The 1144 phase (Ae 1 A 1 Fe 4 As 4 ) shows a strong advantage of engineering fabrication among Fe (Iron)-based superconductor (FBS) family due to the robustness of its superconducting properties with ...respect to chemical inhomogeneities, granted by its stoichiometric nature. This regularity is furthermore associated to defects capable of acting as efficient pinning centers with high critical currents achieved at high fields for these superconductors. Like other FBS phases, its lossless current-carrying capability can be remarkably degraded by distractions at grain boundaries (GBs). GB oxidation is an issue of upmost importance to the realization of the practical FBS application for high field (>20 T) magnet. In this study, we explore oxidized grain boundary and intrinsic grain structural properties of 1144 polycrystalline samples by applying analytical electron microscopy such as atomic resolution scanning transmission electron microscopy and atom probe tomography. These structural properties of 1144 samples are evaluated following the degradation of superconducting properties due to oxidation. We observe a strong correlation between the contamination at grain boundaries and the decrease of transport properties of the bulk sample, while the bulk crystalline structure is not affected by the oxidation. crystalline
Cell-permeable peptides (CPPs) promote the transduction of nonpermissive cells by recombinant adenovirus (rAd) to improve the therapeutic efficacy of rAd. In this study, branched oligomerization of ...CPPs significantly enhanced the transduction of human mesenchymal stem cells (MSCs) by rAd in a CPP type-independent manner. In particular, tetrameric CPPs increased transduction efficiency at 3000-5000-fold lower concentrations than did monomeric CPPs. Although branched oligomerization of CPPs also increases cytotoxicity, optimal concentrations of tetrameric CPPs required for maximum transduction are at least 300-1000-fold lower than those causing 50% cytotoxicity. Furthermore, although only approximately 60% of MSCs were maximally transduced at 500 muM of monomeric CPPs, >95% of MSCs were transduced with 0.1 muM of tetrameric CPPs. Tetrameric CPPs also significantly increased the formation and net surface charge of CPP/rAd complexes, as well as the binding of rAd to cell membranes at a greater degree than did monomeric CPPs, followed by rapid internalization into MSCs. In a critical-size calvarial defect model, the inclusion of tetrameric CPPs in ex vivo transduction of rAd expressing bone morphogenetic protein 2 into MSCs promoted highly mineralized bone formation. In addition, MSCs that were transduced with rAd expressing brain-derived neurotrophic factor in the presence of tetrameric CPPs improved functional recovery in a spinal cord injury model. These results demonstrated the potential for tetrameric CPPs to provide an innovative tool for MSC-based gene therapy and for in vitro gene delivery to MSCs.
The question of whether grain boundaries (GBs) in niobium can be responsible for lowered operating field (BRF) or quality factor (Q0) in superconducting radio frequency (SRF) cavities is still ...controversial. Here, we show by direct DC transport across planar GBs isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain boundary when the external magnetic field lies in the GB plane. However, increasing the misalignment between the GB plane and the external magnetic field vector markedly reduces preferential flux flow along the GB. Importantly, we find that preferential GB flux flow is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain boundaries of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly the final chemical treatment and the angle between the magnetic field and the GB plane, suggests two more reasons why real cavity performance can be so variable.
Background and purpose: Lubiprostone (Amitiza), a possible ClC‐2 channel opener derived from prostaglandin E1 and indicated for the treatment of constipation, increases chloride ion transport and ...fluid secretion into the intestinal lumen. As lubiprostone may also directly modulate gastrointestinal motility, we investigated its actions and the possible involvement of prostaglandin EP receptor activation on rat and human isolated gastrointestinal preparations.
Experimental approach: Rat and human isolated preparations were mounted in tissue baths for isometric recording. The effects of lubiprostone on muscle tension and on electrically stimulated, neuronal contractions were investigated in the absence and presence of EP receptor antagonists.
Key results: In rat and human stomach longitudinal muscle, lubiprostone induced a contraction (pEC50 of 7.0±0.0, n=4 and 6.4±0.2, n=3, respectively), which was inhibited by pretreatment with the EP1 receptor antagonist, EP1A 300 nM (pEC50 reduced to 6.2±0.2, n=6), but not by the EP3 or EP4 receptor antagonists (L‐798106 and GW627368X, respectively, 1 μM, P>0.05). Lubiprostone also reduced electrically stimulated, neuronal contractions in rat and human colon circular muscle preparations (pIC50 of 8.9±0.4, n=7 and 8.7±0.9, n=6, respectively), an effect mediated pre‐junctionally. This effect was reduced by the EP4 receptor antagonist (pIC50 of 6.7±1.1, n=7 and 7.7±0.4, n=6, respectively) but not by EP1 or EP3 receptor antagonists.
Conclusions and implications: In rats and humans, lubiprostone contracts stomach longitudinal muscle and inhibits neuronally mediated contractions of colon circular muscle. Experiments are now needed to determine if this additional activity of lubiprostone contributes to its clinical efficacy and/or side‐effect profile.
Abstract The 1144 phase (Ae1A1Fe4As4) shows a strong advantage of engineering fabrication among Fe (Iron)-based superconductor (FBS) family due to the robustness of its superconducting properties ...with respect to chemical inhomogeneities, granted by its uniform crystalline-layered structure. This regularity is furthermore associated to crystalline defects capable of acting as efficient pinning centers, from which high critical currents can achieved at high fields. Like other FBS phases, its lossless current-carrying capability can be remarkably degraded by distractions at grain boundaries (GBs). GB oxidation is an issue of upmost importance to the realization of the practical FBS application for high field (> 20T) magnet. In this study, we explore oxidized grain boundary and intrinsic grain structural properties of 1144 polycrystalline samples by applying analytical electron microscopy such as atomic resolution scanning transmission electron microscopy and atom probe tomography. These structural properties of samples produced by a mechanochemically assisted synthesis are evaluated following the degradation of superconducting properties due to oxidation. We observe a strong correlation between the contamination at grain boundaries and the decrease of transport properties of the bulk sample, while the crystallin structure seems to be not affected by the oxidation.
Powder-in-tube (PIT) Nb3Sn wires are competing with Restacked-Rod-Process (RRP ) for the realization of the high luminosity upgrade of the Large Hadron Collider (LHC) at CERN. These two conductors ...have different properties and microstructures that are in both cases averages of an inhomogeneous A15 microstructure. PIT has in general a smaller fraction of A15 in the non-Cu cross-section than RRP and a lower non-Cu Jc (12 T, 4.2 K) (2500-2700 A mm−2 versus 2900-3000 A mm−2) but it can be made in smaller filament diameters, which is an important property for LHC magnets. Another characteristic of PIT A15 is that ∼25% is made up of ∼1-2 m sized grains (typically ∼10 times the small grain (SG) diameter) and their contribution to transport is uncertain. Here we studied a 192 filament Ta-doped, 1 mm diameter PIT wire and combined multiple characterization techniques in order to distinguish the different wire components, to determine their individual properties and to identify which components are current-carriers. We found multiple evidence that the large A15 grains, which are also the highest-Tc grains, do not contribute to transport at high field and that the only current-carrying A15 is the SG with Tc <17.7 K. However, because of the high density of grain boundaries in the SG A15 layer, PIT has an exceptionally high SG-layer Jc and high specific grain boundary pinning force, QGB. These findings clearly show that it is essential to increase the ratio of small to large and disconnected grains in order to improve PIT performance.
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