Papers by Muataz Al Barwani
Sheridan Center for Teaching and Learning, Brown University, 1995
Cayley-Dickson doubling procedure is used to construct the root systems of some celebrated Lie al... more Cayley-Dickson doubling procedure is used to construct the root systems of some celebrated Lie algebras in terms of the integer elements of the division algebras of real numbers, complex numbers, quaternions and octonions. Starting with the roots and weights of SU(2) expressed as the real numbers one can construct the root systems of the Lie algebras of SO(4),SP(2)= SO(5),SO(8),SO(9),F_4 and E_8 in terms of the discrete elements of the division algebras. The roots themselves display the group structures besides the octonionic roots of E_8 which form a closed octonion algebra. The automorphism group Aut(F_4) of the Dynkin diagram of F_4 of order 2304, the largest crystallographic group in 4-dimensional Euclidean space, is realized as the direct product of two binary octahedral group of quaternions preserving the quaternionic root system of F_4.The Weyl groups of many Lie algebras, such as, G_2,SO(7),SO(8),SO(9),SU(3)XSU(3) and SP(3)X SU(2) have been constructed as the subgroups of Au...
The largest finite subgroup of O(4) is the noncrystallographic Coxeter group W(H_4) of order 1440... more The largest finite subgroup of O(4) is the noncrystallographic Coxeter group W(H_4) of order 14400. Its derived subgroup is the largest finite subgroup W(H_4)/Z_2 of SO(4) of order 7200. Moreover, up to conjugacy, it has five non-normal maximal subgroups of orders 144, two 240, 400 and 576. Two groups [ W(H_2)× W(H_2)] × Z_4 and W(H_3)× Z_2 possess noncrystallographic structures with orders 400 and 240 respectively. The groups of orders 144, 240 and 576 are the extensions of the Weyl groups of the root systems of SU(3)× SU(3) maximal subgroups of quaternionic root systems.
Software stack in modern science is comparable to any other kind of experimental apparatus it mus... more Software stack in modern science is comparable to any other kind of experimental apparatus it must be checked and validated to assure its correctness Scientific software publications are subject to neither QA nor peer review Scientists typically develop their own software spending typically 30% of their time 90% or more of them are self-taught, lacking the knowledge of software development practices Ensuring that correct and reproducible results are published is a matter of scientific integrity
Software stack in modern science is comparable to any other kind of experimental apparatus it mus... more Software stack in modern science is comparable to any other kind of experimental apparatus it must be checked and validated to assure its correctness Scientific software publications are subject to neither QA nor peer review Scientists typically develop their own software spending typically 30% of their time 90% or more of them are self-taught, lacking the knowledge of software development practices Ensuring that correct and reproducible results are published is a matter of scientific integrity
Hyperfine Interactions, 2016
The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential... more The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential linear-augmented-plane-waves method. We have calculated the Fermi contact field (B hf) and isomer shift (δ) at the Fe site versus the number of neighbouring Ga atoms. We found that B hf decrease whereas δ increases with increasing number of neighbouring G atom. In addition we have calculated the hyperfine properties of FeGa system with DO 3 structure, where various distributions of 4 the Ga atoms in the conventional unit cell are considered (including the regular DO 3 structure). We found that the DO 3 structure has the lowest energy as compared to the other configurations. The two distinct A and D sites of the ordered DO 3 conventional unit cell have two distinct values for B hf and δ. On changing the atomic arrangement of the Ga atoms within the conventional unit cell, the configuration of the A site is maintained whereas that of the D site becomes imperfect. The contact magnetic hyperfine fields of the D-like sites in the imperfect structures are lower than that of the DO 3 D site.
PLoS ONE, 2013
We use a simulation technique based on molecular dynamics and stochastic rotation model to presen... more We use a simulation technique based on molecular dynamics and stochastic rotation model to present the effect of temperature and capsid tail on the packaging and ejection processes of semiflexible polymers. We consider two types of solvents, a good solvent, where the polymer is neutral and repulsion interactions among its various sections are favored, and one where the polymer is charged, giving rise to extra electrostatic reaction. For tailless capsids, we find that packing a neutral polymer is slightly slower at higher temperatures whereas its ejection is slightly slower at lower temperatures. We find the same trend for a charged polymer but the effect is noticeably larger. At a high enough temperature, we notice that packing a charged polymer can be stopped. On the other hand, at fixed temperature and regardless whether the polymer is charged, packing is much easier for a capsid with a tail whereas ejection is much slower. The effect of including the tail on the dynamics of a charged polymer, in particular, is rather significant: more packing fraction is facilitated at higher temperatures due to more ordered polymer configuration inside the capsid. In contrast, during ejection the tail traps the last remaining beads for quite some time before allowing full ejection. We interpret these results in terms of entropic and electrostatic forces.
