3,505 research outputs found
Robustness of Regularity for the D Convective Brinkman-Forchheimer Equations
We prove a robustness of regularity result for the D convective
Brinkman-Forchheimer equations \partial_tu -\mu\Delta u + (u \cdot \nabla)u
+ \nabla p + \alpha u + \beta\abs{u}^{r - 1}u = f, for the range of the
absorption exponent (for there exist global-in-time
regular solutions), i.e. we show that strong solutions of these equations
remain strong under small enough changes of the initial condition and forcing
function. We provide a smallness condition which is similar to the robustness
conditions given for the D incompressible Navier-Stokes equations by
Chernyshenko et al. (2007) and Dashti & Robinson (2008).Comment: 22 page
Triton calculations with and exchange three-nucleon forces
The Faddeev equations are solved in momentum space for the trinucleon bound
state with the new Tucson-Melbourne and exchange three-nucleon
potentials. The three-nucleon potentials are combined with a variety of
realistic two-nucleon potentials. The dependence of the triton binding energy
on the cut-off parameter in the three-nucleon potentials is studied
and found to be reduced compared to the case with pure exchange. The
exchange parts of the three-nucleon potential yield an overall repulsive
effect. When the recommended parameters are employed, the calculated triton
binding energy turns out to be very close to its experimental value.
Expectation values of various components of the three-nucleon potential are
given to illustrate their significance for binding.Comment: 17 pages Revtex 3.0, 4 figures. Accepted for publication in Phys.
Rev.
Molecular remnant of Nova 1670 (CK Vulpeculae). II. A three-dimensional view on the gas distribution and velocity field
CK Vul is the remnant of an energetic eruption known as Nova 1670 that is
thought to be caused by a stellar merger. The remnant is composed of (1) a
large hourglass nebula of recombining gas (of 71\arcsec size), very similar to
some classical planetary and pre-planetary nebulae (PPNe), and (2) of a much
smaller and cooler inner remnant prominent in millimeter-wave emission from
molecules. We investigate the three-dimensional spatio-kinematic structure of
both components. The analysis of the hourglass structure yields a revised
distance to the object of >2.6 kpc, at least 3.7 times greater than so far
assumed. At this distance, the stellar remnant has a bolometric luminosity >12
L and is surrounded by molecular material of total mass >0.8
M (the latter value has a large systematic uncertainty). We also
analyzed the architecture of the inner molecular nebula using ALMA observations
of rotational emission lines obtained at subarcsecond resolution. We find that
the distribution of neutral and ionized gas in the lobes can be reproduced by
several nested and incomplete shells or jets with different velocity fields and
varying orientations. The analysis indicates that the molecular remnant was
created in several ejection episodes, possibly involving an interacting binary
system. We calculated the linear momentum (10 g cm s)
and kinetic energy (10 erg) of the CK Vul outflows and find
them within the limits typical for classical PPNe. Given the similarities of
the CK Vul outflows to PPNe, we suggest there may CK Vul analogs among wrongly
classified PPNe with low intrinsic luminosities, especially among PPNe with
post-red-giant-branch central stars.Comment: 12 pages, animations at: https://bit.ly/3hR6jSF and
https://shorturl.at/gwzOT . Comments welcome
A Geometric Theory of Diblock Copolymer Phases
We analyze the energetics of sphere-like micellar phases in diblock
copolymers in terms of well-studied, geometric quantities for their lattices.
We argue that the A15 lattice with Pm3n symmetry should be favored as the
blocks become more symmetric and corroborate this through a self-consistent
field theory. Because phases with columnar or bicontinuous topologies
intervene, the A15 phase, though metastable, is not an equilibrium phase of
symmetric diblocks. We investigate the phase diagram of branched diblocks and
find thatthe A15 phase is stable.Comment: 4 pages, RevTeX, 3 eps figures include
Three-Nucleon Force and the -Mechanism for Pion Production and Pion Absorption
The description of the three-nucleon system in terms of nucleon and
degrees of freedom is extended to allow for explicit pion production
(absorption) from single dynamic de-excitation (excitation) processes.
