Pakistan Atomic Energy Commission PAEC

Islamabad, Pakistan

Pakistan Atomic Energy Commission PAEC

Islamabad, Pakistan

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Arif A.,National Institute for Biotechnology and Genetic Engineering NIBGE | Zafar Y.,Pakistan Atomic Energy Commission PAEC | Arif M.,National Institute for Biotechnology and Genetic Engineering NIBGE | Blumwald E.,University of California at Davis
Molecular Biotechnology | Year: 2013

An increasing volume of evidence indicating the mechanisms of drought tolerance of AVP1-overexpressing transgenic plants has been reported. In the present study, we are reporting the experiments conducted for the drought tolerance of AVP1 overexpressing plants and WT tobacco plants in three water regimes named as "fully watered," "less-watered," and "desiccated". Results suggest that AVP1 plants exhibited greater vigor and drought tolerance in quantitative terms i.e., increase in size and weight of shoots and capsules. AVP1 plants produced more seeds than WT across all three water regimes. The less-watered regime was found to produce the greatest contrast. AVP1 overexpression enhanced solute accumulation in vacuoles resulting in an increase in water retention and turgor of the cell. The ultrastructure study of AVP1 overexpressing cells and WT leaf cells revealed that AVP1 plants displayed more turgid and hyperosmotic cells than WT. Moreover, guard cells in the AVP1 plants exhibited thick cell walls, few vacuoles, and deep and close stomata, whereas WT plants showed larger vacuoles and relatively open stomata aperture with no significant difference in size and number of the cells per unit area. © 2012 Springer Science+Business Media, LLC.

Nisar J.,Uppsala University | Nisar J.,Pakistan Atomic Energy Commission PAEC | Topalian Z.,Uppsala University | De Sarkar A.,KTH Royal Institute of Technology | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Fixation of SO2 molecules on anatase TiO2 surfaces with defects have been investigated by first-principles density functional theory (DFT) calculations and in situ Fourier transform infrared (FTIR) surface spectroscopy on porous TiO2 films. Intrinsic oxygen-vacancy defects, which are formed on TiO2(001) and TiO2(101) surfaces by ultraviolet (UV) light irradiation and at elevated temperatures, are found to be most effective in anchoring the SO2 gas molecules to the TiO 2 surfaces. Both TiO2(101) and TiO2(001) surfaces with oxygen vacancies are found to exhibit higher SO2 adsorption energies in the DFT calculations. The adsorption mechanism of SO 2 is explained on the basis of electronic structure, charge transfer between the molecule and the surface, and the oxidation state of the adsorbed molecule. The theoretical findings are corroborated by FTIR experiments. Moreover, the (001) surface with oxygen vacancies is found to bind SO 2 gas molecules more strongly, as compared to the (101) surface. Higher concentration of oxygen vacancies on the TiO2 surfaces is found to significantly increase the adsorption energy. The results shed new insight into the sensing properties of TiO2-based gas sensors. © 2013 American Chemical Society.

Wang B.,KTH Royal Institute of Technology | Kanhere P.D.,Nanyang Technological University | Chen Z.,Nanyang Technological University | Nisar J.,Pakistan Atomic Energy Commission PAEC | And 4 more authors.
Journal of Physical Chemistry C | Year: 2013

In this paper, we have employed DFT and HSE06 methods to study the doping effects on the NaTaO3 photocatalyst. N, S, C, and P monodoping and N-N, C-S, P-P, and N-P codoping have been studied. The redopants' formation energies have been calculated, and we find S monodoping is energetically more favorable than any other elemental doping. The mechanism of anion doping on the electronic properties of NaTaO3 is discussed. We find the band gap reduces significantly if we dope with anionic elements whose p orbital energy is higher than the O 2p orbitals. N and S can shift the valence band edge upward without losing the ability to split water into H2 and O2. Double-hole-mediated codoping can decrease the band gap significantly. On the basis of our calculations, codoping with N-N, C-S, and P-P could absorb visible light. However, they can only decompose water into H2 when the valence band edge is above the water oxidation level. © 2013 American Chemical Society.