Nanoscale Research Letters, 2012
Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar + ions at different en... more Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar + ions at different energies were investigated using X-ray photoemission spectroscopy (XPS) and atomic force microscopy techniques. The results provide direct experimental evidence of ripple formation, sp 2 to sp 3 hybridized carbon transformation, electronic damage, Ar + implantation, unusual defects and edge reconstructions in FLG, which depend on the irradiation energy. In addition, shadowing effects similar to those found in oblique-angle growth of thin films were seen. Reliable quantification of the transition from the sp 2-bonding to sp 3-hybridized state as a result of Ar + ion irradiation is achieved from the deconvolution of the XPS C (1s) peak. Although the ion irradiation effect is demonstrated through the shape of the derivative of the Auger transition C KVV spectra, we show that the D parameter values obtained from these spectra which are normally used in the literature fail to account for the sp 2 to sp 3 hybridization transition. In contrast to what is known, it is revealed that using ion irradiation at large FLG sample tilt angles can lead to edge reconstructions. Furthermore, FLG irradiation by low energy of 0.25 keV can be a plausible way of peeling graphene layers without the need of Joule heating reported previously.
Modern Physics Letters B, 2011
The electronic and magnetic structures of a hydrogenated and hydrogen free superlattice of three ... more The electronic and magnetic structures of a hydrogenated and hydrogen free superlattice of three iron monolayers and nine vanadium monolayers are studied using the first principle full-potential augmented-plane-wave method as implemented in WIEN2k package. The average and the local magnetic moments of the system are studied versus the hydrogen positions at the octahedral sites within the superlattice and also versus the filling of the vanadium octahedral location by hydrogen atoms. The local Fe magnetic moment and the average magnetic moment per iron atom are found to increase as the H position moves towards the Fe – V interface. On the other hand, the average magnetic moment per Fe atom is found to initially decrease up to filling by three H atoms and then increases afterwards. To our knowledge, this is the first reporting on the increase in the computed magnetic moment with hydrogenation. These trends of magnetic moments are attributed to the volume changes resulting from hydrogen...
Macromolecules, 1998
<F4.381e+05&am... more <F4.381e+05>Molecular dynamics simulations of a model main-chain liquid-crystallinepolymer (LCP), and a low molecular weight analogue, have been carriedout using an e#cient parallel algorithm. A main-chain LCP is formed withthe help of Gay-Berne mesogenic units connected to each other throughflexible methylene spacers. We have studied the e#ect of varying thespacer length, and have examined the region of the isotropic - liquidcrystalline
Linear Algebra and its Applications, 2006
The largest finite subgroup of O(4) is the noncrystallographic Coxeter group W (H4) of order 1440... more The largest finite subgroup of O(4) is the noncrystallographic Coxeter group W (H4) of order 14400. Its derived subgroup is the largest finite subgroup W (H4)/Z2 of SO(4) of order 7200. Moreover, up to conjugacy, it has five non-normal maximal subgroups of orders 144, two 240, 400 and 576. Two groups [W (H2) × W (H2)]×Z4 and W (H3)×Z2 possess noncrystallographic structures with orders 400 and 240 respectively. The groups of orders 144, 240 and 576 are the extensions of the Weyl groups of the root systems of SU (3) × SU (3), SU (5) and SO(8) respectively. We represent the maximal subgroups of W (H4) with sets of quaternion pairs acting on the quaternionic root systems.
Journal of Physics A: Mathematical and General, 1997
A gauged SO(3) symmetry is broken into its closed subgroups by Higgs scalars belonging to the irr... more A gauged SO(3) symmetry is broken into its closed subgroups by Higgs scalars belonging to the irreducible representations characterized by j = 2, 3, 4 and 6. Explicit matrix decompositions of the irreducible representations of SO(3) in terms of the irreducible representations of the closed subgroups are made manifest. Analogous structures between the line defects of liquid crystals and the cosmic strings are notified.
