Fuzzy sets do not form a topos

The relationship between fuzzy sets and H-valued sets is briefly examined and a claim of Eytan's that the former comprise the objects of a topos is corrected.     

Chemiluminescent emissions from the gas phase reactions of ozone with acetylene and allene

Chemiluminescence spectra (300–800 nm) from the reactions of ozone with acetylene and allene have been obtained. These spectra show the production of electronically excited CHO, OH(²Π_i, υ ? 9) and possibly C₂(B³Π_g, υ′ = 0 → X³Π_u, υ″ = 6) from the O₃ + C₂H₂ reaction. CH(²Δ), OH(²Σ⁺) and OH(²Π_j, υ ? 9) emissions were identified from the O₃ + C₃H₄ reaction in addition to the CH₂O(¹A″) emission previously reported.     

X-ray CT microtomography and mechanical response of foamed polysiloxane elastomers

3D X-ray computer microtomography (CT) experiments have been performed to assess the microstructure of scaled cellular polysiloxane elastomers and to predict how key morphological features alter as a function of compressive loading. In the work reported here, full scale (nominally 600 μm pore size) and half scale (nominally 300 μm pore size) polydimethylsiloxane foams (M97) were prepared using extractable urea particles, and tested. CT test methodology was developed to image foam microstructure at different levels of compression. 1D magnetic resonance imaging (MRI) experiments have also been performed on full scale foams for baseline characterisation. Material porosity, bulk density and dynamic mechanical analysis (DMA) stress/strain responses as a function of compression were recorded. Our results show that undesirable engineering stress responses are evident when the material microstructure (cell size and shape) is non-uniform and complex. This is particularly evident when non-spherical urea particles are used, leading to undesirable scaled foam microstructures with mechanical responses that do not match that shown by ‘full scale’ versions. Through the use of X-ray CT and MRI, our studies have provided insights into the link between manufacturing, polymer architecture (cell size/shape) and mechanical response of scaled M97 cellular materials. The data collected will support materials FEA (finite element model) code development activities, as well as help identify how the material architecture can be modified to achieve more controlled and uniform mechanical responses.     

A simple and rapid hydride generation—atomic absorption method for the determination of arsenic in biological,environmental and geological samples

An inexpensive 50-ml disposable (hypodermic) syringe is used as the arsine generation vessel. The arsine is passed into a 10-cm long. 10-mm i.d. electrically heated silica tube atomizer with nitrogen carrier gas. Excess of hydrogen is burned off in a hydrogen diffusion flame at the ends of the tube. Samples containing appreciable silica are fused with KOH—MgO_XXX while organic samples are digested with H₂SO₄—H₂O₂. Parameters affecting the determination of arsenic as arsine have been investigated. Collaborative results on a variety of standard reference materials agree well with literature values. The advantages of the proposed method are that it is sensitive, selective, fast, simple, inexpensive, precise and accurate.     

Distortion and orientation for triplet coronene in different n-heptane shpol'skii sites using polarized microwave midp technique

Using phosphorescence microwave double resonance techniques, the type of distortion and the orientation of the magnetic axes are determined for triplet coronene molecules in different Shpol'skii sites in n-heptane single crystals at 1.6 K. Coronene triplet molecules in different sites are found to differ one from another not only in orientation but also in the degree and the sense (quinoidal versus antiquinoidal) of the distortion of the hexagonal coronene structure.     

A modified approach to 2-(N-aryl)-1,3-oxazoles: application to the synthesis of the IMPDH inhibitor BMS-337197 and analogues

[structure: see text] A modified approach to the synthesis of 2-(N-aryl)-1,3-oxazoles, employing an optimized iminophosphorane/heterocumulene-mediated methodology, and its application to the synthesis of BMS-337197, a potent inhibitor of IMPDH, are described.     

In vivo sodium-23 magnetic resonance surface coil imaging: Observing experimental cerebral ischemia in the rat

Sodium-23 magnetic resonance imaging can be used to detect and assess experimental cerebral ischemia in the rat. An imaging technique utilizing a surface coil is described to produce sodium magnetic resonance images of good quality and resolution within 10 min. A novel method of hemispheric occlusion showed edema in the right brain of the rat head within 3 hr after injury. The edema was especially pronounced by 12 hr with effects in the right brain, eye and surrounding muscle evident.     

Rate constants for the reaction of (sP) atoms with SO2 (M = N2O) over the temperature range 299–392 K

Third order rate constants have been determined for the reaction O + SO₂ + N₂O → SO₃ + N₂O over the temperature range 299–392 K using a modulation technique. The Arrhenius expression obtained is k₂^N₂O = 3.32 × 10¹⁰ exp[?(2000±400)/RT] liter² mole^?2 s^?1. This temperature dependence is in good agreement with recent flash photolysis-resonance fluorescence measurements using N₂ as a third body.