Ultrafast nematic-orbital excitation in FeSe.

The electronic nematic phase is an unconventional state of matter that spontaneously breaks the rotational symmetry of electrons. In iron-pnictides/chalcogenides and cuprates, the nematic ordering and fluctuations have been suggested to have as-yet-unconfirmed roles in superconductivity. However, most studies have been conducted in thermal equilibrium, where the dynamical property and excitation can be masked by the coupling with the lattice. Here we use femtosecond optical pulse to perturb the electronic nematic order in FeSe. Through time-, energy-, momentum- and orbital-resolved photo-emission spectroscopy, we detect the ultrafast dynamics of electronic nematicity. In the strong-excitation regime, through the observation of Fermi surface anisotropy, we find a quick disappearance of the nematicity followed by a heavily-damped oscillation. This short-life nematicity oscillation is seemingly related to the imbalance of Fe 3dxz and dyz orbitals. These phenomena show critical behavior as a function of pump fluence. Our real-time observations reveal the nature of the electronic nematic excitation instantly decoupled from the underlying lattice.

Octet-line node structure of superconducting order parameter in KFe2As2.

In iron-pnictide superconductivity, the interband interaction between the hole and electron Fermi surfaces (FSs) is believed to play an important role. However, KFe(2)As(2) has three zone-centered hole FSs and no electron FS but still exhibits superconductivity. Our ultrahigh-resolution laser angle-resolved photoemission spectroscopy unveils that KFe(2)As(2) is a nodal s-wave superconductor with highly unusual FS-selective multi-gap structure: a nodeless gap on the inner FS, an unconventional gap with "octet-line nodes" on the middle FS, and an almost-zero gap on the outer FS. This gap structure may arise from the frustration between competing pairing interactions on the hole FSs causing the eightfold sign reversal. Our results suggest that the A(1g) superconducting symmetry is universal in iron-pnictides, in spite of the variety of gap functions.

Re-evaluation of the culture condition of polymorphonuclear cells for the study of apoptosis induction.

The culture conditions of human peripheral blood polymorphonuclear leukocytes (PMN) in the study of apoptosis induction were re-evaluated. The changes in the relative viable cell number of PMNs after tumor necrosis factor (TNF) treatment were colorimetrically investigated using a cell counting kit. The relative potency of PMNs to produce the superoxide anion (O2-) was measured as the reduction of color intensity by addition of superoxide dismutase (SOD). When the PMNs were cultured in conventional RPMI1640 medium supplemented with 10% fetal bovine serum (FBS), the stimulation effect of TNF on O2- generation by PMNs was observed only for the first 6 hours. When FBS was replaced with human serum, the effect of TNF was maintained for longer incubation periods. Prolonged incubation of PMNs spontaneously produced large DNA fragments, and the extent of DNA fragmentation was relatively smaller in human serum-containing medium. TNF, LPS, hyperthermia or potassium thiocyanate slightly accelerated the production of large DNA fragments, as well as the induction of trace amounts of internucleosomal DNA cleavage in PMNs, which became detectable only after concentration by fractional isopropanol precipitation. The present study suggests the importance of the use of human serum rather than conventional FBS for the study of apoptosis induction in PMNs.

ERC-55, a binding protein for the papilloma virus E6 oncoprotein, specifically interacts with vitamin D receptor among nuclear receptors.

VDR regulates gene expression in a ligand-dependent way by binding to cognate enhancer elements of target gene promoters. The ligand-dependent activation function, AF-2, of VDR is thought to require transcriptional co-activators/co-repressors together with basal transcriptional machinery. Using a yeast two hybrid system with VDR, we have isolated a mouse Ca(2+)-binding protein (designated as VAF1) specifically interacting in vivo and in vitro with VDR among nuclear receptors like RAR, RXR, ER and GR. VAF1 is a mouse homologue to human ERC-55, which has recently been shown to interact with human papillomavirus oncogenic protein, E6[1]. Unlike those of many previously identified co-activators, the VDR-VAF1 interaction was ligand-independent. Thus, VAF1 seems a putative VDR-specific cofactor modulating its function.