Studies of polyester fiber as carrier for microbes in a quantitative test method for disinfectants

Tests were conducted by a Task Force on Disinfectant Test Methods that was appointed to investigate controversies regarding the accuracy of AOAC test methods for disinfectants as presented in AOAC's Official Methods of Analysis, Chapter 6. The general principles for new and improved AOAC tests are discussed, and a disinfectant test using microbes labeled onto a polyester fiber surface is described. The quantitative test measures the survival of test microbes as a function of exposure time as well as the exposure conditions required to kill 6 log10 of the test microbes. The time required was similar to that for the kinetics of the kill of Bacillus subtilis-labeled cylinders as tested by methods of the AOAC Sporicidal Test 966.04.     

NOVEL POLYMER WIDE VIEWING ANGLE COMPENSATION FILMS FOR LIQUID CRYSTAL DISPLAYS(LCDS)

We report on generating uniaxial negative birefringent compensation films, made of specifically designedpolyimides. These polymers were synthesized via a polycondensation of dianhydride [such as 2, 2' -bis(3, 4-dicarboxyphenyl)hexafluoropropane dianhydride] and 2, 2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. The uniaxial negative birefringent (n_x =n_y > n_z) polyimide substrates are achieved using a solution-casting method in conventional solvents, which exhibit thedesirable optical phase retardation [(n_x - n_z)×d] values from 50 to 400 nm varying with the film thickness. In thesepolyimide films, the long chain rigid molecules adopt intrinsic planar orientaion. In detail, the majority of phenylene-imiderings and phenylenes preferentially adopt nearly planar conformations parallel to the film substrae. In addition, these filmsalso possess high transparency (or transmittance) and little color shift. The unique color dispersion curve indicates that thistype of materials is very suitable for the applications in LCDs due to an excellent mimic for the retardation color dispersioncurve with respect to LC molecules. Significantly low in-plane retardation (< 1 nm) allows this new technology based film toachieve sufficiently high contrast ratio while highly negative retardation dramatically suppresses the gray scale inversion toimprove the viewing angle performance in a variety of new mode LCDs.     

Fourier representation method for electronic structures of linear polymers

The Fourier representation method described in the previous paper of this series is used to make electronic structure calculations for a linear chain of equally spaced hydrogen atoms. The electronic wavefunction is assumed to be a determinant of doubly-occupied crystal orbitals of modulated-plane-wave type, built from one 1s Slater-type orbital of screening parameter ζ centered on each atom. The energy is calculated from the electrostatic zero-order Hamiltonian with exact evaluation of all Coulomb and exchange contributions, and is optimized with respect to the lattice spacing and ζ value. Good agreement with work by others is noted, indicating a near-equivalence of modulated-plane-wave and tight-binding wavefunctions for this half-filled-valence-band system. The linear chain is calculated to be far more stable than cubic three-dimensional hydrogen crystals. This fact sheds light on the unusually large calculated nearest-neighbor distances in the cubic crystals, and is related to a suggestion that under certain conditions the most stable structure for solid atomic hydrogen may be of lower symmetry than cubic. The previous paper of this series: Harris, F. E.: J. Chem. Phys.56, 4422 (1972) [1]. Chargé de Recherches du F.N.R.S. (Fonds National Belge de la Recherche Scientifique).     

Expedient solid-phase synthesis of fluorogenic protease substrates using the 7-amino-4-carbamoylmethylcoumarin (ACC) fluorophore

A highly efficient solid-phase synthesis method for the preparation of fluorogenic protease substrates based upon the bifunctional leaving group 7-amino-4-carbamoylmethylcoumarin (ACC) is reported. Methods for the large-scale preparation of the novel fluorogenic leaving-group ACC are provided (Scheme 1). Detailed procedures are also provided for loading a diverse set of amino acids to support-bound ACC in good yields and with minimal racemization. Finally, procedures are included for the preparative synthesis of optimized ACC substrates for HIV-1 protease and plasmin.     

In situ monitoring of solid-state polymerization reactions in sodium chloroacetate and sodium bromoacetate by 23Na and 13C solid-state NMR spectroscopy

The thermally induced solidstate polymerization reactions in sodium chloroacetate and sodium bromoacetate, leading to poly(hydroxyacetic acid) (polyglycolide) and NaCl and NaBr, respectively, were studied by isothermal in situ solid-state NMR spectroscopy at 120, 130 and 140 degrees C with a time resolution of the order of 5 to 25 min. The nuclei probed were 23Na and 13C, allowing the parent compounds (sodium halogenoacetates) and both reaction products (polymer and alkali halide) to be monitored. For sodium chloroacetate, there is no evidence for the involvement of intermediate phases during the reaction whereas this cannot be excluded for sodium bromoacetate. The crystal structure of sodium bromoacetate was determined directly from powder diffraction data by the Monte Carlo method, and was found to be isostructural with sodium chloroacetate. The topochemical reaction mechanism proposed previously for sodium chloroacetate is thus also applicable for the polymerization reaction in sodium bromoacetate. The mechanistic and kinetic information obtained from our in situ solid-state NMR investigations is compared and contrasted with information obtained from other in situ probes of the polymerization reactions in these materials.     

Hartree-like methods in electronic structure theory

We consider the “Hartree Problem,” here defined as the problem of finding the orthogonal one-electron states which in a single determinant minimize the electronic energy, excluding exchange contributions. These states may provide a useful basis for correlation-energy studies. It is shown how the “Hartree Problem,” although superficially not of pseudoeigenvalue form, can nevertheless be cast in such a form and solved by an iterative diagonalization process.