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## Publications

Publications (330)

Background:
Urinary tract infections (UTIs) and bacterial resistance to antibiotics is global health problem and a threat to public health in many countries.
Aims:
The study aimed to determine the prevalence of MDR Escherichia coli and Klebsiella pneumoniae in UTI patients.
Materials & methods:
The midstream urine samples of 120 patients were...

Cytomegalovirus (CMV) is prevalent worldwide. It belongs to the β-herpesvirinae subfamily of
Herpesviridae and comprises a double-stranded linear DNA genome and capsid, surrounded by an
envelope. CMV infection is most prominently found in patients with kidney failure caused by various
possible reasons such as urinary tract infection or systemic dis...

BACKGROUND: Urinary tract infections (UTIs) are common health infections in pregnant women with high complications. Many of the worldwide population suffer from vitamin D deficiency (VDD) due to insufficient exposure to sunlight. The relationship between VDD and UTI and giving vitamin D supplementation contributes to preventing UTI.

Tunneling transport across the p-n-p junction of Weyl semimetal with tilted energy dispersion is investigated. We report that the electrons around different valleys experience opposite direction refractions at the barrier interface when the energy dispersion is tilted along one of the transverse directions. Chirality dependent refractions at the ba...

Clinical specimens were collected from 120 patients, 44 of them are males and 76 females with age range 1-70 years. A total of 49(40.8%) isolates were diagnosed as P. aeruginosa based on a number of tests and confirming by using 16SrDNA gene specific for P. aeruginosa. Results showed that the highest antibiotic resistance was in 40(81.6%) isolates...

One of the most common pathogens that are multidrug resistant and colonize burns wounds is Pseudomonas aeruginosa. This led researchers to find alternative treatment, so bacteriophages were alternative treatment methods used against bacterial infections. The phages were isolated from sewage and urine. Morphology of purified phages was examined by u...

The Rashba eﬀect gives rise to the key feature of chiral spin texture. Recently it was demonstrated that the orbital angular momentum (OAM) texture forms the underlying basis for Rashba spin texture. Here we solve a model Hamiltonian of a generic p-orbital system in the presence of crystal field, internal spin-orbit coupling (SOC) and inversion sym...

In order to enhance the magnitude of spin-orbit torque (SOT), considerable experimental works have been devoted to studying the thickness dependence of the different layers in multilayers consisting of heavy metal (HM), ferromagnet (FM), and capping layers. Here, we present a theoretical model based on the spin-drift-diffusion formalism to investig...

The study was carried out to isolate, purify and quantification of bacteriophages against Multiple Drugs Resistance (MDR) Pseudomonas aeruginosa from different sources, also the characterization of these bacteriophages with animal experiments using a bacteriophage as a treatment for mice experimentally infected with MDR P. aeruginosa, furthermore,...

Recently many novel magnetoresistance (MR) phenomena have been reported from studies of two dimensional (2D) materials. Here, we report on the exotic transport behavior of VS2. A large negative and quadratic MR of -10% is observed for an in-plane magnetic field B up to 14 T. Remarkably, when the applied field deviates from the in-plane orientation...

We adopt the tight-binding mode-matching method to study the strain effect on silicene heterojunctions. It is found that valley- and spin-dependent separation of electrons cannot be achieved by the electric field only. When a strain and an electric field are simultaneously applied to the central scattering region, not only are the electrons of vall...

In this work, we show that the disorder-free Kubo formula for the nonequilibrium value of an observable due to a dc electric field, represented by Exx̂ in the Hamiltonian, can be interpreted as the standard time-independent theory response of the observable due to a time- and position-independent perturbation HMF. We derive the explicit expression...

We study the combined effects of separated parallel disks, birefringence and surface currents on the Casimir force and torque. All three contribute to the Casimir force and surface currents from graphene permit tuning and switching from attraction to repulsion thus allowing for an oscillating Casimir force which can be relevant to parametric amplif...

