3,215 research outputs found
Gene Expression Profile Changes After Short-activating RNA-mediated Induction of Endogenous Pluripotency Factors in Human Mesenchymal Stem Cells
It is now recognized that small noncoding RNA sequences have the ability to mediate transcriptional activation of specific target genes in human cells. Using bioinformatics analysis and functional screening, we screened short-activating RNA (saRNA) oligonucleotides designed to target the promoter regions of the pluripotency reprogramming factors, Kruppel-like factor 4 (KLF4) and c-MYC. We identified KLF4 and c-MYC promoter-targeted saRNA sequences that consistently induced increases in their respective levels of nascent mRNA and protein expression in a time- and dose-dependent manner, as compared with scrambled sequence control oligonucleotides. The functional consequences of saRNA-induced activation of each targeted reprogramming factor were then characterized by comprehensively profiling changes in gene expression by microarray analysis, which revealed significant increases in mRNA levels of their respective downstream pathway genes. Notably, the microarray profile after saRNA-mediated induction of endogenous KLF4 and c-MYC showed similar gene expression patterns for stem cell- and cell cycle-related genes as compared with lentiviral vector-mediated overexpression of exogenous KLF4 and c-MYC transgenes, while divergent gene expression patterns common to viral vector-mediated transgene delivery were also noted. The use of promoter-targeted saRNAs for the activation of pluripotency reprogramming factors could have broad implications for stem cell research
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
Coexistence of orbital and quantum critical magnetoresistance in FeSeS
The recent discovery of a non-magnetic nematic quantum critical point (QCP)
in the iron chalcogenide family FeSeS has raised the prospect of
investigating, in isolation, the role of nematicity on the electronic
properties of correlated metals. Here we report a detailed study of the normal
state transverse magnetoresistance (MR) in FeSeS for a series of
S concentrations spanning the nematic QCP. For all temperatures and
\textit{x}-values studied, the MR can be decomposed into two distinct
components: one that varies quadratically in magnetic field strength
and one that follows precisely the quadrature scaling form
recently reported in metals at or close to a QCP and characterized by a
\textit{H}-linear MR over an extended field range. The two components evolve
systematically with both temperature and S-substitution in a manner that is
determined by their proximity to the nematic QCP. This study thus reveals
unambiguously the coexistence of two independent charge sectors in a quantum
critical system. Moreover, the quantum critical component of the MR is found to
be less sensitive to disorder than the quadratic (orbital) MR, suggesting that
detection of the latter in previous MR studies of metals near a QCP may have
been obscured.Comment: 19 pages (including Supplemental Material), 12 figure
Composition of primary cosmic rays at energies 10(15) to approximately 10(16) eV
The sigma epsilon gamma spectrum in 1 approx. 5 x 1000 TV observed at Mt. Fuji suggests that the flux of primary protons 10 to the 15 approx 10th eV is lower by a factor of 2 approx. 3 than a simple extrapolation from lower energies; the integral proton spectrum tends to be steeper than around to the power V and the spectral index tends to be steeper than Epsilon to the -17th power around 10 to the 14th power eV and the spectral index becomes approx. 2.0 around 10 to the 15th power eV. If the total flux of primary particles has no steepening up to approx 10 to the 15th power eV, than the fraction of primary protons to the total flux should be approx 20% in contrast to approx 45% at lower energies
High energy gamma-rays and hadrons at Mount Fuji
The energy spectra of high energy gamma-rays and hadrons were obtained by the emulsion chamber with 40 c.u. thickness at Mt. Fuji (3750 m). These results are compared with the Monte Carlo calculation based on the same model which is used in a family analysis. Our data are compatible with the model of heavy-enriched primary and scaling in the fragmentation region
Particle interactions at energies over 1000 TeV inferred from gamma-families observed at Mount Fuji
Scaling, mean P sub t, high P sub t jets and others at energies over 1000 TeV are discussed on the basis of gamma-family data with sigma E sub gamma 100 TeV, observed at Mt. Fuji (3750 m). These quantities were examined in connection with the primary composition
Line nodes in the energy gap of high-temperature superconducting BaFe_2(As_{1-x}P_x)_2 from penetration depth and thermal conductivity measurements
We report magnetic penetration depth and thermal conductivity data for
high-quality single crystals of BaFe(AsP) (\,K)
which provide strong evidence that this material has line nodes in its energy
gap. This is distinctly different from the nodeless gap found for
(Ba,K)FeAs which has similar and phase diagram. Our results
indicate that repulsive electronic interactions play an essential role for
Fe-based high- superconductivity but that uniquely there are distinctly
different pairing states, with and without nodes, which have comparable .Comment: 4 pages, 3 figures, revised version to be published in Phys. Rev. B
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