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Electron transport properties in a triple-quantum-dot ring with three terminals are theoretically studied. By introducing local Rashba spin-orbit interaction on an individual quantum dot, we calculate the charge and spin currents in one lead. We find that a pure spin current appears in the absence of a magnetic field. The polarization direction of the spin current can be inverted by altering the bias voltage. In addition, by tuning the magnetic field strength, the charge and spin currents reach their respective peaks alternately.PACS numbers: 73.63. Kv, 71.70.Ej, One of the central issue in spintronics is how to realize the spin accumulation and spin transport in nanodevices. Recently, there has been many theoretical proposals to achieve the pure spin current without an accompanying charge current in mesoscopic systems, such as the use of spin Hall effects, 1,2 optical spin orientation by linearly polarized light, 3,4 adiabatic or nonadiabatic spin pumping in metals and semiconductors,generation in three-terminal spin devices. 7 Among these schemes, spin-orbit(SO) coupling is exploited to influences the electron spin state. In particular, in low-dimensional structures Rashba SO interaction comes into play by introducing an electric potential to destroy the symmetry of space inversion in an arbitrary spatial direction.8,9 Thus, by virtue of the Rashba interaction, electric control and manipulation of the electronic spin state is feasible. 10,11,12,13,14 In this Letter, we introduce Rashba interaction to act locally on one component quantum dot(QD) of a triple-QD ring with three terminals. Our theoretical investigation indicates that it is possible to form the pure spin current in one of the three leads even in the absence of a magnetic field. And the polarization direction of the spin current can be inverted by altering the bias voltage.The structure that we consider is illustrated in Fig.1. The single-particle Hamiltonian for an electron in such a structure can be written as H s = H 0 + H so = P 2 2m * + V (r) + H so where, accompanying the kinetic energy term P 2 2m * , the electron confined potential V (r) defines the structure geometry; And H so = y 2 · [α(σ × p) + (σ × p)α] denotes the local Rashba SO coupling on QD-2 (QD-j represents the QD with a single-particle level ε j shown in Fig.1(a)). We select the basis set {ψ kj χ σ , ψ j χ σ }(j=1,2,3) to second-quantize the Hamiltonian. The wavefunctions ψ j and ψ kj have the physical meaning of the orbital eigenstates of the isolated QD and leads, in the absence of Rashba interaction, where k j indicates the continuum state in lead-j. χ σ with σ =↑, ↓ denotes the eigenstates of Pauli spin operatorσ z .The second-quantized Hamiltonian consists of three parts:where c † kj σ and d † jσ (c kj σ and d jσ ) are the creation (annihilation) operators corresponding to the basis states in lead-j and QD-j. ε kj is the single-particle level in lead-j. V jσ = ψ j χ σ |H s |ψ kj χ σ denotes QDlead hopping amplitude. The interdot hopping amplitude, written as t lσ = t l − iσs...

Electron transport through the T-shaped quantum-dot (QD) structure is theoretically investigated, by considering a Majorana zero mode coupled to the terminal QD. It is found that in the double-QD case, the presence of the Majorana zero mode can efficiently dissolve the antiresonance point in the conductance spectrum and induce a conductance peak to appear at the same energy position whose value is equal to e 2 /2h. This antiresonance-resonance change will be suitable to detect the Majorana bound states. Next in the multi-QD case, we observe that in the zero-bias limit, the conductances are always the same as the double-QD result, independent of the parity of the QD number. We believe that all these results can be helpful for understanding the properties of Majorana bound states.

