum effects and dust density.
Physics of Plasmas, 2009
The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized... more The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized dense electron-positron-ion plasma. For this purpose, the quantum hydrodynamic model is employed to derive a deformed Korteweg-de Vries (dKdV) equation. The steady state double layer solution of dKdV equation is obtained and its dependence on various parameters is discussed. It is found that only compressive double layers can exist in such plasmas. The analytical and numerical studies reveal that the quantum ion-acoustic double layer structures strongly depend on quantum diffraction effects and positron number density.
Acoustic Waves, 2010
Contrary to classical plasmas, the number density of degenerate electrons, positrons/holes in qua... more Contrary to classical plasmas, the number density of degenerate electrons, positrons/holes in quantum plasmas is extremely high and they obey Fermi-Dirac statistics whereas the temperature is very low. Plasma and quantum mechanical effects co-exist in such systems and many unusual effects like tunneling of electrons, quantum destabilization, pressure ionization, Bose-Einstein condensation and crystallization etc. may be equally important (Bonitz et al., 2009). Their properties in equilibrium and nonequilibrium are governed by many-body effects (collective and correlation effects) which require quantum statistical theories and versatile computational techniques. The average inter-particle distance n-1/3 (where n is the particle density) is comparable with electron thermal de Broglie wavelength
Indian Journal of Physics, 2014
In this study, a potentiometric urea biosensor has been fabricated on glass filter paper through ... more In this study, a potentiometric urea biosensor has been fabricated on glass filter paper through the immobilization of urease enzyme onto chitosan/cobalt oxide (CS/Co 3 O 4) nanocomposite. A copper wire with diameter of 500 lm is attached with nanoparticles to extract the voltage output signal. The shape and dimensions of Co 3 O 4 magnetic nanoparticles are investigated by scanning electron microscopy and the average diameter is approximately 80-100 nm. Structural quality of Co 3 O 4 nanoparticles is confirmed from X-ray powder diffraction measurements, while the Raman spectroscopy has been used to understand the chemical bonding between different atoms. The magnetic measurement has confirmed that Co 3 O 4 nanoparticles show ferromagnetic behavior, which could be attributed to the uncompensated surface spins and/or finite size effects. The ferromagnetic order of Co 3 O 4 nanoparticles is raised with increasing the decomposition temperature. A physical adsorption method is adopted to immobilize the surface of CS/Co 3 O 4 nanocomposite. Potentiometric sensitivity curve has been measured over the concentration range between 1 9 10-4 and 8 9 10-2 M of urea electrolyte solution revealing that the fabricated biosensor holds good sensing ability with a linear slope curve of *45 mV/ decade. In addition, the presented biosensor shows good reusability, selectivity, reproducibility and resistance against interferers along with the stable output response of *12 s.
Physics of Plasmas, 2014
ABSTRACT The kinetic theory of electron plasma waves with finite orbital angular momentum has rec... more ABSTRACT The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.
Springer Series on Atomic, Optical, and Plasma Physics, 2014
Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope ... more Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope of potential applications, ranging from nano-scale science in condensed matter to the vast scales of astrophysical objects. The theoretical description of quantum plasmas relies on various approaches, microscopic or macroscopic, some of which have obvious relation to classical plasma models. The appropriate model should, in principle, incorporate the quantum mechanical effects such as diffraction, spin statistics and correlations, operative on the relevant scales. However, first-principle approaches such as quantum Monte Carlo and density functional theory or quantum-statistical methods such as quantum kinetic theory or nonequilibrium Green's functions require substantial theoretical and computational efforts. Therefore, for selected problems, alternative simpler methods have been put forward. In particular, the collective behavior of many-body systems is usually described within a self-consistent scheme of particles and fields on the mean-field level. In classical plasmas, further simplifications are achieved by a transition to hydrodynamic equations. Similar fluid-type descriptions for quantum plasmas have been proposed and widely used in the recent decade. This chapter is devoted to an overview of the main concepts of quantum hydrodynamics (QHD), thereby critically analyzing its validity range and its main limitations. Furthermore, the results of the linearized QHD in unmagnetized and magnetized plasmas and a few nonlinear solutions are examined with illustrations. The basic concepts and formulation of particle-particle interactions are also reviewed at the end, indicating their possible consequences in quantum many-body problems.
Physics of Plasmas, 2010
The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron pla... more The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron plasmas in the presence of stationary ions. The quantum hydrodynamic model is employed and reductive perturbation method is used to derive the Korteweg-de Vries (KdV) and extended KdV equations for solitons and double layers, respectively. It is found that in the linear limit both slow acoustic and fast Langmuir waves can propagate in such type of quantum plasmas like in classical pair-ion or pair plasmas. The amplitude and width of the electrostatic solitons are found to be decreasing with the increase in concentration of positrons (or decrease in the concentration of ions) in degenerate electron-positron-ion plasmas. It is found that only rarefactive double layer can exist in such plasmas which depend on various parameters. The dependence of double layer structure on ion concentration and quantum diffraction effects of electrons and positrons are also discussed. The results are also elaborated graphically by considering dense plasma parameters in the outer layers of astrophysical objects such as white dwarfs and neutron stars.
Physics of Plasmas, 2008
... H. Ur-Rehman, SA Khan, W. Masood, M. Siddiq. ... A variety of modes have been discussed in du... more ... H. Ur-Rehman, SA Khan, W. Masood, M. Siddiq. ... A variety of modes have been discussed in dusty plasmas, such as dust ion acoustic (DIA) waves, dust acoustic (DA) waves, and dust lattice (DL) waves in unmagnetized dusty plasmas, whereas dust drift (DD) modes, Shukla ...
Physics of Plasmas, 2008
ABSTRACT Obliquely propagating linear and weakly nonlinear ion-acoustic waves in a magnetized qua... more ABSTRACT Obliquely propagating linear and weakly nonlinear ion-acoustic waves in a magnetized quantum plasma are investigated by employing the quantum hydrodynamic formulation. A linear dispersion relation is presented and the nonlinear Korteweg–de Vries equation is derived using the reductive perturbative method. The dispersion caused by the quantum diffraction effects is possible only in a very short wavelength regime. The amplitude and width of the solitons formed by the ion-acoustic waves propagating in a magnetized plasma depend upon various parameters. Possible applications of the results to dense plasmas are discussed.