885 research outputs found
Chemistry of sprite discharges through ion-neutral reactions
International audienceWe estimate the concentration changes, caused by a single streamer in sprites, of ozone and related minor species as odd nitrogen (NOx) and hydrogen (HOx) families in the upper stratosphere and mesosphere. The streamer has an intense electric field and high electron density at its head where a large number of chemically-radical ions and atoms are produced through electron impact on neutral molecules. After propagation of the streamer, the densities of minor species can be perturbed through ion-neutral chemical reactions initiated by the relaxation of these radical products. We evaluate the production rates of ions and atoms using electron kinetics model and assuming the electric field and electron density in the streamer head. We calculate the density variations mainly for NOx, Ox, and HOx species using a one-dimensional model of the neutral and ion composition of the middle atmosphere, including the effect of the sprite streamer. Results at the nighttime condition show that the densities of NO, O3, H, and OH increase suddenly through reactions triggered by firstly produced atomic nitrogen and oxygen, and electrons just after streamer initiation. It is shown that NO and NO2 still remain for 1 h by a certain order of increase with their source-sink balance predominantly around 60 km; for other species, increases in O3, OH, HO2, and H2O2 still remain in the range of 40?70 km. From this affirmative result of long time behavior previously not presented, we emphasize that sprites would have a power to impact on local chemistry at night. We also discuss comparison with previous studies and suggestion for satellite observations
Feedback Instability Analysis for Dipole Configuration with Ionospheric and Magnetospheric Cavities
Correlation Effects in a One-Dimensional Quarter-Filled Electron System with Repulsive Interactions
A one-dimensional electron system at quarter-filling has been examined by
applying the renormalization group method to a bosonized model with on-site (U)
and nearest-neighbor (V) repulsive interactions. By evaluating both normal
scattering and Umklapp scattering perturbatively, we obtain a phase diagram in
which a metallic state with a 2k_F spin density wave (k_F is the Fermi wave
number) moves into an insulating state with charge disproportionation of a 4k_F
charge density wave with an increase in both U and V. The effect of the
next-nearest-neighbor repulsion is also discussed.Comment: 4 pages, 2 figures, to be published in J. Phys. Soc. Jpn. 69 (2000)
No.
Charge Ordering and Spin gap in NaV_2O_5
A possible ground state of NaV_2O_5 is proposed based on the Hartree
approximation for both on-site and intersite Coulomb interactions. The results
indicate that the intersite Coulomb interaction induces a zigzag type of charge
disproportionation (i.e. charge ordering) along the ladders of V-ions resulting
in the localized spins between neighboring ladders to form a spin gap. This new
state, which is different from the spin-Peierls state so far believed, seems to
be consistent with the existing experimental results.Comment: 3 pages, 4 figures, submitted to J. Phys. Soc. Jp
Effects of Next-Nearest-Neighbor Repulsion on One-Dimensional Quarter-Filled Electron Systems
We examine effects of the next-nearest-neighbor repulsion on electronic
states of a one-dimensional interacting electron system which consists of
quarter-filled band and interactions of on-site and nearest-neighbor repulsion.
We derive the effective Hamiltonian for the electrons around wave number \pm
\kf (\kf: Fermi wave number) and apply the renormalization group method to
the bosonized Hamiltonian. It is shown that the next-nearest-neighbor repulsion
makes 4\kf-charge ordering unstable and suppresses the spin fluctuation.
Further the excitation gaps and spin susceptibility are also evaluated.Comment: 19 pages, 8 figures, submitted to J. Phys. Soc. Jp
On the funcÂtion of the Megakaryocyte (Motility, Separation of the Platelet and Phagocytosis), Observations Both in Idiopathic Thrombo-cytopenic Purpura and in Normal Adult
The idiopathic thrombocytopenic purpura was described by
Werlhof as an independent disease first in 1738. Kaznelson
reported the excellent effect of splenectomy for its chronic type in 1915. For the genesis of its thrombocytopenia, there have been many theories to be concluded into the followings, 1) the development of an auto-immune mechanism resulting in platelet destruction, 2) increased platelet destruction in the spleen, 3)
the inhibition of platelet production from the marrow megakaryocytes by a humoral factor produced in the spleen, 4) both increased destruction and decreased production of the platelet. Among the above four theories, the third one is the most popular in the chronic type.</p
Finite-temperature phase transitions in quasi-one-dimensional molecular conductors
Phase transitions in 1/4-filled quasi-one-dimensional molecular conductors
are studied theoretically on the basis of extended Hubbard chains including
electron-lattice interactions coupled by interchain Coulomb repulsion. We apply
the numerical quantum transfer-matrix method to an effective one-dimensional
model, treating the interchain term within mean-field approximation.
Finite-temperature properties are investigated for the charge ordering, the
"dimer Mott" transition (bond dimerization), and the spin-Peierls transition
(bond tetramerization). A coexistent state of charge order and bond
dimerization exhibiting dielectricity is predicted in a certain parameter
range, even when intrinsic dimerization is absent.Comment: to be published in J. Phys. Soc. Jpn., Vol. 76 (2007) No. 1 (5 pages,
4 figures); typo correcte
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