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- Ahmad, Sheikh Asrar, et al.
(författare)
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Use of digital thruster to separate the cadmium and lead metals from mixture sample
- 2008
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 63:1, s. 101-106
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Tidskriftsartikel (refereegranskat)abstract
- The present work deals with the use of a digital thruster (DT) for the separation of cadmium and lead metals from mixture samples. Mixtures of lead and cadmium salts with varying concentrations were injected into a free electrolytic diffusion apparatus (FEDA). The microcathodes surrounding the central anode were programmed witha DT. The DT distributed the charge over the microcathodes at time intervals of 100-900 mu s or at the frequency of 625-70 Hz. The microcathodes become electrodeposited with lead and cadmium metals, showing both separation and co-deposition. The purity of deposited metals was analyzed by Atomic Absorption Spectroscopy (AAS) using PerkinElmer and Aldrich AAS standards. (C) 2008 Elsevier B.V. All rights reserved.
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| 5. |
- Ali, Shahid, 1975-
(författare)
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Waves and instabilities in quantum plasmas
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study of waves and instabilities in quantum plasmas is of fundamental importance for understanding collective interactions in superdense astrophysical objects, in high intense laser-plasma/solid-matter interactions, in microelectronic devices and metallic nanostructures. In dense quantum plasmas, there are new pressure laws associated with the Fermi-Dirac distribution functions and new quantum forces associated with the quantum Bohm potential and the Bohr magnetization involving electron ½ spin. These forces significantly alter the collective behavior of dense quantum plasmas. This thesis contains six papers, considering several novel collective modes and instabilities at quantum scales. In Paper I, we have used the quantum hydrodynamical (QHD) model for studying the one-dimensional dust-acoustic (DA) waves incorporating the Fermi pressure law and the quantum Bohm potential. The latter modifies the DA wave dispersion relation in a collisional plasma. In Paper II, we have calculated the electrostatic potential of a test charge in an unmagnetized electron-ion quantum plasma. It is found that the Debye-Hückel and oscillatory wake potentials strongly depend upon the Fermi energy at quantum scales. The results can be of interest for explaining the charged particle attraction and repulsion in degenerate quantum plasmas, such as those in semiconductor and microelectronic devices. Paper III presents the parametric study of nonlinear electrostatic waves in two-dimensional collisionless quantum dusty plasmas. A reductive perturbation method has been employed to the QHD equations together with the Poisson equation, obtaining the cylindrical Kadomtsev-Petviashvili (CKP) equations and their stationary localized solutions. We have numerically examined the quantum mechanical and geometrical effects on the profiles of nonplanar quantum dust-ion-acoustic (DIA) and DA solitary waves. The role of static as well as mobile (negatively or positively charged) dust particles on the low-frequency electrostatic waves has also been highlighted for metallic nanostructures. Paper IV introduces the nonlinear properties of the ion-sound waves in a dense electron-ion Fermi magnetoplasma. The computational analysis of the nonlinear system reveals that the Sagdeev-like potential and the ion-sound density excitations are significantly affected by the wave direction cosine and the Mach number at quantum scales. Paper V considers the nonlinear interactions of electrostatic upper-hybrid (UH), ion-cyclotron (IC), lower-hybrid (LH), and Alfvén waves in a quantum magnetoplasma. The nonlinear dispersion relations have been analyzed analytically to obtain the growth rates for both the decay and modulational instabilities involving the dispersive IC, LH, and Alfvén waves. In Paper VI, we have identified a new drift-like dissipative instability in a collisional quantum plasma. The modified unstable drift-like mode can cause cross-field anomalous ion-diffusion at quantum scales.
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| 6. |
- Moslem, Waleed M., et al.
(författare)
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Three-dimensional electrostatic waves in a nonuniform quantum electron–positron magnetoplasma
- 2008
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 372:19, s. 3471-3475
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Tidskriftsartikel (refereegranskat)abstract
- The dispersion properties of three-dimensional electrostatic waves in a nonuniform quantum electron–positron magnetoplasma are examined. A new dispersion relation is derived using the electron and positron densities response arising from the balance between the quantum Bohm and electrostatic forces, and from the electron and positron continuity and Poisson equations. In the local approximation regime, the dispersion relation admits both oscillatory and purely growing instabilities those depend on the quantum parameters as well as the density, velocity and magnetic field inhomogeneities.
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| 7. |
- Rasool, Mahmood, et al.
(författare)
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A novel missense mutation in the EDA gene associated with X-linked recessive isolated hypodontia
- 2008
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Ingår i: Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1434-5161 .- 1435-232X. ; 53:10, s. 894-8
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Tidskriftsartikel (refereegranskat)abstract
- Isolated hypodontia, or congenital absence of one to six permanent teeth (OMIM 300606), is a common condition that affects about 20% of individuals worldwide. We identified two extended Pakistani pedigrees segregating X-linked hypodontia with variable expressivity. Affected males show no other associated anomalies, and obligate carrier females have normal dentition. We analyzed the families with polymorphic markers in the ectodysplasin A (EDA) gene region and obtained significant linkage to the phenotype in each pedigree (Z(max) 3.29 and 2.65, respectively, at theta = 0.00). Sequence analysis of the coding regions of EDA revealed a novel missense mutation c.1091T>C resulting in a methionine to threonine substitution (p.M364T) in the tumor necrosis factor (TNF) homology domain. Met364 is a highly conserved residue located on the outer surface of the EDA protein. From our findings, we suggest that the mutation disturbs but does not destroy the EDA structure, resulting in the partial and unusually mild ED phenotype restricted to hypodontia.
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