Nuclear transfer in leach (Paramisgurnus dabryanus Sauvage) by cell-to-cell electrofusion

To study nuclear transfer in the leach (Paramisgurnus dabryanus Sauvage), blastula and gastrula cells were fused with UV-inactivated oocytes by cell-to-cell electrofusion. To facilitate nuclear transfer, blastula and gastrula cells were cultured or incubated at 4 degreesC in different solutions. TC-199 medium supplemented with 20% calf serum was the best culture solution, and effectively retained the totipotence of blastula or gastrula cells for up to 10 days, It was found that gastrula cells incubated at 4 degreesC had the same totipotence as blastula cells, The optimal UV dosage for inactivation of the oocyte chromatin was 180-240 mJ cm(-2). Electrofusion was carried out in a cone-shaped fusion chamber, which permitted the recipient oocyte and the donor blastula cell to contact one another. The electrofusion procedure resulted in a 10% success rate of normal-appearing fish. Genetic analysis indicated that the nuclear material originated from the donor cell (blastomere) and the oocyte pronucleus did not take part in development.

The onset of foreign gene transcription in nuclear-transferred embryos of fish

The transcriptional onset of hGH-transgene in fish was studied in the following three cases: the first is in MThGH-transgenic F-4 common carp (Cyprinus carpio) embryos, the second is in nuclear-transferred embryos supported by the transgenic F-4 embryonic nuclei, and the third is in nuclear-transferred embryos supported by the transgenic F-4 tail-fin nuclei. RT-PCR results show that the hGH-transgene initiates its transcriptional activity from early-gastrula stage, the early blastula stage and even 16-cell stage in the first, second and third cases, respectively. it looks like that fish egg cytoplasm could just offer a very restricted reprogramming on transcriptional activity of specific gene in differentiated cell nuclei by nuclear transplantation.

Nuclear transplantation with early-embryonic cells of transgenic fish

Like other transgenic animals, transgenic fishes produced by microinjection are transgenic mosaics. In order to produce homogenous transgenic fish, the transgenic blastula or gastrula cells were dissociated from Carassius auratus, Pengze var, and Cyprinus carpio, Huanghe var., and the nuclei were transferred into the mature eggs of the same species via microinjection or electro-fusion. Five nuclear-transferred Carassius auratus, Pengze var. and one Cyprinus carpio, Huanghe var. were obtained and the existence of the transgene was detected. The possibility of generating homogenous strain of transgenic fish by nuclear transplantation with transgenic early-embryonic cells is discussed.

Temperature dependence of hole spin relaxation in ultrathin InAs monolayers

The temperature dependence of hole spin relaxation time in both neutral and n-doped ultrathin InAs monolayers has been investigated. It has been suggested that D'yakonov-Perel (DP) mechanism dominates the spin relaxation process at both low and high temperature regimes. The appearance of a peak in temperature dependent spin relaxation time reveals the important contribution of Coulomb scatterings between carriers to the spin kinetics at low temperature, though electron-phonon scattering becomes dominant at higher temperatures. Increased electron screening effect in the n-doped sample has been suggested to account for the shortened spin relaxation time compared with the undoped one. The results suggest that hole spins are also promising for building solid-state qubits.

Spin injection in the multiple quantum-well LED structure with the Fe/AlO (x) injector

A spin-injection/-detection device has been fabricated based on the multiple quantum well light emitting diode (LED) structure. It is found that only a broad electroluminescence (EL) peak of a full width at half maximum of 8.6 nm appears at the wavelength of 801 nm in EL spectra with a circular luminescence polarization degree of 18%, despite PL spectra always show three well resolved peaks. The kinetic energy gained by injected electrons and holes in their drift along opposite directions broadens the EL peak, and makes three EL peaks converge together. The same process also destroys the injected spin polarization of electrons mainly dominated by the Bir-Aronov-Pikus spin relaxing mechanism.

DTADH and quantum critical phenomena caused by anisotropy and external magnetic field for spin-1/2 Heisenberg diamond chains

Using the transfer matrix renormalization group (TMRG) method, we study the connection between the first derivative of the thermal average of driving-term Hamiltonian (DTADH) and the trace of quantum critical behaviors at finite temperatures. Connecting with the exact diagonalization method, we give the phase diagrams and analyze the properties of each phase for both the ferromagnetic and anti-ferromagnetic frustrated J(3) anisotropy diamond chain models. The finite-temperature scaling behaviors near the critical regions are also investigated. Further, we show the critical behaviors driven by external magnetic field, analyze the formation of the 1/3 magnetic plateau and the influence of different interactions on those critical points for both the ferrimagnetic and anti-ferromagnetic distorted diamond chains.

Tuning of the two electron states in quantum rings through the spin-orbit interaction

The effect of the Coulomb interaction on the energy spectrum and anisotropic distribution of two electron states in a quantum ring in the presence of Rashba spin-orbit interaction (RSOI) and Dresselhaus SOI (DSOI) is investigated in the presence of a perpendicular magnetic field. We find that the interplay between the RSOI and DSOI makes the single quantum ring behaves like a laterally coupled quantum dot and the interdot coupling can be tuned by changing the strengths of the SOIs. The interplay can lead to singlet-triplet state mixing and anticrossing behavior when the singlet and triplet states meet with increasing magnetic field. The two electron ground state displays a bar-bell-like spatial anisotropic distribution in a quantum ring at a specific crystallographic direction, i.e., [110] or [1 (1) over bar0], which can be switched by reversing the direction of the perpendicular electric field. The ground state exhibits a singlet-triplet state transition with increasing magnetic field and strengths of RSOI and DSOI. An anisotropic electron distribution is predicted which can be detected through the measurement of its optical properties.

