12,727 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
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
Performance Analysis of a Dual-Hop Cooperative Relay Network with Co-Channel Interference
This paper analyzes the performance of a dual-hop amplify-and-forward (AF) cooperative relay network in the presence of direct link between the source and destination and multiple co-channel interferences (CCIs) at the relay. Specifically, we derive the new analytical expressions for the moment generating function (MGF) of the output signal-to-interference-plus-noise ratio (SINR) and the average symbol error rate (ASER) of the relay network. Computer simulations are given to confirm the validity of the analytical results and show the effects of direct link and interference on the considered AF relay network
Research of thoracolumbar spine lateral vascular anatomy and imaging
This study introduces an anatomical basis for surgeries such as thoracoscopeassisted
thoracolumbar spinal anterior interbody fusion in terms of image observing
and corpse specimen anatomising. The observation of the 3-dimensional
computed tomography (CT) image indicates that segmental arteries are
visible and run in the central supersulcus of the corresponding vertebral body’s
side, while the branches are invisible. The distances between adjacent segmental
arteries in T10/11, T11/12, T12/L1, L1/2, and L2/3 are 23.35 ± 1.48, 25.61 ± 2.08,
29.12 ± 2.30, 32.53 ± 2.18, and 33.73 ± 2.29 (mm), respectively. And the
observation by the thoracolumbar spine side of the adult corpse specimens
shows that segmental arteries and veins constantly exist and run in the central
supersulcus of the corresponding vertebral body’s side; each segmental artery
has some small branches; the zone between the upper and lower segmental
arteries form a relatively non-vascular nerve safe zone, where the intervertebral
space (disc) locates. The distances between adjacent segmental arteries in T10/11,
T11/12, T12/L1,L1/2,L2/3 are 23.34 ± 0.78, 25.54 ± 0.85, 29.11 ± 1.01, 32.82 ±
± 1.28, and 33.71 ± 1.42 (mm), respectively. The safe zone, with the intervertebral
disc as the reference mark, can provide enough operation space for surgeries
like thoracoscope-assisted anterior interbody fusion and reducing damage
to blood vessels as well as surgical complications. Additionally, the arrangement
and distribution of segmental arteries can be clearly displayed on
the 3-dimensional CT image and the result is basically consistent with that of
corpse specimens. Therefore, the 3-dimensional CT image can be regarded as
the reference for video-assisted thoracoscopic surgery plans. (Folia Morphol
2010; 69, 3: 128-133
Monte Carlo simulation of melting transition on DNA nanocompartment
DNA nanocompartment is a typical DNA-based machine whose function is
dependent of molecular collective effect. Fundamental properties of the device
have been addressed via electrochemical analysis, fluorescent microscopy, and
atomic force microscopy. Interesting and novel phenomena emerged during the
switching of the device. We have found that DNAs in this system exhibit a much
steep melting transition compared to ones in bulk solution or conventional DNA
array. To achieve an understanding to this discrepancy, we introduced DNA-DNA
interaction potential to the conventional Ising-like Zimm-Bragg theory and
Peyrard-Bishop model of DNA melting. To avoid unrealistic numerical calculation
caused by modification of the Peyrard-Bishop nonlinear Hamiltonian with the
DNA-DNA interaction, we established coarse-gained Monte Carlo recursion
relations by elucidation of five components of energy change during melting
transition. The result suggests that DNA-DNA interaction potential accounts for
the observed steep transition.Comment: 12 pages, 5 figure
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