Unconventional anisotropic s-wave superconducting gaps of the LiFeAs iron-pnictide superconductor

We have performed high-resolution angle-resolved photoemission spectroscopy on Fe-based superconductor LiFeAs (T(c)=18 K). We reveal multiple nodeless superconducting (SC) gaps with 2Δ/k(B)T(c) ratios varying from 2.8 to 6.4, depending on the Fermi surface (FS). We also succeeded in directly observing a gap anisotropy along the FS with magnitude up to ~30%. The anisotropy is fourfold symmetric with an antiphase between the hole and electron FSs, suggesting complex anisotropic interactions for the SC pairing. The observed momentum dependence of the SC gap offers an excellent opportunity to investigate the underlying pairing mechanism.

Single spin asymmetries in charged pion production from semi-inclusive deep inelastic scattering on a transversely polarized 3He Target at Q2 = 1.4-2.7 GeV2

We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations.

Transforming growth factor-β1 polymorphisms and chronic obstructive pulmonary disease: a meta-analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a complex polygenic disease in which gene- environment interactions play a critical role in disease onset and progression. Transforming growth factor-β 1 (TGF-β 1) is one of several candidate loci for the pathogenesis of COPD, and is highly polymorphic.

OBJECTIVE

To derive a more precise estimation of the relationship between the T869C and C-509T polymorphisms of the TGF-β 1 gene and COPD, a meta-analysis of 11 published case-control studies was performed.

METHODS

Ten studies with 1507 cases and 2542 controls for T869C polymorphism and six studies with 955 cases and 2136 controls for C-509T polymorphism were included. The pooled odds ratios were performed respectively for allele contrasts, additive genetic model, dominant genetic model and recessive genetic model. A subgroup analysis was also performed by ethnicity for T869C polymorphism.

RESULTS

With respect to T869C polymorphism, a significant association of TGF-β 1 gene polymorphism at 869T/C with COPD was observed in the overall analysis (C vs. T: OR 0.82, 95%CI 0.70-0.96, P = 0.01). In the subgroup analysis by ethnicity, significant risks were also found in the Caucasian population for C vs. T (OR 0.77, 95%CI 0.60-0.98, P = 0.03), but not in the Asian population (C vs. T: OR 0.88, 95%CI 0.76-1.03, P = 0.10). With respect to C-509T polymorphism, no significant association with COPD was demonstrated in the overall analysis (T vs. C: OR 0.84, 95%CI 0.68- 1.04, P = 0.11).

CONCLUSION

Potentially functional TGF-β 1 T869C polymorphism may play a low penetrance role in COPD susceptibility in an ethnicity-specific manner.

Circulating microRNAs in hepatitis B virus-infected patients

MicroRNAs (miRNAs) are stably present in human serum. The relationship between circulating miRNAs and hepatitis B virus (HBV) infected liver disease has not been previously reported. Applied Biosystems array-based miRNA expression profiling was performed on pooled sera obtained from identified groups of chronic asymptomatic carriers (ASC), patients with chronic hepatitis B (CHB) and HBV-associated acute-on-chronic liver failure (ACLF), as well as healthy controls (HC). Nine miRNAs were verified in more clinical samples by RT-PCR. The correlation between miRNAs expression and the relationship between miRNA levels and clinical characteristics was analysed. Results showed that circulating miRNAs were detected in all disease and control samples, and their numbers increased with symptom severity, from 37 in HC, 77 in ASC, 101 in CHB, to 135 in ACLF. The expression levels of most miRNAs were also up-regulated in HBV-infected patients when compared to HC. Expression of the liver-specific miR-122 was significantly up-regulated in HBV-infected patients. Concomitant regulation of miRNAs not in clusters was disrupted by HBV infection. However, such disruption was not observed for miRNAs in paralogous clusters. Furthermore, the level of miRNAs in the CHB serum was up-regulated most in hepatitis B e antigen-positive patients. The expression levels of miR-122 and miR-194 correlated negatively with the age of patients with CHB or ACLF. Functional analysis showed that miR-122 could inhibit HBV replication in Huh7 and HepG2 cells. In all, our study revealed that a number of miRNAs were differentially expressed during HBV infection and underscored the potential importance of miR-122 in the infection process.

Direct observation of broken time-reversal symmetry on the surface of a magnetically doped topological insulator

We study interference patterns of a magnetically doped topological insulator Bi(2-x)Fe(x)Te(3+d) by using Fourier transform scanning tunneling spectroscopy and observe several new scattering channels. A comparison with angle-resolved photoemission spectroscopy allows us to unambiguously ascertain the momentum-space origin of distinct dispersing channels along high-symmetry directions and identify those originating from time-reversal symmetry breaking. Our analysis also reveals that the surface state survives far above the energy where angle-resolved photoemission spectroscopy finds the onset of continuum bulk bands.

