50,623 research outputs found
Electroresistance effect in La1−xCaxMnO3 (0<x<1) ceramics
No full textElectroresistance (ER) effects were investigated for a full series of manganite ceramics La1-xCaxMnO3 (0 < x < 1) synthesized by solid state reaction The results indicate that while the ER effects are large only in the presence of electrically active high E-field boundaries the equilibrium or metastable electronic-magnetic states in the adjoining domains are also significant as a large ER occurs only at x = 0 51 and x = 0 17 those compositions are both near a two-phase coexistence region i e close to a compositional regime where equilibrium insulating/metallic phase domains and interfaces would occur spontaneously (C) 2010 Elsevier Ltd All rights reserve
Observation of χcJ →3 (K+K-)
No full textBy analyzing (27.12 +/- 0.14) x 10(8) Psi(3686) events collected with the BESIII detector operating at the BEPCII collider, the decay processes X-cJ -> 3( K+ K- ) (J = 0, 1, 2) are observed for the first time with statistical significances of 8.2 sigma, 8.1 sigma, and 12.4 sigma, respectively. The product branching fractions of Psi(3686) -> gamma X-cJ , X-cJ -> 3( K+ K- ) are presented and the branching fractions of X-cJ -> 3( K+ K- ) decays are determined to be B-Xc0 -> 3( K+ K- ) = (10.7 +/- 1.8 +/- 1.1) x 10(-6), B-Xc1 -> 3( K+ K- ) = (4.2 +/- 0.9 +/- 0.5) x 10(-6), and B-Xc2 -> 3( K+ K- ) 1/4 (7.2 +/- 1.1 +/- 0.8) x 10(-6), where the first uncertainties are statistical and the second are systematic
Recommended from our members
Enhanced colour encoding of materials discrimination information for multiple view dual-energy x-ray imaging
No full textThis thesis reports an investigation into dual-energy X-ray discrimination techniques. These techniques are designed to provide colour-coded materials discrimination information in a sequence of perspective images exhibiting sequential parallax. The methods developed are combined with a novel 3D imaging technique employing depth from motion or kinetic depth effect (KDE). This technique when applied to X-ray images is termed KDEX imaging and was developed previously by the university team for luggage screening applications at security checkpoints. A primary motivation for this research is that the dual-energy X-ray techniques, which are routinely incorporated into ‘standard’ 2D luggage scanners, provide relatively crude materials discrimination information. In this work it was critical that robust materials discrimination and colour encoding process was implemented as the sequential parallax exhibited by the KDEX imagery may introduce colour changes, due to the different X-ray beam paths associated with each perspective image. Any introduction of ‘colour noise’ into the resultant image sequences could affect the perception of depth and hinder the ongoing assessment of the potential utility of the dual-energy KDEX technique. Two dual-energy discrimination methods have been developed, termed K-II and W-E respectively. Employing the total amount of attenuation measured at each energy level and the weight fraction of layered structures, a combination of the K-II and the W-E techniques enables the computation and extraction of a target objects’ effective atomic number (Zeff) and its surface density (ρS) in the presence of masking layers
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Search for X (1870) via the decay J/ψ →ωK+K-η
No full textUsing a sample of (10087±44)×106 J/ψ events collected by the BESIII detector at the BEPCII collider, we search for the decay X(1870)→K+K-η via the J/ψ→ωK+K-η process for the first time. No significant X(1870) signal is observed. The upper limit on the branching fraction of the decay J/ψ→ωX(1870)→ωK+K-η is determined to be 9.55×10-7 at the 90% confidence level. In addition, the branching faction B(J/ψ→ωK+K-η) is measured to be (3.33±0.02(stat)±0.12(syst))×10-4
Measurements of K S 0 - K L 0 asymmetries in the decays Λ c + → p K L , S 0 , p K L , S 0 π + π − and p K L , S 0 π 0
No full textAbstract Using e + e − annihilation data sets corresponding to an integrated luminosity of 4.5 fb −1, collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions B Λ c + → p K L 0 = (1.67 ± 0.06 ± 0.04)%, B Λ c + → p K L 0 π + π − = (1.69 ± 0.10 ± 0.05)%, and B Λ c + → p K L 0 π 0 = (2.02 ± 0.13 ± 0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of Λ c + → p K S 0 , Λ c + → p K S 0 π + π − , and Λ c + → p K S 0 π 0 , we present the first measurements of the K S 0 - K L 0 asymmetries R Λ c + K S , L 0 X = B Λ c + → K S 0 X − B Λ c + → K L 0 X B Λ c + → K S 0 X + B Λ c + → K L 0 X in charmed baryon decays: R Λ c + p K S , L 0 = − 0.025 ± 0.031 , R Λ c + p K S , L 0 π + π − = − 0.027 ± 0.048 and R Λ c + p K S , L 0 π 0 = − 0.015 ± 0.046 . No significant asymmetries with statistical significance are observed
Partial wave analysis of ψ (3686) →K+K-η
No full textUsing a sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector, we perform the first partial wave analysis of ψ(3686)→K+K-η. In addition to the well established states, φ(1020), φ(1680), and K3∗(1780), contributions from X(1750), ρ(2150), ρ3(2250), and K2∗(1980) are also observed. The X(1750) state is determined to be a 1-resonance. The simultaneous observation of the φ(1680) and X(1750) indicates that the X(1750), with previous observations in photoproduction, is distinct from the φ(1680). The masses, widths, branching fractions of ψ(3686)→K+K-η, and the intermediate resonances are also measured
A population of isolated hard X-ray sources near the supernova remnant Kes 69
No full textRecent X-ray observations of the supernova remnant (SNR) IC 443 interacting with molecular clouds detected a new population of hard X-ray sources related to the remnant itself, which has been proposed to be fast ejecta fragments propagating within the dense environment. Encouraged by these studies, we obtained a deep XMM-Newton observation of the SNR Kes 69, which also shows signs of a shock-cloud interaction. We report on the detection of 18 hard X-ray sources in the field of Kes 69, which is a number sognificantly higher than expected for the Galactic source population in the field. The sources are spatially correlated with CO emission from the cloud in the remnant environment. The spectra of 3 of the 18 sources can be described as hard power-laws with photon indices smaller than two plus line emission associated with K-shell transitions. We discuss the two most promising scenarios for the interpretation of the sources, namely fast ejecta fragments (as in IC 443) and cataclysmic variables. While most of the observational evidence is consistent with the former interpretation, we cannot rule out the latter
- …