BackgroundNatural hybridization in plants is universal and plays an important role in evolution. Based on morphology it has been presumed that hybridization occurred in the genus Buddleja, though genetic studies confirming this assumption have not been conducted to date. The two species B. crispa and B. officinalis overlap in their distributions over a wide range in South-West China, and we aimed to provide genetic evidence for ongoing hybridization in this study.ResultsWe investigated the occurrence of hybrids between the two species at the southern-most edge of the distribution of B. crispa using five nuclear loci and pollination experiments. The genetic data suggest substantial differentiation between the two species as species-specific alleles are separated by at least 7–28 mutations. The natural hybrids found were nearly all F1s (21 of 23), but backcrosses were detected, and some individuals, morphologically indistinguishable from the parental species, showed introgression. Pollen viability test shows that the percentage of viable pollen grains was 50 ± 4 % for B. crispa, and 81 ± 2 % for B. officinalis. This difference is highly significant (t = 7.382, p < 0.0001). Hand cross-pollination experiments showed that B. crispa is not successful as pollen-parent, but B. officinalis is able to pollinate B. crispa to produce viable hybrid seed. Inter-specific seed-set is low (8 seeds per fruit, as opposed to about 65 for intra-specific pollinations), suggesting post-zygotic reproductive barriers. In addition, one of the reference populations also suggests a history of introgression at other localities.ConclusionsThe occurrence of morphologically intermediate individuals between B. crispa and B. officinalis at Xishan Mountain is unequivocally linked to hybridization and almost all examined individuals of the putative hybrids were likely F1s. Despite pollination experiments indicating higher chances for introgression into B. officinalis (hybrids only produced viable seed when crossed with B. officinalis), observed introgression was asymmetrical into B. crispa. This could be due to seeds produced by hybrids not contributing to seedlings, or other factors favoring the establishment of backcrosses towards B. crispa. However, further research will be needed to confirm these observations, as the small number of plants used for the pollination experiments could have introduced an artifact, for example if used individuals were more or less compatible than the species average, and also the small number of loci used could convey a picture of introgression that is not representative for the whole genome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0539-9) contains supplementary material, which is available to authorized users.

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Efficient peptide and protein identifications from data-independent acquisition mass spectrometric (DIA-MS) data typically rely on a project-specific spectral library with a suitable size. Here, we describe subLib, a computational strategy for optimizing the spectral library for a specific DIA data set based on a comprehensive spectral library, requiring the preliminary analysis of the DIA data set. Compared with the pan-human library strategy, subLib achieved a 41.2% increase in peptide precursor identifications and a 35.6% increase in protein group identifications in a test data set of six colorectal tumor samples. We also applied this strategy to 389 carcinoma samples from 15 tumor data sets: up to a 39.2% increase in peptide precursor identifications and a 19.0% increase in protein group identifications were observed. Our strategy for spectral library size optimization thus successfully proved to deepen the proteome coverages of DIA-MS data.

For a quantum dot ͑QD͒ in the Kondo regime, we introduce a side QD attached to one of the two leads to mimic an Anderson impurity in the conduction electron reservoir. Then, we study the peculiar Kondo effect in such a double QD structure. We find that the Kondo peak in the local density of states in the QDs exhibits a notable deviation from the Lorentzian line shape. More importantly, the expected Kondo peak in the linear conductance turns into zero when a Kondo level or a single-particle level of the side QD is aligned with the Fermi level. This result indicates that the presence of an Anderson impurity in the leads can quench the electron transport through the central QD. The underlying mechanism to cause this behavior is ascribed to quantum interference, which is clearly described in the language of Feynman paths.

Background SLC7A7 (solute carrier family 7, amino acid transporter light chain, y + L system, member 7) is a critical gene in the regulation of cationic amino acid transport. However, the relationships between SLC7A7 and prognosis and tumor-infiltrating lymphocytes in different cancers remain unclear. Methods SLC7A7 expression was analyzed using the Oncomine database and Tumor Immune Estimation Resource (TIMER) site. The enrichment of the GO (Gene Oncology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways was conducted by DAVID. We evaluated the influence of SLC7A7 on clinical prognosis using the PrognoScan database. The functional state of SLC7A7 in various types of cancers was analyzed by CancerSEA. The relationships between SLC7A7 and cancer immune infiltrates was investigated by TIMER. Furthermore, correlations between SLC7A7 expression and gene marker sets of immune infiltrates were analyzed by TIMER and Gene Expression Profiling Interactive Analysis (GEPIA). The expression of SLC7A7 was verified by GEO database and immunohistochemistry. Results A lung cancer cohort study (GSE31210) showed that high SLC7A7 expression was associated with poor overall survival (OS) and relapse-free survival (RFS). In addition, SLC7A7 had a significant impact on the prognosis of diverse cancers. SLC7A7 expression was positively correlated with infiltrating levels of CD4 + and CD8 + T cells, macrophages, neutrophils and dendritic cells (DCs) in non-small cell lung cancer (NSCLC). SLC7A7 expression was also strongly correlated with various immune marker sets in NSCLC. Conclusions These results indicated a role for SLC7A7 in infiltration of CD8 + T cells, CD4 + T cells, tumor-associated macrophages (TAMs), neutrophils and DCs in multiple cancers, and regulation of T cell exhaustion and Tregs in NSCLC. These findings suggest that SLC7A7 could be served as a biomarker for prognosis and immune infiltration in NSCLC.