297 research outputs found
Triplet Exciton Generation in Bulk-Heterojunction Solar Cells based on Endohedral Fullerenes
Organic bulk-heterojunctions (BHJ) and solar cells containing the trimetallic
nitride endohedral fullerene 1-[3-(2-ethyl)hexoxy
carbonyl]propyl-1-phenyl-Lu3N@C80 (Lu3N@C80-PCBEH) show an open circuit voltage
(VOC) 0.3 V higher than similar devices with [6,6]-phenyl-C[61]-butyric acid
methyl ester (PC61BM). To fully exploit the potential of this acceptor molecule
with respect to the power conversion efficiency (PCE) of solar cells, the short
circuit current (JSC) should be improved to become competitive with the state
of the art solar cells. Here, we address factors influencing the JSC in blends
containing the high voltage absorber Lu3N@C80-PCBEH in view of both
photogeneration but also transport and extraction of charge carriers. We apply
optical, charge carrier extraction, morphology, and spin-sensitive techniques.
In blends containing Lu3N@C80-PCBEH, we found 2 times weaker photoluminescence
quenching, remainders of interchain excitons, and, most remarkably, triplet
excitons formed on the polymer chain, which were absent in the reference
P3HT:PC61BM blends. We show that electron back transfer to the triplet state
along with the lower exciton dissociation yield due to intramolecular charge
transfer in Lu3N@C80-PCBEH are responsible for the reduced photocurrent
Decoupling of Lattice and Orbital Degrees of Freedom in an Iron-Pnictide Superconductor
The interplay of structural and electronic phases in iron-based
superconductors is a central theme in the search for the superconducting
pairing mechanism. While electronic nematicity, defined as the breaking of
four-fold symmetry triggered by electronic degrees of freedom, is competing
with superconductivity, the effect of purely structural orthorhombic order is
unexplored. Here, using x-ray diffraction (XRD), we reveal a new structural
orthorhombic phase with an exceptionally high onset temperature
( K), which coexists with superconductivity
( K), in an electron-doped iron-pnictide superconductor far
from the underdoped region. Furthermore, our angle-resolved photoemission
spectroscopy (ARPES) measurements demonstrate the absence of electronic nematic
order as the driving mechanism, in contrast to other underdoped iron pnictides
where nematicity is commonly found. Our results establish a new, high
temperature phase in the phase diagram of iron-pnictide superconductors and
impose strong constraints for the modeling of their superconducting pairing
mechanism.Comment: SI available upon reques
Redox-Induced Src Kinase and Caveolin-1 Signaling in TGF-β1-Initiated SMAD2/3 Activation and PAI-1 Expression
Plasminogen activator inhibitor-1 (PAI-1), a major regulator of the plasmin-based pericellular proteolytic cascade, is significantly increased in human arterial plaques contributing to vessel fibrosis, arteriosclerosis and thrombosis, particularly in the context of elevated tissue TGF-β1. Identification of molecular events underlying to PAI-1 induction in response to TGF-β1 may yield novel targets for the therapy of cardiovascular disease.Reactive oxygen species are generated within 5 minutes after addition of TGF-β1 to quiescent vascular smooth muscle cells (VSMCs) resulting in pp60(c-src) activation and PAI-1 expression. TGF-β1-stimulated Src kinase signaling sustained the duration (but not the initiation) of SMAD3 phosphorylation in VSMC by reducing the levels of PPM1A, a recently identified C-terminal SMAD2/3 phosphatase, thereby maintaining SMAD2/3 in an active state with retention of PAI-1 transcription. The markedly increased PPM1A levels in triple Src kinase (c-Src, Yes, Fyn)-null fibroblasts are consistent with reductions in both SMAD3 phosphorylation and PAI-1 expression in response to TGF-β1 compared to wild-type cells. Activation of the Rho-ROCK pathway was mediated by Src kinases and required for PAI-1 induction in TGF-β1-stimulated VSMCs. Inhibition of Rho-ROCK signaling blocked the TGF-β1-mediated decrease in nuclear PPM1A content and effectively attenuated PAI-1 expression. TGF-β1-induced PAI-1 expression was undetectable in caveolin-1-null cells, correlating with the reduced Rho-GTP loading and SMAD2/3 phosphorylation evident in TGF-β1-treated caveolin-1-deficient cells relative to their wild-type counterparts. Src kinases, moreover, were critical upstream effectors of caveolin-1(Y14) phosphoryation and initiation of downstream signaling.TGF-β1-initiated Src-dependent caveolin-1(Y14) phosphorylation is a critical event in Rho-ROCK-mediated suppression of nuclear PPM1A levels maintaining, thereby, SMAD2/3-dependent transcription of the PAI-1 gene
SNW1 Is a Critical Regulator of Spatial BMP Activity, Neural Plate Border Formation, and Neural Crest Specification in Vertebrate Embryos
In frog and fish embryos, SNW1 is a protein required for the spatio-temporal activity of BMP signaling necessary for neural plate border formation and specification of neural crest tissue
Probing the Interstellar Medium in Early type galaxies with ISO observations
Four IRAS-detected early type galaxies were observed with ISO. With the
exception of the 15 micron image of NGC1052, the mid-IR emission from NGC1052,
NGC1155, NGC5866 and NGC6958 at 4.5, 7 and 15 microns show extended emission.
Mid-IR emission from NGC1052, NGC1155, and NGC6958 follows a de Vaucouleurs
profile. The ratio of 15/7 micron flux decreases with radius in these galaxies,
approaching the values empirically observed for purely stellar systems. In
NGC5866, the 7 and 15 micron emission is concentrated in the edge-on dust lane.
All the galaxies are detected in the [CII] line, and the S0s NGC1155 and
NGC5866 are detected in the [OI] line as well. The ISO-LWS observations of the
[CII] line are more sensitive measures of cool, neutral ISM than HI and CO by
about a factor of 10-100. Three of four early type galaxies, namely NGC1052,
NGC6958 and NGC5866, have low ratio FIR/Blue and show a lower [CII]/FIR, which
is due to a softer radiation field from old stellar populations. The low
[CII]/CO ratio in NGC5866 ([CII]/CO(1-0) < 570) confirms this scenario. We
estimate the UV radiation expected from the old stellar populations in these
galaxies and compare it to that needed to heat the gas to account for the
cooling observed [CII] and [OI] lines. In three out of four galaxies, NGC1052,
NGC5866 and NGC6958, the predicted UV radiation falls short by a factor of 2-3.
In view of the observed intrinsic scatter in the "UV-upturn" in elliptical
galaxies and its great sensitivity to age and metallicity effects, this is not
significant. However, the much larger difference (about a factor of 20) between
the UV radiation from old stars and that needed to produce the FIR lines for
NGC 1155 is strong evidence for the presence of young stars, in NGC1155.Comment: To appear in the Astrophysical Journal. Figure 1 appears as a
separate jpg figur
Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine
[This corrects the article DOI: 10.1186/s13054-016-1208-6.]
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