62 research outputs found
Graphene-oxide-semiconductor planar-type electron emission device
Graphene was used as the topmost electrode for a metal-oxide-semiconductor planar-type electron emission device. With several various layers, graphene as a gate electrode on the thin oxide layer was directly deposited by gallium vapor-assisted chemical vapor deposition. The maximum efficiency of the electron emission, defined as the ratio of anode current to cathode current, showed no dependency on electrode thickness in the range from 1.8 nm to 7.0 nm, indicating that electron scattering on the inside of the grapheneelectrode is practically suppressed. In addition, a high emission current density of 1–100 mA/cm2 was obtained while maintaining a relatively high electron emission efficiency of 0.1%–1.0%. The graphene-oxide-semiconductor planar-type electron emission device has great potential to achieve both high electron emission efficiency and high electron emissioncurrent density in practical applications
Initial Surgical Versus Conservative Strategies in Patients With Asymptomatic Severe Aortic Stenosis
AbstractBackgroundCurrent guidelines generally recommend watchful waiting until symptoms emerge for aortic valve replacement (AVR) in asymptomatic patients with severe aortic stenosis (AS).ObjectivesThe study sought to compare the long-term outcomes of initial AVR versus conservative strategies following the diagnosis of asymptomatic severe AS.MethodsWe used data from a large multicenter registry enrolling 3,815 consecutive patients with severe AS (peak aortic jet velocity >4.0 m/s, or mean aortic pressure gradient >40 mm Hg, or aortic valve area <1.0 cm2) between January 2003 and December 2011. Among 1,808 asymptomatic patients, the initial AVR and conservative strategies were chosen in 291 patients, and 1,517 patients, respectively. Median follow-up was 1,361 days with 90% follow-up rate at 2 years. The propensity score–matched cohort of 582 patients (n = 291 in each group) was developed as the main analysis set for the current report.ResultsBaseline characteristics of the propensity score–matched cohort were largely comparable, except for the slightly younger age and the greater AS severity in the initial AVR group. In the conservative group, AVR was performed in 41% of patients during follow-up. The cumulative 5-year incidences of all-cause death and heart failure hospitalization were significantly lower in the initial AVR group than in the conservative group (15.4% vs. 26.4%, p = 0.009; 3.8% vs. 19.9%, p < 0.001, respectively).ConclusionsThe long-term outcome of asymptomatic patients with severe AS was dismal when managed conservatively in this real-world analysis and might be substantially improved by an initial AVR strategy. (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis Registry; UMIN000012140
Antiferromagnetic superexchange via 3d states of titanium in EuTiO3 as seen from hybrid Hartree-Fock density functional calculations
A superexchange mechanism between Eu^2+ 4f spins via the 3d states of nonmagnetic Ti^4+ ions is proposed through first-principles calculations based on a hybrid Hartree-Fock density functional approach to explain G-type antiferromagnetism in EuTiO3. This mechanism is supported by systematic calculations for related Eu2+-based perovskite oxides. In EuTiO3, the competition between the antiferromagnetic superexchange and an indirect ferromagnetic exchange via the Eu 5d states leads to a delicate balance between antiferromagnetic and ferromagnetic phases. The superexchange mechanism involving the Ti 3d states hints at the microscopic origin of the strong spin-lattice coupling in EuTiO3
Low-power-consumption, high-current-density, and propellantless cathode using graphene-oxide-semiconductor structure array
Oxidation Resistance Improvement of Graphene-Oxide-Semiconductor Planar-Type Electron Sources Using h-BN as an Oxygen-Resistant, Electron-Transmissive Coating
Ferromagnetism induced by lattice volume expansion and amorphization in EuTiO[3] thin films
Lattice volume expansion or amorphization renders EuTiO[3] ferromagnetic, although the stable phase of crystalline EuTiO[3] is an antiferromagnet. The lattice volume expansion is induced into the crystalline EuTiO[3] thin film by utilizing the lattice mismatch between the thin film and a substrate. The magnetization at low temperatures monotonically increases with an increase in lattice volume for the crystalline EuTiO3 thin film, coincident with the results of calculations based on the hybrid Hartree–Fock density functional approach. The ferromagnetic interaction between Eu[2+] ions is enhanced by the amorphization as well; the amorphous EuTiO[3] thin film becomes a ferromagnet, and the Curie temperature is higher for amorphous Eu[2]TiO[4] than for its crystalline counterpart. The phenomenon, that is, the volume expansion- and amophization-induced ferromagnetism, is explained in terms of the competition between ferromagnetic and antiferromagnetic interactions among Eu[2+] ions
Evolution of the brain developmental plan: Insights from agnathans.
International audienceIn vertebrate evolution, the brain exhibits both conserved and unique morphological features in each animal group. Thus, the molecular program of nervous system development is expected to have experienced various changes through evolution. In this review, we discuss recent data from the agnathan lamprey (jawless vertebrate) together with available information from amphioxus and speculate the sequence of changes during chordate evolution that have been brought into the brain developmental plan to yield the current variety of the gnathostome (jawed vertebrate) brains
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