Hakim Sabzevari University

Sabzevar, Iran
Time filter
Source Type

A simple electrochemical sensor has been developed based on the reduced graphene oxide/Pt nanoparticles nanocomposite immobilized on modified glassy carbon electrode (nPt-GN/GCE). The modified electrode displayed excellent electrochemical catalytic activities toward droxidopa (DDP) and phenobarbital (PB). The analytical performance of prepared electrode for the simultaneous determination of DDP and PB was investigated by using cyclic voltammetry and differential pulse voltammetry (DPV). The nPt-GN based sensor could separate the oxidation peak potentials of DDP and PB about 230 mV by DPV method. The calculated detection limits, obtained by DPV, for DDP and PB were 3.1 × 10−8 M and 2.36 × 10−8 M, respectively. The fabricated sensor was successfully applied to the detection of DDP and PB in real samples. The experiments illustrate that nPt-GN nanocomposite is a worthy electrode material which offers a large surface-to-volume ratio and improves the selectivity and sensitivity. © 2016 Elsevier B.V.

Lezgy-Nazargah M.,Hakim Sabzevari University
Thin-Walled Structures | Year: 2017

Based on a generalized layered global-local beam (GLGB) theory, a computationally low cost finite element model is presented for the elasto-plastic analysis of thin-walled beams. In the employed GLGB theory, the cross-section of the thin-walled beam is replaced with an equivalent layered composite one. For describing the displacement fields of the equivalent layered composite beam, the double superposition hypothesis in conjugate with an exponential shear stress function is employed. In contrast to the most of available advanced one-dimensional (1D) models proposed for thin-walled structures, the effects of the transverse normal stress and transverse flexibility are considered in the present GLGB theory. The proposed GLGB theory does not need the incorporation of any shear correction factor and it has only one general unknown parameter more than Timoshenko's beam theory. For plasticity modeling, von Mises yield criterion is employed. The non-linear 1D finite element formulations are solved using Newton-Raphson algorithm. The proposed nonlinear finite element model is validated through comparison with the three-dimensional (3D) finite element and other similar theoretical models available in the literature. © 2017 Elsevier Ltd

Mahdavian Yekta D.,Hakim Sabzevari University
Physical Review D | Year: 2017

It has been shown that the product of the entropies of the inner Cauchy and outer event horizon of the charged axisymmetric and stationary black holes is a universal formula, which is independent of the black hole's mass. In this paper, we investigate this universality for the two kinds of rotating black holes in the three-dimensional gravity models. In fact, we study the spacelike warped anti-de Sitter black hole in the new massive gravity and the Bañados, Teitelboim, and Zanelli black hole in the minimal massive gravity. We show that this rule is held in the first theory. By contrast, in the latter case which includes a holographic gravitational anomalous term, we obtain that the universality does not work and the product depends on the mass. As a complement to the above verification, we also study the thermodynamic properties of these black holes. © 2017 American Physical Society.

Baghayeri M.,Hakim Sabzevari University | Nazarzadeh Zare E.,University of Mazandaran | Mansour Lakouraj M.,University of Mazandaran
Biosensors and Bioelectronics | Year: 2014

The novel biocompatible poly(p-phenylenediamine) (PpPDA)-Fe3O4 nanocomposite (PpPDA@Fe3O4) was synthesized via emulsion polymerization. The PpPDA@Fe3O4 nanocomposite was characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). The PpPDA@Fe3O4 nanocomposite was then used as substrate for the immobilization of hemoglobin (Hb) and their bioelectrochemical behaviors were studied. Electrochemical impedance spectroscopy was used to confirm the adsorption of Hb onto the surface of PpPDA@Fe3O4 nanocomposite. The Hb immobilized on PpPDA@Fe3O4 nanocomposite retained its near-native conformations as characterized by the FT-IR. A pair of well-defined redox peaks of Hb was obtained at the Hb-PpPDA@Fe3O4 modified glassy carbon electrode (Hb-PpPDA@Fe3O4/GCE) through direct electron transfer between the protein and the underlying electrode. The proposed biosensor showed good reproducibility and high sensitivity to H2O2 with the detection limit of 0.21μM (S/N=3). In the range of 0.5-400.0μM, the catalytic reduction current of H2O2 was proportional to its concentration. The apparent Michaelis-Menten constant of Hb on the PpPDA@Fe3O4 nanocomposite was estimated to be 0.088mM, showing its high affinity. © 2014.

