2,643 research outputs found
Wigner crystal model of counterion induced bundle formation of rod-like polyelectrolytes
A simple electrostatic theory of condensation of rod-like polyelectrolytes
under influence of polyvalent ions is proposed. It is based on the idea that
Manning condensation of ions results in formation of the Wigner crystal on a
background of a bundle of rods. It is shown that, depending on a single
dimensionless parameter, this can be the densely packed three-dimensional
Wigner crystal or the two-dimensional crystal on the rod surfaces. For DNA the
location of charge on the spiral results in a model of the one-dimensional
Wigner crystal. It is also argued that the Wigner crystal idea can be applied
to self-assembly of other polyelectrolytes, for example, colloids and DNA-lipid
complexes.Comment: 4 pages; typos corrected, references adde
Characterizing renewable energy compound events across Europe using a logistic regression-based approach
Can Strong Gravitational Lensing Constrain Dark Energy?
We discuss the ratio of the angular diameter distances from the source to the
lens, , and to the observer at present, , for various dark
energy models. It is well known that the difference of s between the
models is apparent and this quantity is used for the analysis of Type Ia
supernovae. However we investigate the difference between the ratio of the
angular diameter distances for a cosmological constant,
and that for other dark energy models,
in this paper. It has been known that there is
lens model degeneracy in using strong gravitational lensing. Thus, we
investigate the model independent observable quantity, Einstein radius
(), which is proportional to both and velocity
dispersion squared, . values depend on the parameters
of each dark energy model individually. However, for the various dark energy models, is well within
the error of for most of the parameter spaces of the dark energy
models. Thus, a single strong gravitational lensing by use of the Einstein
radius may not be a proper method to investigate the property of dark energy.
However, better understanding to the mass profile of clusters in the future or
other methods related to arc statistics rather than the distances may be used
for constraints on dark energy.Comment: 15 pages, 13 figures, Accepted in PR
Supernovae Ia Constraints on a Time-Variable Cosmological "Constant"
The energy density of a scalar field with potential , , behaves like a time-variable cosmological
constant that could contribute significantly to the present energy density.
Predictions of this spatially-flat model are compared to recent Type Ia
supernovae apparent magnitude versus redshift data. A large region of model
parameter space is consistent with current observations. (These constraints are
based on the exact scalar field model equations of motion, not on the widely
used time-independent equation of state fluid approximation equations of
motion.) We examine the consequences of also incorporating constraints from
recent measurements of the Hubble parameter and the age of the universe in the
constant and time-variable cosmological constant models. We also study the
effect of using a non-informative prior for the density parameter.Comment: Accepted for publication in Ap
Collapse of Stiff Polyelectrolytes due to Counterion Fluctuations
The effective elasticity of highly charged stiff polyelectrolytes is studied
in the presence of counterions, with and without added salt. The rigid polymer
conformations may become unstable due to an effective attraction induced by
counterion density fluctuations. Instabilities at the longest, or intermediate
length scales may signal collapse to globule, or necklace states, respectively.
In the presence of added-salt, a generalized electrostatic persistence length
is obtained, which has a nontrivial dependence on the Debye screening length.Comment: 4 pages RevTex, 3 ps figures included using epsf, final version as
appeared in PR
High-Frequency Oscillations in a Solar Active Region observed with the Rapid Dual Imager
High-cadence, synchronized, multiwavelength optical observations of a solar
active region (NOAA 10794) are presented. The data were obtained with the Dunn
Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly
developed camera system : the Rapid Dual Imager. Wavelet analysis is undertaken
to search for intensity related oscillatory signatures, and periodicities
ranging from 20 to 370 s are found with significance levels exceeding 95%.
Observations in the H-alpha blue wing show more penumbral oscillatory phenomena
when compared to simultaneous G-band observations. The H-alpha oscillations are
interpreted as the signatures of plasma motions with a mean velocity of 20
km/s. The strong oscillatory power over H-alpha blue-wing and G-band penumbral
bright grains is an indication of the Evershed flow with frequencies higher
than previously reported.Comment: 9 pages, 9 figure
Effective affinities in microarray data
In the past couple of years several studies have shown that hybridization in
Affymetrix DNA microarrays can be rather well understood on the basis of simple
models of physical chemistry. In the majority of the cases a Langmuir isotherm
was used to fit experimental data. Although there is a general consensus about
this approach, some discrepancies between different studies are evident. For
instance, some authors have fitted the hybridization affinities from the
microarray fluorescent intensities, while others used affinities obtained from
melting experiments in solution. The former approach yields fitted affinities
that at first sight are only partially consistent with solution values. In this
paper we show that this discrepancy exists only superficially: a sufficiently
complete model provides effective affinities which are fully consistent with
those fitted to experimental data. This link provides new insight on the
relevant processes underlying the functioning of DNA microarrays.Comment: 8 pages, 6 figure
The periodic variations of a white-light flare observed with ULTRACAM
High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited,
standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being
due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection)
- …