Absence of a holelike fermi surface for the iron-based K0.8F1.7Se2 superconductor revealed by angle-resolved photoemission spectroscopy

We have performed an angle-resolved photoemission spectroscopy study of the new iron-based superconductor K(0.8)Fe(1.7)Se(2) (T(c)∼30 K). Clear band dispersion is observed with the overall bandwidth renormalized by a factor of 2.5 compared to our local density approximation calculations, indicating relatively strong correlation effects. Only an electronlike band crosses the Fermi energy, forming a nearly circular Fermi surface (FS) at M (π, 0). The holelike band at Γ sinks ∼90 meV below the Fermi energy, with an indirect band gap of 30 meV, to the bottom of the electronlike band. The observed FS topology in this superconductor favors (π, π) inter-FS scattering between the electronlike FSs at the M points, in sharp contrast to other iron-based superconductors which favor (π, 0) inter-FS scattering between holelike and electronlike FSs.

Electronic structure of optimally doped pnictide Ba0.6K0.4Fe2As2: a comprehensive angle-resolved photoemission spectroscopy investigation

The electronic structure of the Fe-based superconductor Ba(0.6)K(0.4)Fe(2)As(2) is studied by means of angle-resolved photoemission. We identify dispersive bands crossing the Fermi level forming hole-like (electron-like) Fermi surfaces (FSs) around Γ (M) with nearly nested FS pockets connected by the antiferromagnetic wavevector. Compared to band structure calculation findings, the overall bandwidth is reduced by a factor of 2 and the low energy dispersions display even stronger mass renormalization. Using an effective tight banding model, we fitted the band structure and the FSs to obtain band parameters reliable for theoretical modeling and calculation of physical quantities.

A precise method for visualizing dispersive features in image plots

In order to improve the advantages and the reliability of the second derivative method in tracking the position of extrema from experimental curves, we develop a novel analysis method based on the mathematical concept of curvature. We derive the formulas for the curvature in one and two dimensions and demonstrate their applicability to simulated and experimental angle-resolved photoemission spectroscopy data. As compared to the second derivative, our new method improves the localization of the extrema and reduces the peak broadness for a better visualization on intensity image plots.

Significance and relationship between DJ-1 gene and surviving gene expression in laryngeal carcinoma

This study aimed at exploring the correlation between DJ-1 gene and survivin gene in laryngeal squamous cell carcinoma by analyzing their gene expression levels and their relationship with clinicopathologic parameters. The expression of DJ-1 gene and survivin gene in 82 laryngeal carcinoma tissues from patients and 82 negative surgical margin tissue samples were detected by immunohistochemistry, respectively. The correlation of their expression levels and patients' clinical parameters were then analyzed by Pearson correlation analysis. The positive detection rates of DJ-1 and survivin in laryngeal carcinoma tissues were 71.95% and 60.98%, which were higher than those of the normal control that were 29.27% and 0.00%, respectively (P<0.01). The positive detection rates of DJ-1 and survivin were found associated with tumor stages (P<0.05), but not with lymph node metastasis. The DJ-1 gene expression level was related to cell differentiation (P<0.05). Finally, a positive correlation between DJ-1 and survivin gene expression in laryngeal carcinoma was found. The overall survival rate of patients was 51.2%, and disease-free survival (DFS) was 39.0%. DFS in DJ-1 negative-expression group was 87.0%, and 20.3% in DJ-1 positive-expression group. The negative expression of DJ-1 was associated with a shorter mean patient DFS time (44.643±1.417 months), whereas positive expression of DJ-1 was associated with a longer mean DSF time (25.943±;1.297 months). DJ-1 and survivin play a vital role in the occurrence and development of laryngeal carcinoma. DJ-1 may promote the carcinogenesis of laryngeal cells by up-regulating the survivin gene expression.

Angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3: strong coupling behavior and the universality of interband scattering

We have performed angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3 to investigate the electronic structure relevant to superconductivity. We observed a holelike Fermi surface (FS) and an electronlike FS at the Brillouin zone center and corner, respectively, which are nearly nested by the Q∼(π,π) wave vector. We do not find evidence for the nesting instability with Q∼(π+δ,0) reminiscent of the antiferromagnetic order in the parent compound Fe1+yTe. We have observed an isotropic superconducting (SC) gap along the holelike FS with the gap size Δ of ∼4 meV (2Δ/kBTc ∼ 7), demonstrating the strong-coupling superconductivity. The observed similarity of low-energy electronic excitations between iron-chalcogenides and iron-arsenides strongly suggests that common interactions which involve Q∼(π,π) scattering are responsible for the SC pairing.