604 research outputs found
Electron-hole asymmetry in Co- and Mn-doped SrFe2As2
Phase diagram of electron and hole-doped SrFe2As2 single crystals is
investigated using Co and Mn substitution at the Fe-sites. We found that the
spin-density-wave state is suppressed by both dopants, but the superconducting
phase appears only for Co (electron)-doping, not for Mn (hole)-doping. Absence
of the superconductivity by Mn-doping is in sharp contrast to the hole-doped
system with K-substitution at the Sr sites. Distinct structural change, in
particular the increase of the Fe-As distance by Mn-doping is important to have
a magnetic and semiconducting ground state as confirmed by first principles
calculations. The absence of electron-hole symmetry in the Fe-site-doped
SrFe2As2 suggests that the occurrence of high-Tc superconductivity is sensitive
to the structural modification rather than the charge doping.Comment: 7 pages, 6 figure
B cellāintrinsic TLR signals amplify but are not required for humoral immunity
Although innate signals driven by Toll-like receptors (TLRs) play a crucial role in T-dependent immune responses and serological memory, the precise cellular and time-dependent requirements for such signals remain poorly defined. To directly address the role for B cellāintrinsic TLR signals in these events, we compared the TLR response profile of germinal center (GC) versus naive mature B cell subsets. TLR responsiveness was markedly up-regulated during the GC reaction, and this change correlated with altered expression of the key adaptors MyD88, Mal, and IRAK-M. To assess the role for B cellāintrinsic signals in vivo, we transferred MyD88 wild-type or knockout B cells into B cellādeficient Ī¼MT mice and immunized recipient animals with 4-hydroxy-3-nitrophenylacetyl (NP) chicken gamma globulin. All recipients exhibited similar increases in NP-specific antibody titers during primary, secondary, and long-term memory responses. The addition of lipopolysaccharide to the immunogen enhanced B cell-intrinsic, MyD88-dependent NP-specific immunoglobulin (Ig)M production, whereas NP-specific IgG increased independently of TLR signaling in B cells. Our data demonstrate that B cellāintrinsic TLR responses are up-regulated during the GC reaction, and that this change significantly promotes antigen-specific IgM production in association with TLR ligands. However, B cellāintrinsic TLR signals are not required for antibody production or maintenance
Visualization of defects in single-crystal and thin-film PdCoO2 using aberration-corrected scanning transmission electron microscopy
Funding: This work was primarily supported by the U.S. Department of Energy, Office of Basic Sciences, Division of Materials Sciences and Engineering, under Award No. DE-SC0002334.Single-crystal delafossite PdCoO2 is known to have an extremely low intrinsic impurity concentration of ~0.001%, demonstrating extraordinarily high conductivity with a mean free path of ~20 microns at low temperatures. However, when grown as thin films, the resistivity at room temperature increases by a factor of 3 to 80 times, depending on the film thickness. Using scanning transmission electron microscopy, we identify different classes of defects for the single crystal vs epitaxial thin film. The dominant defect for single-crystal PdCoO2 is found to be ribbon-like defects. For the thin films, we identify different types of defects arising in epitaxial thin films mainly due to substrate termination that disrupt the lateral connectivity of the conducting planes. Our results are consistent with the high conductivity of single crystals and increased electrical resistivity of the thin films compared to that of single crystals, suggesting that selecting a proper substrate, improving surface quality, and reducing the step density are the keys to enhance the film quality for utilizing PdCoO2 as a platform for future applications.PostprintPeer reviewe
Wheat Yield Trend and Soil Fertility Status in Long Term Rice-Rice-Wheat Cropping System
A long-term soil fertility experiment under rice-rice-wheat system was performed to evaluate the long term effects of inorganic fertilizer and manure applications on soil properties and grain yield of wheat. The experiment began since 1978 was laid out in randomized complete block design with 9 treatments replicated 3 times. From 1990 onwards, periodic modifications have been made in all the treatments splitting the plots in two equal halves of 4 x 3 m2 leaving one half as original. In the original treatments, recent data revealed that the use of Farm Yard Manure (FYM) @10 t ha-1 gave significantly (Pā¤0.05) higher yield of 2.3 t ha-1 in wheat, whereas control plot gave the lowest grain yield of 277 kg