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Islamabad, Pakistan

Masood W.,Pakistan Institute of Nuclear Science and Technology | Masood W.,National Center for Physics | Eliasson B.,Ruhr University Bochum | Eliasson B.,Umea University
Physics of Plasmas | Year: 2011

A model for nonlinear ion waves in an unmagnetized plasma with relativistically degenerate electrons and cold fluid ions is presented here. The inertia is given here by the ion mass while the restoring force is provided by the relativistic electron degeneracy pressure, and the dispersion is due to the deviation from charge neutrality. A nonlinear Korteweg-de Vries equation is derived for small but finite amplitude waves and is used to study the properties of localized ion acoustic solitons for parameters relevant for dense astrophysical objects such as white dwarf stars. Different degrees of relativistic electron degeneracy are discussed and compared. © 2011 American Institute of Physics.


Kausar A.,Quaid-i-Azam University | Kausar A.,National Center for Physics | Zulfiqar S.,National University of Sciences and Technology | Sarwar M.I.,Quaid-i-Azam University
Polymer Reviews | Year: 2014

Currently, a lot of research efforts have been directed toward exploiting the special high-performance characteristics of polymers with sulfur in the backbone. Sulfur-containing polymers fall under various classes and cover an extremely broad property range. The impetus to their development resulted from the unique properties and success in their applications, depending upon the type of linkage introduced. This review basically sets out to explain the design, synthesis, properties, and applications of various sulfur-containing polymers especially polyamides, polyimides, poly(amide-imide)s, polybenzimidazoles, polyurethanes, polyesters, etc. Outstanding performance of these polymers came up from their structures having sulfur-based groups such as thiophene, sulfide, sulfone, thiazol, and thiourea. Thus these linkages endow special features to such functional polymers. The sulfur-containing polymers are also described here with reference to their relevance as optically active, liquid crystalline, flame retardant, and fuel cell materials. Several endeavors are underway to take advantage of incorporated sulfur moiety in the polymer backbone, as a consequence to ascertain their validity on the forefront of scientific investigations. © 2014 Copyright Taylor & Francis Group, LLC.


Motapothula M.,National University of Singapore | Dang Z.Y.,National University of Singapore | Venkatesan T.,National University of Singapore | Breese M.B.H.,National University of Singapore | And 2 more authors.
Physical Review Letters | Year: 2012

We report channeling patterns where clearly resolved effects of the narrow {111} planes are observed in axial and planar alignments for 2Â MeV protons passing through a 55Â nm [001] silicon membrane. At certain axes, such as â?̈213â?© and â?̈314â?©, the offset in atomic rows forming the narrow {111} planes results in shielding from the large potential at the wide {111} planes, producing a region of shallow, asymmetric potential from which axial channeling patterns have no plane of symmetry. At small tilts from such axes, different behavior is observed from the wide and narrow {111} planes. At planar alignment, distinctive channeling effects due to the narrow planes are observed. As a consequence of the shallow potential well at the narrow planes, incident protons suffer dechanneled trajectories which are excluded from channeling within the wide planes, resulting in an anomalously large scattered beam at {111} alignment. © 2012 American Physical Society.


Saeed A.,International Islamic University, Islamabad | Alia N.,National Center for Physics | Syed W.A.,International Islamic University, Islamabad
Chalcogenide Letters | Year: 2013

Tin antimony sulfide (SnSb2S4) thin film was deposited on ultrasonically cleaned soda lime glass substrate by vacuum thermal evaporation technique at10-4 Torr chamber pressure. The deposited thin films were annealed at 150°C in tube furnace in the presence of argon gas. For characterization, thin films were subjected to X-ray diffraction (XRD), SEM, EDS and J.A. Woollam variable angle ellipsometry (VASE) for structural, surface morphological, elemental composition and optical properties respectively. The film has ntype conductivity, confirmed by hot point probe technique. The film has good optical, structural and electrical properties extremely suitable for the use as non-toxic, environmental friendly absorbing layer in solar cell.


Gohar H.,National Center for Physics | Saifullah K.,Quaid-i-Azam University
General Relativity and Gravitation | Year: 2012

We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well. © 2012 Springer Science+Business Media, LLC.

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