Aatef Hobiny

Understanding the adsorption mechanism of Ni(II) on graphene oxides by batch experiments and density functional theory studies

The graphene oxides (GOs) have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable materials for the efficient elimination of heavy metal ions from aqueous solutions. Herein the sorption of Ni(II) on GOs was studied using batch experiments, and the results showed that the sorption of Ni(II) is strongly dependent on pH and ionic strength at pH<8, and independent of ionic strength at pH>8. The sorption of Ni(II) is mainly dominated by outer-sphere surface complexation and ion exchange at low pH, and by inner-sphere surface complexation at high pH. The interaction of Ni(II) with GOs was also investigated by theoretical density functional theory (DFT) calculations, and the results show that the sorption of Ni(II) on GOs is mainly attributed to the–COH and–COC groups and the DFT calculations show that Ni(II) forms stable GO_Ni_triplet structure with the binding energy of -39.44 kcal/mol, which is in good agreement with the batch sorption experimental results. The results are important for the application of GOs as adsorbents in the efficient removal of Ni(II) from wastewater in environmental pollution cleanup.

Formation of Autapse Connected to Neuron and Its Biological Function

Autapse is a specific synapse connected to the neuron via close loop, and its functional adjusting is described by applying time-delayed feedback on the membrane potential of the neuron. This paper discussed the possible formation mechanism and biological function of autapse connection on neurons. We believe that the formation and growth of autapse connected to neuron can be associated with injury on axon and blocking in signal transmission; thus auxiliary loop is developed to form an autapse. When autapse is set up, it can propagate the signals and change the modes of electrical activities under self-adaption. Based on the cable neuron model, the injury on axon is generated by poisoning and blocking in ion channels (of sodium); thus the conductance of ion channels are changed to form injury-associated defects. Furthermore, auxiliary loop with time delay is designed to restore and enhance signal propagation by setting different time delays and feedback gains. The numerical studies confirmed that appropriate time delay and feedback gain in electric or chemical autapse can help signal (or wave generated by external forcing) propagation across the blocked area. As a result, formation of autapse could be dependent on the injury of neuron and further enhances the self-adaption to external stimuli.

Surface Modification of Graphene Oxides by Plasma Techniques and Their Application for Environmental Pollution Cleanup.

Graphene oxides (GOs) have come under intense multidisciplinary study because of their unique physicochemical properties and possible applications. The large amount of oxygen-containing functional groups on GOs leads to a high sorption capacity for the removal of various kinds of organic and inorganic pollutants from aqueous solutions in environmental pollution cleanup. However, the lack of selectivity results in difficulty in the selective removal of target pollutants from aqueous solutions in the presence of other coexisting pollutants. Herein, the surface grafting of GOs with special oxygen-containing functional groups using low-temperature plasma techniques and the application of the surface-modified GOs for the efficient removal of organic and inorganic pollutants in environmental pollution are reviewed. This paper gives an account of our research on the application of GO-based nanomaterials in environmental pollution cleanup, including: (1) the synthesis and surface grafting of functional groups on GOs, summarizing various types of low-temperature plasma techniques for the synthesis of graphene/GOs; and (2) the application of graphene/GOs and their composites for the efficient removal of organic and inorganic pollutants from aqueous solutions, including the interaction mechanism according to recently published results.

Analytical Solution of Thermoelastic Damping in a Nanoscale Beam using the Fractional Order Theory of Thermoelasticity

In this paper, we study the generalized thermoelastic vibration of a bounded nano-beam resonator under fractional order theory of thermoelasticity. The theory of generalized thermoelasticity with one relaxation time can be established in the limit as the special cases of the present model. The effect of fractional parameter is investigated on the nano-beam resonator for beams with clamped ends. Analytical expressions for the deflection, temperature change, frequency shift, and thermoelastic damping have been derived for the beam. The effect of the fractional parameter on the variation of frequency shifts and thermoelastic damping is analyzed graphically.

