Optical components from a new vitrifying liquid crystal

New low molar mass liquid crystalline vitrifying materials have been synthesized and tested for application in optical films. The molecules were based on spiro compounds derived from pentaerythritol and mesogenic groups derived from cyanobiphenylyl moieties. The resulting materials showed glass transition temperatures as high as 85 degrees C and nematic to isotropic phase transition temperatures up to 222 degrees C. Crystallization from the melt was strongly suppressed. Well-aligned, solid, birefringent layers were obtained from the materials by spincoating. Uniaxially oriented layers with an optic axis tilted with respect to the substrate were obtained by spincoating the liquid crystals on pretilt amplification layers. When an anisotropic dye was incorporated in the liquid crystals, polarizers with a tilted absorption axis were obtained. In addition, the compounds were found to be suitable as hosts for photo-induced reorientation of photo-isomerizable dyes.     

Microwave rotational spectra of the Kr-NH3 van der Waals complex

Rotational spectra of the Kr-NH₃ van der Waals complex were measured in the frequency range between 4 and 24 GHz using a pulsed jet cavity Fourier transform microwave spectrometer. The isotopomers studied included those of NH₃, ¹⁵NH₃, ND₃, NHD₂, and NH₂D with the five most abundant isotopes of Kr. Tunnelling splittings due to the inversion of the ammonia subunit within the ground state of the complex were observed for all three deuterium containing isotopomers. In the NH₃ and ¹⁵NH₃ isotopomers, one of the tunnelling states has a spin statistical weight of zero and the splitting can therefore not be measured in these species. Nuclear quadrupole hyperfine structure arising from the ¹⁴N and ⁸³Kr nuclei was measured and the corresponding nuclear quadrupole coupling constants were determined. These were used to estimate structural parameters and derive information about the intermolecular dynamics. Smaller nuclear quadrupole splittings arising from the deuterium nuclei were observed but could not be resolved. The ground state spectroscopic constants were compared with experimental and theoretical data previously reported for Ar-NH₃ and its isotopomers. For the Kr-ND₃ isotopomers, additional transitions were observed and assigned to the two inversion components of an excited internal rotor state. A fit of the spectroscopic constants revealed the presence of a Coriolis perturbation, similar to that reported for this state in Ar-ND₃ and Ar-NH₃.     

On Some Families of Smooth Affine Spherical Varieties of Full Rank

Let G be a complex connected reductive group. Losev has shown that a smooth affine spherical G-variety X is uniquely determined by its weight monoid, which is the set of irreducible representations of G that occur in the coordinate ring of X. In this paper we use a combinatorial characterization of the weight monoids of smooth affine spherical varieties to classify:(a) all such varieties for G = SL(2) × C~×and(b) all such varieties for G simple which have a G-saturated weight monoid of full rank. We also use the characterization and Knop's classification theorem for multiplicity free Hamiltonian manifolds to give a new proof of Woodward's result that every reflective Delzant polytope is the moment polytope of such a manifold.     

BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES—VI. PHOTOOXIDATION OF L-TRYPTOPHAN BY SELECTIVELY SULFONATED GALLIUM PHTHALOCYANINES: SINGLET OXYGEN YIELDS AND EFFECT OF AGGREGATION

Abstract— The photosensitized oxidation of L-tryptophan by gallium phthalocyanines sulfonated to different degrees is studied as a function of both substrate and sensitizer concentrations in water and 50% MeOH-H₂O solutions. The maximum quantum yield of singlet oxygen was found to be nearly 0.5 for all sulfonated gallium complexes. The effect of adding sulfonate groups in the phthalocyanine backbone is to change the tendency of dye molecules to dimerize or aggregate in a particular solvent. A shift in the chemical equilibrium away from the monomeric state, which occurs at high dye concentrations and at lower degrees of dye sulfonation, results in a reduced photochemical yield. The variation of quantum yields in different solvent systems and at several wavelengths is similarly accounted for by the fraction of light absorbed by the productive monomer state.     

INVESTIGATIONS ON VINYLENE CARBONATE Ⅰ. PREPARATION AND PROPERTIES OF POLY-(VINYLENEC ARBONATE)

Bulk polymerization of vinylene carbonate using t-butylperoxypivalate at 40℃gave colourless, high molecular weight poly(vinylene carbonate) (PVCA). Solutions of PVCA in acetone and DMF are not stable at 25℃and this degradation was studied. From measurements in DMF with unfractionated PVCA a Mark-Houwink equation was obtained:     

