Structural and property changes in poly (vinylidene fluoride–trifluoroethylene) 70/30 mol % copolymer induced by proton irradiation

Poly(vinylidene fluoride–trifluoroethylene) 70/30 mol% copolymer has been irradiated with 3 MeV protons at doses ranging from 43 to 200 Mrad. The effects of irradiation on the polarization hysteresis, dielectric properties, lattice spacing, phase transition behavior and electric-field-induced strain have been studied. The irradiated copolymer exhibits the characteristic behavior of a relaxor ferroelectric, including frequency dispersion of the dielectric constant, which follows the Vogel–Fulcher rule. These results indicate that the proton irradiation breaks up the coherent polarization domains in the copolymer into nano-sized regions, thereby converting the copolymer to a relaxor ferroelectric. X-ray diffraction measurements show that the nano-sized regions are in the non-polar phase. Since the lattice spacing of the non-polar phase is substantially different from that of the polar phase, the local phase transformation between these two phases induced by an external electric field gives rise to a large lattice strain and hence a giant electrostrictive response. PACS 77     

Investigation of the effects of wall adsorption of the visualization agent on baseline noise characteristics for indirect UV detection in capillary electrophoresis

New insights into the effects of the wall adsorption of the visualization agent on baseline noise characteristics in indirect UV detection in capillary electrophoresis were provided. When compared to relatively small, hydrophilic cationic (1-(4-pyridyl)pyridinium chloride hydrochloride) or anionic chromophores (bromide and benzoate), the use of a UV-absorbing long-chain cationic surfactant (benzyldimethylhexadecylammonium chloride) as a probe (visualization agent) for studying baseline noise characteristics as a function of various experimental conditions, such as applied voltage, pH or buffer composition, was found to provide noise data that were very different under certain conditions. For cationic visualization agents that have a strong tendency of adsorbing onto the capillary surfaces due to electrostatic and/or hydrophobic interactions, it appeared that the interplay of both thermal as well as adsorption/desorption events occurring within the capillary is likely responsible for a fluctuation of the visualization agent concentration at the detector.     

Influence des Liaisons Chimiques sur la Transition Spin Faible → Spin Fort du Cobalt(III) (3d6) au sein D′Oxydes de Type K2NiF4

Influence of the Chemical Bonding on the Low Spin → High Spin Transition of Cobalt(III) in Oxides of the K₂NiF₄ Type It appears from a wide investigation of the LS → HS transition of cobalt(III) based on a Slichter and Drickamer model that in an oxide lattice with K₂NiF₄-type structure, the influence of the cation size in C.N.9 sites is prevailing on that resulting from the competing bonds in the pervoskite-type layers.     

Negative thermal expansion in oriented crystalline polymers

Measurements on the thermal expansivity α_∥ and α_? (along and normal to the draw direction, respectively) have been carried out for a series of oriented polymers with widely different crystallinities (0.36–0.81) and draw ratios (1–20) and over large temperature ranges covering the major amorphous transitions in each case. While α_? increases with temperature, α_∥ tends to decrease sharply above the transition temperature. For highly crystalline polymers, α_∥ decreases to values typical of polymer crystals (?1 × 10^?5 K^?1) and this can be attributed to the constraining effect of the crystalline bridges connecting the crystalline blocks. However, for polymers of lower crystallinity, α_∥ may become an order of magnitude more negative and this remarkable phenomenon is attributed to the rubber–elastic contraction of taut tie-moleucles. Since taut tie-molecules and bridges have drastically different effects on α_∥ at high temperatures, this allows a rough determination of their relative fractions.     

Integrated bio-inorganic hybrid systems for nano-forensics

This tutorial review describes a new class of data processing system that applies information theory at the molecular level. We also summarize the recent multidisciplinary advances in biotechnology and nanotechnology that have facilitated the development of reliable nano-level code systems. After a brief introduction of information theory, we present possible ways to adapt this concept to the molecular world. This review explains the requirements and solutions for each step necessary to apply a nano code system to real products. Finally, we introduce a designed nano code system for agricultural products as one example of the many possible applications for nano codes.     

Evaluation of Lighting Systems,Carbon Sources,and Bacteria Cultures on Photofermentative Hydrogen Production

Fluorescent and incandescent lighting systems were applied for batch photofermentative hydrogen production by four purple non-sulfur photosynthetic bacteria (PNSB). The hydrogen production efficiency of Rhodopseudomonas palustris, Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodospirillum rubrum was evaluated using different carbon sources (acetate, butyrate, lactate, and malate). Incandescent light was found to be more effective for bacteria cell growth and hydrogen production. It was observed that PNSB followed substrate selection criteria for hydrogen production. Only R. palustris was able to produce hydrogen using most carbon sources. Cell density was almost constant, but cell growth rate and hydrogen production were significantly varied under the different lighting systems. The kinetics study suggested that initial substrate concentration had a positive correlation with lag phase duration. Among the PNSB, R. palustris grew faster and had higher hydrogen yields of 1.58, 4.92, and 2.57 mol H₂/mol using acetate, butyrate, and lactate, respectively. In the integrative approach with dark fermentation effluents rich in organic acids, R. palustris should be enriched in the phototrophic microbial consortium of the continuous hydrogen production system.     

Quantitative determination of glucose in blood plasma by homonuclear proton decoupled water attenuation transverse relaxation Carr-Purcell-Meiboom-Gill (WATR-HDCPMG) NMR spectroscopy

Glucose in 5% D₂O/95% H₂O solution was successfully determined quantitatively by measurements of the ¹H NMR peak height (intensity) of the single peaks at δ(¹H) = 5.22 and 4.64 ppm corresponding to the α-D and the β-D-glucose spectrum, respectively. The single peaks were obtained from decoupling of the high field part of the AX spectrum of the α-D- or the β-D-glucose by incorporation of time shared homonuclear decoupling in the WATR-CPMG method (WATR-HDCPMG) without re-attenuation of the water peak. The method was applied to the determination of total glucose in blood plasma from human subjects undergoing oral glucose tolerance test (OGTT) in the teaching hospital. The results compared favorably with those obtained from the standard glucose oxidase method obtained in a hospital pathology laboratory. The accuracy of the results obtained using the WATR-HDCPMG method was within 3.5% of the glucose oxidation method. Received: 5 January 1998 / Revised: 23 February 1998 / Accepted: 26 February 1998