Disorientation of crystallites in highly stretched polyethylene

Crystallite orientation in polyethylene has been investigated in the high range of stretching. Crystallite disorientation can be observed in samples subjected to various stretching procedures: hot drawing and elongation of oriented fibers at room temperature at constant rate and at constant load. Crystallite disorientation does not take place during elongation but is induced upon removal of the applied stress. The higher the rate of removal of stress the greater is the disorientation. Two mechanisms are postulated for the disorientation: one relating to the irregular residual strain developed in fibrils by high stretching, and the other concerning rotational movement of crystallites caused by amorphous chains terminated on the interfaces. The fibrillation brought about by high stretching is thought to play an important role in the crystallite disorientation.     

Characterization of cellulose molecules in bio-system studied by modeling methods

Cellulose chains in bio-system were examined. A model system, in which molecular chains were fixed at one end in an aqueous environment, was analyzed as a model bio-system of cellulose. Five cellulose chains (DP = 40), whose one end was fixed (like a cantilever), were placed in 20.0 × 2.8 × 2.8 nm³ cell which was filled up with water molecules. This model cell was thoroughly annealed and then piled up three-dimensionally. The molecular dynamics simulation was applied to this model system at room temperature (298 K) with time step of 1.0 femto-second in AMBER force field with parameter sets for carbohydrates. The molecular motion of cellulose chains in cantilever condition was found to be more moderate compared with case of free chains. The water molecules around the cellulose chains were interrupted directly forming hydrogen bondings among the cellulose chains. This result suggests that degree of crystallinity of cellulose in bio-system is low. The result also reminds us that the cellulose chains are originally able to hold water molecules giving them a gel property, although dried cellulose is not soluble in water. Conformational and Packing Analysis of Polysaccharides, Part 4. Presented at 22nd International Carbohydrate Symposium, July 23–27, 2004.     

Non-adiabatic coupling constants for the disrotatory and conrotatory isomerization paths between butadiene and cyclobutene

The S₁S₀ non-adiabtic coupling constants were calculated for the disrotatory and conrotatory paths of the isomerization reaction between butadiene and cyclobutene. The calculated non-adiabatic coupling terms showed clearly the difference between the non-adiabatic interactions of the two reaction processes, and they correlate well with the Woodward-Hoffman rule.     

Formation of GeO2 nanosheets using water thin layers in lamellar phase as a confined reaction field--in situ measurement of SAXS by synchrotron radiation

Highly crystallized GeO2 nanosheets were synthesized by hydrolysis and condensation reactions of germanium alkoxide using a 2-dimensional flat thin lamellar phase water layer containing surfactant molecules at the liquid-liquid interface as a confined reaction field.     

Effect of evolved hydrogen fluoride on radiation-induced crosslinking and dehydrofluorination of poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVdF) was irradiated by ⁶⁰Co γ-rays with and without potassium hydroxide (KOH) under vacum. KOH tablets were added to absorb completely hydrogen fluoride (HF) which is the main volatile product of radiolysis of PVdF in the irradiation cell. In the presence of HF, the rates of radiation-induced crosslinking and dehydrofluorination of PVdF were lower than those in the absence of HF. The experimental results are discussed from the standpoint of stabilization of alkyl free radicals in PVdF by reaction with hydrogen fluoride.     

Drapeau theorem for differential systems

Generalizing the theorem for Goursat flags, we will characterize those flags which are obtained by “rank 1 prolongation” from the space of 1 jets for 1 independent and m dependent variables.     

Transition of nylon 6 γ-phase crystals by stretching in the chain direction

A crystal transition was found in nylon 6 fibers from the γ-phase to α-phase on stretching in the chain direction. The γ-phase fiber prepared by iodine treatment was stretched under constant load and the crystal deformation was observed by an x-ray method. The critical stress for the transition was estimated as 4 × 10³ kg./cm.² at room temperature. For this crystal transition the following conditions must be satisfied: (1) extension of the γ-phase chain to untwist the chain around the amide groups, (2) translational mobility of the chain to change the stacking in the crystallite. At the critical stress, the chain in the crystal is extended to nearly the same length as that of α-phase. The translational movement occurs under stress higher than about 3 × 10³ kg./cm.², and the pseudohexagonal cell is deformed into a monoclinic form. However, the monoclinic crystallites present at a stress lower than the critical value estimated above are unstable and may be brought back to the original form by head treatment at 100°C. No crystal transition occurs at low temperature.     

