PubMed · 13630350
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1959-01-10. [Infiltration].. https://pubmed.ncbi.nlm.nih.gov/13630350/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A double stranded DNA molecule when pulled with a force acting on one end of the molecule can become either partially or completely unzipped depending on the magnitude of the force F. For a random DNA sequence, the number M of unzipped base pairs goes as M approximately (F - Fc)(-2) and diverges at the critical force Fc with an exponent chi = 2. We find that when excluded volume effect is taken into account for the unzipped part of the DNA, the exponent chi = 2 is not changed but the critical force Fc is changed. The force versus temperature phase diagram depends on only two parameters in the model, the persistence length and the denaturation temperature. Furthermore a scaling form of the phase diagram can be found. This scaling form is parameter independent and depends only on the spatial dimension. It applies to all DNA molecules and should provide a useful framework for comparison with experiments.
Polymorphism and higher-order structures of even-number dicarboxylic acids from hexadecanedioic acid to eicosanedioic acid have been studied by micro-FTIR spectroscopy and microscopic observation. In order to obtain the three-dimensional structural information, the oblique transmission method was incorporated into a micro-FTIR spectrometer equipped with a couple of Cassegrain lenses. The IR spectra showed that the solid states of dicarboxylic acid bore a marked structural similarity to those of n-saturated fatty acids. It was found that a solution-grown single crystal of dicarboxylic acids was an aggregate of lamellae whose thickness exceeded by far their molecular length. The surfaces of lamellae were covered with hydrocarbon segments taking a hairpin structure, and the linkage of hydrogen-bonded dicarboxylic acids formed a folded chain structure. The result of oblique transmission measurements showed that the stacking mode of lamellae varied depending on crystallization conditions.
The equations of nematodynamics are formulated, solved, and used to model textural transformations in sheared thermotropic flow-aligning nematic polymers. The solutions are classified and characterized using analytical, scaling, and numerical methods. It is found that as the shear rate increases, the pathway between an oriented nonplanar state and an oriented planar state is through texture formation and coarsening. The two shear-rate dependent dimensionless numbers that control the texture formation and coarsening process are Ericksen Er and Deborah De numbers. The emergence of texture is independent of the Deborah number, and occurs at Er=10(4). As the shear rate increases and Er>10(4) the first texture that arises is a defect lattice. Further increases of the shear rate bring De close to 1, ignite the coarsening processes, and replace the defect lattice with a defect gas. The smallest texture length scale l(t) occurs at the defect lattice-defect gas transition. In the defect lattice regime the texture length scale decreases with increasing shear rate as l(t) proportional to (gamma-a)(-1/2), while in the defect gas regime it increases as l(t) proportional to (gamma-b sqrt[(gamma-a)]-c)(-1). Finally when De>2, an oriented monodomain state emerges, and the texture vanishes since coarsening overpowers defect nucleation. It is found that the texture transition cascade unoriented monodomain=>defect lattice=>defect gas=>oriented monodomain is remarkably consistent with the experimentally observed textural transitions of sheared lyotropic nematic polymers.