Effect of the degree of extension on the phase composition and tendency toward mesomorphism of UHMWPE in gel-spun oriented fibers

Structural transformations of UHMWPE-based fibers prepared by orientational drawing have been studied by the combination of SAXS and WAXS methods, photo- and diffractometry, and isometric DSC measurements in a wide temperature range. A sequence of phase transformations and other structural changes has been followed and identified during the orientational deformation of the fibers in a wide range of draw ratios from 1 to 85 within the temperature interval from room temperature to the melting temperature of the polymer.     

Water-vapor absorption spectrum in the 0.59-μm region

The paper gives the results of investigation of the water-vapor absorption spectrum in the range of 586.9–596.6 nm. In the given range, 282 water-vapor absorption lines were recorded and were identified as belonging to the bands 4ν₁ + ν₃, 3ν₁ + 2ν₂ + ν₃, 3ν₁ + 2ν₃. Theoretical justification of the technique for interpreting the observed spectrum was made. The values of more vibration-rotation levels of energy were determined: for state (401) up to J = 10, for state (321) up to J = 10, and for state (302) up to J = 8. The rotational and centrifugal constants of the reduced Watson's Hamiltonian for the vibrational states (401), (321), (302), and (222) and constants of Fermi resonance (401)-(321), (302)-(222), and Coriolis resonance between the states (401), (321), and (302), (222) were determined.     

Rotational instability of filamentary crystals undergoing plastic deformation

We investigated the kinetics of spontaneous torsion in filamentary crystals during plastic deformation by a tensile load. The nature of the observed effect is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 76–81, August, 1988.     

Characterization of periodic domain structures in lithium niobate crystals by scanning electron microscopy and X-ray diffraction analysis

Congruent lithium niobate crystals with periodic domain structures formed by the method of thermoelectric postgrowth treatment have been investigated. Periodic domain structures in the samples of polar ZY-, YZ-, and YX-cuts were characterized by scanning electron microscopy, high resolution x-ray diffractometry, and topography. The evaluation and comparison of the secondary electron (SE) signal cycling, electron emission coefficient, and charge value to equalize the differences in the SE signal have allowed us to specify the features of ZY-and YZ-cut structures. A correlation between the crystal lattice distortions near domain boundaries and the type of domain walls has been found. The domain walls separating the areas with the tail-to-tail P _s vectors not only cause stronger crystal lattice distortions near them, but also are charged less quickly under electron irradiation.     

Light scattering in a finite multi-particle system

We use the discrete dipole approximation (DDA) to perform electromagnetic scattering calculations of particles in a 3D volume. We adjust the spacing between the particles to change the volume densities of the scattering systems from approximately 10% to 100%. For very large volume densities, e.g. >50%, it is difficult to assign unambiguously whether the system is composed of a single heterogeneous particle or of multiple particles. Our calculations demonstrate optical effects attributable to multiple scattering in systems having volume densities as high as ～90%. This suggests that heterogeneities within naturally occurring particle systems can produce multiple-scattering effects. We also see evidence of very deep negative polarization branches (NPBs) (～?6%) that may have implications in interpreting polarization phase curves of cometary circumnuclear halos.