Studies on Phosphorus-Containing Polymers. VI. Synthesis of Derivatives of Linear Phosphonitrile Chloride and Their Stability

The synthesis of LPNC and its derivatives and the hydrolysis and heat resistance properties of these materials are discussed. Lack of stability to water and depolymerization are adverse properties of many inorganic polymers. In the case of LPNC, it was found that these properties were probably due to the terminal ionic structure, and when the ionic part is removed from LPNC, the properties could be somewhat improved.     

FTIR-ATR evaluation of organic contaminant cleaning methods for SiO2 surfaces.

The effectiveness of cleaning organic contaminants from silicon dioxide (SiO2) surfaces was studied by conducting highly sensitive measurements using Fourier Transform Infrared Attenuated Total reflectance (FTIR-ATR) with a Si prism as the waveguide. To serve as an example, the surface of the prism was oxidized to an order of a few nanometers. The oxidized Si surface film was allowed to stand in the atmosphere and then wet-cleaned in a repeated manner; subsequently its thickness was measured by ellipsometry. Although, various wet-cleaning methods were tested, they only showed values of 0.1-0.2 nm larger than, but not equal to, the original thickness immediately after oxidation. FTIR-ATR measurements of the spectral change after exposure to air revealed that organic species, such as C-CH3 and -(CH2)n-, increased with time. Wet-cleaning the sample failed to remove the C-CH3 species, which indicates that they corresponded to the film thickness increment from the original.     

Enzymatic screening of microalgae as a potential source of natural antioxidants

Extracts of over 100 species of microalgae both from nature and from laboratory cultures were screened for antioxidant activity. As an assay for antioxidant function, we examined the inhibition of the activity of two oxidizing enzymes, lipoxygenase and tyrosinase. Water, ethanol, and methanol extracts of microalgae were used for the assay. It was found that lipoxygenase and tyrosinase activities were inhibited by the extract of several microalgae. Our results suggest that these species of microalgae have useful antioxidant activity, and they will be further examined for potential biotechnological exploitation. The aim of our screening was to identify potential sources of natural antioxidant compounds, which if found to be sufficiently potent and nontoxic, might eventually replace the chemicals that are currently used as food additives and cosmetics, in order to prevent food spoilage and their oxidation.     

Compact amperometric algal biosensors for the evaluation of water toxicity

Unicellular microalga Chlorella vulgaris was entrapped in an alginate gel or a polyion complex membrane immobilized directly on the surface of a transparent indium tin oxide electrode. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine), 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU), toluene and benzene, were evaluated as inhibition ratios of the reduction current. The concentrations that give 50% inhibition of the oxygen reduction current (IC^′₅₀) for atrazine, DCMU, toluene and benzene were 2.0, 0.05, 1550 and 3000 μmol dm⁻³, respectively. There was a good correlation between these data and those of the conventional standard growth test. In comparison with the conventional algal biosensors based on the Clark-type oxygen electrode, the present sensor is much smaller and less expensive, and its assay time is much shorter (≤200 s).     

Orientational photorefractive effects observed in poly(vinyl alcohol)/liquid crystal composites

60 ) as a photoconductive sensitizer under an applied dc field. Orientational photorefractivity was demonstrated by observing Raman–Nath diffraction beams with an external dc field. The photorefractive gratings were partially memorized even in the absence of the applied dc field. Received: 12 January 1998/Revised version: 2 February 1998     

Complex formation of p-nitrocalix[6]arene with rare earth metal ions.

p-Nitrocalix[6]arene (CALX-N6, L) formed a 1:1 metal complex, ML, with light rare earth metal ions (M3+), such as La3+, Pr3+ and Nd3+ except Ce3+, but formed a 1:2 (M(3+):L) complex, ML2 (the charge of the complex is omitted) with heavy rare earth metal ions, such as Sm(3+)-Lu3+ including Y3+. The conditional stability constants of these 1:1 and 1:2 complexes, KML and KML2, were measured by a ligand displacement method using absorption spectrophotometry in 4% (v/v) acetone aqueous solution at pH 9.65 +/- 0.15 and 25 degrees C.     

Thermal behavior of Jonscher’s formalism in relaxor ferroelectrics showing diffuse phase transitions

A theoretical study of the thermal behavior of the exponent s of Jonscher’s power law in ferroelectric materials showing diffuse phase transitions (DPTs) is presented. The proposed model is applied to the experimental results of lanthanum-doped lead zirconate titanate ferroelectric ceramics. Both the proposed model and the experimental results show a critical point (a maximum) around the maximum of the dielectric loss factor, which moves to higher temperatures when the frequency increases, the typical behavior of a relaxor material with DPTs. PACS 77.22.Gm; 77.80.Bh; 77.84.Dy     

Two-dimensional correlation analysis useful for spectroscopy, chromatography, and other analytical measurements.

Application of generalized two-dimensional (2D) correlation in various analytical fields is explored. 2D correlation is a powerful and versatile technique applicable to spectroscopy, chromatography, and other measurements. Construction of 2D spectra is relatively straightforward, requiring only a series of systematically varying analytical signals, like spectra or chromatograms, induced by an external perturbation applied to the system of interest. Perturbation can take many different forms, like change in temperature, pressure or concentration, chemical reactions, electrical or mechanical stimuli, and so on. A set of analytical signals collected under a perturbation are then converted to 2D correlation spectra, which provide rich and useful information about the presence of coordinated or independent changes among signals, as well as relative directions and sequential order of signal intensity variations. The signal resolution is also enhanced by spreading overlapped bands along the second dimension. Illustrative examples of 2D correlation are given for spectroscopic and chromatographic applications.