5,836 research outputs found
Adsorption of a binary mixture of monomers with nearest-neighbour cooperative effects
A model for the adsorption of a binary mixture on a one-dimensional infinite
lattice with nearest neighbour cooperative effects is considered. The particles
of the two species are both monomers but differ in the repulsive interaction
experienced by them when trying to adsorb. An exact expression for the coverage
of the lattice is derived. In the jamming limit, it is a monotonic function of
the ratio between the attempt frequencies of the two species, varying between
the values corresponding to each of the two single species. This is in contrast
with the results obtained in other models for the adsorption of particles of
different sizes. The structure of the jamming state is also investigated.Comment: v2: Errors in the figures fixed; same text; 23 pages, 5 figures.
Accepted for publication in Journal of Physics A: Mathematical and Genera
Memory effects in vibrated granular systems
Granular materials present memory effects when submitted to tapping
processes. These effects have been observed experimentally and are discussed
here in the context of a general kind of model systems for compaction
formulated at a mesoscopic level. The theoretical predictions qualitatively
agree with the experimental results. As an example, a particular simple model
is used for detailed calculations.Comment: 12 pages, 5 figures; to appear in Journal of Physics: Condensed
Matter (Special Issue: Proceedings of ESF SPHINX Workshop on ``Glassy
behaviour of kinetically constrained models.''
Effects of chloride ion substitutes and chloride channel blockers on the transient outward current in rat ventricular myocytes
AbstractThe Cai2-insensitive transient outward current, ilo was studied at 20–24°C in rat ventricular myocytes with the whole cell recording patch-clamp technique. The current was recorded before and after replacement of chloride by methanesulfonate or aspartate or in the absence and the presence of chloride channel blockers, SITS or 9-anthracene carboxylic acid. In control conditions (in the presence of external divalent cations, Ca2+ and Cd2+, Cd2+ being used to suppress Ca2+ current), ilo inactivation was composed of a fast and a slow component. When methanesulfonate was substituted for external Cl− the peak current decreased to a variable extent, but the inactivation of the remaining current was still composed of a fast and a slow component. In contrast, the inactivation of the difference current was well fitted by a single exponential. The time to peak of the difference current was shorter than that of the current recorded either in the absence or the presence of methanesulfonate. Both activation- and steady-state inactivation-voltage curves were either unchanged (n = 4) or shifted by a few mV (5.5 mV, n = 14) towards positive potentials when methanesulfonate was substituted for Cl− The current remaining in methanesulfonate reversed at potentials closed to EK. The difference current was composed of a peak and a steady-state component. The peak was suppressed by 4-aminopyridine whereas the steady-state component was not. The peak was also suppressed when pipette solution contained Cs+ instead of K+ but was still present when the Hepes concentration in both external and pipette media was increased 5-fold (50 mM vs. 10 mM). When aspartate was substituted for Cl− or when 2 mM SITS was added to the external solution (in the absence of Ca2+ and Cd2+ because aspartate is known to chelate Ca2+ ions and possibly other divalent cations), ilo was reduced to a similar extent in the two cases and the difference current was composed of a peak (inactivation fitted by a single exponential) and a steady-state component. The SITS-sensitive transient current reversed at a potential close to ECl When 5 mM 9-anthracene carboxylic acid was added to external solution (in the presence of Ca2+ and Cd2+), the peak of the difference current was similar to that observed when Cl− was substituted by methanesulfonate. The difference current resulting from the substitution of methanesulfonate for chloride was not changed when the pipette solution contained either 50 mM EGTA (instead of 5 mM) or 10 mM EGTA and 10 mM BAPTA. The nature of Cs+- and 4-aminopyridine-sensitive transient outward current suppressed by chloride ion substitutes or chloride channel blockers is discussed
Unveiling hidden structures in the Coma cluster
We have assembled a large data-set of 613 galaxy redshifts in the Coma
cluster, the largest presently available for a cluster of galaxies. We have
defined a sample of cluster members complete to b, using a
membership criterion based on the galaxy velocity, when available, or on the
galaxy magnitude and colour, otherwise. Such a data set allows us to define
nearly complete samples within a region of 1~\Mpc\ radius, with a sufficient
number of galaxies per sample to make statistical analyses possible. Using this
sample and the {\em ROSAT} PSPC X--ray image of the cluster, we have
re-analyzed the structure and kinematics of Coma, by applying the wavelet and
adaptive kernel techniques. A striking coincidence of features is found in the
distributions of galaxies and hot intracluster gas. The two central dominant
galaxies, NGC4874 and NGC4889, are surrounded by two galaxy groups, mostly
populated with galaxies brighter than b and well separated in
velocity space. On the contrary, the fainter galaxies tend to form a single
smooth structure with a central peak coinciding in position with a secondary
peak detected in X--rays, and located between the two dominant galaxies; we
suggest to identify this structure with the main body of the Coma cluster. A
continuous velocity gradient is found in the central distribution of these
faint galaxies, a probable signature of tidal interactions rather than
rotation. There is evidence for a bound population of bright galaxies around
other brightest cluster members. Altogether, the Coma cluster structure seems
to be better traced by the faint galaxy population, the bright galaxies being
located in subclusters. We discuss this evidence in terms of an ongoing
accretion of groups onto the cluster.Comment: to appear in A&A, 19 pages, uuencoded gzipped postscript fil
Alien Registration- Lefevre, Marie May A. (Van Buren, Aroostook County)
https://digitalmaine.com/alien_docs/33327/thumbnail.jp
Equitable edge colored Steiner triple systems
A k-edge coloring of G is said to be equitable if the number of edges, at any vertex, colored with a certain color differ by at most one from the number of edges colored with a different color at the same vertex. An STS(v) is said to be polychromatic if the edges in each triple are colored with three different colors. In this paper, we show that every STS(v) admits a 3-edge coloring that is both polychromatic for the STS(v) and equitable for the underlying complete graph. Also, we show that, for v 1 or 3 (mod 6), there exists an equitable k-edge coloring of K which does not admit any polychromatic STS(v), for k = 3 and k = v - 2
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