Direct detection of the relative strength of Rashba and Dresselhaus spin-orbit interaction: Utilizing the SU(2) symmetry

We propose a simple method to detect the relative strength of Rashba and Dresselhaus spin-orbit interactions in quantum wells (QWs) without relying on the directional-dependent physical quantities. This method utilizes the two different critical gate voltages that leading to the remarkable signals of SU(2) symmetry, which happens to reflect the intrinsic-structure-inversion asymmetry of the QW. We support our proposal by the numerical calculation of in-plane relaxation times based on the self-consistent eight-band Kane model. We find that the two different critical gate voltages leading to the maximum spin-relaxation times [one effect of the SU(2) symmetry] can simply determine the ratio of the coefficients of Rashba and Dresselhaus terms. Our proposal can also be generalized to extract the relative strengths of the spin-orbit interactions in quantum-wire and quantum-dot structures.

Spin-dependent transport and spin polarization in coupled quantum wells

We theoretically investigate the electron transport and spin polarization of two coupled quantum wells with Dresselhaus spin-orbit interaction. In analogy with the optical dual-channel directional coupler, the resonant tunneling effect is treated by the coupled-mode equations. We demonstrate that spin-up and -down electrons can be completely separated from each other for the system with an appropriate system geometry and a controllable barrier. Our result provides a new approach to construct spin-switching devices without containing any magnetic materials or applying a magnetic field. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2981204]

Electric tunable of electron spin polarization in hybrid magnetic-electric barrier structures

Electron spin-dependent transport properties have been theoretically investigated in two-dimensional electron gas (2DEG) modulated by the magnetic field generated by a pair of anti-parallel magnetization ferromagnetic metal stripes and the electrostatic potential provided by a normal metal Schottky stripe. It is shown that the energy positions of the spin-polarization extremes and the width of relative spin conductance excess plateau could be significantly manipulated by the electrostatic potential strength and width, as well as its position relative to the FM stripes. These interesting features are believed useful for designing the electric voltage controlled spin filters. (C) 2008 Elsevier B.V. All rights reserved.

Proposal for the direct optical detection of pure spin currents in semiconductors

We suggest a different practical scheme for the direct detection of pure spin current by using the two-color Faraday rotation of optical quantum interference process (QUIP) in a semiconductor system. We demonstrate theoretically that the Faraday rotation of QUIP depends sensitively on the spin orientation and wave vector of the carriers, and can be tuned by the relative phase and the polarization direction of the omega and 2 omega laser beams. By adjusting these parameters, the magnitude and direction of the spin current can be detected.

Spin states in semiconductor quantum dot with a single magnetic ion

We investigate theoretically CdTe quantum dots containing a single Mn2+ impurity, including the sp-d exchange interaction between carriers and the magnetic ion and the short-range exchange interaction between electron and hole. We find anticrossing behaviors in the energy spectrum of the electron-hole (e-h) pair that arise from the interplay between exchange interactions and the magnetic field. In addition to the s-d exchange interaction, we find that other mechanisms inducing the anticrossings become important in the strong heavy hole-light hole (hh-lh) mixing regime. The transition strengths between the states with spin projection of Mn2+ ion S-z not equal -5/2 (S-z = -5/2) decrease (increase) with increasing magnetic fields due to the alignment of the Mn2+ spin. The spin splitting of the e-h pair states depends sensitively on the external magnetic and electric field, which reveals useful information about the spin orientation and position of the magnetic ion. Meanwhile, the manipulation of the position of the magnetic ion offers us a way to control the spin splitting of the carriers. (C) 2008 Elsevier B.V. All rights reserved.

Temperature-dependent transport and spin accumulation in a quantum wire with Rashba spin-orbit interaction

We study the theory of temperature-dependent electron transport, spin polarization, and spin accumulation in a Rashba spin-orbit interaction (RSOI) quantum wire connected nonadiabatically to two normal conductor electrode leads. The influence of both the wire-lead connection and the RSOI on the electron transport is treated analytically by means of a scattering matrix technique and by using an effective free-electron approximation. Through analytical analysis and numerical examples, we demonstrate a simple way to design a sensitive spin-transfer switch that operates without applying any external magnetic fields or attaching ferromagnetic contacts. We also demonstrate that the antisymmetry of the spin accumulation can be destroyed slightly by the coupling between the leads and the wire. Moreover, temperature can weaken the polarization and smear out the oscillations in the spin accumulation.

Coherence loss and recovery of an electron spin coupled inhomogeneously to a one-dimensional interacting spin bath: An adaptive time-dependent density-matrix renormalization group study

Coherence evolution and echo effect of an electron spin, which is coupled inhomogeneously to an interacting one-dimensional finite spin bath via hyperfine-type interaction, are studied using the adaptive time-dependent density-matrix renormalization group method. It is found that the interplay of the coupling inhomogeneity and the transverse intrabath interactions results in two qualitatively different coherence evolutions, namely, a coherence-preserving evolution characterized by periodic oscillation and a complete decoherence evolution. Correspondingly, the echo effects induced by an electron-spin flip at time tau exhibit stable recoherence pulse sequence for the periodic evolution and a single peak at root 2 tau for the decoherence evolution, respectively. With the diagonal intrabath interaction included, the specific feature of the periodic regime is kept, while the root 2 tau-type echo effect in the decoherence regime is significantly affected. To render the experimental verifications possible, the Hahn echo envelope as a function of tau is calculated, which eliminates the inhomogeneous broadening effect and serves for the identification of the different status of the dynamic coherence evolution, periodic versus decoherence.