5,588 research outputs found
Spin-charge separation at small lengthscales in the 2D t-J model
We consider projected wavefunctions for the 2D model. For various
wavefunctions, including correlated Fermi-liquid and Luttinger-type
wavefunctions we present the static charge-charge and spin-spin structure
factors. Comparison with recent results from a high-temperature expansion by
Putikka {\it et al.} indicates spin-charge separation at small lengthscales.Comment: REVTEX, 5 pages, 5 figures hardcopies availabl
Gamma-ray line emission from Al-26 produced by Wolf-Rayet stars
The recent satellite observations of the 1.8 MeV line from the decay of Al-26 has given a new impetus to the study of the nucleosynthesis of Al-26. The production and ejection of Al-26 by massive mass-losing stars (Of and WR stars) is discussed in the light of recent stellar models. The longitude distribution of the Al-26 gamma ray line emission produced by the galactic collection of WR stars is derived based on various estimates of their radial distribution. This longitude profile provides: (1) a specific signature of massive stars on the background of other potential Al-26 sources, as novae, supernovae, certain red giants and possibly AGB stars; and (2) a possible tool to improve the data analysis of the HEAO 3 and SMM experiments
Vertex routing models
A class of models describing the flow of information within networks via
routing processes is proposed and investigated, concentrating on the effects of
memory traces on the global properties. The long-term flow of information is
governed by cyclic attractors, allowing to define a measure for the information
centrality of a vertex given by the number of attractors passing through this
vertex. We find the number of vertices having a non-zero information centrality
to be extensive/sub-extensive for models with/without a memory trace in the
thermodynamic limit. We evaluate the distribution of the number of cycles, of
the cycle length and of the maximal basins of attraction, finding a complete
scaling collapse in the thermodynamic limit for the latter. Possible
implications of our results on the information flow in social networks are
discussed.Comment: 12 pages, 6 figure
A foam model highlights the differences of the macro- and microrheology of respiratory horse mucus
Native horse mucus is characterized with micro- and macrorheology and
compared to hydroxyethylcellulose (HEC) gel as a model. Both systems show
comparable viscoelastic properties on the microscale and for the HEC the
macrorheology is in good agreement with the microrheology. For the mucus, the
viscoelastic moduli on the macroscale are several orders of magnitude larger
than on the microscale. Large amplitude oscillatory shear experiments show that
the mucus responds nonlinearly at much smaller deformations than HEC. This
behavior fosters the assumption that the mucus has a foam like structure on the
microscale compared to the typical mesh like structure of the HEC, a model that
is supported by cryogenic-scanning-electron-microscopy (CSEM) images. These
images allow also to determine the relative amount of volume that is occupied
by the pores and the scaffold. Consequently, we can estimate the elastic
modulus of the scaffold. We conclude that this particular foam like
microstructure should be considered as a key factor for the transport of
particulate matter which plays a central role in mucus function with respect to
particle penetration. The mesh properties composed of very different components
are responsible for macroscopic and microscopic behavior being part of
particles fate after landing.Comment: Accepted for publication in the Journal of the Mechanical Behavior of
Biomedical Material
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