The Experts below are selected from a list of 14685 Experts worldwide ranked by ideXlab platform

Gaohua Liao - One of the best experts on this subject based on the ideXlab platform.

  • electronic structures of free standing nanowires made from indirect bandgap semiconductor gallium phosphide
    2016
    Co-Authors: Gaohua Liao, Ning Luo, Keqiu Chen
    Abstract:

    We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP) - a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the Bands show anti-crossing structures, while the Bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the Conduction Bands, while the maximum of the valence Bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest Conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest Conduction Bands and the highest valence Bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. (Less)

  • electronic structures of free standing nanowires made from indirect bandgap semiconductor gallium phosphide
    2016
    Co-Authors: Gaohua Liao, Ning Luo, Keqiu Chen
    Abstract:

    We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)--a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the Bands show anti-crossing structures, while the Bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the Conduction Bands, while the maximum of the valence Bands is always at the $\Gamma$-point. Using double group theory, we analyze the symmetry properties of the lowest Conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest Conduction Bands and the highest valence Bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula.

R. S. Eisenberg - One of the best experts on this subject based on the ideXlab platform.

  • coulomb blockade model of permeation and selectivity in biological ion channels
    2015
    Co-Authors: Kh. I. Kaufman, Peter V. E. Mcclintock, R. S. Eisenberg
    Abstract:

    Biological ion channels are protein nanotubes embedded in, and passing through, the bilipid membranes of cells. Physiologically, they are of crucial importance in that they allow ions to pass into and out of cells, fast and efficiently, though in a highly selective way. Here we show that the Conduction and selectivity of calcium/sodium ion channels can be described in terms of ionic Coulomb blockade in a simplified electrostatic and Brownian dynamics model of the channel. The Coulomb blockade phenomenon arises from the discreteness of electrical charge, the strong electrostatic interaction, and an electrostatic exclusion principle. The model predicts a periodic pattern of Ca2+ Conduction versus the fixed charge Qf at the selectivity filter (Conduction Bands) with a period equal to the ionic charge. It thus provides provisional explanations of some observed and modelled Conduction and valence selectivity phenomena, including the anomalous mole fraction effect and the calcium Conduction Bands. Ionic Coulomb blockade and resonant Conduction are similar to electronic Coulomb blockade and resonant tunnelling in quantum dots. The same considerations may also be applicable to other kinds of channel, as well as to charged artificial nanopores.

  • multi ion Conduction Bands in a simple model of calcium ion channels
    2013
    Co-Authors: I. Kaufman, Peter V. E. Mcclintock, Dmitry G. Luchinsky, R. Tindjong, R. S. Eisenberg
    Abstract:

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. With increasing Qf, there are distinct regions of high conductance (Conduction Bands) M0, M1, M2 separated by regions of almost zero-conductance (stop-Bands). Two of these Conduction Bands, M1 and M2, are related to the saturated calcium occupancies of P = 1 and P = 2, respectively and demonstrate self-sustained conductivity. Despite the model's limitations, its M1 and M2 Bands show high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels. The non-selective band M0 can be identified with a non-selective cation channel, or with OmpF porin.

Keqiu Chen - One of the best experts on this subject based on the ideXlab platform.

  • electronic structures of free standing nanowires made from indirect bandgap semiconductor gallium phosphide
    2016
    Co-Authors: Gaohua Liao, Ning Luo, Keqiu Chen
    Abstract:

    We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP) - a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the Bands show anti-crossing structures, while the Bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the Conduction Bands, while the maximum of the valence Bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest Conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest Conduction Bands and the highest valence Bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. (Less)

  • electronic structures of free standing nanowires made from indirect bandgap semiconductor gallium phosphide
    2016
    Co-Authors: Gaohua Liao, Ning Luo, Keqiu Chen
    Abstract:

    We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)--a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the Bands show anti-crossing structures, while the Bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the Conduction Bands, while the maximum of the valence Bands is always at the $\Gamma$-point. Using double group theory, we analyze the symmetry properties of the lowest Conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest Conduction Bands and the highest valence Bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula.

