Diamagnetic anisotropy and rotational viscosity of 6CHBT nematic liquid crystal

Nematic liquid crystal with polar terminal NCS group was studied by using acoustic and electro-optical methods. Experimental results on rotational viscosity have been obtained by two methods. The anisotropy of diamagnetic susceptibility of the studied LC with temperature variation was determined based on the comparison of these methods. The present results may be useful for testing physical models of the orientation dynamics of nematic liquid crystals in alternating electric and magnetic fields.

Study on the Mechanism of Magnetic Paraffin Control of Crude Oil Based on the Reorientation of Paraffin Crystals Induced by Magnetic Field

The wax deposition during pipeline transportation impedes the flow of crude oil and eventually blocks the pipelines. Magnetic paraffin control (MPC) technology has been extensively adopted for its advantage in energy-saving and pollution reduction. In order to clarify the scientific essence of MPC problem, energy transition mechanism of paraffin control has been investigated based on the theory of molecular reorientation. Meanwhile, the mechanism of magnetic orientation of paraffin crystals was also studied in detail. Results show that diamagnetic anisotropy is the fundamental cause for which diamagnetic paraffin molecules can respond to magnetic field. Furthermore, magnetic-field-induced rotation of paraffin molecules could be remarkably enhanced by the ordered structure of paraffin molecules, such as liquid lamellar structures and paraffin crystallites, which could make it possible to overcome energy barrier and induce the orientation of paraffin molecules. In addition, the effect of magnetic orientation on the formation of paraffin crystal network was also investigated detailedly, and a novel MPC mechanism based on magnetic orientation of paraffin crystal was proposed. This research is of great significance to improve the paraffin control technology and its theoretical principle in our country.

The Diamagnetic Susceptibility of the Tubulin Dimer

An approximate value of the diamagnetic anisotropy of the tubulin dimer, Δχdimer, has been determined assuming axial symmetry and that only the α-helices and β-sheets contribute to the anisotropy. Two approaches have been utilized: (a) using the value for the Δχα for an α-helical peptide bond given by Pauling (1979) and (b) using the previously determined anisotropy of fibrinogen as a calibration standard. The Δχdimer≈4×10-27 JT−2 obtained from these measurements are similar to within 20%. Although Cotton-Mouton measurements alone cannot be used to estimate Δχ directly, the value we measured, CMdimer=1.41±0.03×10-8 T−2cm2mg−1, is consistent with the above estimate for Δχdimer. The method utilized for the determination of the tubulin dimer diamagnetic susceptibility is applicable to other proteins and macromolecular assemblies as well.