The presented Mathematica code is an efficient tool for simulation of planar channeling radiation spectra of relativistic electrons channeled along major crystallographic planes of a diamond-structure single crystal. The program is based on the quantum theory of channeling radiation which has been successfully applied to study planar channeling at electron energies between 10 and 100 MeV. Continuum potentials for different planes of diamond, silicon and germanium single crystals are calculated using the Doyle-Turner approximation to the atomic scattering factor and taking thermal vibrations of the crystal atoms into account. Numerical methods are applied to solve the one-dimensional Schrödinger equation. The code is designed to calculate the electron wave functions, transverse electron states in the planar continuum potential, transition energies, line widths of channeling radiation and depth dependencies of the population of quantum states. Finally the spectral distribution of spontaneously emitted channeling radiation is obtained. The simulation of radiation spectra considerably facilitates the interpretation of experimental data. © 2012 Elsevier B.V. All rights reserved.

Bahrami S.,Hakim Sabzevari University
Geomorphology | Year: 2013

Alluvial fans are important landforms where their morphology and morphometry reflect changes in tectonic, climate, base level, and drainage basin characteristics. Along the margins of tectonically active mountain ranges like the Zagros Mountains, alluvial fans are generally assumed to act as useful landforms for identifying the level of tectonic activity. The purpose of this paper is to evaluate the relationship between active tectonics and morphometric characteristics of alluvial fans around Danehkhoshk anticline in the Simply Folded Belt of Zagros. Morphometric characteristics of alluvial fans, such as area (FA), slope (SF) length of base (BF), width/length ratio (W/L), radius (R), sweep angle (SA) and entrenchment (E) as well as valley floor width-to-height ratio (Vf) and strata dips of anticline limbs (DAL), were measured. The study area was sub-divided into eight tectonic zones and then the mean values of the above-mentioned parameters were calculated in each zone. Result reveals that values of SA, BF and E are directly proportional to DAL. The poor relationships between catchment characteristics (slope and area) and fan parameters are probably due to extensive karstic landforms of catchments having complex hydrologic systems and, hence, result in complex catchment/fan relations. The highly entrenched fans with high sweep angles and long bases are characteristic of tectonically active fronts of Danehkhoshk anticline, having V-shaped valleys (higher Vf values), steep triangular facets and more rotated limbs (higher DAL values). Apart from the tectonic control on fan development, the fan head entrenchment and negative accumulation spaces on most alluvial fans can be attributed to decreased sediment load and discharge the drier the present-day climate regime. © 2012 Elsevier B.V.

