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Controllable photo-induced spin and valley filtering in silicene
Yawar Mohammadi,Borhan Arghavani Nia
Physics , 2015,
Abstract: We study ballistic transport of Dirac electrons through a strip in silicene, when the strip is exposed to off-resonant circularly polarized light and an electric field applied perpendicular to the silicene plane. We show that the conductance through the strip is spin- or/and valley-polarized. This can be explained by spin-valley coupling in silicene, and modification of its band structure through virtual absorption/emission processes and also by the perpendicular electric field. The spin- (valley-) polarization can be enhanced by tuning the light intensity and the value of the perpendicular electric field, leading to perfect spin (valley) filtering for certain of their values. Further, the spin (valley) polarization can be inverted by reversing the perpendicular electric field (by reversing the perpendicular electric field or reversing the circular polarization of the light irradiation). The conditions necessary for the fully valley polarization is determined.
Electronic properties of armchair AA-stacked bilayer graphene nanoribbons
Yawar Mohammadi,Borhan Arghavani Nia
Physics , 2014,
Abstract: We study analytically, based on the tight-binding model, the electronic band structure of armchair AA-stacked bilayer graphene nanoribbons (BLGNRs) in several regimes. We apply hard-wall boundary conditions to determine the discretion dominating on the Bloch wavefunctions in the confined direction. First we consider an ideal case, perfect nanoribbons without any edge deformation, and show that their electronic properties are strongly size-dependent. We find that the narrow armchair AA-stacked BLGNRs (similar to single-layer graphene nanoribbons) may be metallic or semiconducting depending on their width determined by the number of dimer lines across the ribbon width, while the wide ribbons are metallic. Then we show that, when the edge deformation effects are taken into account, all narrow armchair AA-stacked BLGNRs become semiconducting while the wide ribbons remain metallic. We also investigate effects of an electric filed applied perpendicular to the nanoribbon layers and show it can be used to tune the electronic properties of these nanoribbons leading to a semiconducting-to-metallic phase transition at a critical value of the electric field which depends on the nanoribbon width. Furthermore, in all regimes, we calculate the corresponding wavefunctions which can be used to investigate and predict various properties in these nanoribbons.
Controllable intrinsic DC spin/valley Hall conductivity in ferromagnetic silicene: Exploring a fully spin/valley polarized transport
Yawar Mohammadi,Borhan Arghavani Nia
Physics , 2015, DOI: 10.1016/j.spmi.2015.10.006
Abstract: We study intrinsic DC spin and valley Hall conductivity in doped ferromagnetic silicene in the presence of an electric filed applied perpendicular to silicene sheet. By calculating its energy spectrum and wavefunction and by making use of Kubo formalism, we obtain a general relation for the transverse Hall conductivity which can be used to obtain spin- and valley-Hall conductivity. Our results, in the zero limit of the exchange field, reduces to the previous results. Furthermore we discuss electrically tunable spin and valley polarized transport in ferromagnetic silicene and obtain the necessary conditions for observing a fully spin or valley polarized transport.
Strain engineering the charged-impurity-limited carrier mobility in phosphorene
Yawar Mohammadi,Borhan Arghavani Nia
Physics , 2015, DOI: 10.1016/j.spmi.2015.10.049
Abstract: We investigate, based on the tight-binding model and in the linear deformation regime, the strain dependence of the electronic band structure of phosphorene, exposed to a uniaxial strain in one of its principle directions, the normal, the armchair and the zigzag directions. We show that the electronic band structure of strained phosphorene, for experimentally accessible carrier densities and uniaxial strains, is well described by a strain-dependent decoupled electron-hole Hamiltonian. Then, employing the decoupled Hamiltonian, we consider the strain dependence of the charged-impurity-limited carrier mobility in phosphorene, for both types of carrier, arbitrary carrier density and in both armchair and zigzag directions. We show that a uniaxial tensile (compressive) strain in the normal direction enhances (weakens) the anisotropy of the carrier mobility, while a uniaxial strain in the zigzag direction acts inversely. Moreover applying a uniaxial strain in the armchair direction is shown to be ineffective on the anisotropy of the carrier mobility. These will be explained based on the effect of the strain on the carrier effective mass.