We investigate the thickness optimization for maximum current-induced spin-orbit torque (SOT) generated by topological surface states (TSS’s) in a bilayer system comprising of a ferromagnetic layer coupled to a thin topological insulator (TI) film. We show that by reducing the TI thickness, two competing effects on the SOT are induced: (i) the torq...

Despite the inefficiencies associated with current-induced spin torques, they remain the predominant mode of skyrmion propulsion. In this work, we demonstrate numerically that skyrmions can be transported much more efficiently with a voltage-controlled magnetic anisotropy (VCMA) gradient. An analytical model was developed to understand the underlyi...

We introduced concept of force in describing spin-orbit torque (SOT) in spin-orbit coupling systems. We showed that the damping-like torque is induced when the system is not in steady state, i.e., when the electron spin is still precessing ($d{\bf s}/dt\ne 0$) and the electron being accelerated by, e.g., an electric field. The damping-like SOT can...

Weyl semimetals are recently discovered states of quantum matter, which generally possess tilted energy dispersion. Here, we investigate the electron tunneling through a Weyl semimetal p-n-p junction. The angular dependence of electron tunneling exhibits an anomalous profile such that perfect transmission angles are shifted along the direction of t...

In this work, we show that (real space) curvature in the geometry of curved waveguides with Rashba spin orbit interactions (RSOIs) can lead to out-of-plane spin accumulations. We first derive the RSOI Hamiltonian on arbitrarily curved surfaces. We then analyze the effects of curvature with two distinct methods. We first apply an adiabatic approxima...

A topological insulator (TI) thin film differs from the more typically studied thick TI system in that the former has both a top and a bottom surface where the states localized at both surfaces can couple to one other across the finite thickness. An out-of-plane magnetic field leads to the formation of discrete Landau level states in the system, wh...

We use the gauge formalism to investigate the current-induced spin dynamics in ferromagnetic media with spatially varying local magnetization, which is coupled to various material systems exhibiting linear spin-orbit coupling (SOC) effects, such as semiconductor and graphene materials. We perform a gauge transformation to the system, and obtain a g...

We study the quantum capacitance in a topological insulator thin film system magnetized in the in-plane direction in the presence of an out-of-plane magnetic field and hexagonal warping. To first order, the modification in quantum capacitance due to hexagonal warping compared to the clean case, where both the in-plane magnetization and hexagonal wa...

We investigate the tunneling conductance of Weyl semimetal with tilted energy dispersion by considering electron transmission through a p-n-p junction with one-dimensional electric and magnetic barrier. In the presence of both electric and magnetic barriers, we found that a large conductance gap can be produced by the aid of tilted energy dispersio...

In this work, we show that the disorder-free Kubo formula for the non-equilibrium value of an observable due to a DC electric field, represented by $E_x\hat{x}$ in the Hamiltonian, can be interpreted as the standard time-independent theory response of the observable due to a time- and position-\textit{independent} perturbation $H_{MF}$. We derive t...

We investigate the current-induced spin-orbit torque in thin topological insulator (TI) films in the presence of hybridization between the top and bottom surface states. We formulate the relation between spin torque and TI thickness, from which we derived the optimal value of the thickness to maximize the torque. We show numerically that in typical...

We theoretically investigate the RKKY exchange coupling between two ferromagnets (FM) separated by a thin topological insulator film (TI). We find an unusual dependence of the RKKY exchange coupling on the TI thickness ($t_{TI}$). First, when $t_{TI}$ decreases, the coupling amplitude increases at first and reaches its maximum value at some critica...

Type-II Weyl semimetal is a new state of quantum matter discovered recently, which breaks Lorentz symmetry and possesses a tilted energy dispersion. Here, we investigate the effect of an applied electrical potential on type-II Weyl semimetal and find that application of gated or doped electrical potential does not only change the carrier concentrat...

We present arguments for a mass term in the Landau-Lifshitz-Gilbert equation based on the notion of mass as an inertial quantity. From trajectories of skyrmions in a confining potential and a 1-D potential we see evidence for a mass-inertia connection. We derive an expression for the effective mass for skyrmions, , where accounts for the mismatch b...