LIGHT DOSIMETRY FOR PHOTODYNAMIC THERAPY BY WHOLE BLADDER WALL IRRADIATION

Abstract In Photodynamic Therapy (PDT) there is a need for accurate quantitative light dosimetry. This has become particularly apparent in the treatment of superficial bladder cancer, either by focal or by whole bladder wall irradiation. We have studied this problem using a spherical model of the bladder, consisting of two concentric thin-walled plastic spheres, 8 and 10 cm in diameter. The inner sphere was filled with water or with a light-scattering medium. The space between the spheres was filled with an optically tissue equivalent liquid. An isotropic light source was placed at the center of the spheres. Light energy fluence rates (light "dose rates") during PDT of the bladder simulated in this manner, were measured using a specially developed miniature light detector and were also calculated using a mathematical model. These data were confirmed by measurements in vivo (dog bladder). In the case of focal irradiation at a wavelength of 630 nm, the ratio (R) between the true light fluence rate at the bladder surface and the fluence rate due to the primary light beam is somewhat larger than 1, depending on the diameter of the primary beam. The maximum ratio is 2, for a beam diameter of several centimeters. In the case of whole bladder wall PDT, R is larger than 5. This is due to the strong scattering of (red) light by tissue and indicates that the intensity of the primary beam, which is usually reported, is not a good measure of the true fluence rate for whole bladder wall PDT. When the light source is moved away from the center of the spheres, the rate of change of the fluence rate at the bladder wall is more than a factor of 2 larger when the bladder cavity is filled with a light-scattering suspension, as compared with water. The use of a light-scattering medium may therefore not be advantageous to achieve a uniform light distribution across the bladder wall.     

SULFONATED PHTHALIMIDOMETHYL ALUMINUM PHTHALOCYANINE: THE EFFECT OF HYDROPHOBIC SUBSTITUENTS ON THE in vitro PHOTOTOXICITY OF PHTHALOCYANINES

The photocytotoxicity of sulfonated phthalimidomethyl aluminum phthalocyanine, a more hydrophobic photosensitizer as compared to phthalocyanine substituted with sulfonate groups only, was investigated. Inclusion of 1-2 phthalimidomethyl groups into disulfonated aluminum phthalocyanine, resulted in increased partition coefficients between n-octanol and water, and a six-fold increase in both cellular uptake and photocytotoxicity towards Chinese hamster lung fibroblast cells (line V-79). Reducing the number of phthalimidomethyl groups, or increasing the degree of sulfonation, lead to a decrease in the partition coefficient, cellular uptake, and phototoxicity. The quantum yield of singlet oxygen was comparable for all dyes tested in this series, indicating that no significant change in this photophysical parameter resulted from phthalimidomethylation. These results suggest that the addition of 1-2 phthalimidomethyl groups to disulfonated aluminum phthalocyanine improves cellular uptake, but, as the relative efficiency of cell killing was not effected, the intracellular distribution on photosensitive molecules may not be modified.     

PHOTOSENSITIZATION OF SINGLE-STRAND BREAKS IN pBR322 DNA BY ROSE BENGAL

Rose bengal photosensitized the formation of frank single-strand breaks (SSBs) in double-stranded, supercoiled pBR322 DNA as measured by neutral agarose electrophoresis. The yield of SSBs followed first order kinetics with respect to light fluence and dye concentration. The efficiency of cleavage was more than 20 times greater in an argon atmosphere than in an oxygen atmosphere. The quantum yield in an air atmosphere was 1.7 (+/- 0.3) X 10(-8). Sodium azide quenched the cleavage more efficiently in an oxygen atmosphere than when the oxygen concentration was reduced. Isopropanol and mannitol were poor quenchers; ribose-5-phosphate and guanosine-5'-monophosphate did not quench the cleavage. Substituting D2O for H2O increased the yield of SSBs in both oxygen and oxygen-depleted atmospheres. The results are consistent with initiation of cleavage by reaction of the triplet state of rose bengal (or a radical derived from it) with DNA. In the presence of oxygen, an additional mechanism is introduced.     

THE U.V. PHOTOLYSIS (Λ= 185nm) OF ETHYLENE GLYCOL IN AQUEOUS SOLUTION*

Abstract— –The u.v. photolysis (Λ= 185 nm) of 2 M aqueous solutions of ethylene glycol was studied at 22°C. Products (quantum yields) are hydrogen (0.20₄) formaldehyde (0.19₄), glycolaldehyde (0.08), methanol (0.07₄), glycerol (0.06), erythritol (0.03), acetaldehyde (0.02), 3,4-dihydroxybutanal (0.01) and succinaldehyde (0.001). With increasing temperature the yields of all products remain essentially unchanged except that of acetaldehyde (φ= 0.32 at 90°C) which is formed in a chain reaction. The photolysis of (CD₂OH)₂ yields 91% HD, indicating that the most important primary process is the homolytic splitting of the O-H bond. The resulting oxy radicals fragmentate largely into formaldehyde and CH₂OH radicals. Molecular fragmentation processes yielding hydrogen and glycolaldehyde, as well as formaldehyde and methanol, are discussed in the proposed decomposition scheme.