325 research outputs found
Superconductivity in La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4) superlattices
Superlattices of the repeated structure La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4)
(LSCO-LCO), where none of the constituents is superconducting, show a
superconducting transition of T_c \simeq 25 K. In order to elucidate the nature
of the superconducting state we have performed a low-energy muSR study. By
applying a magnetic field parallel (Meissner state) and perpendicular (vortex
state) to the film planes, we could show that superconductivity is sheet like,
resulting in a very anisotropic superconducting state. This result is
consistent with a simple charge-transfer model, which takes into account the
layered structure and the difference in the chemical potential between LCO and
LSCO, as well as Sr interdiffusion. Using a pancake-vortex model we could
estimate a strict upper limit of the London penetration depth to 380 nm in
these superlattices. The temperature dependence of the muon depolarization rate
in field cooling experiments is very similar to what is observed in
intercalated BSCCO and suggests that vortex-vortex interaction is dominated by
electromagnetic coupling but negligible Josephson interaction.Comment: 4 pages, 3 figure
Field-induced water electrolysis switches an oxide semiconductor from an insulator to a metal
Here we demonstrate that water-infiltrated nanoporous glass electrically
switches an oxide semiconductor from an insulator to metal. We fabricated the
field effect transistor structure on an oxide semiconductor, SrTiO3, using
100%-water-infiltrated nanoporous glass - amorphous 12CaO*7Al2O3 - as the gate
insulator. For positive gate voltage, electron accumulation, water electrolysis
and electrochemical reduction occur successively on the SrTiO3 surface at room
temperature, leading to the formation of a thin (~3 nm) metal layer with an
extremely high electron concentration of 10^15-10^16 cm^-2, which exhibits
exotic thermoelectric behaviour.Comment: 21 pages, 12 figure
The Justy mutation identifies Gon4-like as a gene that is essential for B lymphopoiesis
A recessive mutation named Justy was found that abolishes B lymphopoiesis but does not impair other major aspects of hematopoiesis. Transplantation experiments showed that homozygosity for Justy prevented hematopoietic progenitors from generating B cells but did not affect the ability of bone marrow stroma to support B lymphopoiesis. In bone marrow from mutant mice, common lymphoid progenitors and pre-pro–B cells appeared normal, but cells at subsequent stages of B lymphopoiesis were dramatically reduced in number. Under culture conditions that promoted B lymphopoiesis, mutant pre-pro–B cells remained alive and began expressing the B cell marker CD19 but failed to proliferate. In contrast, these cells were able to generate myeloid or T/NK precursors. Genetic and molecular analysis demonstrated that Justy is a point mutation within the Gon4-like (Gon4l) gene, which encodes a protein with homology to transcriptional regulators. This mutation was found to disrupt Gon4l pre-mRNA splicing and dramatically reduce expression of wild-type Gon4l RNA and protein. Consistent with a role for Gon4l in transcriptional regulation, the levels of RNA encoding C/EBPα and PU.1 were abnormally high in mutant B cell progenitors. Our findings indicate that the Gon4l protein is required for B lymphopoiesis and may function to regulate gene expression during this process
Ab-initio Low-Energy Model of Transition-Metal-Oxide Heterostructure LaAlO3/SrTiO3
We develop the multi-scale ab-initio scheme for correlated electrons (MACE)
for transitionmetal-oxide heterostructures, and determine the parameters of the
low-energy effective model. By separating Ti t2g bands near the Fermi level
from the global Kohn-Sham (KS) bands of LaAlO3/SrTiO3 which are highly
entangled with each other, we are able to calculate the parameters of the
low-energy effective model of the interface with the help of constrained random
phase approximation (cRPA). The on-site energies of the Ti t2g orbitals in the
1stlayer is about 650 meV lower than those in the 2nd-layer. In the 1st-layer,
the transfer integral of the Ti t2g orbital is nearly the same as that of the
bulk SrTiO3, while the effective screened Coulomb interaction becomes about 10
percent larger than that of the bulk SrTiO3. The differences of the parameters
from the bulk SrTiO3 reduce rapidly with increasing distance from the
interface. Our present versatile method makes it possible to derive effective
ab-initio low-energy models and allows studying interfaces of strongly
correlated electron systems from first principles.Comment: 11 pages, 9 figures, submitted to J. Phys. Soc. Jp
Epitaxial Structure of (001)- and (111)-Oriented Perovskite Ferrate Films Grown by Pulsed-Laser Deposition
Exceptionally high incidence of symptomatic grade 2–5 radiation pneumonitis after stereotactic radiation therapy for lung tumors
<p>Abstract</p> <p>Background</p> <p>To determine the usefulness of dose volume histogram (DVH) factors for predicting the occurrence of radiation pneumonitis (RP) after application of stereotactic radiation therapy (SRT) for lung tumors, DVH factors were measured before irradiation.</p> <p>Methods</p> <p>From May 2004 to April 2006, 25 patients were treated with SRT at the University of Tokyo Hospital. Eighteen patients had primary lung cancer and seven had metastatic lung cancer. SRT was given in 6–7 fields with an isocenter dose of 48 Gy in four fractions over 5–8 days by linear accelerator.</p> <p>Results</p> <p>Seven of the 25 patients suffered from RP of symptomatic grade 2–5 according to the NCI-CTC version 3.0. The overall incidence rate of RP grade2 or more was 29% at 18 months after completing SRT and three patients died from RP. RP occurred at significantly increased frequencies in patients with higher conformity index (CI) (p = 0.0394). Mean lung dose (MLD) showed a significant correlation with V<sub>5</sub>–V<sub>20 </sub>(irradiated lung volume) (p < 0.001) but showed no correlation with CI. RP did not statistically correlate with MLD. MLD had the strongest correlation with V<sub>5</sub>.</p> <p>Conclusion</p> <p>Even in SRT, when large volumes of lung parenchyma are irradiated to such high doses as the minimum dose within planning target volume, the incidence of lung toxicity can become high.</p
Evidence for early life in Earth’s oldest hydrothermal vent precipitates
Although it is not known when or where life on Earth began, some of the earliest habitable environments may have been submarine-hydrothermal vents. Here we describe putative fossilized microorganisms that are at least 3,770 million and possibly 4,280 million years old in ferruginous sedimentary rocks, interpreted as seafloor-hydrothermal vent-related precipitates, from the Nuvvuagittuq belt in Quebec, Canada. These structures occur as micrometre-scale haematite tubes and filaments with morphologies and mineral assemblages similar to those of filamentous microorganisms from modern hydrothermal vent precipitates and analogous microfossils in younger rocks. The Nuvvuagittuq rocks contain isotopically light carbon in carbonate and carbonaceous material, which occurs as graphitic inclusions in diagenetic carbonate rosettes, apatite blades intergrown among carbonate rosettes and magnetite–haematite granules, and is associated with carbonate in direct contact with the putative microfossils. Collectively, these observations are consistent with an oxidized biomass and provide evidence for biological activity in submarine-hydrothermal environments more than 3,770 million years ago
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