Topological insulator (TI) thin films differ from the more commonly studied semi-infinite bulk TIs in that the former possesses both top and bottom surfaces where the surface states localized at different surfaces can couple to one another due to the finite thickness of the film. In the presence of an in-plane mangnetization TI thin films display t...

Topological insulators(TI) are a unique class of materials with exotic surface electronic properties. When a ferromagnetic (FM) layer is added on the top of a thin film 3D TI, the surface states gain magnetization. We point out here that the in-plane magnetization and the Fermi surface anisotropy due to hexagonal warping mediate changes in the quan...

In this work we derive an effective Hamiltonian for the surface states of a hollow topological insulator (TI) nanotube with finite width walls. Unlike a solid TI cylinder, a TI nanotube possesses both an inner as well as outer surface on which the states localized at each surface are coupled together. The curvature along the circumference of the na...

We propose a multilayer device comprising of a thin-film-based ferromagnetic hetero-structure (FMH) deposited on a diamond layer doped with nitrogen vacancy centers (NVC's). We find that when the NVC's are in close proximity (1-2 nm) with the FMH, the exchange energy is comparable to, and may even surpass the magnetostatic interaction energy. This...

In this work we study the spin accumulation due to an in-plane electric field in an asymmetric topological insulator (TI) thin film system with an out of plane magnetic field and an in-plane magnetization. A TI thin film differs from the more typically studied thick TI system in that the former has both a top and a bottom surface where the states l...

Most theoretical studies of tunneling in Dirac and the closely related Weyl semimetals have modeled these materials as single Weyl nodes described by the three-dimensional Dirac equation $H = v_f \vec{p}\cdot\vec{\sigma}$. The influence of scattering between the different valleys centered around different Weyl nodes, and the Fermi arc states which...

The spin gauge field formalism has been used to explain the emergence of out of plane spin accumulation in two-dimensional spin orbit interaction (SOI) systems in the presence of an in-plane electric field. The adiabatic alignment of the charge carrier spins to the momentum dependent SOI field, which changes in time due to the electric field, can b...

Gauge concept evolves in the course of nearly one century from Faraday's rather obscure electrotonic state of matter to the physically significant Yang-Mills that underpin today's standard model. As gauge theories improve, links are established with modern observations, e.g. in the Aharonov-Bohm effect, the Pancharatnam-Berry's phase, superconducti...

Klein tunneling refers to the absence of normal backscattering of electrons even under the case of high potential barriers. At the barrier interface, the perfect matching of electron and hole wavefunctions enables a unit transmission probability for normally incident electrons. It is theoretically and experimentally well understood in two-dimension...

We present a single barrier system to generate pure valley-polarized current in monolayergraphene. A uniaxial strain is applied within the barrier region, which is delineated by localized magnetic field created by ferromagnetic stripes at the region’s boundaries. We show that under the condition of matching magnetic field strength, strain potential...

The effective Hamiltonian of the surface states on semi-infinite slabs of the topological insulators (TI) Bi2Te3 and Bi2Se3 require the addition of a cubic momentum hexagonal warping term on top of the usual Dirac fermion Hamiltonian in order to reproduce the experimentally measured constant energy contours at intermediate values of Fermi energy. I...

We study the Thiele equation for current-induced motion in a skyrmion lattice
through two soluble models of the pinning potential. Comprised by a Magnus
term, a dissipative term and a pinning force, Thiele's equation resembles
Newton's law but in virtue of the topological character of the first two, it
differs significantly from Newtonian mechanics...

In this work we show that (real space) curvature in the geometry of curved waveguides with Rashba spin orbit interaction (RSOI) can lead to out of plane spin accumulations. We first derive the RSOI Hamiltonian on arbitrarily curved surfaces. We then analyze the effects of curvature with two distinct methods. We first apply an adiabatic approximatio...