Using Two Widespread Backbones to Increase the Lifetime of Wireless Sensor Networks
Ensiye Ahmadi,Abbas Arghavani
International Journal of Mechatronics, Electrical and Computer Technology , 2013,
Abstract: Limiting energy resource in the sensor networks increases the importance of energy aware protocols. Nonexistence of fixed or predefined infrastructure in the sensor networks compared to radio and case networks, add the necessity of existence such protocols. In this paper, two energy aware rooted virtual backbone have used for collecting and transferring data toward the sink. Each backbone is built such that covers the large numbers of network nodes, so that any node is not a member of both backbones. Simulation results show that alternative usage of two mentioned backbones, have significant influence on the increasing network lifetime. In addition, we would show that suggested guideline, against existing methods, has not significant effectiveness of changing the size of controlled packet.
Agent Petri Nets Framework for Modeling Staphylococcus epidermidis Biofilm Formation  [PDF]
Borhan Marzougui, Kamel Barkaoui, Mohamed Amine Makni
E-Health Telecommunication Systems and Networks (ETSN) , 2016, DOI: 10.4236/etsn.2016.51003
Abstract: This Staphylococcus epidermidis has been discovered as the most frequent germ detected during indwelling medical devices infection. This fact is well attached with the ability of this bacterium to form structured layered population known as biofilm. Inside S. epidermidis biofilm, bacterial cells present more different behavior than in their planktonic counterpart. This paper describes the thriving application of Petri net theory for modeling of interaction between different regulations actors leading S. epidermidis to switch from Planctonik to Biofilm. Indeed this biologic system is very sensible and has dangerous effect. We propose Agent Petri Nets model to describe and analyze the process of formation of Biofilm molecule. This model presents a formal framework based on Multi Agents system characteristics.
Genotyping of E. coli Isolated from Urinary Tract Infection Patients Containing B-Lactamase Resistance Gene CTX-M Group 1 in Sanandaj Medical Health Centers  [PDF]
Arezoo Omati, Kambiz Davari, Borhan Shokrolahi
American Journal of Molecular Biology (AJMB) , 2016, DOI: 10.4236/ajmb.2016.64015
Abstract: CTX-M-producing bacteria are known as a resistant source against oxyimino-cephalosporin such as cefotaxime and ceftazidime; although laboratory diagnosis of this gene has not been properly defined. The aims of this study are determining the rates of prevalence of CTX-M and CTX-M group 1 in the Escherichia coli (E. coli) obtained from urinary tract infections (UTI), and also determining their genetic relationship in the city of Sanandaj. In current study, 180 E. coli strains isolated from urinary tract infections were used. Sensitivity to common antibiotics was studied by the disc diffusion method. Phenotypic detection of isolated ESBL-producing starins was done by the combination disc test. CTX-M and CTX-M1 genes were detected using the PCR method and finally, the possible clonal relationship between isolates was determined using the REP-PCR method. 89 samples were ESBL-positive. The PCR assay used for detecting the CTX-M gene, showed that 48 samples out of 180 samples (26.66%) contained that gene; also among these 48 samples, 23 (12.77%) had CTX-M group 1. Based on the REP-PCR assay, 48 genotypes among 48 samples were CTX-M-positive. Results from the REP-PCR assay indicated that the clonal propagation theory of one epidemic strain of Escherichia coli is not apply, i.e. all CTX-M-producing species are not originated from one single strain and the gene is spread between different isolates. Therefore, hospitals and their employees must be more hygiene and, proper disposal of hospital waste can help to prevent the spread of different resistances.
