The effect of in-plane magnetic field on the spin Hall effect in Rashba-Dresselhaus system

In a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit couplings, there are two spin-split energy surfaces connected with a degenerate point. Both the energy surfaces and the topology of the Fermi surfaces can be varied by an in-plane magnetic field. We find that, if the chemical potential falls between the bottom of the upper band and the degenerate point, then simply by changing the direction of the magnetic field, the magnitude of the spin Hall conductivity can be varied by about 100 percent. Once the chemical potential is above the degenerate point, the spin Hall conductivity becomes the constant $e/8\pi$, independent of the magnitude and direction of the magnetic field. In addition, we find that the in-plane magnetic field exerts no influence on the charge Hall conductivity.Comment: 11 pages, 3 figures, to be published on Phys. Rev.

Matrix Formulation of Hamiltonian Structures of Constrained KP Hierarchy

We give a matrix formulation of the Hamiltonian structures of constrained KP hierarchy. First, we derive from the matrix formulation the Hamiltonian structure of the one-constraint KP hierarchy, which was originally obtained by Oevel and Strampp. We then generalize the derivation to the multi-constraint case and show that the resulting bracket is actually the second Gelfand-Dickey bracket associated with the corresponding Lax operator. The matrix formulation of the Hamiltonian structure of the one-constraint KP hierarchy in the form introduced in the study of matrix model is also discussedComment: 19 pages, Revtex, no figures. Minor changes, reference correcte

Precessionless spin transport wire confined in quasi-two-dimensional electron systems

We demonstrate that in an inversion-asymmetric two-dimensional electron system 2DES with both Rashba and Dresselhaus spin-orbit couplings taken into account, certain transport directions on which no spin precession occurs can be found when the injected spin is properly polarized. By analyzing the expectation value of spin with respect to the injected electron state on each space point in the 2DES, we further show that the adjacent regions with technically reachable widths along these directions exhibit nearly conserved spin. Hence a possible application in semiconductor spintronics, namely, precessionless spin transport wire, is proposed.Comment: 3 pages, 4 figures, to be appeared in Journal of Applied Physics, Proceedings of the 50th MMM Conferenc

Clinical development of liposome-based drugs: formulation, characterization, and therapeutic efficacy

Research on liposome formulations has progressed from that on conventional vesicles to new generation liposomes, such as cationic liposomes, temperature sensitive liposomes, and virosomes, by modulating the formulation techniques and lipid composition. Many research papers focus on the correlation of blood circulation time and drug accumulation in target tissues with physicochemical properties of liposomal formulations, including particle size, membrane lamellarity, surface charge, permeability, encapsulation volume, shelf time, and release rate. This review is mainly to compare the therapeutic effect of current clinically approved liposome-based drugs with free drugs, and to also determine the clinical effect via liposomal variations in lipid composition. Furthermore, the major preclinical and clinical data related to the principal liposomal formulations are also summarized

Protein domain repetition is enriched in Streptococcal cell-surface proteins

AbstractTandem repetition of domain in protein sequence occurs in all three domains of life. It creates protein diversity and adds functional complexity in organisms. In this work, we analyzed 52 streptococcal genomes and found 3748 proteins contained domain repeats. Proteins not harboring domain repeats are significantly enriched in cytoplasm, whereas proteins with domain repeats are significantly enriched in cytoplasmic membrane, cell wall and extracellular locations. Domain repetition occurs most frequently in S. pneumoniae and least in S. thermophilus and S. pyogenes. DUF1542 is the highest repeated domain in a single protein, followed by Rib, CW_binding_1, G5 and HemolysinCabind. 3D structures of 24 repeat-containing proteins were predicted to investigate the structural and functional effect of domain repetition. Several repeat-containing streptococcal cell surface proteins are known to be virulence-associated. Surface-associated tandem domain-containing proteins without experimental functional characterization may be potentially involved in the pathogenesis of streptococci and deserve further investigation

Datta-Das transistor: Significance of channel direction, size-dependence of source contacts, and boundary effects

We analyze the spin expectation values for injected spin-polarized electrons (spin vectors) in a [001]-grown Rashba-Dresselhaus two-dimensional electron gas (2DEG). We generalize the calculation for point spin injection in semi-infinite 2DEGs to finite-size spin injection in bounded 2DEGs. Using the obtained spin vector formula, significance of the channel direction for the Datta-Das transistor is illustrated. Numerical results indicate that the influence due to the finite-size injection is moderate, while the channel boundary reflection may bring unexpected changes. Both effects are concluded to decrease when the spin-orbit coupling strength is strong. Hence [110] is a robust channel direction and is therefore the best candidate for the design of the Datta-Das transistor.Comment: 5 pages, 4 figures, accepted for publication in Physical Review

A role for the Perlman syndrome exonuclease Dis3l2 in the Lin28-let-7 pathway

The pluripotency factor Lin28 blocks the expression of let-7 microRNAs (miRNAs) in undifferentiated cells during development and functions as an oncogene in a subset of cancers1. Lin28 binds to let-7 precursor RNAs and recruits 3′ terminal uridylyl transferases (TUTases) to selectively inhibit let-7 biogenesis2–4. Uridylated pre-let-7 is refractory to processing by Dicer and is rapidly degraded by an unknown ribonuclease5. Here we identify Dis3l2 as the 3′-5′ exonuclease responsible for the decay of uridylated pre-let-7. Biochemical reconstitution assays reveal that 3′ oligouridylation stimulates Dis3l2 activity in vitro, and knockdown of Dis3l2 in mouse embryonic stem cells leads to the stabilization of pre-let-7. Our study establishes 3′ oligouridylation as an RNA decay signal for Dis3l2 and identifies the first physiological RNA substrate of this novel exonuclease that is mutated in the Perlman syndrome of fetal overgrowth and predisposition to Wilms’ tumor6

Local spin density in two-dimensional electron gas with hexagonal boundary

The intrinsic spin-Hall effect in hexagon-shaped samples is investigated. To take into account the spin-orbit couplings and to fit the hexagon edges, we derive the triangular version of the tight-binding model for the linear Rashba [Sov. Phys. Solid State 2, 1109 (1960)] and Dresselhaus [Phys. Rev. 100, 580 (1955)] [001] Hamiltonians, which allow direct application of the Landauer-Keldysh non-equilibrium Green function formalism to calculating the local spin density within the hexagonal sample. Focusing on the out-of-plane component of spin, we obtain the geometry-dependent spin-Hall accumulation patterns, which are sensitive to not only the sample size, the spin-orbit coupling strength, the bias strength, but also the lead configurations. Contrary to the rectangular samples, the accumulation pattern can be very different in our hexagonal samples. Our present work provides a fundamental description of the geometry effect on the intrinsic spin-Hall effect, taking the hexagon as the specific case. Moreover, broken spin-Hall symmetry due to the coexistence of the Rashba and Dresselhaus couplings is also discussed. Upon exchanging the two coupling strengths, the accumulation pattern is reversed, confirming the earlier predicted sign change in spin-Hall conductivity.Comment: 7 pages, 4 figure