A trilayer system with perpendicularly magnetized metallic (FMM) free-layer, heavy metal (HM) with strong spin-hall effect and ferromagnetic insulating (FMI) substrate has been proposed to significantly enhance the torque acting on FMM. Its magnitude can be engineered by configuring the magnetization of the FMI. The analytical solution has been dev...

In this work we study the effects of in-plane magnetic fields on thin films
of the Dirac Semimetal (DSM) \ce{Na2Bi} where one of the in-plane directions is
perpendicular to the $k$-separation between the two Weyl points for each spin
orientation. We show numerically that the states localized near the surface of
these thin films are related to the F...

The three-dimensional topological insulator \ce{Bi2Te3} differs from other
topological insulators in the \ce{Bi2Se3} family in that the effective
Hamiltonian of its surface states on a flat semi-infinite slab requires the
addition of a cubic momentum hexagonal warping term in order to reproduce the
experimentally measured constant energy contours....

Gauge concept evolves in the course of nearly one century from Faraday’s rather obscure electrotonic state of matter to the physically significant Yang–Mills that underpin today’s standard model. As gauge theories improve, links are established with modern observations, e.g. in the Aharonov–Bohm effect, the Pancharatnam–Berry’s phase, superconducti...

We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green's function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off...

The introduction of a strong Rashba spin orbit coupling (SOC) had been
predicted to enhance the spin motive force (SMF) [see Phys. Rev. Lett. {\bf
108}, 217202 (2012)]. In this work, we predict further enhancement of the SMF
by time modulation of the Rashba coupling $\alpha_R$, which induces an
additional electric field $E^R_d=\pm{\dot \alpha_R} m_...

Electron transport in Bi2Se3 topological insulator slabs is investigated in the thermal activation regime (>50 K) both in the absence (ballistic) and presence of weak and strong acoustic phonon scattering using the non-equilibrium Green function approach. Resistance of the slab is simulated as a function of temperature for a range of slab thickness...

For graphene heterojunctions, perfect transmission of the electrons injected at normal direction can occur across an arbitrarily high and wide barrier, a phenomenon known as Klein tunneling [1-2]. Due to the effect of Klein tunneling, it is difficult to confine the massless Dirac fermions using the electrostatic methods [3-4]. Recently, it is repor...

The spin orbit coupling spin torque consists of the field-like [REF: S.G. Tan
et al., arXiv:0705.3502, (2007).] and the damping-like terms [REF: H.
Kurebayashi et al., Nature Nanotechnology 9, 211 (2014).] that have been widely
studied for applications in magnetic memory. We focus, in this article, not on
the spin orbit effect producing the above s...

We study the Thiele equation for the motion of skyrmions in a lattice under a spin current of electrons. We show that a threshold current for conduction electrons exists below which skyrmions are blocked. By mimicking a pinning center with a localized attractive potential, we study the effects of the Magnus force and the damping force and find that...

We obtain the lowest energy solutions for the skymion field equations and
their corresponding vortex structures. Two nondegenerate solutions emerge with
their vortex swirls in opposite directions. The solutions are associated with
an extremum property, which favors an array of almost hexagonal shape. We
predict that a regular hexagonal lattice must...

In this work we study the surface states of a topological insulator (TI) cylinder with a magnetization in the radial, azimuthal and axial directions. We derive the eigenenergies and eigenstates, and show that a state with a quantum number associated with the orbital angular momentum incident at a junction between a source TI cylinder and a coaxial...

The surface states of topological insulators (TI) possess a linear dispersion in the low-energy approximation, and are protected against time-reversal-invariant perturbations such as non-magnetic impurities, defects [1-3]. The chiral nature of TI surface states can induce perfect quantum tunneling for Dirac fermions incident in the normal direction...

For a skyrmion lattice phase of chiral
magnets, we compare predictions of the Landau-Lifshitz-Gilbert (LLG) and Thiele equations for the current-induced drift velocity for a given constant spin velocity. Instead of integrating the equations over a unit cell, we only perform an angle average, while retaining information on the radial dependence of v...