Separation axioms in fuzzy topological spaces

This paper provides a hierarchy of separation properties for fuzzy topological spaces which are generalizations of the standard topological notions.     

Quenching of giant hysteresis effects in La(1-z)Y(z)Hx switchable mirrors

Hydrogen atoms adsorbed on TiO2(110)-(1x1) surfaces have been characterized by scanning tunneling microscopy (STM) combined with electron stimulated desorption (ESD) technique. Certain amounts of H atoms are unexpectedly found on the TiO2 surfaces annealed at 900 K. Two forms of adsorption were discriminated in STM images from the different sensitivity to ESD and tentatively assigned to hydroxyl-type (O-H) and hydride-type (Ti-H) species.     

The infrared spectra (500-150 CM−1) of the complexes cis- and trans-[Pt(pyridine)2X2] (X = Cl,Br, I,SCN)

The IR spectra of cis- and trans-[Pt(pyridine)₂X₂] (X = Cl, Br, I, SCN) are discussed. Distinction between the vPt—N and vPt—X bands is based on their relative sensitivities to ¹⁵N-labelling and deuteration of the pyridine ring, to halogen substitution and to ¹⁵NCS-labelling. Two vPt—N and two vPt—X bands are observed in the cis-complexes as required for C_2v symmetry. The D_2h symmetry of the trans-complexes requires one vPt-N and one vPt—X band but additional bands are observed and are ascribed to coupling between vPt—N and vPt—X.     

Synthesis of beta-hydroxy-beta-(fluoronitrophenyl)alanines: vital components in the assembly of biologically active cyclic peptides

[formula: see text] Numerous biologically active cyclic peptides, such as the antibiotic vancomycin, contain amino acid residues connected through side-chain biaryl or aryl-alkyl ether linkages. Nucleophilic aromatic substitution reactions have recently been shown to provide a general method for the formation of such ether linkages, and consequently the synthesis of functionalized fluoronitro-substituted aromatic amino acids is of great interest. Herein, a method for the stereospecific synthesis of 3-fluoro-4-nitro- and 4-fluoro-3-nitro-threo-beta-hydroxyphenylalanine is described.     

Anomalous amorphous SiO2 films

Anomalous SiO₂ films have been prepared by sputtering Si in a mixture of Ar-10% O₂ at 77 K. The same sputtering conditions at room temperature yield normal SiO₂ which means that the anomaly is produced by the low temperature deposition. The anomaly reveals itself in several physical properties. The density of the anomalous SiO₂ is 1.72 as compared with 2.20 for bulk and the dielectric constant is about 50% larger than bulk and with a much stronger temperature dependence. The infrared (ir) spectrum of the anomalous SiO₂ is only slightly different from bulk SiO₂ but esr experiments reveal about 3 × 10¹⁸ spins cm which do not exist in bulk SiO₂. These anomalous films are extremely stable: upon heating only a small amount of oxygen (1 part in 10⁵) evolves at 440°C but the density and IR spectrum remain unchanged up to 1300°C. Annealing at 1500°C completely removes the ESR signal and returns the ir spectrum and the density to that of cristobalite. An electron diffraction and transmission electron microscopy study reveals that the anomalous SiO₂ films consist of essentially bulk like SiO₂ clusters about 250 Å in diameter separated by a low density network. The low density network undoubtedly contains unbound O atoms and the SiSi bonds which give rise to the esr signal. The structural model can account for all the anomalous properties.     

Validation of bismuth film electrode for determination of cobalt and cadmium in soil extracts using ICP-MS

A study is presented on the use of the bismuth film electrode (BiFE) operated in the anodic stripping and the cathodic adsorptive stripping voltammetry (ASV, CAdSV) modes, for the determination of two trace heavy metals (Cd and Co, respectively), in soil extract samples. Two types of BiFE were examined in this study: the in situ prepared BiFE, which was employed in ASV determination of Cd, and the ex situ prepared BiFE, which was used in CAdSV of Co with dimethylglyoxime (DMG) as complexing agent. A series of unpretreated soil extracts with varying Cd and Co concentrations were analyzed, and the results obtained compared to those determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed the suitability of stripping analysis at the BiFE for determination of μg l⁻¹ levels of heavy metals in soil extracts. The promising results obtained here, coupled with the non-toxic nature of bismuth (in comparison to commonly used mercury electrodes employed in stripping analysis), offer great promise in centralized and decentralized analysis of trace heavy metals in complex environmental matrices.     

Intercombination decay of 3s3p 3 P 1 0 in MgI-like Ni and Cu

The intercombination transition 3s^{2 1}S₀ ?3s3p³P ₁ ⁰ in Ni¹⁶⁺ and Cu¹⁷⁺ has been studied by beam-foil spectroscopic methods. Decay curve analysis yields lifetime values of (12.0±1.0)ns and (8.8±0.6)ns for Ni and Cu in agreement with various predictions.     

A possible mechanism to explain the synergistic effects exhibited by mixtures of alkyltin mercaptoesters as stabilisers for PVC

The phenomenon of synergism observed with mixtures of mono- and dialkyltin stabilisers for PVC has been recognised and exploited for many years, but remains largely unexplained. Whilst a similar effect in mixed metal (Ba/Cd or Ca/Zn) carboxylate stabilisers has been explained, mechanistic studies of the organotin systems have not appeared. Infra-red spectroscopy has now been used to study the Cl/mercaptoester exchange equilibria of alkyltin mercaptoester (isooctylthioglycollate) chlorine compounds which are undoubtedly produced when the organotin mercaptoesters act as PVC stabilisers. The exchange process is shown to be facile, even at ambient temperatures, and a regenerative mechanism, based on these observations, is proposed to explain the synergistic effect.     

Preliminary study of metals in proteins by high-performance liquid chromatography-inductively coupled plasma mass spectrometry using multi-element time-resolved analysis.

The feasibility of multi-element and multi-isotope determinations during the on-line chromatographic separation of protein matrices was investigated using time-resolved software with inductively coupled plasma mass spectrometry. Size-exclusion chromatography was used to separate a mixture of known proteins and the behaviour of associated elements was monitored. It was possible to scan either the entire mass range or a selected number of isotopes. Reversed-phase chromatography was used to separate Zn-containing species in chicken meat that had been intrinsically and extrinsically labelled with stable isotopes of Zn. The ratio obtained for the intrinsic label agreed with that obtained by other workers using thermal ionization mass spectrometry. Time-resolved analysis permitted rapid data acquisition, thus reducing the number of chromatographic runs required. However, at present, data handling can be time consuming. Further software developments will add to the advantages that this technique offers.