Electronic transport and magnetic properties of the perovskites La0.8Sr0.2Co1−xFexO3; x ≤ 0.3

Transport and magnetic properties of LaCoO₃-based compounds, doped with 20% Sr and 2.5, 5, 10, 15, 20 and 30% Fe, were investigated by means of magnetization, resistivity and magnetoresistance measurements as well as by ⁵⁷Fe Mössbauer spectroscopy. While the temperature dependence of the dc and ac magnetic susceptibilities reveals the presence of magnetic phase separation accompanied by spin-glass and cluster-glass behavior, the electrical resistivity and magnetoresistance characteristics indicate that the mesoscopic structure of the present compounds is rather well described as consisting of ferromagnetic, metallic grains embedded in an insulating matrix. The effect of the partial Co → Fe substitution on the bulk magnetic and transport properties, as well as on the local state of Co and Fe ions is discussed.     

Multiphonon absorption in As2S3As2Se3 glasses

Multiphonon absorption in As₂S₃ and As₂Se₃ glasses is well explained by a molecular model in terms of combination bands of high frequency vibrational modes of pyramidal AsY₃ and bent AsYAs groups (Y = SorSe). Multiphonon absorption coefficients in mixed As₂S₃As₂Se₃ glasses are nearly additive in terms of the pure components, suggesting a high degree of non-random mixing.     

Novel routes to Cu(salicylaldimine) covalently bound to silica: combined pulse EPR and in situ attenuated total reflection-IR studies of the immobilization

Several novel routes for the immobilization of modified Cu(salicylaldimine) complexes on commercially available silica are described. New pulse electron paramagnetic resonance (EPR) and electron-nuclear double resonance sequences, which provide more detailed information than that available previously, in combination with continuous wave EPR, allow a definitive assignment of the geometry at the copper center in the immobilized Cu(salicylaldimine). Immobilization of the modified Cu(salicylaldimine) on silica was followed in situ by monitoring the intensity of the characteristic free- and metal-coordinated imine bands as a function of time using attenuated total reflectance IR spectroscopy. On the basis of these studies, the outcome of the Schiff base condensation of Cu-bis(salicylaldehyde) with gamma-aminopropyl-modified silica gel is shown to provide immobilized trans-O(2)N(2)- and O(3)N-coordinated immobilized Cu(salicylaldimine)-type compounds. In addition, trans-O(2)N(2)- or O(3)N-coordinated copper centers are selectively prepared on silica by controlling the aminopropyl modifier loading, thus opening a route to compounds not available by conventional synthesis. The O(3)N-coordinated Cu(salicylaldimine)-type compound on silica was investigated as a precursor for the synthesis of a tethered chiral Cu(salicylaldimine) via reaction of the coordinated carbonyl group with (R)-(+)-alpha-methylbenzylamine. Supported Cu(salicylaldimine) was also prepared via the immobilization of the appropriate silylethoxy-modified homogeneous precursor on silica gel. Precursors and silica-supported Cu(salicylaldimine) materials have been fully characterized. Comparisons are drawn with related Cu(salicylaldimine) immobilized in silica aerogels.     

Peptide conformational analysis using the TRIPOS force field

To explain observed electron transfer rates between the terminal aromatic moieties in the arylsubstituted alanine dimer 1 , a conformational analysis of the dipeptide was performed using a standard molecular mechanics force field. The resulting low-energy conformers could conveniently be grouped into two families with an average energy difference of ca. 2 kcal mol^?1 and populations of 64% and 30%, respectively. These results correlate well with the 78:22 ratio of the two experimentally distinguishable decay processes for the radical anion of 1 . © 1992 John Wiley & Sons, Inc.     

Phosphinoarsonium and diarsonium cations from chloride-abstraction-induced pnictogen coupling

The first salts of phosphinoarsonium, diarsonium, and phosphinodiarsonium ions are obtained from reaction mixtures of a chlorophosphine, a tertiary arsine, and a chloride-abstracting agent. The versatile synthetic approach has implications in the development of a wide variety of interpnictogen compounds.     

4‐Ethynyl‐1,2‐methylenedioxybenzene at 150 K

The title compound, C₉H₆O₂, contains two moderate C—H?O hydrogen bonds. That involving the terminal alkyne gives rise to chains along the b axis. The other hydrogen bond occurs over a centre of symmetry, leading to dimers. The combination of the two interactions gives rise to rings, each comprising six mol­ecules, which are part of infinite sheets in the bc plane.     

Sustainable nanotechnology decision support system: bridging risk management,sustainable innovation and risk governance

The significant uncertainties associated with the (eco)toxicological risks of engineered nanomaterials pose challenges to the development of nano-enabled products toward greatest possible societal benefit. This paper argues for the use of risk governance approaches to manage nanotechnology risks and sustainability, and considers the links between these concepts. Further, seven risk assessment and management criteria relevant to risk governance are defined: (a) life cycle thinking, (b) triple bottom line, (c) inclusion of stakeholders, (d) risk management, (e) benefit–risk assessment, (f) consideration of uncertainty, and (g) adaptive response. These criteria are used to compare five well-developed nanotechnology frameworks: International Risk Governance Council framework, Comprehensive Environmental Assessment, Streaming Life Cycle Risk Assessment, Certifiable Nanospecific Risk Management and Monitoring System and LICARA NanoSCAN. A Sustainable Nanotechnology Decision Support System (SUNDS) is proposed to better address current nanotechnology risk assessment and management needs, and makes. Stakeholder needs were solicited for further SUNDS enhancement through a stakeholder workshop that included representatives from regulatory, industry and insurance sectors. Workshop participants expressed the need for the wider adoption of sustainability assessment methods and tools for designing greener nanomaterials.     

Electrochemistry of dopamine at the polarised liquid|liquid interface facilitated by an homo-oxo-calix[3]arene ionophore

The homo-oxo-calix[3]arene-facilitated electrochemistry of dopamine at the polarised liquid|liquid interface is presented. Cyclic voltammetry indicated that the dopamine: homo-oxo-calix[3]arene complex formed at the interface between water and 1,2-dichloroethane had a 1:2 stoichiometry, which was confirmed by ¹H NMR titration. The electrochemically-determined association constants for the homo-oxo-calix[3]arene complexes with dopamine (log β 8.3), Na⁺ (8.0) and K⁺ (7.5) showed that the ionophore was more selective for dopamine over the two alkali metal cations than the dibenzo-18-crown-6 ionophore. Square wave voltammetry was employed for assessment of low concentration measurements, with a limit of detection of 3.8 μM dopamine achieved. These results show that oxo-calixarene-based ionophores are useful reagents for the detection of dopamine at the interface between two immiscible electrolyte solutions.