Abbas Z.,Pakistan National Agricultural Research Center | Abbas Z.,National Institute for Genomics and Advanced Biotechnology NIGAB | Abbas Z.,National Institute for Biotechnology and Genetic Engineering NIBGE | Zafar Y.,Pakistan Atomic Energy Commission PAEC | And 2 more authors.
International Journal of Agriculture and Biology | Year: 2013

Insects have natural potential to develop resistance against chemical insecticides. Several resistance strategies have been suggested including biopesticides and use of two dissimilar toxins. Advances in molecular biology techniques have now allowed construction of chimeric proteins to delay the development of resistance in insect population, but still there are chances of developing resistance in insect population against them as these fusions are based on Bacillus thuringiensis (Bt) genes only, which have some homology in their amino acid sequences, having same mode of action and derived from same bacterial origin. In the present study ω-ACTX-Hv1a toxin gene (Hvt) as an insect calcium channel antagonist is fused with Bt cry1Ac to combine both strategies (biopesticides and two dissimilar toxins) and delay the resistance in insect population. The recombinant protein has been successfully expressed in prokaryotic system and was detected by SDS PAGE. Topical application of the 1.0 pmol purified recombinant protein to the thoracic region paralyzed and immobilized the Helicoverpa armigera and Spodoptera littoralis larvae within 2 h. 100% mortality was observed in insects after 24 h. The LD50 was found to be 4 and 2 pmol per gram of body weight for H. armigera and S. littoralis larvae, respectively. The present study clearly indicates that this recombinant protein is highly effective against agronomical important lepidopteron insects and is an excellent candidate for use as a biopesticides or expressed heterogeneously in agricultural crops to provide long lasting resistance to insect attacks. © 2013 Friends Science Publishers.

Pietzsch A.,Helmholtz Center Berlin | Nisar J.,Pakistan Atomic Energy Commission PAEC | Jamstorp E.,Paul Scherrer Institute | Grasjo J.,Uppsala University | And 3 more authors.
Journal of Electron Spectroscopy and Related Phenomena | Year: 2015

By combining X-ray absorption spectroscopy and first principles calculations we have determined the electronic structure of synthetic and natural kaolinite as a model system for engineered and natural clay materials. We have analyzed defect states in the band gap and find that both natural and synthetic kaolinite contain defects where oxygen replaces hydrogen in one of the Al (0 0 1)-hydroxyl groups of the kaolinite clay sheets. The band gap of both synthetic and natural kaolinite is found to decrease by about 3.2 eV as this defect is formed. © 2015 Elsevier B.V. All rights reserved.

Akhtar N.,Pakistan Institute of Nuclear Science and Technology | Akhtar N.,Pakistan Institute of Engineering and Applied Sciences | Mahmood S.,Pakistan Institute of Nuclear Science and Technology | Mahmood S.,Pakistan Institute of Engineering and Applied Sciences | And 2 more authors.
Plasma Physics and Controlled Fusion | Year: 2014

The modulational instability and envelope solitons of ion acoustic waves in an unmagnetized nonthermal electron-positron-ion (epi) plasma are investigated. The ions are taken to be dynamic and warm while electrons and positrons are assumed to be inertialess and hot which follow the kappa (or Generalized Lorentzian) distribution. The Krylov-Bogoliubov-Mitropolsky method is used to derive the nonlinear Schrödinger equation for nonlinear amplitude modulation of ion acoustic waves in nonthermal epi plasmas with warm ions. The dispersive and nonlinear coefficients are obtained for ion acoustic waves in nonthermal epi plasmas which depend on spectral indices of kappa distributed electrons and positrons, ion temperature and positron density. The modulationally stable and unstable regions are studied for a wide range of wave numbers and it is found that the finite ion temperature, positron density and spectral indices of kappa distributed electrons and positrons play a significant role in the formation of bright and dark envelope solitons in nonthermal epi plasmas with adiabatically heated ions. Our findings are applicable to explain some aspects of nonlinear propagation of envelope solitons in astrophysical plasma situations such as neutron stars or pulsars where nonthermal epi plasmas with warm ions can exist (Arons J 2009 Astrophys. Space Sci. Library 357 373, Blasi P and Amato E 2011 Astrophys. Space Sci. Proc. pp 623-41, Asif and Saeed 2011 Plasma Phys. Control. Fusion 53 095006). © 2014 IOP Publishing Ltd.