SOLVENT EFFECT ON SPHEROIDENE IN NONPOLAR AND POLAR SOLUTIONS AND THE ENVIRONMENT OF SPHEROIDENE IN THE LIGHT-HARVESTING COMPLEXES OF Rhodobacter sphaeroides 2.4.1 AS REVEALED BY THE ENERGY OF THE 1Ag−→1Bu+ ABSORPTION AND THE FREQUENCIES OF THE VIBRONICALLY COUPLED C=C STRETCHING RAMAN LINES IN THE 1Ag− AND 1Bu− STATES

Abstract –The ¹A_g^?→¹B_u⁺ electronic absorption band and the vibronically coupled, C=C stretching Raman lines in the ¹A_g^? and 2¹A_g^? states were recorded for spheroidene free in nonpolar and polar solvents as well as for spheroidene bound to the LH1 and LH2 complexes of Rhodobacter sphaeroides 2.4.1. The ¹B_u⁺ energy exhibited a linear dependence on R(n) = (n² - 1)/(n²+ 2) in both nonpolar and polar solvents; the line for polar solvents had a gentler slope and crossed the line for nonpolar solvents at R(n) = 0.3. The above characteristic of polar solvents was ascribed to the electric field generated by fluctuation of the solvent permanent dipoles; it stabilizes the ¹B_u⁺ energy and reduces the polarizability of the solvent. The vibronically coupled, C=C stretching frequencies in the ¹A_g^? and 2¹A_g^? states [ν(A_g) and [ν(2A_g)] also showed similar dependence on R(n), which is explained in terms of vibronic coupling among the ¹A_g^?, 2¹A_g^? and 3¹A_g^? states. The environment of spheroidene in the LH2 and LH1 complexes was assessed on the basis of the ¹B_u⁺ energy and the ν(A_g) and [ν(2A_g) frequencies: Spheroidene in the LH2 complex is located in an environment with high polarizability, while spheroidene in the LH1 complex is located in an environment with lower polarizability.     

Generation of Nearly Diffraction-Free Beams Using a New Optical System

A new optical system which can efficiently generate the nearly diffraction-free beams is proposed and its characteristics are investigated by numerical analysis. This optical system consists of a new optical element called a DCC (double-concave-cone) lens and an objective lens with a large numerical aperture, and can generate the Bessel beam and also the Bessel-Gauss beam. The maximum propagation distance of nearly diffraction-free beams generated by the system agrees with its theoretical value for the Bessel beam.     

Adsorption behavior of trivalent americium and rare earth ions onto a macroporous silica-based isobutyl-BTP/SiO2-P adsorbent in nitric acid solution

To separate minor actinides from high level liquid waste (HLLW) of PUREX reprocessing, a silica-based macroporous isobutyl-BTP/SiO₂-P adsorbent was synthesized by impregnating isobutyl-BTP (2,6-di(5,6-diisobutyl-1,2,4-triazin-3-yl)pyridine) extractant into the macroporous SiO₂-P support with a mean diameter of 60 μm. A partitioning process using extraction chromatography for the treatment of HLLW was designed consisting five separation columns. As a partly work focused on isobutyl-BTP/SiO₂-P separation column, adsorption behavior of ²⁴¹Am and trivalent rare earth (RE) from simulated HLLW onto silica-based isobutyl-BTP/SiO₂-P adsorbent was investigated by batch method. Meanwhile, the chemical and radiolytic stabilities of isobutyl-BTP/SiO₂-P adsorbent against 0.01 M HNO₃ solution and γ-ray irradiation were studied. It was found that isobutyl-BTP/SiO₂-P adsorbent exhibited good adsorption selectivity for ²⁴¹Am over RE(III) in 0.01 M HNO₃ solution and showed weak or no adsorption affinity to light and middle RE(III) groups. In addition, in stability experiments, isobutyl-BTP adsorbent showed excellent stability against 0.01 M HNO₃ solution and γ-ray irradiation over 4 months contact time.