Self-error-rejecting photonic qubit transmission in polarization-spatial modes with linear optical elements

We present an original self-error-rejecting photonic qubit transmission scheme for both the polarization and spatial states of photon systems transmitted over collective noise channels. In our scheme, we use simple linear-optical elements, including half-wave plates, 50:50 beam splitters, and polarization beam splitters, to convert spatial-polarization modes into different time bins. By using postselection in different time bins, the success probability of obtaining the uncorrupted states approaches 1/4 for single-photon transmission, which is not influenced by the coefficients of noisy channels. Our self-error-rejecting transmission scheme can be generalized to hyperentangled n-photon systems and is useful in practical high-capacity quantum communications with photon systems in two degrees of freedom.

Hyperentanglement concentration for polarization–spatial–time-bin hyperentangled photon systems with linear optics

Hyperentanglement has significant applications in quantum information processing. Here we present an efficient hyperentanglement concentration protocol (hyper-ECP) for partially hyperentangled Bell states simultaneously entangled in polarization, spatial-mode and time-bin degrees of freedom (DOFs) with the parameter-splitting method, where the parameters of the partially hyperentangled Bell states are known to the remote parties. In this hyper-ECP, only one remote party is required to perform some local operations on the three DOFs of a photon, only the linear optical elements are considered, and the success probability can achieve the maximal value. Our hyper-ECP can be easily generalized to concentrate the N-photon partially hyperentangled Greenberger–Horne–Zeilinger states with known parameters, where the multiple DOFs have largely improved the channel capacity of long-distance quantum communication. All of these make our hyper-ECP more practical and useful in high-capacity long-distance quantum communication.

Practical entanglement concentration of nonlocal polarization-spatial hyperentangled states with linear optics

We present some different hyperentanglement concentration protocols (hyper-ECPs) for nonlocal N-photon systems in partially polarization-spatial hyperentangled states with known parameters, resorting to linear optical elements only, including those for hyperentangled Greenberger–Horne–Zeilinger-class states and the ones for hyperentangled cluster-class states. Our hyper-ECPs have some interesting features. First, they require only one copy of nonlocal N-photon systems and do not resort to ancillary photons. Second, they work with linear optical elements, neither Bell-state measurement nor two-qubit entangling gates. Third, they have the maximal success probability with only a round of entanglement concentration, not repeating the concentration process some times. Fourth, they resort to some polarizing beam splitters and wave plates, not unbalanced beam splitters, which make them more convenient in experiment.

On Existence of Solutions for Nonlinear q-difference Equations with Nonlocal q-integral Boundary Conditions

AbstractIn this paper, we discuss the existence of solutions for nonlinear q-difference equations with nonlocal q-integral boundary conditions. The first part of the paper deals with some existence and uniqueness results obtained by means of standard tools of fixed point theory. In the second part, sufficient conditions for the existence of extremal solutions for the given problem are established. The results are well illustrated with the aid of examples.

Photo-thermal-elastic interaction in an unbounded semiconducting medium with spherical cavity due to pulse heat flux

Abstract In this work, the photothermal waves in an unbounded semiconducting medium with spherical cavity are studied. This problem is solved using the theory of coupled plasma, thermal, and elastic wave. An unbounded material, elastic semiconductor containing a spherical cavity with isotropic and homogeneous thermal and elastic properties has been considered. The inner surface of the cavity is taken traction-free and subjected to an exponentially decaying pulse boundary heat flux. Laplace transform techniques and eigenvalue approach were used to obtain the analytical solutions. Numerical computations have been done for silicon-like semiconductor material, and the results are presented graphically to estimate the effect of time and the coupling between the plasma, thermal, and elastic waves.

On the libration collinear points in the restricted three – body problem

Abstract In the restricted problem of three bodies when the primaries are triaxial rigid bodies, the necessary and sufficient conditions to find the locations of the three libration collinear points are stated. In addition, the Linear stability of these points is studied for the case of the Euler angles of rotational motion being θi = 0, ψi + φi = π/2, i = 1, 2 accordingly. We underline that the model studied in this paper has special importance in space dynamics when the third body moves in gravitational fields of planetary systems and particularly in a Jupiter model or a problem including an irregular asteroid.