3,152 research outputs found
Detection of antiferromagnetic ordering in heavily doped LaFeAsO1-xHx pnictide superconductors using nuclear-magnetic-resonance techniques
We studied double superconducting (SC) domes in LaFeAsO1-xHx by using 75As-
and 1H-nuclear magnetic resonance techniques, and unexpectedly discovered that
a new antiferromagnetic (AF) phase follows the double SC domes on further H
doping, forming a symmetric alignment of AF and SC phases in the electronic
phase diagram. We demonstrated that the new AF ordering originates from the
nesting between electron pockets, unlike the nesting between electron and hole
pockets as seen in the majority of undoped pnictides. The new AF ordering is
derived from the features common to high-Tc pnictides: however, it has not been
reported so far for other high-Tc pnictides because of their poor electron
doping capability.Comment: 5 figures, in press in PR
Edge Current due to Majorana Fermions in Superfluid He A- and B-Phases
We propose a method utilizing edge current to observe Majorana fermions in
the surface Andreev bound state for the superfluid He A- and B-phases. The
proposal is based on self-consistent analytic solutions of quasi-classical
Green's function with an edge. The local density of states and edge mass
current in the A-phase or edge spin current in the B-phase can be obtained from
these solutions. The edge current carried by the Majorana fermions is partially
cancelled by quasiparticles (QPs) in the continuum state outside the superfluid
gap. QPs contributing to the edge current in the continuum state are
distributed in energy even away from the superfluid gap. The effect of Majorana
fermions emerges in the depletion of the edge current by temperature within a
low-temperature range. The observations that the reduction in the mass current
is changed by -power in the A-phase and the reduction in the spin current
is changed by -power in the B-phase establish the existence of Majorana
fermions. We also point out another possibility for observing Majorana fermions
by controlling surface roughness.Comment: 13 pages, 4 figures, published versio
Spin density wave and superconductivity in CaFe_{1-x}Co_{x}AsF studied by nuclear magnetic resonance
We performed nuclear magnetic resonance (NMR) measurements to investigate the
evolution of spin-density-wave (SDW) and superconducting (SC) states upon
electron doping in CaFe_{1-x}Co_{x}AsF, which exhibits an intermediate phase
diagram between those of LaFeAsO_{1-x}F_x and Ba(Fe_{1-x}Co_x)_2As_2. We found
that homogeneous coexistence of the incommensurate SDW and SC states occurs
only in a narrow doping region around the crossover regime, which supports
S_{+-}-wave symmetry. However, only the structural phase transition survives
upon further doping, which agrees with predictions from orbital fluctuation
theory. The transitional features upon electron doping imply that both spin and
orbital fluctuations are involved in the superconducting mechanism
Homogeneous coexistence of SDW and SC states in CaFe(1-x)Co(x)AsF studied by nuclear magnetic resonance
We investigated the homogeneous coexistence of spin-density-wave (SDW) and
superconducting (SC) states via 75As-nuclear magnetic resonance (NMR) in
CaFe(1-x)Co(x)AsF and found that the electronic and magnetic properties of this
compound are intermediate between those of LaFeAsO(1-x)F(x) and
Ba(Fe(1-x)Co(x))2As2. For 6% Co-doped samples, the paramagnetic spectral weight
completely disappears in the crossover regime between the SDW and SC phases
followed by the anomalous behavior of relaxation rate (1/T1), implying that the
two phases are not segregated. The 59Co-NMR spectra show that spin moments are
not commensurate but spatially modulated. These experimental results suggest
that incommensurate SDW (IC-SDW) and SC states are compatible in this compound.Comment: 5 pages, 4 figure
Next-generation sequencing for endocrine cancers : Recent advances and challenges
Contemporary molecular biology research tools have enriched numerous areas of biomedical research that address challenging diseases, including endocrine cancers (pituitary, thyroid, parathyroid, adrenal, testicular, ovarian, and neuroendocrine cancers). These tools have placed several intriguing clues before the scientific community. Endocrine cancers pose a major challenge in health care and research despite considerable attempts by researchers to understand their etiology. Microarray analyses have provided gene signatures from many cells, tissues, and organs that can differentiate healthy states from diseased ones, and even show patterns that correlate with stages of a disease. Microarray data can also elucidate the responses of endocrine tumors to therapeutic treatments. The rapid progress in next-generation sequencing methods has overcome many of the initial challenges of these technologies, and their advantages over microarray techniques have enabled them to emerge as valuable aids for clinical research applications (prognosis, identification of drug targets, etc.). A comprehensive review describing the recent advances in next-generation sequencing methods and their application in the evaluation of endocrine and endocrine-related cancers is lacking. The main purpose of this review is to illustrate the concepts that collectively constitute our current view of the possibilities offered by next-generation sequencing technological platforms, challenges to relevant applications, and perspectives on the future of clinical genetic testing of patients with endocrine tumors. We focus on recent discoveries in the use of next-generation sequencing methods for clinical diagnosis of endocrine tumors in patients and conclude with a discussion on persisting challenges and future objectives