Dmitry G. Luchinsky - One of the best experts on this subject based on the ideXlab platform.

  • Multi-ion Conduction Bands in a simple model of calcium ion channels
    2013
    Co-Authors: I. Kaufman, Peter V. E. Mcclintock, Dmitry G. Luchinsky, R. Tindjong, Robert S. Eisenberg
    Abstract:

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. This structure consists of distinct regions of high conductance (Conduction Bands) M0, M1, M2 separated by regions of zero-conductance (stop-Bands). Two of these Conduction Bands, M1 and M2, demonstrate high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels.

  • multi ion Conduction Bands in a simple model of calcium ion channels
    2013
    Co-Authors: I. Kaufman, Peter V. E. Mcclintock, Dmitry G. Luchinsky, R. Tindjong, R. S. Eisenberg
    Abstract:

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. With increasing Qf, there are distinct regions of high conductance (Conduction Bands) M0, M1, M2 separated by regions of almost zero-conductance (stop-Bands). Two of these Conduction Bands, M1 and M2, are related to the saturated calcium occupancies of P = 1 and P = 2, respectively and demonstrate self-sustained conductivity. Despite the model's limitations, its M1 and M2 Bands show high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels. The non-selective band M0 can be identified with a non-selective cation channel, or with OmpF porin.

Peter V. E. Mcclintock - One of the best experts on this subject based on the ideXlab platform.

  • coulomb blockade model of permeation and selectivity in biological ion channels
    2015
    Co-Authors: Kh. I. Kaufman, Peter V. E. Mcclintock, R. S. Eisenberg
    Abstract:

    Biological ion channels are protein nanotubes embedded in, and passing through, the bilipid membranes of cells. Physiologically, they are of crucial importance in that they allow ions to pass into and out of cells, fast and efficiently, though in a highly selective way. Here we show that the Conduction and selectivity of calcium/sodium ion channels can be described in terms of ionic Coulomb blockade in a simplified electrostatic and Brownian dynamics model of the channel. The Coulomb blockade phenomenon arises from the discreteness of electrical charge, the strong electrostatic interaction, and an electrostatic exclusion principle. The model predicts a periodic pattern of Ca2+ Conduction versus the fixed charge Qf at the selectivity filter (Conduction Bands) with a period equal to the ionic charge. It thus provides provisional explanations of some observed and modelled Conduction and valence selectivity phenomena, including the anomalous mole fraction effect and the calcium Conduction Bands. Ionic Coulomb blockade and resonant Conduction are similar to electronic Coulomb blockade and resonant tunnelling in quantum dots. The same considerations may also be applicable to other kinds of channel, as well as to charged artificial nanopores.

  • Multi-ion Conduction Bands in a simple model of calcium ion channels
    2013
    Co-Authors: I. Kaufman, Peter V. E. Mcclintock, Dmitry G. Luchinsky, R. Tindjong, Robert S. Eisenberg
    Abstract:

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. This structure consists of distinct regions of high conductance (Conduction Bands) M0, M1, M2 separated by regions of zero-conductance (stop-Bands). Two of these Conduction Bands, M1 and M2, demonstrate high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels.

  • multi ion Conduction Bands in a simple model of calcium ion channels
    2013
    Co-Authors: I. Kaufman, Peter V. E. Mcclintock, Dmitry G. Luchinsky, R. Tindjong, R. S. Eisenberg
    Abstract:

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. With increasing Qf, there are distinct regions of high conductance (Conduction Bands) M0, M1, M2 separated by regions of almost zero-conductance (stop-Bands). Two of these Conduction Bands, M1 and M2, are related to the saturated calcium occupancies of P = 1 and P = 2, respectively and demonstrate self-sustained conductivity. Despite the model's limitations, its M1 and M2 Bands show high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels. The non-selective band M0 can be identified with a non-selective cation channel, or with OmpF porin.