Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. IV. Crystal orientation mechanism of nylon-6 under uniaxial stretching

A model relating crystal orientation to the deformation of nylon-6 spherulites under uniaxial stretching is discussed in terms of the orientation distribution functions of reciprocal lattice vectors of crystal planes, such as the (002) and (200) planes. The distribution functions calculated from the model are compared with those obtained from x-ray diffraction experiments. It is found that the crystal a axis and, consequently, the direction of hydrogen bonds within the crystal (α modification) orient parallel to the lamellar axis in the undeformed state, and that the crystal orientation behavior of nylon-6 is much different from that of low-density polyethylene, being characterized by much smaller values of the reorientation parameters of crystallites within orienting lamellae. Moreover, small-angle light scattering for H_v and V_v polarization is also calculated on the basis of the spherulite deformation model by taking the nylon-6 crystal as having orthogonal–biaxial symmetry in optical anisotropy. It is concluded that the H_v scattering can be realized in terms of the proposed model for spherulite deformation by taking into account a considerable contribution of hydrogen bonds to the molecular polarizability, so as to make the polarizability along the crystal a axis larger than that along the b axis. In other words, this conclusion suggests positively birefringent spherulites in the nylon-6 samples studied.     

Synthesis of perfluorobicyclic ethers

The electrochemical fluorination of cycloalkyl-substituted acetic and propionic acids were conducted to obtain several kinds of perfluorobicyclic ethers [reaction conditions: Anodic current density: 3.5 A/dm², Volt: 5～8V, Temp: 5～6 °C] . For example, from cyclopentyl-substituted acetic acids, perfluoro(4-alkyl-2-oxabicyclo[3.3.0]octane)s (I) were formed as the cyclization products in yields of 10～19% together with the corresponding perflouroalkanoyl flourides (II) (Y=3～13%).

While, perfluorospiro-ethers were obtained from the fluorination of 3-cycloalkyl-substituted propionic acids. The characterization of these perfluorobicyclic ethers which consists of the reaction with anhydrous aluminum chloride will be reported also.     

On a first-passage problem for a cumulative process with exponential decay

A first-passage problem for a cumulative process is investigated. The cumulative process is assumed to be generated by a Poisson process, and the amplitude generated by an event is assumed to decay exponentially. An integral equation for the probability density of the first-passage time until the total amplitude exceeds a pre-specified threshold level is derived. The Laplace transform of the probability density of the first-passage time is obtained explicity when each amplitude generated by an event is distributed exponentially. The mean first-passage times are given in a closed form and plotted versus the threshold level.     

Purely periodic -expansions with Pisot unit base

Let 1$"> be a Pisot unit. A family of sets defined by a -numeration system has been extensively studied as an atomic surface or Rauzy fractal. For the purpose of constructing a Markov partition, a domain constructed by an atomic surface has appeared in several papers. In this paper we show that the domain completely characterizes the set of purely periodic -expansions.

     

General description of mechanical anisotropy of semicrystalline polymers in relation to orientation of structural units composed of crystalline and noncrystalline materials

A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single-phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two-phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements.     

Development of an on-line immobilized-enzyme reversed-phase HPLC method for protein digestion and peptide separation

This paper describes use of a novel glass bead-based immobilized-enzyme micro column for simple and swift on-line protein digestion then peptide separation by reversed-phase HPLC. The inexpensive and easily made immobilized-enzyme micro column was prepared from aminopropyl controlled-pore glass that was reacted first with glutaraldehyde then with trypsin in the presence of phosphate buffer. Tryptic digestion of bovine serum albumin (BSA) was achieved simply by passing pretreated protein solution through the laboratory made immobilized-trypsin column; the tryptic fragments were then separated by reversed-phase HPLC. The peptide separation was found to be identical to separation of a sample which had undergone conventional enzymatic protein digestion in solution. Digestion of BSA by the immobilized-trypsin column decreased with increasing flow rate of the solution through the column, and 1.0 μL min⁻¹ was found to be the optimum flow rate for on-line protein digestion with our system. It was also found that the sample required pretreatment with urea before injection, because of a change in the properties of the protein in the presence of urea, and the immobilized-trypsin column lost its function in the presence of acetonitrile. This on-line proteomics system enables simple and rapid protein digestion and was successfully applied to partially micro two-dimensional (2D) chromatographic separation of proteins.     

