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Poly(phenylene ethynylene) (PPE) and a series of PPE derivatives were studied using Density Functional Theory- Tight Binding in order to generate molecular dynamics simulations in the gas phase. Dihedral angles between adja-cent phenylene units were measured over time to generate a histogram of conjugation lengths where conjugation length was defined by planarity. The average effective conjugation lengths for these polymers were extracted from this data. Notably, it was found that PPE with alkoxy substituents on the phenylene ring of each repeat unit are attributed with causing an increased average conjugation length relative to unsubstituted PPE from 4.7 to 6.4 repeat units. Comparatively, alkyl substituents caused a decrease in conjugation length to 4.5 repeat units. The methods developed here were extended to a wider series of PPE derivatives where a direct link was found between polymer planarity and the electron donating/withdrawing ability of substituents. These results indicate that the solvating sidechains frequently employed in conjugated polymers have an innate effect on the rigidity of the polymer backbone.
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Name: The journal of physical chemistry. A
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The primary purpose is to determine bioavailability of Bazedoxifene/conjugated estrogen formulations for future testing purposes.
To conduct a randomized, double-blind, controlled clinical trial to determine the independent and combined effects of dietary conjugated linoleic acid (CLA) and vitamin D supplementation o...
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The purpose of this study is to see if there is a racial and/or gender difference in platelet aggregation.
The formation of clumps of RED BLOOD CELLS under low or non-flow conditions, resulting from the attraction forces between the red blood cells. The cells adhere to each other in rouleaux aggregates. Slight mechanical force, such as occurs in the circulation, is enough to disperse these aggregates. Stronger or weaker than normal aggregation may result from a variety of effects in the ERYTHROCYTE MEMBRANE or in BLOOD PLASMA. The degree of aggregation is affected by ERYTHROCYTE DEFORMABILITY, erythrocyte membrane sialylation, masking of negative surface charge by plasma proteins, etc. BLOOD VISCOSITY and the ERYTHROCYTE SEDIMENTATION RATE are affected by the amount of erythrocyte aggregation and are parameters used to measure the aggregation.
A 9,10alpha-dihydro derivative of ERGOTAMINE that contains isopropyl sidechains at the 2' and 5' positions of the molecule.
Chemically stimulated aggregation of cell surface receptors, which potentiates the action of the effector cell.
Continuous involuntary sustained muscle contraction which is often a manifestation of BASAL GANGLIA DISEASES. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from MUSCLE SPASTICITY. (From Adams et al., Principles of Neurology, 6th ed, p73)
A collective term for a group of around nine geometric and positional isomers of LINOLEIC ACID in which the trans/cis double bonds are conjugated, where double bonds alternate with single bonds.