Evaluation of Kostiakov’s Infiltration Equation in Furrow Irrigation Design According to FAO Method
Borhan Sohrabi,Abdolkarim Behnia
Journal of Agronomy , 2007,
Abstract: According to recommendations by FAO, the estimation of furrow length without any design computations requires the application of the so-called Tn/4 law in order to reduce depth water losses. In other cases where the coefficients in the infiltration equation are known from field measurements and data, other relations may be used on the basis of these coefficients and for given depth water losses. The research was conducted by Agricultural Engineering Institute of Iran through 1992-1997 at four province of Iran. In the investigations carried out in the Sugar Beet Research Station (Karaj) furrow irrigation was used with cut-back. Field analyses revealed differences in the range of 27-38% between the computed parameters in the design stage and farm measurements. The FAO’s method was also evaluated at other station in Karaj (Deputy of Infrastructure). In this region, the field measurements and model predictions for infiltration values showed a difference of 1-14%. Evaluation of the FAO model was also performed at Tajrak Agricultural Research Station in Hamedan using the furrow irrigation (without cut-back). The differences in values found at this site were 43-64%. The same differences for Boroujerd Agricultural Research Station were 19-31%. It is easily seen from these observations that theoretical relations, even those proposed by recognized international organizations such as FAO and SCS, cannot establish valid and reliable foundations for designing surface irrigation systems but that at least in large projects, field investigations are required prior to design and evaluation of these systems in order to avoid further water losses.
A comparative survey on the increased fracture resistance of amalgam restored teeth using three types of Glass Ionomer as adhesive liners
Shafiee F.,Borhan Haghighi Z
Journal of Dental Medicine , 2004,
Abstract: Statement of Problem: Because dental amalgam does not adhere to tooth structure, using adhesive cements in amalgam-bonded restorations have been increased. Purpose: The goal of this in-vitro study was to compare the effects of three types of glass ionomer as adhesive liners as well as varnish liner in increasing fracture resistance of teeth restored with amalgam. Materials and Methods: Seventy extracted human maxillary premolars were selected and MOD cavities were prepared on them excluding ten intact teeth as positive control group and ten cavity prepared teeth without restoration as negative control group. All the prepared teeth were then restored with spherical amalgam (gs.80) with one of the following liners silver alloy glass ionomer liner, conventional glass ionomer liner, varnish liner, resin-modified glass ionomer and resin-modified glass ionomer with delayed light curing. The teeth were stored in 37 C distilled water for 7 days and were then loaded under compressive strength using an Instron testing machine. The force required to fracture teeth were recorded and the data were analyzed statistically using ANOVA and Tukey HSD tests. Results: Statistically significant differences were observed in fracture resistance between restored and non-restored samples. Comparisons between groups attributed significant effects to resin-modified glass ionomer in increasing fracture resistance of amalgam restored teeth (P<0.05). In most specimens, one cusp was separated from tooth structure whereas amalgam remained bonded to the intact cusp. Conclusion: According to these findings, resin-modified glass ionomer put a statistically significant effect in fracture resistance of amalgam-restored teeth.
Preparation and Characterization of Activated Carbon from Rubber-seed Shell by Chemical Activation
Azry Borhan,Ahmad Fikree Kamil
Journal of Applied Sciences , 2012,
Abstract: The use of rubber-seed shell, an agricultural waste by-product as a raw material for the production of activated carbon with chemical activation using potassium hydroxide, KOH was investigated. In this work, the produced activated carbons were characterized by Nitrogen Adsorption Theorem and Scanning Electron Microscope instruments. The optimal activation conditions were found at temperature of 500°C and at activation time of 180 min. Result showed that the BET surface area, total pore volume and diameter of the activated carbon were 1288.52 m2 g-1, 0.81 cm3 g-1 and 2.49 nm, respectively. From the nitrogen adsorption-desorption isotherm and pore size distribution, it was found that vast majority of pores fall within range of mesopore, therefore indicating that activated carbon prepared from rubber-seed shell is an attractive source for liquid and gas adsorption applications.
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