Electron-boson coupling and oxygen-isotope effect in the optical conductivity of high-Tc superconductors

We have investigated electron-boson coupling in the optical conductivity of high-T_c superconductors through the optical self-energy. The real part of the self-energy (ReΣ^op(ω)) of YBa₂Cu₃O_y (YBCO) shows a characteristic doping dependence. In the optimally doped YBCO, ReΣ^op(ω) has a single peak around 65 meV, which corresponds to the kink structure of the band dispersion. On the other hand, in the under-doped YBCO, the peak structure of ReΣ^op(ω) splits into two parts. To evaluate contribution from the phonons in electron-boson coupling, we have measured oxygen-isotope effects by substituting ¹⁶O→¹⁸O for the optimally doped and under-doped YBCO.     

Synthesis and photophysical properties of azuleno[1′,2′:4,5]pyrrolo[2,1-b]quinazoline-6,14-diones: Azulene analogs of tryptanthrin

Azulene analog of tryptanthrin, azuleno[1′,2′:4,5]pyrrolo[2,1-b]quinazoline-6,14-dione, was successfully prepared by the condensation reaction of azuleno[2,1-b]pyrrole-2,3-dione with isatoic anhydride in the presence of sodium hydride or diisopropylethylamine (DIPEA). Its 2-halo derivatives were also obtained in high yields by the condensation reaction with 5-haloisatoic anhydrides in the presence of DIPEA. Reactivity toward electrophilic reagents was revealed by halogenation with N-bromosuccinimide (NBS) or N-iodosuccinimide (NIS) to afford 12-halo derivatives in high yields. Among the halo derivatives, 2-iodo and 12-iodo derivatives were reactive enough to afford phenylethynyl derivatives under Pd-catalyzed Sonogashira cross-coupling conditions. Within the phenylethynyl derivatives, only 12-phenylethynyl derivative was transformed into its 1,1,4,4-tetracyanobutadiene (TCBD) derivative by the reaction with TCNE. Amphoteric redox properties of the novel azulene analogs of tryptanthrin were characterized by spectroscopic and voltammetric analyses.     

UPLC-MS/MS detection of disaccharides derived from glycosaminoglycans as biomarkers of mucopolysaccharidoses

Mucopolysaccharidoses (MPSs) are a group of disorders resulting from primary defects in lysosomal enzymes involved in the degradation of glycosaminoglycans (GAGs). Depending on the specific enzyme defect, the catabolism of one or more GAGs is blocked leading to accumulation in tissues and biological fluids. GAG measurements are important for high-risk screening, diagnosis, monitoring treatment efficacy, and patient follow up. The dimethylmethylene blue (DMB) spectrophotometric method commonly used in most biochemical genetics laboratories relies on a non-specific total GAG analysis which has led to false positive results, and even false negative results (mainly for MPS III and IV patients). The main objective of our project was to devise and validate a reliable tandem mass spectrometry multiplex analysis for the urine quantitation of four GAGs (dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and chondroitin sulfate (CS)) for an eventual technological transfer to the clinic. The developed methodology is rapid (7 min) and our results showed good intraday and interday precision (RSDs ≤ 8.7%) and accuracy (Biases range: −12.0%–18.4%). Linearity was good (r² > 0.995) for DS, HS, CS, and KS calibration curves. In comparison with the DMB spectrophotometric method, this multiplex tandem mass spectrometry method allows GAG fractionation, thus a differentiation of MPS types, except for MPS I and II which are characterized by the same GAG profile. The devised method is a useful and reliable tool for diagnosis of MPS patients, as well as their monitoring and follow up, as shown by longitudinal studies.