6,766 research outputs found
Hydrodynamic limit of gradient exclusion processes with conductances
Fix a strictly increasing right continuous with left limits function W: \bb
R \to \bb R and a smooth function \Phi : [l,r] \to \bb R, defined on some
interval of \bb R, such that . We prove that
the evolution, on the diffusive scale, of the empirical density of exclusion
processes, with conductances given by , is described by the weak solutions
of the non-linear differential equation . We derive some properties of the operator and prove
uniqueness of weak solutions of the previous non-linear differential equation
Dynamics explorer interdisciplinary scientist investigations
This document is a final report on research activities and accomplishments that occurred during the funding period of 10-1-90 through 1-30-94. The focus of our interdisciplinary investigation during the Dynamics Explorer Mission was on the complex coupling processes that tap the magnetic-storm energy, stored in the ring current particle reservoir, and transport this energy into the subauroral, midlatitude and even equatorial ionospheric regions. The transport of energy through the inner magnetosphere and into the underlying ionospheric regions is a critical element in our understanding of the impact of solar and magnetic disturbances on upper atmospheric and ionospheric regions equatorward of the auroral zone
Midlatitude and highâlatitude electron density profiles in the ionosphere of Saturn obtained by Cassini radio occultation observations
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95024/1/jgra19781.pd
Evaluating multi-loop Feynman diagrams with infrared and threshold singularities numerically
We present a method to evaluate numerically Feynman diagrams directly from
their Feynman parameters representation. We first disentangle overlapping
singularities using sector decomposition. Threshold singularities are treated
with an appropriate contour deformation. We have validated our technique
comparing with recent analytic results for the gg->h two-loop amplitudes with
heavy quarks and scalar quarks.Comment: 8 pages, 3 figures; references added, version to appear in JHE
Variational approach to the scattering of charged particles by a many-electron system
We report a variational approach to the nonlinearly screened interaction of
charged particles with a many-electron system. This approach has been developed
by introducing a modification of the Schwinger variational principle of
scattering theory, which allows to obtain nonperturbative scattering
cross-sections of moving projectiles from the knowledge of the linear and
quadratic density-response functions of the target. Our theory is illustrated
with a calculation of the energy loss per unit path length of slow antiprotons
moving in a uniform electron gas, which shows good agreement with a fully
nonlinear self-consistent Hartree calculation. Since available self-consistent
calculations are restricted to low heavy-projectile velocities, we expect our
theory to have novel applications to a variety of processes where nonlinear
screening plays an important role.Comment: 10 pages, 2 figures; Accepted to Physical Review
Secondary metabolites from Stachys palustris L.
In this work we report the first total analysis of the secondary metabolites from a sample of Stachys palustris L., an herbaceous perennial plant belonging to Lamiaceae, collected in Hungary.
The phytochemical analysis, performed by means of classical column chromatography and NMR spectroscopy and Mass spectrometry (MS), allowed us to isolate and identify eight compounds such as verbascoside (1) [1], echinacoside (2) [1], two isoscutellarein derivatives (3, 4) [2,3], chlorogenic acid (5) [3], harpagide (6) [4], 8-O-acetyl-harpagide (7) [4] and monomelittoside (8) [4]. These compounds belong to four different classes of chemical compounds namely phenyl-ethanoid glycosides (PhGs) (compounds 1, 2), flavonoids (compounds 3,4), caffeoyl-quinic acids (compound 5) and iridoids (compounds 6,7 and 8).
From a chemosystematic point of view, these compounds are all important: compounds (6) and (7) are considered as the major chemotaxonomic markers of the genus; compound (1) and (8) resulted new constituents in this species and compound (2) is even new in the genus. In addition to this, the co-occurrence of iridoids and PhGs has a chemosystematic importance since it is widely demonstrated their presence in Asterids [1, 3]. Lastly, compounds (3) and (4) such as compounds (5),(6) and (7) have already been found in Stachys species, giving, this way, evidence of a phytochemical pattern perfectly in accordance with those reported in literature for other members of this genus. Nevertheless, itâs worth to underline the fact that compounds (3) and (4), like all isoscutellarein derivatives containing allose, seem to have a restricted distribution in only some genera of Lamiaceae
Involvement of Mhc Loci in immune responses that are not Ir-gene-controlled
Twenty-nine randomly chosen, soluble antigens, many of them highly complex, were used to immunize mice of two strains, C3H and B10.RIII. Lymphnode cells from the immunized mice were restimulated in vitro with the priming antigens and the proliferative response of the cells was determined. Both strains were responders to 28 of 29 antigens. Eight antigens were then used to immunize 11 congenic strains carrying different H-2 haplotypes, and the T-cell proliferative responses of these strains were determined. Again, all the strains responded to seven of the eight antigens. These experiments were then repeated, but this time -antibodies specific for the A (AA) or E (EE) molecules were added to the culture to block the in vitro responsiveness. In all but one of the responses, inhibition with both A-specific and E-specific antibodies was observed. The response to one antigen (Blastoinyces) was exceptional in that some strains were nonresponders to this antigen. Furthermore, the response in the responder strains was blocked with A-specific, but not with E-specific, antibodies. The study demonstrates that responses to antigens not controlled by Irr genes nevertheless require participation of class II Mhc molecules. In contrast to Ir gene-controlled responses involving either the A- or the E-molecule controlling loci (but never both), the responses not Ir-controlled involve participation of both A- and E-controlling loci. The lack of Ir-gene control is probably the result of complexity of the responses to multiple determinants. There is thus no principal difference between responses controlled and those not controlled by Ir genes: both types involve the recognition of the antigen, in the context of Mhc molecules
Time-dependent density-functional theory approach to nonlinear particle-solid interactions in comparison with scattering theory
An explicit expression for the quadratic density-response function of a
many-electron system is obtained in the framework of the time-dependent
density-functional theory, in terms of the linear and quadratic
density-response functions of noninteracting Kohn-Sham electrons and functional
derivatives of the time-dependent exchange-correlation potential. This is used
to evaluate the quadratic stopping power of a homogeneous electron gas for slow
ions, which is demonstrated to be equivalent to that obtained up to second
order in the ion charge in the framework of a fully nonlinear scattering
approach. Numerical calculations are reported, thereby exploring the range of
validity of quadratic-response theory.Comment: 14 pages, 3 figures. To appear in Journal of Physics: Condensed
Matte
Constraining Maximally Supersymmetric Membrane Actions
We study the recent construction of maximally supersymmetric field theory
Lagrangians in three spacetime dimensions that are based on algebras with a
triple product. Assuming that the algebra has a positive definite metric
compatible with the triple product, we prove that the only non-trivial examples
are either the well known case based on a four dimensional algebra or direct
sums thereof.Comment: 11 pages, very minor changes. Reference added. Version to be
published in JHE
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