Bahrami S.,Hakim Sabzevari University
Tectonophysics | Year: 2013

Morphometric analysis of hierarchical arrangement of drainage networks allows to evaluate the effects of external controls especially tectonics on basin development. In this study, a quantitative method for calculation of stream's hierarchical anomaly number is introduced. Morphometric parameters such as hierarchal anomaly index ({increment}a), percent of asymmetry factor (PAF), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), stream's bifurcation ratio (Rb), bifurcation index (R), drainage density (Dd), drainage frequency (Df) and anticline's hinge spacing (Hs) of 15 basins in Zagros Mountains were examined. Results show that the strong correlations exist between pairs {increment}a-PAF (r. = 0.844), {increment}a-Bs (r. = 0.732), {increment}a-Bl/Bmw (r. = 0.775), {increment}a-R (r. = 0.517), PAF-Bl/Bmw (r. = 0.519), Bs-R (r. = 0.659), Bl/Bmw-R (r. = 0.703), Hs-{increment}a (r. = -. 0.708), Hs-PAF (r. = -. 0.529) and Hs-Bs (r. = -. 0.516). The variations in trend of anticlines control the shape of basins so that where anticlines hinges become closer to each other in the downstream direction, basin become narrower downward and hence the {increment}a increases. The more uplifted northeastern anticlines cause the trunk river of the basins to migrate toward the younger anticlines in southwest and hence {increment}a increases because the trunk river receives a lot of first order streams. Data reveal that the rate of {increment}a is higher in elongated synclinal basins. Due to the decrease in the intensity of deformation from northeast toward southwest of Zagros, the hinge spacing of anticlines increases southwestwards. Data reveal that the variation in hinge spacing of anticlines strongly controls the basin's shape and tilting as well as the hierarchical anomaly of drainage system. Since the elongation and tilting of basins are associated with the variations in rates of folding, uplift and hinge spacing of anticlines, it can be concluded that the hierarchical anomaly of drainages in studied basins is controlled by the intensity of Zagros tectonic activities. © 2013 Elsevier B.V.

Mahdavian Yekta D.,Hakim Sabzevari University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this paper, we study the three-dimensional minimal massive gravity (MMG) in the Hamiltonian formalism. At first, we define the canonical gauge generators as building blocks in this formalism and then derive the canonical expressions for the asymptotic conserved charges. The construction of a consistent asymptotic structure of MMG requires introducing suitable boundary conditions. In the second step, we show that the Poisson bracket algebra of the improved canonical gauge generators produces an asymptotic gauge group, which includes two separable versions of the Virasoro algebras. For instance, we study the Banados-Teitelboim-Zanelli (BTZ) black hole as a solution of the MMG field equations, and the conserved charges give the energy and angular momentum of the BTZ black hole. Finally, we compute the black hole entropy from the Cardy formula in the dual conformal field theory and show our result is consistent with the value obtained by using the Smarr formula from the holographic principle. © 2015 American Physical Society.

In this paper a synthetic nanocomposite based on poly(p-phenylenediamine) (PPD) and Fe3O4 nanoparticles (Fe3O4 NPs) introduced as a suitable substrate for enzyme immobilization. Glucose oxidase (GOD) was immobilized on PPD@Fe3O4 modified glassy carbon electrode (GCE). The immobilized GOD on PPD@Fe3O4 nanocomposite displayed a pair of well-defined quasi-reversible redox peaks with a formal potential of -0.41 V (vs. SCE) and a heterogeneous electron transfer rate constant (ks) of 3.76 s-1 in 0.1 M pH 7.0 PBS solution. The apparent Michaelis-Menten constant of the immobilized GOD was 0.42 mM, indicating an excellent catalytic activity and a notable affinity to detection of glucose. There was no interference from compounds commonly found in clinical samples and determination of glucose in clinical samples was successfully presented. © The Royal Society of Chemistry 2015.

Mahdavian Yekta D.,Hakim Sabzevari University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

We investigate the asymptotic structure of the three dimensional Warped Anti-de Sitter (WAdS3) black holes in the Bergshoeff-Hohm-Townsend (BHT) massive gravity using the canonical Hamiltonian formalism. We define the canonical asymptotic gauge generators, which produce the conserved charges and the asymptotic symmetry group for the WAdS3 black holes. The attained symmetry group is described by a semi-direct sum of a Virasoro and a Kač-Moody algebra. Using the Sugawara construction, we obtain a direct sum of two Virasoro algebras. We show that not only the asymptotic conserved charges satisfy the first law of black hole thermodynamics, but also they lead to the expected Smarr formula for the WAdS3 black holes. We also show that the black hole's entropy obeys the Cardy formula of the dual conformal field theory (CFT). © 2016 The Author.

Loading Hakim Sabzevari University collaborators
Loading Hakim Sabzevari University collaborators