Mahmood S.,Pakistan Institute of Nuclear Science and Technology | Mahmood S.,Pakistan Institute of Engineering and Applied Sciences | Kanwal S.,Pakistan Institute of Engineering and Applied Sciences | Kanwal S.,Pakistan Atomic Energy Commission PAEC | And 2 more authors.
Physics of Plasmas | Year: 2012

Nonlinear electrostatic vortex structures in the rotating magnetized electron-positron-ion plasmas are investigated. The electrons and positrons are considered to be dynamic while ions are taken to be stationary to neutralize only plasma background. In linear limit, the dispersion relation for electrostatic wave in a rotating electron-positron-ion plasma is discussed for both local and nonlocal cases. It is also found that conditions for the existence of dipolar vortex structures are modified in the presence of stationary ions in a magnetized rotating electron-positron plasma. © 2012 American Institute of Physics.

Rafique J.,Harbin Institute of Technology | Rafique J.,Pakistan Atomic Energy Commission PAEC | Yu J.,Harbin Institute of Technology | Zha X.,Harbin Institute of Technology | Rafique K.,Pakistan Atomic Energy Commission PAEC
Bulletin of Materials Science | Year: 2010

Ultra thin and aligned carbon nanofibres (CNFs) have been fabricated by heat treatment from aligned polyacrylonitrile (PAN) nanofibre precursors prepared by electrospinning. The alignment of the precursor nanofibres was achieved by using a modified electrospinning set up developed recently, where a tip collector was used to collect and align the nanofibres. The average diameter of the aligned CNFs is about 80 nm. The stabilization and carbonization behaviour were studied mainly based on the randomly oriented PAN nanofibres. The effects of stabilization and carbonization temperatures, temperature-increasing rates, and with and without substrates on the morphology and structure of the CNFs were investigated. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Raman spectroscopy were used to characterize the structure of the CNFs and thermogravimetric/ differential temperature analysis was used to evaluate the thermal behaviour of PAN nanofibres. © Indian Academy of Sciences.

Sadiq S.,COMSATS Institute of Information Technology | Sadiq S.,Pakistan National Agricultural Research Center | Imran M.,COMSATS Institute of Information Technology | Hassan M.N.,COMSATS Institute of Information Technology | And 4 more authors.
LWT - Food Science and Technology | Year: 2014

Antimicrobial behavior of lactic acid bacteria (LAB) has been explored since many years to assess their ability to produce bacteriocin, a natural preservative, to increase the shelf life of food. This study aims to characterize bacteriocin producing strains of lactic acid bacteria isolated from acidic to slightly acidic raw vegetables including tomato, bell pepper and green chili and to investigate their potential to inhibit food related bacteria. Among twenty nine LAB screened for antimicrobial activity, three exhibited antagonism against closely related bacterial isolates which was influenced by varying temperature and pH. They were identified up to strain level as Lactococcus lactis subsp. lactis TI-4, L. lactis subsp. lactis CE-2 and L. lactis subsp. lactis PI-2 based on 16S rRNA gene sequence. Their spectrum of inhibition was observed against food associated strains of Bacillus subtilis and Staphylococcus aureus. Moreover, L. lactis subsp. lactis PI-2 selected on the basis of higher antimicrobial activity was further evaluated for bacteriocin production which was detected as nisin A and nisin Z. These findings suggest the possible use of L. lactis strains of vegetable origin as protective cultures in slightly acidic as well as slightly alkaline food by the bio-preservative action of bacteriocins. © 2014 Elsevier Ltd.

Zafar A.Y.,National Institute for Genomics and Advanced Biotechnology | Zafar A.Y.,Pakistan Atomic Energy Commission PAEC | Iqbal J.,National Institute for Genomics and Advanced Biotechnology | Iqbal M.M.,National Institute for Genomics and Advanced Biotechnology | And 4 more authors.
Molecular Biotechnology | Year: 2011

Salinity and drought are main threat to agriculture productivity, to avoid further losses it is necessary to improve the genetic material of crops against these stresses In this present study, AtNHX1, a vacuolar type Na +/H + antiporter gene driven by 35S promoter was introduced into groundnut using Agrobacterium tumefaciens transformation system. The stable integration of the AtNHX1 gene was confirmed by polymerase chain reaction (PCR) and southern blot analysis. It was found that transgenic plants having AtNHX1 gene are more resistant to high concentration of salt and water deprivation than the wild type plants. Salt and proline level in the leaves of the transgenic plants were also much higher than that of wild type plants. The results showed that overexpression of AtNHX1 gene not only improved salt tolerance but also drought tolerance in transgenic groundnut. Our results suggest that these plants could be cultivated in salt and drought-affected soils. © Springer Science+Business Media, LLC 2011.

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