This mechanism yields an energy dependent effective three-body hamiltonean. The
Faddeev equations for the trinucleon bound state are solved with a force model
that has already been tested in the two-nucleon system above pion-production
threshold. The binding energy and other bound state properties are calculated.
The contribution to the effective three-nucleon force arising from the pionic
degrees of freedom is evaluated. The validity of previous coupled-channel
calculations with explicit but stable isobar components in the
wavefunction is studied.Comment: 23 pages in Revtex 3.0, 9 figures (not included, available as
postscript files upon request), CEBAF-TH-93-0
Strong-Segregation Theory of Bicontinuous Phases in Block Copolymers
We compute phase diagrams for starblock copolymers in the
strong-segregation regime as a function of volume fraction , including
bicontinuous phases related to minimal surfaces (G, D, and P surfaces) as
candidate structures. We present the details of a general method to compute
free energies in the strong segregation limit, and demonstrate that the gyroid
G phase is the most nearly stable among the bicontinuous phases considered. We
explore some effects of conformational asymmetry on the topology of the phase
diagram.Comment: 14 pages, latex, 21 figures, to appear in Macromolecule
Individual variation in levels of haptoglobin-related protein in children from Gabon
Background: Haptoglobin related protein (Hpr) is a key component of trypanosome lytic factors (TLF), a subset of highdensity lipoproteins (HDL) that form the first line of human defence against African trypanosomes. Hpr, like haptoglobin (Hp) can bind to hemoglobin (Hb) and it is the Hpr-Hb complexes which bind to these parasites allowing uptake of TLF. This unique form of innate immunity is primate-specific. To date, there have been no population studies of plasma levels of Hpr, particularly in relation to hemolysis and a high prevalence of ahaptoglobinemia as found in malaria endemic areas. Methods and Principal Findings: We developed a specific enzyme-linked immunosorbent assay to measure levels of plasma Hpr in Gabonese children sampled during a period of seasonal malaria transmission when acute phase responses (APR), malaria infection and associated hemolysis were prevalent. Median Hpr concentration was 0.28 mg/ml (range 0.03-1.1). This was 5-fold higher than that found in Caucasian children (0.049 mg/ml, range 0.002-0.26) with no evidence of an APR. A general linear model was used to investigate associations between Hpr levels, host polymorphisms, parasitological factors and the acute phase proteins, Hp, C-reactive protein (CRP) and albumin. Levels of Hpr were associated with Hp genotype, decreased with age and were higher in females. Hpr concentration was strongly correlated with that of Hp, but not CRP
Exotic smooth structures and symplectic forms on closed manifolds
We give a short proof of the (known) result that there are no Kaehler
structures on exotic tori. This yields a negative solution to a problem posed
by Benson and Gordon. W discuss the symplectic version of the problem and
analyze results which yield an evidence for the conjecture that there are no
symplectic structures on exotic tori.Comment: AMSLaTeX, 16 pages, a new version. A survey of the symplectic version
of the problem is adde
Relativistic Corrections to the Triton Binding Energy
The influence of relativity on the triton binding energy is investigated. The
relativistic three-dimensional version of the Bethe-Salpeter equation proposed
by Blankenbecler and Sugar (BbS) is used. Relativistic (non-separable)
one-boson-exchange potentials (constructed in the BbS framework) are employed
for the two-nucleon interaction. In a 34-channel Faddeev calculation, it is
found that relativistic effects increase the triton binding energy by about 0.2
MeV. Including charge-dependence (besides relativity), the final triton binding
energy predictions are 8.33 and 8.16 MeV for the Bonn A and B potential,
respectively.Comment: 25 pages of text (latex), 1 figure (not included, available upon
request
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