22,872 research outputs found
Cosmic-ray transport in the galactic magnetosphere
It is advantageous to regard cosmic rays as the constitutent particles of the Galactic radiation belts and cosmic ray energization as a consequence of inward radial diffusion in the quasi-dipolar Galactic magnetosphere. This process occurs in addition to Fermi acceleration. The purpose of this work is to explore a magnetospheric explanation for the elevation of Galactic charged particles to cosmic ray energies. The magnetosphere that is of interest in this context is not a planetary magnetosphere but a galactic magnetosphere entirely analogous to those inferred from radio observations of distant galaxies. It is the magnetosphere of the Milky Way. Cosmic rays are (by this interpretation) the charged particles that constitute the radiation belts of the Galactic magnetosphere. Thus, the mechanism by which charged particles attain cosmic-ray energies is presumable the mechanism by which radiation-belt particles attain high energies in more familiar magnetosphere, i.e., the radial diffusion associated with magnetic disturbances that contain spectral power resonant with the azimuthal drift of the particles
The Wisconsin magmatic terrane: An Early Proterozoic greenstone-granite terrane formed by plate tectonic processes
The Wisconsin magmatic terrane (WMT) is an east trending belt of dominantly volcanic-plutonic complexes of Early Proterozoic age (approx. 1850 m.y.) that lies to the south of the Archean rocks and Early Proterozoic epicratonic sequence (Marquette Range Supergroup) in Michigan. It is separated from the epicratonic Marquette Range Supergroup by the high-angle Niagara fault, is bounded on the south, in central Wisconsin, by Archean gneisses, is truncated on the west by rocks of the Midcontinent rift system, and is intruded on the east by the post-orogenic Wolf river batholith. The overall lithologic, geochemical, metallogenic, metamorphic, and deformational characteristics of the WMT are similar to those observed in recent volcanic arc terranes formed at sites of plate convergence. It is concluded that the WMT represents an evolved oceanic island-arc terrane accreated to the Superior craton in the Early Proterozoic. This conclusion is strengthened by the apparent absence of Archean basement from most of the WMT, and the recent recognition of the passive margin character of the epicratonic Marquette Range Supergroup
Acute pulmonary pathology and sudden death in rats following the intravenous administration of the plasticizer, DI (2-ethylhexyl) phthalate, solubilized with Tween surfactants
Intravenous administration of 200-300 mg/kg of di(2-ethylhexyl)phthalate (DEHP) solubilized in aqueous solutions of several Tween surfactants caused respiratory distress in rats. There was a dose-dependent lethality with death generally occurring within 90 minutes after injection. The lungs from DEHP:Tween treated animals were enlarged, generally darkened, and in some cases showed hemorrhagic congestion. Neither the overt symptoms nor the morphologic alterations resulting from DEHP:Tween administration could be reproduced by intravenous administration of aqueous Tween solutions alone. The absence of pulmonary abnormalities following the intravenous administration of DEHP as an aqueous emulsion given either alone or even as soon as 2 minutes after pretreatment with Tween 80, suggests that the specific in vivo interaction between DEHP and Tween surfactants depends on the prior formation of water-soluble micelles of DEHP
The Herschel Space Observatory view of dust in M81
We use Herschel Space Observatory data to place observational constraints on the peak and Rayleigh-Jeans slope of dust emission observed at 70−500 μm in the nearby spiral galaxy M81. We find that the ratios of wave bands between 160 and 500 μm are primarily dependent on radius but that the ratio of 70 to 160 μm emission shows no clear dependence on surface brightness or radius. These
results along with analyses of the spectral energy distributions imply that the 160−500 μm emission traces 15−30 K dust heated by evolved stars in the bulge and disc whereas the 70 μm emission includes dust heated by the active galactic nucleus and young stars in star forming regions
A Frustrated 3-Dimensional Antiferromagnet: Stacked Layers
We study a frustrated 3D antiferromagnet of stacked layers. The
intermediate 'quantum spin liquid' phase, present in the 2D case, narrows with
increasing interlayer coupling and vanishes at a triple point. Beyond this
there is a direct first-order transition from N{\' e}el to columnar order.
Possible applications to real materials are discussed.Comment: 11 pages,7 figure
Half-Filled Lowest Landau Level on a Thin Torus
We solve a model that describes an interacting electron gas in the
half-filled lowest Landau level on a thin torus, with radius of the order of
the magnetic length. The low energy sector consists of non-interacting,
one-dimensional, neutral fermions. The ground state, which is homogeneous, is
the Fermi sea obtained by filling the negative energy states and the excited
states are gapless neutral excitations out of this one-dimensional sea.
Although the limit considered is extreme, the solution has a striking
resemblance to the composite fermion description of the bulk
state--the ground state is homogeneous and the excitations are neutral and
gapless. This suggests a one-dimensional Luttinger liquid description, with
possible observable effects in transport experiments, of the bulk state where
it develops continuously from the state on a thin torus as the radius
increases.Comment: 4 pages, 1 figur
Properties of charge density waves in LaBaCuO
We report a comprehensive x-ray scattering study of charge density wave
(stripe) ordering in , for which the
superconducting is greatly suppressed. Strong superlattice reflections
corresponding to static ordering of charge stripes were observed in this
sample. The structural modulation at the lowest temperature was deduced based
on the intensity of over 70 unique superlattice positions surveyed. We found
that the charge order in this sample is described with one-dimensional charge
density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0,
0.23, 0.5) respectively on neighboring planes. The structural
modulation due to the charge density wave order is simply sinusoidal, and no
higher harmonics were observed. Just below the structural transition
temperature, short-range charge density wave correlation appears, which
develops into a large scale charge ordering around 40 K, close to the spin
density wave ordering temperature. However, this charge ordering fails to grow
into a true long range order, and its correlation length saturates at , and slightly decreases below about 15 K, which may be due to the onset
of two-dimensional superconductivity.Comment: 11 pages, 9 figure
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