Functions of sensor 1 and sensor 2 regions of Saccharomyces cerevisiae Cdc6p in vivo and in vitro
Cdc6p is a key regulator of the cell cycle in eukaryotes and is a member of the AAA(+) (ATPases associated with a variety of cellular activities) family of proteins. In this family of proteins, the sensor 1 and sensor 2 regions are important for their function and ATPase activity. Here, site-directed mutagenesis has been used to examine the role of these regions of Saccharomyces cerevisiae Cdc6p in controlling the cell cycle progression and initiation of DNA replication. Two important amino acid residues (Asn(263) in sensor 1 and Arg(332) in sensor 2) were identified as key residues for Cdc6p function in vivo. Cells expressing mutant Cdc6p (N263A or R332E) grew slowly and accumulated in the S phase. In cells expressing mutant Cdc6p, loading of the minichromosome maintenance (MCM) complex of proteins was decreased, suggesting that the slow progression of S phase in these cells was due to inefficient MCM loading on chromatin. Purified wild type Cdc6p but not mutant Cdc6p (N263A and R332E) caused the structural modification of origin recognition complex proteins. These results are consistent with the idea that Cdc6p uses its ATPase activity to change the conformation of origin recognition complex, and then together they recruit the MCM complex
Evidence for time-reversal symmetry breaking of the superconducting state near twin-boundary interfaces in FeSe
Junctions and interfaces consisting of unconventional superconductors provide
an excellent experimental playground to study exotic phenomena related to the
phase of the order parameter. Not only the complex structure of unconventional
order parameters have an impact on the Josephson effects, but also may
profoundly alter the quasi-particle excitation spectrum near a junction. Here,
by using spectroscopic-imaging scanning tunneling microscopy, we visualize the
spatial evolution of the local density of states (LDOS) near twin boundaries
(TBs) of the nodal superconductor FeSe. The rotation of the
crystallographic orientation across the TB twists the structure of the
unconventional order parameter, which may, in principle, bring about a
zero-energy LDOS peak at the TB. The LDOS at the TB observed in our study, in
contrast, does not exhibit any signature of a zero-energy peak and an apparent
gap amplitude remains finite all the way across the TB. The low-energy
quasiparticle excitations associated with the gap nodes are affected by the TB
over a distance more than an order of magnitude larger than the coherence
length . The modification of the low-energy states is even more
prominent in the region between two neighboring TBs separated by a distance
. In this region the spectral weight near the Fermi level
(0.2~meV) due to the nodal quasiparticle spectrum is almost
completely removed. These behaviors suggest that the TB induces a fully-gapped
state, invoking a possible twist of the order parameter structure which breaks
time-reversal symmetry.Comment: 12 pages, 6 figure
Imaging Simulations of the Sunyaev-Zel'dovich Effect for ALMA
We present imaging simulations of the Sunyaev-Zel'dovich effect of galaxy
clusters for the Atacama Large Millimeter/submillimeter Array (ALMA) including
the Atacama Compact Array (ACA). In its most compact configuration at 90GHz,
ALMA will resolve the intracluster medium with an effective angular resolution
of 5 arcsec. It will provide a unique probe of shock fronts and relativistic
electrons produced during cluster mergers at high redshifts, that are hard to
spatially resolve by current and near-future X-ray detectors. Quality of image
reconstruction is poor with the 12m array alone but improved significantly by
adding ACA; expected sensitivity of the 12m array based on the thermal noise is
not valid for the Sunyaev-Zel'dovich effect mapping unless accompanied by an
ACA observation of at least equal duration. The observations above 100 GHz will
become excessively time-consuming owing to the narrower beam size and the
higher system temperature. On the other hand, significant improvement of the
observing efficiency is expected once Band 1 is implemented in the future.Comment: 16 pages, 12 figures. Accepted for publication in PASJ. Note added in
proof is include
The Sunyaev-Zel'dovich Effect at Five Arc-seconds: RXJ1347.5-1145 Imaged by ALMA
We present the first image of the thermal Sunyaev-Zel'dovich effect (SZE)
obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combining
7-m and 12-m arrays in Band 3, we create an SZE map toward a galaxy cluster
RXJ1347.5-1145 with 5 arc-second resolution (corresponding to the physical size
of 20 kpc/h), the highest angular and physical spatial resolutions achieved to
date for imaging the SZE, while retaining extended signals out to 40
arc-seconds. The 1-sigma statistical sensitivity of the image is 0.017 mJy/beam
or 0.12 mK_CMB at the 5 arc-second full width at half maximum. The SZE image
shows a good agreement with an electron pressure map reconstructed
independently from the X-ray data and offers a new probe of the small-scale
structure of the intracluster medium. Our results demonstrate that ALMA is a
powerful instrument for imaging the SZE in compact galaxy clusters with
unprecedented angular resolution and sensitivity. As the first report on the
detection of the SZE by ALMA, we present detailed analysis procedures including
corrections for the missing flux, to provide guiding methods for analyzing and
interpreting future SZE images by ALMA.Comment: 20 pages, 13 figures. Accepted for publication in PAS
- …