210,661 research outputs found
The effect of asymmetry of the coil block on self-assembly in ABC coil-rod-coil triblock copolymers
Using the self-consistent field approach, the effect of asymmetry of the coil
block on the microphase separation is focused in ABC coil-rod-coil triblock
copolymers. For different fractions of the rod block , some stable
structures are observed, i.e., lamellae, cylinders, gyroid, and core-shell
hexagonal lattice, and the phase diagrams are constructed. The calculated
results show that the effect of the coil block fraction is
dependent on . When , the effect of asymmetry of
the coil block is similar to that of the ABC flexible triblock copolymers; When
, the self-assembly of ABC coil-rod-coil triblock copolymers
behaves like rod-coil diblock copolymers under some condition. When continues to increase, the effect of asymmetry of the coil block reduces.
For , under the symmetrical and rather asymmetrical
conditions, an increase in the interaction parameter between different
components leads to different transitions between cylinders and lamellae. The
results indicate some remarkable effect of the chain architecture on
self-assembly, and can provide the guidance for the design and synthesis of
copolymer materials.Comment: 9 pages, 3 figure
Constraints on the Inner Cluster Mass Profile and the Power Spectrum Normalization from Strong Lensing Statistics
Strong gravitational lensing is a useful probe of both the intrinsic
properties of the lenses and the cosmological parameters of the universe. The
large number of model parameters and small sample of observed lens systems,
however, have made it difficult to obtain useful constraints on more than a few
parameters from lensing statistics. Here we examine how the recent WMAP
measurements help improve the constraining power of statistics from the radio
lensing survey JVAS/CLASS. We find that the absence of theta>3'' lenses in
CLASS places an upper bound of beta<1.25 (1.60) at 68% (95%) CL on the inner
density profile, rho \propto r^{-beta}, of cluster-sized halos. Furthermore,
the favored power spectrum normalization is sigma_8 >= 0.7 (95% CL). We discuss
two possibilities for stronger future constraints: a positive detection of at
least one large-separation system, and next-generation radio surveys such as
LOFAR.Comment: Scatter in concentration included; virial mass used consistently; new
Fig 3. Final version published in ApJ
Effect of polymer concentration and length of hydrophobic end block on the unimer-micelle transition broadness in amphiphilic ABA symmetric triblock copolymer solutions
The effects of the length of each hydrophobic end block N_{st} and polymer
concentration \bar{\phi}_{P} on the transition broadness in amphiphilic ABA
symmetric triblock copolymer solutions are studied using the self-consistent
field lattice model. When the system is cooled, micelles are observed, i.e.,the
homogenous solution (unimer)-micelle transition occurs. When N_{st} is
increased, at fixed \bar{\phi}_{P}, micelles occur at higher temperature, and
the temperature-dependent range of micellar aggregation and half-width of
specific heat peak for unimer-micelle transition increase monotonously.
Compared with associative polymers, it is found that the magnitude of the
transition broadness is determined by the ratio of hydrophobic to hydrophilic
blocks, instead of chain length. When \bar{\phi}_{P} is decreased, given a
large N_{st}, the temperature-dependent range of micellar aggregation and
half-width of specific heat peak initially decease, and then remain nearly
constant. It is shown that the transition broadness is concerned with the
changes of the relative magnitudes of the eductions of nonstickers and solvents
from micellar cores.Comment: 8 pages, 4 figure
Beam energy dependence of Hanbury-Brown-Twiss radii from a blast-wave model
The beam energy dependence of correlation lengths (the Hanbury-Brown-Twiss
radii) is calculated by using a blast-wave model and the results are comparable
with those from RHIC-STAR beam energy scan data as well as the LHC-ALICE
measurements. A set of parameter for the blast-wave model as a function of beam
energy under study are obtained by fit to the HBT radii at each energy point.
The transverse momentum dependence of HBT radii is presented with the extracted
parameters for Au + Au collision at 200 GeV and for Pb+Pb
collisions at 2.76 TeV. From our study one can learn that particle emission
duration can not be ignored while calculating the HBT radii with the same
parameters. And tuning kinetic freeze-out temperature in a range will result in
system lifetime changing in the reverse direction as it is found in RHIC-STAR
experiment measurements.Comment: 9 pages, 9 figure
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