Journal of Mathematical Physics, 2003
ABSTRACT The root systems of SO(8), SO(9) and F4 are constructed by quaternions. Triality manifes... more ABSTRACT The root systems of SO(8), SO(9) and F4 are constructed by quaternions. Triality manifests itself as permutations of pure quaternion units e1, e2 and e3. It is shown that the automorphism groups of the associated root systems are the finite subgroups of O(4) generated by left-right actions of unit quaternions on the root systems. The relevant finite groups of quaternions, the binary tetrahedral and binary octahedral groups, play essential roles in the construction of the Weyl groups and their conjugacy classes. The relations between the Dynkin indices, standard orthogonal vector and the quaternionic weights are obtained.
![Research paper thumbnail of Quaternionic root systems and subgroups of the Aut(F[sub 4])](https://attachments.academia-assets.com/83555242/thumbnails/1.jpg)
Journal of Mathematical Physics, 2006
Cayley-Dickson doubling procedure is used to construct the root systems of some celebrated Lie al... more Cayley-Dickson doubling procedure is used to construct the root systems of some celebrated Lie algebras in terms of the integer elements of the division algebras of real numbers, complex numbers, quaternions and octonions. Starting with the roots and weights of SU (2) expressed as the real numbers one can construct the root systems of the Lie algebras of SO(4), SP (2) ≈ SO(5), SO(8), SO(9), F4 and E8 in terms of the discrete elements of the division algebras. The roots themselves display the group structures besides the octonionic roots of E8 which form a closed octonion algebra. The automorphism group Aut(F4) of the Dynkin diagram of F4 of order 2304, the largest crystallographic group in 4-dimensional Euclidean space, is realized as the direct product of two binary octahedral group of quaternions preserving the quaternionic root system of F4 .The Weyl groups of many Lie algebras, such as, G2, SO(7), SO(8), SO(9), SU (3)XSU (3) and SP (3) × SU (2) have been constructed as the subgroups of Aut(F4) .We have also classified the other non-parabolic subgroups of Aut(F4) which are not Weyl groups. Two subgroups of orders192 with different conjugacy classes occur as maximal subgroups in the finite subgroups of the Lie group G2 of orders 12096 and 1344 and proves to be useful in their constructions. The triality of SO(8) manifesting itself as the cyclic symmetry of the quaternionic imaginary units e1, e2, e3 is used to show that SO(7) and SO(9) can be embedded triply symmetric way in SO(8) and F4 respectively.
Hyperfine Interactions, 2011
We study the effect of hydrogen on the electronic, magnetic and hyperfine structures of an ironva... more We study the effect of hydrogen on the electronic, magnetic and hyperfine structures of an ironvanadium superlattice consisting of three Fe monolayers and nine V monolayers. The contact charge density (ρ), the contact hyperfine field (Bhf) and the electronic field gradient (EFG) at the Fe sites for different H locations and H fillings are calculated using the first principle full-potential linear-augmented-plane-wave (FP-LAPW) method . It is found that sizeable changes in the hyperfine properties are obtained only when H is in the interface region.
Journal of Physics and Chemistry of Solids, 2018
The Open University's repository of research publications and other research outputs Atomistic an... more The Open University's repository of research publications and other research outputs Atomistic and ab initio DFT modelling of the defect structures in Al 3+ /Cr 3+-doped and co-doped Y 3 Fe 5 O 12
We present simulations investigating the role of the tail of a spherical viral capsid (mimicking ... more We present simulations investigating the role of the tail of a spherical viral capsid (mimicking a bacteriophage) on the ejection dynamics of a semiflexible polymer (representing viral dsDNA). We compare the ejection dynamics of a neutral polymer with that of a charged one. We find that the presence of the tail markedly slows down ejection. Our simulations suggest that this is because the last few polymer sections are trapped in the tail. Such trapping is particularly efficient for a charged polymer where the entropy of the part of the polymer outside the capsid is greatly reduced making complete ejection of the last few polymer sections difficult. Lowering the temperature further enhances this trapping.
Physical Review E, 2000
The isotropic-nematic interface of a simple model of liquid-crystal molecules has been investigat... more The isotropic-nematic interface of a simple model of liquid-crystal molecules has been investigated using computer simulation, and by numerical minimization of the Onsager free-energy functional. The molecules are represented by long spherocylindrical particles interacting via the Kihara potential. The agreement between simulation and theory is excellent, apart from the bulk coexistence densities which are over estimated by the theory. Planar alignment of the molecules at the interface is preferred in all cases. The number density profile is found to vary monotonically, both in simulation and in theory. Biaxiality of the molecular orientational distribution near the interface is demonstrated.
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Papers by Muataz Al Barwani