Birefringence studies

The compensation birefringence measurement is very easily coupled to optical microscopy in the transmission and reflection modes, thus allowing characterizing orientation with a spatial resolution of a few hundreds of nanometers [14]. Polarizing microscopes are widely available and are often used for birefringence studies even if spatial resolution is not required. Objectives specifically designed for cross-polarized microscopy are necessary to avoid artifacts. 

Dynamic Light Scattering and Transient Electric Birefringence Study of Poly(vinyI chloride) Micrc els... 

A final piece of evidence against both finite extensibility and internal viscosity is provided by flow birefringence studies. One would expect each to produce variations in the stress optical coefficient with shear rate, beginning near the onset of shear rate dependence in the viscosity (307). Experimentally, the stress-optical coefficient remains constant well beyond the onset of shear rate dependence in r for all ranges of polymer concentration (18,340). 

Transmission electron microscopy (TEM) and birefringence studies of strained and/ or fractured epoxies have revealed more direct experimental evidence that molecular flow can occur in these glasses. Films of DGEBA-DETA ( 11 wt.- % DETA) epoxies, 1 pm thick, were strained directly in the electron microscope and the deformation processes were observed in bright-field TEM 73 110). Coarse craze fibrils yielded in-homogeneously by a process that involved the movement of indeformable 6-9 tan diameter, highly crosslinked molecular domains past one another. The material between such domains yielded and became thinner as plastic flow occurred. 

D.F. Nicoli, J.G. Elias and D. Eden, Transient electric birefringence study of CTAB micelles implications for rodlike growth, J. Phys. Chem. 85 (1981) 2866-2869. 

Colloidal dispersions suspensions and aggregates Viscosity and transient electric birefringence study of clay colloidal aggregation. Physical Review E 65, 21407-21500... 

S. R. Galante and P. L. Frattini, Spatially resolved birefringence studies of planar entry flow, J. Non-Newt. Fluid Mech., 47, 289 (1993). 

P. N. Dunlap and L. G. Leal, Dilute polystyrene solutions in extensional flow birefringence and flow modification, J. Non-Newt. Fluid Mech., 23, 5 (1987). E. Geffroy and L. G. Leal, Flow birefringence studies of a concentrated polystyrene solution in a two-roll mill. 1. Steady flow and start-up of steady flow, J. Polym. Sci., Polym. Phys., 30,1329 (1992). 

DAHP synthetase, 251, 255 Dehydroquinase, 258 Dehydroshikimate riductase, 259 Dextrans, 341 acid hydrolysis of, 349 chain lengths of, 345, 346 cuprammonium complexes of, 355 electron microscope studies on, 349 enzymic synthesis of, 342, 345, 355 from sucrose, 342 flow birefringence studies on, 349 fructose-containing, 359 infrared absorption spectra of, 352 isolation of, 343... 

Flavonoids, biosynthesis of, 268 Flow birefringence, studies on dextran, 349... 

In the purpose of comparisons between theory emd experiments, this short review points out the need for significant experimental studies related to flow patterns, pressure drops and extrudate swell ratios for polymer melts characterized in shear and elongation. Streamlines, velocity components and stress fields related to flow birefringence studies should be used to validate numerical simulations of entry and exit flows. Progress in flow computations in domains involving the upstream and downstream channels together with the exit region are also necessary. 

Tiselius, again using suitably cut plates of heulandite, established actual concentration gradients from birefringence studies as a function of distance x from the surface. If the concentration at f = 0 is Co throughout the crystal, and at time t is at distance x while at x = 0, c = for all t > 0, then... 

Transition temperatures and heats were obtained from differential heating and cooling curves both at atmospheric and higher pressures by Goranson and Kracek (7). Existence of three phases is confirmed by the earlier birefringence studies of Boeke (8 ). 

Palmer DC (1994) Stuffed derivatives of the silica polymorphs. Rev Mineral 29 83-122 Palmer DC, Bismayer U, Salje EKH (1990) Phase transitions in leucite order parameter behavior and the Landau potential deduced from Raman spectroscopy and birefringence studies. Phys Chem Minerals 17 259-265... 

Specimen Preparation. Specimens for tensile and birefringence studies were prepared from sheets molded at about 200 C between stainless steel platens to the appropriate thickness. 

Lewis BA et al (1985) Magnetic birefringence studies of dilute purple membrane suspensions. Biophys 147(2) 143-150... 

Lowering the temperature increases Szz for all systems to the same limiting value of Szz 0.65 in the nematic phase [35, 99, 100]. Note, that the order parameter curve of polymer 1 exhibits a horizontal slope at the glass transition. A further jump of Szz. observed for the polymers 2, indicates an additional smectic A phase with a limiting value of Szz 0.9. No such discontinuity is detected for the monomeric liquid crystal 5, exhibiting a smectic A phase, likewise. Comparison of the order parameters of Fig. 17 with those of NMR [108-110] and birefringence studies... 

Hu, Y, Wang, S. Q., and Jamieson, A. M., Rheological and flow birefringence studies of a shear-thickening complex fluid a surfactant model system, /. RheoL, 37,531-546 (1993b). 

Polarized light is generally required, however, for birefringence studies. The strongest interference colors is observed when the birefringent sample is at an angle of 45° to the oscillation direction of the polarizers. The order of the interference colors depends on the thickness of the sample and the difference in the refractive indices parallel and perpendicular to the strain direction. Refractive indices are determined by immersing the samples in inert liquids of known refractive index. 

J. C. Bemengo, B. Roux, and D. Herbage, Electrical Birefringence Study of Monodisperse Collagen Solutions, Biopolymers 13, 641-647 (1974). 

Transient electric birefringence study of rod-shaped water-in-oil microemulsions, Langmuir 14, 1-7 (1998). 

Ritacco H, Kurlat D, Langevin D (2003) Propoties of aqueous solutions of polyelectrolytes and surfactants of opposite charge surface tension, surface theology, and electrical birefringence studies. J Phys Chem B 107 9146... 

The cells of all five polymer concentrations were used for the birefringence study with the light of an He Ne laser. The polarizer and analyzer were crossed, and the cell was aligned so that the rubbing direction (director field it) was tilted by 45° with respect to the polarizer and analyzer. 

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