ha-1. Similarly, in the modified treatments, the use of FYM @10 t ha-1 along with inorganic Nitrogen (N) and Potassium oxide (K2O) @ 50 kg ha-1 produced significantly (Pā¤0.05) the highest yield of 2.4 t/ha in wheat. The control plot with an indigenous nutrient supply only produced wheat yield of 277 kg ha-1 after 35th year completion of rice-rice-wheat system. A sharp decline in wheat yields was noted in minus N, phosphorus (P), Potassium (K) treatments during recent years. Yields were consistently higher in the N:P2O5:K2O and FYM treatments than in treatments, where one or more nutrients were lacking. The application of P2O5 and K2O caused a partial recovery of yield in P and K deficient plots. There was significant (Pā¤0.05) effect of use of chemical fertilizers and manure on soil properties. The soil analysis data showed an improvement in soil pH (7.8), soil organic matter (4.1%), total N content (0.16%), available P (503.5 kg P2O5 ha-1) and exchangeable K (137.5 kg K2O ha-1) in FYM applied treatments over all other treatments. The findings showed that the productivity of the wheat can be increased and sustained by improving nutrient through the integrated use of organic and inorganic manures in long term.Journal of Nepal Agricultural Research Council Vol.1 2015 pp.21-2
Synergistic High Charge-Storage Capacity for Multi-level Flexible Organic Flash Memory
Electret and organic floating-gate memories are next-generation flash storage mediums for printed organic complementary circuits. While each flash memory can be easily fabricated using solution processes on flexible plastic substrates, promising their potential for on-chip memory organization is limited by unreliable bit operation and high write loads. We here report that new architecture could improve the overall performance of organic memory, and especially meet high storage for multi-level operation. Our concept depends on synergistic effect of electrical characterization in combination with a polymer electret (poly(2-vinyl naphthalene) (PVN)) and metal nanoparticles (Copper). It is distinguished from mostly organic nano-floating-gate memories by using the electret dielectric instead of general tunneling dielectric for additional charge storage. The uniform stacking of organic layers including various dielectrics and poly(3-hexylthiophene) (P3HT) as an organic semiconductor, followed by thin-film coating using orthogonal solvents, greatly improve device precision despite easy and fast manufacture. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as high-k blocking dielectric also allows reduction of programming voltage. The reported synergistic organic memory devices represent low power consumption, high cycle endurance, high thermal stability and suitable retention time, compared to electret and organic nano-floating-gate memory devices
Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). V. The Complete SMUDGes Catalog and the Nature of Ultra-Diffuse Galaxies
We present the completed catalog of ultra-diffuse galaxy (UDG) candidates
(7070 objects) from our search of the DR9 Legacy Survey images, including
distance and total mass estimates for 1529 and 1436 galaxies, respectively,
that we provide and describe in detail. From the sample with estimated
distances, we obtain a sample of 585 UDGs ( mag arcsec
and kpc) over 20,000 sq. deg of sky in various environments. We
conclude that UDGs in our sample are limited to
M/M and are on average a factor of 1.5 to 7
deficient in stars relative to the general population of galaxies of the same
total mass. That factor increases with increasing galaxy size and mass up to a
factor of 10 when the total mass of the UDG increases beyond M M. We do not find evidence that this factor has a dependence
on the UDG's large-scale environment.Comment: 21 pages, accepted for publication in ApJS, full catalog available
upon reques
Evidence of metallic clustering in annealed Ga1-xMnxAs from atypical scaling behavior of the anomalous Hall coefficient
We report on the anomalous Hall coefficient and longitudinal resistivity
scaling relationships on a series of annealed Ga1-xMnxAs epilayers (x~0.055).
As-grown samples exhibit scaling parameter n of ~ 1. Near the optimal annealing
temperature, we find n ~ 2 to be consistent with recent theories on the
intrinsic origins of anomalous Hall Effect in Ga1-xMnxAs. For annealing
temperatures far above the optimum, we note n > 3, similar behavior to certain
inhomogeneous systems. This observation of atypical behavior agrees well with
characteristic features attributable to spherical resonance from metallic
inclusions from optical spectroscopy measurements.Comment: 3 pages, 3 figure
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